WO3-ZIFs-AgInS2 composite film for photoelectric cathode protection as well as preparation method and application of WO3-ZIFs-AgInS2 composite film

Abstract

The invention discloses a WO3-ZIFs-AgInS2 composite film for photoelectric cathode protection and a preparation method and application thereof, and belongs to the technical field of photoelectric cathode protection. WO3 is grown on the surface of conductive glass in situ, ZIFs is introduced through an electro-deposition technology, and a WO3-ZIFs film with the hydrophobic and energy storage dual functions is successfully obtained; and finally, the coupling potential of the WO3-ZIFs-AgInS2 composite film obtained by an in-situ synthesis method and 304SS is subjected to cathodic polarization during illumination, sufficient protection is provided for metal, so that the metal shows long-acting and stable photoelectrochemical cathodic protection performance in a seawater environment, and in-situ protection can be realized without adding a hole trapping agent. The preparation method of the film has the advantages of simplicity, high efficiency, easiness in large-scale production and the like, and the prepared photo-anode has relatively high stability and corrosion protection efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of photoelectrochemical cathodic protection, and particularly relates to a WO3-ZIFs-AgInS2 composite film, a preparation method thereof and an application thereof. Background Art

[0002] Corrosion not only causes huge economic losses and serious environmental pollution, but also leads to catastrophic accidents that cause personal injuries. At present, metal anti-corrosion technologies mainly include two categories: physical barrier protection and electrochemical protection. Cathodic protection technology has been widely used in the anti-corrosion of marine infrastructure due to its advantages such as directness, thoroughness, and durability. Impressed current cathodic protection requires a stable power source and relatively complex maintenance equipment, which limits its use under marine conditions and also consumes a large amount of energy during operation. Sacrificial anode cathodic protection methods require different sacrificial anodes for different structural sizes and service lives. However, the production of sacrificial anodes consumes a large amount of energy and the dissolution of anodes in seawater will also pollute the ocean. Therefore, it is urgent to develop a new type of metal protection technology that is green, energy-saving, and environmentally friendly.

[0003] As a new type of anti-corrosion technology, photoelectrochemical cathodic protection has been widely concerned and studied due to its advantages such as environmental protection and energy saving. Its principle is to use solar energy to excite semiconductor materials to generate electrons, which are then transferred to the coupled metal materials to provide cathodic protection. Researchers have used a variety of n-type semiconductor materials in the field of photoelectrochemical cathodic protection, such as TiO2, ZnO, SrTiO3, g-C3N4, etc. At the same time, based on the above materials, a series of material modification measures have been developed, such as morphology control, heterojunction engineering, cooperative hermetic assembly, etc. However, semiconductor materials can only generate photo-generated electrons under light illumination, and the cathodic protection of metals will terminate with the stop of light illumination, which will limit its practical application.

[0004] Tungsten trioxide (WO3) is a transition metal oxide with tungsten in multiple valence states. Due to its excellent electron storage performance, it has been proven to be the best choice for electron storage. However, the conduction band potential of single WO3 semiconductor is relatively positive, which has disadvantages such as low separation efficiency of photoelectrons and holes and inability to charge itself. To improve the photogenerated CP performance and electron storage performance of WO3, WO3 is compounded with other semiconductor materials to construct a series of WO3-based heterojunction photoanodes, such as WO3 / ZnO, WO3 / ZnIn2S4, etc. AgInS2 has characteristics such as low toxicity, a negative CB potential of -1.08 eV, a narrow bandgap of 1.8 eV, and a large absorption coefficient in the visible light region, and is widely used in photoelectrochemical cathodic protection. Constructing heterojunctions is regarded as an effective measure to improve the photoelectric separation efficiency of semiconductors. However, binary heterojunctions generally have problems of band mismatch and poor photoelectric separation efficiency. ZIFs materials have received extensive attention in the field of photoelectrochemical cathodic protection due to their high specific surface area, easy-to-adjust structure, and wide light absorption range. Therefore, in order to achieve effective protection of metals under dark conditions, in this work, ZIFs are used as an intermediate buffer layer to construct a WO3-ZIFs-AgInS2 energy storage photoanode with band matching. Summary of the Invention

[0005] The first object of the present invention is to provide a method for constructing a WO3-ZIFs-AgInS2 energy storage photoanode with high energy storage function, which is used to solve the problems of low energy storage efficiency and poor stability in existing photoelectrochemical cathodic protection technologies. WO3-ZIFs-AgInS2 has good band matching, and the constructed heterostructure promotes the effective separation of photogenerated electrons and holes, thus achieving a high energy storage efficiency. At the same time, by regulating the type of ZIFs, a multi-component heterojunction with directional electron transport function is constructed to achieve efficient protection of 304SS under the conditions of no hole scavenger, in the light state and the dark state.

[0006] The second object of the present invention is to provide a simple and controllable in-situ preparation method for an energy storage photoanode, which is used to solve the problems of cumbersome preparation process and low efficiency of the current photoanode preparation technology. In the present invention, WO3 is in-situ grown on the surface of conductive glass, and ZIFs are introduced by electrodeposition technology to successfully obtain a WO3-ZIFs film with both hydrophobic and energy storage functions. Finally, a WO3-ZIFs-AgInS2 composite film is obtained by an in-situ synthesis method. The coupling potential of the WO3-ZIFs-AgInS2 composite film and 304SS undergoes cathodic polarization under illumination, providing sufficient protection for the metal and enabling it to exhibit long-term stable photoelectrochemical cathodic protection performance in a seawater environment. Without the addition of a hole scavenger, in-situ protection can be achieved. The preparation method of this film has the advantages of simplicity, high efficiency, and easy large-scale production, and the prepared photoanode has high stability and corrosion protection efficiency.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A preparation method of a WO3-ZIFs-AgInS2 composite film for optoelectronic cathodic protection, comprising the following steps:

[0009] (1) Clean the conductive glass;

[0010] (2) Grow a WO3 thin film on the conductive glass obtained by the treatment in step (1) by a hydrothermal method;

[0011] (3) Obtain a WO3-ZIFs composite thin film on the surface of the WO3 thin film by an electrodeposition method;

[0012] (4) Obtain a WO3-ZIFs-AgInS2 composite film by in-situ growth, which is the composite film for optoelectronic cathodic protection.

[0013] Among them, in step (1), the cleaning includes ultrasonically cleaning 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 min.

[0014] Among them, the conductive glass is FTO conductive glass or ITO conductive glass.

[0015] Among them, step (2) is specifically: dissolve sodium tungstate in water or absolute ethanol, then add concentrated sulfuric acid to make a mixed solution, and then place the cleaned conductive glass in the above mixed solution, react at 70-100 °C for 7-9 h, and then transfer it to a muffle furnace and heat up to 400-600 °C, calcine for 1-3 h to obtain a WO3 thin film.

[0016] Among them, the mass-volume ratio of sodium tungstate to water or absolute ethanol is 1:(100-150) g / ml, and the mass-volume ratio of sodium tungstate to concentrated sulfuric acid is 1:(0.8-1.2) g / ml.

[0017] Among them, step (3) is specifically as follows: Use the FTO glass covered with WO3 as the working electrode, Pt and saturated calomel as the counter electrode and reference electrode respectively; Use 50 ml of 0.15 M Co(NO3)2·6H2O solution as the electrolyte, and at a voltage of -1.0 V (vs SCE) for 200 s to prepare Co(OH)2 on the surface of WO3; The FTO glass prepared with Co(OH)2 is immersed in 1 M 2-methylimidazole solution, 1 M benzimidazole solution, and 1 M 5-chlorobenzimidazole solution for 10 - 15 h respectively to obtain ZIF67-A, ZIF67-B, and ZIF67-C respectively, and then vacuum-dry at 60 - 90 °C for 0.5 - 1.5 h to obtain WO3-ZIF67-A, WO3-ZIF67-B, and WO3-ZIF67-C.

[0018] Among them, step (4) is specifically as follows: Use a mixed solution of silver nitrate, indium nitrate, and thioacetamide. Place the FTO conductive glass with the WO3-ZIFs composite film deposited on its surface face down and carry out hydrothermal reaction at 150 - 200 °C for 8 - 12 hours. After the reaction kettle cools, remove the solution and dry at 80 - 100 °C for 0 - 1 h to prepare the WO3-ZIFs-AgInS2 composite film for photoelectrochemical cathodic protection.

[0019] Among them, in the mixed solution of silver nitrate, indium nitrate, and thioacetamide, the contents of silver nitrate, indium nitrate, and thioacetamide are 0.15 - 0.25 g, 0.6 - 0.7 g, and 0.4 - 0.5 g respectively.

[0020] A WO3-ZIFs-AgInS2 composite film for photoelectrochemical cathodic protection is made by the above preparation method.

[0021] The application of the above WO3-ZIFs-AgInS2 composite film in photoelectrochemical cathodic protection.

[0022] The WO3-ZIFs-AgInS2 composite film in the present invention has the following advantages:

[0023] 1) The large specific surface area and porosity of ZIFs can provide more active sites and improve the light utilization efficiency of the composite photoanode;

[0024] 2) The good energy band matching of WO3-ZIFs-AgInS2 is conducive to promoting the separation of photogenerated electrons and holes;

[0025] 3) By regulating the ligand type of ZIFs, the hydrophobicity of the WO3-ZIFs photoanode can be effectively regulated;

[0026] 4) The WO3-ZIFs-AgInS2 heterojunction thin film can achieve the function of directional electron transport, which helps to achieve effective charge separation and transport, reduce charge recombination, and thus improve the photocatalytic activity.

[0027] 5) WO3-ZIFs-AgInS2 shows excellent protective performance against 304SS and can achieve stable protection in both light and dark states.

[0028] In addition, the heterostructure construction strategy of the present invention cannot simultaneously possess the two advantages of high stability and simple method. The above problems are solved by a three-step heterostructure construction strategy. First, compared with other methods such as drop coating and spin coating, it is easier to control, easier for large-scale production, and the prepared film is more uniform. Second, the WO3-ZIF67-AgInS2 composite film has a directional electron transport function, which can effectively improve the recombination of holes and electrons. Third, the film has stable performance and can show long-term stable photoelectrochemical cathodic protection performance for 304SS in a seawater environment. The present invention also provides a composite film for photoelectrochemical cathodic protection, which adopts the following technical solution: The composite film for photoelectrochemical cathodic protection is prepared by using the above-mentioned preparation method.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The present invention constructs a WO3-ZIFs-AgInS2 energy storage photoanode with band matching. By changing the ligand type and constructing a synergistic heterostructure strategy, the problems existing in the WO3-based photoanode, such as low dark-state energy storage efficiency, high electron and hole recombination rates, and weak photoanode stability, are solved, and stable protection of 304SS in light / dark states is achieved. It should be noted that the composite photoanode prepared by the present invention can achieve stable light / dark-state photoelectrochemical cathodic protection of 304SS in a seawater environment without a hole scavenger.

[0031] 2. The present invention has the characteristics of simplicity, high efficiency, and low cost. The prepared WO3-ZIFs-AgInS2 energy storage photoanode has advantages such as a high specific surface area and high dark-state energy storage efficiency. The multi-component heterojunction with a good energy band gradient can enable photo-generated electrons to be transported directionally along the energy band, and due to the synergistic effect between different semiconductors, a large number of photo-induced electrons are generated, thus greatly improving the photoelectrochemical cathodic protection performance of the heterojunction system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The specification drawings constituting a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0033] Figure 1SEM images of WO3-ZIF67-A-AgInS2 thin films (a is the front side, b is the cross-section);

[0034] Figure 2 Hydrophobicity performance diagram of WO3-ZIFs;

[0035] Figure 3 XRD of WO3-ZIF67-A-AgInS2 composite thin film;

[0036] Figure 4 UV-vis diagram of WO3-ZIF67-A-AgInS2 composite thin film;

[0037] Figure 5 Open circuit potential diagram of WO3-ZIFs-AgInS2 composite thin film in the absence of a hole scavenger and intermittent light. Detailed implementation manners

[0038] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0039] Example 1

[0040] This example provides a preparation method of a WO3-ZIFs-AgInS2 composite film for photocathodic protection, including the following steps:

[0041] (1) Clean the FTO conductive glass; the cleaning includes ultrasonically cleaning the FTO conductive glass in ethanol and deionized water respectively; the time of each ultrasonic cleaning is 20 min;

[0042] (2) Grow a WO3 thin film on the conductive glass obtained by step (1) through a hydrothermal method; specifically: dissolve sodium tungstate in water or absolute ethanol, then add concentrated sulfuric acid to make a mixed solution, and then place the cleaned conductive glass in the above mixed solution, react at 85 °C for 8 h, and then transfer it to a muffle furnace and heat up to 500 °C and calcine for 2 h to obtain a WO3 thin film; the mass-volume ratio of sodium tungstate to water or absolute ethanol is 1:120 g / ml, and the mass-volume ratio of sodium tungstate to concentrated sulfuric acid is 1:1 g / ml;

[0043] (3) A WO3-ZIFs composite film is obtained by electrodeposition on the surface of the WO3 film. Specifically: The FTO glass covered with WO3 is used as the working electrode, and Pt and saturated calomel are used as the counter electrode and reference electrode respectively; Using 50 ml of 0.15 M Co(NO3)2·6H2O solution as the electrolyte, at a voltage of -1.0 V (vs SCE) for 200 s, Co(OH)2 is prepared on the WO3 surface; The FTO glass prepared with Co(OH)2 is immersed in 1 M 2-methylimidazole solution, 1 M benzimidazole solution, and 1 M 5-chlorobenzimidazole solution for 12 h respectively to obtain ZIF67-A, ZIF67-B, and ZIF67-C. Subsequently, it is vacuum dried at 80 °C for 1 h to obtain WO3-ZIF67-A, WO3-ZIF67-B, and WO3-ZIF67-C;

[0044] (4) The WO3-ZIFs-AgInS2 composite film obtained by in-situ growth is the composite film for photoelectrochemical cathodic protection. Specifically: Using a mixed solution of 60 ml of silver nitrate, indium nitrate, and thioacetamide, the conductive surface of the FTO conductive glass with a WO3-ZIFs composite film deposited on its surface is placed face down and hydrothermally reacted at 150 - 200 °C for 8 - 12 hours. After the reaction kettle cools down, the solution is removed and dried at 80 - 100 °C for 0 - 1 h to prepare the WO3-ZIFs-AgInS2 composite film for photoelectrochemical cathodic protection. Among them, the contents of silver nitrate, indium nitrate, and thioacetamide in the mixed solution of silver nitrate, indium nitrate, and thioacetamide are 0.2 g, 0.66 g, and 0.45 g respectively.

[0045] Example 2

[0046] This example provides a method for preparing a WO3-ZIFs-AgInS2 composite film for photoelectrochemical cathodic protection, including the following steps:

[0047] (1) Clean the FTO conductive glass; The cleaning includes ultrasonically cleaning the FTO conductive glass in acetone and deionized water respectively; The time for each ultrasonic cleaning is 10 min;

[0048] (2) Grow a WO3 film on the conductive glass obtained by step (1) through hydrothermal method. Specifically: Dissolve sodium tungstate in water or absolute ethanol, then add concentrated sulfuric acid to make a mixed solution, and then place the cleaned conductive glass in the above mixed solution, react at 70 °C for 9 h, and then transfer it to a muffle furnace and heat up to 400 °C and calcine for 3 h to obtain a WO3 film; The mass-volume ratio of sodium tungstate to water or absolute ethanol is 1:100 g / ml, and the mass-volume ratio of sodium tungstate to concentrated sulfuric acid is 1:1.2 g / ml;

[0049] (3) A WO3-ZIFs composite film is obtained by electrodeposition on the surface of the WO3 film. Specifically: The FTO glass covered with WO3 serves as the working electrode, and Pt and saturated calomel electrodes serve as the counter electrode and reference electrode respectively; Using 50 ml of 0.15 M Co(NO3)2·6H2O solution as the electrolyte, at a voltage of -1.0 V (vs SCE) for 200 s, Co(OH)2 is prepared on the WO3 surface; The FTO glass prepared with Co(OH)2 is soaked in 1 M 2-methylimidazole solution, 1 M benzimidazole solution, and 1 M 5-chlorobenzimidazole solution for 10 h respectively to obtain ZIF67-A, ZIF67-B, and ZIF67-C respectively, and then dried in vacuum at 90 °C for 0.5 h to obtain WO3-ZIF67-A, WO3-ZIF67-B, and WO3-ZIF67-C;

[0050] (4) The WO3-ZIFs-AgInS2 composite film obtained by in-situ growth is the composite film for photo-cathode protection. Specifically: Using a mixed solution of 60 ml of silver nitrate, indium nitrate, and thioacetamide, the conductive side of the FTO conductive glass with a WO3-ZIFs composite film deposited on its surface is placed face down and hydrothermally reacted at 150 - 200 °C for 8 - 12 hours. After the reaction kettle cools down, the solution is removed and dried at 80 - 100 °C for 0 - 1 h to prepare the WO3-ZIFs-AgInS2 composite film for photo-cathode protection. Among them, the contents of silver nitrate, indium nitrate, and thioacetamide in the mixed solution of silver nitrate, indium nitrate, and thioacetamide are 0.25 g, 0.6 g, and 0.5 g respectively.

[0051] Example 3

[0052] This example provides a preparation method of a WO3-ZIFs-AgInS2 composite film for photo-cathode protection, including the following steps:

[0053] (1) Clean the ITO conductive glass; The cleaning includes ultrasonically cleaning the ITO conductive glass in ethanol and deionized water respectively; The time for each ultrasonic cleaning is 30 min;

[0054] (2) Grow a WO3 film on the conductive glass obtained by step (1) through hydrothermal method. Specifically: Dissolve sodium tungstate in water or absolute ethanol, then add concentrated sulfuric acid to make a mixed solution, and then place the cleaned conductive glass in the above mixed solution, react at 100 °C for 7 h, and then transfer it to a muffle furnace and heat up to 600 °C and calcine for 1 h to obtain a WO3 film; The mass-volume ratio of sodium tungstate to water or absolute ethanol is 1:150 g / ml, and the mass-volume ratio of sodium tungstate to concentrated sulfuric acid is 1:0.8 g / ml;

[0055] (3) The WO3-ZIFs composite film is obtained by electrodeposition on the surface of the WO3 film. Specifically, the FTO glass covered with WO3 is used as the working electrode, Pt and saturated calomel are used as the counter electrode and reference electrode respectively. Using 50 ml of 0.15 M Co(NO3)2·6H2O solution as the electrolyte, at a voltage of -1.0 V (vs SCE) for 200 s, Co(OH)2 is prepared on the surface of WO3. The FTO glass prepared with Co(OH)2 is immersed in 1 M 2-methylimidazole solution, 1 M benzimidazole solution, and 1 M 5-chlorobenzimidazole solution for 15 h respectively to obtain ZIF67-A, ZIF67-B, and ZIF67-C. Subsequently, it is vacuum dried at 60 °C for 1.5 h to obtain WO3-ZIF67-A, WO3-ZIF67-B, and WO3-ZIF67-C;

[0056] (4) The WO3-ZIFs-AgInS2 composite film obtained by in-situ growth is the composite film for photoelectrochemical cathodic protection. Specifically, a mixed solution of 60 ml of silver nitrate, indium nitrate, and thioacetamide is used. The conductive side of the FTO conductive glass with the WO3-ZIFs composite film deposited on its surface is placed face down and hydrothermally reacted at 150-200 °C for 8-12 hours. After the reaction kettle cools down, the solution is removed and dried at 80-100 °C for 0-1 h to prepare the WO3-ZIFs-AgInS2 composite film for photoelectrochemical cathodic protection. Among them, the contents of silver nitrate, indium nitrate, and thioacetamide in the mixed solution of silver nitrate, indium nitrate, and thioacetamide are 0.15 g, 0.70 g, and 0.4 g respectively.

[0057] Experimental Example 1

[0058] The microscopic morphology of the WO3-ZIF67-A-AgInS2 composite film was observed by scanning electron microscopy (model: ZEISS Sigma 300 from Germany).

[0059] As Figure 1 (a) shown, WO3-ZIF67-A-AgInS2 is composed of WO3 nanosheets, ZIF67 platelet-like structures, and AgInS2 nanoflower-like structures. Figure 1 (b) The cross-section of WO3-ZIF67-AgInS2 shows that WO3 is at the bottom layer, the middle layer is ZIF67, and the top layer is AgInS2, indicating the successful synthesis of WO3-ZIF67-A-AgInS2.

[0060] Experimental Example 2

[0061] The contact angle between the water droplet and the coating surface was measured with an optical contact angle meter, and its hydrophobicity was characterized. A 2 μL water droplet was dropped on the coating surface, and the static contact angle of the water droplet was measured after stabilization.

[0062] As Figure 2 shown, the contact angle of WO3 is 6.7°, the contact angle of WO3-ZIF67-A is 71.2°, the contact angle of WO3-ZIF67-B is 135°, and the contact angle of WO3-ZIF67-C is 143.3°, achieving effective regulation of the hydrophobic effect.

[0063] Experimental Example 3

[0064] The XRD test of the phase composition of the WO3-ZIF67-A-AgInS2 composite film was carried out by an X-ray diffractometer (model BRUCKER D8 ADVANCE).

[0065] The target used for the test was a Cu target, the test angle range was 10-80°, and the grazing test mode was adopted. As Figure 2 shown in the XRD pattern, the peaks of the WO3-ZIF67-A-AgInS2 composite film can well correspond to the standard card of WO3, proving the existence of tungsten oxide in the prepared material. Among them, the diffraction peaks appearing at 23.13, 23.63, 24.31, 26.45, 28.82, 34.08, 41.85, and 49.85 in the figure correspond to the (002), (020), (200), (120), (112), (202), (222), and (223) of cubic WO3 (JCPDS 83 0947). The diffraction peaks at 26.7°, 29.0°, 31.7°, 34.5°, and 36.9° belong to the AgInS2 phase. Due to the weak diffraction peak intensity of ZIF67, no obvious diffraction peak of ZIF67 was found.

[0066] Experimental Example 4

[0067] The optical properties of WO3-ZIF67-A-AgInS2 were tested by ultraviolet-visible spectroscopy to explore the influence of the ternary heterojunction on optical absorption.

[0068] As Figure 3 shown, the maximum light response wavelength of WO3-AgInS2 is 589nm, and the maximum light response wavelength of WO3-ZIF67-AgInS2 is basically in the range of 602nm. The above phenomena indicate that WO3-ZIF67-AgInS2 has a wider light absorption range, which helps to improve the utilization efficiency of sunlight.

[0069] Experimental Example 5

[0070] Test on the technical effect of the photoelectrochemical cathodic protection of the WO3-ZIFs-AgInS2 composite film

[0071] The WO3-ZIFs-AgInS2 composite film was electrochemically tested using an electrochemical workstation (model: Kost CS350M). The three-electrode method was adopted for the test, with a platinum sheet as the counter electrode, Ag / AgCl as the reference electrode, and the coupled 304SS and WO3-ZIFs-AgInS2 composite film as the working electrode. The change in the photoinduced open-circuit potential was tested by intermittent light irradiation to indicate the photoelectrochemical cathodic protection performance of the material. Among them, in a 3.5 wt% NaCl solution without a hole scavenger, the intermittent frequency of the intermittent light was 50 s of light on and 50 s of light off; the light source system used during the test was PLS-SXE300E to simulate sunlight irradiation.

[0072] As Figure 5 shown, in a 3.5 wt% NaCl solution without a hole scavenger and under intermittent light irradiation, the WO3-ZIF67-B-AgInS2 and WO3-ZIF67-C-AgInS2 films can polarize the potential of 304SS to -0.25 (V vs Ag / AgCl) and -0.2 (V vs Ag / AgCl) respectively, which can protect 304SS compared with the self-corrosion potential of 304SS, -0.16 (V vs Ag / AgCl). The WO3-ZIF67-A-AgInS2 composite film can polarize the potential of 304SS to -0.49 (V vs Ag / AgCl). Compared with the self-corrosion potential of 304SS, -0.16 (V vs Ag / AgCl), the WO3-ZIF67-A-AgInS2 composite film can provide a photoelectrochemical cathodic protection effect of about 330 mV for 304SS under light irradiation. This phenomenon is attributed to the fact that the WO3-ZIF67-A-AgInS2 heterojunction has a matched energy band structure and appropriate hydrophobicity, which can promote the effective separation of holes and electrons, and finally exhibit excellent light / dark state photoelectrochemical cathodic protection performance.

[0073] It can be seen that a series of WO3-ZIFs-AgInS2 composite films for photoelectrochemical cathodic protection were obtained by the hydrothermal method and electroplating method in the present invention. The composite film delays the radiative recombination of electrons and holes and significantly improves the photoelectric conversion efficiency. The protection effect on 304SS is relatively poor after the WO3-ZIF67-B and WO3-ZIF67-C composites with relatively excellent hydrophobic properties are combined with AgInS2. Therefore, the WO3-ZIF67-A-AgInS2 film with a matched energy band and appropriate hydrophobicity can achieve stable light / dark state protection of 304SS in a seawater environment. The method for obtaining the film is simple, easy to obtain, and low in cost, and is more in line with the actual marine application environment (avoiding the disadvantages of adding hole scavengers), laying a foundation for the large-scale production and application of this type of material.

[0074] In summary, the above experimental results all demonstrate that the AgInS2 composite film for optoelectronic cathodic protection of the present invention can provide effective light / dark state optoelectronic cathodic protection for 304SS and extend the service life of the metal.

[0075] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a WO3-ZIFs-AgInS2 composite film for photocathode protection, characterized in that The following steps are involved: (1) Cleaning the conductive glass; (2) growing a WO3 thin film on the conductive glass treated in step (1) by a hydrothermal method; (3) obtaining a WO3-ZIFs composite film by electrodeposition on the surface of the WO3 film; (4) The WO3-ZIFs-AgInS2 composite film obtained by in-situ growth is the composite film for photocathode protection.

2. The method for preparing the WO3-ZIFs-AgInS2 composite film for photocathode protection according to claim 1, characterized in that: In step (1), the cleaning includes placing the conductive glass in a first solution and a second solution for ultrasonic cleaning respectively; the first solution is ethanol or acetone, and the second solution is deionized water; the time for each ultrasonic cleaning is 10 to 30 minutes.

3. The method for preparing the WO3-ZIFs-AgInS2 composite film for photocathode protection according to claim 1, characterized in that: The conductive glass is FTO conductive glass or ITO conductive glass.

4. The method for preparing the WO3-ZIFs-AgInS2 composite film for photocathode protection according to claim 1, characterized in that: Step (2) is specifically as follows: dissolving sodium tungstate in water or anhydrous ethanol, then adding concentrated sulfuric acid to make a mixed solution, placing the cleaned conductive glass in the mixed solution, reacting at 70-100°C for 7-9h, then transferring to a muffle furnace and heating to 400-600°C, calcining for 1-3h to obtain a WO3 film.

5. The method for preparing the WO3-ZIFs-AgInS2 composite film for photocathode protection according to claim 4, characterized in that: The mass volume ratio of sodium tungstate to water or anhydrous ethanol is 1: (100-150) g / ml, and the mass volume ratio of sodium tungstate to concentrated sulfuric acid is 1: (0.8-1.2) g / ml.

6. The method for preparing the WO3-ZIFs-AgInS2 composite film for photocathode protection according to claim 1, characterized in that: Step (3) is specifically as follows: using FTO glass covered with WO3 as the working electrode, Pt and saturated calomel as the counter electrode and reference electrode respectively; using 50ml of 0.15M Co(NO3)2·6H2O solution as the electrolyte, at a voltage of -1.0V (vs SCE) for 200s to prepare Co(OH)2 on the WO3 surface; soaking the FTO glass prepared with Co(OH)2 in 1M 2-methylimidazole solution, 1M benzimidazole solution, and 1M 5-chlorobenzimidazole solution for 10-15h, respectively, to obtain ZIF67-A, ZIF67-B, and ZIF67-C, and then vacuum drying at 60-90°C for 0.5-1.5h to obtain WO3-ZIF67-A, WO3-ZIF67-B, and WO3-ZIF67-C.

7. The method for preparing the WO3-ZIFs-AgInS2 composite film for photocathode protection according to claim 1, characterized in that: Step (4) is specifically as follows: using a mixed solution of silver nitrate, indium nitrate and thioacetamide, placing the FTO conductive glass with the WO3-ZIFs composite film deposited on the surface facing downward for hydrothermal reaction at 150-200°C for 8-12 hours, removing the solution after the reactor is cooled, and drying at 80-100°C for 0-1h to prepare the WO3-ZIFs-AgInS2 composite film for photoelectric cathode protection.

8. The method for preparing the WO3-ZIFs-AgInS2 composite film for photocathode protection according to claim 7, characterized in that: The amounts of silver nitrate, indium nitrate and thioacetamide in the mixed solution of silver nitrate, indium nitrate and thioacetamide are 0.-15-0.25 g, 0.6-0.7 g and 0.4-0.5 g respectively.

9. A WO3-ZIFs-AgInS2 composite film for photocathode protection, prepared by the preparation method according to any one of claims 1 to 8.

10. Use of a WO3-ZIFs-AgInS2 composite film as claimed in claim 9 in photoelectrochemical cathodic protection.

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