- Email: [email protected]
rGO heterojunction for photocatalytic degradation of organic pollutants
Materials Research Bulletin 121 (2020) 110621
Contents lists available at ScienceDirect
Materials Research Bulletin journal homepage: www.elsevier.com/locate/matresbu
Preparation and characterization of novel Ag3VO4/Cu-MOF/rGO heterojunction for photocatalytic degradation of organic pollutants ⁎
Elham Akbarzadeha, , Hossein Zare Soheilia, Mojtaba Hosseinifardb, Mohammad Reza Gholamia, a b
T ⁎
Department of Chemistry, Sharif University of Technology, Tehran, 11365-11155, Iran Semiconductors Department, Materials and Energy Research Center, Tehran, 14155-4777, Iran
A R T I C LE I N FO
A B S T R A C T
Keywords: Photocatalyst Visible light Metal organic frameworks Ag3VO4/Cu-MOF/rGO nanocomposite
Cu-based metal organic framework/rGO was used as an effective cocatalyst to synthesis novel Ag3VO4/Cu-MOF/ rGO nanocomposite. The resulting photocatalysts were characterized by different microscopic and spectroscopic methods. The photocatalytic degradation studies on acid blue 92 showed that Ag3VO4/Cu-MOF/rGO nanocomposite indicated significant improved activity compared with pure Ag3VO4 and Cu-MOF/rGO. The improved photocatalytic activity of nanocomposite was attributed to the increased surface area and effective charge carrier separation and transport in the nanocomposite.
1. Introduction Nowadays energy issue and environmental pollution are two worldwide problems in front of human society. In recent years, photocatalysis over semiconductor materials has been widely studied as a promising strategy for solar energy alteration and solving environmental problems [1–5]. Along with other semiconductors, Ag based photocatalysts such as Ag3PO4 [6], Ag2CO3 [7], Ag3VO4 [8], AgBr [9] and AgI [10] have been attracted attention due to their great visible light response. Among Ag based semiconductors, Ag3VO4 which is a visible light response catalyst with narrow band gap of around 2.2 eV, has been extensively studied as a promising photocatalyst [11,12]. However, low specific surface area and high electron/hole recombination rate are two principle factors that affect the photocatalytic activity of this semiconductor [13,14]. Hence, some strategies are required to improve its photocatalytic efficiency. Many attempts have been allocated to elevate the photocatalytic activity of Ag3VO4, such as junction with other materials to increase the lifetime of electrons and holes and enhance the interfacial charge transfer [15–18]. Metal organic Frameworks (MOFs) have attracted considerable regard as a novel group of porous materials in the past decade in catalysis field because of their significant attributes [19–21]. Great variation of the multifunctional organic linkers and metal ion types is an additional privilege which enhance attention to this class of metal organic materials [22]. MOFs have been widely studied as efficient materials in photocatalytic reactions [23,24], CO2 reduction [25] and hydrogen generation [26]. In recent studies, semiconductor materials such as
⁎
TiO2 [27], Ag3PO4 [28], Co3O4 [29], CdS [30], BiOI [31] and gC3N4 [32,33] have been coupled with MOFs to enhance their photocatalytic efficiency. Recently, graphene based-materials have received great interest as cocatalyst for synthesis of efficient photocatalyst because of the specific surface area and their unique electronic properties [34,35]. In present study, Cu-MOF/rGO has been used as a promising cocatalyst to improve photocatalytic performance of the Ag3VO4 particles. The photocatalytic activity of this nanocomposite was examined by degradation of AB92 dye in aqueous solution under visible light and photocatalytic mechanism of Ag3VO4/Cu-MOF/rGO was also discussed. 2. Experimental section 2.1. Chemicals Terephthalic acid (tpaH), N,N-dimethylformamide (DMF), Silver nitrate (Ag(NO3)), Copper(II) Nitrate Trihydrate (Cu(NO3)2.3H2O), were supplied from Merck. Vanadium pentoxide (V2O5), Sodium hydroxide (NaOH) were purchased from Sigma-Aldrich. 2.2. Preparation of nanocomposite A modified Hummers procedure was applied to prepare GO from natural graphite as reported before [36]. A solvothermal method was used to synthesis Cu-MOF/rGO. In a typical process, 20 mL DMF solution containing 0.36 g tpaH was added drop wisely to the mixture of
Corresponding authors. E-mail addresses: [email protected] (E. Akbarzadeh), [email protected] (M.R. Gholami).
https://doi.org/10.1016/j.materresbull.2019.110621 Received 30 May 2019; Received in revised form 11 September 2019; Accepted 11 September 2019 Available online 12 September 2019 0025-5408/ © 2019 Elsevier Ltd. All rights reserved.
Materials Research Bulletin 121 (2020) 110621
E. Akbarzadeh, et al.
DMF (20 mL) and Cu(NO3)2.3H2O (0.52 g) under continuous stirring. After 0.5 h of stirring at room temperature 50 mg of graphene oxide was added to the solution. After 2 h of stirring, the as obtained mixture was heated to 110 ℃ for 36 h. The final products were filtered and washed with deionized water and dried at 60 ℃ to obtain MOF/rGO powders. For comparison, the pure Cu-metal organic framework powders were synthesis under the as mentioned condition without addition of GO. For synthesis of the Ag3VO4/Cu-MOF/rGO nanocomposite 20 mL aqueous solution containing NaOH and V2O5 (6:1 mol ratio) was prepared. Then, 30 mg of Cu-MOF/rGO was added and the suspension stirred magnetically for 90 min. Subsequently, 60 mL solution of AgNO3 was added to the suspension and the reaction was continued for another 4 h under vigorously stirring at room temperature. Finally, the resulting precipitates were retrieved, washed with distilled water and dried at 60 ℃ in air. The pure Ag3VO4 was synthesized under the same condition without addition of Cu-MOF/rGO. 2.3. Characterization Fig. 1. FT-IR spectra of as synthesized nanocomposites and pure Ag3VO4 and Cu-MOF.
Raman spectra of materials were investigated by a Takram P50C0R10 Raman model spectrometer. Fourier-transform infrared (FTIR) spectra the composites were studied by an ABB BOMER MB series equipment. Energy dispersive X-ray spectroscopy (EDX) and field emission scanning electron microscopy (FE-SEM, Mira3 Tascan) were applied to investigate the morphology of materials. X-ray diffraction (XRD) data was applied to obtain phase structure of materials by a Philips X’pert diffractometer with a Cu K?? irradiation (?? =0.15406 nm) at 40 kV/40 mA. UV–vis diffuse-reflectance spectroscopy (UV–vis DRS) of as-synthesized composites were obtained using a GBC Cintra 40 equipment. Thermogravimetric analyses (TGA) were recorded over a temperature range of from 30 to 900 °C by a SDT Q600 V20.9 Build 20 thermal analyzer in N2 atmosphere. Brunauer − Emmett − Teller (BET) surface area of the catalysts and pore size distributions of corresponding materials were calculated using N2 adsorption/desorption isotherms analysis at 77 K on a BELSORBmini II. Electrochemical impedance spectroscopy (EIS) was studied by A.C. impedance spectroscopy analysis at open circuit voltage and the frequency ranged from 100 kHz to 10 Hz. 2.4. Photocatalytic performance
Fig. 2. Raman spectra of Cu-MOF/rGO nanocomposite and rGO.
Photo-degradation of the organic dyes was selected as a sample catalytic reaction for evaluation of the catalysts activity. In order to ensure adsorption/desorption equilibrium of AB92 molecules and nanocatalysts, 100 mL of AB92 (10 mg L−1) solution containing 10 mg of catalyst powder was provided and kept in the dark under stirring for 1 h. A circulating cold-water jacket that surrounded the reactor and the light source, was used for keeping temperature of the reactions unchanged at 25 ℃. The mixed suspension was irradiated with visible light, and photocatalytic reaction was started. After every 10 min irradiation, 3 mL of the dye solution was sampled and centrifuged to remove the solid materials. The AB92 concentration of each sample was evaluated by an UV–vis spectrophotometer set to characteristic absorption wavelength of AB92,? ?=571 nm.
860 cm−1 corresponding to the stretching vibration of VO4 unit [37]. Ag3VO4/Cu-MOF/rGO spectrum also shows additional peaks that can be attributed to the presence of Cu-MOF/rGO in nanocomposite. Raman spectrum of rGO and Cu-MOF/rGO are shown in Fig. 2. Raman spectra of rGO demonstrates two distinct vibrational peaks at 1350 cm−1 and 1602 cm−1 corresponding to D-band and G-band, respectively [38]. Raman spectroscopy of Cu-MOF/rGO indicates typical peaks of Cu-MOF [39]. D-band and G-band of rGO are also obvious in Raman spectra of Cu-MOF/rGO composite. The phase structure of the catalysts was investigated by X-ray diffraction patterns (Fig. 3). All the peaks in the diffraction patterns of CuMOF/rGO are in good agreement with previous report related to CuMOF [40]. Because of the small amount of rGO in the composite, it is difficult to attribute any of XRD peaks of Cu-MOF/rGO to rGO. All of the diffraction patterns of pure Ag3VO4 can be attributed to the monoclinic phase (JCPDS No. 43-0542) [41]. In the XRD patterns of Ag3VO4/Cu-MOF/rGO there are some additional small peaks which can be indexed to the Cu-MOF/rGO composite. The microstructures and morphology of the catalysts were characterized by FE-SEM (Fig. 4). SEM picture of the Ag3VO4/Cu-MOF indicates Ag3VO4 particles a long with plentiful number of agglomerated MOF nanoparticles (Fig. 4a). Fig. 4b demonstrates SEM picture of the Cu-MOF incorporated with rGO nanosheets. It is obvious from Fig. 4c that Ag3VO4 particles were successfully introduced to the Cu-MOF/rGO
3. Results and discussion 3.1. Characterization of materials The FT-IR spectra of as-synthesized nanocomposites and pure materials are depicted in Fig. 1. Two characteristic peaks of COO- at 1300 cm−1 and 1600 cm−1 are visible in the FT-IR spectra of Cu-MOF and Cu-MOF/rGO. The peaks located approximately at 1650 cm−1 and 2920 cm−1 are ascribed to C]O and C–H vibration, respectively [22]. The FT-IR spectra of Ag3VO4 and Ag3VO4/Cu-MOF/rGO nanocomposite, are shown two strong absorption peaks at about 740 cm-1 and 2
Materials Research Bulletin 121 (2020) 110621
E. Akbarzadeh, et al.
solvated Cu(tpa). (dmf) to desolvated Cu(tpa) [40,42]. The mass change after 300 ℃ indicates pyrolysis of the Cu-MOF/rGO composite. UV-vis diffuse reflectance spectroscopy of Ag3VO4 and Ag3VO4/CuMOF/rGO at divers light wavelength was measured to study the optical response (Fig. 7). Pure Ag3VO4 illustrates strong photo-absorption in visible light with the absorption edge around 600 nm. DRS results of the Ag3VO4/Cu-MOF/rGO nanocomposite demonstrate a red shift in absorption edge compared to pure Ag3VO4. Electrochemical impedance spectroscopy results have been used to study the charge transfer resistance of the materials (Fig. 8). Nyquist plots of the materials were recorded in the presence of 5 mM K3[Fe (CN)6] : K4[Fe(CN)6] (1:1) mixture containing 0.1 M KCl. EIS results indicated that Ag3VO4/Cu-MOF/rGO has lower charge transfer resistance than Cu-MOF/rGO and pure Ag3VO4. These results highlight an increased interfacial electron transport in the Ag3VO4/Cu-MOF/rGO nanocomposites. Fig. 3. XRD patterns of the prepared materials.
3.2. Photocatalytic performance of the catalysts
nanocomposite. The EDX elemental mapping of the Ag3VO4/Cu-MOF/ rGO indicates presence of O, Cu, C, Ag and V elements in the nanocomposite (Fig. 4d). Fig. 5 demonstrates BET surface area of Cu-MOF/rGO (a) Ag3VO4 (b) and Ag3VO4/Cu-MOF/rGO (c) which were acquired from nitrogen adsorption and desorption isotherms analysis at 77 K. The BET surface areas were obtained to be 16.25, 3.59 and 5.63 m2/g for Cu-MOF/rGO, Ag3VO4 and Ag3VO4/Cu-MOF/rGO, respectively. Comparison between Ag3VO4 and Ag3VO4/Cu-MOF/rGO demonstrated increased surface area of nanocomposite. Thermogravimetric analysis results of the prepared materials in N2 atmosphere are indicated in Fig. 6. Primary weight lost about 100 ℃ in TGA curve of GO is caused by the evaporation of surface water molecules and secondary mass lost at 150–300 ℃ originated from decomposition of surface oxygen groups in GO. In the TGA plots of Ag3VO4/ Cu-MOF/rGO and Cu-MOF/rGO, the weight losses before 300 ℃ are mainly due to the removal of the water molecules and transformation of
Photodegradation of organic dyes was chosen as an example reaction to evaluate catalytic activity of Ag3VO4 and Ag3VO4/Cu-MOF/rGO nanocomposite. Langmuir-Hinshelwood (L-H) kinetics model dC (r = − dt = kapp C ) was applied to investigate the kinetic of photocatalytic reactions and account the linear simulation of AB92 degradation. The rate coefficients of AB92 degradation over the photocatalysts were obtained by plot of ln (C/C0) versus time. C0 and C introduce concentration of dye molecules before beginning the reaction and t min after light irradiation, respectively (Fig. 9). The experimental results indicated that in the absence of any catalyst under visible light irradiation, AB92 is approximately stable. The Ag3VO4/Cu-MOF/rGO nanocomposite illustrated remarkable progress in photocatalytic degradation of AB92 than pure Ag3VO4 and Ag3VO4/ Cu-MOF under visible light irradiation. The degradation rate constant of the Ag3VO4/Cu-MOF/rGO nanocomposite (0.008 min−1) is higher by a coefficient of 2.5 and 4.7 compare to pure Ag3VO4 (0.0032 min−1) and Cu-MOF/rGO
Fig. 4. FESEM pictures of Ag3VO4/Cu-MOF (a) Cu-MOF/rGO (b) Ag3VO4/Cu-MOF/rGO (c) and EDX elemental mapping of nanocomposite (d). 3
Materials Research Bulletin 121 (2020) 110621
E. Akbarzadeh, et al.
Fig. 5. N2 adsorption/desorption isotherm of the prepared materials. Pore size distributions of samples (inset) calculated by the BJH method.
Fig. 6. TGA curves of the prepared materials. Fig. 7. UV–vis diffuse-reflectance spectra of Ag3VO4 and Ag3VO4/Cu-MOF/ rGO.
(0.0017 min−1) respectively. These results revealed that combination of the Ag3VO4 nanoparticles with Cu-MOF/rGO substantially enhances the photocatalytic activity. The superior photocatalytic performance can be attributed to the increased surface area and enhancement of interfacial electron transfer and charge carrier separation. To study the weight percentage ratio of Ag3VO4 and Cu-MOF/rGO effect on the catalytic activity, composites with different amount of CuMOF/rGO were prepared (Fig. 10). The best catalytic performance was observed when the weight percentage ratio of Ag3VO4 and Cu-MOF/ rGO was 90:10 with kapp =0.008 min−1. Apparent rate constants were
obtained to be 0.0068 min-1 and 0.0044 min-1 for 85% Ag3VO4/CuMOF/rGO and 95% Ag3VO4/Cu-MOF/rGO, respectively. In order to study the stability of as-synthesized nanocomposite, three consecutive cycles of photocatalytic AB92 degradation were performed using the retrieved Ag3VO4/Cu-MOF/rGO. After the third photoreaction run, catalytic activity of the nanocomposite was decreased to about 70% efficiency of the first run, indicating that stability of Ag3VO4/Cu-MOF/rGO is almost acceptable. It should be noted that 4
Materials Research Bulletin 121 (2020) 110621
E. Akbarzadeh, et al.
Fig. 8. Electrochemical impedance spectroscopy (Nyquist plots) of the materials.
Fig. 10. Plot of ln(C/C0) for AB92 degradation in the presence of different nanocomposites.
Ag-based photocatalysts are not so stable in visible light irradiation.
3.3. Possible photocatalytic mechanism It is appealing to consider the probable reaction mechanism for the photocatalytic performance of the Ag3VO4/Cu-MOF/rGO nanocomposite in AB92 photodegradation. The main reactive species that contribute in degradation process are O•2−, HO•2 and OH•. These active radicals produce by photo-induced electrons and holes that combine with pre-adsorbed H2O/OH− on the surface of photocatalyst and available oxygen in the solution [43]. Several scavengers (t-BuOH, CH3OH, iodide ion and p-benzoqinone) were added to the initial dye solution to investigate the role of reactive species which directly taking part in AB92 degradation process in the presence of Ag3VO4/Cu-MOF/rGO nanocomposite. As observed in Fig. 11, experimental results demonstrated that the photo-degradation of AB92 molecules was almost inhibited in the presence of p-benzoqinone. These results prove that O•2− plays the main role in the degradation of AB92 molecules. Whereas, the photo-degradation of AB92 was remarkably increased in the presence of CH3OH, indicating that the holes do not have any major role in dye degradation. In fact, CH3OH reduced the electrons – holes recombination and then increased photodegradation of dye molecules. However, by addition of KI and t-BuOH as OH• scavenger in dye solution the degradation of dye molecules was almost invariable. On the basis of the obtained results from the application of inorganic compounds as scavenger, it is obvious that O•2− is the most important active species in AB92 photo-degradation in the presence of Ag3VO4/Cu-MOF/rGO
Fig. 11. The effect of various scavengers in the degradation of dye molecules over Ag3VO4/Cu-MOF/rGO.
catalyst. According to the experimental results a probable photocatalytic mechanism of dye degradation in the presence of Ag3VO4/Cu-MOF/ rGO was proposed as illustrated in Scheme. 1. In the nanocomposite, Ag3VO4 particles were applied as photoelectron donor and rGO was used as the charge carrier from Ag3VO4 to Cu-MOF as well as
Fig. 9. Plot of C/C0 (a) and ln(C/C0) (b) for AB92 photodegradation in the presence of different catalysts. 5
Materials Research Bulletin 121 (2020) 110621
E. Akbarzadeh, et al.
Scheme 1. Proposed photocatalytic mechanism and charge transfer scheme of the Ag3VO4/Cu-MOF/rGO under visible light irradiation.
supporting matrix for Ag3VO4 and Cu-MOF.
[14] L. Zhang, Y. He, P. Ye, W. Qin, Y. Wu, T. Wu, Enhanced photodegradation activity of Rhodamine B by Co3O4/Ag3VO4 under visible light irriadiation, Mater. Sci. Eng. B 178 (2013) 45–52. [15] K. Wangkawong, S. Phanichphant, D. Tantraviwat, B. Inceesungvorn, CoTiO3/ Ag3VO4 composite: a study on the role of CoTiO3 and the active species in the photocatalytic degradation of methylene blue, J. Colloid Interface Sci. 454 (2015) 210–215. [16] R. Ran, X. Meng, Z. Zhang, Facile preparation of novel graphene oxide-modified Ag2O/Ag3VO4/AgVO3 composites with high photocatalytic activities under visible light irradiation, Appl. Catal. B 196 (2016) 1–15. [17] R. Ran, J.G. McEvoy, Z. Zhang, Ag2O/Ag3VO4/Ag4V2O7 heterogeneous photocatalyst prepared by a facile hydrothermal synthesis with enhanced photocatalytic performance under visible light irradiation, Mater. Res. Bull. 74 (2016) 140–150. [18] F. Kiantazh, A. Habibi-Yangjeh, Ag3VO4/ZnO nanocomposites with an n–n heterojunction as novel visible-light-driven photocatalysts with highly enhanced activity, Mater. Sci. Semicond. Process. 39 (2015) 671–679. [19] Y.-B. Huang, J. Liang, X.-S. Wang, R. Cao, Multifunctional metal–organic framework catalysts: synergistic catalysis and tandem reactions, Chem. Soc. Rev. 46 (2017) 126–157. [20] H.-Y. Zhang, X.-P. Hao, L.-P. Mo, S.-S. Liu, W.-B. Zhang, Z.-H. Zhang, A magnetic metal–organic framework as a highly active heterogeneous catalyst for one-pot synthesis of 2-substituted alkyl and aryl (indolyl) kojic acid derivatives, New J. Chem. 41 (2017) 7108–7115. [21] E. Akbarzadeh, H.Z. Soheili, M.R. Gholami, Novel Cu2O/Cu-MOF/rGO is reported as highly efficient catalyst for reduction of 4-Nitrophenol, Mater. Chem. Phys. (2019) 121846. [22] E. Akbarzadeh, M. Falamarzi, M.R. Gholami, Synthesis of M/CuO (M= Ag, Au) from Cu based Metal Organic Frameworks for efficient catalytic reduction of pnitrophenol, Mater. Chem. Phys. 198 (2017) 374–379. [23] C.-C. Wang, J.-R. Li, X.-L. Lv, Y.-Q. Zhang, G. Guo, Photocatalytic organic pollutants degradation in metal–organic frameworks, Energy Environ. Sci. 7 (2014) 2831–2867. [24] J. Qiu, L. Yang, M. Li, J. Yao, Metal nanoparticles decorated MIL-125-NH2 and MIL125 for efficient photocatalysis, Mater. Res. Bull. 112 (2019) 297–306. [25] Y. Fu, D. Sun, Y. Chen, R. Huang, Z. Ding, X. Fu, Z. Li, An amine‐functionalized titanium metal–Organic framework photocatalyst with visible‐light‐Induced activity for CO2 reduction, Angew. Chemie Int. Ed. 51 (2012) 3364–3367. [26] R. Lin, L. Shen, Z. Ren, W. Wu, Y. Tan, H. Fu, J. Zhang, L. Wu, Enhanced photocatalytic hydrogen production activity via dual modification of MOF and reduced graphene oxide on CdS, Chem. Commun. 50 (2014) 8533–8535. [27] S. Abedi, A. Morsali, Ordered mesoporous metal–organic frameworks incorporated with amorphous TiO2 as photocatalyst for selective aerobic oxidation in sunlight irradiation, ACS Catal. 4 (2014) 1398–1403. [28] N. Mohaghegh, M. Tasviri, E. Rahimi, M. Gholami, Comparative studies on Ag3PO4/BiPO4–metal-organic framework–graphene-based nanocomposites for photocatalysis application, Appl. Surf. Sci. 351 (2015) 216–224. [29] T. Zeng, X. Zhang, S. Wang, H. Niu, Y. Cai, Spatial confinement of a Co3O4 catalyst in hollow metal–organic frameworks as a nanoreactor for improved degradation of organic pollutants, Environ. Sci. Technol. 49 (2015) 2350–2357. [30] L. Hu, G. Deng, W. Lu, S. Pang, X. Hu, Deposition of CdS nanoparticles on MIL-53 (Fe) metal-organic framework with enhanced photocatalytic degradation of RhB under visible light irradiation, Appl. Surf. Sci. 410 (2017) 401–413. [31] S.G. Khasevani, M. Gholami, Engineering a highly dispersed core@ shell structure for efficient photocatalysis: a case study of ternary novel BiOI@ MIL-88A (Fe)@ gC3N4 nanocomposite, Mater. Res. Bull. 106 (2018) 93–102. [32] G. Xu, H. Zhang, J. Wei, H.-X. Zhang, X. Wu, Y. Li, C. Li, J. Zhang, J. Ye, Integrating the g-C3N4 nanosheet with B–H bonding decorated metal–Organic framework for CO2 activation and photoreduction, ACS Nano (2018). [33] X. Zhang, Y. Yang, W. Huang, Y. Yang, Y. Wang, C. He, N. Liu, M. Wu, L. Tang, gC3N4/UiO-66 nanohybrids with enhanced photocatalytic activities for the oxidation of dye under visible light irradiation, Mater. Res. Bull. 99 (2018) 349–358. [34] X. Hao, Z. Jin, H. Yang, G. Lu, Y. Bi, Peculiar synergetic effect of MoS2 quantum dots and graphene on Metal-Organic Frameworks for photocatalytic hydrogen evolution, Appl. Catal. B 210 (2017) 45–56. [35] L. Yang, C. Xu, F. Wan, H. He, H. Gu, J. Xiong, Synthesis of RGO/BiOI/ZnO composites with efficient photocatalytic reduction of aqueous Cr (VI) under visible-light irradiation, Mater. Res. Bull. 112 (2019) 154–158.
4. Conclusion In present study, Cu-MOF/rGO was applied as a favorable cocatalyst to improve photocatalytic activity of the Ag3VO4 particles. Experimental results asserted that the as synthesized Ag3VO4/Cu-MOF/ rGO composite displayed improved catalytic activity in photo-degradation of dye molecules. The main reason for this enhancement can be attributed to the migration of photogenerated electron between Ag3VO4 and Cu-MOF through rGO nanosheets. Usage of inorganic compounds as scavenger demonstrated that O•2− was the major reactive species in dye degradation in the presence of Ag3VO4/Cu-MOF/rGO photocatalyst. Acknowledgments The authors gratefully acknowledge the Iran National Science Foundation for financial support (INSF no.96016238). References [1] T. Di, B. Zhu, B. Cheng, J. Yu, J. Xu, A direct Z-scheme g-C3N4/SnS2 photocatalyst with superior visible-light CO2 reduction performance, J. Catal. 352 (2017) 532–541. [2] E. Akbarzadeh, M.R. Gholami, Pt–NiO–Al2O3/G derived from graphene-supported layered double hydroxide as efficient catalyst for p-nitrophenol reduction, Res. Chem. Intermed. 43 (2017) 5829–5839. [3] S.M. El-Sheikh, T.M. Khedr, A. Hakki, A.A. Ismail, W.A. Badawy, D.W. Bahnemann, Visible light activated carbon and nitrogen co-doped mesoporous TiO2 as efficient photocatalyst for degradation of ibuprofen, Sep. Purif. Technol. 173 (2017) 258–268. [4] J. Zhang, Z. Ma, Flower-like Ag3VO4/BiOBr np heterojunction photocatalysts with enhanced visible-light-driven catalytic activity, Mol. Catal. 436 (2017) 190–198. [5] M. Kang, J. Liang, F. Wang, X. Chen, Y. Lu, J. Zhang, Structural design of hexagonal/monoclinic WO3 phase junction for photocatalytic degradation, Mater. Res. Bull. (2019) 110614. [6] M. You, J. Pan, C. Chi, B. Wang, W. Zhao, C. Song, Y. Zheng, C. Li, The visible light hydrogen production of the Z-Scheme Ag3PO4/Ag/g-C3N4 nanosheets composites, J. Mater. Sci. 53 (2018) 1978–1986. [7] P. Sánchez-Cid, C. Jaramillo-Páez, J. Navío, A. Martín-Gómez, M. Hidalgo, Coupling of Ag2CO3 to an optimized ZnO photocatalyst: advantages vs. Disadvantages, J. Photochem. Photobiol. A: Chem. (2018). [8] S. Le, W. Li, Y. Li, B. Borjigin, G. Li, X. Wang, Tetracycline Removal Under Solar Illumination Over Ag3VO4/mpg‐C3N4 Heterojunction Photocatalysts, Photochem. Photobiol. (2018). [9] H. Wang, L. Zou, Y. Shan, X. Wang, Ternary GO/Ag3PO4/AgBr composite as an efficient visible-light-driven photocatalyst, Mater. Res. Bull. 97 (2018) 189–194. [10] J. Zhang, Z. Ma, Ag3VO4/AgI composites for photocatalytic degradation of dyes and tetracycline hydrochloride under visible light, Mater. Lett. 216 (2018) 216–219. [11] J. Barzegar, A. Habibi-Yangjeh, A. Akhundi, S. Vadivel, Novel ternary g-C3N4/ Ag3VO4/AgBr nanocomposites with excellent visible-light-driven photocatalytic performance for environmental applications, Solid State Sci. 78 (2018) 133–143. [12] E. Akbarzadeh, S.R. Setayesh, M.R. Gholami, Synthesis of the visible-light-driven Ag 3 VO 4/Ag 3 PO 4/Ag photocatalysts with enhanced photocatalytic activity, RSC Adv. 6 (2016) 14909–14915. [13] T. Zhu, Y. Song, H. Ji, Y. Xu, Y. Song, J. Xia, S. Yin, Y. Li, H. Xu, Q. Zhang, Synthesis of g-C3N4/Ag3VO4 composites with enhanced photocatalytic activity under visible light irradiation, Chem. Eng. J. 271 (2015) 96–105.
6
Materials Research Bulletin 121 (2020) 110621
E. Akbarzadeh, et al.
[40] C.G. Carson, K. Hardcastle, J. Schwartz, X. Liu, C. Hoffmann, R.A. Gerhardt, R. Tannenbaum, Synthesis and structure characterization of copper terephthalate metal–organic frameworks, Eur. J. Inorg. Chem. 2009 (2009) 2338–2343. [41] J. Ren, Y. Wu, Y. Dai, D. Sha, J. Pan, M. Chen, J. Wang, Q. Wang, N. Ye, X. Yan, Preparation and characterization of graphitic C 3 N 4/Ag 3 VO 4 with excellent photocatalytic performance under visible light irradiation, J. Mater. Sci. Mater. Electron. 28 (2017) 641–651. [42] S. He, Z. Li, L. Ma, J. Wang, S. Yang, Graphene oxide-templated growth of MOFs with enhanced lithium-storage properties, New J. Chem. 41 (2017) 14209–14216. [43] Z. He, Y. Shi, C. Gao, L. Wen, J. Chen, S. Song, BiOCl/BiVO4 p–n heterojunction with enhanced photocatalytic activity under visible-light irradiation, J. Phys. Chem. C 118 (2013) 389–398.
[36] M.-Q. Yang, Y.-J. Xu, Basic principles for observing the photosensitizer role of graphene in the graphene–semiconductor composite photocatalyst from a case study on graphene–ZnO, J. Phys. Chem. C 117 (2013) 21724–21734. [37] N. Tian, H. Huang, Y. He, Y. Guo, T. Zhang, Y. Zhang, Mediator-free direct Z-scheme photocatalytic system: BiVO 4/gC 3 N 4 organic–inorganic hybrid photocatalyst with highly efficient visible-light-induced photocatalytic activity, J. Chem. Soc. Dalton Trans. 44 (2015) 4297–4307. [38] Y. Jin, C. Zhao, Z. Sun, Y. Lin, L. Chen, D. Wang, C. Shen, Facile synthesis of FeMOF/RGO and its application as a high performance anode in lithium-ion batteries, RSC Adv. 6 (2016) 30763–30768. [39] X. He, W.-N. Wang, Pressure-regulated synthesis of Cu (TPA)·(DMF) in microdroplets for selective CO 2 adsorption, J. Chem. Soc. Dalton Trans. 48 (2019) 1006–1016.
7
Contents lists available at ScienceDirect
Materials Research Bulletin journal homepage: www.elsevier.com/locate/matresbu
Preparation and characterization of novel Ag3VO4/Cu-MOF/rGO heterojunction for photocatalytic degradation of organic pollutants ⁎
Elham Akbarzadeha, , Hossein Zare Soheilia, Mojtaba Hosseinifardb, Mohammad Reza Gholamia, a b
T ⁎
Department of Chemistry, Sharif University of Technology, Tehran, 11365-11155, Iran Semiconductors Department, Materials and Energy Research Center, Tehran, 14155-4777, Iran
A R T I C LE I N FO
A B S T R A C T
Keywords: Photocatalyst Visible light Metal organic frameworks Ag3VO4/Cu-MOF/rGO nanocomposite
Cu-based metal organic framework/rGO was used as an effective cocatalyst to synthesis novel Ag3VO4/Cu-MOF/ rGO nanocomposite. The resulting photocatalysts were characterized by different microscopic and spectroscopic methods. The photocatalytic degradation studies on acid blue 92 showed that Ag3VO4/Cu-MOF/rGO nanocomposite indicated significant improved activity compared with pure Ag3VO4 and Cu-MOF/rGO. The improved photocatalytic activity of nanocomposite was attributed to the increased surface area and effective charge carrier separation and transport in the nanocomposite.
1. Introduction Nowadays energy issue and environmental pollution are two worldwide problems in front of human society. In recent years, photocatalysis over semiconductor materials has been widely studied as a promising strategy for solar energy alteration and solving environmental problems [1–5]. Along with other semiconductors, Ag based photocatalysts such as Ag3PO4 [6], Ag2CO3 [7], Ag3VO4 [8], AgBr [9] and AgI [10] have been attracted attention due to their great visible light response. Among Ag based semiconductors, Ag3VO4 which is a visible light response catalyst with narrow band gap of around 2.2 eV, has been extensively studied as a promising photocatalyst [11,12]. However, low specific surface area and high electron/hole recombination rate are two principle factors that affect the photocatalytic activity of this semiconductor [13,14]. Hence, some strategies are required to improve its photocatalytic efficiency. Many attempts have been allocated to elevate the photocatalytic activity of Ag3VO4, such as junction with other materials to increase the lifetime of electrons and holes and enhance the interfacial charge transfer [15–18]. Metal organic Frameworks (MOFs) have attracted considerable regard as a novel group of porous materials in the past decade in catalysis field because of their significant attributes [19–21]. Great variation of the multifunctional organic linkers and metal ion types is an additional privilege which enhance attention to this class of metal organic materials [22]. MOFs have been widely studied as efficient materials in photocatalytic reactions [23,24], CO2 reduction [25] and hydrogen generation [26]. In recent studies, semiconductor materials such as
⁎
TiO2 [27], Ag3PO4 [28], Co3O4 [29], CdS [30], BiOI [31] and gC3N4 [32,33] have been coupled with MOFs to enhance their photocatalytic efficiency. Recently, graphene based-materials have received great interest as cocatalyst for synthesis of efficient photocatalyst because of the specific surface area and their unique electronic properties [34,35]. In present study, Cu-MOF/rGO has been used as a promising cocatalyst to improve photocatalytic performance of the Ag3VO4 particles. The photocatalytic activity of this nanocomposite was examined by degradation of AB92 dye in aqueous solution under visible light and photocatalytic mechanism of Ag3VO4/Cu-MOF/rGO was also discussed. 2. Experimental section 2.1. Chemicals Terephthalic acid (tpaH), N,N-dimethylformamide (DMF), Silver nitrate (Ag(NO3)), Copper(II) Nitrate Trihydrate (Cu(NO3)2.3H2O), were supplied from Merck. Vanadium pentoxide (V2O5), Sodium hydroxide (NaOH) were purchased from Sigma-Aldrich. 2.2. Preparation of nanocomposite A modified Hummers procedure was applied to prepare GO from natural graphite as reported before [36]. A solvothermal method was used to synthesis Cu-MOF/rGO. In a typical process, 20 mL DMF solution containing 0.36 g tpaH was added drop wisely to the mixture of
Corresponding authors. E-mail addresses: [email protected] (E. Akbarzadeh), [email protected] (M.R. Gholami).
https://doi.org/10.1016/j.materresbull.2019.110621 Received 30 May 2019; Received in revised form 11 September 2019; Accepted 11 September 2019 Available online 12 September 2019 0025-5408/ © 2019 Elsevier Ltd. All rights reserved.
Materials Research Bulletin 121 (2020) 110621
E. Akbarzadeh, et al.
DMF (20 mL) and Cu(NO3)2.3H2O (0.52 g) under continuous stirring. After 0.5 h of stirring at room temperature 50 mg of graphene oxide was added to the solution. After 2 h of stirring, the as obtained mixture was heated to 110 ℃ for 36 h. The final products were filtered and washed with deionized water and dried at 60 ℃ to obtain MOF/rGO powders. For comparison, the pure Cu-metal organic framework powders were synthesis under the as mentioned condition without addition of GO. For synthesis of the Ag3VO4/Cu-MOF/rGO nanocomposite 20 mL aqueous solution containing NaOH and V2O5 (6:1 mol ratio) was prepared. Then, 30 mg of Cu-MOF/rGO was added and the suspension stirred magnetically for 90 min. Subsequently, 60 mL solution of AgNO3 was added to the suspension and the reaction was continued for another 4 h under vigorously stirring at room temperature. Finally, the resulting precipitates were retrieved, washed with distilled water and dried at 60 ℃ in air. The pure Ag3VO4 was synthesized under the same condition without addition of Cu-MOF/rGO. 2.3. Characterization Fig. 1. FT-IR spectra of as synthesized nanocomposites and pure Ag3VO4 and Cu-MOF.
Raman spectra of materials were investigated by a Takram P50C0R10 Raman model spectrometer. Fourier-transform infrared (FTIR) spectra the composites were studied by an ABB BOMER MB series equipment. Energy dispersive X-ray spectroscopy (EDX) and field emission scanning electron microscopy (FE-SEM, Mira3 Tascan) were applied to investigate the morphology of materials. X-ray diffraction (XRD) data was applied to obtain phase structure of materials by a Philips X’pert diffractometer with a Cu K?? irradiation (?? =0.15406 nm) at 40 kV/40 mA. UV–vis diffuse-reflectance spectroscopy (UV–vis DRS) of as-synthesized composites were obtained using a GBC Cintra 40 equipment. Thermogravimetric analyses (TGA) were recorded over a temperature range of from 30 to 900 °C by a SDT Q600 V20.9 Build 20 thermal analyzer in N2 atmosphere. Brunauer − Emmett − Teller (BET) surface area of the catalysts and pore size distributions of corresponding materials were calculated using N2 adsorption/desorption isotherms analysis at 77 K on a BELSORBmini II. Electrochemical impedance spectroscopy (EIS) was studied by A.C. impedance spectroscopy analysis at open circuit voltage and the frequency ranged from 100 kHz to 10 Hz. 2.4. Photocatalytic performance
Fig. 2. Raman spectra of Cu-MOF/rGO nanocomposite and rGO.
Photo-degradation of the organic dyes was selected as a sample catalytic reaction for evaluation of the catalysts activity. In order to ensure adsorption/desorption equilibrium of AB92 molecules and nanocatalysts, 100 mL of AB92 (10 mg L−1) solution containing 10 mg of catalyst powder was provided and kept in the dark under stirring for 1 h. A circulating cold-water jacket that surrounded the reactor and the light source, was used for keeping temperature of the reactions unchanged at 25 ℃. The mixed suspension was irradiated with visible light, and photocatalytic reaction was started. After every 10 min irradiation, 3 mL of the dye solution was sampled and centrifuged to remove the solid materials. The AB92 concentration of each sample was evaluated by an UV–vis spectrophotometer set to characteristic absorption wavelength of AB92,? ?=571 nm.
860 cm−1 corresponding to the stretching vibration of VO4 unit [37]. Ag3VO4/Cu-MOF/rGO spectrum also shows additional peaks that can be attributed to the presence of Cu-MOF/rGO in nanocomposite. Raman spectrum of rGO and Cu-MOF/rGO are shown in Fig. 2. Raman spectra of rGO demonstrates two distinct vibrational peaks at 1350 cm−1 and 1602 cm−1 corresponding to D-band and G-band, respectively [38]. Raman spectroscopy of Cu-MOF/rGO indicates typical peaks of Cu-MOF [39]. D-band and G-band of rGO are also obvious in Raman spectra of Cu-MOF/rGO composite. The phase structure of the catalysts was investigated by X-ray diffraction patterns (Fig. 3). All the peaks in the diffraction patterns of CuMOF/rGO are in good agreement with previous report related to CuMOF [40]. Because of the small amount of rGO in the composite, it is difficult to attribute any of XRD peaks of Cu-MOF/rGO to rGO. All of the diffraction patterns of pure Ag3VO4 can be attributed to the monoclinic phase (JCPDS No. 43-0542) [41]. In the XRD patterns of Ag3VO4/Cu-MOF/rGO there are some additional small peaks which can be indexed to the Cu-MOF/rGO composite. The microstructures and morphology of the catalysts were characterized by FE-SEM (Fig. 4). SEM picture of the Ag3VO4/Cu-MOF indicates Ag3VO4 particles a long with plentiful number of agglomerated MOF nanoparticles (Fig. 4a). Fig. 4b demonstrates SEM picture of the Cu-MOF incorporated with rGO nanosheets. It is obvious from Fig. 4c that Ag3VO4 particles were successfully introduced to the Cu-MOF/rGO
3. Results and discussion 3.1. Characterization of materials The FT-IR spectra of as-synthesized nanocomposites and pure materials are depicted in Fig. 1. Two characteristic peaks of COO- at 1300 cm−1 and 1600 cm−1 are visible in the FT-IR spectra of Cu-MOF and Cu-MOF/rGO. The peaks located approximately at 1650 cm−1 and 2920 cm−1 are ascribed to C]O and C–H vibration, respectively [22]. The FT-IR spectra of Ag3VO4 and Ag3VO4/Cu-MOF/rGO nanocomposite, are shown two strong absorption peaks at about 740 cm-1 and 2
Materials Research Bulletin 121 (2020) 110621
E. Akbarzadeh, et al.
solvated Cu(tpa). (dmf) to desolvated Cu(tpa) [40,42]. The mass change after 300 ℃ indicates pyrolysis of the Cu-MOF/rGO composite. UV-vis diffuse reflectance spectroscopy of Ag3VO4 and Ag3VO4/CuMOF/rGO at divers light wavelength was measured to study the optical response (Fig. 7). Pure Ag3VO4 illustrates strong photo-absorption in visible light with the absorption edge around 600 nm. DRS results of the Ag3VO4/Cu-MOF/rGO nanocomposite demonstrate a red shift in absorption edge compared to pure Ag3VO4. Electrochemical impedance spectroscopy results have been used to study the charge transfer resistance of the materials (Fig. 8). Nyquist plots of the materials were recorded in the presence of 5 mM K3[Fe (CN)6] : K4[Fe(CN)6] (1:1) mixture containing 0.1 M KCl. EIS results indicated that Ag3VO4/Cu-MOF/rGO has lower charge transfer resistance than Cu-MOF/rGO and pure Ag3VO4. These results highlight an increased interfacial electron transport in the Ag3VO4/Cu-MOF/rGO nanocomposites. Fig. 3. XRD patterns of the prepared materials.
3.2. Photocatalytic performance of the catalysts
nanocomposite. The EDX elemental mapping of the Ag3VO4/Cu-MOF/ rGO indicates presence of O, Cu, C, Ag and V elements in the nanocomposite (Fig. 4d). Fig. 5 demonstrates BET surface area of Cu-MOF/rGO (a) Ag3VO4 (b) and Ag3VO4/Cu-MOF/rGO (c) which were acquired from nitrogen adsorption and desorption isotherms analysis at 77 K. The BET surface areas were obtained to be 16.25, 3.59 and 5.63 m2/g for Cu-MOF/rGO, Ag3VO4 and Ag3VO4/Cu-MOF/rGO, respectively. Comparison between Ag3VO4 and Ag3VO4/Cu-MOF/rGO demonstrated increased surface area of nanocomposite. Thermogravimetric analysis results of the prepared materials in N2 atmosphere are indicated in Fig. 6. Primary weight lost about 100 ℃ in TGA curve of GO is caused by the evaporation of surface water molecules and secondary mass lost at 150–300 ℃ originated from decomposition of surface oxygen groups in GO. In the TGA plots of Ag3VO4/ Cu-MOF/rGO and Cu-MOF/rGO, the weight losses before 300 ℃ are mainly due to the removal of the water molecules and transformation of
Photodegradation of organic dyes was chosen as an example reaction to evaluate catalytic activity of Ag3VO4 and Ag3VO4/Cu-MOF/rGO nanocomposite. Langmuir-Hinshelwood (L-H) kinetics model dC (r = − dt = kapp C ) was applied to investigate the kinetic of photocatalytic reactions and account the linear simulation of AB92 degradation. The rate coefficients of AB92 degradation over the photocatalysts were obtained by plot of ln (C/C0) versus time. C0 and C introduce concentration of dye molecules before beginning the reaction and t min after light irradiation, respectively (Fig. 9). The experimental results indicated that in the absence of any catalyst under visible light irradiation, AB92 is approximately stable. The Ag3VO4/Cu-MOF/rGO nanocomposite illustrated remarkable progress in photocatalytic degradation of AB92 than pure Ag3VO4 and Ag3VO4/ Cu-MOF under visible light irradiation. The degradation rate constant of the Ag3VO4/Cu-MOF/rGO nanocomposite (0.008 min−1) is higher by a coefficient of 2.5 and 4.7 compare to pure Ag3VO4 (0.0032 min−1) and Cu-MOF/rGO
Fig. 4. FESEM pictures of Ag3VO4/Cu-MOF (a) Cu-MOF/rGO (b) Ag3VO4/Cu-MOF/rGO (c) and EDX elemental mapping of nanocomposite (d). 3
Materials Research Bulletin 121 (2020) 110621
E. Akbarzadeh, et al.
Fig. 5. N2 adsorption/desorption isotherm of the prepared materials. Pore size distributions of samples (inset) calculated by the BJH method.
Fig. 6. TGA curves of the prepared materials. Fig. 7. UV–vis diffuse-reflectance spectra of Ag3VO4 and Ag3VO4/Cu-MOF/ rGO.
(0.0017 min−1) respectively. These results revealed that combination of the Ag3VO4 nanoparticles with Cu-MOF/rGO substantially enhances the photocatalytic activity. The superior photocatalytic performance can be attributed to the increased surface area and enhancement of interfacial electron transfer and charge carrier separation. To study the weight percentage ratio of Ag3VO4 and Cu-MOF/rGO effect on the catalytic activity, composites with different amount of CuMOF/rGO were prepared (Fig. 10). The best catalytic performance was observed when the weight percentage ratio of Ag3VO4 and Cu-MOF/ rGO was 90:10 with kapp =0.008 min−1. Apparent rate constants were
obtained to be 0.0068 min-1 and 0.0044 min-1 for 85% Ag3VO4/CuMOF/rGO and 95% Ag3VO4/Cu-MOF/rGO, respectively. In order to study the stability of as-synthesized nanocomposite, three consecutive cycles of photocatalytic AB92 degradation were performed using the retrieved Ag3VO4/Cu-MOF/rGO. After the third photoreaction run, catalytic activity of the nanocomposite was decreased to about 70% efficiency of the first run, indicating that stability of Ag3VO4/Cu-MOF/rGO is almost acceptable. It should be noted that 4
Materials Research Bulletin 121 (2020) 110621
E. Akbarzadeh, et al.
Fig. 8. Electrochemical impedance spectroscopy (Nyquist plots) of the materials.
Fig. 10. Plot of ln(C/C0) for AB92 degradation in the presence of different nanocomposites.
Ag-based photocatalysts are not so stable in visible light irradiation.
3.3. Possible photocatalytic mechanism It is appealing to consider the probable reaction mechanism for the photocatalytic performance of the Ag3VO4/Cu-MOF/rGO nanocomposite in AB92 photodegradation. The main reactive species that contribute in degradation process are O•2−, HO•2 and OH•. These active radicals produce by photo-induced electrons and holes that combine with pre-adsorbed H2O/OH− on the surface of photocatalyst and available oxygen in the solution [43]. Several scavengers (t-BuOH, CH3OH, iodide ion and p-benzoqinone) were added to the initial dye solution to investigate the role of reactive species which directly taking part in AB92 degradation process in the presence of Ag3VO4/Cu-MOF/rGO nanocomposite. As observed in Fig. 11, experimental results demonstrated that the photo-degradation of AB92 molecules was almost inhibited in the presence of p-benzoqinone. These results prove that O•2− plays the main role in the degradation of AB92 molecules. Whereas, the photo-degradation of AB92 was remarkably increased in the presence of CH3OH, indicating that the holes do not have any major role in dye degradation. In fact, CH3OH reduced the electrons – holes recombination and then increased photodegradation of dye molecules. However, by addition of KI and t-BuOH as OH• scavenger in dye solution the degradation of dye molecules was almost invariable. On the basis of the obtained results from the application of inorganic compounds as scavenger, it is obvious that O•2− is the most important active species in AB92 photo-degradation in the presence of Ag3VO4/Cu-MOF/rGO
Fig. 11. The effect of various scavengers in the degradation of dye molecules over Ag3VO4/Cu-MOF/rGO.
catalyst. According to the experimental results a probable photocatalytic mechanism of dye degradation in the presence of Ag3VO4/Cu-MOF/ rGO was proposed as illustrated in Scheme. 1. In the nanocomposite, Ag3VO4 particles were applied as photoelectron donor and rGO was used as the charge carrier from Ag3VO4 to Cu-MOF as well as
Fig. 9. Plot of C/C0 (a) and ln(C/C0) (b) for AB92 photodegradation in the presence of different catalysts. 5
Materials Research Bulletin 121 (2020) 110621
E. Akbarzadeh, et al.
Scheme 1. Proposed photocatalytic mechanism and charge transfer scheme of the Ag3VO4/Cu-MOF/rGO under visible light irradiation.
supporting matrix for Ag3VO4 and Cu-MOF.
[14] L. Zhang, Y. He, P. Ye, W. Qin, Y. Wu, T. Wu, Enhanced photodegradation activity of Rhodamine B by Co3O4/Ag3VO4 under visible light irriadiation, Mater. Sci. Eng. B 178 (2013) 45–52. [15] K. Wangkawong, S. Phanichphant, D. Tantraviwat, B. Inceesungvorn, CoTiO3/ Ag3VO4 composite: a study on the role of CoTiO3 and the active species in the photocatalytic degradation of methylene blue, J. Colloid Interface Sci. 454 (2015) 210–215. [16] R. Ran, X. Meng, Z. Zhang, Facile preparation of novel graphene oxide-modified Ag2O/Ag3VO4/AgVO3 composites with high photocatalytic activities under visible light irradiation, Appl. Catal. B 196 (2016) 1–15. [17] R. Ran, J.G. McEvoy, Z. Zhang, Ag2O/Ag3VO4/Ag4V2O7 heterogeneous photocatalyst prepared by a facile hydrothermal synthesis with enhanced photocatalytic performance under visible light irradiation, Mater. Res. Bull. 74 (2016) 140–150. [18] F. Kiantazh, A. Habibi-Yangjeh, Ag3VO4/ZnO nanocomposites with an n–n heterojunction as novel visible-light-driven photocatalysts with highly enhanced activity, Mater. Sci. Semicond. Process. 39 (2015) 671–679. [19] Y.-B. Huang, J. Liang, X.-S. Wang, R. Cao, Multifunctional metal–organic framework catalysts: synergistic catalysis and tandem reactions, Chem. Soc. Rev. 46 (2017) 126–157. [20] H.-Y. Zhang, X.-P. Hao, L.-P. Mo, S.-S. Liu, W.-B. Zhang, Z.-H. Zhang, A magnetic metal–organic framework as a highly active heterogeneous catalyst for one-pot synthesis of 2-substituted alkyl and aryl (indolyl) kojic acid derivatives, New J. Chem. 41 (2017) 7108–7115. [21] E. Akbarzadeh, H.Z. Soheili, M.R. Gholami, Novel Cu2O/Cu-MOF/rGO is reported as highly efficient catalyst for reduction of 4-Nitrophenol, Mater. Chem. Phys. (2019) 121846. [22] E. Akbarzadeh, M. Falamarzi, M.R. Gholami, Synthesis of M/CuO (M= Ag, Au) from Cu based Metal Organic Frameworks for efficient catalytic reduction of pnitrophenol, Mater. Chem. Phys. 198 (2017) 374–379. [23] C.-C. Wang, J.-R. Li, X.-L. Lv, Y.-Q. Zhang, G. Guo, Photocatalytic organic pollutants degradation in metal–organic frameworks, Energy Environ. Sci. 7 (2014) 2831–2867. [24] J. Qiu, L. Yang, M. Li, J. Yao, Metal nanoparticles decorated MIL-125-NH2 and MIL125 for efficient photocatalysis, Mater. Res. Bull. 112 (2019) 297–306. [25] Y. Fu, D. Sun, Y. Chen, R. Huang, Z. Ding, X. Fu, Z. Li, An amine‐functionalized titanium metal–Organic framework photocatalyst with visible‐light‐Induced activity for CO2 reduction, Angew. Chemie Int. Ed. 51 (2012) 3364–3367. [26] R. Lin, L. Shen, Z. Ren, W. Wu, Y. Tan, H. Fu, J. Zhang, L. Wu, Enhanced photocatalytic hydrogen production activity via dual modification of MOF and reduced graphene oxide on CdS, Chem. Commun. 50 (2014) 8533–8535. [27] S. Abedi, A. Morsali, Ordered mesoporous metal–organic frameworks incorporated with amorphous TiO2 as photocatalyst for selective aerobic oxidation in sunlight irradiation, ACS Catal. 4 (2014) 1398–1403. [28] N. Mohaghegh, M. Tasviri, E. Rahimi, M. Gholami, Comparative studies on Ag3PO4/BiPO4–metal-organic framework–graphene-based nanocomposites for photocatalysis application, Appl. Surf. Sci. 351 (2015) 216–224. [29] T. Zeng, X. Zhang, S. Wang, H. Niu, Y. Cai, Spatial confinement of a Co3O4 catalyst in hollow metal–organic frameworks as a nanoreactor for improved degradation of organic pollutants, Environ. Sci. Technol. 49 (2015) 2350–2357. [30] L. Hu, G. Deng, W. Lu, S. Pang, X. Hu, Deposition of CdS nanoparticles on MIL-53 (Fe) metal-organic framework with enhanced photocatalytic degradation of RhB under visible light irradiation, Appl. Surf. Sci. 410 (2017) 401–413. [31] S.G. Khasevani, M. Gholami, Engineering a highly dispersed core@ shell structure for efficient photocatalysis: a case study of ternary novel BiOI@ MIL-88A (Fe)@ gC3N4 nanocomposite, Mater. Res. Bull. 106 (2018) 93–102. [32] G. Xu, H. Zhang, J. Wei, H.-X. Zhang, X. Wu, Y. Li, C. Li, J. Zhang, J. Ye, Integrating the g-C3N4 nanosheet with B–H bonding decorated metal–Organic framework for CO2 activation and photoreduction, ACS Nano (2018). [33] X. Zhang, Y. Yang, W. Huang, Y. Yang, Y. Wang, C. He, N. Liu, M. Wu, L. Tang, gC3N4/UiO-66 nanohybrids with enhanced photocatalytic activities for the oxidation of dye under visible light irradiation, Mater. Res. Bull. 99 (2018) 349–358. [34] X. Hao, Z. Jin, H. Yang, G. Lu, Y. Bi, Peculiar synergetic effect of MoS2 quantum dots and graphene on Metal-Organic Frameworks for photocatalytic hydrogen evolution, Appl. Catal. B 210 (2017) 45–56. [35] L. Yang, C. Xu, F. Wan, H. He, H. Gu, J. Xiong, Synthesis of RGO/BiOI/ZnO composites with efficient photocatalytic reduction of aqueous Cr (VI) under visible-light irradiation, Mater. Res. Bull. 112 (2019) 154–158.
4. Conclusion In present study, Cu-MOF/rGO was applied as a favorable cocatalyst to improve photocatalytic activity of the Ag3VO4 particles. Experimental results asserted that the as synthesized Ag3VO4/Cu-MOF/ rGO composite displayed improved catalytic activity in photo-degradation of dye molecules. The main reason for this enhancement can be attributed to the migration of photogenerated electron between Ag3VO4 and Cu-MOF through rGO nanosheets. Usage of inorganic compounds as scavenger demonstrated that O•2− was the major reactive species in dye degradation in the presence of Ag3VO4/Cu-MOF/rGO photocatalyst. Acknowledgments The authors gratefully acknowledge the Iran National Science Foundation for financial support (INSF no.96016238). References [1] T. Di, B. Zhu, B. Cheng, J. Yu, J. Xu, A direct Z-scheme g-C3N4/SnS2 photocatalyst with superior visible-light CO2 reduction performance, J. Catal. 352 (2017) 532–541. [2] E. Akbarzadeh, M.R. Gholami, Pt–NiO–Al2O3/G derived from graphene-supported layered double hydroxide as efficient catalyst for p-nitrophenol reduction, Res. Chem. Intermed. 43 (2017) 5829–5839. [3] S.M. El-Sheikh, T.M. Khedr, A. Hakki, A.A. Ismail, W.A. Badawy, D.W. Bahnemann, Visible light activated carbon and nitrogen co-doped mesoporous TiO2 as efficient photocatalyst for degradation of ibuprofen, Sep. Purif. Technol. 173 (2017) 258–268. [4] J. Zhang, Z. Ma, Flower-like Ag3VO4/BiOBr np heterojunction photocatalysts with enhanced visible-light-driven catalytic activity, Mol. Catal. 436 (2017) 190–198. [5] M. Kang, J. Liang, F. Wang, X. Chen, Y. Lu, J. Zhang, Structural design of hexagonal/monoclinic WO3 phase junction for photocatalytic degradation, Mater. Res. Bull. (2019) 110614. [6] M. You, J. Pan, C. Chi, B. Wang, W. Zhao, C. Song, Y. Zheng, C. Li, The visible light hydrogen production of the Z-Scheme Ag3PO4/Ag/g-C3N4 nanosheets composites, J. Mater. Sci. 53 (2018) 1978–1986. [7] P. Sánchez-Cid, C. Jaramillo-Páez, J. Navío, A. Martín-Gómez, M. Hidalgo, Coupling of Ag2CO3 to an optimized ZnO photocatalyst: advantages vs. Disadvantages, J. Photochem. Photobiol. A: Chem. (2018). [8] S. Le, W. Li, Y. Li, B. Borjigin, G. Li, X. Wang, Tetracycline Removal Under Solar Illumination Over Ag3VO4/mpg‐C3N4 Heterojunction Photocatalysts, Photochem. Photobiol. (2018). [9] H. Wang, L. Zou, Y. Shan, X. Wang, Ternary GO/Ag3PO4/AgBr composite as an efficient visible-light-driven photocatalyst, Mater. Res. Bull. 97 (2018) 189–194. [10] J. Zhang, Z. Ma, Ag3VO4/AgI composites for photocatalytic degradation of dyes and tetracycline hydrochloride under visible light, Mater. Lett. 216 (2018) 216–219. [11] J. Barzegar, A. Habibi-Yangjeh, A. Akhundi, S. Vadivel, Novel ternary g-C3N4/ Ag3VO4/AgBr nanocomposites with excellent visible-light-driven photocatalytic performance for environmental applications, Solid State Sci. 78 (2018) 133–143. [12] E. Akbarzadeh, S.R. Setayesh, M.R. Gholami, Synthesis of the visible-light-driven Ag 3 VO 4/Ag 3 PO 4/Ag photocatalysts with enhanced photocatalytic activity, RSC Adv. 6 (2016) 14909–14915. [13] T. Zhu, Y. Song, H. Ji, Y. Xu, Y. Song, J. Xia, S. Yin, Y. Li, H. Xu, Q. Zhang, Synthesis of g-C3N4/Ag3VO4 composites with enhanced photocatalytic activity under visible light irradiation, Chem. Eng. J. 271 (2015) 96–105.
6
Materials Research Bulletin 121 (2020) 110621
E. Akbarzadeh, et al.
[40] C.G. Carson, K. Hardcastle, J. Schwartz, X. Liu, C. Hoffmann, R.A. Gerhardt, R. Tannenbaum, Synthesis and structure characterization of copper terephthalate metal–organic frameworks, Eur. J. Inorg. Chem. 2009 (2009) 2338–2343. [41] J. Ren, Y. Wu, Y. Dai, D. Sha, J. Pan, M. Chen, J. Wang, Q. Wang, N. Ye, X. Yan, Preparation and characterization of graphitic C 3 N 4/Ag 3 VO 4 with excellent photocatalytic performance under visible light irradiation, J. Mater. Sci. Mater. Electron. 28 (2017) 641–651. [42] S. He, Z. Li, L. Ma, J. Wang, S. Yang, Graphene oxide-templated growth of MOFs with enhanced lithium-storage properties, New J. Chem. 41 (2017) 14209–14216. [43] Z. He, Y. Shi, C. Gao, L. Wen, J. Chen, S. Song, BiOCl/BiVO4 p–n heterojunction with enhanced photocatalytic activity under visible-light irradiation, J. Phys. Chem. C 118 (2013) 389–398.
[36] M.-Q. Yang, Y.-J. Xu, Basic principles for observing the photosensitizer role of graphene in the graphene–semiconductor composite photocatalyst from a case study on graphene–ZnO, J. Phys. Chem. C 117 (2013) 21724–21734. [37] N. Tian, H. Huang, Y. He, Y. Guo, T. Zhang, Y. Zhang, Mediator-free direct Z-scheme photocatalytic system: BiVO 4/gC 3 N 4 organic–inorganic hybrid photocatalyst with highly efficient visible-light-induced photocatalytic activity, J. Chem. Soc. Dalton Trans. 44 (2015) 4297–4307. [38] Y. Jin, C. Zhao, Z. Sun, Y. Lin, L. Chen, D. Wang, C. Shen, Facile synthesis of FeMOF/RGO and its application as a high performance anode in lithium-ion batteries, RSC Adv. 6 (2016) 30763–30768. [39] X. He, W.-N. Wang, Pressure-regulated synthesis of Cu (TPA)·(DMF) in microdroplets for selective CO 2 adsorption, J. Chem. Soc. Dalton Trans. 48 (2019) 1006–1016.
7