Efficient and stable material for producing hydrogen by photolysis of water and preparation method thereof

Abstract

The invention discloses an efficient and stable material for producing hydrogen by photosplitting water and a preparation method thereof, a WO3 / BiVO4 heterojunction photoelectrode is prepared by compounding WO3 and BiVO4, and efficient photoelectrochemical performance is realized by utilizing matched energy band positions of the WO3 and the BiVO4 and good visible light capturing capability. In addition, an ultrathin oxide protection layer is plated on the surface of the prepared photoelectrode through an atomic layer deposition method, and stable photoelectrochemical performance is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalytic water hydrogen production materials, and in particular to a highly efficient and stable photocatalytic water hydrogen production material and a preparation method thereof. Background Art

[0002] In recent decades, with the massive consumption of fossil energy and the continuous growth of global energy demand, humans are facing an urgent need to develop new energy sources. As an extremely abundant renewable energy source, solar energy is attracting more and more attention. Semiconductor photoelectrochemical (PEC) technology, with its unique advantage of efficiently converting solar energy into electrical energy or chemical energy (such as hydrogen energy), is considered to be one of the effective ways to solve the energy crisis and environmental pollution.

[0003] In PEC water splitting technology, how to design and prepare low-cost semiconductor photoelectrode materials while achieving high solar energy-to-chemical energy conversion efficiency and long-term stable operating characteristics has always been a research hotspot in the field of photoelectrochemical cells. Single oxide semiconductor electrodes often face many limitations in pursuing the above goals. In contrast, heterojunction structures composed of two or more different semiconductor materials usually exhibit superior performance due to their unique electronic and optical properties. However, in practical applications, how to find and optimize such heterojunction materials is still an important topic of current research.

[0004] BiVO4, as a Bi-based oxide material with a small bandgap, non-toxicity and good chemical stability, has attracted much attention due to its potential application value. However, the low carrier migration efficiency and poor charge transport properties seriously restrict the application of BiVO4 in actual photoelectrochemical cells. At present, research on BiVO4 photoelectrodes mainly focuses on the design and preparation of materials, such as improving their performance through doping, heterojunction preparation, micro-nanostructuring and other means. However, the stability problem of the photoelectrode cannot be ignored. Therefore, there is an urgent need for a technical solution that can effectively improve the stability of BiVO4 photoelectrode materials while maintaining their high photoelectric energy-chemical energy conversion efficiency. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a highly efficient and stable photocatalytic water splitting hydrogen production material and a preparation method thereof.

[0006] The present invention is achieved through the following technical solutions:

[0007] The present invention provides a method for preparing a material for producing hydrogen by photolysis of water, comprising the following steps:

[0008] (1) dissolving a tungsten source and polyvinyl alcohol in hydrogen peroxide to obtain a WO3 seed layer precursor solution; mixing a tungsten source aqueous solution, ethanol, a hydrochloric acid solution, oxalic acid and urea to obtain a WO3 hydrothermal colloid; coating the WO3 seed layer precursor solution on a substrate, and obtaining a substrate covered with a WO3 seed layer after annealing;

[0009] (2) placing the substrate covered with the WO3 seed layer obtained in step (1) in a reactor, and then pouring the WO3 hydrothermal colloid obtained in step (1) into the reactor for hydrothermal reaction, taking out the substrate after the reaction is completed, and obtaining a substrate covered with a WO3 thin film after annealing;

[0010] (3) mixing a bismuth source, a vanadium source, citric acid, nitric acid, polyvinyl alcohol and acetic acid to obtain a BiVO4 precursor solution; coating the BiVO4 precursor solution on the substrate covered with the WO3 thin film obtained in step (2), and obtaining a substrate covered with a WO3 / BiVO4 heterojunction after annealing;

[0011] (4) Depositing an amorphous TiO2 layer on the substrate covered with the WO3 / BiVO4 heterojunction obtained in step (3) by atomic layer deposition to obtain the photocatalytic water splitting hydrogen production material on the substrate.

[0012] The present invention prepares a WO3 / BiVO4 heterojunction photoelectrode (i.e., a photocatalytic water splitting hydrogen production material) by compounding WO3 and BiVO4, and utilizes the matching energy band positions and good visible light capture capabilities of the two to achieve efficient photoelectrochemical performance. In addition, an ultra-thin oxide protective layer is plated on the surface of the prepared photoelectrode by atomic layer deposition. The amorphous TiO2 layer contains abundant oxygen vacancies and can serve as an effective passivation layer to enhance the charge separation of photogenerated carriers, thereby improving the photoelectrochemical performance of the electrode and achieving stable photoelectrochemical performance.

[0013] Furthermore, in step (1), the tungsten source is selected from one or more of tungstic acid, sodium tungstate (Na2WO4) and tungsten hexachloride (WCl6).

[0014] Furthermore, in step (1), the mass ratio of the tungsten source to polyvinyl alcohol is (1-2):(0.3-0.8), and the dosage ratio of the tungsten source to hydrogen peroxide is (1-2) g:(15-20) mL.

[0015] Furthermore, in step (1), the concentration of the hydrogen peroxide solution is 20-40 wt %.

[0016] Furthermore, in step (1), the volume ratio of the tungsten source aqueous solution, ethanol and hydrochloric acid solution is (2-4):(8-10):(3-5).

[0017] Furthermore, in step (1), the concentration of the tungsten source aqueous solution is 0.03-0.06M.

[0018] Furthermore, in step (1), the tungsten source aqueous solution is prepared by the following method: dissolving tungstic acid in water, adding hydrogen peroxide, and then stirring at 90-95° C. until completely dissolved to obtain the tungsten source aqueous solution.

[0019] Furthermore, the usage ratio of the tungsten source and water is (1-2) g: (20-40) mL.

[0020] Furthermore, the usage ratio of the tungsten source and hydrogen peroxide is (1-2) g: (15-20) mL.

[0021] Furthermore, the concentration of the hydrogen peroxide is 20-40wt%.

[0022] Furthermore, in step (1), the concentration of the hydrochloric acid solution is 5-10M.

[0023] Furthermore, in step (1), the mass ratio of oxalic acid to urea is 1:(1.5-2.5).

[0024] Furthermore, in step (1), the usage ratio of the oxalic acid and the tungsten source aqueous solution is 0.01 g:(15-20) mL.

[0025] Furthermore, in step (1), the WO3 seed layer precursor solution is spin-coated on the substrate, and the spin-coating conditions are: first spin-coating at a rotation speed of 800-1200 r / min for 3-7 s, and then spin-coating at a rotation speed of 3500-4500 r / min for 20-40 s.

[0026] Furthermore, in step (1), annealing treatment is performed at 450-550° C. for 2-3 h.

[0027] Furthermore, in step (2), a hydrothermal reaction is carried out at 150-200° C. for 20-24 h.

[0028] Furthermore, in step (2), annealing treatment is performed at 450-550° C. for 2-3 hours.

[0029] Furthermore, in step (3), the bismuth source is bismuth nitrate.

[0030] Furthermore, in step (3), the vanadium source is selected from ammonium metavanadate, ammonium vanadate and vanadium acetylacetonate oxide (C 10 H 14 O5V) one or more.

[0031] Furthermore, in step (3), the molar ratio of the bismuth source, the vanadium source and the citric acid is (0.5-1):(0.5-1):(1-2).

[0032] Furthermore, in step (3), the usage ratio of the bismuth source and nitric acid is (0.005-0.01) mol: (15-20) mL.

[0033] Furthermore, in step (3), the usage ratio of polyvinyl alcohol to nitric acid is (0.005-0.01) g:(0.5-2) mL.

[0034] Furthermore, in step (3), the volume ratio of acetic acid to nitric acid is (0.2-0.3):1.

[0035] Furthermore, in step (3), the BiVO4 precursor solution is spin-coated on a substrate covered with a WO3 film, and the spin-coating conditions are: first spin-coating at a rotation speed of 800-1200 r / min for 3-7 s, and then spin-coating at a rotation speed of 3500-4500 r / min for 20-40 s.

[0036] Furthermore, in step (3), annealing treatment is performed at 450-550° C. for 2-3 h.

[0037] Furthermore, in step (4), the titanium oxide precursor deposited by atomic layer deposition is tetrakis(dimethylamino)titanium (TDMAT) and water.

[0038] Furthermore, in step (4), the deposition temperature is 140-160°C.

[0039] Furthermore, in step (4), the thickness of the amorphous TiO2 layer is 1-10 nm.

[0040] The amorphous TiO2 layer provided by the present invention can also be used to improve the stability of other types of photoelectrodes.

[0041] The present invention protects a photocatalytic water-hydrogen production material prepared by the above method.

[0042] The present invention also protects the application of the above-mentioned photocatalytic water splitting hydrogen production material in photoelectrocatalysis.

[0043] Beneficial effects of the present invention:

[0044] The present invention prepares a WO3 / BiVO4 heterojunction photoelectrode by compounding WO3 and BiVO4, and utilizes the matching energy band positions and good visible light capture capabilities of the two to achieve efficient photoelectrochemical performance. In addition, an ultra-thin oxide protective layer is plated on the surface of the prepared photoelectrode by atomic layer deposition to achieve stable photoelectrochemical performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 These are the surface SEM images of the WO3 seed layer, WO3 film, WO3 / BiVO4 heterojunction photoelectrode, and WO3 / BiVO4 / TiO2 photoelectrode in Example 1; wherein, (a) is the surface SEM image of the WO3 seed layer, (b) is the surface SEM image of the WO3 film, (c) is the surface SEM image of the WO3 / BiVO4 heterojunction photoelectrode, and (d) is the surface SEM image of the WO3 / BiVO4 / TiO2 photoelectrode.

[0046] Figure 2 This is the cross-sectional TEM image of the WO3 / BiVO4 / TiO2 photoelectrode prepared in Example 1.

[0047] Figure 3 These are the XRD patterns of WO3, BiVO4, WO3 / BiVO4 and WO3 / BiVO4 / TiO2 in Example 1.

[0048] Figure 4 This is the X-ray photoelectron spectroscopy (XPS) analysis spectrum of the WO3 / BiVO4 / TiO2 photoelectrode prepared in Example 1; wherein, (a) is the surface chemical composition and chemical state distribution spectrum of the WO3 / BiVO4 / TiO2 photoelectrode measured by an X-ray photoelectron spectrometer, (b) is the XPS spectrum of the W element, (b) is the XPS spectrum of the Bi element, (c) is the XPS spectrum of the V element, and (d) is the XPS spectrum of the Ti element.

[0049] Figure 5 The photoelectrochemical JV curves of the WO3 photoelectrode, BiVO4 photoelectrode and WO3 / BiVO4 heterojunction photoelectrode in Example 1 are shown.

[0050] Figure 6 The JV curves of the WO3 / BiVO4 heterojunction photoelectrode in Example 1 and the WO3 / BiVO4 heterojunction photoelectrode in Example 2 are shown.

[0051] Figure 7 JV curves of the WO3 / BiVO4 heterojunction photoelectrode in Example 1 and the WO3 / BiVO4 heterojunction photoelectrode in Example 3.

[0052] Figure 8 These are the EIS spectrum curves and electron energy spectra of WO3, BiVO4, and WO3 / BiVO4 in Example 1; wherein (a) is the EIS spectrum curves of WO3, BiVO4, and WO3 / BiVO4, and (b) is the electron energy spectrum of WO3 / BiVO4 and a schematic diagram of the electron transport process.

[0053] Fig. 9 This is a stability test curve diagram of the WO3 / BiVO4 heterojunction photoelectrode and the WO3 / BiVO4 / TiO2 photoelectrode in Example 1.

[0054] Fig.10 This is a diagram showing the experimental results of photolysis of water using the WO3 / BiVO4 / TiO2 photoelectrode prepared in Example 1. DETAILED DESCRIPTION

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0056] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0057] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods, and the materials, reagents, etc. used are all available from commercial sources unless otherwise specified.

[0058] Example 1

[0059] A method for preparing a material for producing hydrogen by photolysis of water comprises the following steps:

[0060] (1) The WO3 seed layer was prepared by a sol-gel method. 1.25 g of tungstic acid (H2WO4) and 0.5 g of polyvinyl alcohol (PVA) were dissolved in 17 mL of 30 wt% hydrogen peroxide (H2O2), and then stirred with a magnetic stirrer until completely dissolved, finally forming a uniform, stable, and transparent WO3 seed layer precursor solution.

[0061] Dissolve 1.25g of tungstic acid (H2WO4) in 30mL of deionized water (H2O), then add 17mL of 30wt% hydrogen peroxide (H2O2), then heat the resulting solution on an electric furnace at about 95°C and stir continuously until it is completely dissolved, add an appropriate amount of deionized water to dilute the above solution to 100mL, and adjust the concentration of the H2WO4 solution to 0.05M.

[0062] 3 mL of the 0.05 M H2WO4 solution, 9 mL of ethanol, 4 mL of 6 M hydrochloric acid (HCl), 0.01 g of oxalic acid and 0.02 g of urea were placed in a beaker, a stirring bar was added, and the mixture was stirred on a magnetic stirrer until it was completely dissolved to obtain a WO3 hydrothermal colloid.

[0063] Using a MIDAS SYSTEM SPIN-1200T type coating machine, the WO3 seed layer precursor solution was first spin-coated on the surface of the FTO conductive glass sheet, and the coating was performed at a low speed of 1000r / min for 5s and a high speed of 4000r / min for 30s. Each time the wet film was spun, the surface must be uniform, and there must be no obvious dust that would cause uneven film. Finally, the wet film was placed in a muffle furnace for annealing at 500℃ for 2h, and the thickness of the obtained WO3 seed layer was about 100nm.

[0064] Place a FTO conductive glass sheet covered with a WO3 seed layer on the bottom of a 25mL reactor, then slowly pour 17mL of hydrothermal colloid into the reactor, then tighten the lid and place it in a 180℃ constant temperature drying oven for 24h. After the temperature drops naturally, take out the FTO conductive glass sheet, wash it with deionized water, and blow it dry with a nitrogen gun. Finally, place the FTO conductive glass sheet in a muffle furnace and anneal it at 500℃ for 2h to obtain a FTO conductive glass sheet (WO3 photoelectrode) covered with a WO3 film with a thickness of about 800nm.

[0065] (2) A WO3 / BiVO4 heterojunction photoelectrode was prepared by a sol-gel method. 0.005 mol of bismuth nitrate (Bi(NO3)3) was used as a bismuth source, 0.005 mol of ammonium metavanadate (NH4VO3) was used as a vanadium source, and 0.01 mol of citric acid was mixed together and added to 15 mL of 23.3% nitric acid (HNO3) to obtain a mixed solution. 0.008 g of PVA and 0.25 mL of acetic acid were added to 1 mL of the mixed solution, and the solution was fully stirred with a magnetic stirrer to dissolve the mixture completely, thereby obtaining a BiVO4 precursor solution.

[0066] The prepared BiVO4 precursor solution was evenly spin-coated on the surface of the FTO conductive glass sheet covered with WO3 film, and the coating was carried out at a low speed of 1000r / min for 5s and a high speed of 4000r / min for 30s. The wet film was then annealed at 500℃ in a muffle furnace for 2h to obtain a WO3 / BiVO4 heterojunction photoelectrode with one BiVO4 layer and a thickness of about 100nm.

[0067] (3) The amorphous TiO2 protective layer was prepared by atomic layer deposition (ALD). First, the surface of the prepared WO3 / BiVO4 heterojunction photoelectrode was cleaned with an ear-cleaning bulb. Then, the back of the sample and the conductive electrode were covered with conductive tape. Then, the sample was placed in the chamber and deposited at 150°C. The titanium oxide precursor was tetrakis(dimethylamino)titanium (TDMAT; Jiangsu Nanda Optoelectronic Materials Co., Ltd., China) and pure water. 40 cycles were performed at a deposition rate of / period, the thickness of the amorphous TiO2 protective layer is 2nm, and the photocatalytic water splitting hydrogen production material, namely WO3 / BiVO4 / TiO2 photoelectrode, is obtained.

[0068] Example 2

[0069] A method for preparing a material for producing hydrogen by photolysis of water is basically the same as that of Example 1, except that in step (2), there are two BiVO4 layers with a thickness of about 200 nm.

[0070] Example 3

[0071] A method for preparing a photocatalytic water hydrogen production material is basically the same as Example 1, except that: in step (3), 200 cycles are performed at a deposition rate of / period, and the thickness of the amorphous TiO2 protective layer is 10nm.

[0072] Test Example 1

[0073] The surface morphology of the WO3 seed layer, WO3 film, WO3 / BiVO4 heterojunction photoelectrode, and WO3 / BiVO4 / TiO2 photoelectrode in Example 1 was characterized by scanning electron microscopy (SEM). Figure 1 As shown, from Figure 1 As can be seen in (a), the WO3 seed layer is relatively dense and evenly covers the entire surface of the FTO conductive glass sheet, showing the characteristics of polycrystalline. Figure 1 (b) shows the WO3 porous nanostructure grown on the WO3 seed layer. It can be seen that the diameter of the WO3 grains is about 50-200nm. Figure 1 In (c), it can be clearly seen that the BiVO4 film almost covers the WO3 film. Then, after the TiO2 layer is deposited, Figure 1 As shown in (d), the surface morphology of the WO3 / BiVO4 heterojunction is basically unchanged, indicating that the TiO2 layer is very thin and evenly distributed on the surface.

[0074] Figure 2 This is a cross-sectional transmission electron microscope (TEM) image of the WO3 / BiVO4 / TiO2 photoelectrode prepared in Example 1. Figure 2 It can be seen that the thickness of the amorphous TiO2 protective layer is about 2nm.

[0075] Test Example 2

[0076] X-ray diffractometer (XRD) was used to analyze the structures of WO3, BiVO4, WO3 / BiVO4 and WO3 / BiVO4 / TiO2. Figure 3 As shown, from Figure 3It can be seen that the diffraction positions of pure WO3 and BiVO4 films correspond to standard cards JCPDS NO.33-1387 and JCPDS NO.75-2481, respectively, indicating that both WO3 and BiVO4 films have good crystalline structures. After depositing and annealing the BiVO4 layer on the WO3 film, the WO3 / BiVO4 heterojunction shows peaks corresponding to BiVO4 and WO3, indicating that no new compounds are formed. The XRD spectrum of the WO3 / BiVO4 / TiO2 sample has a nearly identical spectrum to the WO3 / BiVO4 heterojunction sample, and no XRD peak of TiO2 is observed, indicating that the TiO2 deposited by ALD at 150°C is amorphous.

[0077] Figure 4 This is the X-ray photoelectron spectroscopy (XPS) analysis spectrum of the WO3 / BiVO4 / TiO2 photoelectrode prepared in Example 1. Figure 4 In (a), several obvious peaks can be seen, revealing the presence of W, Bi, V and Ti elements; Figure 4 As can be seen in (b), W 6+ The peaks of ions at 37.9 eV and 35.8 eV correspond to W 4f 5 / 2 And W 4f 7 / 2 state; from Figure 4 As can be seen in (c), the peaks at 159.1eV and 164.4eV correspond to Bi 3+ Bi 4f ions 7 / 2 And Bi 4f 5 / 2 state; from Figure 4 As can be seen in (d), the peaks at 524.7 eV and 516.7 eV correspond to V 5+ V 2p of ions 1 / 2 and V2p 3 / 2 state; from Figure 4 As can be seen in (e), Ti 2p 3 / 2 and Ti 2p 1 / 2 The XPS peaks of the TiO2 layer are well symmetrical and are located at 458.4eV and 464.2eV, respectively. 4+ The XPS analysis results show that WO3 and BiVO4 thin films can be obtained on the surface of FTO conductive glass by hydrothermal method and sol-gel method.

[0078] Test Example 3

[0079] The WO3 photoelectrode, BiVO4 photoelectrode and WO3 / BiVO4 heterojunction photoelectrode in Example 1 were subjected to 100 mW / cm 2The photoelectrochemical performance test was carried out in a mixed electrolyte solution of 0.5M Na2SO4 and 0.5M Na2SO3 under Xe lamp irradiation, wherein the preparation method of BiVO4 photoelectrode is as follows: the BiVO4 precursor solution in Example 1 is evenly spin-coated on the surface of the FTO conductive glass sheet, and the spin coating is carried out at a low speed of 1000r / min for 5s and at a high speed of 4000r / min for 30s. Then the wet film is annealed at 500℃ in a muffle furnace for 2h to obtain a BiVO4 photoelectrode.

[0080] Test results such as Figure 5 As shown in the JV curve, it can be seen that the photocurrent obtained by the WO3 / BiVO4 heterojunction photoelectrode test is larger than that of the single WO3 and BiVO4 electrodes. The test results show that at 1.23V vs. RHE, the photocurrent density that the WO3 / BiVO4 heterojunction photoelectrode can obtain is about 1.7mA / cm 2 , while the photocurrent density that can be obtained by pure BiVO4 electrode is 0.56mA / cm 2 The photocurrent of the photoelectrode is about half of that of the WO3 / BiVO4 heterojunction photoelectrode. This is because when WO3 and BiVO4 form a heterojunction, the energy band matching position of the two is just conducive to the separation of photogenerated carriers. Figure 5 It can also be seen that the open circuit voltage of the WO3 / BiVO4 heterojunction photoelectrode reaches 0.21V vs.RHE.

[0081] The WO3 / BiVO4 heterojunction photoelectrode (WO3 / BiVO4-1 layer) in Example 1 and the WO3 / BiVO4 heterojunction photoelectrode (WO3 / BiVO4-2 layer) in Example 2 were subjected to 100 mW / cm 2 The photoelectrochemical performance was tested in a mixed electrolyte solution of 0.5M Na2SO4 and 0.5M Na2SO3 under Xe lamp irradiation. The test results are as follows Figure 6 As shown, it is explained that the thickness of WO3 / BiVO4 will also affect the photoelectrochemical performance of the photoelectrode.

[0082] The WO3 / BiVO4 heterojunction photoelectrode (WO3 / BiVO4 / 2nm TiO2) in Example 1 and the WO3 / BiVO4 heterojunction photoelectrode (WO3 / BiVO4 / 10nm TiO2) in Example 3 were subjected to 100mW / cm 2 The photoelectrochemical performance was tested in a mixed electrolyte solution of 0.5M Na2SO4 and 0.5MNa2SO3 under Xe lamp irradiation. The test results are as follows Figure 7As shown in the figure, the photocurrent density of the photoelectrode with a 2nm amorphous TiO2 protective layer is basically the same as that of the photoelectrode before deposition, but the stability of the photoelectrode is greatly improved. The photocurrent density of the photoelectrode with a 10nm amorphous TiO2 protective layer is attenuated compared to that of the photoelectrode before deposition, and the stability of the electrode is also improved.

[0083] Test Example 4

[0084] The electrochemical impedance spectra of WO3, BiVO4, and WO3 / BiVO4 in Example 1 were tested by an electrochemical workstation, and the electronic energy spectrum of WO3 / BiVO4 was tested. The test results are as follows: Figure 8 As shown, from Figure 8 As can be seen in (a), the arc of the EIS spectrum curve of the WO3 / BiVO4 heterojunction is significantly smaller than that of the semiconductor thin film sample of a single component, which indicates that the separation and transport efficiency of photogenerated electron-hole pairs will be significantly increased, which is consistent with the JV curve results of Test Example 3. Figure 8 (b) is the electronic energy spectrum of the WO3 / BiVO4 heterojunction and the schematic diagram of the electron transport process. In the standard hydrogen electrode (NHE) diagram, the conduction band position of BiVO4 is more negative than that of WO3, which is conducive to the migration of photogenerated electrons from the conduction band of BiVO4 to the conduction band of WO3, while the valence band position of WO3 is more positive than that of BiVO4, which is conducive to the migration of photogenerated holes from the valence band of WO3 to the valence band of BiVO4, thereby promoting the separation of photogenerated electron-hole pairs and improving the photoelectric conversion efficiency of the photoelectrode.

[0085] Test Example 5

[0086] The stability test was carried out on the WO3 / BiVO4 heterojunction photoelectrode and the WO3 / BiVO4 / TiO2 photoelectrode in Example 1, and the JT curve was completed using the three-electrode test system of Shanghai Chenhua Electrochemical Workstation (CHI-600D), including the working electrode (electrode sample), the counter electrode (Pt electrode) and the reference electrode (Ag / AgCl electrode). The electrolyte used in the test was a mixed solution of 0.5M Na2SO4 and 0.5M Na2SO3 (pH=7). A 300W xenon lamp was used as the light source in the test, and the light intensity density was calibrated using the ST series light intensity meter produced by Newport to ensure that the light intensity irradiated to the sample surface was 100mW / cm 2 .

[0087] The test results are as follows Fig. 9 Previous studies have shown that the photocurrent density of a single BiVO4 photoelectrode and a single WO3 photoelectrode will decay by about half after being exposed to light and tested in solution for 10 hours. Fig. 9It can be seen that after 11 hours of uninterrupted measurement, the photocurrent of the WO3 / BiVO4 / TiO2 photoelectrode of the present invention remains at 1.58 mA / cm 2 After 11 hours of measurement, the photocurrent of the WO3 / BiVO4 heterojunction photoelectrode began to decay slowly. After 11 hours of uninterrupted testing, the photocurrent decayed by about 16%, which shows that the deposition of the 2nm amorphous TiO2 protective layer increased the stability of the photoelectrode.

[0088] Test Example 6

[0089] The WO3 / BiVO4 / TiO2 photoelectrode prepared in Example 1 was subjected to a photolysis water experiment under the irradiation of a 300W xenon lamp. In the photoreactor, the photoanode (WO3 / BiVO4 / TiO2 photoelectrode) and the counter electrode (Pt wire) are in two different tube chambers, and the photolysis water reaction is carried out in 0.5M Na2SO4 and 0.5M Na2SO3 solutions. When the incident light irradiates the electrode surface, the WO3 / BiVO4 / TiO2 photoelectrode and the Pt counter electrode surface in the electrolyte solution begin to photolyze water to produce oxygen and hydrogen, respectively. As the number of electrons flowing through the external circuit increases, it can be clearly seen that more oxygen and hydrogen bubbles are adsorbed on the surfaces of the WO3 / BiVO4 / TiO2 photoelectrode and the Pt counter electrode. The H2 produced on the counter electrode was tested by gas chromatograph (GC), and the test results are shown as follows. Fig.10 As shown, after calculation, it is found that the Faraday efficiency of hydrogen production of the electrode remains at 89%, indicating that H2 is indeed generated during the photoelectrochemical test.

[0090] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Those skilled in the art should understand that other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing a material for producing hydrogen by photolysis of water, characterized in that: The following steps are involved: (1) dissolving a tungsten source and polyvinyl alcohol in hydrogen peroxide to obtain a WO3 seed layer precursor solution; A tungsten source aqueous solution, ethanol, hydrochloric acid solution, oxalic acid and urea are mixed to obtain a WO3 hydrothermal colloid; the WO3 seed layer precursor solution is coated on a substrate, and after annealing treatment, a substrate covered with a WO3 seed layer is obtained; (2) placing the substrate covered with the WO3 seed layer obtained in step (1) in a reactor, and then pouring the WO3 hydrothermal colloid obtained in step (1) into the reactor for hydrothermal reaction, taking out the substrate after the reaction is completed, and obtaining a substrate covered with a WO3 thin film after annealing; (3) mixing a bismuth source, a vanadium source, citric acid, nitric acid, polyvinyl alcohol and acetic acid to obtain a BiVO4 precursor solution; coating the BiVO4 precursor solution on the substrate covered with the WO3 thin film obtained in step (2), and obtaining a substrate covered with a WO3 / BiVO4 heterojunction after annealing; (4) Depositing an amorphous TiO2 layer on the substrate covered with the WO3 / BiVO4 heterojunction obtained in step (3) by atomic layer deposition to obtain the photocatalytic water splitting hydrogen production material on the substrate.

2. The preparation method according to claim 1, characterized in that: In step (1), the mass ratio of the tungsten source to polyvinyl alcohol is (1-2):(0.3-0.8), and the dosage ratio of the tungsten source to hydrogen peroxide is (1-2) g:(15-20) mL.

3. The preparation method according to claim 1, characterized in that: In step (2), a hydrothermal reaction is carried out at 150-200° C. for 20-24 h.

4. The preparation method according to claim 1, characterized in that: In step (3), the molar ratio of the bismuth source, ammonium metavanadate and citric acid is (0.5-1):(0.5-1):(1-2).

5. The preparation method according to claim 1, characterized in that: In step (3), the BiVO4 precursor solution is spin-coated on the substrate covered with the WO3 film, and the spin-coating conditions are: first spin-coating at a rotation speed of 800-1200 r / min for 3-7 s, and then spin-coating at a rotation speed of 3500-4500 r / min for 20-40 s.

6. The preparation method according to claim 1, characterized in that: In step (4), the titanium oxide precursor deposited by atomic layer deposition is tetrakis(dimethylamino)titanium and water.

7. The preparation method according to claim 1, characterized in that: In step (4), the deposition temperature is 140-160°C.

8. The preparation method according to claim 1, characterized in that: In step (4), the thickness of the amorphous TiO2 layer is 1-10 nm.

9. A photocatalytic water splitting hydrogen production material prepared by the method according to any one of claims 1 to 8.

10. Use of the photocatalytic water splitting hydrogen production material according to claim 9 in photoelectrocatalysis.

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