BiVO4 / CuInS2 composite film for photoelectric cathode protection as well as preparation method and application of BiVO4 / CuInS2 composite film

Abstract

The invention discloses a BiVO4 / CuInS2 composite film for photoelectric cathode protection and a preparation method and application thereof, and belongs to the technical field of photoelectric cathode protection, BiVO4 is grown on the surface of conductive glass through electroplating, CuInS2 is introduced through a hydrothermal method to construct a p-n heterojunction, the BiVO4 / CuInS2 composite film is prepared, consumption of photo-generated holes is promoted, the photoelectric conversion efficiency is improved, and the photoelectric conversion efficiency is improved. The coupling potential of the composite film and the 304 SS is subjected to cathodic polarization during illumination, sufficient protection is provided for metal, the metal shows long-acting and stable photoelectrochemical cathodic protection performance in a seawater environment, and efficient protection on the 304 SS in a bright state and a dark state without a hole trapping agent is achieved. Compared with other dispensing, spin coating and other methods, the method is easier to control and easier for large-scale production, and the prepared film is more uniform.

Description

Technical Field

[0001] This invention relates to the field of photocathode protection technology, specifically to a BiVO4 / CuInS2 composite film for photocathode protection, its preparation method, and its application. Background Technology

[0002] Metal corrosion is a global problem, posing a significant threat to public safety and health, and causing substantial economic losses. Common corrosion protection technologies include impressed current protection, sacrificial anodes, and coatings, which offer good protection but often come at the cost of environmental impact, power consumption, and the use of active metals (Al, Al-Zn alloys, etc.). Photoelectrochemical cathodic protection (PECCP) is a technology that converts solar energy into electrical energy for corrosion protection, and it has gained widespread attention due to its green, environmentally friendly, and sustainable advantages. The principle of this technology is that when the photoanode is irradiated by sunlight, electrons are excited from the valence band (VB) to the conduction band (CB), leaving holes in the VB. Subsequently, electrons are transferred to the metal, causing cathodic polarization, while holes participate in the oxidation of water or are captured by hole scavengers. In this process, the performance of PECCP is closely related to the photoelectric separation efficiency of the photoanode. Therefore, developing semiconductor materials with high photoelectric separation efficiency is key to promoting the development of PECCP technology.

[0003] Currently, semiconductor materials suitable for PECCP include TiO2, WO3, and ZnO, but these materials have large band gaps, making it difficult to utilize visible light. Furthermore, these materials suffer from insufficient oxidizing power, requiring the addition of hole traps for use, which limits their application in real-world environments. Monoclinic scheelite BiVO4 has attracted significant interest from researchers due to its narrow band gap (~2.4 eV) and high photostability. However, the high recombination rate of photogenerated electrons and holes limits its application in photocathode protection. Heterojunction engineering not only promotes charge separation through an internal field but also broadens the solar energy absorption range, attracting widespread attention. Type II heterojunctions are the most common type of heterojunction. Their band structure allows for effective separation of photogenerated carriers (electrons and holes) at the interface, enabling them to migrate separately into different materials and reducing electron-hole recombination. However, the carrier migration path in Type II heterojunctions is complex; improper design can easily lead to carrier recombination at the interface, reducing photoelectric separation efficiency. A literature review (T. Shi, Y. Liu, X. Niu, G. Yin, C. Ni, X. Han, W. Wang, Y. Duan, Q. Zong, S. Ren, Y. Du, F. Xiao, Novel ZnO / BiOI nanorod photoanode with interface pn heterojunction and excellent photoelectric conversion efficiency for photocathodic protection of stainless steel, Colloids and Surfaces A: Physicochemical and Engineering Aspects 676 (2023). https: / / doi.org / 10.1016 / j.colsurfa.2023.132124.) indicates that a photoanode composed of a pn heterojunction can generate an electric field at the pn heterojunction interface of a semiconductor. The pn heterojunction can promote the directional migration of photogenerated electrons and holes, reduce the recombination of photogenerated electrons and holes, and thus improve the photocatalytic activity and photoelectrochemical conversion efficiency of the material.CuInS2, a typical p-type semiconductor (with a band gap of 1.53 eV) (J. Tian, ​​Z. Chen, J. Jing, C. Feng, M. Sun, W. Li, Photoelectrochemical cathodic protection of Cu2O / TiO2 pn heterojunction under visible light, Journal of Oceanology and Limnology 38(5) (2020) 1517-1531. https: / / doi.org / 10.1007 / s00343-020-9327-y.), possesses both strong light absorption coefficient and low cost, showing great application potential in the field of photocatalytic degradation of organic pollutants. However, the photogenerated carrier recombination rate of CuInS2 is relatively fast, which significantly reduces the number of effective carriers participating in the photocatalytic reaction, thus exhibiting a low photoelectric conversion efficiency. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned defects and deficiencies in the prior art. By constructing a pn heterojunction with directional electron transport function, efficient protection of 304 SS can be achieved in the absence of hole trapping agents and in both bright and dark states.

[0005] The second objective of this invention is to provide a method for preparing a pn heterojunction thin film for photocathode protection and its application, thereby addressing the problem of poor corrosion resistance in current photoanode materials used for photocathode protection. This invention involves electroplating BiVO4 onto a conductive glass surface and then introducing CuInS2 via a hydrothermal method to construct a pn heterojunction. The resulting BiVO4 / CuInS2 composite thin film promotes the consumption of photogenerated holes, improving photoelectric conversion efficiency. The coupling potential between this composite film and 304SS undergoes cathodic polarization under illumination, providing ample protection for the metal and exhibiting long-term stable photochemical cathodic protection performance in seawater environments.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a BiVO4 / CuInS2 composite film for photocathode protection includes the following steps: (1) Clean the conductive glass; (2) A BiVO4 thin film is grown on the conductive glass obtained in step (1) by electroplating. (3) The composite film for photocathode protection can be obtained by in-situ growth of CuInS2 on the surface of the BiVO4 thin film.

[0007] In step (1), the cleaning includes placing the conductive glass in a first solution and a second solution for ultrasonic cleaning; the first solution is ethanol or acetone, and the second solution is deionized water; the time for each ultrasonic cleaning is 10~30 minutes.

[0008] The conductive glass is either FTO conductive glass or ITO conductive glass.

[0009] Step (2) includes the following steps: (1) Dissolve Bi(NO3)3∙5H2O and KI in deionized water, and adjust the pH to 1.75 with concentrated HNO3 to obtain solution A; (2) Dissolve p-benzoquinone in ethanol to obtain solution B; (3) Mix solutions A and B as electrolytes and stir magnetically for 5-15 minutes; (4) A three-electrode system is formed by a Pt sheet (counter electrode, CE), a saturated calomel electrode (SCE, reference electrode, RE) and an FTO (working electrode, WE); BiOI thin film is obtained by electrodeposition at −0.147 V for 3-8 min. (5) A dimethyl sulfoxide (DMSO) solution containing VO(acac)2 is dropped onto the BiOI film and kept at 550-600 °C for 1-3 h. Then it is soaked in NaOH solution for 0.5 h and rinsed with deionized water to obtain the BiVO4 film.

[0010] The composition of the solution includes: Bi(NO3)3∙5H2O to KI in a mass ratio of 1:3-4; Bi(NO3)3∙5H2O to deionized water in a mass-to-volume ratio of 1:45-55 g / ml; Bi(NO3)3∙5H2O to p-benzoquinone in a mass ratio of 1.8-2.2:1; p-benzoquinone to ethanol in a mass-to-volume ratio of 0.02-0.03 g / ml; VO(acac)2 in a dimethyl sulfoxide (DMSO) solution in a molar concentration of 0.1-0.3 mol / L; Bi(NO3)3∙5H2O to VO(acac)2 in a dimethyl sulfoxide (DMSO) solution in a mass-to-volume ratio of 50-60 g / ml; and NaOH solution in a molar concentration of 0.5-1.5 mol / L.

[0011] Step (3) includes the following steps: a mixed solution of copper chloride, indium chloride and thioacetamide is used to perform a hydrothermal reaction at 150-200℃ for 8-12 hours. After the reaction vessel is cooled, the solution is obtained. It is then washed 3 times with water and 3 times with ethanol by centrifugation and dried at 80-100℃ for 8-12 hours to obtain a BiVO4 / CuInS2 thin film for photocathode protection.

[0012] In the mixed solution of copper chloride, indium chloride, and thioacetamide, the concentration of copper chloride is 1-5 mg / ml, the concentration of indium chloride is 8-15 mg / ml, and the concentration of thioacetamide is 5-10 mg / ml.

[0013] The present invention also provides a BiVO4 / CuInS2 composite film for photocathode protection, which is prepared by the above-described preparation method.

[0014] The above-mentioned BiVO4 / CuInS2 composite film for photoelectric cathodic protection is used in photoelectrochemical cathodic protection.

[0015] This invention proposes a hydrothermal technique to grow CuInS2 on BiVO4 with a nanostructure, resulting in a BiVO4 / CuInS2 thin film exhibiting pn-type heterojunction characteristics. When BiVO4 and CuInS2 come into contact, a built-in electric field is formed that facilitates the directional separation of photogenerated carriers. Specifically, photogenerated electrons move towards the n-type semiconductor region (BiVO4) under the influence of the built-in electric field, while photogenerated holes move towards the p-type semiconductor region (CuInS2), thereby reducing interfacial recombination between electrons and holes.

[0016] This invention solves the aforementioned problems through a pn heterojunction construction strategy using electroplating and hydrothermal methods. First, compared to other methods, electroplating is easier to control and scale up. Second, the BiVO4 nanostructure provides more active sites and exhibits a certain energy storage effect. Third, the formation of the pn heterojunction guides electrons to accumulate in the n-type (BiVO4) while holes remain in the p-type (CuInS2). The directional transport function of the pn heterojunction further extends the charge separation time, facilitating the rapid transfer of photogenerated charges, thereby significantly improving the photoelectrochemical cathodic protection performance of the heterojunction system. Fourth, the photoanode performance exhibits high stability, enabling stable protection of 304 SS under both light and dark conditions.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention addresses the limitation of heterogeneous structure construction strategies in simultaneously possessing both high stability and ease of use. It solves this problem by constructing a pn heterogeneous strategy in two steps.

[0018] First, compared to other methods such as drop coating and spin coating, it is easier to control, easier to mass-produce, and produces a more uniform film.

[0019] Second, the formation of the pn heterojunction guides electrons to accumulate in the n-type (BiVO4) while holes remain in the p-type (CuInS2), which further prolongs the charge separation time and helps the rapid transfer of photogenerated charges, thereby greatly improving the photoelectrochemical cathodic protection performance of the heterojunction system.

[0020] Third, the film exhibits stable performance and demonstrates long-lasting and stable photoelectrochemical cathodic protection for 304 SS in a seawater environment. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 The images show scanning electron microscope (SEM) images of the composite thin films (a is BiVO4, b is BiVO4 / CuInS2). Figure 2 XRD pattern of the composite thin film Figure 3 The graph shows the photoinduced open-circuit short-term potential variation of BiVO4 and BiVO4 / CuInS2 composite films in the presence of intermittent light. Figure 4 The image shows the UV-vis images of BiVO4 and BiVO4 / CuInS2 composite films. Detailed Implementation

[0023] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1 This embodiment provides a method for preparing a BiVO4 / CuInS2 composite film for photocathode protection, including the following steps: (1) The FTO conductive glass was ultrasonically cleaned in ethanol and deionized water respectively; the ultrasonic cleaning time was 20 min each time.

[0025] (2) A BiVO4 thin film is grown on the conductive glass obtained in step (1) by electroplating, including the following steps: a. Dissolve 0.97 g Bi(NO3)3∙5 H2O and 3.32 g KI in 50 ml of deionized water, and adjust the pH to 1.75 with concentrated HNO3 to obtain solution A.

[0026] b. Dissolve 0.49 g of p-benzoquinone in 20 ml of ethanol to obtain solution B.

[0027] c. Mix solutions A and B as electrolytes and stir magnetically for 10 min.

[0028] A three-electrode system was constructed using a Pt sheet (counter electrode, CE), a saturated calomel electrode (SCE, reference electrode, RE), and an FTO (working electrode, WE). A BiOI thin film was obtained by electrodeposition at −0.147 V for 5 min.

[0029] e. Add 0.2 ml of dimethyl sulfoxide (DMSO) solution containing 0.2 M VO(acac)2 to BiOI, keep at 550 °C for 2 h, then soak in 1 M NaOH for 0.5 h, and rinse with deionized water to obtain BiVO4 membrane.

[0030] (3) CuInS2 is grown in situ on the surface of the BiVO4 film, specifically including the following steps: a mixed solution of copper chloride, indium chloride and thioacetamide is used, wherein the molar concentration of copper chloride is 1 mg / ml, the molar concentration of indium chloride is 15 mg / ml and the molar concentration of thioacetamide is 5 mg / ml. The mixture is hydrothermally reacted at 180°C for 10 hours. After the reaction vessel is cooled, the solution is obtained. The solution is washed three times with water and three times with ethanol by centrifugation and dried at 90°C for 10 hours to obtain the BiVO4 / CuInS2 film for photocathode protection.

[0031] Example 2 This embodiment provides a method for preparing a BiVO4 / CuInS2 composite film for photocathode protection, including the following steps: (1) The ITO conductive glass was ultrasonically cleaned in acetone and deionized water respectively; the ultrasonic cleaning time was 10 min each time.

[0032] (2) A BiVO4 thin film is grown on the conductive glass obtained in step (1) by electroplating, including the following steps: a. Dissolve 1.00 g Bi(NO3)3∙5 H2O and 3.00 g KI in 50 ml of deionized water, and adjust the pH to 1.75 with concentrated HNO3 to obtain solution A.

[0033] b. Dissolve 0.56 g of p-benzoquinone in 27.8 ml of ethanol to obtain solution B.

[0034] c. Mix solutions A and B as electrolytes and stir magnetically for 10 min.

[0035] A three-electrode system was constructed using a Pt sheet (counter electrode, CE), a saturated calomel electrode (SCE, reference electrode, RE), and an FTO (working electrode, WE). A BiOI thin film was obtained by electrodeposition at −0.147 V for 5 min.

[0036] e. Add 0.2 ml of dimethyl sulfoxide (DMSO) solution containing 0.1 M VO(acac)2 to BiOI, keep at 550 °C for 2 h, then soak in 0.5 M NaOH for 0.5 h, and rinse with deionized water to obtain BiVO4 membrane.

[0037] (3) CuInS2 is grown in situ on the surface of the BiVO4 film, specifically including the following steps: a mixed solution of copper chloride, indium chloride and thioacetamide is used, wherein the molar concentration of copper chloride in the mixed solution is 3.3 mg / ml, the molar concentration of indium chloride is 11 mg / ml, and the molar concentration of thioacetamide is 7.5 mg / ml. The solution is hydrothermally reacted at 150°C for 12 hours. After the reaction vessel is cooled, the solution is washed 3 times with water and 3 times with ethanol by centrifugation and dried at 100°C for 8 hours to obtain the BiVO4 / CuInS2 film for photocathode protection.

[0038] Example 3 This embodiment provides a method for preparing a BiVO4 / CuInS2 composite film for photocathode protection, which includes the following steps: (1) The FTO conductive glass was ultrasonically cleaned in ethanol and deionized water respectively; the ultrasonic cleaning time was 10~30 min each time.

[0039] (2) A BiVO4 thin film is grown on the conductive glass obtained in step (1) by electroplating, including the following steps: a. Dissolve 1.20 g Bi(NO3)3∙5 H2O and 4.8 g KI in 66 ml of deionized water, and adjust the pH to 1.75 with concentrated HNO3 to obtain solution A.

[0040] b. Dissolve 0.55 g of p-benzoquinone in 18 ml of ethanol to obtain solution B.

[0041] c. Mix solutions A and B as electrolytes and stir magnetically for 10 min.

[0042] A three-electrode system was constructed using a Pt sheet (counter electrode, CE), a saturated calomel electrode (SCE, reference electrode, RE), and an FTO (working electrode, WE). A BiOI thin film was obtained by electrodeposition at −0.147 V for 5 min.

[0043] e. Add 0.2 ml of dimethyl sulfoxide (DMSO) solution containing 0.3 M VO(acac)2 dropwise onto BiOI, keep at 550 °C for 2 h, then soak in 1.5 M NaOH for 0.5 h, and rinse with deionized water to obtain BiVO4 membrane.

[0044] (3) CuInS2 is grown in situ on the surface of the BiVO4 film, specifically including the following steps: a mixed solution of copper chloride, indium chloride and thioacetamide is used, wherein the molar concentration of copper chloride is 5 mg / ml, the molar concentration of indium chloride is 8 mg / ml, and the molar concentration of thioacetamide is 10 mg / ml. The mixture is hydrothermally reacted at 200°C for 8 hours. After the reaction vessel is cooled, the solution is obtained. The solution is washed 3 times with water and 3 times with ethanol by centrifugation and dried at 100°C for 8 hours to obtain the BiVO4 / CuInS2 film for photocathode protection.

[0045] Experimental Example 1: The microstructure of BiVO4 and BiVO4 / CuInS2 composite films was observed using a scanning electron microscope (ZEISS Sigma 360, Germany).

[0046] like Figure 1 As shown in (a), BiVO4 consists of a compact structure formed by irregularly shaped nanosheets. Figure 1 As shown in (b), BiVO4 / CuInS2 forms a porous structure from irregular sheet-like structures, with some areas clustered into nanospheres, which is beneficial for increasing the specific surface area of ​​the material and facilitating light absorption.

[0047] Experimental Example 2: The phase composition of BiVO4 and BiVO4 / CuInS2 composite films was tested by X-ray diffraction using a BRUCKER D8 ADVANCE instrument.

[0048] The target used in the test was a Cu target, the test angle range was 10-80°, and a grazing firing test mode was adopted. Figure 2 The XRD pattern shows that the peaks of the BiVO4 thin film correspond well to the standard card of BiVO4, proving that BiVO4 is present in the prepared material. Among them, the diffraction peaks at 18.78° and 28.73° in the figure correspond to the (101) and (112) crystal planes of cubic BiVO4 (JCPDS 48–0744).

[0049] The peaks at 27.9° and 46.4° of the BiVO4 / CuInS2 composite film correspond to the (112) and (204) crystal planes of the chalcopyrite phase (JCPDS27-0159) in CuInS2, respectively. The diffraction peak at 28.73° corresponds to the (112) crystal plane of cubic BiVO4 (JCPDS 48–0744), indicating that the BiVO4 / CuInS2 composite film was successfully prepared.

[0050] Experimental Example 3: Evaluation of the photoelectrochemical cathodic protection effect of BiVO4 / and BiVO4 / CuInS2 composite thin films Electrochemical tests were conducted on the BiVO4 / CuInS2 composite thin film using an electrochemical workstation (model KOSTER CS350M). A three-electrode method was employed, with a platinum sheet as the counter electrode, Ag / AgCl as the reference electrode, and 304 SS coupled to the BiVO4 / CuInS2 composite thin film as the working electrode. The photoinduced open-circuit potential change was measured by intermittent light irradiation to indicate the material's photoelectrochemical cathodic protection performance. The corrosion cell used a 3.5 wt% NaCl solution, and the photoanode cell used a 3.5 wt% NaCl solution without hole trapping technology. The intermittent light frequency was 50 s on and 50 s off; the light source system used was a PLS-SXE300E to simulate sunlight irradiation.

[0051] like Figure 3 As shown, under intermittent light irradiation, the CuInS2 film polarizes the potential of 304 SS to -0.04 (V vs Ag / AgCl), exhibiting the characteristics of a p-type semiconductor. The BiVO4 film can polarize the potential of 304 SS to -0.35 (V vs Ag / AgCl), compared to the self-corrosion potential of 304 SS of -0.16 (V vs Ag / AgCl). The BiVO4 / CuInS2 composite film can polarize the potential of 304 SS to -0.43 (V vs Ag / AgCl), compared to the self-corrosion potential of 304 SS of -0.16 (V vs Ag / AgCl), and is more stable, thus achieving stable protection of 304 SS under both light and dark conditions.

[0052] The BiVO4 / CuInS2 composite film provides approximately 270 mV of photoelectrochemical cathodic protection for 304 SS under illumination. The formation of the pn heterojunction guides electrons to accumulate in the n-type (BiVO4) while holes remain in the p-type (CuInS2), which further prolongs the charge separation time and facilitates the rapid transfer of photogenerated charges, thereby greatly improving the photoelectrochemical cathodic protection performance of the heterojunction system.

[0053] As can be seen, this invention obtains a BiVO4 / CuInS2 composite film for photocathode protection via electroplating and hydrothermal methods. This composite film delays the irradiation recombination of electrons and holes, promotes the consumption of photogenerated holes, and significantly improves the photoelectric conversion efficiency. The BiVO4 / CuInS2 composite film exhibits stable protection against 304 SS in a seawater environment (a decrease of 270 mV compared to 304 SS). The method for obtaining the film is simple and readily available, and when applied to a photocathode protection system in a seawater environment, its photoelectric performance remains stable over a long period, laying the foundation for future industrialization.

[0054] Experimental Example 4: The optical properties of BiVO4 and BiVO4 / CuInS2 were tested using UV-Vis spectroscopy to investigate the effect of pn heterojunction type on optical absorption. Simultaneously, according to formula (E... g =1240 / λ g The band gaps of BiVO4 and BiVO4 / CuInS2 were calculated.

[0055] like Figure 4 As shown, the maximum photoresponse wavelength of BiVO4 / CuInS2 is significantly higher than that of BiVO4. This phenomenon indicates that BiVO4 / CuInS2 has a wider light absorption range, which helps to improve the utilization efficiency of sunlight.

[0056] In summary, the experimental results of Examples 1-4 all demonstrate that the BiVO4 / CuInS2 composite film for photocathode protection of the present invention can provide photocathode protection current for marine steel, thus extending its service life in marine engineering.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a BiVO4 / CuInS2 composite film for photocathode protection, characterized in that... Includes the following steps: (1) Clean the conductive glass; (2) A BiVO4 thin film is grown on the conductive glass obtained in step (1) by electroplating. (3) The composite film for photocathode protection can be obtained by in-situ growth of CuInS2 on the surface of the BiVO4 thin film.

2. The method for preparing a BiVO4 / CuInS2 composite film for photocathode protection according to claim 1, characterized in that: In step (1), the cleaning includes ultrasonic cleaning of the conductive glass in a first solution and a second solution respectively; the first solution is ethanol or acetone, and the second solution is deionized water; the time for each ultrasonic cleaning is 10~30 minutes.

3. The method for preparing a BiVO4 / CuInS2 composite film for photocathode protection according to claim 1, characterized in that: The conductive glass is either FTO conductive glass or ITO conductive glass.

4. The method for preparing a BiVO4 / CuInS2 composite film for photocathode protection according to claim 1, characterized in that... Step (2) includes the following steps: (1) Dissolve Bi(NO3)3∙5H2O and KI in deionized water, and adjust the pH to 1.75 with concentrated HNO3 to obtain solution A; (2) Dissolve p-benzoquinone in ethanol to obtain solution B; (3) Mix solutions A and B as electrolytes and stir magnetically for 5-15 minutes; (4) A three-electrode system consisting of a Pt sheet, a saturated calomel electrode, and FTO was formed; BiOI thin films were obtained by electrodeposition at −0.147 V for 3–8 min. (5) A dimethyl sulfoxide (DMSO) solution containing VO(acac)2 is dropped onto the BiOI film and kept at 550-600 °C for 1-3 h. Then it is soaked in NaOH solution for 0.5 h and rinsed with deionized water to obtain the BiVO4 film.

5. The method for preparing a BiVO4 / CuInS2 composite film for photocathode protection according to claim 4, characterized in that: The mass ratio of Bi(NO3)3∙5H2O to KI is 1:3-4; the mass-volume ratio of Bi(NO3)3∙5H2O to deionized water is 1:45-55 g / ml; the mass ratio of Bi(NO3)3∙5H2O to p-benzoquinone is 1.8-2.2:1; the mass-volume ratio of p-benzoquinone to ethanol is 0.02-0.03 g / ml; the molar concentration of VO(acac)2 in the dimethyl sulfoxide (DMSO) solution is 0.1-0.3 mol / L; the mass-volume ratio of Bi(NO3)3∙5H2O to the dimethyl sulfoxide (DMSO) solution of VO(acac)2 is 50-60 g / ml; and the molar concentration of NaOH solution is 0.5-1.5 mol / L.

6. The method for preparing a BiVO4 / CuInS2 composite film for photocathode protection according to claim 1, characterized in that... Step (3) includes the following steps: a mixed solution of copper chloride, indium chloride and thioacetamide is used to perform a hydrothermal reaction at 150-200℃ for 8-12 hours. After the reaction vessel is cooled, the solution is obtained. It is then washed 3 times with water and 3 times with ethanol by centrifugation and dried at 80-100℃ for 8-12 hours to obtain the BiVO4 / CuInS2 thin film for photocathode protection.

7. The method for preparing a BiVO4 / CuInS2 composite film for photocathode protection according to claim 6, characterized in that: The concentration of copper chloride in the mixed solution of copper chloride, indium chloride and thioacetamide is 1-5 mg / ml, the concentration of indium chloride is 8-15 mg / ml, and the concentration of thioacetamide is 5-10 mg / ml.

8. A BiVO4 / CuInS2 composite film for photocathode protection, which is prepared by the preparation method according to any one of claims 1-7.

9. The application of the BiVO4 / CuInS2 composite film for photoelectric cathodic protection as described in claim 8 in photoelectrochemical cathodic protection.

Images