Monoclinic-phase bismuth vanadate photo-anode generated through regulation and control of chitosan as well as preparation method and application of monoclinic-phase bismuth vanadate photo-anode

Abstract

The invention discloses a monoclinic-phase bismuth vanadate photoanode generated through chitosan regulation and control and a preparation method and application of the monoclinic-phase bismuth vanadate photoanode. The bismuth vanadate photoanode is prepared from uniform casting film sol in which chitosan, a vanadium source and a bismuth source coexist through spin coating, film pre-fixing and calcination. Chitosan in the casting film sol promotes formation of monoclinic phase BiVO4, the surface has developed wormlike pore channels, and excellent solid-liquid mass transfer and bulk phase carrier separation capabilities are shown. Under the sunlight illumination intensity (100mW / cm < 2 >), natural seawater treated by photoelectrocatalytic sulfite can thoroughly inhibit chlorine evolution reaction, the photocurrent density can reach 6.03 mA / cm < 2 > (1.23 V vs.RHE), and meanwhile, the cathode can stably separate out hydrogen. The preparation method of the photo-anode is low in equipment requirement, simple in process and high in controllability and reproducibility, and has great application potential in the field of hydrogen production through photoelectrocatalytic decomposition of seawater.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor photoelectrodes and photoelectrocatalysis, and specifically relates to a chitosan-regulated monoclinic bismuth vanadate photoanode, a preparation method thereof, and an application thereof in photoelectrocatalytic decomposition of seawater to produce hydrogen. Background Art

[0002] The development of "green hydrogen" is of great significance for alleviating the energy shortage and carbon emission problems caused by the use of fossil fuels. Seawater is one of the most abundant natural resources on the earth. The use of seawater to produce "green hydrogen" is expected to provide a sustainable solution for saving freshwater resources and promoting the early realization of the "dual carbon" goal. The concept of hydrogen production from seawater was first proposed by Bockris and Williams in 1975 (Int. J. Hydrogen Energy, 1982, 7 (12): 919-923). It has developed to date and mainly includes three seawater hydrogen production technologies, namely electrocatalytic technology, photocatalytic technology and photoelectrocatalytic technology. Electrocatalytic technology requires a large bias voltage, consumes a lot of electricity, and has more side reactions; photocatalytic technology photogenerated carriers are easy to recombine, and the utilization efficiency of solar energy is low; and the photoelectrocatalytic technology that combines the above two technologies can make up for these shortcomings to a large extent, showing a broader application prospect in the field of "green hydrogen" production from seawater.

[0003] In the photoelectrocatalytic seawater hydrogen production system, since the oxygen evolution reaction on the photoanode involves a more complex four-electron transfer process, it proceeds relatively slowly in terms of kinetics and is the rate-limiting reaction that restricts the catalytic decomposition of seawater, and usually determines the overall hydrogen production efficiency of the system. In addition, there are high concentrations of chloride ions (~0.5M) in seawater, which tend to cause a two-electron chlorine evolution reaction at the photoanode that has more solid-liquid mass transfer and kinetic advantages, generating active chlorine that corrodes and destroys the photoanode interface microstructure, reducing the system's photocurrent density and hydrogen production performance. Therefore, the highly competitive chlorine evolution reaction places higher demands on the research and development of photoanodes that are adapted to the seawater environment, and it is still a huge challenge facing the current direct electrolysis of seawater for hydrogen production.

[0004] Various photoanodes for hydrogen production from seawater have been reported, mainly including TiO 2 、BiVO 4 , Fe 2 O 3 , WO 3 、Si, among which bismuth vanadate (BiVO 4 ) has a suitable band gap (~2.4eV), exhibits good chemical stability in neutral and weak alkaline electrolytes, and has abundant raw material reserves and low toxicity, making it suitable for large-scale applications. 4 Low carrier mobility (~0.1cm 2 V -1 s -1), short carrier diffusion length (~70nm) and low intrinsic conductivity lead to unsatisfactory photoelectric performance. In order to overcome these defects and inhibit the photoanode chlorine evolution reaction for better application in seawater hydrogen production, element doping and / or surface modification strategies are often used to improve BiVO 4 Photoelectrocatalytic hydrogen production from seawater. For example, the team led by Academician Zou Zhigang combined Mo element doping and RhO 2 Mo-BiVO prepared by surface deposition strategy 4 / RhO 2 The photoanode achieved 2.16 mA / cm in natural seawater 2 The photocurrent density of (1.0Vvs.RHE) was only 270min due to the corrosion damage of the photoanode by the chlorine evolution reaction (Energy Environ. Sci., 2011, 4, 4046-4051). Wang Lei's team at Inner Mongolia University 4 NiMoO was constructed and modified on the photoanode. x Protective layer, NiMoO x / BiVO 4 Excellent stability of more than 190 h can be achieved in natural seawater, with a photocurrent density of 3.0 mA / cm at 1.23 V vs. RHE 2 (J.Mater.Chem.A,2022,10,1270-1277), the team also used MoO 3 Surface modification strategies make BiVO 4 The photocurrent density of the photoanode in simulated seawater and natural seawater was increased to 4.30 mA / cm 2 (Appl. Catal. B-Environ., 2022, 304, 120883); Zhang Kan's team from Nanjing University of Science and Technology will contain [FeCl 4 ] unit polythiophene modified on BiVO 4 On the photoanode surface, the photoelectrocatalytic seawater reaches 4.72mA / cm 2 (1.23Vvs.RHE) photocurrent density, due to the presence of [FeCl 4 ] Inhibition of chlorine evolution reaction by polythiophene, BiVO 4 The photoanode can operate stably for 40 hours in the photoelectrocatalytic seawater decomposition test (Nat. Commun., 2024, 15, 2023). 4 The photoanode carrier concentration and conductivity are improved by modifying its surface with negative charge layers, inert layers and other protective layers to isolate seawater chloride ions and inhibit the chlorine evolution reaction, thereby improving the photoelectrocatalytic seawater hydrogen production performance. However, the existing technology has the problems of low photocurrent density and inability to completely inhibit the generation of active chlorine to achieve long-term chlorine repellency. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a chitosan-directed controlled generation of a monoclinic bismuth vanadate photoanode and a preparation method and application thereof. 4 Chitosan was introduced into the casting solution, and the amino groups on chitosan were used to react with BiVO 4 The strong interaction between vanadium and bismuth ions in the casting solution effectively avoids the imbalance of vanadium and bismuth ratio caused by the thermal evaporation loss of vanadium during the calcination process, thereby promoting the directional generation of monoclinic BiVO with narrower band gap and higher activity. 4 ; Chitosan is ablated and decomposed during the calcination process, promoting the formation of BiVO 4 The photoanode has a well-developed worm-like porous structure, which greatly improves the solid-liquid mass transfer efficiency and the separation and transport of bulk carriers, thereby greatly improving BiVO 4 Photoelectric properties; Monoclinic BiVO regulated by chitosan 4 The photoanode is further applied in sulfite-treated seawater. Since the sulfite added to the seawater has extremely fast oxidation kinetics, it is preferentially oxidized to completely inhibit the chlorine evolution reaction of seawater chloride ions, thereby showing excellent performance close to the theoretical photocurrent density and good performance stability.

[0006] In order to achieve the above purpose and solve the problems existing in the prior art, the present invention uses the following technical solutions:

[0007] A method for preparing a monoclinic bismuth vanadate photoanode regulated by chitosan comprises the following steps:

[0008] S1, adding chitosan sol to vanadium source solution, shaking and mixing thoroughly to obtain mixed sol;

[0009] S2, adding the bismuth source solution to the mixed sol obtained in step S1, shaking and letting it stand to obtain a casting sol;

[0010] S3, dropping the cast film sol obtained in step S2 on FTO conductive glass, spreading it evenly and letting it stand for spin coating, and then quickly drying the wet film after spin coating to achieve film pre-fixation, and finally calcining the film to obtain a chitosan-regulated monoclinic bismuth vanadate photoanode.

[0011] The molar ratio of vanadium to chitosan amino in the film casting sol is 1.65-16.10:1, and the molar ratio of vanadium to bismuth is 0.90-1:1.

[0012] In the step S1, the chitosan sol is prepared by dissolving chitosan in dilute acetic acid, and the chitosan amino concentration is 0.088-0.176 mol / L; the vanadium source solution is prepared by dissolving acetylacetonato vanadyl in dimethyl sulfoxide solution, and the concentration is 0.95-1.05 mol / L; and the bismuth source solution in the step S2 is prepared by dissolving bismuth nitrate pentahydrate in anhydrous acetic acid solution, and the concentration is 0.95-1.05 mol / L.

[0013] The standing time in step S2 is 10 to 40 minutes.

[0014] The standing time in step S3 is 20 to 30 seconds.

[0015] In step S3, the spin coating speed is 2000-3500 r / min, and the spin coating time is 25-35 s.

[0016] In the step S3, the rapid thermal drying is performed by using an infrared heating lamp, and the baking time is 20 to 30 minutes.

[0017] The calcination treatment in step S3 is carried out in an air atmosphere, with a heating rate of 2 to 8° C. / min, a calcination temperature of 450 to 500° C., and a holding time of 1.5 to 3 hours.

[0018] The chitosan prepared by the method of the present invention is used to regulate the generation of monoclinic bismuth vanadate photoanode in photoelectrocatalytic hydrogen production from seawater.

[0019] Sulfite-treated seawater is added as the electrolyte solution in the application.

[0020] Uniform casting sol is crucial for the preparation of bismuth vanadate photoanode by spin coating-calcination method. Since chitosan sol easily precipitates flocculent precipitates in common vanadium source and bismuth source solvents, how to make chitosan sol, vanadium source solution and bismuth source solution mutually dissolve to obtain uniform casting sol is a technical difficulty. Preliminary experiments found that chitosan sol and acetylacetonato vanadyl-dimethyl sulfoxide (V-DMSO) solution were first oscillated and mixed to disperse the chitosan sol in V-DMSO solution, and then bismuth nitrate-anhydrous acetic acid (Bi-HAc) solution was added to achieve mutual dissolution of chitosan sol, V-DMSO solution and Bi-HAc solution, thus successfully preparing uniform casting sol.

[0021] BiVO 4 Chitosan was introduced into the casting solution, and the amino groups on chitosan were used to react with BiVO 4 The strong interaction between vanadium and bismuth ions in the casting solution can effectively avoid the imbalance of vanadium and bismuth ratio caused by vanadium thermal evaporation loss. Therefore, the present invention prepares monoclinic BiVO with narrower band gap and higher activity under the control of chitosan. 4 .

[0022] Preferably, the standing time in step S2 is 10 to 40 minutes.

[0023] The casting sol in step S2 should not be left for too long, otherwise the chitosan sol will precipitate flocs. The technical solution preferably leaves it to stand for 10 to 40 minutes to ensure that the chitosan sol, V-DMSO solution and Bi-HAc solution are effectively miscible, and to avoid the precipitation of flocs of chitosan due to standing for too long.

[0024] Preferably, the rapid thermal drying in step S3 uses an infrared heating lamp, and the baking time is 20 to 30 minutes.

[0025] The infrared heating lamp has high thermal efficiency and can quickly transfer heat to the wet chitosan-V-Bi film to achieve rapid film fixation. Infrared rays have strong penetrating power and can heat deep into the wet film. The heating effect is uniform and cracking of the film precursor can be avoided.

[0026] The present invention further provides the use of the monoclinic bismuth vanadate photoanode generated by chitosan regulation in photoelectrocatalytic seawater hydrogen production, wherein the monoclinic bismuth vanadate photoanode regulated by chitosan is used as a working electrode (the back side is used as a test surface), a calomel electrode is used as a reference electrode, a platinum mesh is used as a counter electrode, and seawater treated with sulfite is added as an electrolyte solution. Since the sulfite (Formula 1) added to the seawater has a lower redox potential than the hydroxide (Formula 2) and the chloride ion (Formula 3), the oxidation of the sulfite occurs preferentially on the surface of the photoanode, thereby effectively inhibiting the occurrence of the chlorine evolution reaction, and at the same time releasing electrons through an external circuit to the platinum mesh cathode to reduce water to hydrogen (Formula 4).

[0027] SO 3 2- + 2OH - → SO 4 2- + H 2 O + 2e - E = -0.93 V vs. RHE (1)

[0028] 4OH - → O 2 + 2H 2 O + 4e - E = 0.401 V vs. RHE (2)

[0029] Cl - + 2OH - → ClO - + H 2 O + 2e - E = 0.89 V vs. RHE(3)

[0030] 2H 2 O+2e - →H 2 +2OH - E=-0.828V vs.RHE(4)

[0031] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0032] (1) The preparation method of chitosan-directed control to generate monoclinic bismuth vanadate photoanode is simple and easy. 4 The preparation of photoanodes mostly adopts the process reported by Kyoung-Shin Choi's team: electrodeposition of BiOI → drop coating of acetylacetonato vanadyl solution → calcination treatment (Energy Environ. Sci., 2012, 5, 8553–8557; Science, 2014, 343, 990-994). 4 The photoanode has a nanoporous structure and outstanding charge transport performance, and exhibits excellent photoelectrochemical performance. The method for preparing the bismuth vanadate photoanode proposed in the present invention adopts a two-step process of spin coating and calcination. The film can reach the target thickness by only spin coating once, and has a strong bonding force with the FTO substrate and is not easy to fall off. At the same time, the present invention has low equipment requirements, a simpler process, and stronger controllability and reproducibility. The prepared BiVO 4 The photoanode has well-developed worm-like channels and exhibits excellent solid-liquid mass transfer and carrier phase separation capabilities.

[0033] (2) Under the crystal phase regulation of chitosan, the bismuth vanadate photoanode tends to form a monoclinic phase structure. 4 There are mainly three crystal phases: monoclinic scheelite, tetragonal zircon and tetragonal scheelite. Among these three crystal phases, monoclinic BiVO 4 BiVO has been shown to be the best photocatalyst due to its narrow band gap and higher carrier separation efficiency. 4 The crystal phase is closely related to the vanadium and bismuth content in the precursor. When vanadium is deficient, it is conducive to the formation of a tetragonal phase structure with low catalytic activity during the calcination process. The present invention adds chitosan to the casting solution, and can generate a monoclinic BiVO with high catalytic activity under the condition of vanadium deficiency in the precursor (V / Bi<1). 4 .

[0034] (3) Chitosan-directed regulation to generate monoclinic bismuth vanadate photoanode completely inhibits the chlorine evolution reaction in sulfite-treated seawater, showing excellent performance close to the theoretical photocurrent density. Different from the strategy of surface modification of photoanode to repel chlorine and resist chlorine corrosion in the prior art, the present invention adds sulfite, which is more easily oxidized than chloride ions and hydroxide ions in thermodynamics and kinetics, to seawater, completely inhibits the chlorine evolution reaction and accelerates the photoanode reaction kinetics, thereby further improving the photocurrent density. 4 The coordinated regulation of the photoanode and the seawater electrolyte realizes the 2 ) under the conditions of photocatalytic 0.5M Na 2 SO 3 The photocurrent density of natural seawater treated can reach 6.03mA / cm 2 (1.23 V vs. RHE), in 0.9 M Na 2 SO 3 The photocurrent density in the treated simulated seawater (0.5M NaCl) can reach 7.12mA / cm 2 (1.23V vs. RHE), and can release hydrogen stably and for a long time at the cathode, showing great application potential in the field of photoelectrocatalytic decomposition of seawater to produce hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The appearance photo and surface SEM image of the monoclinic bismuth vanadate photoanode generated by chitosan regulation in Example 1 of the present invention;

[0036] Figure 2 The XRD spectrum of the monoclinic bismuth vanadate photoanode generated by chitosan regulation in Example 1 of the present invention;

[0037] Figure 3 The photoelectric response behavior curve of the monoclinic bismuth vanadate photoanode generated by chitosan regulation in Example 1 of the present invention;

[0038] Figure 4 This is a linear sweep voltammogram of a monoclinic bismuth vanadate photoanode generated by chitosan regulation in seawater electrolyte treated with sodium sulfite in Example 3 of the present invention;

[0039] Figure 5 This is a stability diagram of the hydrogen production performance of photoelectrocatalytic seawater and seawater treated with sodium sulfite using a monoclinic bismuth vanadate photoanode generated by chitosan regulation in Example 10 of the present invention. DETAILED DESCRIPTION

[0040] In order to more clearly illustrate the technical solution of the present invention, the following examples are listed. Unless otherwise stated, the raw materials, reactions and post-treatment methods shown in the examples are common raw materials on the market and technical methods well known to those skilled in the art.

[0041] The present invention discloses a method for preparing a monoclinic bismuth vanadate photoanode regulated by chitosan, which is prepared by spin coating, pre-fixing and calcining a uniform casting film sol in which chitosan, a vanadium source and a bismuth source coexist, and comprises the following steps:

[0042] S1: adding chitosan sol dropwise into vanadium source solution, shaking and fully mixing to obtain mixed sol;

[0043] S2: adding the bismuth source solution dropwise into the mixed sol obtained in step S1, shaking vigorously and letting it stand to obtain a uniform casting sol;

[0044] S3: dripping the cast film sol obtained in step S2 onto the FTO conductive glass, spreading it evenly and letting it stand for spin coating, and then quickly drying the wet film after spin coating to achieve film pre-fixation, and finally calcining the film to obtain the chitosan-regulated monoclinic bismuth vanadate photoanode.

[0045] Preferably, the molar ratio of vanadium to chitosan amino in the casting sol is 1.65-16.10:1, and the molar ratio of vanadium to bismuth is 0.90-1:1.

[0046] Preferably, the chitosan sol in step S1 is prepared by dissolving chitosan in dilute acetic acid, the chitosan amino concentration is 0.088-0.176 mol / L, and the vanadium source solution is vanadium acetylacetonate (VO(acac) 2 ) is dissolved in a dimethyl sulfoxide (DMSO) solution at a concentration of 0.95 to 1.05 mol / L. In step S2, the bismuth source solution is bismuth nitrate pentahydrate (Bi(NO 3 ) 3 ·5H 2 O) is dissolved in anhydrous acetic acid (HAc) solution with a concentration of 0.95-1.05 mol / L.

[0047] The standing time in step S2 is 10 to 40 minutes.

[0048] The standing time in step S3 is 20 to 30 seconds.

[0049] In step S3, the spin coating speed is 2000-3500 r / min, and the spin coating time is 25-35 s.

[0050] In the step S3, the rapid thermal drying is performed by using an infrared heating lamp, and the baking time is 20 to 30 minutes.

[0051] The calcination treatment in step S3 is carried out in an air atmosphere, with a heating rate of 2 to 8° C. / min, a calcination temperature of 450 to 500° C., and a holding time of 1.5 to 3 hours.

[0052] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art. The terms used 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.

[0053] Example 1

[0054] A chitosan-regulated monoclinic bismuth vanadate photoanode and a preparation method and application thereof, comprising the following steps:

[0055] S1: 2 g of chitosan (95% deacetylation degree) was dissolved in 100 mL of 3% by volume dilute acetic acid solution to obtain chitosan sol, wherein the chitosan amino concentration was 0.118 mol / L, 1.00 mol / L acetylacetonyl vanadyl solution was prepared with dimethyl sulfoxide as solvent, 0.4 mL of chitosan sol was added dropwise to 0.19 mL of acetylacetonyl vanadyl solution, and the mixture was shaken and mixed thoroughly to obtain a mixed sol;

[0056] S2: preparing a 1.00 mol / L bismuth nitrate solution with anhydrous acetic acid as solvent, adding 0.21 mL of the bismuth nitrate solution dropwise to the mixed sol obtained in step S1, shaking vigorously and standing for 30 min to obtain a uniform casting sol, wherein the molar ratio of vanadium to chitosan amino groups in the casting sol is 4.03:1, and the molar ratio of vanadium to bismuth is 0.90:1;

[0057] S3 FTO conductive glass is pre-sealed with transparent tape on the conductive surface, leaving 1×1cm 2 region, drop 50 μL of the casting sol obtained in step S2 on the FTO conductive glass, spread it evenly and let it stand for 25 seconds before spin coating, the spin coating speed is 2500 rpm, the spin coating time is 30 seconds, and the wet film after spin coating is quickly heat dried for 20 minutes using an infrared heating lamp to pre-fix the film, and finally calcined the film in a muffle furnace (heating rate 5°C / min, calcination temperature 500°C, insulation time 2h) to obtain a chitosan-regulated monoclinic bismuth vanadate photoanode.

[0058] Figure 1 This is the appearance photo and surface SEM image of the monoclinic bismuth vanadate photoanode generated by chitosan regulation in this example. Chitosan, as a natural organic polymer, can play a pore-forming function by being ablated and decomposed during the calcination process, such as Figure 1As shown in the figure, the monoclinic bismuth vanadate photoanode generated by chitosan directional regulation has a well-developed worm-like porous structure on its surface. The porous structure can not only enhance the mass transfer at the solid-liquid interface, but also promote the rapid migration of bulk carriers to the surface, thereby improving the carrier separation efficiency.

[0059] Figure 2 This is the XRD spectrum of the monoclinic bismuth vanadate photoanode generated by chitosan regulation in this embodiment. 4 Chitosan was introduced into the casting solution, and the amino groups on chitosan were used to react with BiVO 4 The strong interaction between vanadium and bismuth ions in the casting solution can effectively avoid the imbalance of vanadium and bismuth ratio caused by vanadium thermal evaporation loss, thereby promoting the directional generation of monoclinic BiVO with narrower band gap and higher activity. 4 (m-BiVO 4 ), while no chitosan was added to the casting solution, only tetragonal bismuth vanadate (t-BiVO 4 ), so chitosan induces the formation of m-BiVO under the condition of precursor vanadium deficiency (V / Bi<1) 4 plays an important role in.

[0060] Figure 3 This is the photoelectric response behavior curve of the monoclinic bismuth vanadate photoanode generated by chitosan regulation in this example. Since the migration and recombination of photogenerated carriers are competing processes, a higher photocurrent density means that more electrons are transferred to the cathode instead of recombining with photogenerated holes. It can be seen from the figure that the monoclinic bismuth vanadate photoanode generated by chitosan directional regulation has a larger photocurrent density (1.23V vs. RHE) than the photoanode without chitosan addition, indicating that the monoclinic bismuth vanadate photoanode regulated by chitosan has a stronger carrier separation ability.

[0061] Example 2

[0062] A chitosan-regulated monoclinic bismuth vanadate photoanode and a preparation method and application thereof, comprising the following steps:

[0063] S1: 2 g of chitosan (95% deacetylation degree) was dissolved in 100 mL of 3% by volume dilute acetic acid solution to obtain a chitosan sol, wherein the chitosan amino concentration was 0.118 mol / L. A 1.00 mol / L acetylacetonyl vanadyl solution was prepared using dimethyl sulfoxide as a solvent. 0.4 mL of the chitosan sol was added dropwise to 0.195 mL of the acetylacetonyl vanadyl solution, and the mixture was shaken and mixed thoroughly to obtain a mixed sol.

[0064] S2: a 1.00 mol / L bismuth nitrate solution is prepared with anhydrous acetic acid as solvent, and 0.205 mL of the bismuth nitrate solution is added dropwise to the mixed sol obtained in step S1, and the mixture is shaken vigorously and allowed to stand for 30 min to obtain a uniform casting sol, wherein the molar ratio of vanadium to chitosan amino groups in the casting sol is 4.13:1, and the molar ratio of vanadium to bismuth is 0.95:1;

[0065] S3 FTO conductive glass is pre-sealed with transparent tape on the conductive surface, leaving 1×1cm 2 region, drop 50 μL of the casting sol obtained in step S2 on the FTO conductive glass, spread it evenly and let it stand for 25 seconds before spin coating, the spin coating speed is 2500 rpm, the spin coating time is 30 seconds, and the wet film after spin coating is quickly heat dried for 20 minutes using an infrared heating lamp to pre-fix the film, and finally calcined the film in a muffle furnace (heating rate 5°C / min, calcination temperature 500°C, insulation time 2h) to obtain a chitosan-regulated monoclinic bismuth vanadate photoanode.

[0066] The photoelectrocatalytic performance of the monoclinic bismuth vanadate photoanode generated by chitosan regulation in this embodiment was evaluated by using a photoelectrocatalytic test system. The monoclinic bismuth vanadate photoanode regulated by chitosan was used as the working electrode (the back side was used as the test side), the calomel electrode was used as the reference electrode, and the platinum mesh was used as the counter electrode. Simulated seawater (0.5 M NaCl) and the addition of different concentrations of Na 2 SO 3 (0.3~1.1M) treated simulated seawater as electrolyte solution, at 100mW / cm 2 Under simulated solar irradiation, the photocurrent density at an applied bias voltage of 1.23 V vs. RHE was obtained, and the concentration of active chlorine in the electrolyte after photoelectrocatalysis was measured by N, N-diethyl-1, 4-phenylenediamine spectrophotometry (HJ 586-2010) (Table 1). It can be seen from the data in the table that when Na 2 SO 3 , due to Na 2 SO 3 Thermodynamically and kinetically, Na is more easily oxidized than chloride and hydroxide, and no active chlorine was detected during the experiment, indicating that the chlorine evolution reaction was completely suppressed. 2 SO 3 Oxidation instead of chlorine or oxygen evolution reaction can accelerate the photoanode reaction kinetics, thereby further improving the photocurrent density. 2 SO 3 The photocurrent density in the treated simulated seawater reached a maximum value (7.12 mA / cm 2 ), the photocurrent density close to the theoretical value means that the monoclinic bismuth vanadate photoanode generated by the directional regulation of chitosan has almost complete separation of bulk carriers in photoelectrocatalysis.

[0067] Table 1 Photocurrent density and active chlorine concentration in the electrolyte solution after test

[0068]

[0069] Example 3

[0070] A chitosan-regulated monoclinic bismuth vanadate photoanode and a preparation method and application thereof, comprising the following steps:

[0071] S1: 2 g of chitosan (95% deacetylation degree) was dissolved in 100 mL of 3% by volume dilute acetic acid solution to obtain a chitosan sol, wherein the chitosan amino concentration was 0.118 mol / L. A 1.00 mol / L acetylacetonyl vanadyl solution was prepared using dimethyl sulfoxide as a solvent. 0.5 mL of the chitosan sol was added dropwise to 0.195 mL of the acetylacetonyl vanadyl solution, and the mixture was shaken and mixed thoroughly to obtain a mixed sol.

[0072] S2: preparing a 1.00 mol / L bismuth nitrate solution with anhydrous acetic acid as solvent, adding 0.205 mL of the bismuth nitrate solution dropwise to the mixed sol obtained in step S1, shaking vigorously and standing for 30 min to obtain a uniform casting sol, wherein the molar ratio of vanadium to chitosan amino groups in the casting sol is 3.31:1, and the molar ratio of vanadium to bismuth is 0.95:1;

[0073] S3 FTO conductive glass is pre-sealed with transparent tape on the conductive surface, leaving 1×1cm 2 region, drop 50 μL of the casting sol obtained in step S2 on the FTO conductive glass, spread it evenly and let it stand for 25 seconds before spin coating, the spin coating speed is 2500 rpm, the spin coating time is 30 seconds, and the wet film after spin coating is quickly heat dried for 20 minutes using an infrared heating lamp to pre-fix the film, and finally calcined the film in a muffle furnace (heating rate 5°C / min, calcination temperature 500°C, insulation time 2h) to obtain a monoclinic bismuth vanadate photoanode regulated by chitosan.

[0074] The photoelectrocatalytic performance of the monoclinic bismuth vanadate photoanode generated by chitosan control in this embodiment was evaluated by using a photoelectrocatalytic test system. The monoclinic bismuth vanadate photoanode controlled by chitosan was used as the working electrode (the back side was used as the test surface), the calomel electrode was used as the reference electrode, and the platinum mesh was used as the counter electrode. 0.5 M Na 2 SO 3 Treated simulated seawater (0.5M NaCl), 0.5M Na 2 SO 3 Treated standard seawater (purchased from the National Marine Standards and Measurement Center, treated seawater calcium and magnesium precipitation was allowed to stand and then filtered) and 0.5M Na 2 SO3 Treated natural seawater (taken from Tianjin Bohai Bay, the treated seawater calcium and magnesium precipitates were allowed to stand and then filtered) was used as the electrolyte solution at 100mW / cm 2 Linear voltammetric scanning was performed under simulated solar radiation. Figure 4 It can be seen that when the applied bias is 1.23V vs.RHE, 0.5M Na 2 SO 3 The photocurrent densities of the treated simulated seawater, standard seawater, and natural seawater were 6.78 mA / cm 2 , 6.19mA / cm 2 、6.03mA / cm 2 After the photoelectrocatalytic reaction, no active chlorine was detected in the electrolyte, and the chlorine evolution reaction was completely inhibited.

[0075] Example 4

[0076] A chitosan-regulated monoclinic bismuth vanadate photoanode and a preparation method and application thereof, comprising the following steps:

[0077] S1: 2 g of chitosan (95% deacetylation degree) was dissolved in 100 mL of 3% by volume dilute acetic acid solution to obtain a chitosan sol, wherein the chitosan amino concentration was 0.118 mol / L. A 1.00 mol / L acetylacetonyl vanadyl solution was prepared using dimethyl sulfoxide as a solvent. 0.6 mL of the chitosan sol was added dropwise to 0.195 mL of the acetylacetonyl vanadyl solution, and the mixture was shaken and mixed thoroughly to obtain a mixed sol.

[0078] S2: preparing a 1.00 mol / L bismuth nitrate solution with anhydrous acetic acid as solvent, and adding 0.205 mL of the bismuth nitrate solution dropwise into the mixed sol obtained in step S1, and vigorously shaking and standing for 20 min to obtain a uniform casting sol, wherein the molar ratio of vanadium to chitosan amino groups in the casting sol is 2.75:1, and the molar ratio of vanadium to bismuth is 0.95:1;

[0079] S3 FTO conductive glass is pre-sealed with transparent tape on the conductive surface, leaving 1×1cm 2 region, drop 50 μL of the casting sol obtained in step S2 on the FTO conductive glass, spread it evenly and let it stand for 20 seconds before spin coating, the spin coating speed is 2500 rpm, the spin coating time is 30 seconds, and the wet film after spin coating is quickly heat dried for 20 minutes using an infrared heating lamp to pre-fix the film, and finally calcined the film in a muffle furnace (heating rate 5°C / min, calcination temperature 500°C, insulation time 2h) to obtain a chitosan-regulated monoclinic bismuth vanadate photoanode.

[0080] The photoelectrocatalytic performance of the monoclinic bismuth vanadate photoanode generated by chitosan control in this embodiment was evaluated by using a photoelectrocatalytic test system. The monoclinic bismuth vanadate photoanode controlled by chitosan was used as the working electrode (the back side was used as the test surface), the calomel electrode was used as the reference electrode, and the platinum mesh was used as the counter electrode. 0.5 M Na 2 SO 3 Treated natural seawater (taken from Tianjin Bohai Bay, the treated seawater calcium and magnesium precipitates were allowed to stand and then filtered) was used as the electrolyte solution at 100mW / cm 2 Under simulated solar irradiation, the photocurrent density is 5.95 mA / cm at an applied bias of 1.23 V vs. RHE. 2 After the photoelectrocatalytic reaction, active chlorine was not detected in the electrolyte and the chlorine evolution reaction was completely inhibited.

[0081] Example 5

[0082] A chitosan-regulated monoclinic bismuth vanadate photoanode and a preparation method and application thereof, comprising the following steps:

[0083] S1: 2 g of chitosan (95% deacetylation degree) was dissolved in 100 mL of 3% by volume dilute acetic acid solution to obtain chitosan sol, wherein the chitosan amino concentration was 0.118 mol / L, 1.00 mol / L acetylacetonyl vanadyl solution was prepared with dimethyl sulfoxide as solvent, 0.8 mL of chitosan sol was added dropwise to 0.195 mL of acetylacetonyl vanadyl solution, and the mixture was shaken and mixed thoroughly to obtain a mixed sol;

[0084] S2: a 1.00 mol / L bismuth nitrate solution is prepared with anhydrous acetic acid as solvent, and 0.205 mL of the bismuth nitrate solution is added dropwise to the mixed sol obtained in step S1, and the mixture is shaken vigorously and allowed to stand for 10 min to obtain a uniform casting sol, wherein the molar ratio of vanadium to chitosan amino groups in the casting sol is 2.07:1, and the molar ratio of vanadium to bismuth is 0.95:1;

[0085] S3 FTO conductive glass is pre-sealed with transparent tape on the conductive surface, leaving 1×1cm 2 region, drop 50 μL of the casting sol obtained in step S2 on the FTO conductive glass, spread it evenly and let it stand for 30 seconds before spin coating, the spin coating speed is 3000 rpm, the spin coating time is 30 seconds, and the wet film after spin coating is quickly heat dried for 25 minutes using an infrared heating lamp to pre-fix the film, and finally calcined the film in a muffle furnace (heating rate 5°C / min, calcination temperature 500°C, insulation time 2h) to obtain a chitosan-regulated monoclinic bismuth vanadate photoanode.

[0086] The photoelectrocatalytic performance of the monoclinic bismuth vanadate photoanode generated by chitosan control in this embodiment was evaluated by using a photoelectrocatalytic test system. The monoclinic bismuth vanadate photoanode controlled by chitosan was used as the working electrode (the back side was used as the test surface), the calomel electrode was used as the reference electrode, and the platinum mesh was used as the counter electrode. 0.5 M Na 2 SO 3 Treated natural seawater (taken from Tianjin Bohai Bay, the treated seawater calcium and magnesium precipitates were allowed to stand and then filtered) was used as the electrolyte solution at 100mW / cm 2 Under simulated solar irradiation, the photocurrent density is 5.82 mA / cm at an applied bias of 1.23 V vs. RHE. 2 After the photoelectrocatalytic reaction, active chlorine was not detected in the electrolyte and the chlorine evolution reaction was completely inhibited.

[0087] Example 6

[0088] A chitosan-regulated monoclinic bismuth vanadate photoanode and a preparation method and application thereof, comprising the following steps:

[0089] S1: 2 g of chitosan (95% deacetylation degree) was dissolved in 100 mL of 3% by volume dilute acetic acid solution to obtain chitosan sol, wherein the chitosan amino concentration was 0.118 mol / L, 1.00 mol / L acetylacetonyl vanadyl solution was prepared using dimethyl sulfoxide as solvent, 0.1 mL of chitosan sol was added dropwise to 0.19 mL of acetylacetonyl vanadyl solution, and the mixture was shaken and mixed thoroughly to obtain a mixed sol;

[0090] S2: preparing a 1.00 mol / L bismuth nitrate solution with anhydrous acetic acid as solvent, adding 0.21 mL of the bismuth nitrate solution dropwise to the mixed sol obtained in step S1, shaking vigorously and standing for 40 min to obtain a uniform casting sol, wherein the molar ratio of vanadium to chitosan amino groups in the casting sol is 16.10:1, and the molar ratio of vanadium to bismuth is 0.90:1;

[0091] S3 FTO conductive glass is pre-sealed with transparent tape on the conductive surface, leaving 1×1cm 2 region, drop 50 μL of the casting sol obtained in step S2 on the FTO conductive glass, spread it evenly and let it stand for 30 seconds before spin coating, the spin coating speed is 2000 rpm, the spin coating time is 25 seconds, and the wet film after spin coating is quickly heat dried by an infrared heating lamp for 30 minutes to achieve film pre-fixation, and finally the film is calcined in a muffle furnace (heating rate 2°C / min, calcination temperature 450°C, insulation time 3h) to obtain a monoclinic bismuth vanadate photoanode regulated by chitosan.

[0092] The photoelectrocatalytic performance of the monoclinic bismuth vanadate photoanode generated by chitosan control in this embodiment was evaluated by using a photoelectrocatalytic test system. The monoclinic bismuth vanadate photoanode controlled by chitosan was used as the working electrode (the back side was used as the test surface), the calomel electrode was used as the reference electrode, and the platinum mesh was used as the counter electrode. 0.5 M Na 2 SO 3 Treated natural seawater (taken from Tianjin Bohai Bay, the treated seawater calcium and magnesium precipitates were allowed to stand and then filtered) was used as the electrolyte solution at 100mW / cm 2 Under simulated solar irradiation, the photocurrent density is 5.75 mA / cm at an applied bias of 1.23 V vs. RHE. 2 After the photoelectrocatalytic reaction, active chlorine was not detected in the electrolyte and the chlorine evolution reaction was completely inhibited.

[0093] Example 7

[0094] A chitosan-regulated monoclinic bismuth vanadate photoanode and a preparation method and application thereof, comprising the following steps:

[0095] S1: 2 g of chitosan (95% deacetylation degree) was dissolved in 100 mL of 3% by volume dilute acetic acid solution to obtain chitosan sol, wherein the chitosan amino concentration was 0.118 mol / L, 1.00 mol / L acetylacetonyl vanadyl solution was prepared with dimethyl sulfoxide as solvent, 1.0 mL of chitosan sol was added dropwise to 0.195 mL of acetylacetonyl vanadyl solution, and the mixture was shaken and mixed thoroughly to obtain a mixed sol;

[0096] S2: preparing a 1.00 mol / L bismuth nitrate solution with anhydrous acetic acid as solvent, and adding 0.205 mL of the bismuth nitrate solution dropwise into the mixed sol obtained in step S1, and vigorously shaking and standing for 30 min to obtain a uniform casting sol, wherein the molar ratio of vanadium to chitosan amino groups in the casting sol is 1.65:1, and the molar ratio of vanadium to bismuth is 0.95:1;

[0097] S3 FTO conductive glass is pre-sealed with transparent tape on the conductive surface, leaving 1×1cm 2 region, drop 50 μL of the casting sol obtained in step S2 on the FTO conductive glass, spread it evenly and let it stand for 30 seconds before spin coating, the spin coating speed is 2000 rpm, the spin coating time is 35 seconds, and the wet film after spin coating is quickly heat dried by an infrared heating lamp for 30 minutes to achieve film pre-fixation, and finally the film is calcined in a muffle furnace (heating rate 8°C / min, calcination temperature 500°C, insulation time 1.5h) to obtain a chitosan-regulated monoclinic bismuth vanadate photoanode.

[0098] The photoelectrocatalytic performance of the monoclinic bismuth vanadate photoanode generated by chitosan control in this embodiment was evaluated by using a photoelectrocatalytic test system. The monoclinic bismuth vanadate photoanode controlled by chitosan was used as the working electrode (the back side was used as the test surface), the calomel electrode was used as the reference electrode, and the platinum mesh was used as the counter electrode. 0.5 M Na 2 SO 3 Treated natural seawater (taken from Tianjin Bohai Bay, the treated seawater calcium and magnesium precipitates were allowed to stand and then filtered) was used as the electrolyte solution at 100mW / cm 2 Under simulated solar irradiation, the photocurrent density is 5.52 mA / cm at an applied bias of 1.23 V vs. RHE. 2 After the photoelectrocatalytic reaction, active chlorine was not detected in the electrolyte and the chlorine evolution reaction was completely inhibited.

[0099] Example 8

[0100] A chitosan-regulated monoclinic bismuth vanadate photoanode and a preparation method and application thereof, comprising the following steps:

[0101] S1: 1.5 g of chitosan (95% deacetylation degree) was dissolved in 100 mL of 3% by volume dilute acetic acid solution to obtain chitosan sol, wherein the chitosan amino concentration was 0.088 mol / L, 0.95 mol / L acetylacetonyl vanadyl solution was prepared with dimethyl sulfoxide as solvent, 0.8 mL of chitosan sol was added dropwise to 0.20 mL of acetylacetonyl vanadyl solution, and the mixture was shaken and mixed thoroughly to obtain a mixed sol;

[0102] S2: preparing a 0.95 mol / L bismuth nitrate solution with anhydrous acetic acid as solvent, and adding 0.20 mL of the bismuth nitrate solution dropwise into the mixed sol obtained in step S1, and vigorously shaking and standing for 30 min to obtain a uniform casting sol, wherein the molar ratio of vanadium to chitosan amino groups in the casting sol is 2.70:1, and the molar ratio of vanadium to bismuth is 1:1;

[0103] S3 FTO conductive glass is pre-sealed with transparent tape on the conductive surface, leaving 1×1cm 2 region, drop 50 μL of the casting sol obtained in step S2 on the FTO conductive glass, spread it evenly and let it stand for 30 seconds before spin coating, the spin coating speed is 2000 rpm, the spin coating time is 30 seconds, and the wet film after spin coating is quickly heat dried by an infrared heating lamp for 30 minutes to achieve film pre-fixation, and finally the film is calcined in a muffle furnace (heating rate 5°C / min, calcination temperature 500°C, insulation time 2h) to obtain a monoclinic bismuth vanadate photoanode regulated by chitosan.

[0104] The photoelectrocatalytic performance of the monoclinic bismuth vanadate photoanode generated by chitosan control in this embodiment was evaluated by using a photoelectrocatalytic test system. The monoclinic bismuth vanadate photoanode controlled by chitosan was used as the working electrode (the back side was used as the test surface), the calomel electrode was used as the reference electrode, and the platinum mesh was used as the counter electrode. 0.5 M Na 2 SO 3 Treated natural seawater (taken from Tianjin Bohai Bay, the treated seawater calcium and magnesium precipitates were allowed to stand and then filtered) was used as the electrolyte solution at 100mW / cm 2 Under simulated solar irradiation, the photocurrent density is 5.68 mA / cm at an applied bias of 1.23 V vs. RHE. 2 After the photoelectrocatalytic reaction, active chlorine was not detected in the electrolyte and the chlorine evolution reaction was completely inhibited.

[0105] Example 9

[0106] A chitosan-regulated monoclinic bismuth vanadate photoanode and a preparation method and application thereof, comprising the following steps:

[0107] S1: 3 g of chitosan (95% deacetylation degree) was dissolved in 100 mL of 3% by volume dilute acetic acid solution to obtain a chitosan sol, wherein the chitosan amino concentration was 0.176 mol / L, and a 1.05 mol / L acetylacetonyl vanadyl solution was prepared using dimethyl sulfoxide as a solvent, and 0.2 mL of the chitosan sol was added dropwise to 0.20 mL of the acetylacetonyl vanadyl solution, and the mixture was shaken and mixed thoroughly to obtain a mixed sol;

[0108] S2: a 1.05 mol / L bismuth nitrate solution is prepared with anhydrous acetic acid as solvent, and 0.20 mL of the bismuth nitrate solution is added dropwise to the mixed sol obtained in step S1, and the mixture is shaken vigorously and allowed to stand for 30 min to obtain a uniform casting sol, wherein the molar ratio of vanadium to chitosan amino groups in the casting sol is 5.97:1, and the molar ratio of vanadium to bismuth is 1:1;

[0109] S3 FTO conductive glass is pre-sealed with transparent tape on the conductive surface, leaving 1×1cm 2 region, drop 50 μL of the casting sol obtained in step S2 on the FTO conductive glass, spread it evenly and let it stand for 30 seconds before spin coating, the spin coating speed is 3500 rpm, the spin coating time is 30 seconds, and the wet film after spin coating is quickly heat dried by an infrared heating lamp for 30 minutes to achieve film pre-fixation, and finally the film is calcined in a muffle furnace (heating rate 5°C / min, calcination temperature 480°C, insulation time 2.5h) to obtain a chitosan-regulated monoclinic bismuth vanadate photoanode.

[0110] The photoelectrocatalytic performance of the monoclinic bismuth vanadate photoanode generated by chitosan control in this embodiment was evaluated by using a photoelectrocatalytic test system. The monoclinic bismuth vanadate photoanode controlled by chitosan was used as the working electrode (the back side was used as the test surface), the calomel electrode was used as the reference electrode, and the platinum mesh was used as the counter electrode. 0.5 M Na 2 SO 3 Treated natural seawater (taken from Tianjin Bohai Bay, the treated seawater calcium and magnesium precipitates were allowed to stand and then filtered) was used as the electrolyte solution at 100mW / cm 2 Under simulated solar irradiation, the photocurrent density is 5.73 mA / cm at an applied bias of 1.23 V vs. RHE. 2 After the photoelectrocatalytic reaction, active chlorine was not detected in the electrolyte and the chlorine evolution reaction was completely inhibited.

[0111] Example 10

[0112] A chitosan-regulated monoclinic bismuth vanadate photoanode and a preparation method and application thereof, comprising the following steps:

[0113] S1: 2 g of chitosan (95% deacetylation degree) was dissolved in 100 mL of 3% dilute acetic acid solution, the amino concentration of chitosan was 0.118 mol / L, 1.00 mol / L acetylacetonyl vanadyl solution was prepared with dimethyl sulfoxide as solvent, 0.6 mL of chitosan sol was added dropwise to 0.19 mL of acetylacetonyl vanadyl solution, and the mixture was shaken and mixed thoroughly to obtain a mixed sol;

[0114] S2: preparing a 1.00 mol / L bismuth nitrate solution with anhydrous acetic acid as solvent, and adding 0.21 mL of the bismuth nitrate solution dropwise to the mixed sol obtained in step S1, and vigorously shaking and standing for 30 min to obtain a uniform casting sol, wherein the molar ratio of vanadium to chitosan amino groups in the casting sol is 2.68:1, and the molar ratio of vanadium to bismuth is 0.90:1;

[0115] S3 FTO conductive glass is pre-sealed with transparent tape on the conductive surface, leaving 1×1cm 2 region, drop 50 μL of the casting sol obtained in step S2 on the FTO conductive glass, spread it evenly and let it stand for 30 seconds before spin coating, the spin coating speed is 2500 rpm, the spin coating time is 30 seconds, and the wet film after spin coating is quickly heat dried by an infrared heating lamp for 30 minutes to achieve film pre-fixation, and finally the film is calcined in a muffle furnace (heating rate 5°C / min, calcination temperature 500°C, insulation time 2h) to obtain a chitosan-regulated monoclinic bismuth vanadate photoanode.

[0116] The photoelectrocatalytic performance of the monoclinic bismuth vanadate photoanode generated by chitosan regulation in this embodiment was evaluated by using a photoelectrocatalytic test system. The monoclinic bismuth vanadate photoanode regulated by chitosan was used as the working electrode (the back side was used as the test side), the calomel electrode was used as the reference electrode, and the platinum mesh was used as the counter electrode to simulate seawater (0.5 M NaCl), natural seawater (taken from Tianjin Bohai Bay), 0.5 M Na 2 SO 3 Treated simulated seawater, 0.5M Na 2 SO 3 Treated natural seawater (taken from Tianjin Bohai Bay, the treated seawater calcium and magnesium precipitates were allowed to stand and then filtered) was used as the electrolyte solution, respectively at 100mW / cm 2 The chronoamperometry test was performed under simulated solar radiation with an applied bias of 1.23V vs. RHE. Figure 5 As shown in the figure, when no sodium sulfite is added to the simulated seawater (0.5M NaCl) and natural seawater, a large amount of chloride ions react with chlorine on the surface of the photoanode, and the generated active chlorine corrodes and destroys the photoanode, causing the photocurrent density to drop rapidly. 2 SO 3 Treated simulated seawater and 0.5M Na 2 SO 3 The photocurrent density of the treated natural seawater (taken from the Bohai Bay in Tianjin, the treated seawater calcium and magnesium precipitates were allowed to stand and then filtered) did not decrease significantly during the 30-hour photoelectrocatalytic test, showing good performance stability. Active chlorine was not detected in the electrolyte after the reaction, and the chlorine evolution reaction was completely suppressed, which shows great application potential in the field of photoelectrocatalytic decomposition of seawater for hydrogen production.

[0117] The above are only preferred embodiments of the present invention. It should be noted that all technicians in this technical field can make changes or modifications to this embodiment without departing from the spirit of the attached claims and the scope of the principles shown in the present invention, and these changes should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a monoclinic bismuth vanadate photoanode regulated by chitosan, characterized in that: The steps include: S1, adding chitosan sol to vanadium source solution, shaking and mixing thoroughly to obtain mixed sol; S2, adding the bismuth source solution to the mixed sol obtained in step S1, shaking and letting it stand to obtain a casting sol; S3, dropping the cast film sol obtained in step S2 on FTO conductive glass, spreading it evenly and letting it stand for spin coating, and then quickly drying the wet film after spin coating to achieve film pre-fixation, and finally calcining the film to obtain a chitosan-regulated monoclinic bismuth vanadate photoanode.

2. The method for preparing a monoclinic bismuth vanadate photoanode regulated by chitosan according to claim 1, characterized in that: The molar ratio of vanadium to chitosan amino in the film casting sol is 1.65-16.10:1, and the molar ratio of vanadium to bismuth is 0.90-1:

1.

3. The method for preparing a monoclinic bismuth vanadate photoanode regulated by chitosan according to claim 1, characterized in that: In the step S1, the chitosan sol is prepared by dissolving chitosan in dilute acetic acid, and the chitosan amino concentration is 0.088-0.176 mol / L; the vanadium source solution is prepared by dissolving acetylacetonato vanadyl in dimethyl sulfoxide solution, and the concentration is 0.95-1.05 mol / L; and the bismuth source solution in the step S2 is prepared by dissolving bismuth nitrate pentahydrate in anhydrous acetic acid solution, and the concentration is 0.95-1.05 mol / L.

4. The method for preparing a monoclinic bismuth vanadate photoanode regulated by chitosan according to claim 1, characterized in that: The standing time in step S2 is 10 to 40 minutes.

5. The method for preparing a monoclinic bismuth vanadate photoanode regulated by chitosan according to claim 1, characterized in that: The standing time in step S3 is 20 to 30 seconds.

6. The method for preparing a monoclinic bismuth vanadate photoanode regulated by chitosan according to claim 1, characterized in that: In step S3, the spin coating speed is 2000-3500 r / min, and the spin coating time is 25-35 s.

7. The method for preparing a monoclinic bismuth vanadate photoanode regulated by chitosan according to claim 1, characterized in that: In the step S3, the rapid thermal drying is performed by using an infrared heating lamp, and the baking time is 20 to 30 minutes.

8. The method for preparing a monoclinic bismuth vanadate photoanode regulated by chitosan according to claim 1, characterized in that: The calcination treatment in step S3 is carried out in an air atmosphere, with a heating rate of 2 to 8° C. / min, a calcination temperature of 450 to 500° C., and a holding time of 1.5 to 3 hours.

9. The chitosan prepared by the method of claim 1 is used to regulate the generation of monoclinic bismuth vanadate photoanode in photoelectrocatalytic seawater hydrogen production, and sulfite-treated seawater is added as an electrolyte solution.

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