Bismuth vanadate / titanium dioxide / cobalt phosphate photoanode and preparation method thereof

Abstract

The present invention discloses a bismuth vanadate / titanium dioxide / cobalt phosphate photoanode and a preparation method thereof. The method firstly spin-coats a mixed solution of bismuth nitrate pentahydrate and vanadyl acetylacetonate on an FTO substrate, and anneals to obtain a BiVO4 photoanode; then, a TiO2 film is deposited on the surface of the BiVO4 photoanode by electrophoretic deposition to obtain a BiVO4 / TiO2 photoanode; finally, a Co‑Pi co-catalyst layer is deposited on the surface of the BiVO4 / TiO2 photoanode by electrophoretic deposition to obtain a BiVO4 / TiO2 / Co‑Pi photoanode. The BiVO4 / TiO2 / Co‑Pi photoanode of the present invention has excellent stability and exhibits a good service life. It also has a high carrier transport capacity and good photoelectrochemical performance, and can achieve a high photocurrent density at a low potential. At 1.23 vs. RHE, the highest photocurrent density generated is 4.2 mA / cm 2 , which is about 3 times that of BiVO4 photoanode.

Description

Technical Field

[0001] The invention belongs to the field of photoelectric catalytic material preparation, and relates to a bismuth vanadate / titanium dioxide / cobalt phosphate (BiVO4 / TiO2 / Co-Pi) photoanode and a preparation method thereof. Background Art

[0002] Photoelectrochemical (PEC) water splitting technology is a direct way to convert solar energy into clean hydrogen. Bismuth vanadate (BiVO4) is one of the most promising photoanodes for PEC water splitting, with advantages such as a smaller band gap (2.4eV), a deeper valence band (VB) position, and a simpler preparation method. Theoretically, under AM1.5G simulated sunlight, the water oxidation photocurrent density of BiVO4 can reach 7.5mA / cm at 1.23Vvs.RHE. 2 However, BiVO4 suffers from serious carrier recombination and photocorrosion under sunlight, which affects its practical application. Therefore, improving the carrier transport capacity and stability of BiVO4 is crucial to improving the efficiency of PEC water splitting.

[0003] Depositing a protective layer has become an important way to inhibit BiVO4 photocorrosion. TiO2, which is usually used as a protective layer, mainly uses an expensive atomic layer deposition (ALD) method (Zhong, Miao, et al. Journal of the American Chemical Society 137.15 (2015): 5053-5060.) or spin coating deposition (Bhat, Swetha SM, et al. ACS Applied Energy Materials 3.6 (2020): 5646-5656.), and the TiO2 protective layer prevents direct contact between the electrolyte and BiVO4, while inhibiting photocorrosion. However, ALD technology is not economically feasible, and the spin coating annealing process is difficult to regulate the quality of the TiO2 film.

[0004] Some highly efficient oxygen evolution promoters (OEC), such as Co3O4, FeCoO X, NiCo2O4, MnCo2O4 and ZnCo2O4 have a positive effect on accelerating the charge transfer of BiVO4 to achieve efficient water decomposition (Chang, Xiaoxia, et al. Journal of the American Chemical Society 137.26 (2015): 8356-8359.), after OEC is loaded on the BiVO4 surface by electrophoretic deposition process, the modified BiVO4 photoanode has excellent PEC water decomposition activity and good hydrogen production performance. However, there are problems such as carrier recombination or capture by interface defects at the interface between OEC and BiVO4, which limits the water decomposition capacity. Summary of the invention

[0005] The object of the present invention is to provide a BiVO4 / TiO2 / Co-Pi photoanode and a preparation method thereof. The method prepares a BiVO4 photoanode by a metal organic decomposition method, then electrophoretically deposits a TiO2 passivation protective layer on the surface of the BiVO4 photoanode to solve the problem of poor stability of the BiVO4 photoanode in the prior art, thereby obtaining a BiVO4 / TiO2 photoanode, and finally electrophoretically deposits a Co-Pi co-catalyst layer on the surface of the BiVO4 / TiO2 photoanode to solve the problem of poor carrier transport capacity of the BiVO4 photoanode in the prior art, thereby obtaining a high-performance BiVO4 / TiO2 / Co-Pi photoanode.

[0006] The technical solution for achieving the purpose of the present invention is as follows:

[0007] The preparation method of BiVO4 / TiO2 / Co-Pi photoanode, the specific steps are as follows:

[0008] (1) dissolving bismuth nitrate pentahydrate and vanadyl acetylacetonate in a mixed solution of acetic acid and acetylacetone, subjecting the mixture to ultrasonic treatment to completely dissolve the mixture, thereby obtaining a precursor solution, spin-coating the precursor solution on a FTO substrate, and annealing the substrate at 500±10° C. for 10 min in a muffle furnace, repeating the annealing for 8 times, and finally annealing the substrate at 500±10° C. for 2 h to obtain a BiVO4 photoanode;

[0009] (2) adjusting the pH of the titanium trichloride solution to 2.0-2.2 with a Na2CO3 solution, depositing a TiO2 film on the surface of the BiVO4 photoanode by an electrophoretic deposition method, and obtaining a BiVO4 / TiO2 photoanode after washing and drying;

[0010] (3) Cobalt nitrate hexahydrate is added to potassium phosphate (KPi) solution and the pH is adjusted to 6.9-7.1 with Na2CO3 solution to obtain a Co-Pi electrophoretic deposition solution, and a Co-Pi co-catalyst layer is deposited on the surface of the BiVO4 / TiO2 photoanode by electrophoretic deposition. After cleaning and drying, the BiVO4 / TiO2 / Co-Pi photoanode is obtained.

[0011] Preferably, in step (1), the mass ratio of bismuth nitrate pentahydrate to vanadyl acetylacetonate is 0.173:0.095; and the volume ratio of acetic acid to acetylacetone is 1:8.5.

[0012] Preferably, in step (1), the spin coating conditions are: spin coating at a rotation speed of 800 to 1200 r / min for 25 to 35 s.

[0013] Preferably, in step (2), the titanium trichloride solution contains Ti 3+ The concentration is 55-60mM.

[0014] Preferably, in step (2), the conditions for electrophoretic deposition are: using a BiVO4 photoanode as a working electrode, a platinum sheet as a counter electrode, and a calomel electrode as a reference electrode, the three electrodes are immersed in a titanium trichloride solution, the potential is 0 to 0.04 V vs. SCE, and the deposition time is 5 to 15 s.

[0015] Preferably, in step (3), the KPi solution is prepared by dissolving a mixture of potassium dihydrogen phosphate and dipotassium hydrogen phosphate in a molar ratio of 1:1 in water.

[0016] Preferably, in step (3), the molar ratio of cobalt nitrate hexahydrate to KPi is 0.005:1.

[0017] Preferably, in step (3), the conditions for electrophoretic deposition are: using BiVO4 / TiO2 photoanode as the working electrode, platinum sheet as the counter electrode, and silver / silver chloride electrode as the reference electrode, the three electrodes are immersed in the electrophoretic deposition solution of Co-Pi, the potential is -0.4 to -0.2 vs. Ag / AgCl, and the deposition time is 200 to 250 s.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] The BiVO4 / TiO2 / Co-Pi photoanode prepared by the present invention has excellent stability and shows a good service life. It also has a high carrier transport capacity and good photoelectrochemical performance. It can achieve a higher photocurrent density at a lower potential. At 1.23 vs. RHE, the highest photocurrent density generated is 4.2 mA / cm 2 , which is about 3 times that of BiVO4 photoanode. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 XRD diagrams of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi in Comparative Examples 1-3 and Example 1.

[0021] Figure 2 SEM images of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi in Comparative Examples 1-3 and Example 1.

[0022] Figure 3 This is the full XPS spectrum of BiVO4 and BiVO4 / TiO2 / Co-Pi in Comparative Example 1 and Example 1.

[0023] Figure 4 UV-visible absorption spectra of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi in Comparative Examples 1-3 and Example 1.

[0024] Figure 5 Band gap energy diagram of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi in Comparative Examples 1-3 and Example 1.

[0025] Figure 6 The current-voltage curves of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi in Comparative Examples 1-3 and Example 1 are shown.

[0026] Figure 7 Polarization curves of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi in Comparative Examples 1-3 and Example 1. The data were collected under no light conditions.

[0027] Figure 8 ABPE curves of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi in Comparative Examples 1-3 and Example 1.

[0028] Fig. 9 It is the IPCE curve diagram of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi in Comparative Examples 1-3 and Example 1.

[0029] Fig.10EIS impedance spectra of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi in Comparative Examples 1-3 and Example 1.

[0030] Fig.11 Graph showing the charge separation efficiency of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi in Comparative Examples 1-3 and Example 1.

[0031] Fig.12 IT curves of BiVO4 and BiVO4 / TiO2 / Co-Pi in Comparative Example 1 and Example 1.

[0032] Fig.13 The theoretical yields of H2 and O2 of BiVO4 and BiVO4 / TiO2 / Co-Pi in Comparative Example 1 and Example 1. DETAILED DESCRIPTION

[0033] The present invention is further described in detail below in conjunction with embodiments and drawings.

[0034] Comparative Example 1

[0035] Dissolve 0.173g of bismuth nitrate pentahydrate and 0.095g of vanadium acetylacetonate in a mixed solution of 0.55ml of acetic acid and 4.45ml of acetylacetone to obtain a dark green solution, and ultrasonically treat the solution until it is completely dissolved. Spin the resulting precursor solution on a clean FTO surface at a speed of 1000rpm, with a spin coating time of 30s and an acceleration of 100rpm / s. Place the spin-coated FTO in a muffle furnace, anneal at 500℃ for 10min, then take it out and cool it naturally to room temperature in the air. Repeat the above steps 8 times, and anneal at 500℃ for 2h for the last time to obtain a BiVO4 photoanode.

[0036] Comparative Example 2

[0037] Dissolve 0.173g of bismuth nitrate pentahydrate and 0.095g of vanadium acetylacetonate in a mixed solution of 0.55ml of acetic acid and 4.45ml of acetylacetone to obtain a dark green solution, and ultrasonically treat the solution until it is completely dissolved. Spin the resulting precursor solution on a clean FTO surface at a speed of 1000rpm, with a spin coating time of 30s and an acceleration of 100rpm / s. Place the spin-coated FTO in a muffle furnace, anneal at 500℃ for 10min, then take it out and cool it naturally to room temperature in the air. Repeat the above steps 8 times, and anneal at 500℃ for the last time for 2h to obtain a BiVO4 photoanode. Add 2ml of titanium trichloride solution to 40ml of deionized water to dilute Ti 3+The final concentration was 57mM. After vigorous stirring, the pH was adjusted to 2.1 with 1M Na2CO3 solution. At this time, the solution slowly changed from light pink to dark purple, and the electrophoretic deposition solution of TiO2 was obtained. The BiVO4 photoanode was used as the working electrode, the platinum sheet was used as the counter electrode, and the calomel electrode was used as the reference electrode. The three electrodes were immersed in the TiO2 electrophoretic deposition solution. The deposition was carried out for 10s at a potential of 0.02V vs. SCE. After the deposition, the electrodes were rinsed with deionized water and dried naturally in the air to obtain the BiVO4 / TiO2 photoanode.

[0038] Comparative Example 3

[0039] 0.173g of bismuth nitrate pentahydrate and 0.095g of vanadium acetylacetonate were dissolved in a mixed solution of 0.55ml of acetic acid and 4.45ml of acetylacetone to obtain a dark green solution, and the solution was ultrasonically treated until completely dissolved. The obtained precursor solution was spin-coated on a clean FTO surface at a speed of 1000rpm, the spin-coating time was 30s, and the acceleration was 100rpm / s. The spin-coated FTO was placed in a muffle furnace, annealed at 500℃ for 10min, then taken out and naturally cooled to room temperature in the air. Repeat the above steps 8 times, and annealed at 500℃ for 2h in the last time to obtain a BiVO4 photoanode. 0.3402g of potassium dihydrogen phosphate and 0.4354g of potassium dihydrogen phosphate were dissolved in 100ml of deionized water, and stirred vigorously to dissolve them completely to obtain a KPi solution. Then, 0.0146 g of cobalt nitrate hexahydrate was added to the KPi solution, and after further stirring, the pH was adjusted to 7 with a 1 M Na2CO3 solution to obtain a Co-Pi electrophoretic deposition solution. The three electrodes were immersed in the Co-Pi electrophoretic deposition solution with a BiVO4 photoanode as the working electrode, a platinum sheet as the counter electrode, and a silver / silver chloride electrode as the reference electrode. The deposition was performed for 225 seconds at a potential of -0.3 V vs. Ag / AgCl. After the deposition, the electrodes were rinsed with deionized water and dried naturally in the air to obtain a BiVO4 / Co-Pi photoanode.

[0040] Example 1

[0041] Dissolve 0.173g of bismuth nitrate pentahydrate and 0.095g of vanadium acetylacetonate in a mixed solution of 0.55ml of acetic acid and 4.45ml of acetylacetone to obtain a dark green solution, and ultrasonically treat the solution until it is completely dissolved. Spin the resulting precursor solution on a clean FTO surface at a speed of 1000rpm, with a spin coating time of 30s and an acceleration of 100rpm / s. Place the spin-coated FTO in a muffle furnace, anneal at 500℃ for 10min, then take it out and cool it naturally to room temperature in the air. Repeat the above steps 8 times, and anneal at 500℃ for the last time for 2h to obtain a BiVO4 photoanode. Add 2ml of titanium trichloride solution to 40ml of deionized water to dilute Ti 3+ The final concentration was 57mM. After vigorous stirring, the pH was adjusted to 2.1 with 1M Na2CO3 solution. At this time, the solution slowly changed from light pink to dark purple to obtain the electrophoretic deposition solution of TiO2. With BiVO4 photoanode as the working electrode, platinum sheet as the counter electrode, and calomel electrode as the reference electrode, the three electrodes were immersed in the TiO2 electrophoretic deposition solution. At a potential of 0.02V vs.SCE, the deposition was carried out for 10s. After the deposition was completed, the electrodes were rinsed with deionized water and dried naturally in the air to obtain BiVO4 / TiO2 photoanode. 0.3402g of potassium dihydrogen phosphate and 0.4354g of potassium dihydrogen phosphate were dissolved in 100ml of deionized water and stirred vigorously to dissolve completely to obtain KPi solution. Subsequently, 0.0146g of cobalt nitrate hexahydrate was added to the KPi solution. After further stirring, the pH was adjusted to 7 with 1M Na2CO3 solution to obtain the electrophoretic deposition solution of Co-Pi. Using BiVO4 / TiO2 photoanode as the working electrode, platinum sheet as the counter electrode, and silver / silver chloride electrode as the reference electrode, the three electrodes were immersed in the electrophoretic deposition solution of Co-Pi. Deposition was performed for 225 seconds at a potential of -0.3V vs.Ag / AgCl. After the deposition, the electrodes were rinsed with deionized water and dried naturally in the air to obtain the BiVO4 / TiO2 / Co-Pi photoanode.

[0042] Figure 1 XRD patterns of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi photoanodes in Comparative Examples 1-3 and Example 1. Except for the characteristic peak of FTO, all characteristic diffraction peaks point to monoclinic BiVO4 (JCPDS No.14-0688), indicating the successful preparation of BiVO4 photoanodes; in the XRD patterns of BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi photoanodes, no diffraction peaks of TiO2 and Co-Pi were observed, which may be due to their low contents.

[0043] Figure 2The SEM images of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi photoanodes in Comparative Examples 1-3 and Example 1 (where a is BiVO4, b is BiVO4 / TiO2, c is BiVO4 / Co-Pi, and d is BiVO4 / TiO2 / Co-Pi). The BiVO4 photoanode is polycrystalline, and its main characteristic size is 100 to 200 nanometers. For BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi photoanodes, the introduction of the TiO2 passivation layer and the Co-Pi co-catalyst layer does not significantly change the morphology of the film.

[0044] Figure 3 The full XPS spectra of BiVO4 and BiVO4 / TiO2 / Co-Pi photoanodes in Comparative Example 1 and Example 1. By comparison, the characteristic absorption peaks of Ti and Co elements in BiVO4 / TiO2 / Co-Pi can be clearly observed, indicating that the TiO2 passivation layer and the Co-Pi co-catalyst layer are perfectly introduced into BiVO4, further confirming the successful synthesis of the BiVO4 / TiO2 / Co-Pi photoanodes.

[0045] Figure 4 The UV-visible absorption spectra of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi photoanodes in Comparative Examples 1-3 and Example 1 are shown. The BiVO4 photoanodote exhibits a strong absorption edge near 500nm; compared with BiVO4, the absorption edge of BiVO4 / TiO2 does not change significantly, while BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi exhibit relatively high light absorption intensities, indicating that the light absorption of the BiVO4 / TiO2 / Co-Pi photoanodote has been enhanced.

[0046] Figure 5 The band gap energy diagram of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi photoanodes in Comparative Examples 1-3 and Example 1. The band gap energies of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi are 2.53eV, 2.51eV, 2.52eV and 2.50eV, respectively, which further illustrates that the light absorption capacity of BiVO4 / TiO2 / Co-Pi photoanodes is enhanced.

[0047] Figure 6The current-voltage curves of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi photoanodes in Comparative Examples 1-3 and Example 1. At 1.23 V vs. RHE, the photocurrent density of BiVO4 is 1.4 mA / cm 2 , BiVO4 / TiO2 and BiVO4 / Co-Pi respectively increase the photocurrent density to 2.0mA / cm 2 and 3.5mA / cm 2 , which are 1.4 and 2.5 times of BiVO4 respectively; the photocurrent density of BiVO4 / TiO2 / Co-Pi can be increased to 4.2mA / cm 2 , which is 3 times that of BiVO4, indicating that the photoelectric performance of BiVO4 / TiO2 / Co-Pi photoelectrode has been greatly improved.

[0048] Figure 7 Polarization curves of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi photoanodes in Comparative Examples 1-3 and Example 1. The data were collected without light. BiVO4 / TiO2 / Co-Pi has a lower overpotential and a higher current density than BiVO4 / Co-Pi, BiVO4 / TiO2 and BiVO4, especially its starting potential is about 1.3Vvs.RHE, indicating that the role of Co-Pi is to accelerate the surface reaction as an OEC, and the response ability of BiVO4 / TiO2 / Co-Pi photoanodes to low potentials is improved.

[0049] Figure 8 The ABPE curves of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi photoanodes in comparative examples 1-3 and embodiment 1 are shown. Among them, BiVO4 / TiO2 / Co-Pi reaches a maximum value of 1.27% at 0.66V vs.RHE. In comparison, the maximum ABPE values ​​of BiVO4 / Co-Pi and BiVO4 / TiO2 are 0.92% at 0.72V vs.RHE and 0.25% at 1.01V vs.RHE, respectively. BiVO4 can only reach 0.15% at 1.04V vs.RHE, which shows that the BiVO4 / TiO2 / Co-Pi photoanodes can obtain larger photocurrents at lower bias voltages, and the starting potential also has a significant negative shift.

[0050] Fig. 9The IPCE curves of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi photoanodes in Comparative Examples 1-3 and Example 1 are shown. In the entire wavelength range of 350-550nm, due to the loading of TiO2 and Co-Pi, the IPCE (incident photon-to-current conversion efficiency) value of the BiVO4 / TiO2 / Co-Pi photoanodes is greatly improved, reaching a maximum value of 89.7% at 420nm. The IPCE values ​​of BiVO4 / Co-Pi, BiVO4 / TiO2 and BiVO4 are 69.9%, 13.0% and 9.4% respectively, reflecting the improvement of charge collection and processing and transport capabilities in the BiVO4 / TiO2 / Co-Pi photoanodes.

[0051] Fig.10 EIS impedance spectra of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi photoanodes in Comparative Examples 1-3 and Example 1. The arc radius of BiVO4 / TiO2 / Co-Pi is much smaller than that of BiVO4, BiVO4 / TiO2 and BiVO4 / Co-Pi, which further indicates that the TiO2 passivation layer and the Co-Pi co-catalyst layer can synergistically improve the charge transfer efficiency of the photoanode, making the BiVO4 / TiO2 / Co-Pi photoanode have better charge transfer capability.

[0052] Fig.11 The charge injection efficiency diagram of BiVO4, BiVO4 / TiO2, BiVO4 / Co-Pi and BiVO4 / TiO2 / Co-Pi photoanodes in Comparative Examples 1-3 and Example 1 is shown. The charge injection efficiency of BiVO4 is 40.3% at 1.23V vs.RHE, while that of BiVO4 / TiO2 / Co-Pi reaches 79.2% at 1.23V vs.RHE, which is nearly twice that of BiVO4 photoanodes. Meanwhile, the efficiencies of BiVO4 / TiO2 and BiVO4 / Co-Pi are 50.8% and 70.9%, respectively. This indicates that the TiO2 passivation layer and the Co-Pi co-catalyst layer can synergistically suppress carrier recombination at the BiVO4 interface.

[0053] Fig.12 The IT curves of BiVO4 and BiVO4 / TiO2 / Co-Pi photoanodes in Comparative Example 1 and Example 1 are shown. The performance of BiVO4 / TiO2 / Co-Pi has almost no obvious attenuation after 10 hours of illumination, and still maintains 91.5% of the performance, while the performance of BiVO4 has dropped by about half, and only 51.2% of the performance is retained after 10 hours. This shows that the TiO2 passivation layer and the Co-Pi co-catalyst layer can synergistically inhibit the photocorrosion of BiVO4 and enhance stability.

[0054] Fig.13 The theoretical yields of H2 and O2 of BiVO4 and BiVO4 / TiO2 / Co-Pi photoanodes in Comparative Example 1 and Example 1. After 10 h of illumination, the theoretical yields of H2 and O2 of BiVO4 / TiO2 / Co-Pi are 767.64 μmol h -1 cm -2 and 383.82 μmol h -1 cm -2 , compared with 285.56 μmol h of BiVO4 -1 cm -2 and 142.78 μmol h -1 cm -2 It increased by 2.67 times, which shows that the introduction of TiO2 and Co-Pi significantly improved the activity of BiVO4 and the water decomposition ability was greatly improved.

Claims

1. A method for preparing a BiVO4 / TiO2 / Co-Pi photoanode, characterized in that: The specific steps are as follows: (1) dissolving bismuth nitrate pentahydrate and vanadyl acetylacetonate in a mixed solution of acetic acid and acetylacetone, subjecting the mixture to ultrasonic treatment to completely dissolve the mixture, thereby obtaining a precursor solution, spin-coating the precursor solution on a FTO substrate, and annealing the substrate at 500±10° C. for 10 min in a muffle furnace, repeating the annealing for 8 times, and finally annealing the substrate at 500±10° C. for 2 h to obtain a BiVO4 photoanode; (2) adjusting the pH of the titanium trichloride solution to 2.0-2.2 with a Na2CO3 solution, depositing a TiO2 film on the surface of the BiVO4 photoanode by an electrophoretic deposition method, and obtaining a BiVO4 / TiO2 photoanode after washing and drying; (3) Cobalt nitrate hexahydrate is added to the KPi solution and the pH is adjusted to 6.9-7.1 with a Na2CO3 solution to obtain a Co-Pi electrophoretic deposition solution, and a Co-Pi co-catalyst layer is deposited on the surface of the BiVO4 / TiO2 photoanode by electrophoretic deposition. After cleaning and drying, a BiVO4 / TiO2 / Co-Pi photoanode is obtained.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of bismuth nitrate pentahydrate to vanadyl acetylacetonate is 0.173:0.095; and the volume ratio of acetic acid to acetylacetone is 1:8.

5.

3. The preparation method according to claim 1, characterized in that: In step (1), the spin coating conditions are: spin coating at a rotation speed of 800 to 1200 r / min for 25 to 35 s.

4. The preparation method according to claim 1, characterized in that: In step (2), the titanium trichloride solution Ti 3+ The concentration is 55-60mM.

5. The preparation method according to claim 1, characterized in that: In step (2), the conditions for electrophoretic deposition are: using BiVO4 photoanode as the working electrode, platinum sheet as the counter electrode, and calomel electrode as the reference electrode, the three electrodes are immersed in titanium trichloride solution, the potential is 0-0.04V vs.SCE, and the deposition time is 5-15s.

6. The preparation method according to claim 1, characterized in that: In step (3), the KPi solution is prepared by dissolving a mixture of potassium dihydrogen phosphate and dipotassium hydrogen phosphate in a molar ratio of 1:1 in water.

7. The preparation method according to claim 1, characterized in that: In step (3), the molar ratio of cobalt nitrate hexahydrate to KPi is 0.005:

1.

8. The preparation method according to claim 1, characterized in that: In step (3), the conditions for electrophoretic deposition are: using BiVO4 / TiO2 photoanode as the working electrode, platinum sheet as the counter electrode, and silver / silver chloride electrode as the reference electrode, the three electrodes are immersed in the electrophoretic deposition solution of Co-Pi, the potential is -0.4 to -0.2 vs. Ag / AgCl, and the deposition time is 200 to 250 s.

9. The BiVO4 / TiO2 / Co-Pi photoanode prepared according to the preparation method of any one of claims 1 to 8.

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