A phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate and its preparation method.

Abstract

This invention discloses a phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate and its preparation method, belonging to the field of electrode material technology. This invention provides a photoelectrode comprising a BiVO4 layer, a P-C3N4 layer, and a nickel borate (NiBi) layer. The P-C3N4 layer, acting as a hole transport layer, can rapidly conduct electrons and holes separated under illumination, reducing surface charge recombination and passivating BiVO4 interface defects, thus greatly improving the performance of the photoelectrode. The NiBi layer, acting as a co-catalyst, can effectively isolate photogenerated electrons, reducing photogenerated electron-hole pair recombination in the BiVO4 photoelectrode, while simultaneously improving the surface catalytic oxygen production efficiency of BiVO4. Ultimately, a nickel borate-loaded phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode with strong photogenerated carrier transport capability and good stability is obtained.

Description

Technical Field

[0001] This invention belongs to the field of electrode material technology, and particularly relates to a phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate and its preparation method. Background Technology

[0002] Solar energy, as a new and environmentally friendly renewable energy source, has received much attention in addressing the energy crisis and energy shortage. In recent years, the energy conversion efficiency of solar energy has been relatively low, so improving the utilization rate of solar energy has become an urgent problem to be solved. Photoelectrochemical water splitting (PEC) can directly convert solar energy into easily stored hydrogen energy. Photoelectrochemistry is a process of electrochemistry driven by light. It refers to the redox reaction that occurs when photogenerated electron-hole pairs generated on the semiconductor surface in contact with the electrolyte are separated by the electric field of the semiconductor / electrolyte junction and react with ions in the solution.

[0003] Recently, BiVO4 has attracted widespread attention as a photoanode material for PEC (Polymer Enzyme-Oxide-Cylinder) due to its suitable band structure, band gap of 2.40–2.50 eV, favorable conduction band edge position (≈0.1 eV) which is conducive to H2 evolution, and a maximum photocurrent density estimated at 7.5 mA cm⁻¹. -2 The theoretical conversion efficiency of solar energy to hydrogen is 9.2%. However, the actual performance of pure BiVO4 photoanodes is far lower than the theoretical value due to inherent drawbacks such as weak light absorption, poor photogenerated carrier separation and transport performance, and poor surface catalytic oxygen production kinetics. Therefore, how to modify BiVO4 to give it strong photogenerated carrier transport capability and good stability has become an urgent technical problem to be solved in this field. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The present invention provides a phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate, comprising a conductive substrate and a BiVO4 (bismuth vanadate) layer, a P-C3N4 (phosphorus-doped carbon nitride) layer and a nickel borate (NiBi) layer sequentially loaded on the conductive substrate;

[0007] The P-C3N4 layer is composed of P-C3N4 nanosheets; the nickel borate layer is attached to the P-C3N4 layer and the BiVO4 layer.

[0008] Technical Principle: This invention provides a photoelectrode comprising a BiVO4 layer, a P-C3N4 layer, and a nickel borate (NiBi) layer. The P-C3N4 layer, as a hole transport layer, can rapidly conduct electrons and holes that separate under illumination, reducing surface charge recombination, passivating BiVO4 interface defects, and greatly improving the catalytic performance and stability of the electrode. The NiBi layer, as a cocatalyst, can effectively isolate photogenerated electrons, reduce the recombination of photogenerated electron-hole pairs in the BiVO4 photoelectrode, and improve the surface catalytic oxygen production efficiency of BiVO4. Ultimately, a phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate is obtained, which has strong photogenerated carrier transport capability and good stability.

[0009] The present invention also provides a method for preparing the phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate as described in the above technical solution, comprising the following steps:

[0010] (1) BiVO4 is deposited on a conductive substrate to form a BiVO4 layer, thereby obtaining a BiVO4 photoelectrode;

[0011] (2) Melamine and tetrabutylammonium hexafluorophosphate are dissolved in anhydrous ethanol, heated and calcined to obtain powder; the powder is mixed with ethanol to obtain a spraying liquid; the spraying liquid is deposited on the BiVO4 photoelectrode obtained in step (1) to form a P-C3N4 layer, and a P-C3N4 / BiVO4 composite photoelectrode is obtained.

[0012] (3) Mix potassium borate buffer solution and nickel sulfate hexahydrate to obtain precursor liquid A; deposit the precursor liquid A on the P-C3N4 / BiVO4 composite photoelectrode obtained in step (2) to form a nickel borate layer, and obtain the phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate (NiBi / P-C3N4 / BiVO4 composite photoelectrode).

[0013] This invention first deposits BiVO4 on a conductive substrate to form a BiVO4 layer, then deposits phosphorus-doped carbon nitride (P-C3N4) on the surface of the BiVO4 photoelectrode to form nanosheets, and then deposits NiBi to obtain a phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate. The operation is simple and safe, the materials are readily available, and it can be mass-produced.

[0014] Furthermore, step (1) specifically involves:

[0015] A. A solution A is obtained by mixing nitric acid solution, potassium iodide (KI) and bismuth nitrate pentahydrate (Bi(NO3)3·5H2O); p-benzoquinone is dissolved in ethanol and sonicated to obtain solution B; solution A and solution B are mixed to obtain precursor liquid B; precursor liquid B is deposited on a conductive substrate to form a BiOI film, thus obtaining a conductive substrate with a BiOI film deposited on its surface.

[0016] B. Mix vanadium acetylacetonate and dimethyl sulfoxide to obtain solution C; drop solution C onto the conductive substrate on which the surface-deposited BiOI film was obtained in step A, and after annealing, alkali washing, water washing and drying, a BiVO4 layer is formed to obtain a BiVO4 photoelectrode.

[0017] Furthermore, in step A, the ratio of the amount of nitric acid solution, potassium iodide, and bismuth nitrate pentahydrate used is 25 mL: 0.4 mol: 0.04 mol; the pH value of the nitric acid solution is 1.6 to 1.8.

[0018] Furthermore, in step A, the ratio of p-benzoquinone to ethanol is 0.23 mol: 10 mL.

[0019] Furthermore, in step A, the ultrasound duration is 3 to 5 minutes.

[0020] Furthermore, in step A, the process conditions for the deposition precursor fluid B are as follows: initial voltage -0.1V, sampling interval 0.1s, deposition time 150–200s, settling time 0s, and sensitivity 1×10⁻⁶. -3 A. The settling time represents the waiting time before deposition; 0s indicates no waiting and direct deposition.

[0021] Furthermore, in step A, the deposition of the precursor liquid B is carried out using the time-current curve method; during deposition, the conductive substrate is the working electrode, the platinum mesh is the counter electrode, and Ag / AgCl is the reference electrode.

[0022] Furthermore, in step A, the conductive substrate is fluorine-doped tin oxide (FTO) conductive glass.

[0023] Furthermore, in step A, the conductive substrate includes a pretreatment step before deposition of the precursor solution B; the pretreatment is as follows: the conductive substrate is cut into 2×3cm dimensions using a glass cutting table, and then ultrasonically washed with acetone, ethanol and tertiary water for 15 minutes each, and then placed in an oven to dry after washing.

[0024] Furthermore, in step B, the ratio of acetylacetone vanadium oxide to dimethyl sulfoxide is 0.2 mol: 1 mL.

[0025] Furthermore, in step B, the dripping volume is 25 μL / cm. 2 .

[0026] Furthermore, in step B, the annealing treatment is carried out at a temperature of 440–460°C for 2 hours.

[0027] Furthermore, in step B, the concentration of the alkaline solution used for alkaline washing is 1 mol / L; the alkaline solution is NaOH solution; the alkaline washing method is immersion; and the immersion time is 15–25 min. This invention removes excess V₂O₅ through alkaline washing.

[0028] Furthermore, in step (2), the mass ratio of melamine to tetrabutylammonium hexafluorophosphate is 10:1. This invention controls the amount of P doping in the P-C3N4 layer by controlling the mass ratio of melamine to tetrabutylammonium hexafluorophosphate; controlling the amount of P doping within the above range has the advantages of improving conductivity and photocatalytic performance.

[0029] Furthermore, in step (2), the calcination temperature is 240–260°C, and the time is 3 hours. This invention achieves phosphorus-doped carbon nitride by calcination causing deamination condensation of melamine and tetrabutylhexafluorophosphate.

[0030] Furthermore, in step (2), the mass ratio of the powder to the volume ratio of ethanol is 1:1 (mg:mL).

[0031] Furthermore, in step (2), the deposition spraying liquid is applied by spraying; the process conditions for the deposition spraying liquid are: heating plate temperature of 200℃, and the amount of spraying liquid used is 0.5~1mL / cm. 2 The settling time is 0 seconds. Under the above conditions, the deposition of the spraying liquid in this invention is beneficial to the formation of nano-carbon nitride.

[0032] Furthermore, in step (2), the deposition spray solution is followed by a reheating, rinsing, and heating step; the reheating temperature is 230-280℃, and the time is 30 min; the rinsing reagent is grade III water; the heating temperature is 60℃, and the time is 10 min. This invention achieves tight adhesion of P-C3N4 to the BiVO4 photoelectrode through reheating.

[0033] Furthermore, in step (3), the ratio of the amount of potassium borate buffer solution to nickel sulfate hexahydrate (NiSO4·6H2O) is 0.5 mol: 1 mmol; the pH value of the potassium borate buffer solution is 9.5.

[0034] Furthermore, in step (3), the deposition precursor fluid A is deposited via electrochemical deposition; the deposition conditions for the precursor fluid A are: deposition temperature at room temperature, potential at 0V, running time at 10s, sampling interval at 0.1s, settling time at 2s, and sensitivity at 1×10⁻⁶. -3 A, the light intensity is 100mW / cm² -2 The present invention deposits precursor fluid A under the above conditions, which has the advantages of low energy consumption and simple operation.

[0035] Furthermore, in step (3), the deposition of the precursor liquid A is carried out by the time-current curve method; during deposition, the conductive substrate is the working electrode, the platinum mesh is the counter electrode, and Ag / AgCl is the reference electrode.

[0036] Compared with the prior art, the present invention has the following advantages and technical effects:

[0037] The phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode supported on nickel borate provided by this invention can improve hole transport rate and oxygen evolution efficiency, reduce recombination, passivate BiVO4 interface defects, and improve the photoelectric performance of the photoanode. The preparation method provided by this invention is simple and safe to operate, uses readily available materials, and can be mass-produced. Attached Figure Description

[0038] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0039] Figure 1 SEM image of the BiVO4 photoelectrode prepared in step (1) of Example 1;

[0040] Figure 2 The XRD patterns are of the BiVO4 photoelectrode in step (1) of Example 1, the C3N4 / BiVO4 composite photoelectrode in Comparative Example 1, the P-C3N4 / BiVO4 composite photoelectrode in step (2) of Example 1, and the NiBi / P-C3N4 / BiVO4 composite photoelectrode in step (3) of Example 1.

[0041] Figure 3 TEM image of the NiBi / P-C3N4 / BiVO4 composite photoelectrode prepared in Example 1;

[0042] Figure 4 The graph shows the oxygen evolution efficiency as a function of voltage for the BiVO4 photoelectrode in step (1), the P-C3N4 / BiVO4 composite photoelectrode in step (2), and the NiBi / P-C3N4 / BiVO4 composite photoelectrode in step (3) of Example 1.

[0043] Figure 5 The photoluminescence spectra of the BiVO4 photoelectrode in step (1) and the P-C3N4 / BiVO4 composite photoelectrode in step (2) of Example 1 are shown.

[0044] Figure 6Linear scan voltammetric curves of the BiVO4 photoelectrode in step (1), the P-C3N4 / BiVO4 composite photoelectrode in step (2), and the NiBi / P-C3N4 / BiVO4 composite photoelectrode in step (3) of Example 1 in the presence of a hole trapping agent.

[0045] Figure 7 Linear scan voltammetric curves of the BiVO4 photoelectrode in step (1), the P-C3N4 / BiVO4 composite photoelectrode in step (2), and the NiBi / P-C3N4 / BiVO4 composite photoelectrode in step (3) of Example 1 without a hole trapping agent. Detailed Implementation

[0046] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] In this embodiment of the invention, room temperature refers to "25±2℃".

[0049] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels.

[0050] Example 1

[0051] A phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate consists of FTO conductive glass and a BiVO4 layer, a P-C3N4 layer and a NiBi layer sequentially loaded on the FTO conductive glass; the P-C3N4 layer is composed of P-C3N4 nanosheets, and the NiBi layer is attached to the P-C3N4 layer and the BiVO4 layer.

[0052] The fabrication process of the phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate is as follows:

[0053] (1) Take a 20×15cm piece of FTO conductive glass and cut it into 2×3cm pieces using a glass cutting table. Wash it with acetone, ethanol, and tertiary water by sonication for 15min each. After washing, dry it in an oven to obtain pretreated FTO conductive glass. Take 25mL of nitric acid solution with a pH of 1.7 and place it in a 100mL beaker. Add 0.4mol potassium iodide (KI) and 0.04mol bismuth nitrate pentahydrate (Bi(NO3)3·5H2O). Stir thoroughly until the solution is clear and transparent to obtain solution A. Take 10mL of anhydrous ethanol and place it in a beaker. Add 0.23mol p-benzoquinone and sonicate for 5min until the precipitate is completely dissolved to obtain solution B. Solution A and solution B were mixed and stirred until fully miscible to obtain precursor solution B. Precursor solution B was used as the electrolyte. The pretreated FTO conductive glass was used as the working electrode, a platinum mesh as the counter electrode, and Ag / AgCl as the reference electrode. Electrodeposition was performed using the time-current curve method. The electrodeposition conditions were: initial voltage -0.1V, sampling interval 0.1s, deposition time 180s, settling time 0s, and sensitivity 1×10⁻⁶. -3 A. After electrodeposition, the film is rinsed with tertiary water and dried to obtain FTO conductive glass with a BiOI film deposited on it. This glass is then cut into 2×1cm pieces using a glass cutting stage and placed on a corundum sheet, with a 2mm distance between adjacent cut FTO conductive glasses. 1mL of dimethyl sulfoxide (DMSO) is added, along with 0.2mol of vanadium acetylacetonate, and stirred vigorously until no obvious precipitate is obtained, yielding solution C. 50μL (the amount used for each cut FTO conductive glass) of solution C is taken using a 100μL pipette and dropped onto the BiOI film surface. The corundum sheet is then placed in a muffle furnace and heated to 450℃ at a rate of 2℃ / min, calcined for 2h, and then cooled to room temperature to obtain the calcined FTO conductive glass. The calcined FTO conductive glass is placed in a petri dish, soaked in 1mol / L NaOH solution for 15min, rinsed with tertiary water, and dried to obtain a BiVO4 photoelectrode.

[0054] (2) Melamine and tetrabutylammonium hexafluorophosphate were mixed at a mass ratio of 10:1 and dissolved in anhydrous ethanol. The mixture was stirred and heated at 80°C for 0.5 h, then calcined at 240°C for 3 h, ground, dissolved in water, ultrasonically crushed, and dried to obtain a powder. 50 mL of anhydrous ethanol was added to 50 mg of the powder, crushed for 1 h, and centrifuged for 3 min to obtain a spraying solution. A heating plate was set to 200°C, and 1 mL of the spraying solution was taken from the spray gun (the spraying solution volume is 0.5 mL / cm). 2The above-mentioned spraying liquid is used to spray the BiVO4 photoelectrode obtained in step (1). After the spraying is completed, it is placed in a muffle furnace and reheated at 230°C for 30 minutes. Then it is rinsed with three-stage water and heated on a heating plate at 60°C for 10 minutes to obtain the P-C3N4 / BiVO4 composite photoelectrode.

[0055] (3) Take 0.5 mol of potassium borate buffer solution with a pH of 9.5, add 1 mmol of nickel sulfate hexahydrate (NiSO4·6H2O), and stir until the solution is clear and transparent to obtain precursor fluid A. Use the obtained precursor fluid A as the electrolyte, the P-C3N4 / BiVO4 composite photoelectrode obtained in step (2) as the working electrode, a platinum mesh as the counter electrode, and Ag / AgCl as the reference electrode. Electrodeposition is performed using the time-current curve method. The electrodeposition conditions are: deposition temperature is room temperature, potential is 0V, running time is 10s, sampling interval is 0.1s, rest time is 2s, and sensitivity is 1×10 -3 A, the light intensity is 100mW / cm² -2 After electrodeposition, the working electrode was rinsed with three-stage water and dried to obtain a phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate (NiBi / P-C3N4 / BiVO4 composite photoelectrode).

[0056] Comparative Example 1

[0057] The specific preparation steps of a C3N4 / BiVO4 composite photoelectrode are as follows:

[0058] Step (1) is the same as in Example 1;

[0059] (2) Dissolve 50mg of melamine in 50mL of anhydrous ethanol, crush for 1h and centrifuge for 3min to obtain a spraying solution; select a heating plate and set the temperature to 200℃, take 1ml of the above spraying solution with the spray gun and spray the BiVO4 photoelectrode obtained in step (1) by spraying. After the spraying is completed, place it in a muffle furnace and reheat at 230℃ for 30min, then rinse with three-stage water, and heat on a heating plate at 60℃ for 10min to obtain a C3N4 / BiVO4 composite photoelectrode.

[0060] Figure 1 This is a SEM image of the BiVO4 photoelectrode prepared in step (1) of Example 1. From... Figure 1 It can be seen that the microstructure of the BiVO4 photoelectrode is worm-like nanoparticles.

[0061] Figure 2The images show the XRD patterns of the BiVO4 photoelectrode in step (1) of Example 1, the C3N4 / BiVO4 composite photoelectrode in Comparative Example 1, the P-C3N4 / BiVO4 composite photoelectrode in step (2) of Example 1, and the NiBi / P-C3N4 / BiVO4 composite photoelectrode in step (3) of Example 1. Figure 2 It can be seen that Example 1 successfully prepared a NiBi / P-C3N4 / BiVO4 composite photoelectrode.

[0062] Figure 3 This is a TEM image of the NiBi / P-C3N4 / BiVO4 composite photoelectrode prepared in Example 1. From... Figure 3 It can be seen that there is a layer of P-C3N4 nanosheets on the surface of BiVO4, indicating that the P-C3N4 layer is attached to the BiVO4 layer. At the same time, an amorphous material NiBi can be seen attached to both the P-C3N4 layer and the BiVO4 layer.

[0063] Figure 4 The graph shows the oxygen evolution efficiency as a function of voltage for the BiVO4 photoelectrode in step (1), the P-C3N4 / BiVO4 composite photoelectrode in step (2), and the NiBi / P-C3N4 / BiVO4 composite photoelectrode in step (3) of Example 1. from Figure 4 It can be seen that the oxygen evolution efficiencies of the BiVO4 photoelectrode, the P-C3N4 / BiVO4 composite photoelectrode, and the NiBi / P-C3N4 / BiVO4 composite photoelectrode are 34.81%, 33.18%, and 93.79%, respectively, indicating that the NiBi / P-C3N4 / BiVO4 composite photoelectrode has excellent oxygen evolution performance.

[0064] Figure 5 The images show the photoluminescence spectra of the BiVO4 photoelectrode in step (1) and the P-C3N4 / BiVO4 composite photoelectrode in step (2) of Example 1. Figure 5 It can be seen that, compared with the unmodified BiVO4 photoelectrode, the emission intensity of the P-C3N4 / BiVO4 composite photoelectrode obtained by loading P-C3N4 is reduced, thereby suppressing carrier recombination.

[0065] Figure 6 Linear scan voltammetric curves of the BiVO4 photoelectrode in step (1), the P-C3N4 / BiVO4 composite photoelectrode in step (2), and the NiBi / P-C3N4 / BiVO4 composite photoelectrode in step (3) of Example 1 in the presence of a hole trapping agent. Figure 6It can be seen that, under test conditions with hole trapping agents, compared with BiVO4 photoelectrode and P-C3N4 / BiVO4 composite photoelectrode, NiBi / P-C3N4 / BiVO4 composite photoelectrode can achieve a higher photocurrent density under the same external voltage.

[0066] Figure 7 Linear scan voltammetric curves of the BiVO4 photoelectrode in step (1), the P-C3N4 / BiVO4 composite photoelectrode in step (2), and the NiBi / P-C3N4 / BiVO4 composite photoelectrode in step (3) of Example 1 without a hole trapping agent. Figure 7 It can be seen that, under test conditions without hole scavengers, compared to the BiVO4 photoelectrode, both the P-C3N4 / BiVO4 composite photoelectrode with an added P-C3N4 layer and the NiBi / P-C3N4 / BiVO4 composite photoelectrode with added P-C3N4 and NiBi layers showed improved photocurrent. At 1.23V (vs. RHE), the P-C3N4 / BiVO4 composite photoelectrode showed a 1.2-fold increase in photocurrent compared to the BiVO4 photoelectrode, while the NiBi / P-C3N4 / BiVO4 composite photoelectrode showed a 3.6-fold increase in photocurrent compared to the BiVO4 photoelectrode.

[0067] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate, characterized in that, It includes a conductive substrate and a BiVO4 layer, a P-C3N4 layer and a nickel borate layer sequentially loaded on the conductive substrate; The P-C3N4 layer is composed of P-C3N4 nanosheets; the nickel borate layer is attached to the P-C3N4 layer and the BiVO4 layer.

2. A method for preparing a phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate as described in claim 1, characterized in that, Includes the following steps: (1) BiVO4 is deposited on a conductive substrate to form a BiVO4 layer, thereby obtaining a BiVO4 photoelectrode; (2) Melamine and tetrabutylammonium hexafluorophosphate are dissolved in ethanol, heated and calcined to obtain powder; the powder is mixed with ethanol to obtain a spraying liquid; the spraying liquid is deposited on the BiVO4 photoelectrode obtained in step (1) to form a P-C3N4 layer, and a P-C3N4 / BiVO4 composite photoelectrode is obtained. (3) Mix potassium borate buffer solution and nickel sulfate hexahydrate to obtain precursor liquid A; deposit the precursor liquid A on the P-C3N4 / BiVO4 composite photoelectrode obtained in step (2) to form a nickel borate layer, and obtain the phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate.

3. The method for preparing a phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate according to claim 2, characterized in that, Step (1) specifically involves: A. Mix nitric acid solution, potassium iodide and bismuth nitrate pentahydrate to obtain solution A; dissolve p-benzoquinone in ethanol and sonicate to obtain solution B; mix solution A and solution B to obtain precursor liquid B; deposit precursor liquid B on a conductive substrate to form a BiOI film, thus obtaining a conductive substrate with a BiOI film deposited on its surface. B. Mix acetylacetonate vanadyl and dimethyl sulfoxide to obtain solution C; The solution C is dropped onto the conductive substrate on which the surface-deposited BiOI film is obtained in step A. After annealing, alkali washing, water washing and drying, a BiVO4 layer is formed, and a BiVO4 photoelectrode is obtained.

4. The method for preparing the phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode supported on nickel borate according to claim 3, characterized in that, In step A, the ratio of the nitric acid solution, potassium iodide, and bismuth nitrate pentahydrate is 25 mL : 0.4 mol : 0.04 mol; the pH of the nitric acid solution is 1.6–1.8; and / or, The ratio of p-benzoquinone to ethanol is 0.23 mol: 10 mL; and / or, The process conditions for the deposition precursor fluid B are as follows: initial voltage -0.1V, sampling interval 0.1s, deposition time 150–200s, settling time 0s, and sensitivity 1×10⁻⁶. -3 A.

5. The method for preparing the phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode supported on nickel borate according to claim 3, characterized in that, In step B, the ratio of acetylacetone vanadium oxide to dimethyl sulfoxide is 0.2 mol: 1 mL; and / or, The dripping volume is 25 μL / cm. 2 ; and / or, The annealing process is carried out at a temperature of 430–480°C for 2 hours.

6. The method for preparing a phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate according to claim 2, characterized in that, In step (2), the mass ratio of melamine to tetrabutylammonium hexafluorophosphate is 10:1; and / or, The calcination temperature is 240–260°C, and the time is 3 hours.

7. The method for preparing a phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate according to claim 2, characterized in that, In step (2), the mass ratio of the powder to the volume ratio of ethanol is 1:1 (mg:mL).

8. The method for preparing a phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate according to claim 2, characterized in that, In step (2), the deposition spraying liquid is applied by spraying; the process conditions for the deposition spraying liquid are: heating plate temperature of 200℃, and the amount of spraying liquid used is 0.5~1mL / cm. 2 The static time is 0 seconds.

9. The method for preparing a phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate according to claim 2, characterized in that, In step (3), the ratio of potassium borate buffer solution to nickel sulfate hexahydrate is 0.5 mol: 1 mmol; the pH value of potassium borate buffer solution is 9.

5.

10. The method for preparing a phosphorus-doped carbon nitride composite bismuth vanadate photoelectrode loaded with nickel borate according to claim 2, characterized in that, In step (3), the deposition precursor fluid A is deposited via electrochemical deposition; the deposition conditions for the deposition precursor fluid A are: deposition temperature at room temperature, potential at 0V, running time at 10s, sampling interval at 0.1s, settling time at 2s, and sensitivity at 1×10⁻⁶. -3 A, the light intensity is 100 mW·cm -2 .

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