Preparation Method of Benzoic Acid Complex Composite Bismuth Vanadate and Its Application in Photoelectrochemical Water Splitting

Abstract

The present invention belongs to the technical field of composite materials, relates to composite electrode materials, and particularly relates to a preparation method of benzoic acid complex composite bismuth vanadate. The method includes using N,N-dimethylformamide as a solvent, adding ligand benzoic acid to prepare a solution with a concentration of 0.01 - 0.1 M, respectively adding metal ligand ion precursors with the same molar number as BEN, and stirring evenly to prepare a precursor solution; placing the FTO sheet loaded with BiVO4 with the conductive surface facing down into a stainless steel autoclave with a polytetrafluoroethylene liner, adding the precursor solution, carrying out a solvothermal reaction at 100 - 140 °C for 5 - 15 h, taking it out after cooling to room temperature, washing with ethanol and drying to obtain the product. The present invention also applies the prepared composite to photoelectrochemical water splitting for hydrogen production. The metal benzoic acid complex M-BEN-MOC is compounded on the surface of worm-like BiVO4, effectively enhancing the carrier migration rate of the optoelectronic material, improving the electron-hole separation efficiency and the photoelectrocatalytic performance. The prepared binary metal iron-nickel benzoic acid complex BiVO4 / FeNi-BEN-MOC catalyst has good application prospects in the fields of environment, energy, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, relates to composite electrode materials, and particularly relates to a preparation method of a benzoic acid complex composite bismuth vanadate (BiVO 4 / M-BEN-MOC) and its application in photoelectrochemical water splitting. Background Art

[0002] In recent years, converting solar energy with huge energy into stable and easily storable hydrogen energy through photoelectrocatalysis (PEC) water splitting has caused a research boom. In this energy conversion process of solar energy - chemical energy, selecting a suitable semiconductor is the key. Among them, bismuth vanadate (BiVO 4 ) has become an outstanding one among many semiconductor materials due to its low cost, visible light response, large photocurrent density, etc. The suitable bandgap width (~2.4 eV) of BiVO 4 enables it to absorb sunlight in a wide range and also enables better separation of photogenerated carriers. The theoretical photocurrent density can reach 7.5 mA·cm -2 , but in actual applications, the photocurrent density is difficult to reach the theoretical value, mainly because the BiVO 4 semiconductor material has problems such as slow water oxidation kinetics and high recombination rate of photogenerated electron pairs.

[0003] Modification with an oxygen evolution cocatalyst (OEC) is an effective modification method. Metal-organic complexes (hereinafter abbreviated as MOC), such as metal-organic frameworks (MOF), have been widely studied as an effective OEC because they can provide catalytic active sites with adjustable electronic structures. Polyfunctional ligands such as terephthalic acid (PTA) and benzene-1,3,5-tricarboxylic acid (BTC) are commonly used MOF organic ligands. However, there are few reports on MOC synthesized with monofunctional organic ligands as cocatalysts. At the same time, considering the strong oxidizing property of high-valent metals and the low cost of non-noble metals, Fe, Co, and Ni are more concerned as coordination ions in the synthesis of MOF materials. It is reported that Ni and Co are more likely to replace hydrogen atoms in ligands, and the combination of Fe and Ni can increase the valence state of Ni, which is beneficial to the progress of oxidation reactions.

[0004] The present invention uses electrochemically deposited BiVO 4 as a substrate, and further through a hydrothermal method, selects monofunctional benzoic acid (BEN) as an organic ligand to synthesize BiVO 4 / M-BEN-MOC composite thin film materials modified with unit and binary metal benzoic acid complexes M(Fe, Ni)-BEN-MOC. It is found that under an applied voltage of 1.23 V vs. RHE, the photocurrent density of the binary metal (iron-nickel) benzoic acid complex BiVO 4 / FeNi-BEN-MOC composite electrode is that of the bare BiVO4 5.6 times that of the electrode, and exhibits more excellent photoelectrocatalytic performance than composite electrodes modified with other polycarboxylic acid ligand complexes. In addition, the binary metal iron-nickel metal benzoate complex has a higher performance improvement effect compared with the unit iron or nickel metal benzoate complex, and the binary metal coordination active centers synergistically catalyze, effectively improving the surface reaction kinetics of water oxidation. Summary of the Invention

[0005] To solve the problems of slow water oxidation kinetics and high recombination rate of photogenerated electron pairs in BiVO 4 semiconductor materials, the present invention discloses a preparation method of benzoic acid complex composite bismuth vanadate (BiVO 4 / M-BEN-MOC).

[0006] Technical Solution

[0007] Using bismuth nitrate, potassium iodide, p-benzoquinone, ethanol, and FTO conductive glass as raw materials, first grow BiVO on the surface of FTO by electrodeposition and calcination treatment 4 , and then use benzoic acid (BEN), iron(III) nitrate nonahydrate, nickel(II) chloride hexahydrate, and N,N-dimethylformamide (DMF) as raw materials to synthesize BiVO 4 / M-BEN-MOC composite photoanode by solvothermal method.

[0008] A preparation method of benzoic acid complex composite bismuth vanadate (BiVO 4 / M-BEN-MOC) includes the following steps:

[0009] A. Preparation of BiVO 4 / M-BEN-MOC precursor solution: Using N,N-dimethylformamide (DMF) as a solvent, add the ligand benzoic acid (BEN) to form a 0.01-0.1 M solution, and add metal ligand ion precursor substances with the same molar number as BEN, stir evenly to prepare the precursor solution, where the metal ligand ion precursor substances are Fe(NO 3 ) 3 ·9H 2 O, NiCl 2 ·6H 2 O, or a binary precursor of Fe(NO 3 ) 3 ·9H 2 O and NiCl 2 ·6H 2 O in any molar ratio;

[0010] B. Preparation of BiVO 4 / M-BEN-MOC: Load BiVO 4The FTO wafer with the conductive side facing down is placed into a stainless-steel high-pressure reactor lined with polytetrafluoroethylene. The above-mentioned precursor solution is added, and a solvothermal reaction is carried out at 100 - 140 °C for 5 - 15 h. After cooling to room temperature, it is taken out, washed with ethanol, and dried to obtain the product.

[0011] In a preferred disclosure example of the present invention, in step A, N,N-dimethylformamide (DMF) is used as the solvent, and the ligand benzoic acid (BEN) is added to prepare a 0.04 M solution.

[0012] In a preferred disclosure example of the present invention, in step A, the added molar ratio of Fe(NO 3 ) 3 ·9H 2 O and NiCl 2 ·6H 2 O is a binary precursor.

[0013] In a preferred disclosure example of the present invention, in step B, the FTO wafer loaded with BiVO 4 is placed into a stainless-steel high-pressure reactor lined with polytetrafluoroethylene with the conductive side facing down, and the above-mentioned precursor solution is added, and the reaction is carried out at 120 °C for 10 h.

[0014] The FTO wafer loaded with BiVO 4 in the present invention, the preparation method thereof is detailed in CN110408951A.

[0015] According to the method disclosed in the present invention, the prepared BiVO 4 / M-BEN-MOC are respectively BiVO 4 / Fe-BEN-MOC, BiVO 4 / Ni-BEN-MOC and BiVO 4 / FeNi-BEN-MOC; among them, the worm-like BiVO 4 has a uniform and regular morphology, and the growth height is about 0.72 μm. The morphology of the BiVO 4 / M-BEN-MOC composite photoanode material modified with the M-BEN-MOC thin layer hardly changes.

[0016] Another object of the present invention is to disclose the photocatalysis of the prepared BiVO 4 / M-BEN-MOC composite electrode in the application of photoelectrochemical water splitting.

[0017] Photoelectrocatalytic water splitting experiment

[0018] (1) Prepare 50 mL of a solution with a concentration of 0.5 mol·L -1 of Na 2 SO 4 solution, place it in the dark, and introduce N 2Last for 30 min;

[0019] (2) Take BiVO 4 / M-BEN-MOC sample as the working electrode, place it in the photoelectrocatalytic device, add the prepared Na 2 SO 4 solution, turn on the light source, and conduct the photoelectrocatalytic water splitting experiment.

[0020] Features of the present invention:

[0021] (1) Introduce monofunctional benzoic acid as the ligand to form unit and binary metal benzoic acid complexes BiVO 4 / M-BEN-MOC composite photoanode effectively promotes carrier migration and inhibits electron-hole pair recombination;

[0022] (2) Introduce a binary metal coordination center to form an iron-nickel binary metal benzoic acid complex BiVO 4 / FeNi-BEN-MOC composite photoanode accelerates the interfacial reaction kinetics.

[0023] The BiVO 4 / FeNi-BEN-MOC composite photoanode prepared in the present invention uses instruments such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) to analyze the morphology, structure, and composition of the product, measures the absorbance through a UV-Vis spectrophotometer, and measures the photocurrent density curve (J-V) with a standard three-electrode electrochemical workstation, etc., to evaluate its photoelectrocatalytic activity.

[0024] All the reactant reagents used in the present invention are commercially available.

[0025] Beneficial effects

[0026] The present invention synthesizes the BiVO 4 / M-BEN-MOC composite photoanode material through a very simple electrodeposition method, calcination post-treatment, and hydrothermal method. The metal benzoic acid complex M-BEN-MOC is compounded on the surface of worm-like BiVO 4 , effectively enhancing the carrier migration rate of the optoelectronic material, improving the electron-hole separation efficiency, and improving the photoelectrocatalytic performance of the material. The prepared binary metal iron-nickel benzoic acid complex BiVO 4 / FeNi-BEN-MOC catalyst has good application prospects in the fields of environment, energy, etc. Description of the drawings

[0027] Figure 1 . The BiVO prepared in Example 1 4XRD spectrum of BiVO / FeNi-BEN-MOC composite photoanode;

[0028] Figure 2 . BiVO prepared in Example 1 4 XPS spectrum of BiVO / FeNi-BEN-MOC composite photoanode;

[0029] Figure 3 . BiVO prepared in Example 1 4 SEM images of BiVO / FeNi-BEN-MOC composite photoanode;

[0030] Figure 4 . BiVO prepared in Example 1 4 UV-vis spectrum of BiVO / FeNi-BEN-MOC composite photoanode;

[0031] Figure 5 . J-V curves of BiVO / M-BEN-MOC composite photoanodes prepared in Examples 1, 3, and 7 4 ;

[0032] Figure 6 . BiVO prepared in Example 1 4 J-V curves of BiVO / FeNi-MOCs composite photoanode;

[0033] Figure 7 . BiVO prepared in Example 1 4 Photoelectrochemical impedance spectroscopy (PEIS) diagrams of BiVO / FeNi-MOCs composite photoanode. Detailed implementation manners

[0034] The present invention will be described in detail below in conjunction with embodiments, so that those skilled in the art can better understand the present invention. However, the present invention is not limited to the following embodiments.

[0035] In the following embodiments, the FTO sheet loaded with BiVO 4 The preparation method is detailed in CN110408951A.

[0036] Example 1

[0037] A preparation method of BiVO 4 / FeNi-BEN-MOC, comprising the following steps:

[0038] A. Preparation of BiVO 4 / FeNi-BEN-MOC precursor solution: Using 40 mL of N,N-dimethylformamide (DMF) as the solvent, adding 195.4 mg of ligand BEN to the solvent to form solution A with a concentration of 0.04 M, and then adding 484.8 mg of Fe(NO 3 )3 ·9H 2 O and 190.2 mg NiCl 2 ·6H 2 O, and stir evenly to prepare precursor solution B.

[0039] B, BiVO 4 Preparation of / FeNi-BEN-MOC: Place the prepared FTO with worm-like BiVO 4 grown (conductive side down) into a stainless steel autoclave with a PTFE liner, add the prepared precursor solution, tighten it, and place it in a forced-air drying oven at 120 °C for reaction for 10 h. After cooling to room temperature, take it out, wash it with ethanol and dry it to obtain a yellow-green sample product.

[0040] Photoelectrocatalytic water splitting experiment

[0041] (1) Prepare 50 mL of a solution with a concentration of 0.5 mol·L -1 of Na 2 SO 4 solution, place it in the dark, and pass N 2 continuously for 30 minutes;

[0042] (2) Take the BiVO 4 / FeNi-BEN-MOC sample as the working electrode, place it in a photoelectrocatalytic device, add the prepared Na 2 SO 4 solution, turn on the light source, and conduct a photoelectrocatalytic water splitting experiment.

[0043] BiVO 4 The maximum photocurrent density of the / FeNi-BEN-MOC composite photoanode tested by linear sweep voltammetry (LSV) is 3.7 mA / cm 2 (1.23 V vs RHE).

[0044] Example 2

[0045] A preparation method of BiVO 4 / Fe-BEN-MOC, comprising the following steps:

[0046] A, Preparation of BiVO 4 / Fe-BEN-MOC precursor solution: Using 40 mL of N,N-dimethylformamide DMF as the solvent, add 48.8 mg of ligand BEN to the solvent to prepare solution A with a concentration of 0.01 M. Then add 808 mg of Fe(NO 3 ) 3 ·9H 2 O, and stir evenly to prepare precursor solution B.

[0047] B, BiVO4 Preparation of BiVO / Fe-BEN-MOC: Place the prepared FTO (conductive side down) with worm-like BiVO grown on it into a stainless-steel autoclave with a PTFE liner, add the prepared precursor solution, tighten it, and place it in a forced-air drying oven at 120 °C for reaction for 10 h. After cooling to room temperature, take it out, wash it with ethanol and dry it to obtain a yellow-green sample product. 4 Photoelectrocatalytic water splitting experiment

[0048] Photoelectrocatalytic water splitting experiment

[0049] (1) Prepare 50 mL of a solution with a concentration of 0.5 mol·L -1 of Na 2 SO 4 solution, place it in the dark, and introduce N 2 continuously for 30 minutes;

[0050] (2) Take the BiVO 4 / Fe-BEN-MOC sample as the working electrode, place it in a photoelectrocatalytic device, add the prepared Na 2 SO 4 solution, turn on the light source, and conduct a photoelectrocatalytic water splitting experiment.

[0051] The maximum photocurrent density of the linear sweep voltammetry (LSV) test of the BiVO 4 / Fe-BEN-MOC composite photoanode is 2.0 mA / cm 2 (1.23 V vs RHE).

[0052] Example 3

[0053] A preparation method of BiVO 4 / Fe-BEN-MOC, comprising the following steps:

[0054] A. Preparation of the BiVO 4 / Fe-BEN-MOC precursor solution: Using 40 mL of N,N-dimethylformamide (DMF) as the solvent, add 195.4 mg of ligand BEN to the solvent to form solution A with a concentration of 0.04 M. Then add 808 mg of Fe(NO 3 ) 3 ·9H 2 O, stir evenly to prepare the precursor solution B.

[0055] B. Preparation of BiVO 4 / Fe-BEN-MOC: Place the prepared FTO with worm-like BiVO grown on it into a stainless-steel autoclave with a PTFE liner, add the prepared precursor solution, tighten it, and place it in a forced-air drying oven at 120 °C for reaction for 10 h. After cooling to room temperature, take it out, wash it with ethanol and dry it to obtain a yellow-green sample product. 4Put the FTO (conductive side down) into a stainless-steel autoclave with a PTFE liner, add the prepared precursor solution, tighten it, and place it in a blast drying oven at 120 °C for 10 h. After cooling to room temperature, take it out, wash it with ethanol and dry it to obtain a yellow-green sample product.

[0056] Photoelectrocatalytic water splitting experiment

[0057] (1) Prepare 50 mL of a solution with a concentration of 0.5 mol·L -1 of Na 2 SO 4 solution, place it in the dark, and pass in N 2 for 30 minutes continuously;

[0058] (2) Take the BiVO 4 / Fe-BEN-MOC sample as the working electrode, place it in the photoelectrocatalytic device, add the prepared Na 2 SO 4 solution, turn on the light source, and conduct the photoelectrocatalytic water splitting experiment.

[0059] BiVO 4 / Fe-BEN-MOC composite photoanode has a maximum photocurrent density of 3.2 mA / cm 2 (1.23 V vs RHE).

[0060] Example 4

[0061] A preparation method of BiVO 4 / Fe-BEN-MOC includes the following steps:

[0062] A. Preparation of the BiVO 4 / Fe-BEN-MOC precursor solution: Using 40 mL of N,N-dimethylformamide DMF as the solvent, add 488 mg of the ligand BEN to the solvent to form solution A with a concentration of 0.1 M. Then add 808 mg of Fe(NO 3 ) 3 ·9H 2 O, stir evenly to prepare the precursor solution B.

[0063] B. Preparation of BiVO 4 / Fe-BEN-MOC: Put the prepared FTO (conductive side down) for growing worm-like BiVO 4 into a stainless-steel autoclave with a PTFE liner, add the prepared precursor solution, tighten it, and place it in a blast drying oven at 120 °C for 10 h. After cooling to room temperature, take it out, wash it with ethanol and dry it to obtain a yellow-green sample product.

[0064] Photoelectrocatalytic water splitting experiment

[0065] (1) Prepare 50 mL of a solution with a concentration of 0.5 mol·L -1 of Na 2 SO 4 solution, place it in the dark, and introduce N 2 for 30 minutes continuously;

[0066] (2) Take the BiVO 4 / Fe-BEN-MOC sample as the working electrode, place it in the photoelectrocatalytic device, add the prepared Na 2 SO 4 solution, turn on the light source, and conduct the photoelectrocatalytic water splitting experiment.

[0067] The maximum photocurrent density of the linear sweep voltammetry (LSV) test of the BiVO 4 / Fe-BEN-MOC composite photoanode is 2.1 mA / cm 2 (1.23 V vs RHE).

[0068] Example 5

[0069] A preparation method of BiVO 4 / Fe-BEN-MOC includes the following steps:

[0070] A. Preparation of the BiVO 4 / Fe-BEN-MOC precursor solution: Using 40 mL of N,N-dimethylformamide DMF as the solvent, add 195.4 mg of the ligand BEN to the solvent to prepare solution A with a concentration of 0.04 M. Then add 808 mg of Fe(NO 3 ) 3 ·9H 2 O, stir evenly to prepare the precursor solution B.

[0071] B. Preparation of BiVO 4 / Fe-BEN-MOC: Place the prepared FTO (conductive side down) for growing worm-like BiVO 4 into a stainless steel autoclave with a polytetrafluoroethylene liner, add the prepared precursor solution, tighten it, and place it in a blast drying oven at 100 °C for reaction for 10 h. After cooling to room temperature, take it out, wash it with ethanol and dry it to obtain a yellow-green sample product.

[0072] Photoelectrocatalytic water splitting experiment

[0073] (1) Prepare 50 mL of a solution with a concentration of 0.5 mol·L -1 of Na 2 SO 4 solution, place it in the dark, and introduce N 2 for 30 minutes continuously;

[0074] (2) Take BiVO 4 / Fe-BEN-MOC sample as the working electrode, place it in the photoelectrocatalytic device, add the prepared Na 2 SO 4 solution, turn on the light source, and conduct the photoelectrocatalytic water splitting experiment.

[0075] BiVO 4 The maximum photocurrent density of the linear sweep voltammetry (LSV) test of the / Fe-BEN-MOC composite photoanode is 2.5 mA / cm 2 (1.23 V vs RHE).

[0076] Example 6

[0077] A preparation method of BiVO 4 / Fe-BEN-MOC, comprising the following steps:

[0078] A. Preparation of BiVO 4 / Fe-BEN-MOC precursor solution: Using 40 mL of N,N-dimethylformamide DMF as the solvent, add 195.4 mg of ligand BEN to the solvent to form solution A with a concentration of 0.04 M. Then add 808 mg of Fe(NO 3 ) 3 ·9H 2 O, stir evenly to prepare the precursor solution B.

[0079] B. Preparation of BiVO 4 / Fe-BEN-MOC: Place the prepared FTO (conductive side down) for growing worm-like BiVO 4 into a stainless steel autoclave with a polytetrafluoroethylene liner, add the prepared precursor solution, tighten it, and place it in a blast drying oven at 140 °C for reaction for 10 h. After cooling to room temperature, take it out, wash it with ethanol and dry it to obtain a yellow-green sample product.

[0080] Photoelectrocatalytic water splitting experiment

[0081] (1) Prepare 50 mL of a solution with a concentration of 0.5 mol·L -1 of Na 2 SO 4 solution in the dark and introduce N 2 for 30 minutes continuously;

[0082] (2) Take BiVO 4 / Fe-BEN-MOC sample as the working electrode, place it in the photoelectrocatalytic device, add the prepared Na 2 SO 4Solution, turn on the light source, and conduct the photoelectrocatalytic water splitting experiment.

[0083] BiVO 4 The maximum photocurrent density measured by linear sweep voltammetry (LSV) of the BiVO 2 (1.23 V vs RHE).

[0084] Example 7

[0085] A method for preparing BiVO 4 / Ni-BEN-MOC, comprising the following steps:

[0086] A. Preparation of the BiVO 4 / Ni-BEN-MOC precursor solution: Using 40 mL of N,N-dimethylformamide (DMF) as the solvent, add 195.4 mg of the ligand BEN to the solvent to form solution A with a concentration of 0.04 M. Then add 475.4 mg of NiCl 2 ·6H 2 O, and stir evenly to prepare the precursor solution B.

[0087] B. Preparation of BiVO 4 / Ni-BEN-MOC: Place the prepared FTO (conductive side down) with worm-like BiVO 4 into a stainless-steel autoclave with a PTFE liner, add the prepared precursor solution, tighten it, and place it in a blast drying oven at 120 °C for reaction for 10 h. After cooling to room temperature, take it out, wash it with ethanol and dry it to obtain a yellow-green sample product.

[0088] Photoelectrocatalytic water splitting experiment

[0089] (1) Prepare 50 mL of a solution with a concentration of 0.5 mol·L -1 of Na 2 SO 4 and place it in the dark, and introduce N 2 for 30 minutes continuously;

[0090] (2) Take the BiVO 4 / Ni-BEN-MOC sample as the working electrode, place it in the photoelectrocatalytic device, add the prepared Na 2 SO 4 solution, turn on the light source, and conduct the photoelectrocatalytic water splitting experiment.

[0091] BiVO 4 The maximum photocurrent density measured by linear sweep voltammetry (LSV) of the BiVO 2(1.23V vs RHE).

[0092] Example 8

[0093] A method for preparing BiVO 4 / FeNi-BEN-MOC, comprising the following steps:

[0094] A. Preparation of the BiVO 4 / FeNi-BEN-MOC precursor solution: Using 40 mL of N,N-dimethylformamide (DMF) as the solvent, add 195.4 mg of ligand BEN to the solvent to form solution A with a concentration of 0.04 M. Then add 404 mg of Fe(NO 3 ) 3 ·9H 2 O and 237.7 mg of NiCl 2 ·6H 2 O, and stir evenly to prepare precursor solution B.

[0095] B. Preparation of BiVO 4 / FeNi-BEN-MOC: Place the prepared FTO (conductive side down) for growing worm-like BiVO 4 into a stainless steel autoclave with a polytetrafluoroethylene liner, add the prepared precursor solution, tighten it, and place it in a forced-air drying oven at 120 °C for reaction for 5 h. After cooling to room temperature, take it out, wash it with ethanol and dry it to obtain a yellow-green sample product.

[0096] Photoelectrocatalytic water splitting experiment

[0097] (1) Prepare 50 mL of a solution with a concentration of 0.5 mol·L -1 of Na 2 SO 4 solution, place it in the dark, and pass N 2 continuously for 30 minutes;

[0098] (2) Take the BiVO 4 / FeNi-BEN-MOC sample as the working electrode, place it in a photoelectrocatalytic device, add the prepared Na 2 SO 4 solution, turn on the light source, and conduct a photoelectrocatalytic water splitting experiment.

[0099] The maximum photocurrent density of the linear sweep voltammetry (LSV) test of the BiVO 4 / FeNi-BEN-MOC composite photoanode is 2.7 mA / cm 2 (1.23V vs RHE).

[0100] Example 9

[0101] A preparation method of BiVO 4 / FeNi-BEN-MOC, comprising the following steps:

[0102] A. Preparation of BiVO 4 / FeNi-BEN-MOC precursor solution: Using 40 mL of N,N-dimethylformamide (DMF) as the solvent, add 195.4 mg of ligand BEN to the solvent to prepare solution A with a concentration of 0.04 M. Then add 404 mg of Fe(NO 3 ) 3 ·9H 2 O and 237.7 mg of NiCl 2 ·6H 2 O, and stir evenly to prepare precursor solution B.

[0103] B. Preparation of BiVO 4 / FeNi-BEN-MOC: Place the prepared FTO (conductive side down) for growing worm-like BiVO 4 into a stainless steel autoclave with a polytetrafluoroethylene liner, add the prepared precursor solution, tighten it, and place it in a 120 °C blast drying oven to react for 10 h. After cooling to room temperature, take it out, wash it with ethanol and dry it to obtain a yellow-green sample product.

[0104] Photocatalytic water splitting experiment

[0105] (1) Prepare 50 mL of a solution with a concentration of 0.5 mol·L -1 of Na 2 SO 4 solution, place it in the dark, and pass N 2 continuously for 30 minutes;

[0106] (2) Take the BiVO 4 / FeNi-BEN-MOC sample as the working electrode, place it in a photocatalytic device, add the prepared Na 2 SO 4 solution, turn on the light source, and conduct a photocatalytic water splitting experiment.

[0107] The maximum photocurrent density of the linear sweep voltammetry (LSV) test of the BiVO 4 / FeNi-BEN-MOC composite photoanode is 3.3 mA / cm 2 (1.23 V vs RHE).

[0108] Example 10

[0109] A preparation method of BiVO 4 / FeNi-BEN-MOC, comprising the following steps:

[0110] A. Preparation of BiVO 4 / FeNi - BEN - MOC precursor solution: Using 40 mL of N,N - dimethylformamide (DMF) as the solvent, add 195.4 mg of ligand BEN to the solvent to form solution A with a concentration of 0.04 M. Then add 404 mg of Fe(NO 3 ) 3 ·9H 2 O and 237.7 mg of NiCl 2 ·6H 2 O, and stir evenly to prepare precursor solution B.

[0111] B. Preparation of BiVO 4 / FeNi - BEN - MOC: Place the prepared FTO (conductive side down) with worm - like BiVO 4 into a stainless - steel autoclave lined with polytetrafluoroethylene, add the prepared precursor solution, tighten it, and place it in a forced - air drying oven at 120 °C for 15 h. After cooling to room temperature, take it out, wash it with ethanol and dry it to obtain a yellow - green sample product.

[0112] Photocatalytic water splitting experiment

[0113] (1) Prepare 50 mL of a solution with a concentration of 0.5 mol·L -1 of Na 2 SO 4 and place it in the dark, and introduce N 2 continuously for 30 minutes;

[0114] (2) Take the BiVO 4 / FeNi - BEN - MOC sample as the working electrode, place it in the photocatalytic device, add the prepared Na 2 SO 4 solution, turn on the light source, and conduct the photocatalytic water splitting experiment.

[0115] The maximum photocurrent density of the linear sweep voltammetry (LSV) test of the BiVO 4 / FeNi - BEN - MOC composite photoanode is 2.9 mA / cm 2 (1.23 V vs RHE).

[0116] The above are only the embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the description of the present invention, or directly or indirectly applied in other related technical fields, shall be included in the patent protection scope of the present invention by the same token.

Claims

1. A preparation method of benzoic acid complex composite bismuth vanadate, characterized in that, it includes the following steps: A. Using N,N-dimethylformamide (DMF) as a solvent, ligand benzoic acid (BEN) was added to prepare a solution with a concentration of 0.01 - 0.1 M. Metal ligand ion precursors with the same molar amount as BEN were added respectively, and the mixture was stirred evenly to obtain a precursor solution. The metal ligand ion precursors were Fe(NO 3 ) 3 ·9H 2 O, NiCl 2 ·6H 2 O, or a binary precursor of Fe(NO 3 ) 3 · 9H 2 O and NiCl 2 · 6H 2 O with any molar ratio; B. Place the FTO sheet loaded with BiVO 4 with the conductive side facing down into a stainless-steel autoclave lined with polytetrafluoroethylene, add the above-mentioned precursor solution, carry out a solvothermal reaction at 100-140 °C for 5-15 h, take it out after cooling to room temperature, wash it with ethanol and dry it to obtain the product; Among them, the FTO sheet loaded with BiVO 4 is prepared by the following method: a. Mix the KI solution with the Bi(NO 3 ) 3 solution, adjust the pH to 1 - 2 with concentrated nitric acid to obtain Solution A, use the ethanol solution of p-benzoquinone as Solution B, and mix the two evenly to form a mixed solution, where the molar concentration ratio of the KI, Bi(NO 3 ) 3 to p-benzoquinone is 100:10:15 - 30, and the volume ratio of Solution A to Solution B is 5:1 - 3; b. Using the mixed solution as the electrolyte, applying a bias voltage of -0.1 V relative to Ag / AgCl, electro-depositing on the FTO substrate for 3 - 10 min, and then uniformly dropping a 0.2 M dimethyl sulfoxide (DMSO) solution of vanadyl acetylacetonate onto the surface of the FTO substrate; c. Place the FTO substrate in a muffle furnace and heat it at a heating rate of 2 °C / min to 300 - 450 °C for 2 - 5 h of constant temperature to obtain BiVO with a worm-like structure on the FTO substrate. 4 After cooling to room temperature, immerse it in 1 M NaOH solution to wash away the vanadium pentoxide produced after calcination.

2. The preparation method of benzoic acid complex composite bismuth vanadate according to claim 1, characterized in that: In step A, N,N-dimethylformamide is used as the solvent, and the ligand benzoic acid is added to form a 0.04 M solution.

3. The preparation method of benzoic acid complex composite bismuth vanadate according to claim 1, characterized in that: The addition of the binary precursor of Fe(NO 3 ) 3 ·9H 2 O and NiCl 2 ·6H 2 O with a molar ratio of 3:2 in Step A.

4. The preparation method of benzoic acid complex composite bismuth vanadate according to claim 1, characterized in that: In step B, the FTO sheet loaded with BiVO 4 is placed in a stainless-steel autoclave with a PTFE liner, with the conductive side facing down, and the above-mentioned precursor solution is added, and the reaction is carried out at 120 °C for 10 h.

5. Benzoic acid complex composite bismuth vanadate prepared by the method according to any one of claims 1 - 4.

6. The benzoic acid complex composite bismuth vanadate according to claim 5, characterized in that: Worm-like BiVO 4 has a uniform and regular morphology, and the BiVO 4 modified with M-BEN-MOC layer does not change its morphology.

7. An application of the benzoic acid complex composite bismuth vanadate according to claim 5, characterized in that: It is applied to photoelectrochemical water splitting.

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