Preparation method and application of BiVO4 / Mn-Co (OH) F composite photo-anode
By coupling the Mn-Co(OH)F co-catalyst to the BiVO4 photoanode to form a BiVO4/Mn-Co(OH)F composite photoanode, the problems of fast charge recombination rate and poor charge mobility on the surface of the BiVO4 photoanode were solved, and the photoelectrochemical performance was significantly improved.
Patent Information
- Application Number
- CN202510837749.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-23
- Publication Date
- 2025-09-23
AI Technical Summary
Existing BiVO4 photoanodes have problems such as fast surface charge recombination rate and poor charge mobility, which limits their photoelectrochemical water splitting performance.
A direct hydrothermal method was used to couple metal manganese-doped fluorinated cobalt hydroxyl Mn-Co(OH)F as a co-catalyst on the BiVO4 photoanode to form a BiVO4/Mn-Co(OH)F composite photoanode.
The photoelectrocatalytic activity and stability were improved, the photocurrent density reached 4.93 mA/cm2, and the photoelectrochemical performance was significantly enhanced.
Smart Images
Figure HDA0005461158760000011 
Figure HDA0005461158760000012 
Figure HDA0005461158760000021
Abstract
Description
Technical Field
[0001] The present invention belongs to the field of photoelectrochemistry, and in particular relates to a preparation method and application of a BiVO4 / Mn-Co(OH)F composite photoanode. Background Art
[0002] The damage to the environment caused by the large-scale use of fossil fuels has prompted people to explore how to improve the utilization rate of renewable energy. Using sunlight as an inexhaustible resource to obtain clean energy is the best choice to deal with these problems. Photoelectrochemical (PEC) water splitting technology provides a green and environmentally friendly way to obtain energy in the future. However, the lack of an effective photoanode that converts light into charge carriers and further oxidizes water to oxygen has always been an important technical obstacle to photoelectrochemical water splitting. At present, a variety of low-cost, abundant resources and light-corrosion-resistant metal oxides have been developed and studied as photoanodes for photoelectrochemical water oxidation. Among these photoanode materials, monoclinic bismuth vanadate (BiVO4) has a relatively ideal band gap for absorbing sunlight. However, BiVO4 still has the problems of fast surface charge recombination and poor charge mobility, which greatly limits its PEC performance. Summary of the Invention
[0003] In order to solve the above technical problems, the present invention provides a BiVO4 / Mn-Co(OH)F composite photoanode based on BiVO4 photoanode. The optimized composite photoanode has a photocurrent density of 4.93 mA / cm at 1.23 V vs RHE. 2 , which not only improves the photoelectrocatalytic activity but also improves the stability.
[0004] The technical solution adopted by the present invention is: a method for preparing a BiVO4 / Mn-Co(OH)F composite photoanode, which uses BiVO4 photoanode as a substrate and metal manganese-doped fluorinated cobalt hydroxyl Mn-Co(OH)F as a co-catalyst, and adopts a direct hydrothermal method to couple the co-catalyst to the BiVO4 photoanode to form a BiVO4 / Mn-Co(OH)F composite photoanode.
[0005] A method for preparing a BiVO4 / Mn-Co(OH)F composite photoanode comprises the following steps: ultrasonically dissolving cobalt nitrate hexahydrate in deionized water, then sequentially adding ammonium fluoride, hydrated hydrazine, and anhydrous manganese chloride; after stirring, transferring the mixed solution to a stainless steel autoclave pre-installed with a BiVO4 photoanode for a hydrothermal reaction; and after the reaction is completed, removing the material, rinsing it with deionized water, and drying it at 60°C for 30 minutes to obtain the BiVO4 / Mn-Co(OH)F composite photoanode.
[0006] Furthermore, in the above-mentioned preparation method of the BiVO4 / Mn-Co(OH)F composite photoanode, the molar ratio of Mn / Co is 14-18%.
[0007] Furthermore, the above-mentioned method for preparing a BiVO4 / Mn-Co(OH)F composite photoanode comprises the following steps:
[0008] 1) Preparation of an electrodeposition solution: Bi(NO3)3·5H2O was added to a nitric acid solution having a pH of 1.7, and after ultrasonication at 25°C for 10 min, potassium iodide was added and stirred vigorously until completely dissolved to obtain solution A. An ethanol solution of p-benzoquinone was mixed with solution A and ultrasonication was continued until no precipitation occurred to obtain an electrodeposition solution.
[0009] 2) Preparation of the BiVO4 photoanode: An electrodeposition solution was placed in a container connected to an electrochemical workstation. FTO was immersed in the electrodeposition solution as the working electrode, a Pt wire as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Using a three-electrode system, BiOI thin films were electroplated at an applied bias of -0.1 V vs. Ag / AgCl for 5 minutes. Vanadyl acetylacetonate was dissolved in dimethyl sulfoxide, and the resulting solution was evenly drop-coated on the BiOI surface. The solution was then calcined in a muffle furnace and, after cooling, immersed in a 1 mol / L aqueous NaOH solution for 30 minutes. The film was then rinsed with deionized water and dried with nitrogen to obtain the BiVO4 photoanode.
[0010] Furthermore, in the above-mentioned method for preparing a BiVO4 / Mn-Co(OH)F composite photoanode, the calcination is to increase the temperature to 450°C at a heating rate of 2°C / min and continue heating for 2 hours.
[0011] Furthermore, in the above-mentioned method for preparing a BiVO4 / Mn-Co(OH)F composite photoanode, the hydrothermal reaction is a hydrothermal reaction at 100°C for 6 hours.
[0012] The present invention provides an application of a BiVO4 / Mn-Co(OH)F composite photoanode in catalyzing water to release oxygen under visible light.
[0013] The beneficial effects of the present invention are as follows: the preparation method of the composite photoanode prepared in this paper is simple, and the BiVO4 / Mn-Co(OH)F composite photoanode can be simply prepared in one step by a hydrothermal method; the photocurrent density of the BiVO4 / Mn-Co(OH)F composite photoanode at 1.23V vsRHE is 4.93mA / cm 2 By coupling the co-catalyst Mn-Co(OH)F layer on BiVO4, it not only improves the photoelectrochemical performance, but also protects the bismuth vanadate photoanode, further improving the stability of the composite photoanode. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Figure 1 1 is the XRD pattern of different materials prepared in Example 1.
[0015] Figure 2 This is a transmission electron microscope image of BiVO4 / Mn-Co(OH)F prepared in Example 1.
[0016] Figure 3 1 is the linear sweep voltammetry (LSV) curve of three different photoelectrodes in Example 4.
[0017] Figure 4 This is the effect of the composite photoanode prepared with different Mn / Co molar ratios in Example 4 on the photocurrent density.
[0018] Figure 5 2 is a chronoamperometry diagram of three different photoelectrodes in Example 2 under an applied bias of 0.8 V vs RHE. DETAILED DESCRIPTION
[0019] Example 1
[0020] (1) BiVO4 / Mn-Co(OH)F composite photoanode (Mn / Co molar ratio 16%), prepared as follows:
[0021] 1. Preparation of electrodeposition solution:
[0022] To 150 mL of pH 1.7 nitric acid solution, add 2.91 g of Bi(NO₃)₃·5H₂O. After sonication at 25°C for 10 minutes, add 9.96 g of potassium iodide and stir until the solution turns reddish-brown to obtain Solution A. Add p-benzoquinone to anhydrous ethanol and sonicate to dissolve it to obtain a 0.23 mol / L p-benzoquinone ethanol solution. Mix 60 mL of the 0.23 mol / L p-benzoquinone ethanol solution with Solution A and continue sonication until a dark red solution forms to obtain the electrodeposition solution.
[0023] 2. Preparation of BiVO4 photoanode:
[0024] The electrodeposition solution was placed in a container, connected to an electrochemical workstation, and the cleaned FTO conductive glass was immersed in the electrodeposition solution as the working electrode, a Pt wire was used as the counter electrode, and an Ag / AgCl electrode was used as the reference electrode. Using a three-electrode system, electroplating was performed at an external bias of -0.1V vs. Ag / AgCl for about 5 minutes. After removal, the electrodeposited layer was rinsed with deionized water and then blown dry with nitrogen to form a BiOI film. 0.106 g of vanadium acetylacetonate was dissolved in 1.0 mL of dimethyl sulfoxide (DMSO) and ultrasonicated until completely dissolved. 30 μL was evenly drop-coated on the surface of BiOI using a pipette, then placed in a muffle furnace and heated to 450°C at a heating rate of 2°C / min. The mixture was calcined for 2 h, cooled, and immersed in a 1 mol / L NaOH aqueous solution for about 30 min under rotor stirring until the BiVO4 surface turned golden yellow. The V2O5 on the BiVO4 surface was removed, and the mixture was rinsed with deionized water and dried with N2 to obtain a BiVO4 photoanode with a Mn / Co molar ratio of 16%.
[0025] 3. Preparation of BiVO4 / Mn-Co(OH)F composite photoanode:
[0026] At room temperature, 1 mmol of cobalt nitrate hexahydrate was ultrasonically dissolved in 30 mL of deionized water. Then, 0.187 g of ammonium fluoride, 100 microliters of hydrated hydrazine, and 0.02 g of anhydrous manganese chloride were added sequentially. The mixture was stirred for 10 minutes, and the resulting solution was transferred to a 50 mL stainless steel autoclave, into which a BiVO4 photoanode had been pre-installed. The resulting solution was then hydrothermally reacted at 100°C for 6 hours. After completion of the reaction, the material was removed, rinsed with deionized water, and dried at 60°C for 30 minutes to obtain a BiVO4 / Mn-Co(OH)F composite photoanode.
[0027] (2) Characterization
[0028] Figure 1 is the XRD pattern of different materials. Figure 1It can be seen that the XRD pattern of the BiVO4 / Mn-Co(OH)F composite photoanode is no different from that of BiVO4 alone, which is mainly due to the small loading amount of the Mn-Co(OH)F co-catalyst. In order to confirm the successful preparation of Mn-Co(OH)F, Mn-Co(OH)F powder was prepared using the same steps. According to JCPDS no. 50-0827, the diffraction peaks at 20.8°, 32.3°, 33.5°, 35.5°, 38.7°, 51.9°, 52.8°, 56.9°, 59.1°, and 61.6° correspond to the (110), (310), (201), (111), (211), (221), (420), (511), (002), and (601) planes of Co(OH)F, respectively. By observing the XRD pattern of Mn-Co(OH)F powder, it can be seen that the positions of some peaks have shifted significantly, indicating that metallic Mn is successfully doped on Co(OH)F.
[0029] Figure 2 This is a transmission electron microscope image of BiVO4 / Mn-Co(OH)F. Figure 2 It can be seen that the Mn-Co(OH)F co-catalyst was successfully prepared.
[0030] Example 2
[0031] (1) BiVO4 / Mn-Co(OH)F composite photoanode (Mn / Co molar ratio 14%), prepared as follows:
[0032] 1. Preparation of electrodeposition solution: same as in Example 1
[0033] 2. Preparation of BiVO4 photoanode: same as Example 1
[0034] 3. Preparation of BiVO4 / Mn-Co(OH)F composite photoanode:
[0035] At room temperature, 1 mmol of cobalt nitrate hexahydrate was ultrasonically dissolved in 30 mL of deionized water. Then, 0.187 g of ammonium fluoride, 100 microliters of hydrated hydrazine, and 0.0176 g of anhydrous manganese chloride were added sequentially. The mixture was stirred for 10 minutes, and the resulting solution was transferred to a 50 mL stainless steel autoclave, where a BiVO4 photoanode had been pre-installed. The resulting solution was then hydrothermally reacted at 100°C for 6 hours. After completion of the reaction, the material was removed, rinsed with deionized water, and dried at 60°C for 30 minutes to yield a BiVO4 / Mn-Co(OH)F composite photoanode with a Mn / Co molar ratio of 14%.
[0036] Example 3
[0037] (1) BiVO4 / Mn-Co(OH)F composite photoanode (Mn / Co molar ratio 18%), prepared as follows:
[0038] 1. Preparation of electrodeposition solution: same as in Example 1
[0039] 2. Preparation of BiVO4 photoanode: same as Example 1
[0040] 3. Preparation of BiVO4 / Mn-Co(OH)F composite photoanode:
[0041] At room temperature, 1 mmol of cobalt nitrate hexahydrate was ultrasonically dissolved in 30 mL of deionized water. Then, 0.187 g of ammonium fluoride, 100 microliters of hydrated hydrazine, and 0.022 g of anhydrous manganese chloride were added sequentially. The mixture was stirred for 10 minutes, and the resulting solution was transferred to a 50 mL stainless steel autoclave, into which a BiVO4 photoanode had been pre-installed. The resulting mixture was then hydrothermally reacted at 100°C for 6 hours. After completion of the reaction, the material was removed, rinsed with deionized water, and dried at 60°C for 30 minutes to yield a BiVO4 / Mn-Co(OH)F composite photoanode with a Mn / Co molar ratio of 18%.
[0042] Example 4
[0043] Application of BiVO4 / Mn-Co(OH)F composite photoanode in catalytic oxygen evolution from water under visible light
[0044] Electrochemical performance test of the electrode: The electrochemical performance of the composite electrode was tested using an electrochemical workstation CHI 660. During the test, a three-electrode system (BiVO4 / Mn-Co(OH)F composite electrode as the working electrode, Ag / AgCl as the reference electrode, and platinum wire as the counter electrode) was used. The electrolyte solution was a 1.0 M potassium borate buffer solution with a pH of 9.5, and the xenon lamp intensity was 100 mW / cm 2 The scan rate was 50 mV s -1 , the measured potentials are converted to RHE (E RHE =E Ag / AgCl +0.197V+0.059pH).
[0045] Figure 3 The linear sweep voltammetry (LSV) curves of three different photoelectrodes are shown in Figure 2. By comparison, it can be found that the current density of the unmodified BiVO4 photoanode is low. When Co(OH)F is coupled to BiVO4, the photocurrent density increases to 3.99 mA / cm 2 When Mn is further doped into Co(OH)F and coupled to BiVO4, the photocurrent density reaches as high as 4.93 mA / cm 2This indicates that the loading of cocatalyst Mn-Co(OH)F greatly improves the photoelectrolyte water splitting catalytic activity of BiVO4.
[0046] Figure 4 The effect of composite electrode materials prepared with different molar ratios of Mn / Co on the photocurrent density. Figure 4 It can be seen that when Mn / Co=16%, the photocurrent density of the composite electrode is the largest.
[0047] Figure 5 The chronoamperometry plots for three different photoelectrodes at an applied bias of 0.8 V vs RHE are shown. Under simulated sunlight and an applied bias of 0.8 V vs RHE, the stability of Co(OH)F as a co-catalyst alone is poor and does not protect BiVO4. However, the BiVO4 / Mn-Co(OH)F composite material can maintain a photocurrent density of 2.63 mA / cm3 under continuous illumination for 3600 s under the applied bias. 2 This indicates that the prepared material exhibits excellent stability and photoelectrolyte water splitting catalytic activity.
Claims
1. A method for preparing a BiVO4 / Mn-Co(OH)F composite photoanode, characterized in that: Using BiVO4 photoanode as substrate and manganese-doped fluorinated cobalt hydroxyl Mn-Co(OH)F as co-catalyst, the co-catalyst was coupled to the BiVO4 photoanode by direct hydrothermal method to form a BiVO4 / Mn-Co(OH)F composite photoanode.
2. The method for preparing a BiVO4 / Mn-Co(OH)F composite photoanode according to claim 1, characterized in that: In terms of molar ratio, Mn / Co = 14-18%.
3. The method for preparing a BiVO4 / Mn-Co(OH)F composite photoanode according to claim 1, characterized in that: The preparation method includes the following steps: ultrasonically dissolving cobalt nitrate hexahydrate in deionized water, then adding ammonium fluoride, hydrated hydrazine and anhydrous manganese chloride in sequence, stirring, transferring the mixed solution to a stainless steel autoclave pre-installed with a BiVO4 photoanode, and conducting a hydrothermal reaction. After the reaction is completed, the material is taken out, rinsed with deionized water, and dried at 60°C for 30 minutes to obtain a BiVO4 / Mn-Co(OH)F composite photoanode.
4. The method for preparing a BiVO4 / Mn-Co(OH)F composite photoanode according to claim 1, 2 or 3, wherein: The preparation method of the BiVO4 photoanode comprises the following steps: 1) Preparation of electrodeposition solution: Bi(NO3)3·5H2O was added to a nitric acid solution having a pH of 1.7, and after sonication at 25°C for 10 min, potassium iodide was added and stirred vigorously until completely dissolved to obtain solution A. Solution A was mixed with an ethanol solution of p-benzoquinone and continued sonication until no precipitation occurred to obtain the electrodeposition solution; 2) Preparation of the BiVO4 photoanode: An electrodeposition solution was placed in a container connected to an electrochemical workstation. FTO was immersed in the electrodeposition solution as the working electrode, a Pt wire as the counter electrode, and an Ag / AgCl electrode as the reference electrode. Using a three-electrode system, a BiO4 thin film was electroplated for 5 minutes at an applied bias of -0.1 V vs. Ag / AgCl. Vanadyl acetylacetonate was dissolved in dimethyl sulfoxide, and the resulting solution was evenly drop-coated on the BiOI surface. The solution was then calcined in a muffle furnace and, after cooling, immersed in a 1 mol / L aqueous NaOH solution for 30 minutes. The film was then rinsed with deionized water and dried with nitrogen to obtain the BiVO4 photoanode.
5. The method for preparing a BiVO4 / Mn-Co(OH)F composite photoanode according to claim 4, characterized in that: The calcination step is to increase the temperature to 450° C. at a heating rate of 2° C. / min and continue heating for 2 hours.
6. The method for preparing a BiVO4 / Mn-Co(OH)F composite photoanode according to claim 1, 2 or 3, wherein: The hydrothermal reaction is carried out at 100° C. for 6 hours.
7. Use of the BiVO4 / Mn-Co(OH)F composite photoanode prepared according to the method of claim 1, 2 or 3 in catalyzing water to release oxygen under visible light.