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Carbon-modified bismuth titanate with an enhanced photocatalytic activity under nature sunlight
Materials Letters 172 (2016) 184–187
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Carbon-modified bismuth titanate with an enhanced photocatalytic activity under nature sunlight Jian Chen a, Weigang Mei a, Chao Liu c, Chenhui Hu b, Qianjing Huang a, Ningna Chen b, Jing Chen a,n, Rong Zhang a, Wenhua Hou b,n a
College of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing 211816, PR China Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, PR China c School of Materials Engineering, Yancheng Institute of Technology, Yancheng 224051, PR China b
art ic l e i nf o
a b s t r a c t
Article history: Received 12 January 2016 Received in revised form 20 February 2016 Accepted 1 March 2016 Available online 2 March 2016
A novel carbon-modified bismuth titanate Bi4Ti3O12 (C/BTO) nanocomposites were successfully synthesized by a facile co-precipitation method. The resulted samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopic (XPS), N2 adsorption–desorption and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). The photocatalytic activities of the samples were measured through the photocatalytic degradation of methyl orange (MO) aqueous solution under sunlight. Compared with commercial P25, the resulted C/BTO showed an excellent photocatalytic activity. The mechanism for the improved photocatalytic activity was finally proposed. & 2016 Elsevier B.V. All rights reserved.
Keywords: Bismuth titanate Carbon modified Nanocomposites Photocatalysis Solar energy materials
1. Introduction As a new water treatment method, the photocatalytic technology has attracted special attention due to its potential application in the degradation of organic wastewater [1]. With the properties of stability, nontoxicity, low cost, high photocatalytic activity and so on, TiO2 as a photocatalyst has been most widely investigated. However, the wide gap (3.0–3.2 eV) makes TiO2 only be excited under UV light irradiation that is about 4% of solar light, which limits its practical application. To take the advantage of the visible light which is the most composition of solar energy (nearly 45%), exploring new visible light catalysts has become a focus in the photocatalytic field [2–4]. Recently, the novel Bi-based semiconductor materials have drawn greater concern for their high photocatalytic activity [5]. The hybridized 6 s2 of Bi3 þ and O 2p make a new valence band which can reduce the band gap, therefore, most of Bi3 þ – containing semiconductor compounds have a narrow band gap and good photocatalytic activity [6]. Bismuth titanate (Bi4Ti3O12, abbreviated as BTO), a kind of layered perovskite compounds, is composed of alternatively stacking of (Bi2O2)2 þ layers and perovskite-like (Bi2Ti3O10)2 blocks along the c axis. It has been n
Corresponding authors. E-mail addresses: [email protected] (J. Chen), [email protected] (W. Hou).
http://dx.doi.org/10.1016/j.matlet.2016.03.002 0167-577X/& 2016 Elsevier B.V. All rights reserved.
widely explored for potential applications in optical displays, ferroelectric, and optoelectronic devices [7]. In recent years, Bi4Ti3O12 has been found to possess the ability of degrading organic pollutants and splitting water [8,9]. In addition, it has a high photocatalytic activity under visible-light [7]. Many fabrication techniques of crystalline Bi4Ti3O12 have been reported, such as chemical solution decomposition, solid-state reaction, hydrothermal synthesis, and so on [10]. However, Bi4Ti3O12 exhibits a low capability for the separation of electron-hole pairs and the photocatalytic activity of pure Bi4Ti3O12 is still far from practical application [11]. Studies have shown that carbon with the wide visible light absorption at a wavelength of 400–800 nm can enhance the photocatalytic activity and its high adsorption of organic pollutants can facilitate the interface reaction of photocatalysis [12]. For example, Ouyang et al. synthesized carbon doped ZnO composites with a porous structure which exhibited an excellent photocatalytic activity of RhB under solar-light irradiation [13]. Xiong et al. reported an in situ synthesis of C-doped (BiO)2CO3 hierarchical microspheres which exhibited an enhanced visible light photocatalytic activity toward the removal of NO compared with the undoped (BiO)2CO3, C-doped TiO2 and N-doped (BiO)2CO3 [14]. Using hydrothermal and calcination method, Li et al. synthesized C-Bi2WO6 which could totally decompose RhB in 4 h under visible light [15].
J. Chen et al. / Materials Letters 172 (2016) 184–187
Herein, we report a facile synthesis of C/BTO and its photocatalytic activity for the degradation of MO under nature sunlight. The structure, morphology, and other characteristics are investigated in details. In addition, the degradation mechanism is also discussed.
2. Experimental All the chemicals were of analytical grade and used as received without further purification. Detailed synthesis process, characterization means and photocatalytic evaluation were given in the Supplementary information (SI).
3. Results and discussion The layered structure and crystallinity of the resulting samples (BTO, H þ /BTO and C/BTO) were characterized by XRD. As shown in Fig. 1a, the XRD pattern of the as-prepared BTO matches well with the published data (JCPDS no. 35-0795) and the layered structure of BTO is clearly visible (Fig. 1c). After acidification and C modification, the characteristic (060) and (080) diffraction peaks of layered structure are disappeared, while the intensity of other main peaks is significantly reduced, indicating that the original ordered layered structure has been destroyed. From SEM image in Fig. 1d, we can see that C/BTO has no obvious ordered layered structure. Fig. 1b displays the FT-IR spectra of BTO, H þ /BTO and C/BTO. The bands at 790 cm 1 and 658 cm 1 in BTO are attributed
185
to the stretching vibrations of Bi-O and Ti-O [6]. After acidification and C modification, the intensity and peak width of these two peaks are changed, but the basic characteristics are remained. It demonstrates that the basic structure is not changed significantly, being consistent with the XRD results. The band at 1380 cm 1 in H þ /BTO is attributed to the vibration of NO bond which may be derived from the surface adsorbed NO3 . The peaks located at 1633 and 1693 cm 1 may belong to the characteristic absorptions of “C¼ O” [16], while the band at 1425 cm 1 is ascribed to “–COO ” [17]. Moreover, the surface chemical composition of C/BTO was also investigated by XPS analysis (Fig. S1). The survey spectrum shows the presence of Bi, Ti, O and C without other elements detected, and the C 1s spectrum shows two peaks. The peak at 284.2 eV may be assigned to the C-C bond with sp2 orbital, while the peak at 288.1 eV belongs to C ¼O bond of carbonate species [17]. All these evidence that C modification is successful. Accordingly, we suspect that the ethanol was oxidized by nitric acid to be carbonyl-containing species coated onto the surfaces of BTO. The nitrogen adsorption-desorption isotherms are shown in Fig. 2a. Both H þ /BTO and C/BTO present an obvious H3 hysteresis loop, indicating the presence of slit-like pore structure due to the stacking of plate-like particles [18]. By comparison, BTO has no apparent hysteresis loop, revealing that the sample is mainly nonporous. The BET surface area of BTO is only 8.9 m2/g. After acidification and C modification, the BET surface areas of H þ /BTO and C/BTO have greatly increased to 113.3 and 107.9 m2/g, respectively. The optical absorbance of the obtained samples was measured by UV–visible diffuse reflectance spectra. As shown in Fig. 2b, BTO
Fig. 1. XRD patterns (a) and FTIR spectra (b) of the relevant samples; SEM images of BTO (c) and C/BTO (d).
186
J. Chen et al. / Materials Letters 172 (2016) 184–187
Fig. 2. (a) N2 adsorption-desorption isotherms and (b) UV–vis diffuse reflectance spectra of samples.
has a relatively strong absorption in the UV region, but almost no absorption in the visible region of 400–800 nm. According to the position of the absorption edge, the band gap of BTO can be calculated to be 3.07 eV by the formula Eg ¼1240/λ, being consistent with previous literature [10]. After acidification and C modification, both H þ /BTO and C/BTO have a significantly enhanced absorption in UV region and a little increased absorption in visible region, the corresponding band gap is reduced to 2.98 and 2.88 eV, respectively. The photocatalytic activity of the as-prepared samples was evaluated by the degradation of organic contaminant MO in aqueous solution under sunlight. Fig. 3a shows the corresponding degradation curves of P25, BTO, H þ /BTO and C/BTO under sunlight. In the absence of catalyst, MO has no obvious degradation under sunlight, demonstrating that the autodegradation of MO can be ignored. BTO exhibits a low degradation efficiency of 8.0% after 3 h of solar illumination while the degradation rate of P25 is 65.5%. By comparison, H þ /BTO and C/BTO can reach 98.5% and 99.5% under the same conditions, being much better than BTO and P25. Besides, H þ /BTO and C/BTO have a very fast degradation rate of MO. Particularly, C/BTO exhibits the best photocatalytic activity as 99.5% of MO can be decomposed within 30 min under natural sunlight. Fig. 3b depicts the change in UV–vis spectra of MO solution at different time intervals by using C/BTO as photocatalyst. The intensity of the peak at 465 nm gradually decreases with the increasing of exposure time and is almost disappeared after 20 min. Fig. S2 illustrates the proposed degradation mechanism of
MO over C/BTO. The high sunlight photocatalytic activity of C/BTO may result from the synergetic effect of a larger surface area and the effective separation of electron-hole pairs.
4. Conclusions We successfully synthesized layered Bi4Ti3O12 by using a coprecipitation method, through acidification and C modification, the resulted two samples, H þ /BTO and C/BTO, have a much better photocatalytic activity of degrading MO than commercial P25 under sunlight. Especially, C/BTO can degrade nearly 99.5% MO within 30 min under sunlight by the synergistic effect of a high surface area and the effective separation of electron-hole pairs. These results indicate that C/BTO composites are promising candidate materials for wastewater treatment.
Acknowledgments The authors greatly appreciate the financial support of the Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP, 20130091110010), Natural Science Foundation of Jiangsu Province (BK2011438), National Science Fund for Talent Training in Basic Science (No. J1103310), National Basic Research Program (973 Project) (No. 2009CB623504), and the Modern Analysis Center of Nanjing University (No. 20150305).
Fig. 3. (a) MO degradation curves over different photocatalysts under sunlight, and (b) UV–vis spectra of the degraded MO solution over C/BTO.
J. Chen et al. / Materials Letters 172 (2016) 184–187
Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.matlet.2016.03.002.
References [1] C.S. Pan, J. Xu, Y.J. Wang, D. Li, Y.F. Zhu, Adv. Funct. Mater. 22 (2012) 1518–1524. [2] J.J. Sun, X.Y. Li, Q.D. Zhao, J. Ke, D.J. Zhang, C Phys. Chem. 118 (2014) 10113–10121. [3] C.L. Yu, G. Li, S. Kumar, K. Yang, R.C. Jin, Adv. Mater. 26 (2014) 892–898. [4] W.J. Zhou, Y.H. Leng, D.M. Hou, H.D. Li, L.G. Li, G.Q. Li, et al., Nanoscale 6 (2014) 4698–4704. [5] H.F. Cheng, B.B. Huang, Y. Dai, Nanoscale 6 (2014) 2009–2026. [6] Z.W. Chen, H. Jiang, W.L. Jin, C.K. Shi, Appl. Catal. B 180 (2016) 698–706. [7] H.Q. He, J. Yin, X.Y. Li, Y. Zhang, H.S. Qiu, J.B. Xu, et al., Appl. Catal. B 156–157
187
(2014) 35–43. [8] W.F. Yao, X.H. Xu, H. Wang, J.T. Zhou, X.N. Yang, Y. Zhang, et al., Appl. Catal. B 52 (2004) 109–116. [9] H.J. Zhang, G. Chen, X. Li, Solid State Ion. 180 (2009) 1599–1603. [10] X. Lin, Q.F. Guan, T.T. Liu, Y. Zhang, C.J. Zou, Acta Phys. Chim. Sin. 29 (2) (2013) 411–417. [11] W. Zhao, Y. Jin, C.H. Gao, W. Gu, Z.M. Jin, Y.L. Lei, L.S. Liao, Mater. Chem. Phys. 143 (2014) 952–962. [12] M.Y. Zhang, C.L. Shao, X.H. Li, P. Zhang, Y.Y. Sun, C.Y. Su, et al., Nanoscale 4 (2012) 7501–7508. [13] H.B. Ouyang, J.F. Huang, C.Y. Li, L.Y. Cao, J. Fei, Mater. Lett. 111 (2013) 217–220. [14] T. Xiong, H.W. Huang, Y.J. Sun, F. Dong, J. Mater. Chem. A 3 (2015) 6118–6127. [15] Y.Y. Li, J.P. Liu, X.T. Huang, J.G. Yu, Dalton Trans. 39 (2010) 3420–3425. [16] S.J. Zhu, Q.N. Meng, L. Wang, J.H. Zhang, Y.B. Song, H. Jin, et al., Angew. Chem. Int. Ed. 52 (2013) 3953–3957. [17] J. Di, J.X. Xia, M.X. Ji, H.P. Li, H. Xu, H.M. Li, et al., Nanoscale 7 (2015) 11433–11443. [18] F. Dong, Y.J. Sun, M. Fu, W.K. Ho, S.C. Lee, Z.B. Wu, Langmuir 28 (2012) 766–773.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Carbon-modified bismuth titanate with an enhanced photocatalytic activity under nature sunlight Jian Chen a, Weigang Mei a, Chao Liu c, Chenhui Hu b, Qianjing Huang a, Ningna Chen b, Jing Chen a,n, Rong Zhang a, Wenhua Hou b,n a
College of Chemistry and Molecular Engineering, Nanjing Tech University, Nanjing 211816, PR China Key Laboratory of Mesoscopic Chemistry of MOE, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, PR China c School of Materials Engineering, Yancheng Institute of Technology, Yancheng 224051, PR China b
art ic l e i nf o
a b s t r a c t
Article history: Received 12 January 2016 Received in revised form 20 February 2016 Accepted 1 March 2016 Available online 2 March 2016
A novel carbon-modified bismuth titanate Bi4Ti3O12 (C/BTO) nanocomposites were successfully synthesized by a facile co-precipitation method. The resulted samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopic (XPS), N2 adsorption–desorption and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). The photocatalytic activities of the samples were measured through the photocatalytic degradation of methyl orange (MO) aqueous solution under sunlight. Compared with commercial P25, the resulted C/BTO showed an excellent photocatalytic activity. The mechanism for the improved photocatalytic activity was finally proposed. & 2016 Elsevier B.V. All rights reserved.
Keywords: Bismuth titanate Carbon modified Nanocomposites Photocatalysis Solar energy materials
1. Introduction As a new water treatment method, the photocatalytic technology has attracted special attention due to its potential application in the degradation of organic wastewater [1]. With the properties of stability, nontoxicity, low cost, high photocatalytic activity and so on, TiO2 as a photocatalyst has been most widely investigated. However, the wide gap (3.0–3.2 eV) makes TiO2 only be excited under UV light irradiation that is about 4% of solar light, which limits its practical application. To take the advantage of the visible light which is the most composition of solar energy (nearly 45%), exploring new visible light catalysts has become a focus in the photocatalytic field [2–4]. Recently, the novel Bi-based semiconductor materials have drawn greater concern for their high photocatalytic activity [5]. The hybridized 6 s2 of Bi3 þ and O 2p make a new valence band which can reduce the band gap, therefore, most of Bi3 þ – containing semiconductor compounds have a narrow band gap and good photocatalytic activity [6]. Bismuth titanate (Bi4Ti3O12, abbreviated as BTO), a kind of layered perovskite compounds, is composed of alternatively stacking of (Bi2O2)2 þ layers and perovskite-like (Bi2Ti3O10)2 blocks along the c axis. It has been n
Corresponding authors. E-mail addresses: [email protected] (J. Chen), [email protected] (W. Hou).
http://dx.doi.org/10.1016/j.matlet.2016.03.002 0167-577X/& 2016 Elsevier B.V. All rights reserved.
widely explored for potential applications in optical displays, ferroelectric, and optoelectronic devices [7]. In recent years, Bi4Ti3O12 has been found to possess the ability of degrading organic pollutants and splitting water [8,9]. In addition, it has a high photocatalytic activity under visible-light [7]. Many fabrication techniques of crystalline Bi4Ti3O12 have been reported, such as chemical solution decomposition, solid-state reaction, hydrothermal synthesis, and so on [10]. However, Bi4Ti3O12 exhibits a low capability for the separation of electron-hole pairs and the photocatalytic activity of pure Bi4Ti3O12 is still far from practical application [11]. Studies have shown that carbon with the wide visible light absorption at a wavelength of 400–800 nm can enhance the photocatalytic activity and its high adsorption of organic pollutants can facilitate the interface reaction of photocatalysis [12]. For example, Ouyang et al. synthesized carbon doped ZnO composites with a porous structure which exhibited an excellent photocatalytic activity of RhB under solar-light irradiation [13]. Xiong et al. reported an in situ synthesis of C-doped (BiO)2CO3 hierarchical microspheres which exhibited an enhanced visible light photocatalytic activity toward the removal of NO compared with the undoped (BiO)2CO3, C-doped TiO2 and N-doped (BiO)2CO3 [14]. Using hydrothermal and calcination method, Li et al. synthesized C-Bi2WO6 which could totally decompose RhB in 4 h under visible light [15].
J. Chen et al. / Materials Letters 172 (2016) 184–187
Herein, we report a facile synthesis of C/BTO and its photocatalytic activity for the degradation of MO under nature sunlight. The structure, morphology, and other characteristics are investigated in details. In addition, the degradation mechanism is also discussed.
2. Experimental All the chemicals were of analytical grade and used as received without further purification. Detailed synthesis process, characterization means and photocatalytic evaluation were given in the Supplementary information (SI).
3. Results and discussion The layered structure and crystallinity of the resulting samples (BTO, H þ /BTO and C/BTO) were characterized by XRD. As shown in Fig. 1a, the XRD pattern of the as-prepared BTO matches well with the published data (JCPDS no. 35-0795) and the layered structure of BTO is clearly visible (Fig. 1c). After acidification and C modification, the characteristic (060) and (080) diffraction peaks of layered structure are disappeared, while the intensity of other main peaks is significantly reduced, indicating that the original ordered layered structure has been destroyed. From SEM image in Fig. 1d, we can see that C/BTO has no obvious ordered layered structure. Fig. 1b displays the FT-IR spectra of BTO, H þ /BTO and C/BTO. The bands at 790 cm 1 and 658 cm 1 in BTO are attributed
185
to the stretching vibrations of Bi-O and Ti-O [6]. After acidification and C modification, the intensity and peak width of these two peaks are changed, but the basic characteristics are remained. It demonstrates that the basic structure is not changed significantly, being consistent with the XRD results. The band at 1380 cm 1 in H þ /BTO is attributed to the vibration of NO bond which may be derived from the surface adsorbed NO3 . The peaks located at 1633 and 1693 cm 1 may belong to the characteristic absorptions of “C¼ O” [16], while the band at 1425 cm 1 is ascribed to “–COO ” [17]. Moreover, the surface chemical composition of C/BTO was also investigated by XPS analysis (Fig. S1). The survey spectrum shows the presence of Bi, Ti, O and C without other elements detected, and the C 1s spectrum shows two peaks. The peak at 284.2 eV may be assigned to the C-C bond with sp2 orbital, while the peak at 288.1 eV belongs to C ¼O bond of carbonate species [17]. All these evidence that C modification is successful. Accordingly, we suspect that the ethanol was oxidized by nitric acid to be carbonyl-containing species coated onto the surfaces of BTO. The nitrogen adsorption-desorption isotherms are shown in Fig. 2a. Both H þ /BTO and C/BTO present an obvious H3 hysteresis loop, indicating the presence of slit-like pore structure due to the stacking of plate-like particles [18]. By comparison, BTO has no apparent hysteresis loop, revealing that the sample is mainly nonporous. The BET surface area of BTO is only 8.9 m2/g. After acidification and C modification, the BET surface areas of H þ /BTO and C/BTO have greatly increased to 113.3 and 107.9 m2/g, respectively. The optical absorbance of the obtained samples was measured by UV–visible diffuse reflectance spectra. As shown in Fig. 2b, BTO
Fig. 1. XRD patterns (a) and FTIR spectra (b) of the relevant samples; SEM images of BTO (c) and C/BTO (d).
186
J. Chen et al. / Materials Letters 172 (2016) 184–187
Fig. 2. (a) N2 adsorption-desorption isotherms and (b) UV–vis diffuse reflectance spectra of samples.
has a relatively strong absorption in the UV region, but almost no absorption in the visible region of 400–800 nm. According to the position of the absorption edge, the band gap of BTO can be calculated to be 3.07 eV by the formula Eg ¼1240/λ, being consistent with previous literature [10]. After acidification and C modification, both H þ /BTO and C/BTO have a significantly enhanced absorption in UV region and a little increased absorption in visible region, the corresponding band gap is reduced to 2.98 and 2.88 eV, respectively. The photocatalytic activity of the as-prepared samples was evaluated by the degradation of organic contaminant MO in aqueous solution under sunlight. Fig. 3a shows the corresponding degradation curves of P25, BTO, H þ /BTO and C/BTO under sunlight. In the absence of catalyst, MO has no obvious degradation under sunlight, demonstrating that the autodegradation of MO can be ignored. BTO exhibits a low degradation efficiency of 8.0% after 3 h of solar illumination while the degradation rate of P25 is 65.5%. By comparison, H þ /BTO and C/BTO can reach 98.5% and 99.5% under the same conditions, being much better than BTO and P25. Besides, H þ /BTO and C/BTO have a very fast degradation rate of MO. Particularly, C/BTO exhibits the best photocatalytic activity as 99.5% of MO can be decomposed within 30 min under natural sunlight. Fig. 3b depicts the change in UV–vis spectra of MO solution at different time intervals by using C/BTO as photocatalyst. The intensity of the peak at 465 nm gradually decreases with the increasing of exposure time and is almost disappeared after 20 min. Fig. S2 illustrates the proposed degradation mechanism of
MO over C/BTO. The high sunlight photocatalytic activity of C/BTO may result from the synergetic effect of a larger surface area and the effective separation of electron-hole pairs.
4. Conclusions We successfully synthesized layered Bi4Ti3O12 by using a coprecipitation method, through acidification and C modification, the resulted two samples, H þ /BTO and C/BTO, have a much better photocatalytic activity of degrading MO than commercial P25 under sunlight. Especially, C/BTO can degrade nearly 99.5% MO within 30 min under sunlight by the synergistic effect of a high surface area and the effective separation of electron-hole pairs. These results indicate that C/BTO composites are promising candidate materials for wastewater treatment.
Acknowledgments The authors greatly appreciate the financial support of the Specialized Research Fund for the Doctoral Program of Higher Education (SRFDP, 20130091110010), Natural Science Foundation of Jiangsu Province (BK2011438), National Science Fund for Talent Training in Basic Science (No. J1103310), National Basic Research Program (973 Project) (No. 2009CB623504), and the Modern Analysis Center of Nanjing University (No. 20150305).
Fig. 3. (a) MO degradation curves over different photocatalysts under sunlight, and (b) UV–vis spectra of the degraded MO solution over C/BTO.
J. Chen et al. / Materials Letters 172 (2016) 184–187
Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.matlet.2016.03.002.
References [1] C.S. Pan, J. Xu, Y.J. Wang, D. Li, Y.F. Zhu, Adv. Funct. Mater. 22 (2012) 1518–1524. [2] J.J. Sun, X.Y. Li, Q.D. Zhao, J. Ke, D.J. Zhang, C Phys. Chem. 118 (2014) 10113–10121. [3] C.L. Yu, G. Li, S. Kumar, K. Yang, R.C. Jin, Adv. Mater. 26 (2014) 892–898. [4] W.J. Zhou, Y.H. Leng, D.M. Hou, H.D. Li, L.G. Li, G.Q. Li, et al., Nanoscale 6 (2014) 4698–4704. [5] H.F. Cheng, B.B. Huang, Y. Dai, Nanoscale 6 (2014) 2009–2026. [6] Z.W. Chen, H. Jiang, W.L. Jin, C.K. Shi, Appl. Catal. B 180 (2016) 698–706. [7] H.Q. He, J. Yin, X.Y. Li, Y. Zhang, H.S. Qiu, J.B. Xu, et al., Appl. Catal. B 156–157
187
(2014) 35–43. [8] W.F. Yao, X.H. Xu, H. Wang, J.T. Zhou, X.N. Yang, Y. Zhang, et al., Appl. Catal. B 52 (2004) 109–116. [9] H.J. Zhang, G. Chen, X. Li, Solid State Ion. 180 (2009) 1599–1603. [10] X. Lin, Q.F. Guan, T.T. Liu, Y. Zhang, C.J. Zou, Acta Phys. Chim. Sin. 29 (2) (2013) 411–417. [11] W. Zhao, Y. Jin, C.H. Gao, W. Gu, Z.M. Jin, Y.L. Lei, L.S. Liao, Mater. Chem. Phys. 143 (2014) 952–962. [12] M.Y. Zhang, C.L. Shao, X.H. Li, P. Zhang, Y.Y. Sun, C.Y. Su, et al., Nanoscale 4 (2012) 7501–7508. [13] H.B. Ouyang, J.F. Huang, C.Y. Li, L.Y. Cao, J. Fei, Mater. Lett. 111 (2013) 217–220. [14] T. Xiong, H.W. Huang, Y.J. Sun, F. Dong, J. Mater. Chem. A 3 (2015) 6118–6127. [15] Y.Y. Li, J.P. Liu, X.T. Huang, J.G. Yu, Dalton Trans. 39 (2010) 3420–3425. [16] S.J. Zhu, Q.N. Meng, L. Wang, J.H. Zhang, Y.B. Song, H. Jin, et al., Angew. Chem. Int. Ed. 52 (2013) 3953–3957. [17] J. Di, J.X. Xia, M.X. Ji, H.P. Li, H. Xu, H.M. Li, et al., Nanoscale 7 (2015) 11433–11443. [18] F. Dong, Y.J. Sun, M. Fu, W.K. Ho, S.C. Lee, Z.B. Wu, Langmuir 28 (2012) 766–773.