The Enhanced Photocatalytic Properties for Water Oxidation over Bi

Article pubs.acs.org/JPCC

The Enhanced Photocatalytic Properties for Water Oxidation over Bi/ BiVO4/V2O5 Composite Xiaofeng Xu, Shufang Kou, Xia Guo,* Xiaotong Li, Xiaojian Ma, and Hongzhi Mao Key Laboratory of Colloid and Interface Chemistry, Ministry of Education, School of Chemistry and Chemical Engineering, Shandong University, Jinan, Shandong 250100, China S Supporting Information *

ABSTRACT: Bi/BiVO4/V2O5 has been successfully synthesized by a simple annealing of BiVO4 in Ar/H2. The obtained Bi/BiVO4/V2O5 was characterized by X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The photocatalytic activities are examined by an oxygen-evolution reaction. When BiO/BiVO4/V2O5 in air and Bi2VO5.5/ BiVO4/V2O5 in vacuum were compared with the products annealing in other atmospheres, Bi/BiVO4/V2O5 exhibited the best performance (2413 μmol·g−1·h−1), which could be attributed to the synergistic combination of Bi, BiVO4, and V2O5. This study may open up a new avenue for the development of an efficient composite photocatalyst.

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INTRODUCTION Solar light is an abundant, decentralized, and inexhaustible natural resource which can be used for clean energy with minimal environmental impact.1,2 In recent years, the photocatalytic splitting of water into hydrogen and oxygen by semiconductor has been regarded as a promising strategy because of its renewable energy production without reliance on fossil fuels and no carbon dioxide emission.1,3 Water oxidation is the key step for water splitting. However, the conversion efficiency from solar energy to chemical energy is very low because the oxygen-evolution reaction (OER) is an endergonic reaction involving simultaneous transfer of four electrons.4,5 Thus, the discovery and design of highly efficient photocatalytic materials for OER are demanding and challenging. Many photocatalysts for water oxidation have been reported, but most of them have very low photocatalytic activities under solar light.6 The monoclinic phase of BiVO4 has attracted wide attention due to its special crystal, electronic, and optical properties.7 Furthermore, because of the overlapping between the Bi 6s and O 2p orbitals, as well as the Bi3+ lone-pair contribution, the bandgap of BiVO4 is very narrow.7,8 With the relatively small bandgap energy, the monoclinic BiVO4 can effectively absorb visible light.7−9 In addition, BiVO4 is an ideal photocatalytic material for its low cost, nontoxic nature, and favorable stability.2 However, the conversion efficiency from solar energy to chemical energy of BiVO4 is still quite low because it suffers from many drawbacks, such as low chargeseparation efficiency and slow kinetics for oxygen evolution.7−10 Fortunately, in recent years, many significant breakthroughs have been made for BiVO4-based photocatalytic materials. © 2017 American Chemical Society

Combination with semiconductor and deposition with metal are two predominant methods. First, the combination with a semiconductor that has different band gap energy can improve the absorption ability of solar light.11−18 Vanadium pentoxide (V2O5) is a good choice to improve the absorption ability due to its unique energy band gap (2.3 eV).19−24 For example, Sun et al.18 synthesized a novel V2O5/BiVO4/TiO2 composite photocatalyst using a sequentially hydrothermal and adhering method, which shows that the multiple interfaces among different semiconductors enhance the separation efficiency of the photoinduced charge carriers and improve the photocatalytic performance. However, the application of amorphous V2O5 in the photocatalytic area has yet to be reported. Second, metal nanoparticles, such as Au, Ag, Pt, and Bi can enhance the separation efficiency and electron-transfer rate of semiconductor photocatalysts by forming surface plutonic metallic nanostructures.25−33 Feng et al.33 fabricated novel p−n heterojunctions of BiOCl/BiVO4 nanosheets deposited with metallic Bi via a one-step method, which illustrates that Bi plays a crucial role in enhancing the photocatalytic performance of BiVO4. Up to now, many related studies have been performed to improve the photocatalytic properties of BiVO4, but few have combined these two effective methods in one system. In this study, a Bi/BiVO4/V2O5 composite system was constructed by a facile method to overcome the poor chargeseparation yield. More importantly, the as-prepared Bi/BiVO4/ V2O5 composite exhibits superior photocatalytic and photoReceived: April 2, 2017 Revised: July 8, 2017 Published: July 11, 2017 16257

DOI: 10.1021/acs.jpcc.7b03119 J. Phys. Chem. C 2017, 121, 16257−16265

Article

The Journal of Physical Chemistry C

Figure 1. XRD patterns of as-prepared (a) BiVO4, (b) H-450, (c) A-450, and (d) V-450. Raman spectra of BiVO4, H-450, A-450, V-450, and V2O5 in a range of (e) 50−1200 cm−1 and (f) 50−500 cm−1.

furnace. BiVO4 was annealed in an argon−hydrogen atmosphere (Ar−H2, 5% of H2) for 10 min in a range of temperatures between 300 and 500 °C. All of the samples were heated to the desired temperatures at a rate of 10 °C/min. After 10 min, they were cooled to room temperature at a rate of 7 °C/min. These samples were denoted as H-t, where t stands for the temperature in the corresponding annealing treatment. For example, H-450 was obtained by annealing BiVO4 in Ar−H2 at 450 °C for 10 min. For the sake of brevity, the products of BiVO4 annealed at 450 °C for 10 min in vacuum and air atmosphere were denoted as V-450 and A-450, respectively. Characterization. The XRD patterns of BiVO4 were obtained on an X-ray powder diffractometer (Bruker D8 Advance, Germany) equipped with a rotating anode, using the monochromatic Cu Kα as the radiation source. The working voltage and current of the diffractometer were kept at 40 kV and 40 mA, respectively. The Raman spectra were measured by a microscopic confocal Raman spectrometer (Renishaw plc, U.K.). The X-ray photoelectron spectroscopy (XPS) analysis was performed with an ESCALAB 250 spectrometer (ThermoFisher Scientific, U.S.A.), using the radiation of Al KR line as the excitation source. The binding energy was calibrated using the C 1s photoelectron peak at 284.6 eV as the reference. The photoluminescence (PL) spectra were achieved from an LS-55 fluorescence spectrophotometer (PerkinElmer, U.S.A.) at a rate of 10−1500 nm/min. The PL spectra were recorded in the range of 380−700 nm at room temperature at the excitation wavelength of 310 nm. The TEM images were recorded by a transmission electron microscope (JEM-1011, Japan) at an accelerating voltage of 100 kV. The elemental maps and high-

electrochemical properties, in comparison to the other asprepared materials (BiVO4, Bi2VO5.5/BiVO4/V2O5, and BiO/ BiVO4/V2O5). Our results demonstrate that the metallic Bi improves the quantity and transfer rate of the photoinduced charge carriers, enhancing the photocatalytic activity of Bi/ BiVO4/V2O5. In addition, for BiVO4 catalyst, combination with V2O5 enhances the separation of electron−hole pairs.

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EXPERIMENTAL SECTION Materials. Bismuth(III) nitrate pentahydrate (Bi(NO)3· 5H2O, 99.0%), ammonium metavanadate (NH4VO3, 99.0%), and N,N-dimethylformamide (C3H7NO, 99.5%) were purchased from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). Crystalline V2O5 used in Raman measurement was also purchased from Sinopharm Chemical Reagent Co. Ltd. All reagents were used without any further purification. Synthesis of BiVO4 Photocatalyst. A total of 1 mmol of NH4VO3 was dispersed into 10 mL of deionized (DI) water, and then the suspension was added dropwise into a 30 mL DMF solution containing 1 mmol of Bi(NO3)·5H2O. An orange-colored solution was obtained after being vigorously stirred for 30 min. The final solution was then transferred into a 50 mL Teflon-lined autoclave and maintained at 120 °C for 10 h. The resultant mixture was separated by centrifugation, and the precipitate was washed with DI water and ethanol several times to remove undesirable ions. The obtained product was dried at 60 °C for 12 h and denoted as BiVO4. Annealing Treatment. The annealing procedures of BiVO4 were carried out by a simple treatment in a tube 16258


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Figure 2. High-resolution XPS spectra of (a) Bi 4f and (b) V 2p in BiVO4 and H-450.

Ar/H2, new diffraction peaks at 27.2, 38.0, and 39.6° appear in the pattern (Figure 1b), besides those from BiVO4. These peaks could be attributed to those from metallic Bi (JCPDS Card, No. 44−1246). It is believed that the reducing atmosphere and high calcination temperature lead to the reduction of BiVO4 to metallic Bi. Along with this change, there must be VOx in the product. However, the absence of the diffraction peaks of VOx indicates that they are probably amorphous. For the sake of clarity, this product obtained in Ar/H2, which is composed of BiVO4, Bi, and VOx, is denoted as H-450. If the calcination atmosphere was switched to air, BiO (JCPDS Card, No. 27− 0654), rather than metallic Bi, is observed in the pattern (Figure 1c). Similar to the case of H-450, the formation of BiO indicates the decomposition of BiVO4 that definitely produces some sort of VOx, although it is likely amorphous. The product composed of BiVO4, BiO, and VOx, is labeled as A-450. If BiVO4 was calcinated in vacuum, the diffraction peaks belonging to Bi2VO5.5 (JCPDS Card, No. 41−0575) are detected (Figure 1d). So, the product composed of BiVO4, Bi2VO5.5, and VOx, is denoted as V-450. These results confirm the influences of the calcination atmosphere to the products, thereby greatly altering the photocatalytic activity in OER. Raman spectra were used to clarify the potential species of VOx. As shown in Figure 1e, the Raman peaks at 208, 329, 365, 710, and 826 cm−1 are in good agreement with those reported for BiVO4.2,34,35 The Raman band at 208 cm−1 comes from the external rotation mode. The peaks at 329 and 365 cm−1 originate from the symmetric bending mode and the asymmetric bending mode of the VO4 tetrahedron. The peaks at 710 and 826 cm−1 can be assigned to the stretching modes of V−O bonds. After high-temperature calcination, the main peaks of BiVO4 are kept for all three samples (H-450, A450, and V-450). It indicates the dominance of BiVO4 in the samples. Meanwhile, the close check around 150 cm−1 discloses a weak but clear sign for V2O5 in all three samples, although the content of V2O5 might vary from one to another (Figure 1f). The high-resolution XPS spectra of Bi and V were obtained to further prove the existence of metallic Bi and V2O5 in the H450 sample. Figure 2a shows the Bi 4f spectra of BiVO4 and H450. There are two new peaks at 156.7 and 162.3 eV in the Bi 4f spectrum of H-450, as compared with that of BiVO4. These peaks are consistent with those reported for Bi 4f5/2 and Bi 4f7/2 of metallic Bi.31 The other doublet at 159.2 and 164.4 eV in the spectrum agrees well with the Bi 4f5/2 and Bi 4f7/2 of BiVO4.15 On the basis of these peaks, the molar ratio of Bi(0) and Bi(III) is estimated as ∼2.6%, suggesting only a small quantity of

resolution TEM (HRTEM) image were obtained by a JEM 2100F analytical transmission electron microscope equipped with an energy-dispersive spectrometer (EDS) at 200 kV. The UV−vis DRS was recorded on a Shimadzu UV-2450 spectrophotometer in the range of 220−850 nm at room temperature, using BaSO4 as the reference. The resistivity was measured using the RTS-8 four-point probes instrument by preparing samples as tablets with a thickness of 0.3 mm and a diameter of 12.90 mm. The test current was controlled at 0.1293 μA. Photocatalytic Activity Measurements. Photocatalytic O2 evolution tests were carried out in a solution of AgNO3 (100 mM, 15 mL), which was used as the sacrificial reagent for electrons. Typically, 40 mg of the as-prepared sample as a photocatalyst was added to the AgNO3 solution in a 50 mL bottle with rubber stopper. The reaction system was vacuumed and flushed with argon by a Schlenk line to remove the residual gas. Then the solution was stirred for 3 h in the dark to reach absorption−desorption equilibrium. The reactor was illuminated with a xenon lamp (Perfect Light Solaredge 700) equipped with a UV cutoff filter (λ > 400 nm). The irradiance of the lamp used for photocatalytic activity measurement of the sample is 200 W. The amount of O2 was determined, using Ar as the carrier gas, by a gas chromatograph (FULI9790II, molecular sieve 5 Å column) equipped with a thermal conductivity detector (TCD). Photoelectrochemical Measurements. Photocurrent measurements were performed on a CHI-760E electrochemical station using a standard three-electrode system. The Pt plate was used as the counter electrode and Ag/AgCl as the reference electrode. A mixed solution of naphthol and ethanol containing 40 mg of the sample was dispersed on ITO glass, which was used as the working electrode. The electrolyte was a mixture of 0.25 M Na2SO4 and 0.25 M Na2SO3. A 200 W Xe lamp equipped with a cutoff filter at 400 nm was used as the light source. A shutter was used to record transient photocurrent decay at 20 s intervals, and the photoelectric responses of the photocatalysts when the light was on and off were measured at +0.8 V vs Ag/AgCl electrode.

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RESULTS AND DISCUSSION The products were examined by XRD patterns to identify their crystal structure. As shown in Figure 1a, the product obtained by the solvothermal reaction could be indexed as monoclinicphase BiVO4 (JCPDS Card No. 14−0688). No impurities are observed in this XRD pattern. After the calcination at 450 °C in 16259


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Figure 3. (a) TEM image and (b) HRTEM image of H-450. TEM images of (c) A-450 and (d) V-450.

Figure 4. (a) Diffuse reflection spectra and (b) real-color photographs of BiVO4, H-450, A-450, and V-450.

H2, the aggregated nanoparticles fuse together, producing solid nanoparticles with a similar size for H-450 (Figure 3a). The morphology change of H-450 could be attributed to the low melting point of Bi (271.3 °C) in H-450, which makes Bi an effective binder to bridge BiVO4 and V2O5. HRTEM image (Figure 3b) of H-450 shows clear lattice fringes, corresponding to (012) of Bi, (121) of BiVO4, and (001) of V2O5. As shown in Figure 3b, BiVO4 is the main component, and Bi and V2O5 are uniformly distributed throughout the particles. The small amount of crystalline V2O5 is the transformation of amorphous V2O5 under high temperature. In addition, these parts without clear lattice fringes are the amorphous V2O5, which is uniformly distributed throughout the particles. This result confirms that Bi and V2O5 are well mixed with BiVO4. This structure benefits the charge transfer from the bulk to the surface, thereby improving the photocatalytic activity of H-450. Different from H-450, A-450 and V-450 basically inherit the morphology from BiVO 4 (Figure 3c,d), although they are different in components.

metallic Bi on the surface. Figure 2b shows the V 2p spectra of H-450 and BiVO4. There are two doublets in the highresolution spectrum of V 2p in H-450. The doublet at 524.0 and 516.7 eV is in good accordance with the reported data for V 2p1/2 and V 2p3/2 in BiVO4.15,18 The other doublet at 524.7 and 517.1 eV, with energies that are slightly higher than those in BiVO4, is consistent with those in V2O5.15,18 This result strongly supports the presence of V2O5 in H-450, although it was obtained by annealing in Ar/H2. On the basis of the evidence above, the reactions during the annealing treatments can be concluded as follows: H 2: 2BiVO4 + 3H 2 → 2Bi + V2O5 + 3H 2O

(1-1)

Air: 4BiVO4 → 4BiO + 2V2O5 + O2

(1-2)

Vac: 4BiVO4 → 2Bi 2VO5.5 + V2O5

(1-3)

Figure 3 shows the TEM results of H-450, A-450, and V-450. BiVO4 consists of highly aggregated nanoparticles with their overall size about 70−130 nm (Figure S1). This size is smaller than many of the reported ones.36−39 After being treated in Ar/ 16260


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Figure 5. (a) Photocatalytic performances of BiVO4, H-450, A-450, and V-450 in OER. (b) Electrical resistivities and (c) photocurrent responses of BiVO4, H-450, A-450, and V-450. (d) Recycling performance of H-450.

Figure 6. Proposed mechanism for photoinduced processes on H-450.

charge separation and prolong the lifetime, thus enhancing the photocatalytic activity. Figure 5a shows photocatalytic activities of BiVO4, H-450, V450, and A-450 in OER under visible light. Although all of the samples generate oxygen over time, they are quite different in terms of photocatalytic activity. As compared to BiVO4, V-450, and A-450, H-450 exhibits the highest activity, although the rate of oxygen generation gradually slows down after 20 min. This result might be attributed to the consumption of the selfsacrificial agent (AgNO3) and the deposition of silver on the surface. This result is supported by the XRD pattern (Figure S2b) and elemental maps (Figure S3) of H-450 after OER. Figure S4 shows the OER test of H-450 with Na2S2O8 as the

Optical properties of BiVO4, H-450, A-450, and V-450 are investigated by diffuse reflection spectra, which is important to their photocatalytic performances. As shown in Figure 4a, BiVO4 gives an absorption edge at 500 nm without any tails beyond this wavelength, consistent with the reported bandgap.7,8 The similar case happens to A-450, although the absorption edge slightly moves to the red (∼535 nm). V-450 and H-450 exhibit an apparent absorption over the range of 500−730 nm, which makes them unique colors (Figure 4b). This absorption of visible light likely originates from Bi in H450 or Bi2VO5.5 in V-450. In spite of different origins, the energy levels reflected by this absorption could promote the 16261


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Figure 7. TEM images of (a) H-350, (b) H-400, (c) H-450, and (d) H-500. XRD patterns of BiVO4, H-350, H-400, H-450, and H-500 in a range of (e) 10°−70° and (f) 25°−32°.

follows the order of V-450, BiVO4, and A-450, which is in good agreement with their photocatalytic activities. This result is also supported by PL. As shown in Figure S5, the PL intensities of these samples are in the following order: H-450 < V-450 < A450 < BiVO4, which is consistent with the trend from photocatalytic performance. The cycling performance of used H-450 was also examined as shown in Figure 5d. It is found that the photocatalyst shows little degradation after five cycles, suggesting its good stability. Figure 6 shows the schematic illustration of photogenerated charges transfer on H-450. The conduction band (CB) and valence band (VB) potentials of BiVO4 and V2O5 can be calculated by related equations.15,41 For an amorphous semiconductor, there are two tail states at the top of valence band and at the bottom of conduction band due to the localized states compared to crystalline semiconductor.42 So, the band structure of amorphous V2O5 is illustrated as the thickened localized states of CB and VB as shown in Figure 6. Both V2O5 and Bi have positive effects for promoting the charge separation and prolonging the lifetime. First, the photogenerated electrons on BiVO4 could transfer to the CB of V2O5, which increases the separation efficiency of photoexcited electron−hole pairs.15 Second and most importantly, the interfacial transfer of electrons from CB of BiVO4 and V2O5 to metallic Bi enhances the separation of electron−hole pairs and increases the lifetime of charge carriers in BiVO4 and V2O5, enhancing the photocatalytic activity of OER. Hence, the special band-gap structure and superior conductivity of Bi determine the high

sacrificial reagent. In comparison with the reaction in AgNO3 solution, the oxygen-evolution rate of H-450 remains unchanged with reaction time, illustrating the inhibition effect of the consumption of the self-sacrificial agent (AgNO3) for the photocatalytic performance of H-450. The similar phenomenon has been reported in previous reports.2,9,34 In spite of this, H450 could be still regarded as the best photocatalyst. At 20 min, the oxygen-generation rate of H-450 for OER is 2413 μmol·g−1· h−1, ∼3.6 times greater than that of V-450 (662 μmol·g−1·h−1), ∼6.4 times greater than that of BiVO4 (375 μmol·g−1·h−1), or ∼29.4 times greater than that of A-450 (82 μmol·g−1·h−1). To understand the excellent performance, electrical resistance and photocurrent responses were measured for all of the samples. As shown in Figure 5b, H-450 shows the lowest electrical resistance, due to metallic Bi in the composite. This result indicates fast charge transfer from the bulk to the surface, which could reduce the recombination of photogenerated charges and then promote the catalytic reaction on the surface. V-450 and A-450 are worse than H-450, but better than BiVO4, due to abundant crystal boundaries.33,40 Photocurrent responses of photocatalysts under irradiation is a powerful tool to identify their charge-separation efficiencies. Here, photocurrent responses of BiVO4, V-450, A-450, and H-450 were measured at 0.8 V by depositing them on ITO glasses. As displayed in Figure 5c, H-450 shows the largest photocurrent response under visible light, which could be ascribed to its small resistance, its enhanced adsorption tail between 500 and 700 nm, as well as its abundant crystal boundaries. The response 16262


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Figure 8. (a) Photocurrent response and (b) photocatalytic performance of BiVO4, H-350, H-400, H-450, and H-500.

pairs due to its bandgap structure. Hence, the Bi/BiVO4/V2O5 composite is an outstanding photocatalyst for an oxygen evolution reaction. Our findings may open up a new avenue for the development of an efficient composite photocatalyst.

separation efficiency, intensity, and transfer rate of photoinduced charge carriers, and these elements facilitate the superior photocatalytic performance of Bi/BiVO 4 /V 2 O 5 composite. The H-t samples were produced to illustrate the influence of the annealing temperature on the morphology and photocatalytic properties during the formation of the Bi/BiVO4/V2O5 composite. As shown in Figure 7a−d, the spherical morphology becomes gradually irregular with the increasing of the annealing temperature in Ar−H2, which is attributed to higher temperatures making Bi be produced more on the surface of BiVO4. The increase of the amount of Bi with the rise of annealing temperature is supported by XRD (Figure 7e,f). Bi is melted at high temperature and plays an important role in composite connection. The more Bi is produced, the more obvious the change of the morphology. Figure 8a,b show the photocurrent response and photocatalytic oxygen evolution of the samples annealed at different temperatures, respectively. H-t samples show a better photocurrent response and photocatalytic activity than pristine BiVO4. Among these samples, H-450 had the highest photocatalytic oxygen evolution. Under the reducing atmosphere (Ar−H2), high temperature is beneficial to the production of Bi, which promotes the transfer and separation of photoinduced charge carriers. However, the consumption of the BiVO4 catalyst with the production of Bi is adverse to the photocatalysis of OER. These parameters lead to the best photocatalytic oxidation activity of H-450. All results indicate that the Ar−H2 atmosphere and 450 °C of annealing temperature are the two necessary elements of the formation of Bi/BiVO4/V2O5 composite photocatalyst with excellent photocatalytic oxidation performance.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpcc.7b03119. TEM image of BiVO4, and XRD and elemental maps of samples before and after OER; photocatalytic performance of H-450 sample with Na2S2O8 as sacrificial reagent and PL spectra of samples (PDF)

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AUTHOR INFORMATION

Corresponding Author

*Fax: +86-531-88364489; Tel.: +86-88364489; E-mail: [email protected]. ORCID

Xia Guo: 0000-0003-1072-5710 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This study was financially supported by the Natural Science Foundation of China (21071055). REFERENCES

(1) Walter, M. G.; Warren, E. L.; McKone, J. R.; Boettcher, S. W.; Mi, Q. X.; Santori, E. A.; Lewis, N. S. Solar Water Splitting Cells. Chem. Rev. 2010, 110, 6446−6473. (2) Thalluri, S. M.; Martinez Suarez, C. M.; Hussain, M.; Hernandez, S.; Virga, A.; Saracco, G.; Russo, N. Evaluation of The Parameters Affecting The Visible-Light-Induced Photocatalytic Activity of Monoclinic BiVO4 for Water Oxidation. Ind. Eng. Chem. Res. 2013, 52, 17414−17418. (3) Maeda, K.; Domen, K. Photocatalytic Water Splitting: Recent Progress and Future Challenges. J. Phys. Chem. Lett. 2010, 1, 2655− 2661. (4) Wang, D.; Jiang, H.; Zong, X.; Xu, Q.; Ma, Y.; Li, G. L.; Li, C. Crystal Facet Dependence of Water Oxidation on BiVO4 Sheets under Visible Light Irradiation. Chem. - Eur. J. 2011, 17, 1275−1282. (5) Wang, D.; Li, R.; Zhu, J.; Shi, J. Y.; Han, J. F.; Zong, X.; Li, C. Photocatalytic Water Oxidation on BiVO4 with The Electrocatalyst as An Oxidation Cocatalyst: Essential Relations between Electrocatalyst and Photocatalyst. J. Phys. Chem. C 2012, 116, 5082−5089.

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CONCLUSION In summary, a Bi/BiVO4/V2O5 composite was successfully prepared by a facile annealing of BiVO4 in Ar/H2. Furthermore, the BiO/BiVO4/V2O5 and Bi2VO5.5/BiVO4/V2O5 composite were synthesized by annealing BiVO4 in air and vacuum, respectively. The optical and photoelectrochemical properties as well as the photocatalytic performance of different composites were explored, which demonstrates that the Bi/ BiVO4/V2O5 composite has outstanding photocatalytic properties. Our results indicate that Bi plays a more crucial role in the enhancement of the photocatalytic performance of BiVO4. Bi deposition can enhance the intensity and the transfer rate of the photoinduced charge carriers. V2O5 component can improve the separation efficiency of the photoinduced electron−hole 16263


Article


Light-Driven Photofunctions for Arsenic Removal. Appl. Catal., B 2016, 184, 347−354. (24) Aquino-Meneses, L.; Lozada-Morales, R.; Lopez-Calzada, G.; Jiménez-Sandoval, S.; Zayas, M. E.; Zelaya-Angel, O.; Becerril, M.; Carmona-Rodriguez, J.; Sanchez-Mora, E.; Serrano, L. E.; et al. Composition Dependence of The Crystalline-to-Amorphous Phase Transformation of Vanadate Compounds in The CdO-V2O5 Binary System. J. Non-Cryst. Solids 2015, 408, 26−31. (25) Cao, S. W.; Yin, Z.; Barber, J.; Boey, F. Y. C.; Loo, S. C. J.; Xue, C. Preparation of Au-BiVO4 Heterogeneous Nanostructures as Highly Efficient Visible-Light Photocatalysts. ACS Appl. Mater. Interfaces 2012, 4, 418−423. (26) Qiao, R.; Mao, M.; Hu, E.; Zhong, Y. J.; Ning, J. Q.; Hu, Y. Facile Formation of Mesoporous BiVO4/Ag/AgCl Heterostructured Microspheres with Enhanced Visible-Light Photoactivity. Inorg. Chem. 2015, 54, 9033−9039. (27) Van, C. N.; Chang, W. S.; Chen, J. W.; Tsai, K. A.; Tzeng, W. Y.; Lin, Y. C.; Kuo, H. H.; Liu, H. J.; Chang, K. D.; Chou, W. C.; et al. Heteroepitaxial Approach to Explore Charge Dynamics Across Au/ BiVO4 Interface for Photoactivity Enhancement. Nano Energy 2015, 15, 625−633. (28) Booshehri, A. Y.; Chun-Kiat Goh, S.; Hong, J.; Jiang, R.; Xu, R. Effect of Depositing Silver Nanoparticles on BiVO4 in Enhancing Visible Light Photocatalytic Inactivation of Bacteria in Water. J. Mater. Chem. A 2014, 2, 6209−6217. (29) Zhou, Z. J.; Long, M. C.; Cai, W. M.; Cai, J. Synthesis and Photocatalytic Performance of The Efficient Visible Light Photocatalyst Ag-AgCl/BiVO4. J. Mol. Catal. A: Chem. 2012, 353−354, 22− 28. (30) Hu, J. J.; Xu, G. Q.; Wang, J. W.; Lv, J.; Zhang, X.; Zheng, Z. X.; Xie, T.; Wu, Y. C. Photocatalytic Properties of Bi/BiOCl Heterojunctions Synthesized Using an in situ Reduction Method. New J. Chem. 2014, 38, 4913−4921. (31) Chen, D. L.; Zhang, M.; Lu, Q. J.; Chen, J. F.; Liu, B. T.; Wang, Z. F. Facile Synthesis of Bi/BiOCl Composite with Selective Photocatalytic Properties. J. Alloys Compd. 2015, 646, 647−654. (32) Yu, Y.; Cao, C. Y.; Liu, H.; Li, P.; Wei, F. F.; Jiang, Y.; Song, W. G. A Bi/BiOCl Heterojunction Photocatalyst with Enhanced ElectronHole Separation and Excellent Visible Light Photodegrading Activity. J. Mater. Chem. A 2014, 2, 1677−1681. (33) Feng, C. C.; Wang, D. H.; Jin, B. J.; Jiao, Z. B. The Enhanced Photocatalytic Properties of BiOCl/BiVO4 p-n Heterojunctions via Plasmon Resonance of Metal Bi. RSC Adv. 2015, 5, 75947−75952. (34) Xue, Y.; Wang, X. T. The Effects of Ag Doping on Crystalline Structure and Photocatalytic Properties of BiVO4. Int. J. Hydrogen Energy 2015, 40, 5878−5888. (35) Singh, A. P.; Kodan, N.; Dey, A.; Krishnamurthy, S.; Mehta, B. R. Improvement in The Structural, Optical, Electronic and Photoelectrochemical Properties of Hydrogen Treated Bismuth Vanadate Thin Film. Int. J. Hydrogen Energy 2015, 40, 4311−4319. (36) Zeng, J.; Zhong, J. B.; Li, J.; Xiang, Z.; Liu, X. L.; Chen, J. F. Improvement of Photocatalytic Activity under Solar Light of BiVO4 Microcrystals Synthesized by Surfactant-Assisted Hydrothermal Method. Mater. Sci. Semicond. Process. 2014, 27, 41−46. (37) Sarkar, S.; Chattopadhyay, K. K. Visible Light Photocatalysis and Electron Emission from Porous Hollow Spherical BiVO4 Nanostructures Synthesized by a Novel Route. Phys. E 2014, 58, 52−58. (38) García-Pérez, U. M.; Martínez-de la Cruz, A.; SepúlvedaGuzmán, S.; Peral, J. Low-Temperature Synthesis of BiVO4 Powders by Pluronic-Assisted Hydrothermal Method: Effect of The Surfactant and Temperature on The Morphology and Structural Control. Ceram. Int. 2014, 40, 4631−4638. (39) Karunakaran, C.; Kalaivani, S.; Vinayagamoorthy, P. Optical, Electrical and Visible Light-Photocatalytic Properties of Hydrothermally Synthesized Amorphous BiVO4 Nanoparticles. Mater. Lett. 2014, 122, 21−24. (40) Lv, P. W.; Zheng, M.; Wang, X.; Huang, F. Subsolidus Phase Relationships and Photocatalytic Properties in The Ternary System TiO2-Bi2O3-V2O5. J. Alloys Compd. 2014, 583, 285−290.

(6) Kudo, A.; Miseki, Y. Heterogeneous Photocatalyst Materials for Water Splitting. Chem. Soc. Rev. 2009, 38, 253−278. (7) Thalluri, S. M.; Martinez Suarez, C. M.; Hernández, S.; Bensaid, S.; Saracco, G.; Russo, N. Elucidation of Important Parameters of BiVO4 Responsible for Photo-Catalytic O2 Evolution and Insights about The Rate of The Catalytic Process. Chem. Eng. J. 2014, 245, 124−132. (8) Huang, Z. F.; Pan, L.; Zou, J. J.; Zhang, X. W.; Wang, L. Nanostructured Bismuth Vanadate-Based Materials for Solar-EnergyDriven Water Oxidation: A Review on Recent Progress. Nanoscale 2014, 6, 14044−04063. (9) Thalluri, S. M.; Hernández, S.; Bensaid, S.; Saracco, G.; Russo, N. Green-Synthesized W-and Mo-doped BiVO4 Oriented along The {040} Facet with Enhanced Activity for The Sun-Driven Water Oxidation. Appl. Catal., B 2016, 180, 630−636. (10) Walsh, A.; Yan, Y.; Huda, M. N.; Al-Jassim, M. M.; Wei, S. H. Band Edge Electronic Structure of BiVO4: Elucidating The Role of The Bi s and V d Orbitals. Chem. Mater. 2009, 21, 547−551. (11) Jiang, H. Q.; Nagai, M.; Kobayashi, K. Enhanced Photocatalytic Activity for Degradation of Methylene Blue over V2O5/BiVO4 Composite. J. Alloys Compd. 2009, 479, 821−827. (12) Balachandran, S.; Prakash, N.; Thirumalai, K.; Muruganandham, M.; Sillanpäa, M.; Swaminathan, M. Facile Construction of Heterostructured BiVO4-ZnO and Its Dual Application of Greater Solar Photocatalytic Activity and Self-Cleaning Property. Ind. Eng. Chem. Res. 2014, 53, 8346−8356. (13) Grigioni, I.; Stamplecoskie, K. G.; Selli, E.; Kamat, P. Dynamics of Photogenerated Charge Carriers in WO3/BiVO4 Heterojunction Photoanodes. J. Phys. Chem. C 2015, 119, 20792−20800. (14) He, Z. Q.; Shi, Y. Q.; Gao, C.; Wen, L.; Chen, J. M.; Song, S. BiOCl/BiVO4 p−n Heterojunction with Enhanced Photocatalytic Activity under Visible-Light Irradiation. J. Phys. Chem. C 2014, 118, 389−398. (15) Su, J.; Zou, X. X.; Li, G. D.; Wei, X.; Yan, C.; Wang, Y. N.; Zhao, J.; Zhou, L. J.; Chen, J. S. Macroporous V2O5-BiVO4 Composites: Effect of Heterojunction on the Behavior of Photogenerated Charges. J. Phys. Chem. C 2011, 115, 8064−8071. (16) Wang, W. Z.; Huang, X. W.; Wu, S.; Zhou, Y. X.; Wang, L. J.; Shi, H. L.; Liang, Y. J.; Zou, B. Preparation of p-n Junction Cu2O/ BiVO4 Heterogeneous Nanostructures with Enhanced Visible-Light Photocatalytic Activity. Appl. Catal., B 2013, 134−135, 293−301. (17) Zhao, W.; Liu, Y.; Wei, Z.; Yang, S. G.; He, H.; Sun, C. Fabrication of a Novel p-n Heterojunction Photocatalyst n-BiVO4@pMoS2 with Core-Shell Structure and Its Excellent Visible-Light Photocatalytic Reduction and Oxidation Activities. Appl. Catal., B 2016, 185, 242−252. (18) Sun, J. J.; Li, X. Y.; Zhao, Q. D.; Ke, J.; Zhang, D. K. Novel V2O5/BiVO4/TiO2 Nanocomposites with High Visible-Light-Induced Photocatalytic Activity for the Degradation of Toluene. J. Phys. Chem. C 2014, 118, 10113−10121. (19) Yin, H. H.; Yu, K.; Song, C. Q.; Huang, R.; Zhu, Z. Q. Synthesis of Au-Decorated V2O5@ZnO Heteronanostructures and Enhanced Plasmonic Photocatalytic Activity. ACS Appl. Mater. Interfaces 2014, 6, 14851−14860. (20) Wang, J.; Chen, F.; Zhou, X. P. Photocatalytic Degradation of Acetone over A V2O5/LaF3 Catalyst under Visible Light. J. Phys. Chem. C 2008, 112, 9723−9729. (21) Putluru, S. S. R.; Schill, L.; Godiksen, A.; Poreddy, R.; Mossin, S.; Jensen, A. D.; Fehrmann, R. Promoted V2O5/TiO2 Catalysts for Selective Catalytic Reduction of NO with NH3 at Low Temperatures. Appl. Catal., B 2016, 183, 282−290. (22) Beliatis, M. J.; Helgesen, M.; Garcia-Valverde, R.; Corazza, M.; Roth, B.; Carle, J. E.; Jorgensen, M.; Krebs, F. C.; Gevorgyan, S. A. Slot-Die-Coated V2O5 as Hole Transport Layer for Flexible Organic Solar Cells and Optoelectronic Devices. Adv. Eng. Mater. 2016, 18, 1494−1503. (23) Xie, L. Y.; Liu, P.; Zheng, Z.; Weng, S.; Huang, J. Morphology Engineering of V2O5/TiO2 Nanocomposites with Enhanced Visible 16264


Article

The Journal of Physical Chemistry C (41) Raja, S.; Subramani, G.; Bheeman, D.; Rajamani, R.; Bellan, C. S. Structural and Optical Properties of Vacuum Evaporated V2O5 Thin Film. Optik 2016, 127, 461−464. (42) Liu, E. K.; Zhu, B. S.; Luo, J. S. The Physics of Semiconductors; Publishing House of Electronics Industry: Beijing, 2011.

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