Preparation and application of WO3 / MgIn2S4 / ZnIn2S4 photoelectrode materials for photocathode protection

Abstract

This invention belongs to the field of photocatheter protection technology, specifically relating to the preparation and application of WO3 / MgIn2S4 / ZnIn2S4 photoelectrode materials in photocatheter protection. Using a titanium sheet as a substrate, a WO3 precursor seed solution is first spin-coated onto the substrate and annealed to form a WO3 seed layer. Then, WO3, MgIn2S4, and ZnIn2S4 materials are gradually grown hydrothermally on the titanium sheet using a three-step hydrothermal method. By precisely controlling the synthesis conditions, the efficient synthesis of the WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material is achieved. The resulting photoelectrode material exhibits significant protective effects under continuous photocatheter protection, possessing excellent metal corrosion protection performance. It can be widely applied in various metal corrosion protection scenarios, demonstrating good practical application value and promising prospects for promotion.

Description

Technical Field

[0001] This invention belongs to the field of photocathode protection technology, specifically relating to the preparation of WO3 / MgIn2S4 / ZnIn2S4 photoelectrode materials and their application in photocathode protection. Background Technology

[0002] With the rapid development of industry and the large-scale extraction and use of fossil fuels, environmental pollution and energy shortages have become increasingly prominent issues. Among the many environmental and energy-related problems, metal corrosion—especially in marine environments—has become a severe global challenge, causing huge economic losses, serious resource waste, and numerous safety hazards every year. Therefore, it is urgent to explore suitable protective measures to slow down the corrosion process of metallic materials. Among various protective technologies, photocathode protection technology uses solar radiation to excite photoelectrons generated in semiconductor materials to protect metals. Compared with traditional sacrificial anode and impressed current methods, it has significant advantages such as being green, clean, and pollution-free.

[0003] In photocathode protection technology, semiconductor materials require external light to generate electrons. However, in situations without sunlight, such as cloudy days or nighttime, semiconductor materials cannot generate electrons, making it difficult to achieve cathodic protection for metallic materials. Therefore, achieving metal cathodic protection in dark environments has become a critical technical challenge in the practical application of photocathode protection technology, necessitating the introduction of semiconductor materials with electron storage capabilities into the photocathode protection system. WO3 semiconductor material possesses unique electron storage characteristics: when exposed to sunlight, some of the photogenerated electrons are directly used for cathodic protection, while the rest are stored; in dark environments, the electrons stored in WO3 are slowly released, thus achieving continuous protection for coupled metallic materials.

[0004] However, WO3 suffers from drawbacks such as a relatively positive conduction band potential and rapid recombination of photogenerated electron-hole pairs, which hinder efficient electron transfer. Therefore, constructing a WO3-based heterojunction system can optimize its band structure and improve carrier separation efficiency, thereby enhancing photocatheter protection performance and achieving continuous cathodic protection of metallic materials in dark environments. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention provides a method for preparing a WO3-based heterojunction system (WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material). This method involves the gradual hydrothermal growth of WO3, MgIn2S4, and ZnIn2S4 materials on a titanium sheet via a three-step hydrothermal process. By precisely controlling the synthesis conditions, the efficient preparation of the WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material is achieved. Furthermore, the prepared material exhibits excellent protective performance in long-term photocatheter protection applications.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of this invention provides a method for preparing a WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material, the method comprising the following steps:

[0008] S1. Polyvinyl alcohol ([C2H4O]) n , CAS: 9002-89-5, molecular weight 20,000-220,000) and tungstic acid (H2WO4) were dissolved in hydrogen peroxide (H2O2) solution to prepare WO3 precursor seed solution. The obtained seed solution was then spin-coated onto a titanium substrate. After drying and annealing, a WO3 seed layer was obtained on the titanium substrate.

[0009] S2. Tungsten hexachloride (WCl6) is dissolved in ethanol to form a precursor solution. A titanium sheet with a WO3 seed layer is then immersed in the precursor solution. After hydrothermal reaction, washing and annealing, a WO3 photoelectrode is obtained.

[0010] S3. Magnesium chloride hexahydrate (MgCl2·6H2O), indium trichloride tetrahydrate (InCl3·4H2O) and thioacetamide (C2H5NS) are dissolved in water to form a precursor solution. The WO3 photoelectrode is then immersed in the above precursor solution. After hydrothermal reaction, washing and drying, the WO3 / MgIn2S4 photoelectrode is obtained.

[0011] S4. Zinc nitrate hexahydrate (Zn(NO3)2·6H2O), indium trichloride tetrahydrate (InCl3·4H2O), and thioacetamide (C2H5NS) are dissolved in water to form a precursor solution. The WO3 / MgIn2S4 photoelectrode is then immersed in the above precursor solution. After hydrothermal reaction, washing, and drying, the WO3 / MgIn2S4 / ZnIn2S4 photoelectrode is obtained.

[0012] This invention utilizes a three-step hydrothermal method to progressively hydrothermally grow WO3, MgIn2S4, and ZnIn2S4 materials on titanium sheets. By precisely controlling the synthesis conditions, the invention achieves efficient synthesis of WO3 / MgIn2S4 / ZnIn2S4 photoelectrode materials. The resulting photoelectrode materials exhibit significant protective effects under continuous photocatheter protection and possess excellent metal corrosion protection properties.

[0013] Preferably, in S1, the titanium sheet is etched with hydrochloric acid before use, and the etching temperature is 80-95 ℃ for 1-3 hours.

[0014] Preferably, in S1, the mass ratio of polyvinyl alcohol to tungstic acid is 1:1-2, the concentration of polyvinyl alcohol in the hydrogen peroxide solution is 0.4-0.6 g / 10 mL, and the volume concentration of the hydrogen peroxide solution is 25-40%.

[0015] Preferably, in S1, the spin coating rate is 800-2000 r / min, the time is 25-35 s, the number of spin coatings is 2-5, the drying temperature after each spin coating is 70-85 ℃, and the drying time is 8-15 min.

[0016] Preferably, in S1 or S2, the annealing treatment temperature is 400-600 ℃ and the time is 1-3 h.

[0017] Preferably, in the precursor solution described in S2, the concentration of tungsten hexachloride is 0.001-0.005 mol / 70 mL.

[0018] More preferably, in the precursor solution described in S2, the concentration of tungsten hexachloride is 0.002 mol / 70 mL.

[0019] Preferably, in S2, the hydrothermal reaction is carried out at a temperature of 90-110 °C for a time of 7-9 h.

[0020] Preferably, in S3, the molar ratio of magnesium chloride hexahydrate, indium trichloride tetrahydrate, and thioacetamide is 1.2-1.5:1:1.8-2.3, and the concentration of magnesium chloride hexahydrate dissolved in water is 0.001571~0.002125 mol / 70 mL.

[0021] More preferably, in S3, the molar ratio of magnesium chloride hexahydrate, indium trichloride tetrahydrate, and thioacetamide is 1.32:1:2.

[0022] Preferably, in S3, the temperature of the hydrothermal reaction is 170-200 ℃, and the hydrothermal time is 5-7 h.

[0023] Preferably, in S4, the molar ratio of zinc nitrate hexahydrate, indium trichloride tetrahydrate, and thioacetamide is 0.4-0.6:1:1.8-2.3, and the concentration of zinc nitrate hexahydrate dissolved in water is 0.0014~0.0021 mol / 70 mL.

[0024] More preferably, in S4, the molar ratio of zinc nitrate hexahydrate, indium trichloride tetrahydrate, and thioacetamide is 0.504:1:2.

[0025] Preferably, in S4, the temperature of the hydrothermal reaction is 150-170 °C, and the hydrothermal time is 5-7 h.

[0026] The second aspect of the present invention also provides a WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material prepared by the preparation method described in the first aspect.

[0027] The third aspect of the present invention also provides the application of the WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material described in the second aspect as a working electrode in photocatheter protection of metallic materials.

[0028] Preferably, the metal material includes stainless steel (such as 316L SS), carbon steel, and alloys.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] This invention discloses a method for preparing a WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material. The method uses a titanium sheet as a substrate. First, a WO3 precursor seed solution is spin-coated onto the substrate and annealed to form a WO3 seed layer. Then, WO3, MgIn2S4, and ZnIn2S4 materials are sequentially grown on the substrate using a three-step hydrothermal method. By precisely controlling the reaction temperature, time, and reactant ratios in each step, the efficient synthesis of the photoelectrode material is achieved. This preparation method is simple to operate and the conditions are easily controlled. The resulting WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material exhibits excellent photocatheter protection performance, demonstrating a significant and long-lasting protective effect during metal corrosion protection. It can be widely used in various metal corrosion protection scenarios and has good practical application value and promising prospects for promotion. Attached Figure Description

[0031] Figure 1 The open circuit potential (OCP) curves of WO3 / MgIn2S4 / ZnIn2S4 in 3.5wt% NaCl solution under dark and light cyclic cutting conditions are shown.

[0032] Figure 2The current density (it) curves of WO3 / MgIn2S4 / ZnIn2S4 in 3.5wt% NaCl solution under dark and light cyclic cutting conditions are shown.

[0033] Figure 3 The open circuit potential (OCP) curves of WO3 / MgIn2S4 / ZnIn2S4 in 3.5wt% NaCl solution for photocathode protection of 316 L SS (dark state and cyclic light cutting conditions).

[0034] Figure 4 The current density (it) curves of WO3 / MgIn2S4 / ZnIn2S4 in 3.5wt% NaCl solution for photocatheter protection of 316 L SS (dark state and light cycle cutting conditions).

[0035] Figure 5 The open-circuit potential (OCP) curves of WO3 / MgIn2S4 / ZnIn2S4 after 2 h of photo-induced cathodic protection with 316 L SS are shown.

[0036] Figure 6 The current density (it) curves of WO3 / MgIn2S4 / ZnIn2S4 after irradiation in 3.5wt% NaCl solution for 2 h for continuous photocatheter protection of 316 L SS are shown.

[0037] Figure 7 shows a scanning electron microscope (SEM) image of WO3 / MgIn2S4 / ZnIn2S4.

[0038] Figure 8 shows a high-resolution transmission electron microscope (HRTEM) image of WO3 / MgIn2S4 / ZnIn2S4. Detailed Implementation

[0039] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0041] Example 1

[0042] The preparation method of WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material specifically includes the following steps:

[0043] S1: Place a titanium sheet (1×5 cm) 2 The substrate for preparing the photoelectrode was etched with concentrated hydrochloric acid at 90 °C for 1 h. 0.5 g of polyvinyl alcohol (type 1795, [C2H4O]) was used. n (n≈1700, degree of alcoholysis 92.0~94.0 mol%, weight average molecular weight approximately 75000) and 0.625 g tungstic acid were added to 10 mL of 30% hydrogen peroxide solution and stirred for 3 h to prepare a precursor seed solution of WO3. Then, 100 μL of the seed solution was taken onto a titanium substrate, spin-coated at 1000 r / min for 30 s and dried at 80℃ for 10 min. The above spin-coating and drying steps were repeated 3 times. Afterwards, the substrate was annealed in a muffle furnace at 500℃ for 2 h to obtain a WO3 seed layer on the titanium substrate.

[0044] S2: Place the titanium sheet with the WO3 seed layer growing on one side into the reaction vessel, and at the same time dissolve 0.002 mol of tungsten hexachloride in 70 mL of anhydrous ethanol to form a precursor solution and stir until transparent. Then pour the resulting solution into the reaction vessel (immersing the titanium sheet) and carry out a hydrothermal reaction at 100 °C for 8 h. After the reaction is completed, take it out and wash it with water and anhydrous ethanol. Finally, anneal it in a muffle furnace at 500 °C for 2 h to obtain the WO3 photoelectrode.

[0045] S3: Place the WO3 photoelectrode face down in the reaction vessel. Simultaneously, dissolve 0.001848 mol of magnesium chloride hexahydrate, 0.0014 mol of indium trichloride tetrahydrate, and 0.0028 mol of thioacetamide in 70 mL of deionized water to form a precursor solution. Then, pour the resulting solution into the reaction vessel and carry out a hydrothermal reaction at 180 °C for 6 h. After the reaction is completed, remove the electrode and wash it with water and anhydrous ethanol. Finally, dry it at 60 °C for 4 h to obtain the WO3 / MgIn2S4 photoelectrode.

[0046] S4: Place the WO3 / MgIn2S4 photoelectrode face down in the reaction vessel. Simultaneously, dissolve 0.001764 mol of zinc nitrate hexahydrate, 0.0035 mol of indium trichloride tetrahydrate, and 0.007 mol of thioacetamide in 70 mL of deionized water to form a precursor solution. Then, pour the resulting solution into the reaction vessel and carry out a hydrothermal reaction at 160 °C for 6 h. After the reaction is completed, remove the electrode and wash it with water and anhydrous ethanol. Finally, dry it at 60 °C for 4 h to obtain the WO3 / MgIn2S4 / ZnIn2S4 photoelectrode.

[0047] Example 2

[0048] The specific steps for testing the photoelectric performance of WO3 / MgIn2S4 / ZnIn2S4 photoelectrode materials are as follows:

[0049] (1) Photoelectric performance testing environment of WO3 / MgIn2S4 / ZnIn2S4 photoelectrode under light and dark conditions: An electrochemical cell device made of polytetrafluoroethylene was used to test the photoelectric performance related polarization curves under light and dark conditions in a three-electrode system. In this experiment, the WO3 / MgIn2S4 / ZnIn2S4 photoelectrode, Ag / AgCl reference electrode and Pt sheet electrode were used as the working electrode, reference electrode and counter electrode, respectively, to form a three-electrode system. A 3.5wt% NaCl solution was used as the electrolyte solution environment. The photoelectric test experiment used an AM 1.5G filter with a light intensity of 100 mW / cm. 2 A xenon lamp is used as the light source to simulate sunlight in the experiment. The solution environment and light intensity can be adjusted according to the different systems and contents being studied.

[0050] (2) Dark-state and photo-induced OCP tests: First, under the above experimental environment, dark-state OCP was tested using an electrochemical workstation at a constant bias voltage of 0 V vs. Ag / AgCl (time: 600 s), allowing the WO3 / MgIn2S4 / ZnIn2S4 photoelectrode to be in a stable and activated state. Then, photo-induced OCP was tested (time: 1600 s). During the photo-induced OCP test, the dark-state and light-illuminated states were cycled every 200 s to obtain the results. Figure 1 The photoinduced OCP curve is shown.

[0051] (3) Photopolarization curve test: In the above test environment, the photocurrent density (it) curve was tested under illumination using an electrochemical workstation (time: 600 s). During the test, the dark state and the illumination state were cycled every 50 s to obtain the results. Figure 2 The it curve shown.

[0052] (4) Results explanation: such as Figure 1 , 2 As shown in the figure, the test results indicate that the WO3 / MgIn2S4 / ZnIn2S4 photoelectrode prepared in this invention exhibits excellent photoelectric properties. Under illumination, its photoelectric potential shifts negatively to -498 mV, and its photocurrent density is 0.329 mA / cm² at a 0 V bias voltage. 2 .

[0053] Example 3

[0054] The specific steps for testing the performance of photocatheter protection are as follows:

[0055] (1) Photocathodic protection performance test environment of WO3 / MgIn2S4 / ZnIn2S4 photoelectrode under light and dark conditions: An electrochemical cell device made of polytetrafluoroethylene was used to test the polarization curves related to photocathodic protection performance under light and dark conditions in a three-electrode system. In this experiment, the WO3 / MgIn2S4 / ZnIn2S4 photoelectrode, Ag / AgCl reference electrode and 316L SS were used as the working electrode, reference electrode and counter electrode, respectively, to form a three-electrode system. 3.5wt% NaCl solution was used as the electrolyte solution environment, and the light intensity used in the photocathodic protection test was 100 mW / cm². 2 A xenon lamp equipped with an AM 1.5G filter was used as the light source to simulate sunlight for the experiment. The solution environment and light intensity could be adjusted according to the specific system and content being studied.

[0056] (2) Dark-state and photo-induced OCP tests: The dark-state OCP test in this experiment was conducted to ensure that the photoelectrode was in a stable and activated state in the electrolyte solution environment, and also to provide a good environment for the electrode in subsequent tests. The working electrode was connected to the counter electrode (protected metals such as 316L SS), the working electrode clamp of the electrochemical workstation was connected to the counter electrode, the reference electrode clamp was connected to the Ag / AgCl reference electrode, and the counter electrode clamp was not connected. Under the above experimental environment, the dark-state OCP was tested at a constant bias voltage of 0 V vs. Ag / AgCl using the electrochemical workstation (time: 600 s), so that the WO3 / MgIn2S4 / ZnIn2S4 photoelectrode was in a stable and activated state. Then the photo-induced OCP was tested (time: 1600 s). During the photo-induced OCP test, the dark state and light state were cycled every 200 s, and the photo-induced OCP curve shown in Figure 3 was obtained.

[0057] (3) Photopolarization curve test: In the above test environment, the connection method was changed so that the working electrode clip of the electrochemical workstation was connected to the working electrode of the battery, and the reference electrode clip and the counter electrode clip were connected together to the counter electrode (protected metal such as 316L SS). The photocurrent density (it) curve was tested under illumination using the electrochemical workstation (time: 600 s). During the test, the dark state and the illumination state were cycled every 50 s to obtain the results. Figure 4 The it curve shown.

[0058] (4) Results explanation: such as Figure 3 , 4As shown in the figure, the OCP and it curves of the photocathode protection performance of WO3 / MgIn2S4 / ZnIn2S4 photoelectrode connected to 316L SS demonstrate that the WO3 / MgIn2S4 / ZnIn2S4 photoelectrode prepared in this invention exhibits excellent photoelectric properties and can achieve cathodic protection for 316L SS. Under illumination, the photocathode protection potential for 316L SS shifts negatively to -424 mV, and the current density at a 0 V bias voltage is 14.05 μA / cm². 2 Meanwhile, in the continuous photo-induced cathodic protection test of the photoelectrode on 316L SS, the OCP and it curves after 0.5 hours of initial light-off followed by 2 hours of illumination and then back to light-off are shown below. Figure 5 , 6 As shown, it can be seen that it exhibits ultra-long continuous photocathode protection for 316L SS for about 24 hours in the dark.

[0059] In summary, the photoelectric performance and photocathode protection performance tests of the WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material demonstrate that this material can achieve ultra-long-lasting cathodic protection for metals such as 316L SS in the dark state after illumination. Furthermore, this invention also utilizes field emission scanning electron microscopy (SEM, Figure 7) and high-resolution transmission electron microscopy (HRTEM). Figure 8 The material was characterized. Among other things, Figure 7 The SEM images show that the ZnIn2S4 material successfully adhered to the WO3 / MgIn2S4 surface and completely covered the WO3 / MgIn2S4. Figure 8 The HRTEM images show the formation of a well-developed WO3 / MgIn2S4 / ZnIn2S4 three-phase heterojunction system. In summary, this invention not only ensures the successful preparation of the WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material, but also provides a solid scientific foundation for its application in photocatheter protection.

[0060] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for preparing a WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material, characterized in that, Includes the following steps: S1. Polyvinyl alcohol and tungstic acid are dissolved in hydrogen peroxide solution to prepare WO3 precursor seed solution. The obtained seed solution is then spin-coated onto a titanium substrate. After drying and annealing, a WO3 seed layer is obtained on the titanium substrate. S2. Tungsten hexachloride is dissolved in ethanol to form a precursor solution. A titanium sheet with a WO3 seed layer is then immersed in the precursor solution. After hydrothermal reaction, washing and annealing, a WO3 photoelectrode is obtained. S3. Magnesium chloride hexahydrate, indium trichloride tetrahydrate and thioacetamide are dissolved in water to form a precursor solution. Then, the WO3 photoelectrode is immersed in the above precursor solution. After hydrothermal reaction, washing and drying, the WO3 / MgIn2S4 photoelectrode is obtained. S4. Zinc nitrate hexahydrate, indium trichloride tetrahydrate, and thioacetamide are dissolved in water to form a precursor solution. The WO3 / MgIn2S4 photoelectrode is then immersed in the precursor solution. After hydrothermal reaction, washing, and drying, the WO3 / MgIn2S4 / ZnIn2S4 photoelectrode is obtained.

2. The method for preparing a WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material according to claim 1, characterized in that, In S1, the titanium sheet is etched with hydrochloric acid before use. The etching temperature is 80-95 ℃ and the time is 1-3 h.

3. The method for preparing a WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material according to claim 1, characterized in that, In S1, the mass ratio of polyvinyl alcohol to tungstic acid is 1:1-2, the concentration of polyvinyl alcohol in the hydrogen peroxide solution is 0.4-0.6 g / 10 mL, and the volume concentration of the hydrogen peroxide solution is 25-40%.

4. The method for preparing a WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material according to claim 1, characterized in that, In S1, the spin coating rate is 800-2000 r / min, the time is 25-35 s, the number of spin coatings is 2-5, the drying temperature after each spin coating is 70-85 ℃, and the drying time is 8-15 min.

5. The method for preparing a WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material according to claim 1, characterized in that, In S1 or S2, the annealing treatment is carried out at a temperature of 400-600 ℃ for 1-3 h.

6. The method for preparing a WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material according to claim 1, characterized in that, In the precursor solution described in S2, the concentration of tungsten hexachloride is 0.001-0.005 mol / 70 mL; The hydrothermal reaction described in S2 is carried out at a temperature of 90-110 ℃ for a time of 7-9 h.

7. The method for preparing a WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material according to claim 1, characterized in that, In S3, the molar ratio of magnesium chloride hexahydrate, indium trichloride tetrahydrate, and thioacetamide is 1.2-1.5:1:1.8-2.3, the concentration of magnesium chloride hexahydrate dissolved in water is 0.001571~0.002125 mol / 70 mL, the hydrothermal reaction temperature is 170-200 ℃, and the hydrothermal time is 5-7 h.

8. The method for preparing a WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material according to claim 1, characterized in that, In S4, the molar ratio of zinc nitrate hexahydrate, indium trichloride tetrahydrate, and thioacetamide is 0.4-0.6:1:1.8-2.3, the concentration of zinc nitrate hexahydrate dissolved in water is 0.0014~0.0021 mol / 70 mL, the hydrothermal reaction temperature is 150-170 ℃, and the hydrothermal time is 5-7 h.

9. The WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material prepared by the preparation method according to any one of claims 1-8.

10. The application of the WO3 / MgIn2S4 / ZnIn2S4 photoelectrode material as described in claim 9 as a working electrode in photocatheter protection of metallic materials.

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