A cobalt micron flower-bismuth vanadate nanophotoanode catalyst and its preparation method and application

Abstract

The present invention discloses a cobalt micron flower bismuth vanadate nanophotoanode catalyst and its preparation method and application. The preparation method includes: mixing N,N-dimethylformamide and anhydrous methanol to form a mixed solution; mixing the mixed solution, a chiral Schiff base carboxylic acid ligand, 4.4'-bipyridine and a cobalt chloride aqueous solution to obtain a precursor solution; wherein the chiral Schiff base carboxylic acid ligand has the structural formula of #imgabs0#. The BiVO4 / FTO photoelectrode conductive surface is placed face down in a polytetrafluoroethylene reactor, the precursor solution is injected, and after sealing with a hydrothermal reactor, the reaction is carried out at 60 to 110 ° C. After the reaction is completed, the cobalt micron flower bismuth vanadate nanophotoanode catalyst is obtained by cooling to room temperature. The preparation method of the present invention is simple in process, low in cost, and has good repeatability. The obtained product has uniform morphology and consistent size. As a catalyst, it exhibits excellent catalytic performance in the photoelectrocatalytic water oxidation reaction.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectrocatalytic materials, and in particular to a cobalt micron flower-bismuth vanadate nano photoanode catalyst and a preparation method and application thereof. Background Art

[0002] Photoelectrochemical water decomposition to produce hydrogen, that is, solar energy directly decomposes water to produce H2 under the catalytic action of semiconductor photoelectrodes, which can realize the conversion of solar energy to hydrogen energy in one step. This technology has the characteristics of mild reaction conditions, low cost and environmental friendliness, and is one of the most research-worthy and application-potential methods. However, the conversion efficiency of photoelectrochemical cells from solar energy to hydrogen energy is relatively low and cannot meet the minimum industrialization requirements. At present, BiVO4 has a suitable band gap. A sufficiently positive valence band edge (VB, ), becoming a hot research material in this field. However, BiVO4 photoanodes suffer from defects in photoelectrochemical water splitting, such as low electron mobility, severe electron-hole recombination, and slow surface water oxidation reactions. These defects hinder the conversion efficiency of solar energy to hydrogen energy and hinder its industrialization. Therefore, improving the photoelectric conversion efficiency of BiVO4 photoanodes has become a key research focus for anode catalysts in photoelectrochemical cells. Although some progress has been made in the modification of BiVO4 photoanodes, their photocurrent density and photostability still do not meet the requirements of industrialization. Therefore, research and development of BiVO4 composite photoanodes with higher photocurrent density and better stability are imperative. Studies have shown that adding a co-catalyst to the surface of a BiVO4 photoanode and reconstructing the interface to form an M-BiVO4 composite photoanode can not only improve the slow oxygen evolution reaction kinetics of the BiVO4 photoanode, but also enhance the stability of the BiVO4 photoanode. For example, the Chinese patent application publication number CN109876867A discloses a method for preparing a bimetallic-organic framework / bismuth vanadate composite photoanode material. The method uses CoCl2.6H2O and NiCl2.6H2O as raw materials, phthalic acid as a ligand skeleton, and a BiVO4 electrode as a matrix. In a mixed solution of N,N-dimethylformamide, anhydrous ethanol, and distilled water, a three-dimensional rhombohedral tetragonal metal skeleton NiCo-MOFs is formed by hydrothermal method and loaded on a BiVO4 film to obtain the photoanode material NiCo-MOFs / BiVO4. Due to the coupling effect of the bimetallic center, the electron transfer from the organic ligand to the metal center is promoted, promoting charge separation. Furthermore, the three-dimensional rhombic tetrahedral metal skeleton and sufficiently large contact area enable efficient light capture, reducing charge transfer resistance and accelerating carrier migration, thereby suppressing electron-hole pair recombination and significantly improving the electrochemical performance of BiVO4. However, the aforementioned patent requires doping with two metals, and the resulting material's catalytic water oxidation activity remains suboptimal. Therefore, finding suitable materials to construct M-BiVO4 composite systems is a key focus of BiVO4 photoanode modification research. Among various metals, Co, as one of the most catalytically active transition metal catalysts, has attracted considerable research attention. Its abundant reserves, low price, and industrial compatibility make the construction of Co-BiVO4 composite systems promising broad application potential. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a cobalt micron flower-bismuth vanadate nanophotoanode catalyst with uniform size and a preparation method thereof. The preparation method is simple in process, low in cost, and has good repeatability. The catalyst exhibits excellent catalytic performance for photoelectrocatalytic water oxidation.

[0004] The present invention solves the above technical problems through the following technical means:

[0005] A method for preparing a cobalt micron flower-bismuth vanadate nanophotoanode catalyst comprises the following steps:

[0006] S1. Evenly mix N,N-dimethylformamide and anhydrous methanol to form a mixed solution;

[0007] S2, uniformly mixing the mixed solution, the chiral Schiff base carboxylic acid ligand, 4,4'-bipyridine and the cobalt chloride aqueous solution to obtain a precursor solution; wherein the chiral Schiff base carboxylic acid ligand has the structural formula:

[0008] S3. Place the BiVO4 / FTO photoelectrode with the conductive surface facing downward in a polytetrafluoroethylene reactor, inject the precursor solution, seal it with a hydrothermal reactor, react at 60-110°C, and cool to room temperature after the reaction to obtain the cobalt micron flower-bismuth vanadate nanophotoanode catalyst.

[0009] Preferably, in S1, the volume ratio of N,N-dimethylformamide to anhydrous methanol is 1-2:8-9.

[0010] Preferably, the volume ratio of N,N-dimethylformamide to anhydrous methanol is 1.5:8.5.

[0011] Preferably, in S2, the mass ratio of the chiral Schiff base carboxylic acid ligand to 4,4'-bipyridine is 30-150:10-60.

[0012] Preferably, the mass ratio of the chiral Schiff base carboxylic acid ligand to 4,4'-bipyridine is 8.6:3.

[0013] Preferably, in S2, the mass volume ratio of the chiral Schiff base carboxylic acid ligand to the mixed solution is 34.4-103.2 mg:10 ml.

[0014] Preferably, in S2, the molar ratio of cobalt chloride to chiral Schiff base carboxylic acid ligand in the cobalt chloride aqueous solution is 2-1:1.

[0015] Preferably, in S3, the reaction time is 12-48 hours.

[0016] Preferably, in S3, the product cooled to room temperature is further washed and dried.

[0017] Preferably, the washing refers to washing with N,N-dimethylformamide and anhydrous methanol alternately in sequence, and the number of washing times is 3 to 5 times.

[0018] Preferably, the drying temperature is 60-80°C.

[0019] The present invention also provides a cobalt micron flower-bismuth vanadate nanometer photoanode catalyst, which is prepared by adopting the preparation method of the cobalt micron flower-bismuth vanadate nanometer photoanode catalyst.

[0020] The present invention also proposes an application of the cobalt micron flower-bismuth vanadate nanophotoanode catalyst as a photoelectrocatalyst for catalyzing water oxidation reaction.

[0021] The principle of the present invention is to adopt a hydrothermal method, use DMF, water and methanol as solvents, BiVO4 / FTO nanoarray as substrate, through chiral Schiff base carboxylic acid ligands, auxiliary ligand 4,4'-bipyridine, and metal salt Co 2 + The coordination was carried out and the co-polymers were directly grown in situ on the BiVO4 / FTO nano-substrate to form the coordination polymer cobalt micro-flowers. The obtained products had uniform size and morphology.

[0022] The advantages of the present invention are:

[0023] (1) The present invention adopts a hydrothermal method to prepare cobalt micron flower-bismuth vanadate nanophotoanode catalyst, which has simple process, low cost and good repeatability;

[0024] (2) The product prepared by the present invention has a micron flower-nano array structure and is of uniform size;

[0025] (3) The cobalt micron flower-bismuth vanadate nanophotoanode catalyst prepared by the present invention is used for photoelectrocatalytic water oxidation, showing a catalytic performance far higher than that of BiVO4. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a high-resolution scanning electron micrograph (SEM) of the cobalt microflower-bismuth vanadate nanophotoanode catalyst obtained in Example 1 of the present invention; Figures a, b, and c correspond to different magnifications, and Figure d is the mapping area.

[0027] Figure 2 This is a surface scanning element distribution map of the cobalt micron flower-bismuth vanadate nanophotoanode catalyst obtained in Example 1 of the present invention; wherein e~j are the element distribution maps of Bi, V, O, C, N, and Co respectively;

[0028] Figure 3 This is the X-ray photoelectron spectrum (XPS) of the cobalt micron flower-bismuth vanadate nanophotoanode catalyst obtained in Example 1 of the present invention, where a is the full spectrum element spectrum, b, c, and d are the peak fitting spectra of the O, C, and Co elements, respectively;

[0029] Figure 4The LSV curves (photocurrent (a) and dark current (b)) and IT curves (non-chopping (c) and chopping (d)) of the cobalt microflower-bismuth vanadate nanophotoanode catalyst obtained in Example 1 of the present invention in 0.5M Na2SO4 solution are shown, where the pure bismuth vanadate nanophotoanode catalyst is the standard catalyst;

[0030] Figure 5 This is a SEM image of the cobalt-bismuth vanadate nanophotoanode catalyst obtained in Comparative Example 1 of the present invention;

[0031] Figure 6 This is the LSV curve of the cobalt-bismuth vanadate nanophotoanode catalyst obtained in Comparative Example 1 of the present invention under light irradiation conditions;

[0032] Figure 7 This is an SEM image of the cobalt micron flower-bismuth vanadate nanophotoanode catalyst obtained in Comparative Example 2 of the present invention;

[0033] Figure 8 This is the LSV curve of the cobalt micron flower-bismuth vanadate nanophotoanode catalyst obtained in Comparative Example 2 of the present invention under light irradiation conditions;

[0034] Figure 9 This is the Fourier infrared characteristic spectrum of the cobalt micron flower-bismuth vanadate nanophotoanode catalyst obtained in Example 1;

[0035] Figure 10 This is a flow chart of the synthesis experiment of the cobalt microflower-bismuth vanadate nanophotoanode catalyst obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0037] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0038] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0039] The chiral Schiff base carboxylic acid ligand in the examples and comparative examples is a chiral ONO tridentate Schiff base carboxylic acid ligand disclosed in the Chinese patent application publication number CN113087640A, and its structural formula is

[0040] In the following examples and comparative examples, the BiVO4 / FTO photoelectrode is an existing material, and its preparation method includes the following steps: First, a three-electrode system is constructed by a Chenhua (CHI660E) electrochemical workstation, wherein FTO conductive glass (2cm×4cm) is a working electrode, a saturated Ag / AgCl electrode is a reference electrode, and a platinum sheet (1cm×1cm) is an auxiliary electrode. Then, the orange-red BiOI nanosheets are electro-deposited by a constant potential method, with a deposition potential of -0.1V and a deposition time of 3min. The orange-red BiOI nanosheets are then converted into a bright yellow BiVO4 nanophotoanode array by heat treatment to obtain a BiVO4 / FTO photoelectrode, such as Figure 10 The specific steps are shown in the following literature: Nanoporous BiVO4 Photoanodes with Dual-Layer Oxygen Evolution Catalysts for Solar Water Splitting, Tae Woo Kim and Kyoung-Shin Choi, Science, 343(6174), DOI: 10.1126 / science.1246913.

[0041] Example 1

[0042] Reference Figure 10 A method for preparing a cobalt micron flower-bismuth vanadate nanophotoanode catalyst comprises the following steps:

[0043] (1) Mix 1.5 mL of N,N-dimethylformamide solution and 8.5 mL of anhydrous methanol solution;

[0044] (2) adding 68.8 mg of chiral Schiff base carboxylic acid ligand and 24 mg of auxiliary ligand 4,4'-bipyridine to the uniform liquid obtained in step (1), stirring and ultrasonically mixing;

[0045] (3) Ultrasonic dissolution of pink cobalt chloride hexahydrate solid in deionized water to form a 0.1 M cobalt chloride aqueous solution, 3.2 mL of the cobalt chloride aqueous solution was added to the mixed solution obtained in step (2), ultrasonicated for 30 min, and then stirred for 30 min to obtain a precursor solution;

[0046] (4) The BiVO4 / FTO photoelectrode is placed with the conductive surface facing downward in a polytetrafluoroethylene reactor, and the precursor solution obtained in step (3) is slowly injected along the non-conductive surface of the BiVO4 / FTO photoelectrode. After being sealed with a stainless steel hydrothermal reactor, the reaction is carried out at a constant temperature of 60°C in an electric constant temperature forced air drying oven for 48 hours. After the constant temperature reaction time is over, the reactor is cooled to room temperature and the reactor is opened again. The obtained product is taken out and washed with N,N-dimethylformamide and methanol crosswise for 3 times, and then dried at 80°C to obtain a cobalt micron flower-bismuth vanadate nanophotoanode catalyst.

[0047] The high-resolution scanning electron microscope images, surface element distribution maps and X-ray photoelectron spectroscopy images of the cobalt micron flower-bismuth vanadate nanophotoanode catalyst prepared in this example are shown in Figure 2. Figure 1 、 Figure 2 and Figure 3 As shown. Figure 1 As can be seen from a to d, the product obtained in this embodiment has a micron flower-nano array structure with uniform size. Figure 2 e~j confirm the coexistence of Co, Bi, C, V, N, and O elements. Figure 3 a As can be seen, the full spectrum confirms the presence of Co, Ni, Bi, V and O elements, which matches well with the EDX element mapping results. Figure 3 b shows that the O1s of Co-Microflowers-BiVO4 nanophotoanode catalyst can be divided into three peaks: 530.93eV, 531.88eV and 532.83eV, which are attributed to lattice oxygen (O L ) and chemically adsorbed or dissociated oxygen species (O S ) and the hydroxyl oxygen (O H ). Figure 3 c shows that the C1s of the Co-Microflowers-BiVO4 photoanode can be divided into three peaks: 530.93 eV, 531.88 eV and 532.83 eV, which are attributed to O=CO, CN and CC bonds, respectively. Figure 3 d shows the Co 2p spectrum of the Co-Microflowers-BiVO4 photoanode. The fitted peaks at 797.08 eV and 781.38 eV are attributed to the Co 2p1 / 2 and Co 2p3 / 2 spin orbitals, respectively. In addition, two broad peaks at 803.38 eV and 786.38 eV are identified as satellites ("saturation") of Co 2p1 / 2 and Co 2p3 / 2, respectively. These results show the characteristic peaks of the Co(II) oxidation state.

[0048] The LSV curve (photocurrent and dark current) and IT curve (non-chopping and chopping) of the cobalt micron flower-bismuth vanadate nanophotoanode catalyst obtained in this example in 0.5M Na2SO4 solution are shown in FIG. Figure 4 The Co-Microflowers-BiVO4 curves in a to d are shown, where a is the photocurrent, b is the dark current, c is the non-chopping current, and d is the chopping current, with bismuth vanadate nanophotocatalyst as the standard catalyst (i.e., the BiVO4 / FTO photoelectrode). Figure 4 As can be seen from a to b, the cobalt micron flower-bismuth vanadate nanophotoanode catalyst prepared in this embodiment has a high photocatalytic activity at 1.23V. RHE The photocurrent density under bias voltage reached 4.38 mA cm -2 , and compared with pure bismuth vanadate (photocurrent density of 0.8 mA cm -2 ) significantly improves the photocurrent density, and the overpotential of the cobalt microflower-bismuth vanadate nanophotoanode catalyst under dark current is much lower than that of pure bismuth vanadate. Figure 4 c-d shows that the cobalt micron flower-bismuth vanadate nanophotoanode catalyst prepared in this embodiment is at 1.23V RHE There is no obvious decay of photocurrent density within 60 minutes under bias, and in the chopped light state, the visible light responsiveness of cobalt microflower-bismuth vanadate nanophotoanode catalyst is much better than that of pure bismuth vanadate. Figure 9 The Fourier infrared characteristic spectrum of the cobalt microflower-bismuth vanadate nanophotoanode catalyst obtained in this example shows that the infrared characteristic peaks of the Co-Microflowers-BiVO4 photoanode are significantly shifted compared with the infrared characteristic peaks of the chiral Schiff base carboxylic acid ligand, indicating that the Co 2+ It can coordinate with -OH and -C=N in chiral Schiff base carboxylic acid ligands.

[0049] Example 2

[0050] A method for preparing a cobalt micron flower-bismuth vanadate nanophotoanode catalyst comprises the following steps:

[0051] (1) Mix 1.5 mL of N,N-dimethylformamide solution and 8.5 mL of anhydrous methanol solution;

[0052] (2) adding 34.4 mg of chiral Schiff base carboxylic acid ligand and 12 mg of auxiliary ligand 4,4'-bipyridine to the homogeneous liquid obtained in step (1), stirring and ultrasonically mixing;

[0053] (3) Ultrasonic dissolution of pink cobalt chloride hexahydrate solid in deionized water to form a 0.1 M cobalt chloride aqueous solution, 1.6 mL of the cobalt chloride aqueous solution was added to the mixed solution obtained in step (2), ultrasonicated for 30 min, and then stirred for 30 min to obtain a precursor solution;

[0054] (4) The BiVO4 / FTO photoelectrode is placed with the conductive surface facing downward in a polytetrafluoroethylene reactor, and the precursor solution obtained in step (3) is slowly injected along the non-conductive surface of the BiVO4 / FTO photoelectrode. After being sealed with a stainless steel hydrothermal reactor, the reaction is carried out at a constant temperature of 60°C in an electric constant temperature forced air drying oven for 48 hours. After the constant temperature reaction time is over, the reactor is cooled to room temperature and the reactor is opened again. The obtained product is taken out and washed with N,N-dimethylformamide and methanol crosswise for 3 times, and then dried at 80°C to obtain a cobalt micron flower-bismuth vanadate nanophotoanode catalyst.

[0055] Characterization showed that the product obtained in this example had a micron flower-nano array structure with consistent size.

[0056] The same method as in Example 1 was used for testing. The cobalt micron flower-bismuth vanadate nanophotoanode catalyst prepared in this example was tested at 1.23V. RHE The photocurrent density under bias voltage reached 2.93 mA cm -2 , the photocurrent density has no obvious decay within 60 min.

[0057] Example 3

[0058] A method for preparing a cobalt micron flower-bismuth vanadate nanophotoanode catalyst comprises the following steps:

[0059] (1) Mix 1.5 mL of N,N-dimethylformamide solution and 8.5 mL of anhydrous methanol solution;

[0060] (2) adding 34.4 mg of chiral Schiff base carboxylic acid ligand and 12 mg of auxiliary ligand 4,4'-bipyridine to the homogeneous liquid obtained in step (1), stirring and ultrasonically mixing;

[0061] (3) Ultrasonic dissolution of pink cobalt chloride hexahydrate solid in deionized water to form a 0.1 M cobalt chloride aqueous solution, 0.8 mL of the cobalt chloride aqueous solution was added to the mixed solution obtained in step (2), ultrasonicated for 30 min, and then stirred for 30 min to obtain a precursor solution;

[0062] (4) The BiVO4 / FTO photoelectrode is placed with the conductive surface facing downward in a polytetrafluoroethylene reactor, and the precursor solution obtained in step (3) is slowly injected along the non-conductive surface of the BiVO4 / FTO photoelectrode. After being sealed with a stainless steel hydrothermal reactor, the reaction is carried out at a constant temperature of 60°C in an electric constant temperature forced air drying oven for 48 hours. After the constant temperature reaction time is over, the reactor is cooled to room temperature and the reactor is opened again. The obtained product is taken out and washed with N,N-dimethylformamide and methanol crosswise for 3 times, and then dried at 80°C to obtain a cobalt micron flower-bismuth vanadate nanophotoanode catalyst.

[0063] Characterization showed that the product obtained in this example had a micron flower-nano array structure with consistent size.

[0064] The same method as in Example 1 was used for testing. The cobalt micron flower-bismuth vanadate nanophotoanode catalyst prepared in this example was tested at 1.23V. RHE The photocurrent density under bias voltage reached 2.26 mA cm -2 , the photocurrent density has no obvious decay within 60 min.

[0065] Example 4

[0066] A method for preparing a cobalt micron flower-bismuth vanadate nanophotoanode catalyst comprises the following steps:

[0067] (1) Mix 1.5 mL of N,N-dimethylformamide solution and 8.5 mL of anhydrous methanol solution;

[0068] (2) adding 68.8 mg of chiral Schiff base carboxylic acid ligand and 24 mg of auxiliary ligand 4,4'-bipyridine to the uniform liquid obtained in step (1), stirring and ultrasonically mixing;

[0069] (3) Ultrasonic dissolution of pink cobalt chloride hexahydrate solid in deionized water to form a 0.1 M cobalt chloride aqueous solution, 2.4 mL of the cobalt chloride aqueous solution was added to the mixed solution obtained in step (2), ultrasonicated for 30 min, and then stirred for 30 min to obtain a precursor solution;

[0070] (4) The BiVO4 / FTO photoelectrode is placed with the conductive surface facing downward in a polytetrafluoroethylene reactor, and the precursor solution obtained in step (3) is slowly injected along the non-conductive surface of the BiVO4 / FTO photoelectrode. After being sealed with a stainless steel hydrothermal reactor, the reaction is carried out at a constant temperature of 60°C in an electric constant temperature forced air drying oven for 48 hours. After the constant temperature reaction time is over, the reactor is cooled to room temperature and the reactor is opened again. The obtained product is taken out and washed with N,N-dimethylformamide and methanol crosswise for 3 times, and then dried at 80°C to obtain a cobalt micron flower-bismuth vanadate nanophotoanode catalyst.

[0071] Characterization showed that the product obtained in this example had a micron flower-nano array structure with consistent size.

[0072] The same method as in Example 1 was used for testing. The cobalt micron flower-bismuth vanadate nanophotoanode catalyst prepared in this example was tested at 1.23V. RHE The photocurrent density under bias voltage reached 3.83 mA cm -2 , the photocurrent density has no obvious decay within 60 min.

[0073] Example 5

[0074] A method for preparing a cobalt micron flower-bismuth vanadate nanophotoanode catalyst comprises the following steps:

[0075] (1) Mix 1.5 mL of N,N-dimethylformamide solution and 8.5 mL of anhydrous methanol solution;

[0076] (2) adding 103.2 mg of chiral Schiff base carboxylic acid ligand and 36 mg of auxiliary ligand 4,4'-bipyridine to the homogeneous liquid obtained in step (1), stirring and ultrasonically mixing;

[0077] (3) Ultrasonic dissolution of pink cobalt chloride hexahydrate solid in deionized water to form a 0.1 M cobalt chloride aqueous solution, 4.8 mL of the cobalt chloride aqueous solution was added to the mixed solution obtained in step (2), ultrasonicated for 30 min, and then stirred for 30 min to obtain a precursor solution;

[0078] (4) The BiVO4 / FTO photoelectrode is placed with the conductive surface facing downward in a polytetrafluoroethylene reactor, and the precursor solution obtained in step (3) is slowly injected along the non-conductive surface of the BiVO4 / FTO photoelectrode. After being sealed with a stainless steel hydrothermal reactor, the reaction is carried out at a constant temperature of 60°C in an electric constant temperature forced air drying oven for 48 hours. After the constant temperature reaction time is over, the reactor is cooled to room temperature and the reactor is opened again. The obtained product is taken out and washed with N,N-dimethylformamide and methanol crosswise for 3 times, and then dried at 80°C to obtain a cobalt micron flower-bismuth vanadate nanophotoanode catalyst.

[0079] Characterization showed that the product obtained in this example had a micron flower-nano array structure with consistent size.

[0080] The same method as in Example 1 was used for testing. The cobalt micron flower-bismuth vanadate nanophotoanode catalyst prepared in this example was tested at 1.23V. RHE The photocurrent density under bias voltage reached 3.47 mA cm -2 , the photocurrent density has no obvious decay within 60 min.

[0081] Example 6

[0082] A method for preparing a cobalt micron flower-bismuth vanadate nanophotoanode catalyst comprises the following steps:

[0083] (1) Mix 1.5 mL of N,N-dimethylformamide solution and 8.5 mL of anhydrous methanol solution;

[0084] (2) adding 103.2 mg of chiral Schiff base carboxylic acid ligand and 36 mg of auxiliary ligand 4,4'-bipyridine to the homogeneous liquid obtained in step (1), stirring and ultrasonically mixing;

[0085] (3) Ultrasonic dissolution of pink cobalt chloride hexahydrate solid in deionized water to form a 0.1 M cobalt chloride aqueous solution, 4.0 mL of the cobalt chloride aqueous solution was added to the mixed solution obtained in step (2), ultrasonicated for 30 min, and then stirred for 30 min to obtain a precursor solution;

[0086] (4) The BiVO4 / FTO photoelectrode is placed with the conductive surface facing downward in a polytetrafluoroethylene reactor, and the precursor solution obtained in step (3) is slowly injected along the non-conductive surface of the BiVO4 / FTO photoelectrode. After being sealed with a stainless steel hydrothermal reactor, the reaction is carried out at a constant temperature of 60°C in an electric constant temperature forced air drying oven for 48 hours. After the constant temperature reaction time is over, the reactor is cooled to room temperature and the reactor is opened again. The obtained product is taken out and washed with N,N-dimethylformamide and methanol crosswise for 3 times, and then dried at 80°C to obtain a cobalt micron flower-bismuth vanadate nanophotoanode catalyst.

[0087] Characterization showed that the product obtained in this example had a micron flower-nano array structure with consistent size.

[0088] The same method as in Example 1 was used for testing. The cobalt micron flower-bismuth vanadate nanophotoanode catalyst prepared in this example was tested at 1.23V. RHE The photocurrent density under bias voltage reached 3.72 mA cm -2 , the photocurrent density has no obvious decay within 60 min.

[0089] Example 7

[0090] A method for preparing a cobalt micron flower-bismuth vanadate nanophotoanode catalyst comprises the following steps:

[0091] (1) Mix 1.5 mL of N,N-dimethylformamide solution and 8.5 mL of anhydrous methanol solution;

[0092] (2) adding 68.8 mg of chiral Schiff base carboxylic acid ligand and 24 mg of auxiliary ligand 4,4'-bipyridine to the uniform liquid obtained in step (1), stirring and ultrasonically mixing;

[0093] (3) Ultrasonic dissolution of pink cobalt chloride hexahydrate solid in deionized water to form a 0.1 M cobalt chloride aqueous solution, 3.2 mL of the cobalt chloride aqueous solution was added to the mixed solution obtained in step (2), ultrasonicated for 30 min, and then stirred for 30 min to obtain a precursor solution;

[0094] (4) The BiVO4 / FTO photoelectrode is placed with the conductive surface facing downward in a polytetrafluoroethylene reactor, and the precursor solution obtained in step (3) is slowly injected along the non-conductive surface of the BiVO4 / FTO photoelectrode. After being sealed with a stainless steel hydrothermal reactor, the reaction is carried out at a constant temperature of 60°C in an electric constant temperature forced air drying oven for 12 hours. After the constant temperature reaction time is over, the reactor is cooled to room temperature and the reactor is opened again. The obtained product is taken out and washed with N,N-dimethylformamide and methanol three times, and dried at 80°C to obtain a cobalt micron flower-bismuth vanadate nanophotoanode catalyst.

[0095] Characterization showed that the product obtained in this example had a micron flower-nano array structure with consistent size.

[0096] The same method as in Example 1 was used for testing. The cobalt micron flower-bismuth vanadate nanophotoanode catalyst prepared in this example was tested at 1.23V. RHE The photocurrent density under bias voltage reached 1.66 mA cm -2 , the photocurrent density has no obvious decay within 60 min.

[0097] Example 8

[0098] A method for preparing a cobalt micron flower-bismuth vanadate nanophotoanode catalyst comprises the following steps:

[0099] (1) Mix 1.5 mL of N,N-dimethylformamide solution and 8.5 mL of anhydrous methanol solution;

[0100] (2) adding 68.8 mg of chiral Schiff base carboxylic acid ligand and 24 mg of auxiliary ligand 4,4'-bipyridine to the uniform liquid obtained in step (1), stirring and ultrasonically mixing;

[0101] (3) Ultrasonic dissolution of pink cobalt chloride hexahydrate solid in deionized water to form a 0.1 M cobalt chloride aqueous solution, 3.2 mL of the cobalt chloride aqueous solution was added to the mixed solution obtained in step (2), ultrasonicated for 30 min, and then stirred for 30 min to obtain a precursor solution;

[0102] (4) The BiVO4 / FTO photoelectrode is placed with the conductive surface facing downward in a polytetrafluoroethylene reactor, and the precursor solution obtained in step (3) is slowly injected along the non-conductive surface of the BiVO4 / FTO photoelectrode. After being sealed with a stainless steel hydrothermal reactor, the reaction is carried out at a constant temperature of 60°C in an electric constant temperature forced air drying oven for 24 hours. After the constant temperature reaction time is over, the reactor is cooled to room temperature and the reactor is opened again. The obtained product is taken out and washed with N,N-dimethylformamide and methanol three times, and dried at 80°C to obtain a cobalt micron flower-bismuth vanadate nanophotoanode catalyst.

[0103] Characterization showed that the product obtained in this example had a micron flower-nano array structure with consistent size.

[0104] The same method as in Example 1 was used for testing. The cobalt micron flower-bismuth vanadate nanophotoanode catalyst prepared in this example was tested at 1.23V. RHE The photocurrent density under bias voltage reached 2.49 mA cm -2 , the photocurrent density has no obvious decay within 60 min.

[0105] Example 9

[0106] A method for preparing a cobalt micron flower-bismuth vanadate nanophotoanode catalyst comprises the following steps:

[0107] (1) Mix 1.5 mL of N,N-dimethylformamide solution and 8.5 mL of anhydrous methanol solution;

[0108] (2) adding 68.8 mg of chiral Schiff base carboxylic acid ligand and 24 mg of auxiliary ligand 4,4'-bipyridine to the uniform liquid obtained in step (1), stirring and ultrasonically mixing;

[0109] (3) Ultrasonic dissolution of pink cobalt chloride hexahydrate solid in deionized water to form a 0.1 M cobalt chloride aqueous solution, 3.2 mL of the cobalt chloride aqueous solution was added to the mixed solution obtained in step (2), ultrasonicated for 30 min, and then stirred for 30 min to obtain a precursor solution;

[0110] (4) The BiVO4 / FTO photoelectrode is placed with the conductive surface facing downward in a polytetrafluoroethylene reactor, and the precursor solution obtained in step (3) is slowly injected along the non-conductive surface of the BiVO4 / FTO photoelectrode. After being sealed with a stainless steel hydrothermal reactor, the reaction is carried out at a constant temperature of 80°C in an electric constant temperature forced air drying oven for 48 hours. After the constant temperature reaction time is over, the reactor is cooled to room temperature and the reactor is opened again. The obtained product is taken out and washed with N,N-dimethylformamide and methanol three times, and dried at 80°C to obtain a cobalt micron flower-bismuth vanadate nanophotoanode catalyst.

[0111] Characterization showed that the product obtained in this example had a micron flower-nano array structure with consistent size.

[0112] The same method as in Example 1 was used for testing. The cobalt micron flower-bismuth vanadate nanophotoanode catalyst prepared in this example was tested at 1.23V. RHE The photocurrent density under bias voltage reached 3.43 mA cm -2 , the photocurrent density has no obvious decay within 60 min.

[0113] Example 10

[0114] A method for preparing a cobalt micron flower-bismuth vanadate nanophotoanode catalyst comprises the following steps:

[0115] (1) Mix 1.5 mL of N,N-dimethylformamide solution and 8.5 mL of anhydrous methanol solution;

[0116] (2) adding 68.8 mg of chiral Schiff base carboxylic acid ligand and 24 mg of auxiliary ligand 4,4'-bipyridine to the uniform liquid obtained in step (1), stirring and ultrasonically mixing;

[0117] (3) Ultrasonic dissolution of pink cobalt chloride hexahydrate solid in deionized water to form a 0.1 M cobalt chloride aqueous solution, 3.2 mL of the cobalt chloride aqueous solution was added to the mixed solution obtained in step (2), ultrasonicated for 30 min, and then stirred for 30 min to obtain a precursor solution;

[0118] (4) The BiVO4 / FTO photoelectrode is placed with the conductive surface facing downward in a polytetrafluoroethylene reactor, and the precursor solution obtained in step (3) is slowly injected along the non-conductive surface of the BiVO4 / FTO photoelectrode. After being sealed with a stainless steel hydrothermal reactor, the reactor is kept in an electric constant temperature forced air drying oven at 100°C for 48 hours. After the constant temperature reaction time is over, the reactor is cooled to room temperature and the reactor is opened. The product is taken out and washed with N,N-dimethylformamide and methanol three times, and dried at 80°C to obtain a cobalt micron flower-bismuth vanadate nanophotoanode catalyst.

[0119] Characterization showed that the product obtained in this example had a micron flower-nano array structure with consistent size.

[0120] The same method as in Example 1 was used for testing. The cobalt micron flower-bismuth vanadate nanophotoanode catalyst prepared in this example was tested at 1.23V. RHE The photocurrent density under bias voltage reached 2.97 mA cm -2 , the photocurrent density has no obvious decay within 60 min.

[0121] Example 11

[0122] A method for preparing a cobalt micron flower-bismuth vanadate nanophotoanode catalyst is different from that of Example 1 in that: in (4), the reaction is carried out at a constant temperature of 110° C. for 48 hours.

[0123] Characterization showed that the product obtained in this example exhibited a micro-flower-nano array structure.

[0124] Example 12

[0125] A method for preparing a cobalt micron flower-bismuth vanadate nanophotoanode catalyst is different from that of Example 1 in that: in (1), 2 mL of N,N-dimethylformamide solution and 8 mL of anhydrous methanol solution are mixed evenly.

[0126] Characterization showed that the product obtained in this example exhibited a micro-flower-nano array structure.

[0127] Example 13

[0128] A method for preparing a cobalt micron flower-bismuth vanadate nanophotoanode catalyst is different from that of Example 1 in that: (1) 1 mL of N,N-dimethylformamide solution is mixed evenly with 9 mL of anhydrous methanol solution.

[0129] Characterization showed that the product obtained in this example exhibited a micro-flower-nano array structure.

[0130] Comparative Example 1

[0131] A method for preparing a cobalt-bismuth vanadate nanophotoanode catalyst comprises the following steps:

[0132] (1) Mix 5 mL of N,N-dimethylformamide solution and 5 mL of anhydrous methanol solution;

[0133] (2) adding 68.8 mg of chiral Schiff base carboxylic acid ligand and 24 mg of auxiliary ligand 4,4'-bipyridine to the uniform liquid obtained in step (1), stirring and ultrasonically mixing;

[0134] (3) Ultrasonic dissolution of pink cobalt chloride hexahydrate solid in deionized water to form a 0.1 M cobalt chloride aqueous solution, 3.2 mL of the cobalt chloride aqueous solution was added to the mixed solution obtained in step (2), ultrasonicated for 30 min, and then stirred for 30 min to obtain a precursor solution;

[0135] (4) The BiVO4 / FTO photoelectrode is placed with the conductive surface facing downward in a polytetrafluoroethylene reactor, and the precursor solution obtained in step (3) is slowly injected along the non-conductive surface of the BiVO4 / FTO photoelectrode. After sealing with a stainless steel hydrothermal reactor, the reactor is kept in an electric constant temperature forced air drying oven at 120°C for 48 hours. After the constant temperature reaction time is over, the reactor is cooled to room temperature and the reactor is opened. The obtained product is taken out and washed with N,N-dimethylformamide and methanol three times, and dried at 80°C to obtain a cobalt-bismuth vanadate nanophotoanode catalyst.

[0136] The product obtained in this comparative example cannot show a micron flower-nano array structure, and its scanning electron microscope image is as follows: Figure 5 As shown;

[0137] The same method as in Example 1 was used to test the cobalt-bismuth vanadate nanophotoanode catalyst prepared in this comparative example. RHE The photocurrent density under bias voltage reached 1.43 mA cm -2 ,like Figure 6 As shown in Figure 4, there is no obvious decay of the photocurrent density within 60 minutes.

[0138] Comparative Example 2

[0139] A method for preparing a cobalt-bismuth vanadate nanophotoanode catalyst comprises the following steps:

[0140] (1) Mix 6 mL of N,N-dimethylformamide solution and 4 mL of anhydrous methanol solution;

[0141] (2) adding 103.2 mg of chiral Schiff base carboxylic acid ligand and 36 mg of auxiliary ligand 4,4'-bipyridine to the homogeneous liquid obtained in step (1), stirring and ultrasonically mixing;

[0142] (3) Ultrasonic dissolution of pink cobalt chloride hexahydrate solid in deionized water to form a 0.1 M cobalt chloride aqueous solution, 4.8 mL of the cobalt chloride aqueous solution was added to the mixed solution obtained in step (2), ultrasonicated for 30 min, and then stirred for 30 min to obtain a precursor solution;

[0143] (4) The BiVO4 / FTO photoelectrode is placed with the conductive surface facing downward in a polytetrafluoroethylene reactor, and the precursor solution obtained in step (3) is slowly injected along the non-conductive surface of the BiVO4 / FTO photoelectrode. After sealing with a stainless steel hydrothermal reactor, the reactor is kept in an electric constant temperature forced air drying oven at 120°C for 48 hours. After the constant temperature reaction time is over, the reactor is cooled to room temperature and the reactor is opened. The obtained product is taken out and washed with N,N-dimethylformamide and methanol three times, and dried at 80°C to obtain a cobalt-bismuth vanadate nanophotoanode catalyst.

[0144] The product obtained in this comparative example cannot show a micron flower-nano array structure, and its scanning electron microscope image is as follows: Figure 7 As shown;

[0145] The same method as in Example 1 was used to test the cobalt-bismuth vanadate nanophotoanode catalyst prepared in this comparative example. RHE The photocurrent density under bias voltage reached 1.35 mA cm -2 ,like Figure 8 As shown in Figure 4, there is no obvious decay of the photocurrent density within 60 minutes.

[0146] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a cobalt micron flower-bismuth vanadate nanophotoanode catalyst, characterized by: The following steps are involved: S1. Evenly mix N,N-dimethylformamide and anhydrous methanol to form a mixed solution; S2, uniformly mixing the mixed solution, the chiral Schiff base carboxylic acid ligand, 4,4'-bipyridine and the cobalt chloride aqueous solution to obtain a precursor solution; wherein the chiral Schiff base carboxylic acid ligand has the structural formula: S3. Place the BiVO4 / FTO photoelectrode with the conductive surface facing downward in a polytetrafluoroethylene reactor, inject the precursor solution, seal it with a hydrothermal reactor, react at 60-110°C, and cool to room temperature after the reaction to obtain the cobalt micron flower-bismuth vanadate nanophotoanode catalyst.

2. The method for preparing the cobalt micron flower-bismuth vanadate nanophotoanode catalyst according to claim 1, characterized in that: In S1, the volume ratio of N,N-dimethylformamide to anhydrous methanol is 1-2:8-9.

3. The method for preparing the cobalt micron flower-bismuth vanadate nanophotoanode catalyst according to claim 2, characterized in that: The volume ratio of the N,N-dimethylformamide to anhydrous methanol is 1.5:8.

5.

4. The method for preparing the cobalt microflower-bismuth vanadate nanophotoanode catalyst according to claim 1, characterized in that: In S2, the mass ratio of the chiral Schiff base carboxylic acid ligand to 4,4'-bipyridine is 30-150:10-60.

5. The method for preparing the cobalt micron flower-bismuth vanadate nanophotoanode catalyst according to claim 4, characterized in that: The mass ratio of the chiral Schiff base carboxylic acid ligand to 4,4'-bipyridine is 8.6:

3.

6. The method for preparing the cobalt microflower-bismuth vanadate nanophotoanode catalyst according to claim 1, characterized in that: In S2, the mass volume ratio of the chiral Schiff base carboxylic acid ligand to the mixed solution is 34.4-103.2 mg:10 ml.

7. The method for preparing the cobalt microflower-bismuth vanadate nanophotoanode catalyst according to claim 1, characterized in that: In S2, the molar ratio of cobalt chloride to chiral Schiff base carboxylic acid ligand in the cobalt chloride aqueous solution is 2-1:

1.

8. The method for preparing the cobalt microflower-bismuth vanadate nanophotoanode catalyst according to any one of claims 1 to 7, characterized in that: In S3, the reaction time is 12-48 hours.

9. A cobalt micron flower-bismuth vanadate nanophotoanode catalyst, characterized by: The catalyst is prepared by the method for preparing the cobalt micron flower-bismuth vanadate nanophotoanode catalyst according to any one of claims 1 to 8.

10. Use of the cobalt microflower-bismuth vanadate nanophotoanode catalyst as claimed in claim 9 as a photoelectrocatalyst for catalyzing water oxidation reaction.

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