Bi2MoO6 / TiO2 composite photo-anode material as well as preparation method and application thereof

Abstract

The invention provides a Bi2MoO6 / TiO2 composite photo-anode material as well as a preparation method and application thereof, and belongs to the technical field of metal corrosion and protection. A heterojunction engineering strategy is adopted, Bi2MoO6 is deposited on the surface of the TiO2 nanotube array through a one-step hydrothermal reaction, the Bi2MoO6 / TiO2 composite photo-anode with an S-shaped heterojunction structure is prepared, the material is formed by compounding the TiO2 nanotube array at the bottom layer and Bi2MoO6 nanoparticles at the top layer, the light absorption utilization rate and the photoelectric conversion efficiency are more excellent, and the photoelectric conversion efficiency is higher. The photon-generated carrier separation and migration efficiency is remarkably improved, and the long-term stability is higher. When the material is applied to photoelectrochemical cathode protection of metal / alloy, rapid and efficient protection of nickel-plated magnesium alloy can be realized, metal corrosion is effectively inhibited, and a novel photo-anode material with excellent performance is provided for the field of metal corrosion prevention.

Description

Technical Field

[0001] This invention relates to the field of metal corrosion and protection technology, and in particular to a Bi2MoO6 / TiO2 composite photoanode material, its preparation method, and its application. Background Technology

[0002] Photogenerated cathodic protection (PECCP) technology, as a near-zero-energy corrosion protection technology, has attracted widespread attention. PECCP technology has significant application value in harsh service scenarios such as marine bridges and aerospace electronic equipment housings. Its practical application places high demands on the light absorption utilization rate, carrier separation and transport efficiency, and long-term stability of the photoanode. Anatase TiO2 is a hot material in the PECCP field. As a wide-bandgap semiconductor (Eg > 3.0 eV), its photoelectric conversion efficiency is low due to its ultraviolet light response characteristics (accounting for only 4% of the solar spectrum) and high carrier recombination rate, making it difficult to meet the high-efficiency protection requirements of special components such as nickel-plated magnesium alloys. Therefore, it is urgent to optimize its photoelectrochemical performance through precise modification.

[0003] Bismuth molybdate (Bi₂MoO₆) is [Bi₂O₂]. 2+ Layers and perovskite type [MoO4] 2- Inorganic semiconductor materials composed of alternating layers possess a unique Aurivillius structure, exhibiting excellent visible light response, a suitable band gap (~2.7 eV), and superior chemical stability, making them one of the preferred materials for TiO2 modification. Currently, a few studies have attempted to construct composite systems using Bi2MoO6 to modify TiO2, but existing Bi2MoO6 / TiO2 composites generally suffer from two major drawbacks: first, Bi2MoO6 morphology is mostly blocky, sheet-like, or disordered aggregated particles, resulting in weak interfacial bonding with TiO2 nanotube arrays and high charge transfer resistance; second, the band structure of Bi2MoO6 is not precisely controlled, leading to insufficient band offset matching with TiO2, resulting in the formation of mostly traditional type II heterojunctions after composite formation. This prevents efficient separation of photogenerated electron-hole pairs, thus failing to fundamentally solve the problem of slow carrier migration dynamics and making it difficult to meet the high-performance requirements of PECCP technology for photoanodes.

[0004] Magnesium alloys possess characteristics such as low density and high specific strength, making them widely applicable in aerospace, transportation, 3C electronics, and military industries, earning them the reputation of "green engineering materials of the 21st century." However, susceptibility to corrosion is a significant factor limiting their application. Electroless nickel plating is a common surface treatment method for magnesium alloys, imparting advantages such as good wear resistance and high hardness, but a significant drawback is its susceptibility to galvanic corrosion. Chinese invention patent (202110428189.4) proposed using PECCP technology to delay the occurrence of galvanic corrosion in nickel-plated magnesium alloys. However, due to the limited photoelectrochemical performance of the Cu2O-modified TiO2 photoanode used in that patent, the effect of suppressing galvanic corrosion was relatively limited. To address this issue, this application employs a high-pressure hydrothermal reaction, successfully constructing a Bi2MoO6 / TiO2 composite photoanode with an S-type charge transfer mechanism through optimized control of the morphology and band structure of Bi2MoO6. Compared to existing Bi₂MoO₆ / TiO₂ composites, the Bi₂MoO₆ in this invention exhibits a directionally aggregated nanoparticle morphology, which can form a tight interfacial contact with the TiO₂ nanotube array, significantly reducing the interfacial charge transfer resistance. Simultaneously, by changing the pH value of the hydrothermal reaction system, precise control of the Bi₂MoO₆ bandgap shift is achieved, enabling it to form a compatible bandgap structure with TiO₂, overcoming the limitations of traditional type II heterojunctions. This Bi₂MoO₆ / TiO₂ composite material, through an S-type charge transfer mechanism, not only efficiently separates photogenerated electron-hole pairs and suppresses carrier recombination, but also retains the strong reducing properties of photogenerated electrons and the strong oxidizing properties of holes, significantly improving the photoelectrochemical performance of the composite photoanode. Coupling the composite photoanode of this invention with a nickel-magnesium alloy achieves highly efficient photogenerated cathodic protection for the nickel-magnesium alloy, significantly extending its resistance to galvanic corrosion. Currently, there are no patents or literature reports on the application of high-pressure hydrothermal technology to control the morphology and band structure of Bi2MoO6, construct S-type heterojunction Bi2MoO6 / TiO2 composite materials, and apply them to the photogenerated cathodic protection of nickel-magnesium alloys. Summary of the Invention

[0005] The purpose of this invention is to provide a Bi2MoO6 / TiO2 composite photoanode material, its preparation method, and its application, in order to solve the technical problems of low visible light utilization, slow photogenerated charge separation and migration dynamics, and insufficient long-term stability of TiO2 in the prior art.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a hydrothermal preparation method for Bi2MoO6 / TiO2 composite photoanode material, comprising the following steps: Step 1) After polishing the Ti foil, use the Ti foil as the working electrode and the platinum electrode as the counter electrode to connect to a DC power supply and perform anodic oxidation in constant potential mode. The resulting TiO2 is then washed, dried and annealed in sequence to obtain a TiO2 nanotube array. Step 2) After mixing and dispersing the molybdenum source, bismuth source, and water, the pH of the system is adjusted to obtain a mixed solution; Step 3) The mixture is mixed with the sheet-like TiO2 nanotube array and reacted, followed by washing and drying in sequence to obtain the Bi2MoO6 / TiO2 photoanode.

[0007] Furthermore, in step 1), the chemical polishing solution used for polishing includes NH4F, H2O2, H2O, and HNO3; The ratio of NH4F, H2O2, H2O and HNO3 used is 1.5~2g: 20~30mL: 8~15mL: 20~30mL; The polishing time is 60~120s.

[0008] Furthermore, in step 1), the voltage of the constant potential mode is 50~60V, and the anodizing time is 50~70min; The anodizing is carried out in an anodizing electrolyte, which includes NH4F, H2O and ethylene glycol, with the ratio of NH4F, H2O and ethylene glycol being 0.2~0.3 g : 2~5 mL : 35~40 mL.

[0009] Furthermore, in step 1), the drying temperature is 50~70℃, the annealing temperature is 400~500℃, and the annealing time is 1.5~3h; The annealing is carried out in an air atmosphere, and the heating rate from room temperature to the annealing temperature is 3~6℃ / min.

[0010] Furthermore, in step 2), the molybdenum source includes Na2MoO4. 2H2O, bismuth sources include Bi(NO3)3 5H2O; Based on the amount of molybdenum and bismuth, the ratio of molybdenum in the molybdenum source, bismuth in the bismuth source, and water is 1 mmol: 2 mmol: 50~80 mL. The dispersion is carried out under ultrasonic conditions for 20-40 minutes.

[0011] Furthermore, in step 2), the pH of the system is 6.0~10.0, and NH3 is used. H2O was used to adjust the pH of the system; Furthermore, in step 3), the reaction temperature is 150~180℃, and the reaction time is 10~14h; The drying temperature is 50~70℃, and the drying time is 8~10h.

[0012] This invention provides a Bi2MoO6 / TiO2 composite photoanode material prepared by the above preparation method.

[0013] The present invention also provides an application of the above-mentioned Bi2MoO6 / TiO2 composite photoanode material in protecting metals / alloys, using the Bi2MoO6 / TiO2 composite photoanode material as the anode and the metal / alloy to be protected as the cathode, to achieve photocathode protection of the metal / alloy under sunlight irradiation.

[0014] Furthermore, the alloy includes a nickel-magnesium plated alloy.

[0015] The beneficial effects of this invention are: This invention solves the following three problems: 1) Low visible light utilization of TiO2 alone. The light absorption range of Bi2MoO6 before and after TiO2 modification is broadened from 409 nm to 490 nm, and the photoresponse current density (4217 nm) is also improved. A / cm 2 It is approximately 10⁵ times that of pure TiO₂. A / cm 2 1) The charge transfer resistance of TiO2 modified with Bi2MoO6 is 40 times that of TiO2; 2) The photogenerated charge separation and migration kinetics of TiO2 are slow. Under illumination, the charge transfer resistance of TiO2 modified with Bi2MoO6 is 3.59 × 10⁻⁶. 3 Ω·cm 2 Reduced to 46.7 Ω·cm 2 3) Insufficient long-term stability of TiO2 alone. In the PECCP test of nickel-magnesium alloy, Bi2MoO6 / TiO2 photoanode can achieve stable protection of nickel-magnesium alloy for more than 96 hours, which is more than 4 times the protection time of TiO2 photoanode alone.

[0016] This invention utilizes heterojunction engineering techniques, employing a one-step hydrothermal reaction to deposit Bi2MoO6 onto the surface of a TiO2 nanotube array to modify TiO2, thereby obtaining a Bi2MoO6 / TiO2 composite photoanode with an S-shaped heterojunction structure. Compared to existing TiO2 modification techniques, the Bi2MoO6 / TiO2 composite photoanode prepared in this invention exhibits superior light absorption utilization, higher photogenerated carrier separation and migration efficiency, and stronger long-term stability, enabling rapid and efficient PECCP for nickel-magnesium alloy plating. Attached Figure Description

[0017] Figure 1This is a schematic diagram of the wiring of the nickel-magnesium alloy PECCP by photoanode in this invention; Figure 2 The top view morphology of (a) TiO2 photoanode and (b) Bi2MoO6 / TiO2 composite photoanode prepared in Example 1 is shown. Figure 3 (a) UV-Vis absorption spectrum and (b) photocurrent density curve under intermittent visible light irradiation for the Bi2MoO6 / TiO2 composite photoanode prepared in Example 2; Figure 4 (a) Nyquist plot and (b) Tafel plot of the Bi2MoO6 / TiO2 composite photoanode prepared in Example 2 after coupling with a nickel-magnesium alloy electrode; Figure 5 The OCP-t curves of the Bi2MoO6 / TiO2 composite photoanode prepared in Example 2 coupled with nickel-magnesium alloy electrodes plated for different times are shown: (a) nickel plating time 20 min, (b) nickel plating time 2 h. Detailed Implementation

[0018] This invention provides a hydrothermal preparation method for Bi2MoO6 / TiO2 composite photoanode material, comprising the following steps: Step 1) After polishing the Ti foil, use the Ti foil as the working electrode and the platinum electrode as the counter electrode to connect to a DC power supply and perform anodic oxidation in constant potential mode. The resulting TiO2 is then washed, dried and annealed in sequence to obtain a TiO2 nanotube array. Step 2) After mixing and dispersing the molybdenum source, bismuth source, and water, the pH of the system is adjusted to obtain a mixed solution; Step 3) The mixture is mixed with the sheet-like TiO2 nanotube array and reacted, followed by washing and drying to obtain the Bi2MoO6 / TiO2 photoanode.

[0019] In this invention, the purity of the Ti foil is preferably >99.999%.

[0020] In this invention, the Ti foil is ultrasonically cleaned in acetone, anhydrous ethanol and deionized water for 30 minutes in sequence to remove surface impurities, and a clean Ti foil is obtained for subsequent steps.

[0021] In this invention, in step 1), the chemical polishing solution used for polishing includes NH4F, H2O2, H2O and HNO3; The ratio of NH4F, H2O2, H2O and HNO3 is 1.5~2g:20~30mL:8~15mL:20~30mL, preferably 1.8g:24mL:10mL:24mL; The polishing time is 60~120s, preferably 80~100s.

[0022] In this invention, in step 1), the voltage of the constant potential mode is 50~60V, preferably 55V; the anodizing time is 50~70min, preferably 55~65min, and more preferably 60min. The anodizing is carried out in an anodizing electrolyte, which includes NH4F, H2O and ethylene glycol. The ratio of NH4F, H2O and ethylene glycol is 0.2~0.3 g : 2~5 mL : 35~40 mL, preferably 0.22 g : 3 mL : 37 mL.

[0023] In this invention, a high-voltage digital display stable power supply device is used, with Ti foil as the working electrode and platinum electrode as the counter electrode, which are respectively connected to the positive and negative terminals of a DC power supply.

[0024] In this invention, the washing process involves rinsing the TiO2 obtained by anodic oxidation with deionized water and anhydrous ethanol to remove residual electrolytes.

[0025] In this invention, in step 1), the drying temperature is 50~70℃, preferably 60℃; the annealing temperature is 400~500℃, preferably 450℃; and the annealing time is 1.5~3h, preferably 2h. The annealing is preferably carried out in an air atmosphere, and the heating rate from room temperature to the annealing temperature is 3~6℃ / min, preferably 4~5℃ / min.

[0026] In this invention, in step 2), the molybdenum source includes Na2MoO4. 2H₂O, preferably Na₂MoO₄ 2H2O; Bismuth sources include Bi(NO3)3 5H2O, preferably Bi(NO3)3 5H2O; The ratio of molybdenum in the molybdenum source to bismuth in the bismuth source and water, based on the amount of molybdenum and bismuth, is 1 mmol: 2 mmol: 50~80 mL, preferably 1 mmol: 2 mmol: 60 mL. The dispersion is carried out under ultrasonic conditions, and the ultrasonic time is 20-40 minutes, preferably 30 minutes.

[0027] In this invention, in step 2), the pH of the system is 6.0~10.0, preferably 6.0 or 10.0; preferably, NH3 is used. H2O was used to adjust the pH of the system; In this invention, in step 2), the reaction temperature is 150~180℃, preferably 160~170℃; the reaction time is 10~14h, preferably 12~13h. The drying temperature is 50~70℃, preferably 60℃; the drying time is 8~10h, preferably 9h.

[0028] This invention provides a Bi2MoO6 / TiO2 composite photoanode material prepared by the above preparation method.

[0029] The present invention also provides an application of the above-mentioned Bi2MoO6 / TiO2 composite photoanode material in protecting metals / alloys, using the Bi2MoO6 / TiO2 composite photoanode material as the anode and the metal / alloy to be protected as the cathode, to achieve photocathode protection of the metal / alloy under sunlight irradiation.

[0030] In this invention, the alloy includes a nickel-magnesium plated alloy, preferably a nickel-magnesium plated alloy.

[0031] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0032] Example 1

[0033] Ti foil (>99.999%) was sequentially immersed in acetone, anhydrous ethanol, and deionized water, and sonicated for 30 min to remove surface organic impurities. After sonication, the Ti foil was placed in a chemical polishing solution composed of NH4F (1.80 g), H2O2 (24.0 mL), H2O (10.0 mL), and HNO3 (24.0 mL) for 60 s to remove the surface oxide film and attached impurities. A high-voltage digital display stable power supply was then used, with Ti foil as the working electrode and a platinum electrode as the counter electrode, connected to the positive and negative terminals of a DC power supply, respectively. A mixture of 0.22 g NH4F, 3.0 mL H2O, and 37.0 mL ethylene glycol was used as the anodic oxidation electrolyte. The reaction was carried out at a constant potential of 55.0 V for 60 min. Afterward, the TiO2 obtained by anodic oxidation was rinsed with deionized water and anhydrous ethanol to remove residual electrolyte. The sample was then dried in a vacuum drying oven at 60 °C. Subsequently, the sample was placed in a tube furnace and heated to 450 °C at a rate of 5 °C / min under air atmosphere and held at that temperature for 2.0 h for annealing. After the tube furnace temperature cooled naturally, an anatase TiO2 nanotube array was finally obtained, which served as the photoanode.

[0034] Weigh out 1.0 mmol of Na2MoO4 in sequence. 2H2O and 2.0 mmol Bi(NO3)3 Dissolve 5H₂O in 60 mL of deionized water and sonicate for 30 min to mix. Then add NH₃ dropwise. Adjust the pH to 6.0 with H2O, and transfer the solution to the lining of a reactor with a TiO2 photoanode placed at an angle. Place the high-pressure reactor in an oven and react at 160℃ for 12.0 h. After cooling, wash with deionized water and then dry in a vacuum drying oven at 60℃ for 8.0 h to obtain the Bi2MoO6 / TiO2 photoanode.

[0035] Example 2

[0036] Ti foil (>99.999%) was sequentially immersed in acetone, anhydrous ethanol, and deionized water, and sonicated for 30 min to remove surface organic impurities. After sonication, the Ti foil was placed in a chemical polishing solution composed of NH4F (1.80 g), H2O2 (24.0 mL), H2O (10.0 mL), and HNO3 (24.0 mL) for 60 s to remove the surface oxide film and attached impurities. A high-voltage digital display stable power supply was then used, with Ti foil as the working electrode and a platinum electrode as the counter electrode, connected to the positive and negative terminals of a DC power supply, respectively. A mixture of 0.22 g NH4F, 3.0 mL H2O, and 37.0 mL ethylene glycol was used as the anodic oxidation electrolyte. The reaction was carried out at a constant potential of 55.0 V for 60 min. Afterward, the TiO2 obtained by anodic oxidation was rinsed with deionized water and anhydrous ethanol to remove residual electrolyte. The sample was then dried in a vacuum drying oven at 60 °C. Subsequently, the sample was placed in a tube furnace and heated to 450 °C at a rate of 5 °C / min under air atmosphere and held at that temperature for 2.0 h for annealing. After the tube furnace temperature cooled naturally, an anatase TiO2 nanotube array was finally obtained, which served as the photoanode.

[0037] Weigh out 1.0 mmol of Na2MoO4 in sequence. 2H2O and 2.0 mmol Bi(NO3)3 Dissolve 5H₂O in 60 mL of deionized water and sonicate for 30 min to mix. Then add NH₃ dropwise. Adjust the pH to 10.0 with H2O, and transfer the solution to a reactor liner with a TiO2 photoanode placed at an angle. Place the high-pressure reactor in an oven and react at 160℃ for 12.0 h. After cooling, wash with deionized water and then dry in a vacuum drying oven at 60℃ for 8.0 h to obtain the Bi2MoO6 / TiO2 photoanode.

[0038] Application Example 1

[0039] Using the Bi₂MoO₆ / TiO₂ photoanode obtained in Example 1, a dual-electrolysis cell coupling system was employed. The photoanode and the protected metal / alloy were placed in the photolysis cell and the corrosion cell, respectively. The photolysis cell contained a mixed solution of 0.1 mol / L Na₂S (hole sacrificial agent) and 0.2 mol / L NaOH, while the corrosion cell used a 3.5 wt% NaCl solution as the corrosion medium. Salt bridges containing saturated potassium chloride solution were inserted into both the photolysis and corrosion cells for coupling. The photoanode and the protected nickel-magnesium alloy were connected by copper wire. Under sunlight irradiation, the Bi₂MoO₆ / TiO₂ composite photoanode could achieve PECCP on the nickel-magnesium alloy.

[0040] Application Example 2

[0041] Using the Bi₂MoO₆ / TiO₂ photoanode obtained in Example 2, a dual-electrolysis cell coupling system was employed. The photoanode and the protected metal / alloy were placed in a photolysis cell and an etching cell, respectively. The photolysis cell contained a mixed solution of 0.1 mol / L Na₂S (hole sacrificial agent) and 0.2 mol / L NaOH, while the etching cell contained a 3.5 wt% NaCl solution as the etching medium. Salt bridges containing saturated potassium chloride solution were inserted into both the photolysis and etching cells for coupling. The photoanode and the protected metal / alloy were connected by copper wire. Under sunlight irradiation, the Bi₂MoO₆ / TiO₂ composite photoanode could achieve PECCP on nickel-magnesium alloy plating.

[0042] As can be seen from the above embodiments, the present invention provides a Bi2MoO6 / TiO2 composite photoanode material, its preparation method, and its application. Figure 2 The top view morphology of (a) TiO2 photoanode and (b) Bi2MoO6 / TiO2 composite photoanode prepared in Example 1 shows that the Bi2MoO6 / TiO2 composite photoanode prepared in this invention is composed of a bottom TiO2 nanotube array and a top Bi2MoO6 nanoparticle. Figure 3 (a) UV-Vis absorption spectrum and (b) photocurrent density curve under intermittent visible light irradiation of the Bi2MoO6 / TiO2 composite photoanode prepared in Example 2. The UV-Vis absorption spectrum and photocurrent density curve confirm that the Bi2MoO6 / TiO2 composite photoanode has excellent light absorption utilization and high photoelectric conversion efficiency. Figure 4 The figures (a) are Nyquist plots and (b) are Tafel plots of the Bi2MoO6 / TiO2 composite photoanode prepared in Example 2 after coupling with a nickel-magnesium alloy electrode. Figure 5The OCP-t curves of the Bi2MoO6 / TiO2 composite photoanode prepared in Example 2 and nickel-magnesium alloy electrodes plated for different times are shown. The electrochemical data show that the Bi2MoO6 / TiO2 composite photoanode has high efficiency in photogenerated carrier separation and transfer, excellent long-term PECCP performance for nickel-magnesium alloys, and can effectively inhibit metal corrosion.

[0043] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A hydrothermal preparation method for a Bi2MoO6 / TiO2 composite photoanode material, characterized in that, Includes the following steps: Step 1) After polishing the Ti foil, use the Ti foil as the working electrode and the platinum electrode as the counter electrode to connect to a DC power supply and perform anodic oxidation in constant potential mode. The resulting TiO2 is then washed, dried and annealed in sequence to obtain a TiO2 nanotube array. Step 2) After mixing and dispersing the molybdenum source, bismuth source, and water, the pH of the system is adjusted to obtain a mixed solution; Step 3) The mixture is mixed with the sheet-like TiO2 nanotube array and reacted, followed by washing and drying to obtain the Bi2MoO6 / TiO2 photoanode.

2. The hydrothermal preparation method of a Bi2MoO6 / TiO2 composite photoanode material according to claim 1, characterized in that, In step 1), the chemical polishing solution used for polishing includes NH4F, H2O2, H2O, and HNO3; The ratio of NH4F, H2O2, H2O and HNO3 used is 1.5~2g: 20~30mL: 8~15mL: 20~30mL; The polishing time is 60~120s.

3. The hydrothermal preparation method of a Bi2MoO6 / TiO2 composite photoanode material according to claim 1 or 2, characterized in that, In step 1), the voltage of the constant potential mode is 50~60V, and the anodizing time is 50~70min; The anodizing is carried out in an anodizing electrolyte, which includes NH4F, H2O and ethylene glycol, with the ratio of NH4F, H2O and ethylene glycol being 0.2~0.3 g: 2~5 mL: 35~40 mL.

4. The hydrothermal preparation method of a Bi2MoO6 / TiO2 composite photoanode material according to claim 3, characterized in that, In step 1), the drying temperature is 50~70℃, the annealing temperature is 400~500℃, and the annealing time is 1.5~3h; The annealing is carried out in an air atmosphere, and the heating rate from room temperature to the annealing temperature is 3~6℃ / min.

5. A hydrothermal preparation method for a Bi2MoO6 / TiO2 composite photoanode material according to claim 1 or 4, characterized in that, In step 2), the molybdenum source includes Na2MoO4. 2H2O, bismuth sources include Bi(NO3)3 5H2O; Based on the amount of molybdenum and bismuth, the ratio of molybdenum in the molybdenum source, bismuth in the bismuth source, and water is 1 mmol: 2 mmol: 50~80 mL. The dispersion is carried out under ultrasonic conditions for 20-40 minutes.

6. The hydrothermal preparation method of a Bi2MoO6 / TiO2 composite photoanode material according to claim 5, characterized in that, In step 2), the pH of the system is 6.0~10.0, and NH3 is used. H2O is used to adjust the pH of the system.

7. A hydrothermal preparation method for a Bi₂MoO₆ / TiO₂ composite photoanode material according to claim 1, 4, or 6, characterized in that, In step 3), the reaction temperature is 150~180℃ and the reaction time is 10~14h; The drying temperature is 50~70℃, and the drying time is 8~10h.

8. The Bi2MoO6 / TiO2 composite photoanode material prepared by the preparation method according to claims 1 to 7.

9. The application of the Bi2MoO6 / TiO2 composite photoanode material according to claim 8 in the protection of metals / alloys, characterized in that, Using Bi2MoO6 / TiO2 composite photoanode material as the anode and the protected metal / alloy as the cathode, photogenerated cathodic protection of the metal / alloy is achieved under sunlight irradiation.

10. The application of the Bi2MoO6 / TiO2 composite photoanode material according to claim 9 in the protection of metals / alloys, characterized in that, The alloy includes a nickel-magnesium plated alloy.

Images