Recent advances of nanocarbon-inorganic hybrids in photocatalysis

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

17

Elim Albiter, Jos
e M. Barrera-Andrade, Elizabeth Rojas-Garcı´a, Miguel A. Valenzuela Catalysis and Materials Laboratory, ESIQIE-National Politecnic Institute, Zacatenco, M
exico

Chapter Outline 17.1 Nanocarbons and photocatalysis 17.2 TiO2–Nanocarbon 527

521

17.2.1 Fullerenes 528 17.2.2 Carbon nanotubes 532 17.2.3 Graphene 536

17.3 Oxide–Nanocarbon

539

17.3.1 Zinc oxide 539 17.3.2 Copper oxides 540 17.3.3 Tungsten oxide 542

17.4 Chalcogenide-Nanocarbon

542

17.4.1 Cadmium sulfide 542 17.4.2 Other sulfides 545

17.5 MOFs–Nanocarbon 548 17.6 Multicomponent–Nanocarbon 17.6.1 17.6.2 17.6.3 17.6.4

557

Metal oxide 1-NC-metal oxide 2 557 Metal oxide-NC-chalcogenide 557 Semiconductor-NC-metal 560 Semiconductor nanocarbon-MOFs multifunctional materials 561

17.7 Conclusion 571 References 572

17.1

Nanocarbons and photocatalysis

Carbon-based materials have been investigated and used since the second half of the last century as catalysts and tcatalytic supports in a wide variety of chemical reactions of industrial interest [1, 2]. Activated carbon, graphite, and carbon black are the ones that have been used most frequently, followed by, to a lesser extent, glassy carbon, pyrolytic carbon and polymer-derived carbon [3]. Several advantages of carbon-based materials have been reported and their success has been explained in heterogeneous Nanocarbon and its Composites. https://doi.org/10.1016/B978-0-08-102509-3.00017-1 © 2019 Elsevier Ltd. All rights reserved.

522

Nanocarbon and its Composites

catalytic reactions, among which the following can be listed: high chemical stability in acid or basic media, low corrosion capability, high thermal stability, hydrophobic character, easy recovery from the reaction mixture, and lower price [1, 4]. However, the discovery of the so-called nanocarbons such as fullerenes (1985), carbon nanotubes (1991), and graphene (2004) has generated a growing interest in the synthesis, characterization, and applications of these materials in new catalytic reactions; nanocarbons can be used in its pristine form or as hybrids with inorganic nanoparticles, polymers, and other materials [4–6]. The concept of nanocarbon (NC) is understood as the ability of carbon atoms to form, under specific conditions, bonds between them via the hybridization of their 2s-2p orbitals, which leads to the generation of sp, sp2, and sp3 hybrid orbitals [7]. These hybrid orbitals are the basis of their evolution toward graphene and diamond, depending on whether three or four bonds are formed with neighboring carbon atoms, respectively [8]. Fullerene (OD), carbon nanotubes (1D), and graphene (2D) are the leading representatives coming from a sp2-hybridization process and, derived from them, are carbon quantum dots, nanohorns, nanofibers, nanoribbons, nanocapsulates, and nanocages, among others [9]. Although the use of carbon materials began with heterogeneous catalysis in the 1970s, from their use in photocatalysis began incipiently in the 1990s, as shown in Fig. 17.1. However, note that an exponential increase in the number of articles is detected in both topics, mostly in the last 5 years. Semiconductor-based photocatalysis plays a significant role in the development of modern technologies, using unlimited solar energy, in topics related to air and water treatment, hydrogen production, self-cleaning surfaces, sterilization, organic synthesis, and the obtention of fuels from carbon dioxide, among others [10, 11]. The heterogeneous photocatalytic reactions are carried out in the presence of a solid (semiconductor), a source of irradiation (UV/vis light), and reactants in the gas or

Fig. 17.1 Number of publications on “carbon materials”/“catalysis”/“photocatalysis” in Scopus on January 2, 2018.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

523

Fig. 17.2 Most important photocatalytic mechanisms. (A) Water splitting, (B) degradation of pollutant, and (C) CO2 conversion. Based on Zhou P, Yu J, Jaroniec M. All-solid-state Z-scheme photocatalytic systems. Adv Mater 2014;26:4920–35. https://doi.org/10.1002/adma.201400288.

liquid phase. The photocatalytic process begins with the absorption of a photon with energy equal or higher than that of the semiconductor’s band gap, which leads to the generation of charge carriers (i.e., electron-hole pairs) [12]. A series of redox reactions can occur on the semiconductor surface if a suitable scavenger is available for trapping an electron or a hole, leading to some of the most important photocatalytic reactions such as water splitting, degradation of pollutants, and CO2 conversion, as shown in Fig. 17.2 [13]. From a thermodynamic point of view, to carry out any photocatalytic reaction, it is essential that the conduction band (CB) and the valence band (VB) levels of the semiconductor must be more negative or positive than the reduction and oxidation potentials of the corresponding substrates to be converted (Fig. 17.3). Note that in the case of water splitting (Fig. 17.3A), it is necessary to couple the water photooxidation in the VB with the proton photoreduction in the CB to obtain oxygen and hydrogen, respectively. In the case of degradation of pollutants (Fig. 17.3B), this reaction regularly proceeds via OH radicals, which can be generated by oxidation of the hydroxyl ions by holes in the VB or by oxygen reduction with electrons in the CB. This process should be carefully balanced, ensuring that a semiconductor with the capacity to perform both reactions simultaneously is used. Likewise, the CO2 photocatalytic reduction (Fig. 17.3C) requires the coupling of the water photooxidation reaction (VB), which supplies the source of protons and electrons that will be converted in the CB to form products such as CO, CH4, and CH3OH, among others. It is important to note that,

524 Nanocarbon and its Composites

Fig. 17.3 Oxidation and reduction potentials of the different species involved in (A) Water splitting, (B) degradation of pollutants, and (C) CO2 reduction. Based on Li X, Yu J, Wageh S, Al-Ghamdi AA, Xie J. Graphene in photocatalysis: a review. Small 2016;12:6640–96. https://doi.org/10.1002/smll. 201600382.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

525

associated with the thermodynamic aspects, the kinetic aspects are also fundamental to achieve an improved global photocatalytic efficiency [14]. The most important of all is the charge separation/transport kinetics, which can be considered as a controlling step of the global photocatalytic efficiency [14]. At this point, it is where the use of several kinds of heterojunctions (e.g., metal-semiconductor, semiconductor-semiconductor, nanocarbon-semiconductor) that inhibit the recombination of photogenerated charges is justified. Undoubtedly, TiO2 has been the most researched and used semiconductor in some commercial applications due to its high photoactivity and high stability in various reaction media. Also, it is not toxic and has a low cost. However, TiO2 and other semiconductors (e.g., ZnO, WO3, CuxO) have been investigated regarding their surface modification tending to increase their photoactivity, to improve the absorption of visible light, and to modify the reaction mechanism to control the products and intermediates [14]. Fig. 17.4 is an example of a series of surface modifications that have been investigated, mainly with TiO2. Therefore, the hybridization of semiconductors with nanocarbon has been a viable alternative to generate a synergy that leads to the development of new more active, selective, and stable photocatalytic systems. The above can be corroborated by the increase in the number of publications in photocatalytic systems using

Metal deposition

Heterogeneous composites

Pt, Pd, Au, Ag...

CdS, WO3, SnO2, SiO2, Al2O3...

Hybrids with nano-materials CNTs, fullerenes, graphenes, POMs, zeolites

Dye anchoring

TiO2 photocatalyst

Fluoride, phosphate, organic molecules, surfactants, polymers Surface adsorbates

Ru-complex, porphyrins, organic dye

Metal-ion Nonmetal-ion co-doping Doping

Fig. 17.4 Various modification methods of TiO2 photocatalyst. Reproduced with permission from Park H, Park Y, Kim W, Choi W. Surface modification of TiO2 photocatalyst for environmental applications. J Photochem Photobiol, C 2013;15:1–20. https://doi.org/10.1016/j.jphotochemrev.2012.10.001.

526

Nanocarbon and its Composites

Fig. 17.5 Number of publications in photocatalytic systems type nanocarbon-inorganic hybrids.

nanocarbon-inorganic hybrids, as shown in Fig. 17.5. It is worth noting that the use of graphene has had the most significant impact, due to the vertiginous increase in the number of publications from 2010 to the present. The pioneering studies concerning the coupling of photocatalysts with carbonaceous materials were carried out to take advantage of their high adsorption capacity. Consequently, a significant effort was made in research using activated carbon (AC) coupled with TiO2 in different ways: TiO2-loaded AC, powder mixtures of TiO2 with AC, carbon-doped TiO2, and carbon-coated TiO2 [15]. However, nanocarbon compounds showed superior physicochemical properties than AC, such as electric and thermal conductivity, mechanical strength and toughness, and thermal and chemical stability, leading to vigorous and thriving investigations on the synthesis, characterization, and applications of nanocarbon-inorganic hybrids. In this regard, many reports show a higher photocatalytic activity of nanocarbonsemiconductor hybrids compared with bare semiconductors. The improved activity is explained in summary form as follows: (i) nanocarbon can act as a photosensitizer providing additional electrons to the VB of a semiconductor, and (ii) the high conductivity of the nanocarbon allows the extraction and storage of photo-generated electrons [5, 14]. After all, a minimization of the charge-carrier recombination and the creation of an overstructure that favors mass and electron transfer as well as better adsorption of the reactants should also be taken into account. According to the literature, the photocatalytic degradation of pollutants has been the most-studied reaction employing nanocarbon hybridized with oxides and chalcogenides, compared with the photocatalytic water splitting and CO2 reduction. Hence, this chapter will be focused on the recent results and advances in the field of nanocarbon hybridized with the conventional semiconductors (e.g., TiO2, ZnO,

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

527

Fig. 17.6 Chapter structure.

CdS, etc.) and new materials such as MOFs and multicomponents, highlighting the most important aspects reached in recent years in the mentioned photocatalytic (PC) reactions (Fig. 17.6).

17.2

TiO2–Nanocarbon

To date, TiO2 is the most employed material in photocatalysis and shows an excellent potential to be the ideal photocatalyst for a wide range of applications, such as environmental remediation, organic synthesis, water splitting, and CO2 reduction. However, two of its main disadvantages are the poor utilization of the solar spectrum, derived from its large band gap energy, and the fast recombination rate of the photogenerated electron-hole pairs [16]. It has been reported that several nanocarbon materials, such as fullerene, graphene, and carbon nanotubes, improve the absorption of visible light of TiO2 [17–21]. This improvement has been attributed to the formation of chemical bonds between TiO2 and functionalized nanocarbons (TidOdC bonds, Fig. 17.7) [22]. Also, these carbonaceous materials can act as a pool for the photo-generated electrons [14], reducing the recombination rate of electron-hole pairs and improving the photocatalytic performance.

528

Nanocarbon and its Composites

Fig. 17.7 Ti—O—C bonds formed during the synthesis of TiO2–C60 nanohybrids. Based on Mu S, Long Y, Kang S-Z, Mu J. Surface modification of TiO2 nanoparticles with a C60 derivative and enhanced photocatalytic activity for the reduction of aqueous Cr(VI) ions. Catal Commun 2010;11:741–4. https://doi.org/10.1016/j.catcom.2010.02.006.

17.2.1 Fullerenes Fullerenes are well known due to their remarkable physical and chemical properties resulting from their delocalized conjugated structure. Due to their unique electronic structures, C60 and C70 are excellent electron acceptors, making them promising materials to enhance the separation of photo-generated charge carriers in TiO2-based catalysts [16]. Additionally, fullerenes strongly absorb UV light and moderately absorb light in the visible region; thus, they can act as a photosensitizer, donating electrons to a coupled semiconductor. These two characteristics can be further enhanced by the functionalization of fullerenes, derived from the formation of chemical bonds, as mentioned earlier. The observed enhancement in the photocatalytic process has been explained previously in the literature [19, 23]. Briefly, after UV or visible light irradiation, fullerenes are excited from their ground state to a singlet excited state, which then decays to an excited triplet state with a more extended lifetime [24]. It is interesting to note that the excitation of fullerenes improves their capability of accepting or transferring electrons, including up to six electrons [25]. Due to the one-electron reduction potential of fullerenes or their excited states, the photo-generated electrons located in the conduction band of TiO2 could be transferred to these species, producing radical anions. Then, these anions could react with adsorbed species on the catalyst surface. On the other hand, fullerenes may also behave as electron donors, depending on the experimental conditions [26]; this behavior is primarily observed when fullerenes are irradiated with visible light [27–29]. Consequently, it is common to find in the literature that fullerenes can act as electron acceptors, enhancing the photocatalytic performance of the hybrid material due to the reduction of the electron-hole recombination or as an electron donor, enhancing the photocatalytic activity through TiO2 sensitization. These two mechanisms are depicted in Fig. 17.8. Because of their unique behavior when irradiated with UV or visible light, fullerenes have been employed in photochemistry as photosensitizers to produce singlet oxygen, in artificial photosynthesis, and in photochemical solar cells. In recent years, their application, in combination with TiO2, to photocatalytic reactions has been explored. However, the published studies are scarce when compared to other nanocarbons, and there are few reviews that have covered the application of C60

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

529

Fig. 17.8 Photoreaction mechanism of the C70-TiO2 hybrid under UV light (A) and visible light irradiation (B). Reproduced with permission from Wang S, Liu C, Dai K, Cai P, Chen H, Yang C, et al. Fullerene C70–TiO2 hybrids with enhanced photocatalytic activity under visible light irradiation. J Mater Chem A 2015;3:21090–8. https://doi.org/10.1039/C5TA03229F.

fullerene to TiO2 photocatalysis [17, 18]. More recently, C70 fullerene has also been hybridized with semiconductors; however, it is even less studied than C60. A selection of the most representative works regarding the application of fullerenes in TiO2 photocatalysis is presented in Table 17.1. As shown in Table 17.1, fullerenes are not commonly used in the pristine form, but they are functionalized by the introduction of different functional groups. For example, carboxylic groups are introduced into the fullerene structure using mild oxidation with inorganic acids [22, 27] or using organic reactions of cycloaddition [29, 30]. Also, the inclusion of hydroxyl groups has been explored, leading to obtaining the so-called fullerols [31, 32]. As mentioned earlier, the introduction of functional groups accomplishes a better interaction between the fullerene and TiO2, improving the electronic transfer but also improving the solubility in water of these nanocarbons. As a result of the physical and chemical interactions between TiO2 and fullerenes, some of the photophysical properties of the photocatalyst are modified, compared to pure TiO2. For example, Qi et al. found that the band gap energy of C60-TiO2 composites was reduced when the fullerene mass was increased [20]. The authors found a reduction of 0.15 eV when the content of C60 was 4 wt%; it is worthy to note that most published works did not report a modification of the band gap energy [21, 28–30]. However, all authors reported an increased absorption of visible light. The addition of fullerenes also may reduce the photoluminescence (PL) of TiO2-based materials. Cho et al. found that C70 can reduce remarkably the PL of C70-TiO2 composites compared to unmodified TiO2 [29]. The reduction of the PL signal can be attributed to the reduction of the recombination rate of electron-hole pairs, which can lead to an increased photocatalytic performance. The nanocarbon content seems to play an essential role in the photocatalytic activity of fullerene-TiO2 composites. According to the literature, the used content of fullerenes is in the range of 0.1 and 24 wt%, but the highest enhancement in the photocatalytic activity is observed between these values. For example, Qi et al.

530

Table 17.1 Selected publications on the photocatalytic applications of Fullerene-TiO2 hybrids Fullerene C60

Application

Reaction conditions

Commercial C60 Sol-Gel method

Methylene blue degradation

8 W mercury lamp Ccat ¼ 0.4 g L1 NC content ¼ 0.4–4 wt% [C]0 ¼ 5 mg L1

Oxidized commercial C60 Hydrothermal method

Acetone degradation in gas phase

15 W UV lamp Reactor volume ¼ 15 L Catalyst mass ¼ 0.3 g NC content ¼ 0.1–1.5 wt% [Acetone]0 ¼ 400 mg L1

Functionalized commercial C60 Commercial TiO2

Rhodamine B degradation

500 W Xe lamp with a UV cutoff filter (λ >400 nm) Ccat ¼ 1 g L1 NC content ¼ 0.5–3 wt% [C]0 ¼ 10 mg L1

Highlighted properties and results Reduced band gap, depending on C60 content, was observed. TiO2 was coated by C60, and the formation of a heterojunction was observed by HRTEM. The best PC performance was observed with 2 .0 wt% of C60. No modification of BG was observed. The PC performance was increased by the presence of oxidized C60. The catalyst with 0.5 wt% of C60 showed the best activity. The composites presented an enhanced absorption of visible light and they were active under visible light irradiation. The presence of C60 improved the adsorption of RB. The best PC performance was obtained with 1 wt% content of fullerene.

Ref. [20]

[21]

[30] Nanocarbon and its Composites

Preparation method NC/TiO2

Diphenhydramine degradation

Hg lamp with a cutoff filter (λ> 430 nm) Ccat ¼ 1 g L1 NC content ¼ 4 and 12 wt% [C]0 ¼ 100 mg L1 18 W UV lamp Ccat ¼ 0.13 g L1 TiO2 content ¼ 3 and 7.5 wt% [C]0 ¼ 13 mg L1

Functionalized commercial C60 Atomic layer deposition

Methyl orange degradation

Functionalized commercial C70 Hydrothermal method

Methylene blue degradation

Experimental conditions were not provided.

Oxidized commercial C70 Hydrothermal method

Sulfathiazole degradation

300 W Xe lamp with a cutoff filter (λ> 420 nm) Ccat ¼ 1 g L1 NC content ¼ 3–24 wt% [C]0 ¼ 10 g L1

The composite with 12 wt% of NC presented the best PC activity when irradiated with visible or UV light.

[28]

Fullerene was covered with thin layer of amorphous TiO2. The composites were active despite the low content of amorphous TiO2. The PL signal of the composites decreased compared to pure TiO2. The composites were active under visible-light irradiation. Chemical bonding between C70 and TiO2 was evidenced by XPS, FTIR, and Raman spectroscopies. Under UV-light irradiation, the contribution of C70 to the PC activity was negligible, but under visible light, the composite with 18 wt% of C70 showed the best activity.

[31]

[29]

[22]

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

C70

Oxidized commercial C60 Liquid phase deposition method

531

532

Nanocarbon and its Composites

prepared C60-TiO2 hybrids with an NC content of 0.4–4 wt%, and they found the highest activity with a carbon content of 2 wt%. The authors demonstrated, by using DFT calculations, that the interaction between fullerene and TiO2 through the formation of covalent bonds is a key point to enhancing the whole photocatalytic process. Thus, when NC content is increased above a certain threshold, fullerene can form aggregates and clusters on the semiconductor’s surface, increasing the coverage of the surface and the thickness of the fullerene layer [20]. The increased thickness could lead to a reduced NC-TiO2 interaction, and therefore fewer chemical bonds are formed. On the other hand, the increased coverage and the higher thickness inhibit the light absorption on the surface of TiO2. Nevertheless, it is not possible to determine the optimal nanocarbon loading by just comparing the reported results in the literature because this value seems to depend on the experimental conditions or preparation methods used. The fullerene-TiO2 hybrids have been employed in the photocatalytic degradation of water pollutants such as organic dyes, including methylene blue [20], rhodamine B [30], and methyl orange [31]; in the degradation of organic compounds in the gas phase [21, 33]; in the degradation of some emerging pollutants such as diphenhydramine [28] and sulfathiazole [22]; and in the selective oxidation of organic compounds [34]

17.2.2 Carbon nanotubes Carbon nanotubes (CNT) can be classified according to the number of carbon layers in their structure: single-walled nanotubes (SWCNTs), which have one layer of carbon atoms forming a cylinder; and multiwalled carbon nanotubes (MWCNTs), which consist of multiple concentric carbon sheets. Due to their cylindrical morphology, often referred to as a 1D structure [17], CNTs show interesting thermal and electronic properties that make them a promising material with applications in photocatalysis [16]. For example, CNTs can behave as either semiconducting or metallic materials, depending on their morphology; they also have excellent electron conductance [35]. Because of these electrical properties, CNTs can increase the lifetime of the photo-generated charge carriers due to the electron transfer from the CB of TiO2 to the carbon structure, which acts as an efficient electron sink. CNTs can also improve the photocatalytic performance of the TiO2 photocatalyst by providing an increased surface area (200 to 400 m2 g1) [36] and, therefore, more active sites. Also, these nanocarbons can improve the absorption of visible light of TiO2 [17] by modification of its band gap or by sensitization, similar to fullerene enhancement. The described improvements can be influenced by the preparation methods used for the CNTTiO2 hybrids. The reported methods provide reasonable control of the morphology and structure of these materials [37, 38]. For example, Fig. 17.9 shows three common structures of CNT-TiO2 hybrids. The first one (Fig. 17.9A) is composed of nanoparticulate TiO2 and CNT, which is commonly obtained by mechanical mixing. Fig. 17.9B shows TiO2 nanoparticles grown on the CNT surface by a wet chemical route and Fig. 17.9C shows large semiconductor particles wrapped by CNT. It is important

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

533

Fig. 17.9 CNT-TiO2 hybrids structures: (A) A hybrid made up of a random mixture of nanoparticulate TiO2 and CNT, (B) CNT coated with TiO2 nanoparticles, and (C) CNT wrapped around TiO2 nanoparticles. Reproduced with permission from Mallakpour S, Khadem E. Carbon nanotube–metal oxide nanocomposites: fabrication, properties and applications. Chem Eng J 2016;302:344–67. https://doi.org/10.1016/j.cej.2016.05.038.

to note that some morphological aspects of CNTs can have a significant influence on the photocatalytic performance; these include shape, size, aspect ratio, CNT orientation, homogeneity of the hybrid, and volume fraction of CNTs [39]. Besides these aspects, surface modification of CNT plays a key role in enhancing the adsorption of pollutants and, as in the case of fullerenes, increasing the interaction of TiO2 and this nanocarbon. The modification can be achieved by the introduction of hydroxyl, ketone, or acid functional groups on the surface of CNT during purification of the raw materials [39–41]. The CNT loading also has a significant influence in the observed photocatalytic activity. Table 17.2 presents a selection of the most recent works dealing with CNT-TiO2 hybrids, where different CNT loadings have been investigated. The CNT loading range varies from small values as high as 88 wt%, and the most common optimal values are reported ca. 20 wt% [18, 41]. However, this optimum seems to depend on several properties and the morphology of the photocatalyst, and therefore, on the preparation method. For example, in several studies where TiO2 nanoparticles are randomly mixed with CNT, the PC activity can be increased up to loadings of 85 wt% [42, 43]. Some authors have explained this behavior based on the mechanism of PC enhancement, that is, if the CNT is acting as an electron pool or as a photosensitizer [18]. Therefore, it seems that there is a close relationship between the improvement of the PC performance derived from the presence of CNT and the quantity of TiO2. Thus, if CNT is functioning as an electron sink, TiO2 is the photoactive phase in the hybrid. Therefore, it may be useful to have a higher TiO2 amount, which means a higher TiO2 surface exposed. On the other hand, if CNT is behaving as a photosensitizer, it makes sense that the higher activity is achieved under higher loadings of CNT because it is the photoactive phase. The presence of CNT in TiO2-based materials has a significant effect on their properties. For example, the high surface area of these nanocarbons provides improved adsorption of pollutants and a higher number of photoactive sites through the

534

Table 17.2 Selected publications on the photocatalytic applications of Carbon Nanotubes-TiO2 hybrids Preparation method NC/TiO2

Pollutant or cocatalyst

Hydrogen production

Commercial MWCNT Hydrothermal method

Pt

500 W Xe lamp with a cutoff filter (λ >365 nm) Ccat ¼ 0.2 g L1 NC content ¼ 34–88 wt%

Functionalized commercial MWCNT Commercial TiO2

Pt

Commercial MWCNT Sol-gel

Methylene blue

Medium pressure Hg mercury lamp. Ccat ¼ 1 g L1 NC content ¼ 17 wt%. 4 W UV lamp. Ccat ¼ 0.01 g L1 NC content ¼ 24–66 wt%. [C]0 ¼ 10 mg L1

Functionalized commercial MWCNT Sol-gel

Rhodamine B

Pollutant degradation

Reaction conditions

Filtered Xe lamp (λ >300 nm). Ccat ¼ 0.2 g L1 NC content ¼ 5–30 wt%. [C]0 ¼ 10 mg L1

Highlighted properties and results The hybrid with 44 wt% showed the highest production of H2. The electron-hole separation in the materials was evidenced by photocurrent measurements. The interaction between TiO2 and CNT played an essential role in the H2 production rate. The annealing temperature influenced the photocatalytic degradation of methylene blue. The formation of TidOdC bonds was evidenced by XPS analyses. MWCNT enhanced the absorption of visible light of the hybrids.

Ref. [43]

[40]

[45]

[41]

Nanocarbon and its Composites

Application

Rhodamine 6G

Functionalized commercial MWCNT Sol-gel

Tetracycline Pharmaceutical effluents

Catalytic chemical vapor deposition Hydrothermal method

Salicylic acid

125 W Hg lamp. Ccat ¼ 0.25 g L1 NC content ¼ 1–10 wt%. [C]0 ¼ 50 mg L1 6 W UVC lamp (λ > 240 nm). Ccat ¼ 0.1–0.4 g L1 NC content ¼ 0.5–10 wt%. [C]0 ¼ 0.5–30 mg L1 UVA lamp. Ccat ¼ 1 g L1 NC content ¼ 5 wt%. [C]0 ¼ 14 mg L1

A TOC removal of 83% was achieved in the treatment of pharmaceutical effluents. The hybrids showed an inferior PC performance, compared to commercial TiO2. This behavior was attributed to the TiO2 phase composition of the materials.

[44]

[47]

[48]

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

Functionalized commercial MWCNT Hydrothermal method

Reduced band gap, depending on MWCNT content, was observed. The best PC performance was obtained with 20 wt% content of nanocarbon. The PL signal of the hybrids decreased compared to bare TiO2.

535

536

Nanocarbon and its Composites

dispersion of TiO2. Also, TiO2 is an n-type semiconductor but, in the presence of CNTs, can behave as a p-type semiconductor [16, 39] because the photo-generated electrons in the CB of TiO2 can be easily transferred to the surface of CNT, leaving an excess of holes in the VB. Some authors have reported that the attachment of CNT to the surface of TiO2 can modify its band gap. Park et al. [41] observed up to 1 eV reduction in the band gap of MWCNT-TiO2 hybrids (see Fig. 17.10B); the authors ascribed this reduction to the interaction of unpaired p electrons in the nanocarbon and the Ti atoms. Finally, the reduction of the electron-hole recombination was recently shown by Natarajan et al. [44] using PL analyses. As can be seen in Fig. 17.10A, the PL signal of the MWCNT-TiO2 hybrids was considerably reduced in comparison to pure TiO2. In recent years, CNT-TiO2 hybrids have been successfully applied to the degradation of organic pollutants in the aqueous phase. The degraded pollutants include several organic dyes, such as methylene blue [45], rhodamine B [41], rhodamine 6G [44], methyl orange [46], and some pharmaceutical drugs such as tetracycline [47] and salicylic acid [48]. The environmental applications of these materials also include the degradation of 4-chlorophenol [49], the inactivation of gram-positive bacteria [46], and the treatment of pharmaceutical effluents [47] where an 83% removal of the total organic carbon (TOC) in the effluent was observed. These hybrids have also been employed in the photocatalytic production of hydrogen, or the water splitting reaction [40, 43].

17.2.3 Graphene Since its discovery in 2004 [50], graphene (GR) has been one of the most-studied nanocarbons. This material is composed of a single layer of interconnected hexagons of carbon atoms, and it is considered as the basic building block of other nanocarbons [51, 52]. For example, it can be enclosed into 0D configurations to obtain fullerenes, rolled into 1D structures to produce CNTs, or stacked merely into a 3D structure to obtain graphite [51]. Owing to its attractive properties, GR has become one of the most promising materials in photocatalysis, and especially in TiO2-based photocatalysis. Graphene has excellent electrical and thermal conductivity, derived from its longrange conjugated structure; it also has a substantial theoretical surface area (2630 m2 g1) [50, 52]. The high electrical conductivity makes GR an ideal electron sink or electron transfer conduit to improve the charge-carrier separation. Its extended surface area favors the dispersion of TiO2, and therefore, it provides a higher quantity of active sites and extends the adsorption of pollutants or reactive species. Finally, GR can enhance the light absorption of the hybrids to the visible range [18]. Nowadays, several methods, including physical or chemical routes, are applied in the synthesis of graphene and its derivatives [53]; however, a modification of the so-called Hummers’ method is the most employed. This method consists in the chemical oxidation of graphite and a subsequent physical exfoliation to obtain graphene oxide (GO) sheets, and a final reduction to produce sheets of reduced graphene oxide (RGO) [53, 54]. GO sheets are hydrophilic due to the presence of hydroxyl, epoxy, and carboxyl functional groups, and therefore, they can generate stable aqueous

Intensity (a.u.)

MWCNT AT TNT 10% MWCNT/TNT

350

375

400

(A)

425 450 475 Wavelength (nm)

500

525

550

4.0 TiO2 precursor CS-TiO2 (0)

3.5

CS-TiO2 (5) CS-TiO2 (10)

3.0

CS-TiO2 (20) CS-TiO2 (30)

(ahn)1/2

2.5 2.0 1.5 1.0

2.66 eV 2.08 eV

0.5

2.55 eV 3.12 eV 2.75 eV

3.30 eV

0.0 2.0

(B)

2.2

2.4

2.6

2.8 hn /eV

3.0

3.2

3.4

3.6

Fig. 17.10 (A) Photoluminescence spectra of MWCNT, AT, TNT, and 10% MWCNT/TNT composites at 320 nm excitation wavelength and (B) plots of the Kubelka-Munk function corresponding to the spectra of MWCNT-TiO2 hybrids. From (A) Park CH, Lee CM, Choi JW, Park GC, Joo J. Enhanced photocatalytic activity of porous single crystal TiO2/CNT composites by annealing process. Ceram Int 2018;44:1641–5. https://doi.org/10.1016/j.ceramint.2017.10.086; and (B) Wang W, Serp P, Kalck P, Faria JL. Visible light photodegradation of phenol on MWNT-TiO2 composite catalysts prepared by a modified sol–gel method. J Mol Catal Chem 2005;235:194–9. https://doi.org/10.1016/j. molcata.2005.02.027.

538

Nanocarbon and its Composites

suspensions. Besides, the presence of carboxylic groups allows the anchoring of TiO2 nanoparticles [55], enhancing the transfer of photo-generated electrons or modifying the absorption of visible light of the hybrids, as described earlier. Compared to semimetallic GR, GO is an insulator due to the creation of sp3 hybridization in the carbon network, which interrupts the sp2 conjugated network present in pristine GR [56]. The intrinsic properties of GR can be partly reestablished upon reduction of GO sheets. However, RGO sheets can reaggregate to form graphite due to the removal of the functional groups introduced during the oxidation step of its synthesis [57]. GR and RGO have many advantages compared to other materials used in photocatalysis. For example, GR can be used as a low-cost cocatalyst in many photocatalytic reactions or as a substitute for noble metals, such as Pt or Pd, commonly used in the photocatalytic production of H2 [58]. The band gap of GR and RGO can be tuned, which is an excellent advantage over inorganic semiconductors [13]. For example, Mathkar et al. performed a controlled reduction of GO using hydrazine as a reduction agent [59], achieving a fine control on the band gap of RGO from 3.2 eV to 1 eV (see Fig. 17.11). As one the most studied nanocarbons, GR and its derivatives have been applied to all the reactions covered in this chapter. To date, several reviews have been published covering the photocatalytic applications of these nanocarbons [13, 52, 53, 56, 60–62]. 140

Calculated optical gap

130

Time of hydrazine exposure (h)

120

Tertiary alcohol removal occurs at 108 h

110 100 90 80 70

Reduction of phenol and carbonyl after first 16 h

Reduction of epoxide moiety

60 50 40 30 20 10 0 1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Optical gap (eV)

Fig. 17.11 Gradual decrease of optical gap derived from the chemical reduction of different functional groups in the graphene oxide structure. Reproduced with permission from Mathkar A, Tozier D, Cox P, Ong P, Galande C, Balakrishnan K, et al. Controlled, Stepwise Reduction and Band Gap Manipulation of Graphene Oxide. J Phys Chem Lett 2012;3:986–91. https://doi.org/10.1021/jz300096t.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

17.3

539

Oxide–Nanocarbon

17.3.1 Zinc oxide Zinc oxide (ZnO) is an n-type semiconductor with a direct band gap energy of 3.37 eV, very similar to that of TiO2. However, ZnO has a higher photon absorption efficiency showing, in many cases, a better photocatalytic activity than TiO2 [63]. It also has a high oxidizing power while being abundant, nontoxic, and low cost, which makes it a suitable candidate to replace TiO2. However, ZnO has several disadvantages, such as the fast recombination of photogenerated electron-hole pairs, it is only active with UV light, and it suffers from photocorrosion [64]. To solve these limitations, ZnO has been combined with other materials such as metals, semiconductors, and nanocarbons. In the case of NC, an excellent interaction among ZnO, GR, GO, or RGO has been observed, which leads to an improved PC activity compared with bare ZnO [65–84]. Other authors have highlighted the high specific surface area of the ZnOGO hybrids, which favors the adsorption of pollutants [85, 86]. The enhancement of the PC activity can be explained in terms of the high adsorption capacity of the hybrids and their capacity to act as an electron sink, avoiding the recombination of the photo-generated species [68, 79, 85, 87–93]. A schematic view of the ZnO/RGO activation is shown in Fig. 17.12. The ZnO particle size also plays an important role in enhancing the PC performance. For example, GO/ZnO hybrids with a size less than 100 nm presented high stability and photoactivity [67, 77, 94]. Concerning the amount of graphene in the hybrids, it has been reported that, in most cases, the optimal concentration is less than 5 wt% [86, 87, 94, 95]. ZnO photocorrosion is the main disadvantage for its commercial application in photocatalysis. One way to prevent its deactivation is by depositing the ZnO particles on the graphene structure, which could avoid its interaction with the holes and then favor the pollutant photodegradation [91]. Several reviews on ZnO have been published that include the most relevant aspects of NC-ZnO hybrids [96]. In general, most publications report the use of the hydrothermal/solvothermal method for the synthesis of NC-ZnO hybrids, which allows the

Fig. 17.12 Activation of the ZnO particles distributed on CNT using UV light (A) and visible light (B). Based on Mohd AMA, Julkapli NM, Abd HSB. Review on ZnO hybrid photocatalyst: impact on photocatalytic activities of water pollutant degradation. Rev Inorg Chem 2016;36:77–104. https://doi.org/10.1515/revic-2015-0015.

540

Nanocarbon and its Composites

inclusion of the particles of ZnO on the surface of graphene [65–84]. Other methods have also been tested with good results, such as chemical deposition [86–88, 93], ultrasonic treatment [90, 91], chemical vapor deposition [85, 92], electrospinning [97], photocatalytic reduction [98], and electrochemical deposition [99]. ZnO-GO photocatalysts have been employed in the reduction of CO2 to obtain fuels. These catalysts presented a specific surface area of 236 m2 g1 and good CO2 adsorption capacity (44.8 cm3 g1 of CO2) [73]. After irradiation with UV-light, this catalyst generated 263 μmol g1 of methanol after 3 h. One of the variables studied in the generation of fuels from the reduction of CO2 was the amount of GO. By increasing the concentration of GO, the generation efficiency decreased. This can be affected by the distribution of the ZnO particles on GO and their activation to form the different active species that govern the CO2 photoreduction. Furthermore, ZnO-RGO hybrids prepared by electrochemical deposition have been evaluated in hydrogen generation, obtaining 28.9 μmol H2 g1 in 2 h, which was 4.5 times greater than that achieved with bare ZnO [100]. In other reports, ZnO particles were combined with GR, GO, and RGO and tested in the degradation of dyes, obtaining a higher photoactivity than bare ZnO. Works employing CNTs as a nanocarbon linked to ZnO are scarce [101–104]. Solgel and reflux methods have been mainly used to prepare CNT-ZnO hybrids [102–104]. A high specific surface area and a small particle size of ZnO chemically bonded with CNT is frequently found [102]. For instance, MWCNT-doped ZnO nanofibers were prepared by electrospinning and evaluated in the MB degradation under UV and visible light. Results showed a higher photocatalytic activity (sevenfold) of the MWCNT-doped ZnO compared to bare ZnO under UV light. Besides, this hybrid was also photoactive under visible light. The authors confirmed the Zn-O-C bond formation, which contributed to a lower bandgap, improving charge carrier transport under UV light irradiation (See Fig. 17.12A) or acting as a photosensitizer under visible light, as shown in Fig. 17.12B. Table 17.3 shows the most recent works related to the ZnO-NC hybrids and their applications.

17.3.2 Copper oxides Copper oxides (CuxO) are p-type semiconductors with a bandgap of 1.21–1.51 eV for CuO and 2.0 eV for Cu2O. They have a high capacity to absorb visible light and notable electrical properties. These oxides have been supported mainly in graphene, and there is, to our knowledge, only one investigation in which Cu2O was supported in CNT [105]. The hydrothermal method has been the most used in the preparation of CuxO-NC hybrids [106–108]. In most cases, CuxO-NC hybrids were evaluated in photocatalytic reactions under visible light irradiation. Particulary, a Cu2O-GR hybrids has presented a suitable interaction and distribution of the oxide on the graphene surface, leading to an efficient charge separation and higher photocatalytic activity in dye degradation [109–111]. A successful integration of Cu2O particles with RGO by using an in situ reduction method has been reported with high performance in the photocatalytic production of hydrogen [112]. On the other hand, stability is a crucial aspect of this type of hybrid system. For this reason, it has been found that the preparation method plays an

Table 17.3 ZnO combined with different nanocarbon and their applications in photocatalysis Preparation method

GO

Applications

Reaction conditions

Hydrothermal

Methylene blue degradation

RGO

Hydrothermal

Methylene blue degradation

G

Chemical

Methylene blue degradation

UV light, 100 mL with 5  105 mol L1 of MB, 80 mg catalyst, 120 min adsorption, 100 min irradiation UV light, 100 mL with 1  105 mol L1 of MB, 20 mg catalyst, 30 min adsorption, 90 min irradiation Visible light, 50 mL with 30 mg L1 of MB, 10 mg catalyst, 30 min adsorption, 130 min irradiation

CNT

Reflux

Methylene blue degradation

RGO

Supercritical CO2

H2 Production

RGO

Hydrothermal

Photoreduction of CO2

UV light, 200 mL with 10 mg L1 of MB, 200 mg catalyst, 60 min adsorption, 30 min irradiation UV light, 60 mL with 0.1 mol L1 of Na2S and 0.05 mol L1 of Na2SO3, 100 mg catalyst, 120 min irradiation UV light, 50 mL with 1 M of NaOH, 100 mg catalyst, CO2 gas was bubbled into the solution for 30 min, 180 min irradiation

Highlighted properties and results

Reference

The degradation rate was 54.3% for ZnO and 98.1% for ZnO/GO; this catalyst had been used five cycles.

[65]

The degradation rate was 40% for ZnO spheres, almost 100% for ZnO/ RGO. The optimal concentration of RGO was 3.5%. The degradation rate was 45% for ZnO, 80% for ZnO/GR. The GR amount was 5%, this quantity of G had the highest photocatalytic activity. The degradation rate was 68% for ZnO, 100% for ZnO/CNT. Small crystalline size and chemical bond between ZnO and CNT. The hydrogen generation was 289 μmol h1 by ZnO/RGO. RGO increased 4.5 times the generation of H2 than ZnO.

[102]

The content of RGO 10% generated more quantity of methanol, the dosage of catalyst was 2 g L1, 263.17 μmol methanol g1 this quantity was five times higher than obtained using ZnO (52.36 mol methanol g1).

[74]

[86]

[102]

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

Nanocarbon

[100]

541

542

Nanocarbon and its Composites

important role. For example, by using the pyrolysis method, a more active catalyst is obtained because the oxide particles grow in a single direction; it can also be distributed more evenly, giving rise to a more stable photocatalytic system [113]. The reported photocatalytic activity in hydrogen production was 19.5 mmol H2 g1 h1 under UV-vis light [113]. The effect of Cu1+ or Cu2+ species in the system of CuxO/graphene was studied in the CO2 photocatalytic reduction to produce methanol [114]. CuO species proved to be the most active by their uniform distribution on the surface of graphene, resulting in a better charge separation under visible light.

17.3.3 Tungsten oxide Tungsten oxide (WO3) has been used to modify the properties of nanocarbon and to obtain new hybrid catalysts with better properties. Tungsten oxide is a semiconductor found in nature, stable at different pH values, with a band gap energy of 2.7 eV, insoluble in water, and is considered as a promising semiconductor in photocatalysis [115]. Due to these properties, it has been used to modify graphene mainly, and CNT [116]. The most commonly used method for synthesizing WO3/GR and WO3/CNT was hydrothermal [115, 117, 118]. These catalysts presented a homogeneous distribution of the WO3 particles on graphene oxide and excellent interaction between the two particles, which leads to an adequate charge separation and therefore is reflected in higher photocatalytic activity. As a result, these hybrids systems presented a good adsorption capacity along with a high photocatalytic activity in the degradation of pollutants [117–119]. WO3-GR hybrids have also been tested in the photocatalytic reduction of CO2, showing a significant selectivity to methane [115]. In this case, the synergy between two components was shown by a significant displacement of the WO3 conduction band to more negative values, making thermodynamically possible the reduction of CO2. Table 17.4 shows some selected examples using NC-metal oxide hybrids and their photocatalytic applications.

17.4

Chalcogenide-Nanocarbon

Chalcogenides are chemical compounds that contain in their structure an element of the group (16 or VI A) of the periodic table. The term chalcogenide is used mainly to refer to some compounds containing sulfides, selenides, and tellurides. The application of this type of semiconductor is extensive and varied, mainly focused on energy storage.

17.4.1 Cadmium sulfide One of the most-studied chalcogenides is cadmium sulfide (CdS). This material is insoluble in water, has a band gap of 2.4 eV, and absorbs energy in the visible region. It has the disadvantage of displaying a high recombination of the photo-generated pair electron-hole and also presents the phenomenon of photocorrosion [120]. However, CdS supported on graphene presented a superior photocatalytic activity than that of

Nanocarbon

Metal Oxide

Preparation method

GR

Cu2O

CNT

Applications

Reactions conditions

CVD

Methyl orange degradation

WO3

Solvothermal

Methylene blue degradation

RGO

Bi2O3

Solvothermal

Methylene blue degradation

graphene

CuO, Cu2O

Covalent grafting

Photoreduction of CO2 to methanol

Visible light, 80 mL with 30 mg L1 of MO, 20 mg catalyst, 30 min adsorption process, 30 min irradiation Visible light, 100 mL with 10 mg L1 of MO, 20 mg catalyst, 60 min adsorption process, 120 min irradiation Visible light, different concentration of MB, 100 mL the solution of MB, 6 h of irradiation Visible light, 45 mL DMF and 5 mL water, degas with N2, CO2 gas was added, 100 mg catalyst, 24 h reaction

GO

WO3

Hydrothermal

Photoreduction of CO2 into CH4

Visible light, 270 mL total volume, 1 mL of water was injected, some quantity of CO2 with high purity was introduced, O2 gas generated, 8 h reaction

Highlighted properties and results The abundance of defects affects the catalytic activity (80% of the MO was degraded). The degradation rate was 25% for WO3, 55% for WO3/CNT.

Reference [109]

[116]

Neutral pH, degradation rate was 55% for Bi2O3, 98% for Bi2O3/RGO.

[180]

The CuO species is more active than Cu2O species. 1282 μmol methanol g1 was obtained. 0.89 μmol CH4 was obtained after 8 h.

[114]

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

Table 17.4 Summary of photocatalytic applications of different NC-metals oxide

[115]

543

544

Nanocarbon and its Composites

bare CdS, which was explained by a better charge separation [120, 121]. For example, for CdS spheres deposited on graphene by a solvothermal method and evaluated in rhodamine-B degradation, a 95% removal of the model compound after 85 min of reaction time under visible light was found [120–122]. The tereftalic acid fluorescence technique was used to check hydroxyl radical generation in CdS and CdS-graphene, giving positive results in both cases. It was also found that due to the VB position of CdS, it is not thermodynamically possible to carry out the photooxidation of water. Therefore, the hydroxyl radicals are generated by the exchange of free electrons in the graphene network reacting with O2 [121–126]. In another report, RGO was hybridized with CdS, proving that by using visible light, the semiconductor was activated. A photocorrosion effect was also detected when measuring 3.5 wt% of Cd2+ in solution at the end of the experiment [127]. In other investigations, CdS was supported on reduced graphene oxide (RGO) employing the solvothermal method [122, 123, 125, 128–131], the combustion method [126], and the gamma reduction method [128]. In all cases, it was found that the separation of the photo-generated charge carriers was more efficient because the electrons generated by the CdS were transferred to the RGO network and this acted as an electron sink (see Fig. 17.13). CdS deposited on RGO was prepared by a high-temperature reaction and tested in hydrogen production [131], obtaining 14.6 mL H2 g1 in 2 h of irradiation with visible light. This photocatalyst was compared with a catalyst synthesized by the hydrothermal method, obtaining only 10.8 mL H2 g1. In this case, it was possible to improve the catalytic activity because the high-temperature reaction produced a better interaction of the CdS particles and the RGO compared to the hydrothermal method. Fig. 17.13 CdS semiconductor impregnated on RGO and the distribution of the charges.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

545

Fig. 17.14 Schematic illustration of the photocatalytic process on: (A) pure CdS and (B) C60/CdS nanocomposite. Reproduced with permission from Cai Q, Hu Z, Zhang Q, Li B, Shen Z. Fullerene (C60)/CdS nanocomposite with enhanced photocatalytic activity and stability. Appl Surf Sci 2017;403:151–8. https://doi.org/10.1016/j.apsusc.2017.01.135.

Furthermore, CdS particles deposited on C60 evolved 1.7 mmol H2 g1 h1, and the stability of the catalyst was studied at the same time. This proved that when using pure CdS, a significant amount of Cd2+ is produced in solution by photocorrosion. The C60CdS hybrid acted as an excellent electron acceptor and at the same time, as a carrier of the photogenerated electrons. On the other hand, it was evidenced that holes migrate to the surface of the fullerene, thus preventing the CdS photocorrosion (see Fig. 17.14) [132]. With respect to CNT-CdS hybrids tested in photocatalytic hydrogen production, hydrogen evolution under visible light at a rate of 1.8 mmol H2 g1 h1 was found. This results were, again, explained in terms of the improved photo-generated charge separation after the chemical interaction of CNT with CdS [133]. Table 17.5 summarizes representative examples of NC-CdS hybrids applied in photocatalytic reactions.

17.4.2 Other sulfides Sulfides are another quite important member of the chalcogenides family. For instance, copper sulfide (CuS) was supported in GR and RGO and tested in the adsorption and degradation of organic pollutants [134–137]. These hybrids were activated by

546

Table 17.5 Most relevant examples of photocatalytic applications of NC-CdS hybrids Nanocarbon

Preparation method

RGO

Reactions conditions

Solvothermal

Photoreduction of CO2

RGO

Hydrothermal

Rhodamine B degradation

GO and RGO

Impregnation and hightemperature reaction Hydrothermal

Water splitting

Visible light, 80 mg catalyst, 500 mL solution of MB and 100 mgL1 of MB, adsorption process was the overnight; irradiation time was 3 h Visible light, 70 mg catalyst, 70 mL solution of MB and 5 mg L1 of Rhodamine B, adsorption process was 30 min, irradiation time was 60 min Visible light, 250 mL 0.01 M Na2S, 0.004 M Na2SO3, 100 mg catalyst, N2 was bubbled for 60, 120 min irradiation Visible light, 25 mg of catalyst, 50 mL solution lactic acid 10%v and 1 wt% of Pt. Degradation of Rhodamine B: visible light, 20 mg of catalyst, 20 mL solution 10 mg L1 Rhodamine, 30 min adsorption, 40 min irradiation Visible light, 180 mL with 15.13 g of Na2S and 5.67 g of Na2SO3, 100 mg catalyst, 300 min irradiation

Fullerene (C60)

CNT

Hydrothermal

H2 generation and rhodamine B degradation

Water splitting

Highlighted properties and results

Reference

The optimal quantity of RGO was 5wt%, The degradation rate was 94% for CdS/RGO, and 57% of TOC was removed.

[122]

The degradation rate of rhodamine B was 95% after 50 min of irradiation.

[129]

Hydrogen generation was 9.6 mL g1 for 2 h using CdS/ GO and for CdS/RGO was 14.6 mL g1 for 2 h H2 generation was 1.73 mmol h1 g1, the removal% of the dye was 97 in 40 min., and optimal concentration of C60 was 0.4 wt%.

[131]

1.771 mmol g1 h1 of H2 was generated using this catalyst, visible light.

[133]

[132] Nanocarbon and its Composites

Applications

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

547

both visible and ultraviolet light, showing an improved photocatalytic activity superior to that presented by pristine CuS. This was attributed to the enhanced separation of the photo-generated charges in the nanocarbons and a high capacity to adsorb pollutants. Another chalcogenide supported on RGO was bismuth sulfide (Bi2S3), which was synthesized using a poly sodium-p-styrenesulfonate, achieving a homogeneous distribution of Bi2S3 nanoparticles on RGO. The use of this nanocarbon increased the PC activity 3.1 times compared to pure Bi2S3 [138]. Additionally, Bi2S3 flower-like particles supported on RGO were used to decolorize a crystal violet dye, reaching 97% of the dye in 100 min with a percentage of 3 wt% in RGO as the optimal concentration [139]. Besides, indium sulfide (In2S3) was supported on graphene using the hydrothermal method, and its photoactivity was measured in the degradation of methyl orange [140]. In this case, after dye excitation with visible light, the photogenerated electrons were transferred to the chalcogenide and then to graphene, as shown in Fig. 17.15. In another illustrative example, antimony sulfide (Sb2S3) was supported on RGO using the hydrothermal method and activated with visible light. It presented a large specific surface area, high adsorption capacity, and the RGO acted as a charge conduction network, inhibiting the recombination process and thereby increasing efficiency in the discoloration process [141]. Another type of chalcogenide is the ternary one. In all the investigations, zinc and indium were the common elements in the synthesis of the ternary chalcogenides [141–147]. These ternary chalcogenides

Fig. 17.15 Schematic illustration showing the reaction mechanism for photocatalytic degradation. Reproduced with permission from An X, Yu JC, Wang F, Li C, Li Y. One-pot synthesis of In2S3 nanosheets/graphene composites with enhanced visible-light photocatalytic activity. Appl Catal B Environ 2013;129:80–8. https://doi.org/10.1016/j.apcatb.2012.09.008.

548

Nanocarbon and its Composites

were supported in two different nanocarbons, RGO and CNT. In particular, ZnIn2S4 supported on RGO showed a god photon absorption in the visible region with a bandgap energy of 2.34–2.48 eV [142, 143]. It was tested in the degradation of 4-nitrophenol under solar light, presenting high photocatalytic activity and stability. Pure ZnIn2S4 also showed good photoactivity under visible light but with severe photocorrosion. Therefore, the stability of ZnIn2S4 supported on RGO was attributed to the formation of a Zn-O-C covalent bond between two species [142]. Furthermore, a comparison of some nanocarbon structures were mixed with ZnIn2S4 and tested in hydrogen generation. The interaction between the ZnIn2S4 particles and the nanocarbon particles achieved a separation of the photo-generated electron-hole, which generated 2641 μmol H2 g1 h1 [143]. ZnCdS was supported on RGO and CNT [144–146], absorbing energy in the visible region of the spectrum and presenting a lower charge recombination, making their efficiency higher than other chalcogenides. A catalytic formulation type Zn0.83Cd0.17S/ CNT was tested in hydrogen generation, obtaining 5.41 mmol H2 h1 g1. This amount of hydrogen was higher compared to that obtained with other chalcogenide mixtures. It was found that the optimal CNT ratio was 0.25 wt%., which also had a strong effect on the chalcogenide crystal size. [144]. Table 17.6 shows some selected examples of NC-chalcogenides with photocatalytic applications.

17.5

MOFs–Nanocarbon

Metal-organic frameworks (MOFs), also known as porous coordination polymers (PCPs), are composed of metal-based centers (single ions and clusters) linked to organic ligands by strong coordination bonds to form a one-, two-, or threedimensional coordination network [147]. Due to their excellent properties, such as an extremely high surface area (>10,000 m2 g1), tunable pore size, and high pore volume [148], MOFs have attracted significant interest in different applications such as catalysis, gas storage and separation, optics, dye adsorption, biomedical imaging, chemical sensing, and drug delivery [149–151]. In the past few years, several investigation groups have begun to explore their potential as photocatalysts [152–155]. Kuc et al. demonstrated through a theoretical study that MOFs are semiconductors with a band gap between 1.0 and 5.5 eV [156]. Garcia et al. showed the photocatalytic properties of MOF-5, allowing increased attention of the MOFs as photocatalysts (Fig. 17.16) [148, 150, 157]. Various MOFs have been studied as photocatalysts for different applications such as MOF-5 [149], UiO-66 (NH2) [158], NH2-Mil-88 (Fe) [159], and NH2-MIL-68(In), among others [160]. Even though MOFs have good photocatalytic properties, they are inferior to those found for inorganic semiconductors due to the low efficiency for light-to-energy conversion and separation of photogenerated electron-hole pairs. Also, it is well known that some MOFs show instability to thermal treatments, moisture, or chemical agents, which limits their application in different areas. Thus, the scientific community is searching for strategies to improve the stability and photocatalytic activity of MOFs (Fig. 17.17) [161]. Fig. 17.16 shows the number of publications of MOFs and MOFcomposite materials as photocatalysts during the past 9 years.

Nanocarbon

Chalcogenide

Preparation method

RGO

WSe2

Solvothermal

Rhodamine B degradation

GR

CuS

Sol-gel

Methylene blue degradation

RGO

Bi2S3

Hydrothermal

2,4 Dichlorophenol

GO

In2S3

Hydrothermal

Methyl orange degradation

RGO CNT

ZnIn2S4

Microwaveassisted and hydrothermal

Hydrogen generation

Applications

Reactions conditions

Highlighted properties and results

Visible light, 30 mg catalyst, 100 mL solution with 20 ppm Rhodamine B, 30 min adsorption, 0.2 mL H2O2 Visible light, 50 mL solution, 80 ppm MB, 2.5 mL H2O2, 30 min adsorption, 150 min irradiation Visible light, 100 mL with 60 ppm pollutant, 0.08 mg catalyst, 120 min irradiation Visible light, 20 mg catalyst, 20 mL with 25 ppm of MO, 120 min was the adsorption and 120 min irradiation 50 mg catalyst, 80 mL Triethanolamine 10%v, N2 was bubbled

The degradation rate was 60% in 3 h.

[181]

The degradation rate was 93% after 80 min; the size particle was 16 nm, 10 wt% of graphene was the optimal quantity. The degradation rate was 92% after 2 h. The RGO 8 wt% was the optimal concentration.

[135]

Reference

[138]

[140]

The generation of H2 for CNT and RGO were 1601.5 and 2640.8 μmol H2 g1 h1, respectively.

[143]

549

Degradation rate was 98% after 120 min. GO was 1% in the hybrid catalyst.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

Table 17.6 Some examples of NC-Chalcogenides hybrids and their photocatalytic applications

550

Nanocarbon and its Composites

Fig. 17.16 Number of publications on MOFs (blue) and MOFs composites (red) as photocatalysts (based on Scopus database).

Fig. 17.17 Applications more relevant of nanocarbons-MOFs hybrid materials.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

551

The integration of a variety of functional materials such as GR, CNTs, metal nanoparticles, nanorods, metal oxides, complexes, and even enzymes has been shown to improve the stability and photocatalytic properties of pristine MOFs. This incorporation can be possible due to the pore nature of MOFs that encapsulates some catalytically active molecules or nanoparticles [162, 163]. The incorporation of nanocarbons in MOFs through different methods (one-step solvothermal, two-step solvothermal, one-step hydrothermal, random mixing, single/multiple-face interaction, etc.) has improved their physicochemical and photocatalytic properties, being of great interest for different applications (Fig. 17.18). Table 17.7 shows the more representative studies of nanocarbon-MOF nanocomposites as semiconductors in different applications. Pi et al. synthesized MWCNT/NH2-MIL-68(In) composite materials by the onestep solvothermal method using MWCNTs treated with HNO3 (70% vol.) [164]. All composite materials showed very similar x-ray diffraction patterns, indicating that the crystalline structure of the parental NH2-MIL-68(In) remained intact. The N2 adsorption-desorption isotherm of the hybrids showed a type I isotherm, characteristic of micropore materials, and small hysteresis loops, indicating the presence of a small number of mesopores for the capillary condensation. The interaction between MWCNTs and NH2-MIL-68(In) allowed a slight increase in their BET surface area. They also observed through XPS a negative shift of 0.4 eV in the in the 3D spectrum of the hybrids, confirming the successful incorporation of MWCNTs in NH2-MIL-68 (In). According to these results, the introduction of MWCNTs in NH2-MIL-68(In) contributes to better photocatalytic properties in the reduction of Cr(VI) through the adding of new mesopores for Cr(VI) diffusion, enhancing the visible light absorption, and decreasing the recombination of photo-induced electrons/holes (Fig. 17.19).

Fig. 17.18 (A) Factors controlling the structural stability of MOFs in aqueous media, and (B) methods used to improve the hydrostability and hydrothermal cyclic stability of MOFs. Reproduced with permission from Kumar P, Vellingiri K, Kim K-H, Brown RJC, Manos MJ. Modern progress in metal-organic frameworks and their composites for diverse applications. Microporous and Mesoporous Mater 2017;253:251–65. https://doi.org/10.1016/j.micromeso. 2017.07.003.

552

Table 17.7 Summary of different nanocarbon-MOFs hybrids as photocatalysts in different applications MOF

Preparation method

Applications

Reactions conditions

RGO (1–10 wt%)

UiO-66 (NH2)

Selfassembly

Reduction of Cr(VI)

λ ¼ 420 nm, 20 mg photocatalyst, 40 mL of 10 ppm Cr(VI) T ¼ 30°C, pH ¼ 2

RGO (1.3–3.2 wt%)

Mil-53 (Fe)

One-step solvothermal

Methylene blue degradation

RGO (1–20 wt%)

NH2MIL-125 (Ti)

One-step solvothermal

Methylene blue Degradation

MWCNTs (4.2–18.9 wt%)

NH2MIL68 (In)

One-step solvothermal

Reduction of Cr(VI)

RGO (50 wt%)

UiO-66NH2

in situ growth and mixing methods

Water splitting

125 W high-pressure Hg lamp (λ ¼ 365 nm) and 250 W (λ > 420 nm) 100 mg photocatalyst 200 mL 30 ppm MB 300 W Xenon lamp (λ ¼ 420 nm), 30 mg photocatalyst 40 mL of MB (5.4  105 mol L1) 500 W Xe lamp, 40 mg photocatalyst 50 mL of a K2Cr2O7 and Cr(VI) (10 ppm) pH to 4.0 Visible light 5 mg of photocatalyst 100 mL MeOH or TEOA

Highlighted properties and results RGO enhanced the visible light absorption and more efficient separation of photogenerated electronhole pairs. RGO separate the photogenerated electrons suppressing electron-hole recombination.

Reference [182]

[163]

The synergistic effect of NH2-MIL-125(Ti) and RGO as well as the Ti3+Ti4+ intervalence electron transfer, was observed. MWCNTs generated new mesopores that facilitate the diffusion of Cr(VI).

[165]

The graphene wellwrapped UiO-66-NH2 octahedrons showed a

[167]

[164] Nanocarbon and its Composites

Nanocarbon

Ultrathin graphene oxide (1–11 wt%)

MIL-88A (Fe)

One-step hydrothermal

Rhodamine B degradation

500 W Xe lamp (λ ¼ 420 nm), 20 mg photocatalyst 50 mL of 10 ppm RhB H2O2 (20 mM) and pH ¼7

superior electron transfer ability that inhibited moreefficient the recombination of electronhole pairs. GO improved the separation of photoinduced electron-hole pairs and generated highly reactive O2 species with enhanced activity.

[183]

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

(sacrificial reagent) Erythrosin B (0.05 g) or Rhodamine B (sensitizer)

553

554

Nanocarbon and its Composites 2.5

2.1

PL-3 PL-2 PL-1 NH2-MIL-68(In)

Absorbance (a.u.)

1.8

(a)

(b)

(c)

1.5

(d)

(Ahv)1/2

2.0 1.5 1.0 0.5 0.0

1.2

1.5

2.0

2.5 hv (eV)

3.0

3.5

0.9 0.6 0.3 0.0 200

(A)

MWCNT PL-3 PL-2 PL-1 NH2-MIL-68(In)

300

400

500 600 Wavelength (nm)

700

800

(B) Fig. 17.19 (A) UV-Vis DRS spectra and (B) Schematic illustration of the reduction of Cr(VI) on PL-1 under irradiation. From Pi Y, Li X, Xia Q, Wu J, Li Z, Li Y, et al. Formation of willow leaf-like structures composed of NH2–MIL68(In) on a multifunctional multiwalled carbon nanotube backbone for enhanced photocatalytic reduction of Cr(VI). Nano Res 2017;10:3543–56. https://doi.org/10.1007/s12274-017-1565-8.

Huang et al. used an easy and straightforward synthesis method for the integration of RGO/NH2-MIL-125(Ti) hybrid nanocomposites for methylene blue (MB) photocatalytic degradation under visible-light irradiation [165]. Pristine NH2-MIL-125 (Ti) was synthesized using tetra-n-butyl titanate as a source of titanium. SEM images of RGO-NMTi-x nanocomposite materials revealed particles slightly agglomerated

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

555

with different surface morphology. The use of RGO as a support severely affected the crystalline structure of MOF NH2-MIL-125(Ti), which was attributed to strong interactions between RGO and NH2-BDC linkers provoking a considerable distortion of the TiO5(OH) paddlewheel and modifying the crystal structure. In this case, hybrid materials showed low specific surface areas compared with the pristine MOF NH2MIL-125(Ti). They also showed that the synergistic effect between RGO and NH2MIL-125(Ti) could lead to a significant reduction in the recombination rate of the photogenerated electron-hole charge carriers, increasing the photocatalytic performance in the degradation of MB (Fig. 17.20). MOFs as photocatalysts for hydrogen production have shown an efficiency much inferior to that of the currently used semiconductors [166]. Therefore, Wang et al. showed that proper surface modification of MOF is crucial for the enhancement of MOF-based photocatalytic properties [167]. They used three ways for synthesizing graphene/UiO-66-NH2 octahedron composite materials: (1) random mixing (RCGO/ U6N), (2) single-face interaction (RDGO/U6N), and (3) multiple-face interaction of graphene and UiO-66-NH2 octahedrons (RGOWU6N). All materials were used in the photocatalytic H2 production in the presence of a sacrificial reagent (MeOH and TEOA) and sensitizer (erythrosin B and rhodamine B) under visible light (Fig. 17.21). All hybrid materials showed X-ray diffraction patterns typical of UiO-66-NH2 octahedral crystals. As a result, the photoluminescence of composite materials showed a better separation of photo-generated electron-hole charge carriers due to the participation of RGO. In addition, fluorescence lifetime experiments showed apparently longer lifetimes for the MOF hybrids. However, RGO-WU6N material synthesized by method (3) with 50 wt% of graphene exhibited higher catalytic activity due to the fact that every face of the UiO-66-NH2 octahedrons was covered with RGO sheets, as shown in the TEM and SEM images of Figs. 17.21C and F). Besides, this

Fig. 17.20 (A) UV-vis DRS spectrum of (a) rGO-NMTi-1, (b) rGO-NMTi-2, (c) rGO-NMTi-3, and (d) rGO-NMTi-4. (B) MO degradation photocatalytic performance of (a) no catalyst, (b) NH2-MIL-125(Ti), (c) rGO-NMTi-1, (d) rGO-NMTi-2, (e) rGO-NMTi-3, and (f ) rGONMTi-4. Reproduced with permission from Huang L, Liu B. Synthesis of a novel and stable reduced graphene oxide/MOF hybrid nanocomposite and photocatalytic performance for the degradation of dyes. RSC Adv 2016;6:17873–9. https://doi.org/10.1039/C5RA25689E.

556

Nanocarbon and its Composites DMF

ZrCl4 + BDC-NH2

+

(a)

DMF

+ GO

UiO-66-NH2

(b)

H

2O

+H

Cl

(A)

(c)

(B) Fig. 17.21 (A) Schematic for the preparation of RCGO/U6N (a), RDGO/U6N (b), and RGOWU6N (c). (B) TEM and SEM images of RCGO/U6N (a) and (d), RDGO/U6N (b) and (e) , and RGOWU6N (c) and (f ). Reproduced with permission from Wang Y, Yu Y, Li R, Liu H, Zhang W, Ling L, et al. Hydrogen production with ultrahigh efficiency under visible light by graphene well-wrapped UiO-66-NH2 octahedrons. J Mater Chem A 2017;5:20136–40. https://doi.org/10.1039/ C7TA06341E.

material exhibited after four reaction cycles a good reproducibility, revealing that the graphene well-wrapped UiO-66-NH2 octahedrons inhibit the electron-hole recombination. They mentioned that the higher catalytic activity shown in the RGOWU6N material can be due to its superior electron transfer ability inhibiting the recombination of electron-hole pairs because every face of the UiO-66-NH2 octahedrons was covered with RGO. MOFs are composed of metallic nodes joined in an ordered fashion by organic linker molecules, which could be used as a precursor to prepare metal oxide nanoparticles and porous metal oxide-carbon hybrids via heat treatment at ambient

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

557

(air or nitrogen) conditions [168–170]. In 2011, Yang et al. were pioneers in the preparation of ZnO nanoparticles and ZnO@C hybrid composites via simple heat treatment of MOF-5 under a variety of atmospheric gaseous conditions [168]. Novel ZnO nanoparticles with 3D cubic morphologies were obtained through heat treatment at 600–700°C for 3 h under air flow while ZnO@C composites were prepared by the same method as those used in the case of ZnO nanoparticles. However, in this case, this was done by using a nitrogen flow. SEM and TEM analysis of ZnO@C hybrid composites showed clusters of ZnO with a hexagonal structure embedded in the carbonaceous matrix (Fig. 17.22). Both materials were used in the adsorption and photocatalytic decomposition of RhB dye under UV irradiation. ZnO nanoparticles showed good photocatalytic activity concerning RhB degradation while ZnO@C hybrid materials showed excellent adsorption capacity of organic dyes.

17.6

Multicomponent–Nanocarbon

Nanocarbon multicomponent mainly include ternary systems with the combinations of semiconductor-NC-semiconductor or semiconductor-NC-metal, where the NC that dominates in most of the reported works is graphene of the GO or RGO type. It has found good compatibility at coupling graphene with semiconductors and metals, leading to functional nanomaterials with high stability, photon absorption in the visible region, and improved electrical conductivity [171].

17.6.1 Metal oxide 1-NC-metal oxide 2 In this category, the following systems have been reported: ZnO-graphene-TiO2, Cu2O-RGO-TiO2, WO3-GO-TiO2, TiO2-RGO-Ag2O, Cu2O-RGO-Bi2O3, or others, including five components, ZnO-Fe2O3-Fe3O4-RGO-Cu. Interestingly, this last novel core-shell (rGO@CuZnO@Fe3O4) structured photocatalyst (Fig. 17.23) was synthesized by a complicated method and evaluated in the CO2 photocatalytic reduction with water using visible light. The primary product of the CO2 photoreduction was methanol with a high yield of 2656 μmol/gcat, and it was easily recovered by an external magnet. This superior photocatalytic activity, compared with the use of GO or without any nanocarbon, was attributed to a better charge separation induced by an sp2 hybridization of the aromatic system in RGO [172].

17.6.2 Metal oxide-NC-chalcogenide This type of heterostructure has been devised to have excellent photon absorption in the visible region, mainly by the chalcogenide, and then to transfer the photogenerated electrons to the metal oxide using a nanocarbon. Such is the case of the systems of TiO2-RGO-CdS, Nb2O5-N-doped graphene-CdS, ZnO-RGOCdS, TiO2-RGO-SnS2, and Fe2O3-graphene-MoS2, among others. Similarly as in the previous case, what is pursued with multiheterostructures is an efficient synergistic effect that manifests itself in a high charge-carrier transport rate. For example, an NiO@Ni-ZnO/RGO/CdS photocatalyst has been synthesized by a multistep

558 Nanocarbon and its Composites

Fig. 17.22 (A–C) FE-SEM images, (D) TEM image, (E) EDS spectrum, and (F) EEL spectrum of ZnO@C hybrid. Reproduced with permission from Yang SJ, Im JH, Kim T, Lee K, Park CR. MOF-derived ZnO and ZnO@C composites with high photocatalytic activity and adsorption capacity. J Hazard Mater 2011;186:376–82. https://doi.org/10.1016/j.jhazmat.2010.11.019.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

559

Fig. 17.23 Plausible mechanism of CO2 reduction by rGO@CuZnO@Fe3O4. Reproduced with permission from Kumar P, Joshi C, Barras A, Sieber B, Addad A, Boussekey L, et al. Core–shell structured reduced graphene oxide wrapped magnetically separable rGO@CuZnO@Fe3O4 microspheres as superior photocatalyst for CO2 reduction under visible light. Appl Catal, B 2017;205:654–65. https://doi.org/10.1016/j.apcatb.2016.11.060.

method and evaluated on the photocatalytic hydrogen generation reaction under UV and visible light [173]. By comparison to Ni-ZnO-RGO, ZnO-RGO-CdS, or CdS, the multicomponent heterostructure of NiO@Ni-ZnO/RGO/CdS showed tahe higher hydrogen production yield of 824 and 524 μmol h1 under UV-vis and visible light, respectively. These results were explained regarding a synergy between ZnO and CdS enhanced by RGO, which forms a photoexcited carrier transport channel and NiO@Ni acted as a cocatalyst in capturing the photo-generated electrons, as shown in Fig. 17.24. Fig. 17.24 Scheme of photocatalytic reaction process in the NiO@Ni-ZnO/ rGO/CdS heterostructure. Reproduced with permission from Chen F, Zhang L, Wang X, Zhang R. Noble-metal-free NiO@Ni-ZnO/ reduced graphene oxide/CdS heterostructure for efficient photocatalytic hydrogen generation. Appl Surf Sci 2017;422:962–9. https:// doi.org/10.1016/j.apsusc.2017.05.214.

560

Nanocarbon and its Composites

Cr(VI) Bi2S3

Visible light

BiOI

Potential (eV vs NHE)

–1

0

O2 O2/•O2-(–0.046)

e–

•O2–

e–

e–

e–

CB: –0.74

e–

e–

Cr(III)

CB: –0.39 e– e– e–

H+

1

e–

•OH

h+

VB: 1.43 Phenol

•OH/h+

h+

VB: 1.09 h+

h+

2

RGO Degradation products

Fig. 17.25 Proposed reaction mechanism for simultaneous Cr (VI) and phenol removal over Z-scheme BiOI/rGO/Bi2S3 system. Reproduced with permission from Chen A, Bian Z, Xu J, Xin X, Wang H. Simultaneous removal of Cr(VI) and phenol contaminants using Z-scheme bismuth oxyiodide/reduced graphene oxide/bismuth sulfide system under visible-light irradiation. Chemosphere 2017;188:659–66. https://doi.org/10.1016/j.chemosphere.2017.09.002.

An all solid-state Z-scheme system containing bismuth oxyiodide (BiOI) and bismuth sulfide (Bi2S3) supported on RGO with applications in the simultaneous photoreduction of Cr6 and the photooxidation of phenol has been recently reported (See Fig. 17.25) [174]. This photocatalytic system was prepared through an electrostatic self-assembly method with a high photocatalytic activity under visible light, achieving optimal reductive and oxidative efficiencies up to 73% and 95%. According to the results, a fast electron-hole separation occurs between two semiconductors through the surface of RGO.

17.6.3 Semiconductor-NC-metal Metal nanoparticle deposition (e.g., Ag, Au, Pt) on semiconductors results in the formation of a Schottky barrier favoring the transport of photogenerated electrons from the CB of the photoexcited semiconductor to the nanoparticles, and of course, suppressing the recombination pathway [175]. On the other hand, depending on the size of the morphology of the deposited metal NP, Ag, Au, and Cu can present the surface plasmon resonance (SPRE) effect, showing the band gap narrowing to the visible region, and higher efficiency in the transport and distribution of charge carriers [175]. For instance, Ag NP and graphene were coloaded on TiO2 via a surfactant-free solvothermal method and tested in the photocatalytic degradation of paraoxon (an organophosphorus compound) [176]. As a result, a 6 wt% Ag 1 wt% graphene

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

561

Fig. 17.26 Schematic illustration of the activation mechanism of Ag nanoparticle and graphene coloaded TiO2 nanocomposite under visible light irradiation for Paraoxon photocatalytic degradation. Reproduced with permission from Keihan AH, Hosseinzadeh R, Farhadian M, Kooshki H, Hosseinzadeh G. Solvothermal preparation of Ag nanoparticle and graphene co-loaded TiO2 for the photocatalytic degradation of paraoxon pesticide under visible light irradiation. RSC Adv 2016;6:83673–87. https://doi.org/10.1039/C6RA19478H.

deposited in graphene showed the highest photocatalytic activity under visible light, resulting in conversion and TOC removal of the pollutant at close to 100% at 100 min of reaction time. An interpretation of these results included better adsorption of the contaminant and high electron mobility, which decreased the recombination of the photogenerated electron-hole pair, as shown in Fig. 17.26. Table 17.8 summarizes the most relevant examples of nanocarbon-multicomponent systems applied in several photocatalytic reactions. In most cases, the improved adsorption of reactants and remarkable photocatalytic performance with visible light were reported.

17.6.4 Semiconductor nanocarbon-MOFs multifunctional materials Metal oxides (TiO2, WO3, CuOx, SnO2, and ZnO) have been extensively used as photocatalysts in a variety of applications, including photocatalytic degradation of various organic water pollutants, fuel generation through water splitting and carbon dioxide reduction, and CO2 reduction to added-value products. However, some metal oxides such as pure ZnO, CeO2, and TiO2 are almost inactive under visible light illumination (a band gap of 3.2 eV). Also, they have shown a low surface area with a small number of catalytic sites responsible for carrying out the chemical reactions, and in some cases, the fast recombination of photogenerated electron-hole pairs has been observed. Significant efforts are being made to suppress the recombination of photo-generated charge carriers, to decrease the band gap, and to increase the number of catalytic sites and reaction centers. The synthesis of MOF composite materials with

562

Table 17.8 Summary of NC-multicomponent materials as photocatalysts in different photocatalytic applications Nanocomposite

Preparation method

Photocatalytic applications

Highlighted properties and results

References

ZnO/GR/TiO2

Solvothermal

Rhodamine B and industrial dyes

[184]

Cu2O/RGO/ TiO2

Photoreduction

Methylene blue degradation

ZnO/NH2RGO/TiO2 Cu2O/RGO/gC3N4

Hydrothermal

Methyl orange degradation

Self-assembled

Methyl orange degradation

TiO2/RGO/Pd

Rhodamine B degradation

Cu2O/GR/TiO2

Hydrothermal and photodeposition Solvothermal

CdS/GR/TiO2

Hydrothermal

Methylene Blue and p-Chlorophenol degradation

ZnO/RGO/TiO2

Microwave

Reduction of Cr(VI)

MoS2/RGO/ CdS nanorods

Different methods were used

Water splitting

ZGT exhibited a high performance for dye wastewaters. Enhanced dye adsorption/separation of the generated electron-hole pairs and decreased band gap. It was observed excellent dye adsorption and improved charge transport. Improved photocatalytic activity and restrained the recombination of electrons and holes. Pd species acted as an electron acceptor, and RGO presented as high electrical conductivity. Cu2O enhanced the light absorption, and graphene reduced the recombination of carriers. The coupling of graphene expanded photoabsorption range increased the adsorption capacity and efficient separation of electronhole pairs. Increased light absorption intensity and the reduction of electron-hole pair recombination. Effective separation of photogenerated charge carriers led to efficient H2 production.

Rhodamine B degradation

[185]

[186] [187]

[188]

[189]

[190]

[192]

Nanocarbon and its Composites

[191]

Rhodamine B degradation

Improved photogenerated charge carriers transfer and separation at the interface.

[193]

Photodeposition

Methyl orange degradation

[194]

NiO@Ni-ZnO/ RGO/CdS

Multistep

Water splitting

WO3/GO/TiO2

Hydrothermal

Degradation of BPA (2,2-bis (4hydroxy-phenyl) propane)

CdS/RGO/TiO2

Solvothermal

TiO2/CNT/ZnO

Sol-gel

Methylene blue and rhodamine B degradation Methyl orange degradation

ZnO/RGO/TiO2

Hydrothermal

Reduction of Cr(VI)

BiOI/RGO/ Bi2S3 TiO2/GO/Ce

Electrostatic self-assembly Sol-gel method and dip coating

Removal of Cr(VI) and phenol

CuO/GR/TiO2

Hydrothermal

Water splitting

AgVO3/RGO/ Ag

Hydrothermal

Degradation of Bisphenol A

Enlarges the contact area and improved the separation efficiency of photoexcited charge carriers. RGO wide visible-light absorption range and Ni NPs as cocatalysts for capturing photoexcited electrons. The electrons transfer from TiO2 to WO3 to GO, and photogenerated holes transfer from WO3 to TiO2 improved the activity. Enhanced photocatalytic efficiency in the degradation of dyes. The addition of TiO2 and ZnO on MWCNT to promoted dye decomposition increases the photocatalytic activity. Increased light absorption intensity and the reduction of electron-hole pair recombination. RGO was used as an electron “mediator” between BiOI and Bi2S3. Improved the BET surface area and the surface hydroxyl content and induce redshift of the sample to visible light response. The synergistic effect suppressed charge recombination, improve interfacial charge transfer, visible-light adsorption and activity. Exhibited excellent light-trapping ability, absorbance in the visible light region and facilitated charge transfer.

Degradation of formaldehyde

[173]

[195]

[196] [197]

[198] [174]

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

Hydrothermal

TiO2 nanofibers/ RGO/Ag2O TiO2/RGO/Au nanoparticles

[199]

[200]

[201] 563

Continued

564

Table 17.8 Continued Preparation method

Photocatalytic applications

Highlighted properties and results

References

Hydrothermal

Water splitting

[202]

Chemical method at low temperature Dispersion

Methylene Blue degradation

Enhanced the separation efficiency of photogenerated charge carriers. RGO sheets showed efficient separation of electron-hole pairs.

Water splitting

TIO2/RGO/Ag

Via a three-step process Hydrothermal

Cu2O/RGO/ Bi2O3

In situ precipitation

Tetracycline (TC) degradation

TiO2/GR/Bi2O3

Hydrothermal

Rhodamine B degradation

CeO2/NGR/Cu

Ultrasound

Photo-reduction of CO2 to fuel

BiVO4/GO/ Bi2O3

Chemical bath deposition method Hydrothermal

Bisphenol-A (BPA) degradation

Nanocomposite CdS NPs/NGR/ Nb2O5 nanorods CdS NPs/RGO/ ZnO CdS NPs/GR/ MoS2 Cu2O/RGO/Pd

Methylene blue degradation

Photoreduction of CO2 to fuel

2D graphene plays a key role as an efficient electron mediator. Allow the harnessing of the photo-induced charge flow for efficient e-h separation. The synergetic effect of plasmonic Ag and RGO enhanced photoactivity with visiblelight. Z-scheme photocatalytic system favored the transfer of photogenerated electrons and holes toward an effective path. The heterostructures showed an efficient reduction in the recombination of electronhole pairs. NG Cu(II) complex as an artificial enzyme for the reduction of CO2 to methanol fuel was successfully fabricated. GR accelerated the interfacial electrontransfer rate improved separation of photogenerated charge carriers. The restoration of the sp2 hybridized aromatic system in RGO facilitated the movement of electrons.

[204] [205] [206]

[207]

[208]

[209]

[210]

[172]

Nanocarbon and its Composites

CuZnO/RGO/ Fe3O4 microspheres

Water splitting

[203]

Two-step hydrothermal

Water splitting

BiOBr/GR/Er

Hydrothermal

Rhodamine B degradation

CdS/GO/ TAON-Pt

Hydrothermal

Water splitting

Cu2O/RGO/gC3N4

Facile selfassemble approach Liquidexfoliation and solvothermal Hydrothermal and photodeposit Hydrothermal

Methylene blue and methyl orange degradation

Water splitting

Hydrothermal

Rhodamine B degradation

Solvothermal

Water splitting

Photoreduction

Water splitting

SnS2/RGO/ TiO2 TiO2/GR/Pd

ZnS/GR/MoS2 nanosheets Bi2WO6 nanosheets/ RGO/Ag ZnIn2S4/RGO/ MoS2 Nitrogen-doped La2Ti2O7/RGO/ Au NPs

Rhodamine B degradation

Rhodamine B degradation

The photoexcited electrons of CZTS can be readily transported to MoS2 through RGO backbone, reducing the electron-hole pair recombination. Reduced energy band gap and promoted charge separation and transmission over the hybrid photocatalyst. Altered the energy levels of the conduction and valence bands and efficiently lengthen the lifetime of the photogenerated charge carriers. The Cu2O/g-C3N4 heterojunction absorbed visible light region shifted to lower.

[211]

[212]

[213]

[187]

Reduced the recombination of electron/hole pairs and enhanced the rate of electrontransfer for the degradation of dye molecules. Higher available surface area.

[214]

Graphene serves as an excellent electron acceptor and transporter. The effect plasmonic of Ag NPs enhanced the generation and separation of photogenerated charge carriers of Bi2WO6. The photo-generated electrons and holes were suppressed efficiently. Nitrogen doping extends the light absorption range.

[215]

[188]

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

MoS2/RGO/ Cu2ZnSnS4

[216]

[217] [218]

565

Continued

566

Table 17.8 Continued Nanocomposite

Preparation method

Photocatalytic applications

Highlighted properties and results

References

Degradation of different antibiotics such as Tetracycline (TC), Oxytetracycline, Ciprofloxacin, and Doxycycline Water splitting

The high charge carrier mobility of NGQDs and the p-n junction photocatalytic systems, which greatly promoted efficient separation of charge carriers. The interfacial contact between g-C3N4/CdS accelerated the separation and transfer of photoinduced charge carriers and enhanced visible-light absorption. The transfer of conduction band electrons from rutile to anatase improved the charge separation efficiency. The formation of multiheterojunctions promotes the efficient separation of photoinduced electron-hole pairs. high electron conductivity and a low degree of hydrophobicity The synergistic effects played an important role in light absorption, charge separation and transfer, and photo-corrosion. Inhibited the photocorrosion of pure Ag3PO4

[219]

Hydrothermal

RGO g-C3N4/ CdS nanorods/ Pt

Wet-chemical

Anatase TiO2/ RGO/RutileTiO2 Flower-like Bi2O2CO3/GO/ TiO2 Ru/SrTiO3:Rh/ RGO/BiVO4 ZnO/graphene quantum dots/ Cu Ag3PO4/RGO/ BiVO4/Ag

Surfaceassembling strategy Two steps hydrothermal

Water splitting

Photoreduction

Water splitting

Spin-coating and annealing process In situ precipitation and photoreduction Liquidprecipitation

Rhodamine B (RhB) degradation

Hydrothermal

Rhodamine B degradation

g-C3N4/RGO/ anatase TiO2 g-C3N4/RGO/ Bi2MoO6

Methyl orange degradation

Tetracycline degradation

Methylene blue degradation

Improved oxygen-reduction capacity and the formation of hydroxyl radicals driven by the holes in TiO2 Graphene was used as the electron mediator in the Z-scheme system.

[220]

[221]

[222]

[223] [224]

[225]

[226]

[227]

Nanocarbon and its Composites

Quantum dotsBiOI/NGR/ MnNb2O6

Hydrothermal

Methylene blue degradation

TiO2/RGO/Au NPs

Microwaveassisted-and hydrothermal Hydrothermal

Water splitting

Methylene blue degradation

LaMnO3/RGO/ Fe3O4 SnO2/GO/TiO2

Coprecipitation

Methylene blue degradation

Solvothermal

TiO2/RGO/Pt, Pd, Ag, and Au NPs ZnWO4/RGO/ Fe3O4

Solvothermal

Congo red and methylene blue degradation Photoreduction of CO2

Microwave

Methylene blue degradation

WO3/MWCNT/ TiO ZnS/GO/CdS/Pt

Hydrolysis and impregnation Irradiationassisted

Oxalic acid degradation

CdS/RGO/gC3N4

Solvothermal

H2 generation and degradation of Atrazine

MoS2/GR/ Fe2O3

Water splitting

Enhanced photoabsorption range, adsorption capacity and the efficient separation of electron-hole pairs. Au NPs broadens the visible light response of TiO2 due to the surface plasmon resonance (SPR) effect. MoS2 and graphene components extended the light response and acted as a charge transfer medium, respectively. Enhanced the separation efficiency of electron-hole and large surface contact area. Generates more free charge carriers that induce surface chemical reactions. Enhanced utilization of visible light and efficient electron transfer in the noble metaldoped GT nanojunctions. Carrier exploitation efficiently by tolerating the photoexcited electron-hole pairs and thus encouraging oxidative degradation of the pollutants. Active composites were obtained. GO constructed a carrier transport channel between ZnS and CdS to enhance cooperative effects. RGO as a mediator played an important role in accelerating electron transfer in the Z-scheme process.

[190]

[228]

[229]

[230] [231] [232]

[233]

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

TiO2/RGO/CdS

[234] [235]

[236]

Continued 567

568

Table 17.8 Continued Preparation method

Photocatalytic applications

Highlighted properties and results

References

Eu2O3/ Mesoporous Graphene/TiO2

Hydrothermal

4-Chlorophenol degradation

[237]

CdS/GO/ZnO

Hydrothermal

Photocatalytic hydrogen generation and organic dye degradation

MoS2/RGO/ CdS

Photoreduction

Water splitting

CdS QDs/GR/ ZnIn2S4

Hydrothermal

Water splitting

ZnFe2O4/GO/ ZnO

Ultrasound

Methyl orange degradation

MoS2/RGO/ ZnO TiO2/GO/Ce

Hydrothermal

Methylene blue degradation

Sol-gel

Formaldehyde degradation

TiO2/GR/Ag NPs

Solvothermal

Paraoxon pesticide degradation

BiOI/RGO/ Bi2S3 CdS/RGO/ZnO

Electrostatic self-assembly Hydrothermal

Reduction of Cr(VI) and phenol degradation Methyl orange degradation

ZnO/RGO/TiO2

Hydrothermal

Reduction of Cr(VI)

The enhanced surface area with narrow band gap and suppressed electron-hole recombination enhanced OH radical formation. Enhanced surface area and efficient separation of photoinduced charge carriers due to the presence of GO Separation of photoexcited charges by rGO and increased absorption of visible light absorption were observed. Enhancement the ZnIn2S4 photostability, enhanced light absorption and improved separation of photogenerated carriers. The recombination of photo-generated electron-hole utilization of visible light region due to its narrow bandgap. Graphene as a support material enhanced pollutant adsorption and electron transport. The induced redshift of the sample to visible light response. Graphene due to its high electrical conductivity diminishing the recombination rate of the photogenerated pairs. The photoinduced electrons in the conduction band increased its photocatalytic activity. Enhanced photogenerated charge separation, charge transfer and adsorption of dye. Increased light absorption intensity and the reduction of electron-hole pair recombination.

Nanocomposite

[238]

[239]

[240]

[241]

[242]

[176]

[174] [243] [198]

Nanocarbon and its Composites

[199]

Precipitation

Rhodamine B degradation

CdS/RGO/UiO66 ZnO/GO/CuBTC Ce/RGO or GR/ UiO-66

Solvothermal

Water splitting

One-step solvothermal One-step solvothermal

Water splitting Nitroaromatic compounds degradation

Solvothermal

Water splitting

In situ growth and mixing Two-step hydrothermal

Water splitting

MoS2 quantum dots/GO/UiO66-NH2 Pt/RGO/UiO66-NH2 SnO2 NPs/ RGO/UiO-66

Rhodamine B degradation

GO, graphene oxide; GR, graphene; NGR, N-doped graphene; and RGO, reduce graphene oxide.

Effective interaction between RGO and RhB molecules improved the charge carrier separation and photoactivity. Improved the numbers of catalytic sites and minimize recombination of charge carriers. Hradical was encapsulated in the Cu-BTC MOF channel and stabilized. Ce was introduced as “mediator” improving the electron transfer and photoactivity in the visible region. The synergetic effect of MoS2 QDs enhancing photoactivity. Pt cocatalyst for increasing the hydrogen production. Improved RhB adsorption capacity and photocatalytic performance were observed.

[244]

[177] [178] [179]

[245]

[167] [246]

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

BiOI/RGO/AgI

569

570

Nanocarbon and its Composites

graphene oxide, graphene, or carbon nanotubes has allowed the reduction of recombination between photo-induced electron-hole pairs and expanded the photoabsorption range to the visible light region. Recently, the integration of metals or metal oxides into MOF composite materials with graphene oxide (GO), graphene (GR), or carbon nanotubes has shown an improvement in the photocatalytic performance. For instance, cadmium sulfide (CdS) is a most-promising semiconductor for photocatalytic hydrogen production. However, CdS has some drawbacks such as fast recombination of photogenerated electron-hole pairs as well as a low surface area with a small number of catalytic sites. Lin and coworkers designed an UiO-66/CdS/RGO ternary composite for the photocatalytic hydrogen production under visible light [177]. They observed in the pure CdS a deficient hydrogen production; however, when CdS NPs were dispersed into the MOF UiO-66 surface and incorporated RGO, an enhancement in the photocatalytic activity was observed. They explained their results regarding a better dispersion of CdS on UiO-66 increasing the number of catalytic sites and reaction centers, as well as RGO, minimizes the recombination of charge carriers. ZnO is another widely used semiconductor in photocatalysis due to its low cost, chemical inertness, nontoxicity, ready availability, and stability. However, ZnO is limited by a large band gap energy (3.37 eV) and a fast recombination rate of photogenerated electron-hole pairs. Shi et al. synthesized a multicomponent material based in Cu-BTC and a ZnO/graphene oxide system that was used in photocatalytic hydrogen production [178]. They demonstrated that the electrostatic interaction of Cu-BTC with ZnO/GO could encapsulate and stabilize Hradical reaction intermediates, increasing its recombination to form molecular hydrogen. Yang et al. showed the effect of doped metal ions such as Ce in the skeleton of MOF UiO-66 for the photocatalytic reduction of nitroaromatic compounds under visible light [179]. Ce ions were doped into UiO-66 (Zr) nanostructures by the solvothermal method using CeCl2 as a cerium ion precursor. In this case, Ce ions introduced in MOF as an “electron mediator” can improve the electron transfer as well as decrease the recombination of electron-hole pairs (Fig. 17.27). It is important to mention that few studies have been realized using MOF-based multicomponent materials in photocatalytic applications so far. Fig. 17.27 Possible mechanism for the photocatalytic reduction of nitrobenzene over GR/Ce-UiO(10). Reproduced with permission from Yang Z, Xu X, Liang X, Lei C, Gao L, Hao R, et al. Fabrication of Ce doped UiO-66/graphene nanocomposites with enhanced visible light driven photoactivity for reduction of nitroaromatic compounds. Appl Surf Sci 2017;420:276–85. https://doi.org/ 10.1016/j.apsusc.2017.05.158.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

17.7

571

Conclusion

A large number of nanocarbon-semiconductor (NSH) and multicomponent hybrid materials have been analyzed in terms of the preparation methods used, the photocatalytic reactions in which they have been evaluated, and a possible explanation of their behavior. The review was conducted with three types of nanocarbon: fullerenes, CNTs, and graphene while the considered semiconductors were metal oxides (e.g., TiO2, ZnO, WO3, CuxO), metal sulfides (e.g., CdS, ZnS), and MOFs, among others. Most works were devoted to obtaining active, selective, and stable metal-free photocatalytic systems, which provided, in some cases, a better photocatalytic performance by using NSH. In most cases, the hybrid materials showed a higher adsorption capacity, better UV and visible light absorption, and a higher photocatalytic activity than the bare semiconductor as well as better stability. Even though the number of publications related to the NSH applications in photocatalysis has increased exponentially in the last 5 years, works of fundamental character to understand or design its operation were scarce in this period. Five recurring explanations of the NSH improved properties were noted: (i) better charge carrier separation, (ii) reduction of the band gap value and changes in the CB position of the semiconductor, (iii) evidence of nanocarbon-semiconductor chemical interaction, (iv) charge carrier transfer between them, and (v) nanocarbon photo-sensibilization effect. In particular, graphene (i.e., graphene oxide (GO) and reduced graphene oxide (RGO) were the most nanocarbon sources used in the preparation of NSH. In fact, a few photocatalytic applications of fullerenes or CNT-TiO2 hybrids were reported in comparison with graphene-TiO2. Significant advances in the use of RGO-TiO2 were detected, mainly in photocatalytic hydrogen production and CO2 photoreduction. The most important result obtained with CNT and graphene combined with ZnO was a higher photocatalytic activity and stability and diminishing ZnO photocorrosion. Some reaction mechanisms were proposed to explain the stability of ZnO using the electron and hole transfer mechanism. It seemed that after CNT photosensitization under visible light, electrons are transferred to the ZnO CB and holes from ZnO VB to the CNT, inhibiting ZnO photocorrosion. The use of copper and tungsten oxides combined with RGO played a significant role in the selectivity control for the CO2 photocatalytic reduction while the former produces methanol and the last generates methane. It is worth noting that NC-chalcogenide (e.g., CdS) hybrids were good candidates for hydrogen production under visible light. However, considerable work remains to be done to elucidate the reaction mechanism and to control the stability under different reaction media. A remarkable hydrogen production (2641 μmol H2 g-1 h-1) was obtained with a ternary chalcogenide ZnIn2S4 deposited on RGO. Nanocarbon-MOFs hybrids have been a little-explored field, especially in the case of photocatalytic reactions of hydrogen production or reduction of CO2. According to the reported works, the MOF is activated with visible light and then easily transfers electrons to the nanocarbon favoring the oxygen reduction reaction as well as

572

Nanocarbon and its Composites

increasing its stability. Multicomponent NCS hybrids were a combination of two species (metal oxide, chalcogenide, or metal) with nanocarbon to promote electron transfer between them assisted with nanocarbon. Nevertheless, due to the complexity of the participating components and the different concentrations used for each one, much fundamental work is required to understand their photocatalytic performance.

References [1] Serp P, Machado B. Carbon (Nano)materials for catalysis. In: Serp P, Machado B, editors. Nanostructured carbon mater. catal. England: RSC Publishing; 2015. p. 1–45. https://doi.org/10.1039/9781782622567-00001. [2] Rodrı´guez-Reinoso F, Sepu´lveda-Escribano A. Carbon as catalyst support. In: Serp P, Figueiredo JL, editors. Carbon mater. catal. John Wiley & Sons, Inc.; 2008. p. 131–55. https://doi.org/10.1002/9780470403709.ch4. [3] P
erez-Mayoral E, Calvino-Casilda V, Soriano E. Metal-supported carbon-based materials: opportunities and challenges in the synthesis of valuable products. Cat Sci Technol 2016;6:1265–91. https://doi.org/10.1039/C5CY01437A. [4] Su DS, Perathoner S, Centi G. Nanocarbons for the development of advanced catalysts. Chem Rev 2013;113:5782–816. https://doi.org/10.1021/cr300367d. [5] Shearer CJ, Cherevan A, Eder D. Application of functional hybrids incorporating carbon nanotubes or graphene. In: Tanaka K, Iijima S, editors. Carbon Nanotub. Graphene. 2nd ed. Oxford: Elsevier; 2014. p. 387–433. https://doi.org/10.1016/B978-0-08-0982328.00016-4. [6] Centi G, Perathoner S. Advanced photocatalytic materials by nanocarbon hybrid materials. In: Eder D, Schl€ogl R, editors. Nanocarbon-Inorg. Hybrids. 1st ed. Berlin, Boston: De Gruyter; 2014. p. 429–54. https://doi.org/10.1515/9783110269864.429. [7] Mathur RB, Singh BP, Pande S. Carbon nanomaterials. 1st ed. New York: Taylor & Francis; 2017. [8] Wu Y, Shen Z, Yu T, editors. Two-dimensional carbon. 1st ed. New York: Taylor & Francis; 2014. [9] Su DS, Centi G. Preface to special issue on carbon materials for energy application. J Energy Chem 2013;22:i. https://doi.org/10.1016/S2095-4956(13)60021-2. [10] Kry´sa J, Pausˇova´ Sˇ, Zla´mal M, Mills A. Photoactivity assessment of TiO2 thin films using acid Orange 7 and 4-chlorophenol as model compounds. Part I: key dependencies. J Photochem Photobiol Chem 2012;250:66–71. https://doi.org/10.1016/j.jphotochem.2012.09.009. [11] Srikanth B, Goutham R, Badri Narayan R, Ramprasath A, Gopinath KP, Sankaranarayanan AR. Recent advancements in supporting materials for immobilised photocatalytic applications in waste water treatment. J Environ Manage 2017;200:60–78. https://doi.org/10.1016/j.jenvman.2017.05.063. [12] Li C, Xu Y, Tu W, Chen G, Xu R. Metal-free photocatalysts for various applications in energy conversion and environmental purification. Green Chem 2017;19:882–99. https:// doi.org/10.1039/C6GC02856J. [13] Li X, Shen R, Ma S, Chen X, Xie J. Graphene-based heterojunction photocatalysts. Appl Surf Sci 2018;430:53–107. https://doi.org/10.1016/j.apsusc.2017.08.194. [14] Perathoner S, Ampelli C, Chen S, Passalacqua R, Su D, Centi G. Photoactive materials based on semiconducting nanocarbons—a challenge opening new possibilities for photocatalysis. J Energy Chem 2017;26:207–18. https://doi.org/10.1016/j.jechem.2017.01.005.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

573

[15] Inagaki M, Kang F, Toyoda M, Konno H. Carbon materials in photocatalysis. Adv Mater Sci Eng Carbon 2014;289–311. https://doi.org/10.1016/B978-0-12-407789-8.00013-2 Boston: Butterworth-Heinemann. [16] Kuvarega AT, Mamba BB. TiO2-based photocatalysis: toward visible lightresponsive photocatalysts through doping and fabrication of carbon-based nanocomposites. Crit Rev Solid State Mater Sci 2017;42:295–346. https://doi.org/ 10.1080/10408436.2016.1211507. [17] Khalid NR, Majid A, Tahir MB, Niaz NA, Khalid S. Carbonaceous-TiO2 nanomaterials for photocatalytic degradation of pollutants: a review. Ceram Int 2017;43:14552–71. https://doi.org/10.1016/j.ceramint.2017.08.143. [18] Leary R, Westwood A. Carbonaceous nanomaterials for the enhancement of TiO2 photocatalysis. Carbon 2011;49:741–72. https://doi.org/10.1016/j.carbon.2010.10.010. [19] Apostolopoulou V, Vakros J, Kordulis C, Lycourghiotis A. Preparation and characterization of [60] fullerene nanoparticles supported on titania used as a photocatalyst. Colloids Surf A Physicochem Eng Asp 2009;349:189–94. https://doi.org/10.1016/j. colsurfa.2009.08.016. [20] Qi K, Selvaraj R, Al Fahdi T, Al-Kindy S, Kim Y, Wang G-C, et al. Enhanced photocatalytic activity of anatase-TiO2 nanoparticles by fullerene modification: a theoretical and experimental study. Appl Surf Sci 2016;387:750–8. https://doi.org/10.1016/j. apsusc.2016.06.134. [21] Yu J, Ma T, Liu G, Cheng B. Enhanced photocatalytic activity of bimodal mesoporous titania powders by C60 modification. Dalton Trans 2011;40:6635–44. https://doi.org/ 10.1039/C1DT10274E. [22] Wang S, Liu C, Dai K, Cai P, Chen H, Yang C, et al. Fullerene C70–TiO2 hybrids with enhanced photocatalytic activity under visible light irradiation. J Mater Chem A 2015;3:21090–8. https://doi.org/10.1039/C5TA03229F. [23] Long Y, Lu Y, Huang Y, Peng Y, Lu Y, Kang S-Z, et al. Effect of C60 on the photocatalytic activity of TiO2 nanorods. J Phys Chem C 2009;113:13899–905. https://doi. org/10.1021/jp902417j. [24] Xie Q, Perez-Cordero E, Echegoyen L. Electrochemical detection of C60 6- and C70 6-: enhanced stability of fullerides in solution. J Am Chem Soc 1992;114:3978–80. https://doi.org/10.1021/ja00036a056. [25] Ohsawa Y, Saji T. Electrochemical detection of C606- at low temperature. J Chem Soc Chem Commun 1992;781–2. https://doi.org/10.1039/C39920000781. [26] Kamat PV, Gevaert M, Vinodgopal K. Photochemistry on semiconductor surfaces. Visible light induced oxidation of C60 on TiO2 nanoparticles. J Phys Chem B 1997;101:4422–7. https://doi.org/10.1021/jp970047f. [27] Cheng H, Huang B, Wang P, Wang Z, Lou Z, Wang J, et al. In situ ion exchange synthesis of the novel Ag/AgBr/BiOBr hybrid with highly efficient decontamination of pollutants. Chem Commun 2011;47:7054–6. https://doi.org/10.1039/C1CC11525A. [28] Pastrana-Martı´nez LM, Morales-Torres S, Papageorgiou SK, Katsaros FK, Romanos GE, Figueiredo JL, et al. Photocatalytic behaviour of nanocarbon–TiO2 composites and immobilization into hollow fibres. Appl Catal Environ 2013;142–143:101–11. https:// doi.org/10.1016/j.apcatb.2013.04.074. [29] Cho E-C, Ciou J-H, Zheng J-H, Pan J, Hsiao Y-S, Lee K-C, et al. Fullerene C70 decorated TiO2 nanowires for visible-light-responsive photocatalyst. Appl Surf Sci 2015;355:536–46. https://doi.org/10.1016/j.apsusc.2015.07.062. [30] Zhang X, Wang Q, Zou L-H, You J-W. Facile fabrication of titanium dioxide/fullerene nanocomposite and its enhanced visible photocatalytic activity. J Colloid Interface Sci 2016;466:56–61. https://doi.org/10.1016/j.jcis.2015.12.013.

574

Nanocarbon and its Composites

[31] Justh N, Firkala T, La´szlo´ K, La´ba´r J, Szila´gyi IM. Photocatalytic C60-amorphous TiO2 composites prepared by atomic layer deposition. Appl Surf Sci 2017;419:497–502. https://doi.org/10.1016/j.apsusc.2017.04.243. [32] Park Y, Singh NJ, Kim KS, Tachikawa T, Majima T, Choi W. Fullerol–titania chargetransfer-mediated photocatalysis working under visible light. Chem A Eur J 2009;15:10843–50. https://doi.org/10.1002/chem.200901704. [33] Grandcolas M, Ye J, Miyazawa K. Titania nanotubes and fullerenes C60 assemblies and their photocatalytic activity under visible light. Ceram Int 2014;40:1297–302. https://doi. org/10.1016/j.ceramint.2013.07.009. [34] Yang M-Q, Zhang N, Xu Y-J. Synthesis of fullerene–, carbon nanotube–, and graphene– TiO2 nanocomposite photocatalysts for selective oxidation: a comparative study. ACS Appl Mater Interfaces 2013;5:1156–64. https://doi.org/10.1021/am3029798. [35] Baughman RH, Zakhidov AA, de Heer WA. Carbon nanotubes–the route toward applications. Science 2002;297:787–92. https://doi.org/10.1126/science.1060928. [36] Serp P, Corrias M, Kalck P. Carbon nanotubes and nanofibers in catalysis. Appl Catal Gen 2003;253:337–58. https://doi.org/10.1016/S0926-860X(03)00549-0. [37] Xu H, Wang J, Zhang H, Huang Y. The effects of synthesis procedures on the structure and morphology of multiwalled carbon nanotubes (MWNTs)/titania (TiO2) nanocomposites prepared by hydrothermal method. J Mater Sci 2010;45:6200–5. https://doi.org/10.1007/s10853-010-4713-z. [38] Yao Y, Li G, Ciston S, Lueptow RM, Gray KA. Photoreactive TiO2/Carbon Nanotube Composites: Synthesis and Reactivity. Environ Sci Technol 2008;42:4952–7. https:// doi.org/10.1021/es800191n. [39] Mallakpour S, Khadem E. Carbon nanotube–metal oxide nanocomposites: Fabrication, properties and applications. Chem Eng J 2016;302:344–67. https://doi.org/10.1016/j. cej.2016.05.038. [40] Silva CG, Sampaio MJ, Marques RRN, Ferreira LA, Tavares PB, Silva AMT, et al. Photocatalytic production of hydrogen from methanol and saccharides using carbon nanotube-TiO2 catalysts. Appl Catal Environ 2015;178:82–90. https://doi.org/10.1016/ j.apcatb.2014.10.032. [41] Yang HM, Park S-J. Effect of incorporation of multiwalled carbon nanotubes on photodegradation efficiency of mesoporous anatase TiO2 spheres. Mater Chem Phys 2017;186:261–70. https://doi.org/10.1016/j.matchemphys.2016.10.052. [42] Wang W, Serp P, Kalck P, Faria JL. Visible light photodegradation of phenol on MWNTTiO2 composite catalysts prepared by a modified sol–gel method. J Mol Catal Chem 2005;235:194–9. https://doi.org/10.1016/j.molcata.2005.02.027. [43] Zhang X, Cao S, Wu Z, Zhao S, Piao L. Enhanced photocatalytic activity towards degradation and H2 evolution over one dimensional TiO2@MWCNTs heterojunction. Appl Surf Sci 2017;402:360–8. https://doi.org/10.1016/j.apsusc.2017.01.096. [44] Natarajan TS, Lee JY, Bajaj HC, Jo W-K, Tayade RJ. Synthesis of multiwall carbon nanotubes/TiO2 nanotube composites with enhanced photocatalytic decomposition efficiency. Catal Today 2017;282:13–23. https://doi.org/10.1016/j.cattod.2016.03.018. [45] Park CH, Lee CM, Choi JW, Park GC, Joo J. Enhanced photocatalytic activity of porous single crystal TiO2/CNT composites by annealing process. Ceram Int 2018;44:1641–5. https://doi.org/10.1016/j.ceramint.2017.10.086. [46] Koli VB, Dhodamani AG, Delekar SD, Pawar SH. In situ sol-gel synthesis of anatase TiO2-MWCNTs nanocomposites and their photocatalytic applications. J Photochem Photobiol Chem 2017;333:40–8. https://doi.org/10.1016/j.jphotochem.2016.10.008.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

575

[47] Ahmadi M, Ramezani Motlagh H, Jaafarzadeh N, Mostoufi A, Saeedi R, Barzegar G, et al. Enhanced photocatalytic degradation of tetracycline and real pharmaceutical wastewater using MWCNT/TiO2 nano-composite. J Environ Manage 2017;186:55–63. https:// doi.org/10.1016/j.jenvman.2016.09.088. [48] R
eti B, Major Z, Szarka D, Boldizsa´r T, Horva´th E, Magrez A, et al. Influence of TiO2 phase composition on the photocatalytic activity of TiO2/MWCNT composites prepared by combined sol–gel/hydrothermal method. J Mol Catal Chem 2016;414:140–7. https:// doi.org/10.1016/j.molcata.2016.01.016. [49] Zouzelka R, Kusumawati Y, Remzova M, Rathousky J, Pauport
e T. Photocatalytic activity of porous multiwalled carbon nanotube-TiO2 composite layers for pollutant degradation. J Hazard Mater 2016;317:52–9. https://doi.org/10.1016/j.jhazmat.2016.05.056. [50] Novoselov KS, Geim AK, Morozov SV, Jiang D, Zhang Y, Dubonos SV, et al. Electric field effect in atomically thin carbon films. Science 2004;306:666–9. https://doi.org/ 10.1126/science.1102896. [51] Geim AK, Novoselov KS. The rise of graphene. Nat Mater 2007;6:183–91. https://doi. org/10.1038/nmat1849. [52] Han C, Zhang N, Xu Y-J. Structural diversity of graphene materials and their multifarious roles in heterogeneous photocatalysis. Nano Today 2016;11:351–72. https://doi.org/ 10.1016/j.nantod.2016.05.008. [53] Tan L-L, Chai S-P, Mohamed AR. Synthesis and applications of graphene-based TiO2 photocatalysts. ChemSusChem 2012;5:1868–82. https://doi.org/10.1002/cssc.201200480. [54] Park S, Ruoff RS. Chemical methods for the production of graphenes. Nat Nanotechnol 2009;4:217–24. https://doi.org/10.1038/nnano.2009.58. [55] Williams G, Seger B, Kamat PV. TiO2-graphene nanocomposites. UV-assisted photocatalytic reduction of graphene oxide. ACS Nano 2008;2:1487–91. https://doi.org/ 10.1021/nn800251f. [56] Xiang Q, Cheng B, Yu J. Graphene-based photocatalysts for solar-fuel generation. Angew Chem Int Ed 2015;54:11350–66. https://doi.org/10.1002/anie.201411096. [57] Katsukis G, Romero-Nieto C, Malig J, Ehli C, Guldi DM. Interfacing nanocarbons with organic and inorganic semiconductors: from nanocrystals/quantum dots to extended tetrathiafulvalenes. Langmuir 2012;28:11662–75. https://doi.org/10.1021/ la301152s. [58] Li Q, Guo B, Yu J, Ran J, Zhang B, Yan H, et al. Highly efficient visible-light-driven photocatalytic hydrogen production of CdS-cluster-decorated graphene nanosheets. J Am Chem Soc 2011;133:10878–84. https://doi.org/10.1021/ja2025454. [59] Mathkar A, Tozier D, Cox P, Ong P, Galande C, Balakrishnan K, et al. Controlled, stepwise reduction and band gap manipulation of graphene oxide. J Phys Chem Lett 2012;3:986–91. https://doi.org/10.1021/jz300096t. [60] Faraldos M, Bahamonde A. Environmental applications of titania-graphene photocatalysts. Catal Today 2017;285:13–28. https://doi.org/10.1016/j.cattod.2017.01.029. [61] Zhou Q, Zhong Y-H, Chen X, Wang Y, Huang X-J, Wu Y-C. Graphene-TiO2 functional nanocomposite: from synthesis to applications. J Nanosci Nanotechnol 2016;16:9327–45. https://doi.org/10.1166/jnn.2016.12454. [62] Li X, Yu J, Wageh S, Al-Ghamdi AA, Xie J. Graphene in photocatalysis: a review. Small 2016;12:6640–96. https://doi.org/10.1002/smll.201600382. [63] Ong CB, Ng LY, Mohammad AW. A review of ZnO nanoparticles as solar photocatalysts: synthesis, mechanisms and applications. Renew Sustain Energy Rev 2018;81:536–51. https://doi.org/10.1016/j.rser.2017.08.020.

576

Nanocarbon and its Composites

[64] Mohd AMA, Julkapli NM, Abd HSB. Review on ZnO hybrid photocatalyst: impact on photocatalytic activities of water pollutant degradation. Rev Inorg Chem 2016;36:77–104. https://doi.org/10.1515/revic-2015-0015. [65] Fan H, Zhao X, Yang J, Shan X, Yang L, Zhang Y, et al. ZnO–graphene composite for photocatalytic degradation of methylene blue dye. Cat Com 2012;29:29–34. https://doi. org/10.1016/j.catcom.2012.09.013. [66] Liu S, Sun H, Suvorova A, Wang S. One-pot hydrothermal synthesis of ZnO-reduced graphene oxide composites using Zn powders for enhanced photocatalysis. Chem Eng J 2013;229:533–9. https://doi.org/10.1016/j.cej.2013.06.063. [67] Zhang Y, Chen Z, Liu S, Xu Y-J. Size effect induced activity enhancement and antiphotocorrosion of reduced graphene oxide/ZnO composites for degradation of organic dyes and reduction of Cr(VI) in water. Appl Catal Environ 2013;140–141:598–607. https://doi.org/10.1016/j.apcatb.2013.04.059. [68] Dai K, Lu L, Liang C, Dai J, Zhu G, Liu Z, et al. Graphene oxide modified ZnO nanorods hybrid with high reusable photocatalytic activity under UV-LED irradiation. Mater Chem Phys 2014;143:1410–6. https://doi.org/10.1016/j.matchemphys.2013.11.055. [69] Leng Y, Wang W, Zhang L, Zabihi F, Zhao Y. Fabrication and photocatalytical enhancement of ZnO-graphene hybrid using a continuous solvothermal technique. J Supercrit Fluids 2014;91:61–7. https://doi.org/10.1016/j.supflu.2014.04.012. [70] Gayathri S, Jayabal P, Kottaisamy M, Ramakrishnan V. Synthesis of ZnO decorated graphene nanocomposite for enhanced photocatalytic properties. J Appl Phys 2014;115:173504. https://doi.org/10.1063/1.4874877. [71] Chen Y-C, Katsumata K, Chiu Y-H, Okada K, Matsushita N, Hsu Y-J. ZnO–graphene composites as practical photocatalysts for gaseous acetaldehyde degradation and electrolytic water oxidation. Appl Catal Gen 2015;490:1–9. https://doi.org/10.1016/j. apcata.2014.10.055. [72] Hossain MM, Ku B-C, Hahn JR. Synthesis of an efficient white-light photocatalyst composite of graphene and ZnO nanoparticles: application to methylene blue dye decomposition. Appl Surf Sci 2015;354:55–65. https://doi.org/10.1016/j.apsusc.2015.01.191. [73] Li W, Jiang X, Yang H, Liu Q. Solvothermal synthesis and enhanced CO2 adsorption ability of mesoporous graphene oxide-ZnO nanocomposite. Appl Surf Sci 2015;356:812–6. https://doi.org/10.1016/j.apsusc.2015.08.152. [74] Zhang L, Li N, Jiu H, Qi G, Huang Y. ZnO-reduced graphene oxide nanocomposites as efficient photocatalysts for photocatalytic reduction of CO2. Ceram Int 2015;41:6256–62. https://doi.org/10.1016/j.ceramint.2015.01.044. [75] Kavitha MK, Pillai SC, Gopinath P, John H. Hydrothermal synthesis of ZnO decorated reduced graphene oxide: understanding the mechanism of photocatalysis. J Environ Chem Eng 2015;3:1194–9. https://doi.org/10.1016/j.jece.2015.04.013. [76] Rabieh S, Nassimi K, Bagheri M. Synthesis of hierarchical ZnO–reduced graphene oxide nanocomposites with enhanced adsorption–photocatalytic performance. Mater Lett 2016;162:28–31. https://doi.org/10.1016/j.matlet.2015.09.111. [77] Song Y, Shao P, Tian J, Shi W, Gao S, Qi J, et al. One-step hydrothermal synthesis of ZnO hollow nanospheres uniformly grown on graphene for enhanced photocatalytic performance. Ceram Int 2016;42:2074–8. https://doi.org/10.1016/j.ceramint.2015.09.082. [78] Bera S, Pal M, Naskar A, Jana S. Hierarchically structured ZnO-graphene hollow microspheres towards effective reusable adsorbent for organic pollutant via photodegradation process. J Alloys Compd 2016;669:177–86. https://doi.org/10.1016/j.jallcom.2016.02.007.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

577

[79] Men X, Chen H, Chang K, Fang X, Wu C, Qin W, et al. Three-dimensional free-standing ZnO/graphene composite foam for photocurrent generation and photocatalytic activity. Appl Catal Environ 2016;187:367–74. https://doi.org/10.1016/j.apcatb.2016.01.052. [80] Zhu L, Liu Z, Xia P, Li H, Xie Y. Synthesis of hierarchical ZnO&Graphene composites with enhanced photocatalytic activity. Ceram Int 2018;44:849–56. https://doi.org/ 10.1016/j.ceramint.2017.10.009. [81] Parameshwari R, Jothivenkatachalam K, Banks CE, Jeganathan K. Acid-free cooperative self-assembly of graphene-ZnO nanocomposites and its defect mediated visible light photocatalytic activities. Phys B Condens Matter 2017;506:32–41. https://doi.org/ 10.1016/j.physb.2016.10.039. [82] Bai X, Sun C, Liu D, Luo X, Li D, Wang J, et al. Photocatalytic degradation of deoxynivalenol using graphene/ZnO hybrids in aqueous suspension. Appl Catal Environ 2017;204:11–20. https://doi.org/10.1016/j.apcatb.2016.11.010. [83] Mazarji M, Nabi-Bidhendi G, Mahmoodi NM. One-pot synthesis of a reduced graphene oxide–ZnO nanorod composite and dye decolorization modeling. J Taiwan Inst Chem Eng 2017;80:439–51. https://doi.org/10.1016/j.jtice.2017.07.038. [84] Verma S, Dutta RK. Enhanced ROS generation by ZnO-ammonia modified graphene oxide nanocomposites for photocatalytic degradation of trypan blue dye and 4-nitrophenol. J Environ Chem Eng 2017;5:4776–87. https://doi.org/10.1016/j.jece.2017.08.026. [85] Ameen S, Shaheer Akhtar M, Seo H-K, Shik SH. Advanced ZnO–graphene oxide nanohybrid and its photocatalytic applications. Mater Lett 2013;100:261–5. https:// doi.org/10.1016/j.matlet.2013.03.012. [86] Tayyebi A, Outokesh M, Tayebi M, Shafikhani A, Şeng€ or SS. ZnO quantum dotsgraphene composites: Formation mechanism and enhanced photocatalytic activity for degradation of methyl orange dye. J Alloys Compd 2016;663:738–49. https://doi.org/ 10.1016/j.jallcom.2015.12.169. [87] Kashinath L, Namratha K, Byrappa K. Microwave assisted synthesis and characterization of nanostructure zinc oxide-graphene oxide and photo degradation of brilliant blue. Mater Today Proc 2016;3:74–83. https://doi.org/10.1016/j.matpr.2016.01.123. [88] Li B, Liu T, Wang Y, Wang Z. ZnO/graphene-oxide nanocomposite with remarkably enhanced visible-light-driven photocatalytic performance. J Colloid Interface Sci 2012;377:114–21. https://doi.org/10.1016/j.jcis.2012.03.060. [89] Liu X, Pan L, Zhao Q, Lv T, Zhu G, Chen T, et al. UV-assisted photocatalytic synthesis of ZnO–reduced graphene oxide composites with enhanced photocatalytic activity in reduction of Cr(VI). Chem Eng J 2012;183:238–43. https://doi.org/10.1016/j.cej.2011.12.068. [90] Luo Q-P, Yu X-Y, Lei B-X, Chen H-Y, Kuang D-B, Su C-Y. Reduced graphene oxidehierarchical ZnO hollow sphere composites with enhanced photocurrent and photocatalytic activity. J Phys Chem C 2012;116:8111–7. https://doi.org/10.1021/jp2113329. [91] Peng Y, Ji J, Chen D. Ultrasound assisted synthesis of ZnO/reduced graphene oxide composites with enhanced photocatalytic activity and anti-photocorrosion. Appl Surf Sci 2015;356:762–8. https://doi.org/10.1016/j.apsusc.2015.08.070. [92] Cai R, Wu J, Sun L, Liu Y, Fang T, Zhu S, et al. 3D graphene/ZnO composite with enhanced photocatalytic activity. Mater Des 2016;90:839–44. https://doi.org/10.1016/ j.matdes.2015.11.020. [93] Beura R, Thangadurai P. Structural, optical and photocatalytic properties of grapheneZnO nanocomposites for varied compositions. J Phys Chem Solid 2017;102:168–77. https://doi.org/10.1016/j.jpcs.2016.11.024.

578

Nanocarbon and its Composites

[94] Chen D, Wang D, Ge Q, Ping G, Fan M, Qin L, et al. Graphene-wrapped ZnO nanospheres as a photocatalyst for high performance photocatalysis. Thin Solid Films 2015;574:1–9. https://doi.org/10.1016/j.tsf.2014.11.051. [95] Fu D, Han G, Chang Y, Dong J. The synthesis and properties of ZnO–graphene nano hybrid for photodegradation of organic pollutant in water. Mater Chem Phys 2012;132:673–81. https://doi.org/10.1016/j.matchemphys.2011.11.085. [96] Sushma C, Kumar SG. Advancements in the zinc oxide nanomaterials for efficient photocatalysis. Chem Pap 2017;71:2023–42. https://doi.org/10.1007/s11696-017-0217-5. [97] An S, Joshi BN, Lee MW, Kim NY, Yoon SS. Electrospun graphene-ZnO nanofiber mats for photocatalysis applications. Appl Surf Sci 2014;294:24–8. https://doi.org/10.1016/j. apsusc.2013.12.159. [98] Hussin F, Lintang HO, Lee SL, Yuliati L. Photocatalytic synthesis of reduced graphene oxide-zinc oxide: effects of light intensity and exposure time. J Photochem Photobiol Chem 2017;340:128–35. https://doi.org/10.1016/j.jphotochem.2017.03.016. [99] Wei A, Xiong L, Sun L, Liu Y, Li W, Lai W, et al. One-step electrochemical synthesis of a graphene–ZnO hybrid for improved photocatalytic activity. Mater Res Bull 2013;48:2855–60. https://doi.org/10.1016/j.materresbull.2013.04.012. [100] Haldorai Y, Shim J-J. Supercritical fluid mediated synthesis of highly exfoliated graphene/ZnO composite for photocatalytic hydrogen production. Mater Lett 2014;133:24–7. https://doi.org/10.1016/j.matlet.2014.06.150. [101] Melchionna M, Prato M, Fornasiero P. Mix and match metal oxides and nanocarbons for new photocatalytic frontiers. Catal Today 2016;277:202–13. https://doi.org/10.1016/j. cattod.2016.04.024. [102] Dai K, Dawson G, Yang S, Chen Z, Lu L. Large scale preparing carbon nanotube/zinc oxide hybrid and its application for highly reusable photocatalyst. Chem Eng J 2012;191:571–8. https://doi.org/10.1016/j.cej.2012.03.008. [103] Ahmad M, Ahmed E, Hong ZL, Ahmed W, Elhissi A, Khalid NR. Photocatalytic, sonocatalytic and sonophotocatalytic degradation of Rhodamine B using ZnO/CNTs composites photocatalysts. Ultrason Sonochem 2014;21:761–73. https://doi.org/10.1016/ j.ultsonch.2013.08.014. [104] Chaudhary D, Singh S, Vankar VD, Khare N. ZnO nanoparticles decorated multiwalled carbon nanotubes for enhanced photocatalytic and photoelectrochemical water splitting. J Photochem Photobiol Chem 2018;351:154–61. https://doi.org/10.1016/j.jphotochem. 2017.10.018. [105] Yang L, Chu D, Wang L, Wu X, Luo J. Synthesis and photocatalytic activity of chrysanthemum-like Cu2O/carbon nanotubes nanocomposites. Ceram Int 2016;42:2502–9. https://doi.org/10.1016/j.ceramint.2015.10.051. [106] Yusoff N, Huang NM, Muhamad MR, Kumar SV, Lim HN, Harrison I. Hydrothermal synthesis of CuO/functionalized graphene nanocomposites for dye degradation. Mater Lett 2013;93:393–6. https://doi.org/10.1016/j.matlet.2012.10.015. [107] Sarkar C, Dolui SK. Synthesis of copper oxide/reduced graphene oxide nanocomposite and its enhanced catalytic activity towards reduction of 4-nitrophenol. RSC Adv 2015;5:60763–9. https://doi.org/10.1039/C5RA10551J. [108] Cheng L, Wang Y, Huang D, Nguyen T, Jiang Y, Yu H, et al. Facile synthesis of sizetunable CuO/graphene composites and their high photocatalytic performance. Mater Res Bull 2015;61:409–14. https://doi.org/10.1016/j.materresbull.2014.10.036. [109] Zhang D, Hu B, Guan D, Luo Z. Essential roles of defects in pure graphene/Cu2O photocatalyst. Cat Com 2016;76:7–12. https://doi.org/10.1016/j.catcom.2015.12.013.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

579

[110] Zhang W, Ma Y, Yang Z, Tang X, Li X, He G, et al. Analysis of synergistic effect between graphene and octahedral cuprous oxide in cuprous oxide-graphene composites and their photocatalytic application. J Alloys Compd 2017;712:704–13. https://doi.org/ 10.1016/j.jallcom.2017.04.095. [111] Huang H, Zhang J, Jiang L, Zang Z. Preparation of cubic Cu2O nanoparticles wrapped by reduced graphene oxide for the efficient removal of rhodamine B. J Alloys Compd 2017;718:112–5. https://doi.org/10.1016/j.jallcom.2017.05.132. [112] Xu H, Li X, Kang S, Qin L, Li G, Mu J. Noble metal-free cuprous oxide/reduced graphene oxide for enhanced photocatalytic hydrogen evolution from water reduction. Int J Hydrogen Energy 2014;39:11578–82. https://doi.org/10.1016/j.ijhydene.2014.05.156. [113] Mateo D, Esteve-Adell I, Albero J, Primo A, Garcı´a H. Oriented 2.0.0 Cu2O nanoplatelets supported on few-layers graphene as efficient visible light photocatalyst for overall water splitting. Appl Catal Environ 2017;201:582–90. https://doi.org/ 10.1016/j.apcatb.2016.08.033. [114] Gusain R, Kumar P, Sharma OP, Jain SL, Khatri OP. Reduced graphene oxide–CuO nanocomposites for photocatalytic conversion of CO2into methanol under visible light irradiation. Appl Catal Environ 2016;181:352–62. https://doi.org/10.1016/j. apcatb.2015.08.012. [115] Wang P-Q, Bai Y, Luo P-Y, Liu J-Y. Graphene–WO3 nanobelt composite: elevated conduction band toward photocatalytic reduction of CO2 into hydrocarbon fuels. Cat Com 2013;38:82–5. https://doi.org/10.1016/j.catcom.2013.04.020. [116] Tian L, Ye L, Liu J, Zan L. Solvothermal synthesis of CNTs–WO3 hybrid nanostructures with high photocatalytic activity under visible light. Cat Com 2012;17:99–103. https:// doi.org/10.1016/j.catcom.2011.10.023. [117] Fu L, Xia T, Zheng Y, Yang J, Wang A, Wang Z. Preparation of WO3-reduced graphene oxide nanocomposites with enhanced photocatalytic property. Ceram Int 2015;41:5903–8. https://doi.org/10.1016/j.ceramint.2015.01.022. [118] Li Y, Tang Z, Zhang J, Zhang Z. Reduced graphene oxide three-dimensionally wrapped WO3 hierarchical nanostructures as high-performance solar photocatalytic materials. Appl Catal Gen 2016;522:90–100. https://doi.org/10.1016/j.apcata.2016.04.034. [119] Prabhu S, Manikumar S, Cindrella L, Kwon OJ. Charge transfer and intrinsic electronic properties of rGO-WO3 nanostructures for efficient photoelectrochemical and photocatalytic applications. Mater Sci Semicond Process 2018;74:136–46. https://doi.org/ 10.1016/j.mssp.2017.10.041. [120] Mi Q, Chen D, Hu J, Huang Z, Li J. Nitrogen-doped graphene/CdS hollow spheres nanocomposite with enhanced photocatalytic performance. Chin J Catal 2013;34:2138–45. https://doi.org/10.1016/S1872-2067(12)60641-X. [121] Gao Z, Liu N, Wu D, Tao W, Xu F, Jiang K. Graphene–CdS composite, synthesis and enhanced photocatalytic activity. Appl Surf Sci 2012;258:2473–8. https://doi.org/ 10.1016/j.apsusc.2011.10.075. [122] Wang X, Tian H, Yang Y, Wang H, Wang S, Zheng W, et al. Reduced graphene oxide/ CdS for efficiently photocatalystic degradation of methylene blue. J Alloys Compd 2012;524:5–12. https://doi.org/10.1016/j.jallcom.2012.02.058. [123] Kaveri S, Thirugnanam L, Dutta M, Ramasamy J, Fukata N. Thiourea assisted one-pot easy synthesis of CdS/rGO composite by the wet chemical method: Structural, optical, and photocatalytic properties. Ceram Int 2013;39:9207–14. https://doi.org/10.1016/j. ceramint.2013.05.025.

580

Nanocarbon and its Composites

[124] Liu F, Shao X, Wang J, Yang S, Li H, Meng X, et al. Solvothermal synthesis of graphene– CdS nanocomposites for highly efficient visible-light photocatalyst. J Alloys Compd 2013;551:327–32. https://doi.org/10.1016/j.jallcom.2012.10.037. [125] Kumar S, Ojha AK. In-situ synthesis of reduced graphene oxide decorated with highly dispersed ferromagnetic CdS nanoparticles for enhanced photocatalytic activity under UV irradiation. Mater Chem Phys 2016;171:126–36. https://doi.org/10.1016/j. matchemphys.2015.12.008. [126] Khan ME, Khan MM, Cho MH. CdS-graphene nanocomposite for efficient visible-lightdriven photocatalytic and photoelectrochemical applications. J Colloid Interface Sci 2016;482:221–32. https://doi.org/10.1016/j.jcis.2016.07.070. [127] Gao P, Liu J, Sun DD, Ng W. Graphene oxide–CdS composite with high photocatalytic degradation and disinfection activities under visible light irradiation. J Hazard Mater 2013;250–251:412–20. https://doi.org/10.1016/j.jhazmat.2013.02.003. [128] Liu J, Pu X, Zhang D, Seo HJ, Du K, Cai P. Combustion synthesis of CdS/reduced graphene oxide composites and their photocatalytic properties. Mater Res Bull 2014;57:29–34. https://doi.org/10.1016/j.materresbull.2014.05.027. [129] Liu H, Lv T, Wu X, Zhu C, Zhu Z. Preparation and enhanced photocatalytic activity of CdS@RGO core–shell structural microspheres. Appl Surf Sci 2014;305:242–6. https:// doi.org/10.1016/j.apsusc.2014.03.045. [130] Fu X, Zhang Y, Cao P, Ma H, Liu P, He L, et al. Radiation synthesis of CdS/reduced graphene oxide nanocomposites for visible-light-driven photocatalytic degradation of organic contaminant. Radiat Phys Chem 2016;123:79–86. https://doi.org/10.1016/j. radphyschem.2016.02.016. [131] Singh A, Sinha ASK. Active CdS/rGO photocatalyst by a high temperature gas-solid reaction for hydrogen production by splitting of water. Appl Surf Sci 2018;430:184–97. https:// doi.org/10.1016/j.apsusc.2017.02.214. [132] Cai Q, Hu Z, Zhang Q, Li B, Shen Z. Fullerene (C60)/CdS nanocomposite with enhanced photocatalytic activity and stability. Appl Surf Sci 2017;403:151–8. https://doi.org/ 10.1016/j.apsusc.2017.01.135. [133] Wang X, Liu M, Chen Q, Zhang K, Chen J, Wang M, et al. Synthesis of CdS/CNTs photocatalysts and study of hydrogen production by photocatalytic water splitting. Int J Hydrogen Energy 2013;38:13091–6. https://doi.org/10.1016/j.ijhydene.2013.03.016. [134] Shi J, Zhou X, Liu Y, Su Q, Zhang J, Du G. Sonochemical synthesis of CuS/reduced graphene oxide nanocomposites with enhanced absorption and photocatalytic performance. Mater Lett 2014;126:220–3. https://doi.org/10.1016/j.matlet.2014.04.051. [135] Wang Y, Zhang L, Jiu H, Li N, Sun Y. Depositing of CuS nanocrystals upon the graphene scaffold and their photocatalytic activities. Appl Surf Sci 2014;303:54–60. https://doi. org/10.1016/j.apsusc.2014.02.058. [136] Hu X-S, Shen Y, Zhang Y-T, Nie J-J. Preparation of flower-like CuS/reduced graphene oxide(RGO) photocatalysts for enhanced photocatalytic activity. J Phys Chem Solid 2017;103:201–8. https://doi.org/10.1016/j.jpcs.2016.12.021. [137] Borthakur P, Boruah PK, Darabdhara G, Sengupta P, Das MR, Boronin AI, et al. Microwave assisted synthesis of CuS-reduced graphene oxide nanocomposite with efficient photocatalytic activity towards azo dye degradation. J Environ Chem Eng 2016;4:4600–11. https://doi.org/10.1016/j.jece.2016.10.023. [138] Chen Y, Tian G, Mao G, Li R, Xiao Y, Han T. Facile synthesis of well-dispersed Bi2S3 nanoparticles on reduced graphene oxide and enhanced photocatalytic activity. Appl Surf Sci 2016;378:231–8. https://doi.org/10.1016/j.apsusc.2016.03.194.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

581

[139] Vadivel S, Kamalakannan VP, Keerthi, Balasubramanian N. d-Pencillamine assisted microwave synthesis of Bi2S3 microflowers/RGO composites for photocatalytic degradation—a facile green approach. Ceram Int 2014;40:14051–60. https://doi.org/ 10.1016/j.ceramint.2014.05.133. [140] An X, Yu JC, Wang F, Li C, Li Y. One-pot synthesis of In2S3 nanosheets/graphene composites with enhanced visible-light photocatalytic activity. Appl Catal Environ 2013;129:80–8. https://doi.org/10.1016/j.apcatb.2012.09.008. [141] Dashairya L, Sharma M, Basu S, Saha P. Enhanced dye degradation using hydrothermally synthesized nanostructured Sb2S3/rGO under visible light irradiation. J Alloys Compd 2018;735:234–45. https://doi.org/10.1016/j.jallcom.2017.11.063. [142] Chen J, Zhang H, Liu P, Li Y, Liu X, Li G, et al. Cross-linked ZnIn2S4/rGO composite photocatalyst for sunlight-driven photocatalytic degradation of 4-nitrophenol. Appl Catal Environ 2015;168–169:266–73. https://doi.org/10.1016/j.apcatb.2014.12.048. [143] Xia Y, Li Q, Lv K, Tang D, Li M. Superiority of graphene over carbon analogs for enhanced photocatalytic H2-production activity of ZnIn2S4. Appl Catal Environ 2017;206:344–52. https://doi.org/10.1016/j.apcatb.2017.01.060. [144] Yao Z, Wang L, Zhang Y, Yu Z, Jiang Z. Carbon nanotube modified Zn0.83Cd0.17S nanocomposite photocatalyst and its hydrogen production under visible-light. Int J Hydrogen Energy 2014;39:15380–6. https://doi.org/10.1016/j.ijhydene.2014.07.164. [145] Wang X, Tian H, Zheng W, Liu Y. Visible photocatalytic activity enhancement of Zn0.8Cd0.2S by hybridization of reduced graphene oxide. Mater Lett 2013;109:100–3. https://doi.org/10.1016/j.matlet.2013.07.065. [146] Shen J, Huang W, Li N, Ye M. Highly efficient degradation of dyes by reduced graphene oxide–ZnCdS supramolecular photocatalyst under visible light. Ceram Int 2015;41:761–7. https://doi.org/10.1016/j.ceramint.2014.08.135. [147] Zhou “Joe” H-C, Kitagawa S. Metal–organic frameworks (MOFs). Chem Soc Rev 2014;43:5415–8. https://doi.org/10.1039/C4CS90059F. [148] Furukawa H, Ko N, Go YB, Aratani N, Choi SB, Choi E, et al. Ultrahigh porosity in metalorganic frameworks. Science 2010;329:424–8. https://doi.org/10.1126/science.1192160. [149] Li B, Wen H-M, Cui Y, Zhou W, Qian G, Chen B. Emerging multifunctional metal– organic framework materials. Adv Mater 2016;28:8819–60. https://doi.org/10.1002/ adma.201601133. [150] Zhao Y, Song Z, Li X, Sun Q, Cheng N, Lawes S, et al. Metal organic frameworks for energy storage and conversion. Energy Storage Mater 2016;2:35–62. https://doi.org/ 10.1016/j.ensm.2015.11.005. [151] Wang H, Zhu Q-L, Zou R, Xu Q. Metal-organic frameworks for energy applications. Chem 2017;2:52–80. https://doi.org/10.1016/j.chempr.2016.12.002. [152] Silva CG, Corma A, Garcı´a H. Metal–organic frameworks as semiconductors. J Mater Chem 2010;20:3141–56. https://doi.org/10.1039/B924937K. [153] Zhang H, Liu G, Shi L, Liu H, Wang T, Ye J. Engineering coordination polymers for photocatalysis. Nano Energy 2016;22:149–68. https://doi.org/10.1016/j.nanoen.2016.01.029. [154] Fang Y, Ma Y, Zheng M, Yang P, Asiri AM, Wang X. Metal–organic frameworks for solar energy conversion by photoredox catalysis. Coord Chem Rev 2017;https://doi. org/10.1016/j.ccr.2017.09.013. [155] Wang J-L, Wang C, Lin W. Metal–organic frameworks for light harvesting and photocatalysis. ACS Catal 2012;2:2630–40. https://doi.org/10.1021/cs3005874. [156] Kuc A, Enyashin A, Seifert G. Metal  organic frameworks: structural, energetic, electronic, and mechanical properties. J Phys Chem B 2007;111:8179–86. https://doi.org/ 10.1021/jp072085x.

582

Nanocarbon and its Composites

[157] Zhang J-P, Chen X-M. Metal–organic frameworks: from design to materials. In: Met.Org. Framew. Photonics Appl. Berlin, Heidelberg: Springer; 2013. p. 1–26. https:// doi.org/10.1007/430_2013_100. [158] Shen L, Liang S, Wu W, Liang R, Wu L. Multifunctional NH2-mediated zirconium metal–organic framework as an efficient visible-light-driven photocatalyst for selective oxidation of alcohols and reduction of aqueous Cr(VI). Dalton Trans 2013;42:13649–57. https://doi.org/10.1039/C3DT51479J. [159] Shi L, Wang T, Zhang H, Chang K, Meng X, Liu H, et al. An amine-functionalized iron(III) metal–organic framework as efficient visible-light photocatalyst for Cr(VI) reduction. Adv Sci 2015;2:1500006. https://doi.org/10.1002/advs.201500006. [160] Liang R, Shen L, Jing F, Wu W, Qin N, Lin R, et al. NH2-mediated indium metal–organic framework as a novel visible-light-driven photocatalyst for reduction of the aqueous Cr(VI). Appl Catal Environ 2015;162:245–51. https://doi.org/10.1016/j.apcatb. 2014.06.049. [161] Zhu Q-L, Xu Q. Metal–organic framework composites. Chem Soc Rev 2014;43:5468–512. https://doi.org/10.1039/C3CS60472A. [162] Krishna R. Describing the diffusion of guest molecules inside porous structures. J Phys Chem C 2009;113:19756–81. https://doi.org/10.1021/jp906879d. [163] Zhang Y, Li G, Lu H, Lv Q, Sun Z. Synthesis, characterization and photocatalytic properties of MIL-53(Fe)–graphene hybrid materials. RSC Adv 2014;4:7594–600. https:// doi.org/10.1039/C3RA46706F. [164] Pi Y, Li X, Xia Q, Wu J, Li Z, Li Y, et al. Formation of willow leaf-like structures composed of NH 2 -MIL68(In) on a multifunctional multiwalled carbon nanotube backbone for enhanced photocatalytic reduction of Cr(VI). Nano Res 2017;10:3543–56. https://doi. org/10.1007/s12274-017-1565-8. [165] Huang L, Liu B. Synthesis of a novel and stable reduced graphene oxide/MOF hybrid nanocomposite and photocatalytic performance for the degradation of dyes. RSC Adv 2016;6:17873–9. https://doi.org/10.1039/C5RA25689E. [166] Ong W-J, Tan L-L, Ng YH, Yong S-T, Chai S-P. Graphitic carbon nitride (g-C3N4)-based photocatalysts for artificial photosynthesis and environmental remediation: are we a step closer to achieving sustainability? Chem Rev 2016;116:7159–329. https://doi.org/10.1021/ acs.chemrev.6b00075. [167] Wang Y, Yu Y, Li R, Liu H, Zhang W, Ling L, et al. Hydrogen production with ultrahigh efficiency under visible light by graphene well-wrapped UiO-66-NH2 octahedrons. J Mater Chem A 2017;5:20136–40. https://doi.org/10.1039/C7TA06341E. [168] Yang SJ, Im JH, Kim T, Lee K, Park CR. MOF-derived ZnO and ZnO@C composites with high photocatalytic activity and adsorption capacity. J Hazard Mater 2011;186:376–82. https://doi.org/10.1016/j.jhazmat.2010.11.019. [169] Zhang H, Wang T, Wang J, Liu H, Dao TD, Li M, et al. Surface-plasmon-enhanced photodriven CO2 reduction catalyzed by metal–organic-framework-derived iron nanoparticles encapsulated by ultrathin carbon layers. Adv Mater 2016;28:3703–10. https://doi.org/ 10.1002/adma.201505187. [170] Zhang M, Huang Y-L, Wang J-W, Lu T-B. A facile method for the synthesis of a porous cobalt oxide–carbon hybrid as a highly efficient water oxidation catalyst. J Mater Chem A 2016;4:1819–27. https://doi.org/10.1039/C5TA07813J. [171] Han W, Ren L, Qi X, Liu Y, Wei X, Huang Z, et al. Synthesis of CdS/ZnO/graphene composite with high-efficiency photoelectrochemical activities under solar radiation. Appl Surf Sci 2014;299:12–8. https://doi.org/10.1016/j.apsusc.2014.01.170.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

583

[172] Kumar P, Joshi C, Barras A, Sieber B, Addad A, Boussekey L, et al. Core–shell structured reduced graphene oxide wrapped magnetically separable rGO@CuZnO@Fe3O4 microspheres as superior photocatalyst for CO2 reduction under visible light. Appl Catal Environ 2017;205:654–65. https://doi.org/10.1016/j.apcatb.2016.11.060. [173] Chen F, Zhang L, Wang X, Zhang R. Noble-metal-free NiO@Ni-ZnO/reduced graphene oxide/CdS heterostructure for efficient photocatalytic hydrogen generation. Appl Surf Sci 2017;422:962–9. https://doi.org/10.1016/j.apsusc.2017.05.214. [174] Chen A, Bian Z, Xu J, Xin X, Wang H. Simultaneous removal of Cr(VI) and phenol contaminants using Z-scheme bismuth oxyiodide/reduced graphene oxide/bismuth sulfide system under visible-light irradiation. Chemosphere 2017;188:659–66. https://doi.org/ 10.1016/j.chemosphere.2017.09.002. [175] Kumar SG, Rao KSRK. Comparison of modification strategies towards enhanced charge carrier separation and photocatalytic degradation activity of metal oxide semiconductors (TiO2, WO3 and ZnO). Appl Surf Sci 2017;391:124–48. https://doi.org/10.1016/j. apsusc.2016.07.081. [176] Keihan AH, Hosseinzadeh R, Farhadian M, Kooshki H, Hosseinzadeh G. Solvothermal preparation of Ag nanoparticle and graphene coloaded TiO2 for the photocatalytic degradation of paraoxon pesticide under visible light irradiation. RSC Adv 2016;6:83673–87. https://doi.org/10.1039/C6RA19478H. [177] Lin R, Shen L, Ren Z, Wu W, Tan Y, Fu H, et al. Enhanced photocatalytic hydrogen production activity via dual modification of MOF and reduced graphene oxide on CdS. Chem Commun 2014;50:8533–5. https://doi.org/10.1039/C4CC01776E. [178] Shi X, Zhang J, Cui G, Deng N, Wang W, Wang Q, et al. Photocatalytic H2 evolution improvement for H free-radical stabilization by electrostatic interaction of a Cu-BTC MOF with ZnO/GO. Nano Res 2018;11:979–87. https://doi.org/10.1007/s12274-0171710-4. [179] Yang Z, Xu X, Liang X, Lei C, Gao L, Hao R, et al. Fabrication of Ce doped UiO-66/ graphene nanocomposites with enhanced visible light driven photoactivity for reduction of nitroaromatic compounds. Appl Surf Sci 2017;420:276–85. https://doi.org/10.1016/j. apsusc.2017.05.158. [180] Suresh M, Sivasamy A. Bismuth oxide nanoparticles decorated graphene layers for the degradation of methylene blue dye under visible light irradiations and antimicrobial activities. J Environ Chem Eng 2017;https://doi.org/10.1016/j.jece.2017.01.049. [181] Yu B, Zheng B, Wang X, Qi F, He J, Zhang W, et al. Enhanced photocatalytic properties of graphene modified few-layered WSe2 nanosheets. Appl Surf Sci 2017;400:420–5. https://doi.org/10.1016/j.apsusc.2016.12.015. [182] Shen L, Huang L, Liang S, Liang R, Qin N, Wu L. Electrostatically derived self-assembly of NH2-mediated zirconium MOFs with graphene for photocatalytic reduction of Cr(VI). RSC Adv 2013;4:2546–9. https://doi.org/10.1039/C3RA45848B. [183] Liu N, Huang W, Zhang X, Tang L, Wang L, Wang Y, et al. Ultrathin graphene oxide encapsulated in uniform MIL-88A(Fe) for enhanced visible light-driven photodegradation of RhB. Appl Catal Environ 2018;221:119–28. https://doi.org/10.1016/j.apcatb.2017.09.020. [184] Nuengmatcha P, Chanthai S, Mahachai R, Oh W-C. Visible light-driven photocatalytic degradation of rhodamine B and industrial dyes (texbrite BAC-L and texbrite NFW-L) by ZnO-graphene-TiO2 composite. J Environ Chem Eng 2016;4:2170–7. https://doi.org/ 10.1016/j.jece.2016.03.045. [185] Almeida BM, Melo Jr. MA, Bettini J, Benedetti JE, Nogueira AF. A novel nanocomposite based on TiO2/Cu2O/reduced graphene oxide with enhanced solar-light-driven

584

[186]

[187]

[188]

[189]

[190]

[191]

[192]

[193]

[194]

[195]

[196]

[197]

[198]

[199]

Nanocarbon and its Composites

photocatalytic activity. Appl Surf Sci 2015;324:419–31. https://doi.org/10.1016/j. apsusc.2014.10.105. Zhang L, Li H, Liu Y, Tian Z, Yang B, Sun Z, et al. Adsorption-photocatalytic degradation of methyl orange over a facile one-step hydrothermally synthesized TiO2/ ZnO–NH2–RGO nanocomposite. RSC Adv 2014;4:48703–11. https://doi.org/10.1039/ C4RA09227A. Yan X, Xu R, Guo J, Cai X, Chen D, Huang L, et al. Enhanced photocatalytic activity of Cu2O/g-C3N4 heterojunction coupled with reduced graphene oxide three-dimensional aerogel photocatalysis. Mater Res Bull 2017;96:18–27. https://doi.org/10.1016/j. materresbull.2016.12.009. Safajou H, Khojasteh H, Salavati-Niasari M, Mortazavi-Derazkola S. Enhanced photocatalytic degradation of dyes over graphene/Pd/TiO2 nanocomposites: TiO2 nanowires versus TiO2 nanoparticles. J Colloid Interface Sci 2017;498:423–32. https://doi.org/ 10.1016/j.jcis.2017.03.078. Huang J, Fu K, Deng X, Yao N, Wei M. Fabrication of TiO2 Nanosheet Aarrays/ Graphene/Cu2O Composite Structure for Enhanced Photocatalytic Activities. Nanoscale Res Lett 2017;12:310. https://doi.org/10.1186/s11671-017-2088-7. Tian Z, Yu N, Cheng Y, Wang Z, Chen Z, Zhang L. Hydrothermal synthesis of graphene/ TiO2/CdS nanocomposites as efficient visible-light-driven photocatalysts. Mater Lett 2017;194:172–5. https://doi.org/10.1016/j.matlet.2017.02.048. Liu X, Pan L, Lv T, Sun Z. Investigation of photocatalytic activities over ZnO–TiO2– reduced graphene oxide composites synthesized via microwave-assisted reaction. J Colloid Interface Sci 2013;394:441–4. https://doi.org/10.1016/j.jcis.2012.11.047. Kumar DP, Hong S, Reddy DA, Kim TK. Ultrathin MoS2 layers anchored exfoliated reduced graphene oxide nanosheet hybrid as a highly efficient cocatalyst for CdS nanorods towards enhanced photocatalytic hydrogen production. Appl Catal Environ 2017;212:7–14. https://doi.org/10.1016/j.apcatb.2017.04.065. Zhou Y, Wang Y, OuYang X, Liu L, Zhu W. TiO2 nanofibers coated with rGO and Ag2O for promoting visible light photocatalytic performance. Semicond Sci Technol 2017;32:035009 https://doi.org/10.1088/1361-6641/aa5246. Li X, Zheng S, Zhang C, Hu C, Chen F, Sun Y, et al. Synergistic promotion of photocatalytic performance by core@shell structured TiO2/Au@rGO ternary photocatalyst. Mol Catal 2017;438:55–65. https://doi.org/10.1016/j.mcat.2017.05.016. Hao X, Li M, Zhang L, Wang K, Liu C. Photocatalyst TiO2/WO3/GO nano-composite with high efficient photocatalytic performance for BPA degradation under visible light and solar light illumination. J Ind Eng Chem 2017;55:140–8. https://doi.org/10.1016/j. jiec.2017.06.038. Wang L, Wen M, Wang W, Momuinou N, Wang Z, Li S. Photocatalytic degradation of organic pollutants using rGO supported TiO2-CdS composite under visible light irradiation. J Alloys Compd 2016;683:318–28. https://doi.org/10.1016/j.jallcom.2016.05.111. Da Dalt S, Alves AK, Bergmann CP, Da Dalt S, Alves AK, Bergmann CP. Preparation and Performance of TiO2-ZnO/CNT Hetero-Nanostructures Applied to Photodegradation of Organic Dye. Mater Res 2016;19:1372–5. https://doi.org/10.1590/1980-5373mr-2016-0036. Johra FT, Jung W-G. RGO–TiO2–ZnO composites: synthesis, characterization, and application to photocatalysis. Appl Catal Gen 2015;491:52–7. https://doi.org/10.1016/ j.apcata.2014.11.036. Li J, Zhang Q, Lai ACK, Zeng L. Study on photocatalytic performance of cerium– graphene oxide–titanium dioxide composite film for formaldehyde removal. Phys Status Solidi A 2016;213:3157–64. https://doi.org/10.1002/pssa.201600261.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

585

[200] Wang B, Sun Q, Liu S, Li Y. Synergetic catalysis of CuO and graphene additives on TiO2 for photocatalytic water splitting. Int J Hydrogen Energy 2013;38:7232–40. https://doi. org/10.1016/j.ijhydene.2013.04.038. [201] Zhao W, Li J, Wei Z bo, Wang S, He H, Sun C, et al.. Fabrication of a ternary plasmonic photocatalyst of Ag/AgVO3/RGO and its excellent visible-light photocatalytic activity. Appl Catal Environ 2015;179:9–20. https://doi.org/10.1016/j.apcatb.2015.05.002. [202] Yue Z, Liu A, Zhang C, Huang J, Zhu M, Du Y, et al. Noble-metal-free hetero-structural CdS/Nb2O5/N-doped-graphene ternary photocatalytic system as visible-light-driven photocatalyst for hydrogen evolution. Appl Catal Environ 2017;201:202–10. https:// doi.org/10.1016/j.apcatb.2016.08.028. [203] Pawar RC, Lee CS. Single-step sensitization of reduced graphene oxide sheets and CdS nanoparticles on ZnO nanorods as visible-light photocatalysts. Appl Catal Environ 2014;144:57–65. https://doi.org/10.1016/j.apcatb.2013.06.022. [204] Jia T, Kolpin A, Ma C, Chan RC-T, Kwok W-M, Tsang SCE. A graphene dispersed CdS– MoS2 nanocrystal ensemble for cooperative photocatalytic hydrogen production from water. Chem Commun 2014;50:1185–8. https://doi.org/10.1039/C3CC47301E. [205] Bai S, Ge J, Wang L, Gong M, Deng M, Kong Q, et al. A unique semiconductor–metal– graphene stack design to harness charge flow for photocatalysis. Adv Mater 2014;26:5689–95. https://doi.org/10.1002/adma.201401817. [206] Vasilaki E, Georgaki I, Vernardou D, Vamvakaki M, Katsarakis N. Ag-loaded TiO2/ reduced graphene oxide nanocomposites for enhanced visible-light photocatalytic activity. Appl Surf Sci 2015;353:865–72. https://doi.org/10.1016/j.apsusc.2015.07.056. [207] Shen H, Wang J, Jiang J, Luo B, Mao B, Shi W. All-solid-state Z-scheme system of RGOCu2O/Bi2O3 for tetracycline degradation under visible-light irradiation. Chem Eng J 2017;313:508–17. https://doi.org/10.1016/j.cej.2016.11.161. [208] Hou J, Yang C, Wang Z, Jiao S, Zhu H. Bi2O3 quantum dots decorated anatase TiO2 nanocrystals with exposed {001} facets on graphene sheets for enhanced visible-light photocatalytic performance. Appl Catal Environ 2013;129:333–41. https://doi.org/ 10.1016/j.apcatb.2012.09.009. [209] Liu S-Q, Zhou S-S, Chen Z-G, Liu C-B, Chen F, Wu Z-Y. An artificial photosynthesis system based on CeO2 as light harvester and N-doped graphene Cu(II) complex as artificial metalloenzyme for CO2 reduction to methanol fuel. Cat Com 2016;73:7–11. https:// doi.org/10.1016/j.catcom.2015.10.004. [210] Qiu P, Park B, Choi J, Cui M, Kim J, Khim J. BiVO4/Bi2O3 heterojunction deposited on graphene for an enhanced visible-light photocatalytic activity. J Alloys Compd 2017;706:7–15. https://doi.org/10.1016/j.jallcom.2017.02.232. [211] Ha E, Liu W, Wang L, Man H-W, Hu L, Tsang SCE, et al. Cu2ZnSnS4/MoS2-reduced graphene oxide heterostructure: nanoscale interfacial contact and enhanced photocatalytic hydrogen generation. Sci Rep 2017;7:39411. https://doi.org/10.1038/srep39411. [212] Liu C, Dong X, Hao Y, Wang X, Ma H, Zhang X. Efficient photocatalytic dye degradation over Er-doped BiOBr hollow microspheres wrapped with graphene nanosheets: enhanced solar energy harvesting and charge separation. RSC Adv 2017;7:22415–23. https://doi.org/10.1039/C7RA02402A. [213] Hou J, Wang Z, Kan W, Jiao S, Zhu H, Kumar RV. Efficient visible-light-driven photocatalytic hydrogen production using CdS@TaON core–shell composites coupled with graphene oxide nanosheets. J Mater Chem 2012;22:7291–9. https://doi.org/10.1039/ C2JM15791H. [214] Zhang W, Xiao X, Zeng X, Li Y, Zheng L, Wan C. Enhanced photocatalytic activity of TiO2 nanoparticles using SnS2/RGO hybrid as cocatalyst: DFT study and photocatalytic mechanism. J Alloys Compd 2016;685:774–83. https://doi.org/10.1016/j.jallcom.2016.06.199.

586

Nanocarbon and its Composites

[215] Zhu B, Lin B, Zhou Y, Sun P, Yao Q, Chen Y, et al. Enhanced photocatalytic H2 evolution on ZnS loaded with graphene and MoS2 nanosheets as cocatalysts. J Mater Chem A 2014;2:3819–27. https://doi.org/10.1039/C3TA14819J. [216] Low J, Yu J, Li Q, Cheng B. Enhanced visible-light photocatalytic activity of plasmonic Ag and graphene comodified Bi2WO6 nanosheets. Phys Chem Chem Phys 2013;16: 1111–20. https://doi.org/10.1039/C3CP53820F. [217] Ding N, Fan Y, Luo Y, Li D, Meng Q. Enhancement of H2 evolution over new ZnIn2S4/ RGO/MoS2 photocatalysts under visible light. APL Mater 2015;3:104417. https://doi. org/10.1063/1.4930213. [218] Meng F, Cushing SK, Li J, Hao S, Wu N. Enhancement of solar hydrogen generation by synergistic interaction of La2Ti2O7 photocatalyst with plasmonic gold nanoparticles and reduced graphene oxide nanosheets. ACS Catal 2015;5:1949–55. https://doi.org/10.1021/ cs5016194. [219] Yan M, Hua Y, Zhu F, Gu W, Jiang J, Shen H, et al. Fabrication of nitrogen doped graphene quantum dots-BiOI/MnNb2O6 p-n junction photocatalysts with enhanced visible light efficiency in photocatalytic degradation of antibiotics. Appl Catal Environ 2017;202:518–27. https://doi.org/10.1016/j.apcatb.2016.09.039. [220] Tonda S, Kumar S, Gawli Y, Bhardwaj M, Ogale S. g-C3N4 (2D)/CdS (1D)/rGO (2D) dual-interface nano-composite for excellent and stable visible light photocatalytic hydrogen generation. Int J Hydrogen Energy 2017;42:5971–84. https://doi.org/10.1016/j. ijhydene.2016.11.065. [221] Yan Y, Wang C, Yan X, Xiao L, He J, Gu W, et al. Graphene acting as surface phase junction in anatase–graphene–rutile heterojunction photocatalysts for H2 production from water splitting. J Phys Chem C 2014;118:23519–26. https://doi.org/10.1021/ jp507087k. [222] Ao Y, Xu L, Wang P, Wang C, Hou J, Qian J, et al. Graphene and TiO2 comodified flowerlike Bi2O2CO3: a novel multiheterojunction photocatalyst with enhanced photocatalytic activity. Appl Surf Sci 2015;355:411–8. https://doi.org/10.1016/j.apsusc.2015.07.027. [223] Iwase A, Ng YH, Ishiguro Y, Kudo A, Amal R. Reduced graphene oxide as a solid-state electron mediator in z-scheme photocatalytic water splitting under visible light. J Am Chem Soc 2011;133:11054–7. https://doi.org/10.1021/ja203296z. [224] Li Y, Wang L, Ge J, Wang J, Li Q, Wan W, et al. Graphene quantum dots modified ZnO + Cu heterostructure photocatalysts with enhanced photocatalytic performance. RSC Adv 2016;6:106508–15. https://doi.org/10.1039/C6RA15707F. [225] Chen F, Yang Q, Li X, Zeng G, Wang D, Niu C, et al. Hierarchical assembly of graphenebridged Ag3PO4/Ag/BiVO4 (040) Z-scheme photocatalyst: an efficient, sustainable and heterogeneous catalyst with enhanced visible-light photoactivity towards tetracycline degradation under visible light irradiation. Appl Catal Environ 2017;200:330–42. https://doi.org/10.1016/j.apcatb.2016.07.021. [226] Wu F, Li X, Liu W, Zhang S. Highly enhanced photocatalytic degradation of methylene blue over the indirect all-solid-state Z-scheme g-C3N4-RGO-TiO2 nanoheterojunctions. Appl Surf Sci 2017;405:60–70. https://doi.org/10.1016/j.apsusc.2017.01.285. [227] Ma D, Wu J, Gao M, Xin Y, Sun Y, Ma T. Hydrothermal synthesis of an artificial Z-scheme visible light photocatalytic system using reduced graphene oxide as the electron mediator. Chem Eng J 2017;313:1567–76. https://doi.org/10.1016/j. cej.2016.11.036. [228] Wang Y, Yu J, Xiao W, Li Q. Microwave-assisted hydrothermal synthesis of graphene based Au–TiO2 photocatalysts for efficient visible-light hydrogen production. J Mater Chem A 2014;2:3847–55. https://doi.org/10.1039/C3TA14908K.

Recent advances of nanocarbon-inorganic hybrids in photocatalysis

587

[229] Sun S, Sun M, Kong Y, Fang Y, Yao Y. MoS2 and graphene as dual, cocatalysts for enhanced visible light photocatalytic activity of Fe2O3. J Sol-Gel Sci Technol 2016;80:719–27. https://doi.org/10.1007/s10971-016-4165-2. [230] Susanti YD, Afifah N, Saleh R. Multifunctional photocatalytic degradation of methylene blue using LaMnO3/Fe3O 4 nanocomposite on different types of graphene. J Phys Conf Ser 2017;820:012021 https://doi.org/10.1088/1742-6596/820/1/012021. [231] Kumar A, Rout L, Achary LSK, Mohanty A, Dhaka RS, Dash P. An investigation into the solar light-driven enhanced photocatalytic properties of a graphene oxide–SnO2–TiO2 ternary nanocomposite. RSC Adv 2016;6:32074–88. https://doi.org/10.1039/C6RA02067D. [232] Tan L-L, Ong W-J, Chai S-P, Mohamed AR. Noble metal modified reduced graphene oxide/TiO2 ternary nanostructures for efficient visible-light-driven photoreduction of carbon dioxide into methane. Appl Catal Environ 2015;166–167:251–9. https://doi. org/10.1016/j.apcatb.2014.11.035. [233] Sadiq MMJ, Shenoy US, Bhat DK. Novel RGO–ZnWO4–Fe3O4 nanocomposite as high performance visible light photocatalyst. RSC Adv 2016;6:61821–9. https://doi.org/ 10.1039/C6RA13002J. [234] Ba´rdos E, Kova´cs G, Gyulava´ri T, N
emeth K, Kecsenovity E, Berki P, et al. Novel synthesis approaches for WO3-TiO2/MWCNT composite photocatalysts- problematic issues of photoactivity enhancement factors. Catal Today 2018;300:28–38. https://doi.org/ 10.1016/j.cattod.2017.03.019. [235] Wang X, Yuan B, Xie Z, Wang D, Zhang R. ZnS–CdS/Graphene oxide heterostructures prepared by a light irradiation-assisted method for effective photocatalytic hydrogen generation. J Colloid Interface Sci 2015;446:150–4. https://doi.org/10.1016/j.jcis. 2015.01.051. [236] Jo W-K, Selvam NCS. Z-scheme CdS/g-C3N4 composites with RGO as an electron mediator for efficient photocatalytic H2 production and pollutant degradation. Chem Eng J 2017;317:913–24. https://doi.org/10.1016/j.cej.2017.02.129. [237] Myilsamy M, Mahalakshmi M, Subha N, Rajabhuvaneswari A, Murugesan V. Visible light responsive mesoporous graphene–Eu2O3/TiO2 nanocomposites for the efficient photocatalytic degradation of 4-chlorophenol. RSC Adv 2016;6:35024–35. https://doi. org/10.1039/C5RA27541E. [238] Khan Z, Chetia TR, Vardhaman AK, Barpuzary D, Sastri CV, Qureshi M. Visible light assisted photocatalytic hydrogen generation and organic dye degradation by CdS–metal oxide hybrids in presence of graphene oxide. RSC Adv 2012;2:12122–8. https://doi.org/ 10.1039/C2RA21596A. [239] Li Y, Wang H, Peng S. Tunable photodeposition of MoS2 onto a composite of reduced graphene oxide and CdS for synergic photocatalytic hydrogen generation. J Phys Chem C 2014;118:19842–8. https://doi.org/10.1021/jp5054474. [240] Hou J, Yang C, Cheng H, Wang Z, Jiao S, Zhu H. Ternary 3D architectures of CdS QDs/ graphene/ZnIn2S4 heterostructures for efficient photocatalytic H2 production. Phys Chem Chem Phys 2013;15:15660–8. https://doi.org/10.1039/C3CP51857D. [241] Sun L, Shao R, Tang L, Chen Z. Synthesis of ZnFe2O4/ZnO nanocomposites immobilized on graphene with enhanced photocatalytic activity under solar light irradiation. J Alloys Compd 2013;564:55–62. https://doi.org/10.1016/j.jallcom.2013.02.147. [242] Kumar S, Sharma V, Bhattacharyya K, Krishnan V. Synergetic effect of MoS2–RGO doping to enhance the photocatalytic performance of ZnO nanoparticles. New J Chem 2016;40:5185–97. https://doi.org/10.1039/C5NJ03595C.

588

Nanocarbon and its Composites

[243] Kumar S, Sharma R, Sharma V, Harith G, Sivakumar V, Krishnan V. Role of RGO support and irradiation source on the photocatalytic activity of CdS–ZnO semiconductor nanostructures. Beilstein J Nanotechnol 2016;7:1684–97. https://doi.org/10.3762/ bjnano.7.161. [244] Islam MJ, Reddy DA, Ma R, Kim Y, Kim TK. Reduced-graphene-oxide-wrapped BiOIAgI heterostructured nanocomposite as a high-performance photocatalyst for dye degradation under solar light irradiation. Solid State Sci 2016;61:32–9. https://doi.org/ 10.1016/j.solidstatesciences.2016.09.006. [245] Hao X, Jin Z, Yang H, Lu G, Bi Y. Peculiar synergetic effect of MoS2 quantum dots and graphene on Metal-Organic Frameworks for photocatalytic hydrogen evolution. Appl Catal Environ 2017;210:45–56. https://doi.org/10.1016/j.apcatb.2017.03.057. [246] Zhao X, Liu X, Zhang Z, Liu X, Zhang W. Facile preparation of a novel SnO2@UiO-66/ rGO hybrid with enhanced photocatalytic activity under visible light irradiation. RSC Adv 2016;6:92011–9. https://doi.org/10.1039/C6RA18140F.