A CoSnO3 / BiVO4 photoanode, preparation method and application thereof in preparing hydrogen peroxide

Abstract

The application belongs to the technical field of photoelectrolysis of water materials, and relates to a CoSnO3 / BiVO4 photoelectric anode, a preparation method and application of the CoSnO3 / BiVO4 photoelectric anode in preparation of hydrogen peroxide, which comprises the following steps: 1, cleaning a conductive substrate; 2, preparing CoSn(OH)6 powder by a coprecipitation method after adding solution A into Co and Sn sources and then hydrothermal preparation; 3, dissolving Bi sources in a solvent B to prepare a Bi precursor solution, and introducing the Bi sources on the conductive substrate by an electrodeposition method; 4, dissolving V sources in a solvent C, introducing the V sources on the conductive substrate by using a spin coating device, and heating and calcining in a high-temperature heating device to prepare a photoelectric anode BiVO4 layer; 5, introducing CoSn(OH)6 on the conductive substrate by a spin coating method, and finally obtaining a CoSnO3 / BiVO4 photoelectric catalytic electrode by heating and calcining in a high-temperature heating device. The photoelectric catalyst prepared by the application can effectively improve the photocurrent of the original BiVO4 itself, and can have high selectivity and high yield in the reaction of preparing hydrogen peroxide by two-electron water oxidation, so that the cost of preparing hydrogen peroxide by photoelectric catalysis can be effectively reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photoelectrolysis of water materials, and relates to a CoSnO3 / BiVO4 photoelectric anode, a preparation method and application thereof in preparation of hydrogen peroxide. BACKGROUND

[0002] Hydrogen peroxide (H2O2) as an important chemical oxidant and medical disinfectant has a wide application prospect in the fields of environmental protection, medical health, chemical synthesis, etc. The traditional preparation method of hydrogen peroxide mainly relies on industrial chemical process, including chemical reaction of oxidizing agent and reducing agent. However, these methods usually require high temperature and high pressure conditions, produce a large amount of by-products, and at the same time cause considerable pollution to the environment. In order to solve these problems of traditional preparation method, photoelectrocatalytic technology has emerged in the field of hydrogen peroxide preparation. Photoelectrocatalytic technology is a new green synthesis method integrating photocatalysis and electrochemical reaction, which uses visible light or ultraviolet light to excite the electrons on the surface of the catalyst, thereby promoting the redox reaction. In particular, photoelectrocatalytic preparation of hydrogen peroxide has the advantages of high efficiency, environmental friendliness and controllability, and has become one of the current research hotspots.

[0003] Among many materials, BiVO4 has a high light utilization rate. Compared with TiO2 which can only respond in the ultraviolet light band, BiVO4 can respond in the visible light band (visible light accounts for 43% of sunlight). Therefore, in the research of photoelectrocatalysis, bismuth vanadate has always played an important role. However, due to its slow reaction kinetics, poor conductivity, high electron-hole pair recombination rate and other shortcomings, the actual situation of the photoelectric current level of BiVO4 photoelectric anode is far lower than its theoretical expectation. Therefore, in the field of photoelectrocatalysis, how to modify the photoelectrocatalytic performance of bismuth vanadate and improve its photocurrent density and selectivity of target product has become an important part of the research progress in recent years. Researchers often use morphology control, doping, composite heterojunction and other ways to improve the carrier mobility and conductivity, so as to ultimately achieve the purpose of improving the photoelectrocatalytic activity.

[0004] The unique octahedral structure of the perovskite structure metal oxide endows it with excellent photoelectrochemical performance, and also has a high specific surface area and a pore structure, which provides a channel for the entry of catalytic reaction substances and the exit of products in the catalytic reaction process, and the pore structure can also promote the diffusion and transmission of the reaction substances, thereby improving the efficiency of the catalytic reaction. The CoSnO3 powder prepared by the coprecipitation method has the characteristics of simple structure, high stability, fast electron transmission rate, etc. Meanwhile, as a mixed transition metal oxide, CoSnO3 has two different metal cations, and cobalt ions are proved to promote the generation of hydrogen peroxide by water oxidation, and tin-based catalysts often play an important role in electrocatalytic applications. After the CoSnO3 is compounded with the BiVO4, the excellent visible light excitation ability of the BiVO4 can be utilized, and the electron transmission capacity of the photoelectrochemical material is greatly improved through the CoSnO3, so as to reduce the recombination and consumption of the photo-generated carriers in the catalytic material, and make more photo-generated carriers participate in the redox reaction on the surface of the photoelectrochemical material, thereby promoting the photoelectrocatalytic reaction.

[0005] The application CN110468428A discloses a semiconductor anode material for photoelectrocatalytic preparation of hydrogen peroxide and a preparation method thereof. TiO2 nanorods are grown on FTO conductive glass, and Co3O4 nanoparticles are loaded thereon, to finally obtain a Co3O4 / TiO2 composite photoanode material. The preparation includes three steps of preparing a TiO2 nanorod precursor solution, preparing TiO2 nanorods grown on FTO conductive glass by a hydrothermal method, and obtaining the Co3O4 / TiO2 composite photoanode material by a drop coating method.

[0006] The application CN111979561B discloses a SnO x / BiVO4 electrode, a preparation method thereof and application thereof in photoelectrocatalytic synthesis of hydrogen peroxide. The method includes the following steps: dissolving stannous chloride in a mixed solution of ethylene glycol methyl ether and acetylacetone, ultrasonicating and standing, and then spin coating on the surface of a bismuth vanadate photoelectrode, and then annealing under an argon atmosphere to form a tin oxide passivation layer on the surface, thereby preparing the SnO x / BiVO4 electrode. The application can reduce the photo-corrosion of the surface bismuth vanadate, increase the stability of the bismuth vanadate, and improve the separation efficiency of the electron-hole pairs by loading a thin film of tin oxide passivation layer on the surface of the bismuth vanadate.

[0007] Invention CN118477653A discloses a WO3 / FeOOH heterojunction composite film and its preparation method and application, which relates to the field of thin film material preparation. The WO3 / FeOOH heterojunction composite film provided by the present invention is composed of a tungsten trioxide film and iron oxyhydroxide in situ grown on the surface of the tungsten trioxide film, wherein the tungsten trioxide film is in situ grown on the surface of the substrate. In the present invention, WO3 and FeOOH are both semiconductor photocatalytic materials that respond to visible light. After coupling, WO3 and FeOOH form a WO3 / FeOOH heterojunction, which has excellent photoelectrocatalytic performance.

[0008] Invention CN118345379A discloses a method for enhancing the photoelectrocatalytic synthesis of hydrogen peroxide by organic polymers, using a photoelectrochemical cell comprising a photocathode; the photocathode is an electrode having a light-responsive organic copolymer semiconductor catalyst; the cathode and an anode are coupled to form a photocathode-anode photoelectrochemical system, the photocathode being in contact with at least one reactant, an oxygen-containing mediator, dissolved in a continuous phase; the continuous phase comprising an electrolyte and an aqueous neutral solvent, the reactant of the oxygen-containing mediator being an oxygen-containing gas; under conditions of light and a voltage of 0 to 3 V or less, the photocathode reduces oxygen in the oxygen-containing gas in the continuous phase to hydrogen peroxide.

[0009] The above-mentioned invention method grows titanium dioxide nanorods on FTO conductive glass through a hydrothermal method and loads cobalt oxide nanoparticles to achieve efficient photoelectrocatalytic activity. Alternatively, stannous chloride is spin-coated on the surface of a bismuth vanadate electrode and annealed in an argon atmosphere to form a tin oxide passivation layer, which effectively improves the stability of bismuth vanadate and the electron-hole separation efficiency. Alternatively, a heterojunction composite film composed of tungsten trioxide and iron oxyhydroxide is coupled with tungsten oxide and iron oxyhydroxide to improve the visible light response and photoelectrocatalytic performance of the composite material. Alternatively, an organic polymer photocathode-anode photoelectrochemical system is proposed to reduce oxygen to hydrogen peroxide under light and low voltage, demonstrating the application potential of organic semiconductors in the field of photoelectrocatalysis.

[0010] However, the preparation of these catalytic electrodes in existing technologies requires extensive pre-processing and complex process flows, requiring sophisticated equipment and high-cost raw materials, and placing high demands on operator skill. Furthermore, most experiments have not yet explored perovskite-type metal oxide materials, which are more stable, more conductive, and have superior catalytic activity.

[0011] Therefore, seeking a low-cost, simple process, and good electrochemical stability and catalytic performance of the perovskite metal oxide material and BiVO4 composite catalyst preparation method is crucial for further research on the industrialization of photoelectrocatalytic production of hydrogen peroxide. Summary of the Invention

[0012] The technical solution adopted by the present invention to solve the technical problem is: a method for preparing a CoSnO3 / BiVO4 photoanode, comprising the following steps:

[0013] Step s1, cleaning the conductive substrate to remove impurities on the surface of the conductive substrate;

[0014] Step s2: adding solution A dropwise to the Co source and Sn source solutions by coprecipitation to prepare a catalyst slurry, and then transferring the slurry to a chemical reaction device for hydrothermal preparation of CoSn(OH)6 powder;

[0015] Step s3, dissolving a Bi source in solvent B to prepare a Bi precursor solution, and introducing the Bi source onto the conductive substrate treated in step s1 by electrodeposition;

[0016] Step s4, dissolving the V source in solvent C, then introducing the V source onto the conductive substrate treated in step s3 by spin coating using a spin coating device, and heating and calcining in a high-temperature heating device to prepare a photoanode BiVO4 layer;

[0017] Step s5, introducing CoSn(OH)6 onto the conductive substrate treated in step s4 by spin coating using a spin coating device and heating and calcining in a high-temperature heating device to finally obtain a CoSnO3 / BiVO4 photoelectrocatalytic electrode;

[0018] Solution A includes: one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide;

[0019] Solvent B includes one or more of glacial acetic acid, nitric acid, sulfuric acid, hydrochloric acid, oxalic acid, and deionized water;

[0020] Solvent C includes one or more of ethylene glycol, ethanol, methanol, isopropanol, and deionized water.

[0021] Preferably, the Co source includes: one or more of cobalt chloride hexahydrate, cobalt sulfate heptahydrate, hydrated cobalt carbonate, and cobalt nitrate hexahydrate; the Sn source includes: one or more of tin chloride dihydrate, anhydrous stannous chloride, tin sulfate, stannous sulfate, stannous carbonate, and stannous oxalate; the Bi source includes: one or more of bismuth nitrate pentahydrate, bismuth subcarbonate dihydrate, and bismuth sulfate; the V source includes: one or more of vanadium acetylacetonate, ammonium metavanadate, and vanadium pentoxide.

[0022] Preferably, the conductive substrate includes: fluorine-doped silicon dioxide conductive glass FTO, indium tin oxide transparent conductive film glass ITO, and a stainless steel plate.

[0023] Preferably, in step s2, the chemical reaction apparatus includes: a reactor, an autoclave, a stirred reactor, a continuous flow reactor, a microreactor, a batch reactor, a fixed bed reactor, or a fluidized bed reactor;

[0024] In step s4 and step s5, the high-temperature heating device includes: a muffle furnace, a tube furnace, a box furnace, a vacuum furnace, an atmosphere furnace, a resistance furnace, and an induction furnace.

[0025] In step s4 and step s5, the spin coating device includes: a glue spreader, a spin coater, a glue spinner, a spin coater, a spin film coater, a spin coating machine, a spin coater, and a vacuum coating machine.

[0026] Preferably, in step s1, the cleaning step includes: using deionized water, acetone, isopropyl alcohol and ethanol in sequence to ultrasonically bath the conductive substrate for 5 to 20 minutes; the sizes of the conductive substrate include: 1cm*1cm, 1cm*2cm, 2cm*2cm, and 2cm*3cm.

[0027] Preferably, in step s2, the stirring speed of the coprecipitation method is 100-800 rpm, the stirring time is 10 min-24 h, the hydrothermal time is 6-18 h, and the hydrothermal temperature is 120-200°C.

[0028] Preferably, in step s3, the electrodeposition conditions include: applying an external bias voltage of 0.5V to 2.5V vs. Ref for 10min to 2h;

[0029] Among them, in the three electrodes of electrodeposition, the counter electrode includes: one of a carbon counter electrode and a platinum counter electrode; the reference electrode includes: one of a saturated Hg / Hg2SO4 electrode, a saturated Ag / AgCl electrode, a saturated Hg / HgO electrode, and a calomel electrode; and the working electrode is a conductive substrate.

[0030] Preferably, in step s4, the temperature of the high-temperature heating device is set to 350-500° C., the heating rate is 5-10° C. / min, and the calcination time is 1-4 hours;

[0031] In step s5, the temperature of the high-temperature heating device is set to 250-400° C., the heating rate is 5-10° C. / min, and the calcination time is 1-4 hours.

[0032] The present invention also discloses a CoSnO3 / BiVO4 photoanode, which is prepared by adopting the above-mentioned preparation method of the CoSnO3 / BiVO4 photoanode.

[0033] The present invention also discloses an application of a CoSnO3 / BiVO4 photoanode in preparing hydrogen peroxide. The application adopts the CoSnO3 / BiVO4 photoanode to prepare hydrogen peroxide.

[0034] The beneficial effects of the present invention are:

[0035] The present invention prepares CoSn(OH)6 powder by coprecipitation and hydrothermal methods, and combines electrodeposition and spin coating methods to prepare dense and uniform BiVO4 catalyst layers and CoSnO3 catalyst layers on the surface of an FTO substrate, forming a composite photoelectrocatalytic anode material with excellent catalytic activity and strong corrosion resistance. After multiple photoelectrochemical tests, the catalyst does not obviously fall off and has good light transmittance. In addition, all raw materials used in the present invention have the advantages of low price, abundant output, and easy acquisition. In addition, the equipment requirements in the preparation process are low, easy to operate, and the preparation method is simple, which can realize industrial large-scale electrode preparation. Therefore, the photoelectrocatalyst prepared by the present invention can effectively improve the photocurrent of the original BiVO4 itself, and can have high selectivity and high yield in the reaction of preparing hydrogen peroxide by two-electron water oxidation, with the highest yield being 0.449 μmol min -1 cm -2 The Faradaic efficiency reaches 79.23%, and it has excellent stability. The preparation method is simple and easy to control, which can effectively reduce the cost of photoelectrocatalytic preparation of hydrogen peroxide and promote the popularization and application of this technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a scanning electron microscope morphology of the electrode samples of Example 1 and Example 2 of a CoSnO3 / BiVO4 photoanode, a preparation method, and its application in preparing hydrogen peroxide of the present invention;

[0037] Figure 2 This is a transmission electron microscope morphology image of the catalyst sample of Example 2 of the present invention;

[0038] Figure 3 is the XRD pattern of the catalyst samples of Examples 1-4 of the present invention;

[0039] Figure 4 1 is the XPS graph of the catalyst samples of Example 1 and Example 2 of the present invention;

[0040] Figure 5 1 is a linear sweep voltammetric curve test diagram of Examples 1-4 of the present invention;

[0041] Figure 6 Graph showing the photoelectrocatalytic Faraday efficiency and hydrogen peroxide yield of Example 2 of the present invention. DETAILED DESCRIPTION

[0042] The following will provide a clear and complete description of the relevant technologies in the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0043] This embodiment aims to provide a CoSnO3 / BiVO4 photoanode, a preparation method thereof, and its application in the photoelectrocatalytic production of hydrogen peroxide. It has low equipment requirements, simple process, and low cost in the water electrolysis process, further expanding the selection range of photoelectrocatalysts, reducing catalyst preparation costs, and improving photoelectrocatalytic efficiency.

[0044] Reference Figures 1-6 This embodiment provides a CoSnO3 / BiVO4 photoanode, a preparation method thereof, and an application thereof in photoelectrocatalytic production of hydrogen peroxide, specifically comprising the following steps:

[0045] Step s1, cleaning the conductive substrate to remove impurities on the surface of the conductive substrate;

[0046] Step s2: adding solution A dropwise to the Co source and Sn source solutions by coprecipitation to prepare a catalyst slurry, and then transferring the slurry to a chemical reaction device for hydrothermal preparation of CoSn(OH)6 powder;

[0047] Step s3, dissolving a Bi source in solvent B to prepare a Bi precursor solution, and introducing the Bi source onto the conductive substrate by electrodeposition;

[0048] Step s4, dissolving the V source in solvent C, then introducing the V source onto the conductive substrate treated in step s3 using a spin coating device by spin coating, and heating and calcining in a high-temperature heating device to prepare a photoanode BiVO4 layer;

[0049] Step s5, introducing CoSn(OH)6 onto the conductive substrate treated in step s4 by spin coating using a spin coating device and heating and calcining in a high-temperature heating device to finally obtain a CoSnO3 / BiVO4 photoelectrocatalytic electrode;

[0050] Furthermore, in step s1, the catalyst substrate is made of FTO with good light transmittance and conductivity, and has a size of 2 cm*3 cm.

[0051] Furthermore, in step s1, the cleaning step is to sequentially use deionized water, acetone, isopropyl alcohol and ethanol to ultrasonically bath the FTO for 10 minutes.

[0052] Furthermore, in step s2, the cobalt source is cobalt chloride hexahydrate, and the tin source is tin chloride dihydrate.

[0053] Furthermore, in step s2, tin chloride dihydrate and cobalt chloride hexahydrate are respectively dissolved in a mixed solvent of 30 mL of ethanol and 30 mL of deionized water, and 10 mL of a 2M sodium hydroxide solution is added dropwise to the tin chloride solution under stirring. Then, the cobalt chloride solution is added under stirring to obtain a blue-purple suspension mixture, and stirring is continued for 30 minutes to 24 hours.

[0054] Furthermore, in step s3, the Bi source is bismuth nitrate pentahydrate (Bi(NO3)3·5H2O).

[0055] Furthermore, in step s4, the V source is vanadium acetylacetonate.

[0056] Furthermore, in step s2, the stirring speed of the co-precipitation method is 600 rpm, and the stirring time is 30 min to 24 h.

[0057] Furthermore, in step s2, cobalt chloride hexahydrate is used as the cobalt source and tin chloride dihydrate is used as the tin source.

[0058] Furthermore, in step s2, the hydrothermal time is 10 to 12 hours, and the hydrothermal temperature is 150 to 180°C.

[0059] Furthermore, in step s3, the electrodeposition comprises the platinum counter electrode of the three electrodes, the saturated Hg / Hg2SO4 electrode of the reference electrode, and the conductive substrate of the working electrode, wherein the electrodeposition conditions are an external bias voltage of 2V to 2.2V vs. Ref for 1 hour.

[0060] Furthermore, in step s4, the amount of each drop in the spin coating method is 50 μL, the drop is added 3 times in total, the spin coating speed is 4000 rpm, the spin coating acceleration is 800 rpm / s, and the spin coating time is 30 s.

[0061] Furthermore, in step s4, the temperature of the muffle furnace is set to 450° C., the heating rate is 5° C. / min, and the calcination time is 2 h.

[0062] Furthermore, in step s4, the amount of each drop in the spin coating method is 50 μL, the total drop is 1 time, the spin coating speed is 4000 rpm, the spin coating acceleration is 800 rpm / s, and the spin coating time is 30 s.

[0063] Furthermore, in step s5, the temperature of the muffle furnace is set to 300° C., the heating rate is 5° C. / min, and the calcination time is 2 h.

[0064] Example

[0065] This embodiment provides a CoSnO3 / BiVO4 photoanode, a preparation method thereof, and an application thereof in photoelectrocatalytic production of hydrogen peroxide, comprising the following steps:

[0066] s1; cleaning the conductive substrate to remove impurities on the surface of the conductive substrate;

[0067] s2; Solution A was added dropwise to the Co source and Sn source solutions by coprecipitation to prepare a catalyst slurry, and the slurry was transferred to a chemical reaction device for hydrothermal preparation of CoSn(OH)6 powder;

[0068] s3; dissolving a Bi source in solvent B to prepare a Bi precursor solution, and introducing the Bi source onto a conductive substrate by electrodeposition;

[0069] s4; dissolving the V source in solvent C, and then introducing the V source by spin coating on the conductive substrate treated in s3 using a spin coating device and heating and calcining in a high-temperature heating device to prepare a photoanode BiVO4 layer;

[0070] s5; introducing CoSn(OH)6 onto the conductive substrate treated in s4 by spin coating using a spin coating device and heating and calcining in a high-temperature heating device to finally obtain a CoSnO3 / BiVO4 photoelectrocatalytic electrode;

[0071] Specific examples are given below to further illustrate the present invention:

[0072] Example 1:

[0073] 1) FTO cleaning

[0074] Use deionized water, acetone, isopropanol and ethanol to ultrasonically bath FTO for 10 minutes in sequence to remove impurities on the FTO surface so that the film can evenly cover the entire FTO surface during hydrothermal in situ growth.

[0075] 2) Introducing Bi source by electrodeposition

[0076] A Bi source was introduced onto a conductive fluorine-doped tin oxide (FTO)-coated glass substrate via electrodeposition. A 0.2 M Bi precursor solution was prepared by dissolving 8 mmol of Bi(NO₃)₃·5H₂O in 50 mL of an aqueous solution containing 16 mL of 99% acetic acid and 1.6 mL of concentrated HNO₃ (70 wt%). A three-electrode electrolytic cell was constructed using a Pt counter electrode, a saturated Hg / Hg₂SO₄ reference electrode, and cleaned FTO. An external bias of 2.11 V vs. Ref was applied for 1 h. The resulting Bi precursor film was rinsed with ultrapure water and allowed to dry naturally at room temperature.

[0077] 3) Introduce V source by spin coating and calcination

[0078] To convert the bismuth precursor film into a BiVO4 film, a V source was introduced via spin coating. A 0.05M vanadium acetylacetonate solution was prepared using isopropyl alcohol as the solvent. The spin coater was set to a speed of 4000 rpm, an acceleration of 800 rpm / s, and a spin coating time of 30 seconds. 50 μL of the vanadium acetylacetonate solution was evenly added dropwise three times. After drying at room temperature, the film was annealed in a muffle furnace at 450°C for 2 hours at a heating rate of 5°C / min.

[0079] Example 2:

[0080] 1) FTO cleaning

[0081] Use deionized water, acetone, isopropanol and ethanol to ultrasonically bath FTO for 10 minutes in sequence to remove impurities on the FTO surface so that the film can evenly cover the entire FTO surface during hydrothermal in situ growth.

[0082] 2) Preparation of CoSn(OH)6 powder by coprecipitation

[0083] CoSn(OH)6 powder was prepared by coprecipitation. 1.128g SnCl4·2H2O (0.005mol) and 1.1901g CoCl2·6H2O (0.005 mol) was dissolved in a mixed solvent of 30 mL of ethanol and 30 mL of deionized water to obtain a transparent solution; NaOH (2 M) solution was added dropwise to the tin chloride solution under magnetic stirring. During this process, Sn(OH)4 was first precipitated. As NaOH was continuously added, the white precipitate dissolved to form an aqueous solution of Na2Sn(OH)6, and the pH value of the solution was controlled above 12; then, cobalt chloride solution was added under magnetic stirring to obtain a blue-purple suspension mixture; after stirring for 10 hours, the formed suspension was transferred to a 100 ml polytetrafluoroethylene-lined stainless steel autoclave and maintained at 180°C for 12 hours; after the autoclave was naturally cooled to room temperature, the precipitate obtained by filtration was thoroughly washed several times with anhydrous ethanol and deionized water, and the precipitate was placed in a vacuum drying oven at 80°C and dried for 12 hours. After grinding, the precursor CoSn(OH)6 was obtained.

[0084] 3) Introducing Bi source by electrodeposition

[0085] A Bi source was introduced onto a conductive fluorine-doped tin oxide (FTO)-coated glass substrate via electrodeposition. A 0.2 M Bi precursor solution was prepared by dissolving 8 mmol of Bi(NO₃)₃·5H₂O in 50 mL of an aqueous solution containing 16 mL of 99% acetic acid and 1.6 mL of concentrated HNO₃ (70 wt%). A three-electrode electrolytic cell was constructed using a Pt counter electrode, a saturated Hg / Hg₂SO₄ reference electrode, and cleaned FTO. An external bias of 2.11 V vs. Ref was applied for 1 h. The resulting Bi precursor film was rinsed with ultrapure water and allowed to dry naturally at room temperature.

[0086] 4) Introduce V source by spin coating and calcination

[0087] To convert the bismuth precursor film into a BiVO4 film, a V source was introduced via spin coating. A 0.05M vanadium acetylacetonate solution was prepared using isopropyl alcohol as the solvent. The spin coater was set to a speed of 4000 rpm, an acceleration of 800 rpm / s, and a spin coating time of 30 seconds. 50 μL of the vanadium acetylacetonate solution was evenly added dropwise three times. After drying at room temperature, the film was annealed in a muffle furnace at 450°C for 2 hours at a heating rate of 5°C / min.

[0088] 5) Spin coating method to introduce CoSn(OH)6 and calcination

[0089] CoSn(OH)6 was also introduced by spin coating to complete the composite of CoSnO3 and BiVO4. The annealed film was rinsed with ultrapure water to remove excess V2O5 on the surface. A 0.1M CoSn(OH)6 solution was prepared using ethanol as the solvent. The spin coater parameters were set to a speed of 4000 rpm, an acceleration of 800 rpm / s, and a spin coating time of 30 seconds. 50 μL of the CoSn(OH)6 solution was evenly added and spin-coated. After drying at room temperature, the film was annealed in a muffle furnace at 300°C for 2 hours at a heating rate of 5°C / min.

[0090] Example 3:

[0091] 1) FTO cleaning

[0092] Use deionized water, acetone, isopropanol and ethanol to ultrasonically bath FTO for 10 minutes in sequence to remove impurities on the FTO surface so that the film can evenly cover the entire FTO surface during hydrothermal in situ growth.

[0093] 2) Preparation of CoSn(OH)6 powder by coprecipitation

[0094] CoSn(OH)6 powder was prepared by coprecipitation. 1.128g SnCl4·2H2O (0.005mol) and 1.1901g CoCl2·6H2O (0.005 mol) was dissolved in a mixed solvent of 30 mL of ethanol and 30 mL of deionized water to obtain a transparent solution; NaOH (2 M) solution was added dropwise to the tin chloride solution under magnetic stirring. During this process, Sn(OH)4 was first precipitated. As NaOH was continuously added, the white precipitate dissolved to form an aqueous solution of Na2Sn(OH)6, and the pH value of the solution was controlled above 12; then cobalt chloride solution was added under magnetic stirring to obtain a blue-purple suspension mixture; after stirring for 30 minutes, the formed suspension was transferred to a 100 ml polytetrafluoroethylene-lined stainless steel autoclave and maintained at 180°C for 12 hours; after the autoclave was naturally cooled to room temperature, the precipitate obtained by filtration was thoroughly washed several times with anhydrous ethanol and deionized water, and the precipitate was placed in a vacuum drying oven at 80°C and dried for 12 hours. After grinding, the precursor CoSn(OH)6 was obtained.

[0095] 3) Introducing Bi source by electrodeposition

[0096] A Bi source was introduced onto a conductive fluorine-doped tin oxide (FTO)-coated glass substrate via electrodeposition. A 0.2 M Bi precursor solution was prepared by dissolving 8 mmol of Bi(NO₃)₃·5H₂O in 50 mL of an aqueous solution containing 16 mL of 99% acetic acid and 1.6 mL of concentrated HNO₃ (70 wt%). A three-electrode electrolytic cell was constructed using a Pt counter electrode, a saturated Hg / Hg₂SO₄ reference electrode, and cleaned FTO. An external bias of 2.11 V vs. Ref was applied for 1 h. The resulting Bi precursor film was rinsed with ultrapure water and allowed to dry naturally at room temperature.

[0097] 4) Introduce V source by spin coating and calcination

[0098] To convert the bismuth precursor film into a BiVO4 film, a V source was introduced via spin coating. A 0.05M vanadium acetylacetonate solution was prepared using isopropyl alcohol as the solvent. The spin coater was set to a speed of 4000 rpm, an acceleration of 800 rpm / s, and a spin coating time of 30 seconds. 50 μL of the vanadium acetylacetonate solution was evenly added dropwise three times. After drying at room temperature, the film was annealed in a muffle furnace at 450°C for 2 hours at a heating rate of 5°C / min.

[0099] 5) Spin coating method to introduce CoSn(OH)6 and calcination

[0100] CoSn(OH)6 was also introduced by spin coating to complete the composite of CoSnO3 and BiVO4. The annealed film was rinsed with ultrapure water to remove excess V2O5 on the surface. A 0.1M CoSn(OH)6 solution was prepared using ethanol as the solvent. The spin coater parameters were set to a speed of 4000 rpm, an acceleration of 800 rpm / s, and a spin coating time of 30 seconds. 50 μL of the CoSn(OH)6 solution was evenly added and spin-coated. After drying at room temperature, the film was annealed in a muffle furnace at 300°C for 2 hours at a heating rate of 5°C / min.

[0101] Example 4:

[0102] 1) FTO cleaning

[0103] Use deionized water, acetone, isopropanol and ethanol to ultrasonically bath FTO for 10 minutes in sequence to remove impurities on the FTO surface so that the film can evenly cover the entire FTO surface during hydrothermal in situ growth.

[0104] 2) Preparation of CoSn(OH)6 powder by coprecipitation

[0105] CoSn(OH)6 powder was prepared by coprecipitation. 1.128g SnCl4·2H2O (0.005mol) and 1.1901g CoCl2·6H2O (0.005 mol) was dissolved in a mixed solvent of 30 mL of ethanol and 30 mL of deionized water to obtain a transparent solution; NaOH (2 M) solution was added dropwise to the tin chloride solution under magnetic stirring. During this process, Sn(OH)4 was first precipitated. As NaOH was continuously added, the white precipitate dissolved to form an aqueous solution of Na2Sn(OH)6, and the pH value of the solution was controlled above 12; then, cobalt chloride solution was added under magnetic stirring to obtain a blue-purple suspension mixture; after stirring for 24 hours, the formed suspension was transferred to a 100 ml polytetrafluoroethylene-lined stainless steel autoclave and maintained at 180°C for 12 hours; after the autoclave was naturally cooled to room temperature, the precipitate obtained by filtration was thoroughly washed several times with anhydrous ethanol and deionized water, and the precipitate was placed in a vacuum drying oven at 80°C and dried for 12 hours. After grinding, the precursor CoSn(OH)6 was obtained.

[0106] 3) Introducing Bi source by electrodeposition

[0107] A Bi source was introduced onto a conductive fluorine-doped tin oxide (FTO)-coated glass substrate via electrodeposition. A 0.2 M Bi precursor solution was prepared by dissolving 8 mmol of Bi(NO₃)₃·5H₂O in 50 mL of an aqueous solution containing 16 mL of 99% acetic acid and 1.6 mL of concentrated HNO₃ (70 wt%). A three-electrode electrolytic cell was constructed using a Pt counter electrode, a saturated Hg / Hg₂SO₄ reference electrode, and cleaned FTO. An external bias of 2.11 V vs. Ref was applied for 1 h. The resulting Bi precursor film was rinsed with ultrapure water and allowed to dry naturally at room temperature.

[0108] 4) Introduce V source by spin coating and calcination

[0109] To convert the bismuth precursor film into a BiVO4 film, a V source was introduced via spin coating. A 0.05M vanadium acetylacetonate solution was prepared using isopropyl alcohol as the solvent. The spin coater was set to a speed of 4000 rpm, an acceleration of 800 rpm / s, and a spin coating time of 30 seconds. 50 μL of the vanadium acetylacetonate solution was evenly added dropwise three times. After drying at room temperature, the film was annealed in a muffle furnace at 450°C for 2 hours at a heating rate of 5°C / min.

[0110] 5) Spin coating method to introduce CoSn(OH)6 and calcination

[0111] CoSn(OH)6 was also introduced by spin coating to complete the composite of CoSnO3 and BiVO4. The annealed film was rinsed with ultrapure water to remove excess V2O5 on the surface. A 0.1M CoSn(OH)6 solution was prepared using ethanol as the solvent. The spin coater parameters were set to a speed of 4000 rpm, an acceleration of 800 rpm / s, and a spin coating time of 30 seconds. 50 μL of the CoSn(OH)6 solution was evenly added and spin-coated. After drying at room temperature, the film was annealed in a muffle furnace at 300°C for 2 hours at a heating rate of 5°C / min.

[0112] Figure 1The following are scanning electron microscope images of Examples 1 and 2 of the present invention. A CoSn(OH)6 powder sample was prepared by coprecipitation, and a CoSnO3 / BiVO4 photoanode film was prepared on a FTO conductive glass substrate by electrodeposition, spin coating, and calcination. A BiVO4 blank control sample was also prepared using the same film-forming method. As shown in the figure, the BiVO4 film sample prepared on the FTO conductive glass substrate exhibits an amorphous morphology, with a rough surface but consistent thickness. The nanocrystals sintered together to form a relatively compact structure. It can be seen from the figure that the CoSnO3 obtained after calcination exhibits a uniform cubic morphology, with a particle size maintained at approximately 800nm, and can be evenly covered on the surface of the BiVO4 layer. The cross-sectional SEM image of the CoSnO3 / BiVO loaded on the FTO conductive glass substrate clearly distinguishes the CoSnO3 layer, the BiVO4 layer, and the FTO layer, wherein the CoSnO3 cubes are relatively evenly embedded on the surface of the BiVO4 layer, and the thickness of the BiVO4 layer is maintained at approximately 267.5nm. Figure 2 This is the transmission electron microscopy image of Example 2. High-resolution transmission electron microscopy (HR-TEM) clearly shows that there are two obvious lattice spacings of 0.464nm and 0.216nm inside the image, corresponding to the (0 1 1) plane of monoclinic phase BiVO4 (PDF#14-0688) and the (1 1 2) plane of CoSnO3 (PDF#28-1236), respectively. This indicates that CoSnO3 and BiVO4 are successfully composited.

[0113] Figure 3The X-ray diffraction (XRD) patterns of the samples of Examples 1 and 2 of the present invention show distinct peaks near 2Theta values ​​of 26.91°, 34.19°, and 34.61° for both samples prepared by the co-precipitation method with stirring times of 30 minutes and 10 hours, respectively. This corresponds to the CoSnO3 standard card in PDF#28-1236. However, in the powder sample prepared with a stirring time of 30 minutes, peaks of both CoO and SnO2 impurities are also observed. This phenomenon is attributed to the incomplete formation of CoSnO3 during the co-precipitation method due to the short stirring time. When the stirring time is extended to 10 hours, a larger, broad peak in the range of 32-35° is observed, indicating the formation of amorphous CoSnO3. Excessive impurity peaks are not observed, indicating that nearly pure CoSnO3 has been prepared. X-ray diffraction (XRD) patterns of CoSnO3 / BVO loaded onto a conductive glass substrate (FTO) revealed no significant difference in peak position between the three catalyst samples: CoSnO3 / BVO with controlled stirring times of 24h and 10h, and pure BVO. All samples contained peaks of a heterogeneous phase, including Bi2O3 and SnO2 from the FTO itself. The Bi2O3 heterogeneous peak is due to the incomplete reaction between the Bi source introduced by electrodeposition and the V source introduced by spin coating. Some of the Bi source did not come into contact with the V source, resulting in the formation of Bi2O3 during the subsequent calcination process. The lack of significant peak position differences among the three catalyst samples is attributed to the relatively small amount of spin-coated CoSn(OH)6; the introduction of excessive CoSnO3 would have affected the light absorption properties of the composite catalyst.

[0114] Figure 4 The XPS spectra of the samples of Example 1 and Example 2 of the present invention are shown in the following figure. From the overall spectra of the original BiVO4 and CoSnO3 / BVO samples, the characteristic peaks of Bi, V, and O contained in BiVO4 can be seen in both samples. The peaks of Co 2p, Sn 3d, and Bi 3p appear in the CoSnO3 / BVO sample, which also indicates the successful recombination of CoSnO3 and BiVO4. In the Sn 3d spectrum, the two Sn 3d peaks of CoSnO3 / BVO at 486.6 and 495 eV are 5 / 2 and Sn 3d 3 / 2 The peak confirmed Sn 4+ The Co 2p spectrum shows two fitting peaks at 780.7 and 796.5 eV, accompanied by two satellite peaks (785.4 and 802.3 eV), corresponding to the Co 2p 3 / 2 and Co 2p 1 / 2 As can be seen from the figure, the Bi(4f 5 / 2 ) and Bi(4f7 / 2 ) with binding energies at 163.77 and 158.47 eV, respectively. For the CoSnO3 / BVO sample, these peaks shift slightly to lower energies, appearing at 163.96 and 158.59 eV, respectively. Furthermore, the difference in V 2p binding energies between BiVO4 and CoSnO3 / BVO is negligible. The O1s spectrum reveals the presence of oxygen vacancies in addition to lattice oxygen in the CoSnO3 / BVO sample. This is likely attributed to the oxygen vacancies formed by oxygen abstraction from the lattices of the CoSnO3 and BiVO4 composite catalyst during the formation of the two oxygen-containing compounds during the spin-coating and calcination of CoSn(OH)6.

[0115] Figure 5 For the photoelectrochemical tests of all embodiments of the present invention, a xenon lamp (100 mW cm -2 The photoelectrochemical performance of a CoSnO3 / BiVO4 catalyst photoanode was measured in a 1M Na2CO3 electrolyte using a standard spectrum (AM 1.5G) simulating the Earth's surface. For comparison, the photoelectrochemical activity of pristine BiVO4 and samples obtained from the coprecipitation method with stirring times of 10 hours, 30 minutes, and 24 hours were also studied. As shown in the figure, the photocurrent density of the pristine BiVO4 photoanode is relatively low (only 0.121 mA cm at 1.59 V vs. RHE). -2 ), and the composite CoSnO3 / BVO sample showed better photoelectric performance, with a photocurrent density of 3.47 mA cm under the same external bias potential. -2, the photocurrent density increased by about 28.68 times. The unique octahedral structure of perovskite-structured metal oxides gives it excellent photoelectrochemical properties. It also has a high specific surface area and pore structure. During the catalytic reaction, it provides channels for the catalytic reaction substances to enter and the products to leave. The pore structure can also promote the diffusion and transport of the reaction substances, thereby improving the efficiency of the catalytic reaction. The CoSnO3 powder prepared by the co-precipitation method has the characteristics of simple structure, high stability, and fast electron transfer rate. At the same time, CoSnO3, as a mixed transition metal oxide, has two different metal cations, because the atomic mixed matrix helps to regulate the internal stress of the electrode during volume changes. More importantly, due to the different expansion coefficients of the two metal elements, the stability of the mixed transition metal oxide is better than that of a single metal transition metal oxide. At the same time, the activation energy barrier between different cations is reduced, thereby enhancing electron transfer. The composite of CoSnO3 and BiVO4 not only utilizes BiVO4's excellent visible light excitation ability, but also significantly enhances the electron transport capacity of the photoelectrocatalytic material through CoSnO3, reducing the recombination and consumption of photogenerated carriers within the catalytic material and enabling more photogenerated carriers to participate in the redox reaction on the surface of the photoelectrocatalytic material. The LSV curve in the figure clearly shows that the onset potential of CoSnO3 / BVO is significantly reduced compared to pure BVO, and the electrode reaction on the CoSnO3 / BVO composite material can occur faster. At the same time, the It curve in the figure shows that the CoSnO3 / BVO composite material also obtains a higher photocurrent density under the same bias, which indicates that the composite material can significantly improve its photoelectrocatalytic performance. The EIS graph shows that the addition of CoSnO3 accelerates the electron transport rate on the catalyst surface, enabling the effective separation and transfer of photogenerated electrons and holes on the catalyst surface. The charge transfer impedance is low, and the charge transfer efficiency between electrons and reactants is high, thereby promoting the progress of the photoelectrocatalytic reaction. The stirring time in the coprecipitation method is one of the important factors affecting its crystal growth, which will significantly affect the nucleation and growth process of the crystal, thereby affecting the size and morphology of the final particles. Setting the experimental conditions to 10 hours of stirring can provide ideal conditions for crystal growth, ensuring sufficient nucleation number and crystal uniformity, while avoiding agglomeration or excessive crystallization caused by too long stirring. On the other hand, too short a stirring time may not be enough to form uniformly distributed crystals. On the other hand, due to incomplete reaction, other impurities may appear in the sample, thereby affecting the catalytic performance of the catalyst. Excessive stirring time may also cause the crystal size to be too small or agglomerate, which in turn reduces its photoelectric performance.

[0116] Figure 6The graph of the photoelectrocatalytic Faraday efficiency and hydrogen peroxide yield of Example 2 of the present invention shows that the catalytic performance of the CoSnO3 / BiVO4 photoelectrocatalytic anode remains good when the test is continued for more than 120 min, with the highest yield during the test being 0.449 μmol min -1 cm -2 , the Faraday efficiency reaches 79.23%.

[0117] In summary, the present invention prepares CoSn(OH)6 powder by co-precipitation and hydrothermal methods, and combines electrodeposition and spin coating to prepare dense and uniform BiVO4 catalyst layers and CoSnO3 catalyst layers on the surface of an FTO substrate, forming a composite photoelectrocatalytic anode material with excellent catalytic activity and strong corrosion resistance. After multiple photoelectrochemical tests, the catalyst does not obviously fall off and has good light transmittance. Therefore, the photoelectrocatalyst prepared by the present invention can effectively improve the photocurrent of the original BiVO4 itself, and can have high selectivity and high yield in the reaction of preparing hydrogen peroxide by two-electron water oxidation, thereby effectively reducing the cost of photoelectrocatalytic preparation of hydrogen peroxide and promoting the popularization and application of this technology.

[0118] It should be emphasized that the above are only preferred embodiments of the present invention and do not limit the present invention in any form. Any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a CoSnO3 / BiVO4 photoanode, characterized in that: The following steps are involved: Step s1, cleaning the conductive substrate to remove impurities on the surface of the conductive substrate; Step s2: adding solution A dropwise to the Co source and Sn source solutions by coprecipitation to prepare a catalyst slurry, and then transferring the slurry to a chemical reaction device for hydrothermal preparation of CoSn(OH)6 powder; Step s3, dissolving a Bi source in solvent B to prepare a Bi precursor solution, and introducing the Bi source onto the conductive substrate treated in step s1 by electrodeposition; Step s4, dissolving the V source in solvent C, then introducing the V source onto the conductive substrate treated in step s3 by spin coating using a spin coating device, and heating and calcining in a high-temperature heating device to prepare a photoanode BiVO4 layer; Step s5, introducing CoSn(OH)6 onto the conductive substrate treated in step s4 by spin coating using a spin coating device and heating and calcining in a high-temperature heating device to finally obtain a CoSnO3 / BiVO4 photoelectrocatalytic electrode; The solution A comprises: one or more of sodium hydroxide, potassium hydroxide, and calcium hydroxide; The solvent B includes one or more of glacial acetic acid, nitric acid, sulfuric acid, hydrochloric acid, oxalic acid, and deionized water; The solvent C includes one or more of ethylene glycol, ethanol, methanol, isopropanol, and deionized water; In the step s2, the stirring speed of the coprecipitation method is 100-800 rpm, and the stirring time is 10h-24h; the hydrothermal time is 6-18h, and the hydrothermal temperature is 120-200°C.

2. The method for preparing a CoSnO3 / BiVO4 photoanode according to claim 1, characterized in that: The Co source includes one or more of cobalt chloride hexahydrate, cobalt sulfate heptahydrate, hydrated cobalt carbonate, and cobalt nitrate hexahydrate; the Sn source includes one or more of tin chloride dihydrate, anhydrous stannous chloride, tin sulfate, stannous sulfate, stannous carbonate, and stannous oxalate; the Bi source includes one or more of bismuth nitrate pentahydrate, bismuth subcarbonate dihydrate, and bismuth sulfate; and the V source includes one or more of vanadium acetylacetonate, ammonium metavanadate, and vanadium pentoxide.

3. The method for preparing a CoSnO3 / BiVO4 photoanode according to claim 1, characterized in that: The conductive substrate includes: fluorine-doped silicon dioxide conductive glass FTO, indium tin oxide transparent conductive film glass ITO, and a stainless steel plate.

4. The method for preparing a CoSnO3 / BiVO4 photoanode according to claim 1, wherein: In step s2, the chemical reaction apparatus includes: a reactor, an autoclave, a stirred reactor, a continuous flow reactor, a microreactor, a batch reactor, a fixed bed reactor, and a fluidized bed reactor; In step s4 and step s5, the high-temperature heating device includes: a muffle furnace, a tube furnace, a box furnace, a vacuum furnace, an atmosphere furnace, a resistance furnace, and an induction furnace; In step s4 and step s5, the spin coating device includes: a glue spreader, a spin coater, a glue spinner, a spin coater, a spin film coater, a spin coating machine, a spin coater, and a vacuum coating machine.

5. The method for preparing a CoSnO3 / BiVO4 photoanode according to claim 1, wherein: In step s1, the cleaning step includes: using deionized water, acetone, isopropyl alcohol and ethanol in an ultrasonic bath in sequence for 5 to 20 minutes; the sizes of the conductive substrate include: 1 cm*1 cm, 1 cm*2 cm, 2 cm*2 cm, and 2 cm*3 cm.

6. The method for preparing a CoSnO3 / BiVO4 photoanode according to claim 1, wherein: In the step s3, the electrodeposition conditions include: applying an external bias voltage of 0.5V to 2.5V vs. Ref for 10min to 2h; Among them, in the three electrodeposited electrodes, the counter electrode includes: one of a carbon counter electrode and a platinum counter electrode; the reference electrode includes: one of a saturated Hg / Hg2SO4 electrode, a saturated Ag / AgCl electrode, a saturated Hg / HgO electrode, and a calomel electrode; and the working electrode is a conductive substrate.

7. The method for preparing a CoSnO3 / BiVO4 photoanode according to claim 1, wherein: In step s4, the temperature of the high-temperature heating device is set to 350-500°C, the heating rate is 5-10°C / min, and the calcination time is 1-4h; In the step s5, the temperature of the high-temperature heating device is set to 250-400° C., the heating rate is 5-10° C. / min, and the calcination time is 1-4 hours.

8. A CoSnO3 / BiVO4 photoanode, characterized in that The CoSnO3 / BiVO4 photoanode is prepared by the preparation method of the CoSnO3 / BiVO4 photoanode according to any one of claims 1 to 7.

9. Use of a CoSnO3 / BiVO4 photoanode in the preparation of hydrogen peroxide, characterized in that: The application uses the CoSnO3 / BiVO4 photoanode in claim 8 to prepare hydrogen peroxide.

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