A method for preparing a WO3-BiVO4-NiO composite material for metal photocathode protection
By growing a WO3-BiVO4-NiO composite film in situ on a conductive tungsten sheet, the problems of high photogenerated electron-hole recombination rate and easy coating peeling in the prior art are solved, and effective photocathode protection is achieved in a variety of environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUILIN UNIVERSITY OF TECHNOLOGY
- Filing Date
- 2023-07-10
- Publication Date
- 2026-05-15
AI Technical Summary
When existing semiconductor materials are used for metal photocathode protection, the recombination rate of photogenerated electrons and holes is high, which cannot effectively protect metals underwater or in dark conditions, and the coating is prone to peeling off.
Using a conductive tungsten sheet as a substrate, WO3 is grown in situ through anodic oxidation, followed by the deposition of BiVO4 and NiO to form a closely contacted WO3-BiVO4-NiO composite film. BiVO4 is used to broaden the light absorption range, while NiO enriches photogenerated holes and reduces the probability of electron-hole recombination.
It improves the separation efficiency of photogenerated electrons and holes, enhances the protection performance of the photocathode, and can provide effective protection under normal light, underwater and dark conditions, and the film layer is firmly attached.
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Figure CN116875984B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of photocathode protection materials technology, and relates to a method for preparing WO3-BiVO4-NiO composite material and its application in metal photocathode protection. Background Technology
[0002] To mitigate metal corrosion, various anti-corrosion technologies and methods have been developed, such as coating metal surfaces with anti-corrosion coatings and corrosion inhibitors, applying an external current to the metal for cathodic protection, connecting sacrificial anodes for cathodic protection, and photocathodic protection, among others. Among these technologies and methods, photocathodic protection has received widespread attention. The principle of photocathodic protection is that semiconductor materials generate photoelectrons when exposed to light. These photoelectrons transfer to the metal, shifting the metal's potential negatively, making it less susceptible to oxidation and corrosion. Compared to traditional electrochemical cathodic protection methods, photocathodic protection utilizes the energy of sunlight for cathodic protection, requiring no external electrical energy. Furthermore, the semiconductor material on the photoanode is not consumed during the protection process, making it environmentally friendly and recyclable. Semiconductor materials used in metal photocathodic protection need to possess good visible light absorption characteristics, good photoelectric conversion characteristics, and a sufficiently low conduction band potential to provide effective protection.
[0003] Tungsten oxide is an n-type semiconductor material with excellent photoelectric properties and energy storage capabilities. It can store electrical energy under illumination and release it in darkness, thus providing a certain degree of protection when used in metal photocathode protection under dark conditions. However, when used alone, tungsten oxide has a high recombination probability of photogenerated electrons and holes, which does not provide a good protective effect. Combining tungsten oxide with other semiconductors to form a heterojunction allows the built-in electric field of the heterojunction to effectively separate photogenerated electrons and holes, reducing the probability of electron-hole recombination and enhancing the photocathode protection function.
[0004] Bismuth vanadate is also an n-type semiconductor with a smaller band gap than tungsten oxide. When combined with tungsten oxide, it can broaden the light absorption range and improve its photoelectric properties. Nickel oxide, a p-type semiconductor, forms a ternary complex with tungsten oxide and bismuth vanadate. This complex can enrich the holes generated when the material is exposed to light, further improving the efficiency of electron-hole separation and allowing more photogenerated electrons to flow to the protected metal.
[0005] Currently, many methods for photocathode protection of metals using semiconductors involve coating the metal surface with a paste made from semiconductor materials. This method is only suitable for protecting metals exposed to light, not for protecting metals working underwater or in the dark, and the semiconductor coating is also relatively easy to peel off. Summary of the Invention
[0006] This invention aims to provide a method for preparing a WO3-BiVO4-NiO composite material and its application in metal photocathode protection. The invention utilizes the excellent electrical conductivity of tungsten and its ability to be oxidized to WO3. A tungsten sheet is used as a substrate, and WO3 is grown in situ on it through anodic oxidation. Subsequently, BiVO4 and NiO are deposited on the WO3 film through spin coating, chemical deposition, and sintering to form a WO3-BiVO4-NiO semiconductor composite film. The in-situ growth method ensures close contact between WO3 and the tungsten sheet, reducing electron transport resistance, while also ensuring the strong adhesion of the semiconductor film to the tungsten substrate. The composite of BiVO4 and WO3 broadens the light absorption range of the material and improves the efficiency of photogenerated electron-hole separation. The composite of NiO enriches the photogenerated holes in the material, further reducing the probability of photogenerated electron-hole recombination. Simultaneously, NiO also protects WO3 and BiVO4 from photocorrosion.
[0007] The preparation method of the WO3-BiVO4-NiO composite material for metal photocathode protection according to the present invention includes the following steps:
[0008] (1) Using tungsten sheet as anode and HNO3 solution as electrolyte, the solution is kept at a constant temperature of 50℃. A constant voltage is applied to anolyze the tungsten sheet. The resulting sample is rinsed and dried with deionized water, and then annealed at 500℃ for 4 h in air.
[0009] (2) NH4VO3, Bi(NO3)3·5H2O and citric acid were added sequentially to an aqueous solution of HNO3 with a mass content of 23.3% and stirred for 8 hours to form a blue transparent precursor solution. Acetic acid and 0.032 g of polyvinyl alcohol were added to the precursor solution and mixed evenly. 0.2 mL of the mixture was then dropped onto a WO3 film, spin-coated, dried at 100 °C for 1 h, and then annealed at 500 °C for 8 h in air to obtain WO3-BiVO4.
[0010] (3) Dissolve NiCl2, NH4Cl and NaOH in water to prepare a nickel-amine complex aqueous solution. Immerse the WO3-BiVO4 film in 30 ml of the nickel-amine complex aqueous solution and keep it at 55 °C for a certain period of time. Rinse the sample with deionized water, dry it at room temperature for 12 hours, and then anneal it at 400 °C for 2 hours in air to form WO3-BiVO4-NiO.
[0011] In step (1), the concentration of HNO3 is 1~3 mol / L, the voltage of anodizing is 20~40 V, and the anodizing time is 1~4 hours.
[0012] In step (2), the concentration range of Bi(NO3)3·5H2O in the mixed solution is 1 / 6~1 / 2 mol / L, the molar ratio of NH4VO3 to Bi(NO3)3·5H2O in the mixed solution is 1:1, the molar ratio of citric acid to Bi(NO3)3·5H2O is 1:2, and the relationship between the amount of acetic acid added and the amount of Bi(NO3)3·5H2O is 0.92 L of acetic acid added per mole of Bi(NO3)3·5H2O.
[0013] In step (3), the concentration of NiCl2 in the mixed solution is 0.7 mol / L, the concentration of NH4Cl is 2 mol / L, the concentration of NaOH is 0.7 mol / L, and the immersion time of the WO3-BiVO4 film in this nickel-amine complex aqueous solution is 2 to 6 hours.
[0014] This invention utilizes an in-situ method for growing WO3 on a conductive tungsten sheet as a substrate. This method ensures close contact between the semiconductor film and the substrate, facilitating electron transport and guaranteeing the film's strong adhesion to the substrate. The energy storage properties of WO3 ensure protection for metals even in the absence of light. The composite of BiVO4 and NiO with WO3 broadens the material's light absorption range and improves the separation efficiency of photogenerated electrons and holes, thereby enhancing the performance of photocathode protection. The WO3-BiVO4-NiO prepared on the tungsten sheet can provide photocathode protection not only for metals exposed to normal light but also for metals operating underwater and in darkness. Attached Figure Description
[0015] Figure 1 The image shows the X-ray diffraction pattern of the electrode prepared in Example 3 of this invention. As can be seen from the image, in addition to the diffraction peak of the tungsten substrate, diffraction peaks of WO3, BiVO4, and NiO appear, proving that a WO3-BiVO4-NiO composite film was obtained.
[0016] Figure 2 The images show scanning electron microscope (SEM) images of the electrodes prepared in Comparative Examples 1 (a), 2 (b), and 3 (c) of this invention. As can be seen from the images, Comparative Example 1 yielded WO3 nanosheets. The nanosheets obtained in Comparative Example 2 showed increased thickness compared to those in Comparative Example 1, indicating the presence of a BiVO4 layer on the surface. The nanosheets obtained in Example 3 showed little difference from those in Comparative Example 2 because of the smaller amount of deposited NiO, and the thickness of the nanosheets did not change significantly compared to those in Comparative Example 2.
[0017] Figure 3The figures show the photoelectric response curves of the electrodes prepared in Examples 1-4 and Comparative Examples 1 and 2 of this invention. As can be seen from the figures, the photocurrent density generated by the electrodes obtained in Examples 1-4 is significantly higher than that in Comparative Examples 1 and 2, proving that the efficiency of photogenerated electron-hole separation in the WO3-BiVO4-NiO ternary composite is higher than that in the binary composite WO3-BiVO4, and even higher than that in pure WO3. Among them, Example 3 produced the highest photocurrent density, reaching 0.3 mA / cm². 2 .
[0018] Figure 4 100mW / cm 2 Under illumination, Tafel curves were obtained for 316 steel and 316 steel connected to the electrodes prepared in Examples 1-4 and Comparative Examples 1 and 2 of this invention. As can be seen from the figure, the 316 stainless steel connected to the electrodes prepared in Examples 1-4 and Comparative Examples 1 and 2 all exhibited a more negative corrosion potential compared to the 316 steel without a photoanode, demonstrating that the electrodes provided photocathodic protection for the 316 steel. The electrodes obtained in Examples 1-4 significantly shifted the corrosion potential of 316 steel negatively, proving that the WO3-BiVO4-NiO ternary composite provided better photocathodic protection than the binary composite WO3-BiVO4, and even better than pure WO3. Among them, the 316 steel connected to the electrode obtained in Example 3 exhibited the most negative corrosion potential, reaching -633 mV. Detailed Implementation
[0019] Example 1:
[0020] (1) Place the tungsten sheet in a 3 mol / L HNO3 solution at a constant temperature of 50℃. Anodize at 40V for 2 hours, rinse the obtained sample with deionized water and dry it, and then anneal it in a muffle furnace at 500℃ for 4 hours;
[0021] (2) 0.001 mol NH4VO3, 0.001 mol Bi(NO3)3·5H2O and 0.002 mol citric acid were added sequentially to 6 mL of HNO3 solution with a mass content of 23.3% and stirred overnight to form a blue transparent precursor solution. 0.92 mL of acetic acid and 0.032 g of polyvinyl alcohol were added to the precursor solution and mixed evenly. 0.2 mL of the mixture was then pipetted onto a WO3 membrane. After spin coating, the membrane was dried at 100 °C for 1 h and then annealed at 500 °C for 8 h in air to obtain a WO3-BiVO4 membrane.
[0022] (3) Dissolve 0.07 mol NiCl2, 0.2 mol NH4Cl and 0.07 mol NaOH in 100 ml of deionized water to obtain a nickel-amine complex aqueous solution. Immerse the WO3-BiVO4 membrane in 30 ml of this nickel-amine complex aqueous solution and keep it at 55 °C for 6 hours. Then, rinse the sample with deionized water, dry it at room temperature for 12 hours, and then anneal it at 400 °C for 2 hours in air to obtain the WO3-BiVO4-NiO membrane.
[0023] Example 2:
[0024] (1) Place the tungsten sheet in a 2 mol / L HNO3 solution at a constant temperature of 50℃. Anodize at 30V for 3 hours, rinse the obtained sample with deionized water and dry it, and then anneal it in a muffle furnace at 500℃ for 4 hours;
[0025] (2) 0.003 mol NH4VO3, 0.003 mol Bi(NO3)3·5H2O and 0.006 mol citric acid were added sequentially to 6 mL of HNO3 solution with a mass content of 23.3% and stirred overnight to form a blue transparent precursor solution. 2.76 mL of acetic acid and 0.032 g of polyvinyl alcohol were added to the precursor solution and mixed thoroughly. 0.2 mL of the mixture was then pipetted onto a WO3 membrane. After spin coating, the membrane was dried at 100 °C for 1 h and then annealed at 500 °C for 8 h in air to obtain a WO3-BiVO4 membrane.
[0026] (3) Dissolve 0.07 mol NiCl2, 0.2 mol NH4Cl and 0.07 mol NaOH in 100 ml of deionized water to obtain a nickel-amine complex aqueous solution. Immerse the WO3-BiVO4 membrane in 30 ml of this nickel-amine complex aqueous solution and keep it at 55 °C for 6 hours. Then, rinse the sample with deionized water, dry it at room temperature for 12 hours, and then anneal it at 400 °C for 2 hours in air to obtain the WO3-BiVO4-NiO membrane.
[0027] Example 3:
[0028] (1) Place the tungsten sheet in a 1.5 mol / L HNO3 solution at a constant temperature of 50℃. Anodize at 20V for 2 hours, rinse the obtained sample with deionized water and dry it, and then anneal it in a muffle furnace at 500℃ for 4 hours;
[0029] (2) 0.002 mol NH4VO3, 0.002 mol Bi(NO3)3·5H2O and 0.002 mol citric acid were added sequentially to 6 mL of HNO3 solution with a mass content of 23.3% and stirred overnight to form a blue transparent precursor solution. 1.84 mL of acetic acid and 0.032 g of polyvinyl alcohol were added to the precursor solution and mixed evenly. 0.2 mL of the mixture was then pipetted onto a WO3 membrane. After spin coating, the membrane was dried at 100 °C for 1 h and then annealed at 500 °C for 8 h in air to obtain a WO3-BiVO4 membrane.
[0030] (3) Dissolve 0.07 mol NiCl2, 0.2 mol NH4Cl and 0.07 mol NaOH in 100 ml of deionized water to obtain a nickel-amine complex aqueous solution. Immerse the WO3-BiVO4 membrane in 30 ml of this nickel-amine complex aqueous solution and keep it at 55 °C for 4 hours. Then, rinse the sample with deionized water, dry it at room temperature for 2 hours, and then anneal it at 400 °C in air for 2 hours to obtain the WO3-BiVO4-NiO membrane.
[0031] Example 4:
[0032] (1) Place the tungsten sheet in a 1 mol / L HNO3 solution at a constant temperature of 50℃. Anodize at 20V for 4 hours, rinse the obtained sample with deionized water and dry it, and then anneal it in a muffle furnace at 500℃ for 4 hours;
[0033] (2) 0.002 mol NH4VO3, 0.002 mol Bi(NO3)3·5H2O and 0.002 mol citric acid were added sequentially to 6 mL of HNO3 solution with a mass content of 23.3% and stirred overnight to form a blue transparent precursor solution. 1.84 mL of acetic acid and 0.032 g of polyvinyl alcohol were added to the precursor solution and mixed evenly. 0.2 mL of the mixture was then pipetted onto a WO3 membrane. After spin coating, the membrane was dried at 100 °C for 1 h and then annealed at 500 °C for 8 h in air to obtain a WO3-BiVO4 membrane.
[0034] (3) Dissolve 0.07 mol NiCl2, 0.2 mol NH4Cl and 0.07 mol NaOH in 100 ml of deionized water to obtain a nickel-amine complex aqueous solution. Immerse the WO3-BiVO4 membrane in 30 ml of this nickel-amine complex aqueous solution and keep it at 55 °C for 6 hours. Then, rinse the sample with deionized water, dry it at room temperature for 2 hours, and then anneal it at 400 °C for 2 hours in air to obtain the WO3-BiVO4-NiO membrane.
[0035] Comparative Example 1:
[0036] Perform only step (1) of Example 3.
[0037] Comparative Example 2:
[0038] Perform steps (1) and (2) in Example 3.
[0039] Metal photocathode protection test:
[0040] A mixed solution of NaI (0.1 mol / L) and NaOH (0.2 mol / L) was prepared as the electrolyte for the photovoltaic cell. A mixed solution of NaCl (3.5 wt%) and NaOH (0.2 mol / L) was prepared as the electrolyte for the corrosion cell. The photovoltaic cell electrolyte and the corrosion cell electrolyte were connected by a salt bridge. The prepared sample was immersed in the photovoltaic cell electrolyte, and 316 stainless steel was immersed in the corrosion cell electrolyte. The sample and the 316 stainless steel were connected by a wire. On one side of the photovoltaic cell, a solar simulator was used to provide 100 mW / cm² of power. 2 Irradiation. In the corrosion bath, 316 stainless steel was used as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode. The photocathode protection effect of the sample on 316 stainless steel was tested using an electrochemical workstation.
Claims
1. A method for preparing WO3-BiVO4-NiO composite material for metal photocathode protection, characterized in that... WO3 nanosheets were grown in situ on tungsten sheets using anodic oxidation. BiVO4 was prepared on the WO3 nanosheets by spin-coating a BiVO4 precursor solution followed by sintering. NiO was then grown on the WO3-BiVO4 composite material by chemical deposition followed by sintering, yielding a WO3-BiVO4-NiO composite material for metal photocathode protection. The specific steps are as follows: (1) Using tungsten sheets that have been ultrasonically cleaned and dried by acetone, isopropanol, ethanol and deionized water respectively as anodes, HNO3 solution as electrolyte, constant solution temperature of 50℃, constant voltage is applied to anolyze tungsten sheets, the obtained samples are rinsed and dried with deionized water, and then annealed at 500℃ for 4 hours in air atmosphere. (2) NH4VO3, Bi(NO3)3·5H2O and citric acid were added sequentially to an aqueous solution of HNO3 with a concentration of 23.3wt%, and stirred for 8 hours to form a blue transparent precursor solution; acetic acid and 0.032g of polyvinyl alcohol were added to the precursor solution and mixed evenly, and 0.2mL of the mixture was dropped onto a WO3 film, spin-coated, dried at 100℃ for 1h, and then annealed at 500℃ for 8h in air to obtain WO3-BiVO4; (3) Dissolve NiCl2, NH4Cl and NaOH in water to prepare a nickel-amine complex aqueous solution; immerse the WO3-BiVO4 film in 30 ml of nickel-amine complex aqueous solution and keep it at 55 °C for a certain time; rinse the sample with deionized water, dry it at room temperature for 12 hours, and then anneal it at 400 °C for 2 hours in air to form WO3-BiVO4-NiO.
2. The method for preparing WO3-BiVO4-NiO composite material for metal photocathode protection according to claim 1, characterized in that, In step (1), the concentration of HNO3 is 1~3 mol / L, the voltage of anodizing is 20~40 V, and the anodizing time is 1~4 hours.
3. The method for preparing WO3-BiVO4-NiO composite material for metal photocathode protection according to claim 1, characterized in that, In step (2), the concentration range of Bi(NO3)3·5H2O in the mixed solution is 1 / 6~1 / 2 mol / L, the molar ratio of NH4VO3 to Bi(NO3)3·5H2O in the mixed solution is 1:1, the molar ratio of citric acid to Bi(NO3)3·5H2O is 1:2, and the relationship between the amount of acetic acid added and the amount of Bi(NO3)3·5H2O is that 0.92 L of acetic acid is added for every mole of Bi(NO3)3·5H2O.
4. The method for preparing WO3-BiVO4-NiO composite material for metal photocathode protection according to claim 1, characterized in that, In step (3), the concentration of NiCl2 in the mixed solution is 0.7 mol / L, the concentration of NH4Cl is 2 mol / L, the concentration of NaOH is 0.7 mol / L, and the immersion time of the WO3-BiVO4 film in this nickel-amine complex aqueous solution is 2 to 6 hours.
5. The WO3-BiVO4-NiO composite material prepared by the method according to any one of claims 1-4 is applied to the photocathode protection of metals.