Full-spectrum silicon-based composite photoanode array and its preparation method and application

Abstract

The full-spectrum silicon-based composite photoanode array disclosed in the present invention, its preparation method and application, include a silicon nanowire array, on which a conductive polymer is coated. The full-spectrum silicon-based composite photoanode array of the present invention, its preparation method and application, by coating a conductive polymer on a silicon nanowire array, the obtained composite photoanode can achieve absorption in the full spectrum range, and the composite photoanode has a high photocurrent density; and has mild synthesis conditions and is easy to achieve; has a good photoelectrochemical cathode protection effect on electronic metal materials, especially exhibits excellent protection effect in the dark state, and is expected to solve the technical bottleneck of the "three-proof technology" that restricts electronic equipment.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoanode and photoelectric cathode protection of metal materials in electronic components, and specifically relates to a full-spectrum silicon-based composite photoanode array. The present invention also relates to a preparation method of the full-spectrum silicon-based composite photoanode array. The present invention further relates to the application of the full-spectrum silicon-based composite photoanode array. Background Art

[0002] Corrosion is a major engineering problem faced by countries around the world. It is estimated that the average annual losses caused by metal corrosion in the United States and Europe are as high as 100 billion US dollars and 200 billion euros respectively (Progress in Organic Coatings, 2009, 64, 327). Studies have found that in 2014, my country's corrosion cost was 2127.82 billion yuan, accounting for about 3.34% of the gross domestic product (GDP) that year, which is equivalent to the per capita corrosion cost of 1,555 yuan borne by each of our citizens that year (China's Corrosion Cost, Science Press, 2017; npj Materials Degradation, 2017, 1, 4). If the corrosion cost is reduced by 0.1% through corrosion control, tens of billions of economic losses can be saved every year. Electronic components in electronic equipment have high metal density, small size and complex structure (Modern Protection Technology of Electronic Equipment, Electronic Mechanical Engineering, 2005, 21, 1), and there are many technical and protection difficulties. Photoelectrochemical cathodic protection has gradually become one of the most important new methods for metal corrosion protection at this stage (Nanotechnology, 2018, 29, 425701; Journal of Applied Electrochemistry, 2021, 1).

[0003] Photogenerated cathode protection technology uses the photoelectric conversion characteristics of semiconductors to provide photoelectrons for metals through the photoelectric conversion of semiconductors, so that the metals reach the polarization potential to achieve the purpose of corrosion prevention. The advantage of this technology is that it uses solar energy as energy, semiconductors as photoanodes, and the protected metals as cathodes. During the protection period, no new ion pollution will be generated, only electron transfer will occur, and it is green and environmentally friendly. The semiconductors only do photoelectric conversion and do not undergo chemical reactions themselves. In theory, they can be infinitely circulated. In addition, its advantages also lie in the ability to use solar energy to inhibit metal corrosion and not release metal ions into the environment. The basic principle is that under the irradiation of sunlight, electrons in the valence band of semiconductors absorb the energy of photons and are excited to the conduction band, thereby generating a pair of photogenerated holes and photogenerated electrons. Under the action of the space charge region at the interface between the semiconductor and the solution, the photogenerated holes migrate to the surface of the semiconductor material and react with the electron donors in the solution for oxidation, while the photogenerated electrons migrate to the surface of the metal material, thereby increasing the electron density of the protected metal and reducing the self-corrosion potential, thereby achieving the purpose of reducing the metal corrosion rate.

[0004] At present, researchers have studied a variety of semiconductor photoelectrodes, among which TiO2 is considered to be an ideal photoanode material for photogenerated cathode protection because of its stable physical and chemical properties, non-toxicity, low cost, and abundant reserves (Chemistry Materials, 2001, 13, 2838; Corrosion Science, 2020, 166, 108441). However, the wide band gap (3.2eV) of TiO2 makes its light absorption range narrow, inhibiting the absorption of visible light. In the dark state, photogenerated holes and electrons are very easy to recombine, resulting in the overall photogenerated cathode protection effect being limited. Silicon has abundant reserves, low cost, stable properties, and very mature purification technology. The band gap is only 1.1eV, and the light absorption range is wide. Further using chemical etching technology, array microstructures such as silicon nanowires, nanorods or nanotips are prepared on the silicon surface, which can fully absorb sunlight and show excellent photoelectrochemical properties. Silicon nanowire arrays have excellent anti-reflection properties, which can fully absorb sunlight and improve the utilization rate of solar energy; at the same time, the one-dimensional electron transfer path of silicon nanowires is conducive to the transmission of photogenerated electrons.

[0005] Poly(3,4-dioxyethyl)thiophene / p-styrenesulfonic acid (PEDOT:PSS) aqueous solution is the only conductive polymer that has been commercialized. In the field of solar photovoltaics, it is widely used as a hole transport layer, which can effectively consume photogenerated holes and greatly improve the photogenerated electron-hole separation efficiency of the device. In addition, the narrow-bandgap p-type organic semiconductor PEDOT:PSS, as a new energy storage material, realizes the charging and discharging process of photogenerated charges through reversible redox reactions, and is expected to play a continuous protective role on metals in the dark state. Based on the above problems, Si is used to replace TiO2 as the base material of the photoanode, and it is compounded with a conductive polymer that can consume holes and spontaneously store energy to simulate the marine corrosion environment. A "micro" photocathodic protection system for metal electronic materials based on Si photoanode will be constructed, which will be more in line with the uniqueness and actual situation of metal electronic material corrosion in shipborne electronic equipment. Summary of the invention

[0006] The purpose of the present invention is to provide a full-spectrum silicon-based composite photoanode array, which can achieve effective regulation of the photocurrent density of the composite photoanode array.

[0007] Another object of the present invention is to provide a method for preparing a full-spectrum silicon-based composite photoanode array, which has mild synthesis conditions and is easy to implement.

[0008] Another object of the present invention is to provide an application of a full-spectrum silicon-based composite photoanode array, which has good photocathode protection properties for metal materials of electronic components, and especially exhibits relatively excellent performance in a dark state.

[0009] The first technical solution adopted by the present invention is: a full-spectrum silicon-based composite photoanode array. By controlling the concentration of the conductive polymer solution and the spin coating speed and duration, the conductive polymer is coated on the silicon nanowire array. The obtained composite photoanode can achieve absorption in the full spectrum range and has a high photocurrent density of up to 2 mA cm -2 , the photocurrent density is at least 3 times higher than that of pure silicon array.

[0010] The second technical solution adopted by the present invention is: a method for preparing a full-spectrum silicon-based composite photoanode array, comprising the following steps:

[0011] Step 1: Preparation of silicon nanowire array (SiNW):

[0012] First, N-type silicon is cut into rectangular silicon wafers, and ultrasonic cleaning is performed in deionized water, anhydrous ethanol, acetone, anhydrous ethanol, and deionized water in sequence. Then, the silicon wafer is cleaned using the RCA standard cleaning method, and the silicon wafer is placed in piranha solution, APM solution, and HPM solution in sequence for water bath heating to remove organic pollutants, oxide films, particles, metals, etc. on the surface of the silicon wafer, and then rinsed with deionized water.

[0013] After rinsing, a silicon nanowire array (SiNW) is prepared by a top-down metal-assisted chemical etching method. At room temperature, the cleaned silicon wafer is placed in an HF solution. After being taken out, it is quickly placed in a silver plating solution, and then taken out after being heated in a water bath. Then the silicon wafer with silver particles on the surface is placed in the etching solution, heated in a water bath, and then taken out. After the corrosion is completed, it is placed in nitric acid to remove the residual silver particles, and then rinsed and soaked with water. After drying, a silicon nanowire array under metal-assisted chemical etching is obtained.

[0014] Step 2: Full-spectrum silicon-based composite photoanode array

[0015] Conductive polymer solutions of different dilution concentrations were prepared and mixed evenly with an oscillator. The silicon nanowire arrays were then placed in the mixed solutions of different dilution concentrations, taken out after soaking, and spin-coated using a desktop homogenizer. The spin-coated silicon wafers were placed in a tube furnace for heating to obtain a full-spectrum silicon-based composite photoanode array.

[0016] The third technical solution adopted by the present invention is: the application of a full-spectrum silicon-based composite photoanode array, which directly uses the full-spectrum silicon-based composite photoanode array as a photoanode and connects it to the protected metal through a wire. The metal is polarized and its corrosion potential is reduced by nearly 100 to 400 mV, especially in the dark state, showing excellent cathode continuous protection ability, thereby achieving a photogenerated cathode protection effect on the metal.

[0017] The beneficial effects of the present invention are: the full-spectrum silicon-based composite photoanode array of the present invention and its preparation method and application, by coating a conductive polymer on a silicon nanowire array, the obtained composite photoanode can achieve absorption within the full spectrum range, and the composite photoanode has a high photocurrent density; and the synthesis conditions are mild and easy to achieve; it has a good photoelectrochemical cathode protection effect on electronic metal materials, especially exhibits excellent protection effects in the dark state, and is expected to solve the technical bottleneck of the "three-proof technology" that restricts electronic equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a scanning electron microscope image (SEM) of the full-spectrum silicon-based composite photoanode array of the present invention;

[0019] Figure 2 It is the ultraviolet visible near infrared absorption spectrum (UVvis) of the full spectrum silicon-based composite photoanode array of the present invention;

[0020] Figure 3 This is a performance diagram of the full-spectrum silicon-based composite photoanode array of the present invention for photoelectrochemical cathode protection of electronic metal materials. DETAILED DESCRIPTION

[0021] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] The present invention provides a full-spectrum silicon-based composite photoanode array and a preparation method and application thereof, including:

[0023] Cut the silicon into 1cm*2cm rectangular silicon wafers, and place them in deionized water, anhydrous ethanol, acetone, anhydrous ethanol, and deionized water for ultrasonic cleaning for 5 to 15 minutes. Place the silicon wafers in the piranha solution in turn. APM Solution HPM Solution The silicon wafers were heated in a water bath at 40-70°C for 10-30 minutes to remove organic pollutants, oxide films, particles, metals and other pollutants on the surface of the silicon wafers, and then rinsed with deionized water. The silicon nanowire arrays were etched using a "top-down" metal ion-assisted chemical etching method. First, the AgNO3 concentration was set to 0.005-0.1 mol L -1 , HF concentration is 1.0~5.0mol L -1Silver plating solution. Measure 19.5 ml of deionized water and place it in a plastic beaker, put it in a suitable rotor, then add 85 mg of AgNO3, stir it thoroughly at room temperature for 1 hour, and then transfer the solution to a centrifuge tube. Add 3.5-5.5 ml of HF (40wt%) to the centrifuge tube, place the centrifuge tube on an oscillator, and shake the mixed solution for 5 minutes to obtain a silver plating solution. Then let the washed silicon wafer stand in a 2wt% HF solution for 2 minutes. After taking it out, quickly put it into the silver plating solution, heat it in a water bath at 70°C, and take it out after 5 minutes. The reducing Si-H bonds generated by the reaction of silicon with hydrofluoric acid in the silver plating solution will undergo a redox reaction with the oxidizing silver ions. As a cathode reaction, the resulting nano-Ag particles are deposited on the surface of the silicon wafer. Measure 18.5 ml of deionized water and place it in a centrifuge tube, then add 1 ml of a concentration of 0.1-1 mol L -1 H2O2 (30 wt%) and 5.5 ml of 1.0 to 5.0 mol L -1 HF (40wt%) was added, and the mixed solution was shaken for 5 minutes. The silicon wafer with silver particles on the surface obtained in the first step was placed in the etching solution, heated in a water bath at 50-70°C, and taken out after standing for 10-15 minutes. The obtained silicon wafer was placed in 20w%t nitric acid to remove the residual silver particles, and then rinsed and soaked with water. After drying, the silicon nanowire array under metal-assisted chemical etching was obtained.

[0024] The polythiophene solution was diluted 1 to 50 times and dripped on the silicon nanowire array for secondary spin coating at a speed of 100 to 300 rpm for 5 to 40 seconds, and then 500 to 2000 rpm for 20 to 120 seconds. The spin-coated silicon wafer was placed in a tube furnace and heated at 40 to 150 ° C for 5 min to 2 h in a helium atmosphere to obtain a polythiophene and silicon composite photoanode array. It was coupled with metal 304 stainless steel to form a double electrolytic cell system, with the anolyte being a 0.5M Na2SO4 solution and the catholyte being a 3.5% NaCl solution. A 300W high-pressure xenon lamp with a wavelength of ≥400nm was used as a visible light source to study the photocathodic protection performance of the photoanode for metals. The results showed that under illumination conditions, the metal corrosion potential was reduced to -290 to -400mV.

[0025] Through the above-mentioned method, the full-spectrum silicon-based composite photoanode array of the present invention and its preparation method and application can coat conductive polymers of different thicknesses on the silicon nanowire array by controlling the concentration of the conductive polymer solution and the spin coating speed and duration, and then effectively control the photocurrent density of the composite photoanode by controlling the coating thickness of the conductive polymer, so that a higher photocurrent density can be obtained, and the absorption range of light almost covers the ultraviolet, visible and near-infrared regions. Figure 1As shown, the prepared material presents a morphology in which the surface of the silicon array is coated with a conductive polymer coating, the height of the silicon array is about 16 microns, and the thickness of the coating is about 1 micron; Figure 2 As shown, the light absorption range of the conductive polymer and silicon composite photoanode array covers almost the entire spectrum, which is expected to improve the photocurrent density of the composite photoanode and its photocathode protection ability for electronic metal materials, especially the protection characteristics in the dark state; Figure 3 As shown in the figure, different concentrations of conductive polymer coatings exhibit different cathodic protection functions for metals. In the light-on state, the corrosion potential can be reduced to about -450mV, which is 200mV lower than the metal corrosion potential, realizing the photocathode protection function; in the light-off state, the potential of the protected metal does not immediately return to the corrosion potential, but takes a long time to return to the potential before the light is turned on, which is still lower than the corrosion potential of the metal. The experimental results show that the composite photoanode exhibits excellent photocathode protection ability in the dark state, effectively solving the technical bottleneck of the photocathode protection ability of the photoanode in the dark state.

[0026] Example 1

[0027] Cut the silicon into 1cm*2cm rectangular wafers, and place them in deionized water, anhydrous ethanol, acetone, anhydrous ethanol, and deionized water for ultrasonic cleaning for 5 minutes. Place the wafers in the piranha solution. APM Solution HPM Solution The silicon wafers were heated in a 70°C water bath for 20 minutes to remove organic pollutants, oxide films, particles, metals and other pollutants on the surface of the silicon wafers, and then rinsed with deionized water. The silicon nanowire arrays were etched using a "top-down" metal ion-assisted chemical etching method. First, the AgNO3 concentration was set to 0.005 mol L -1 , HF concentration is 1.0 mol L -1 Silver plating solution. Measure 19.5 ml of deionized water and place it in a plastic beaker, put it in a suitable rotor, then add 85 mg of AgNO3, stir it thoroughly at room temperature for 1 hour, and then transfer the solution to a centrifuge tube. Add 5.5 ml of HF (40wt%) to the centrifuge tube, place the centrifuge tube on an oscillator, and oscillate for 5 minutes to shake the mixed solution to obtain the silver plating solution. Then let the washed silicon wafer stand in a 2wt% HF solution for 2 minutes. After taking it out, quickly put it into the silver plating solution, heat it in a water bath to 70°C, and take it out after 5 minutes. The reducing Si-H bonds generated by the reaction of silicon with hydrofluoric acid in the silver plating solution will undergo a redox reaction with the oxidizing silver ions. As a cathode reaction, the resulting nano-Ag particles are deposited on the surface of the silicon wafer. Measure 18.5 ml of deionized water and place it in a centrifuge tube, then add 1 ml of a concentration of 0.1 mol L -1H2O2 (30wt%) and 5.5ml of 1.0molL -1 HF (40wt%) was added, and the mixed solution was shaken for 5 minutes to be evenly mixed. The silicon wafer with silver particles on the surface obtained in the first step was placed in the etching solution, heated to 70°C in a water bath, and taken out after standing for 10 minutes. The obtained silicon wafer was placed in 20wt% nitric acid to remove the residual silver particles, and then rinsed and soaked with water. After drying, the silicon nanowire array under metal-assisted chemical etching was obtained.

[0028] The polythiophene solution was drop-coated on the silicon nanowire array and subjected to secondary spin coating at a speed of 100 rpm for 20 seconds, and then 1000 rpm for 40 seconds. The spin-coated silicon wafer was placed in a tube furnace and heated at 40°C for 120 minutes in a helium atmosphere to obtain a polythiophene and silicon composite photoanode array. It was coupled with 304 stainless steel to form a dual electrolytic cell system, with the anolyte being a 0.5M Na2SO4 solution and the catholyte being a 3.5% NaCl solution. A 300W high-pressure xenon lamp with a wavelength of ≥400nm was used as a visible light source to study the photocathodic protection performance of the photoanode for metals. The results showed that under illumination conditions, the metal corrosion potential was reduced to -400mV.

[0029] Example 2

[0030] Cut the silicon into 1cm*2cm rectangular silicon wafers, and place them in deionized water, anhydrous ethanol, acetone, anhydrous ethanol, and deionized water for ultrasonic cleaning for 15 minutes. Place the silicon wafers in the piranha solution in turn. APM Solution HPM Solution The silicon wafers were heated in a 50°C water bath for 30 minutes to remove organic pollutants, oxide films, particles, metals and other pollutants on the surface of the silicon wafers, and then rinsed with deionized water. The silicon nanowire arrays were etched using a "top-down" metal ion-assisted chemical etching method. First, the AgNO3 concentration was set to 0.1 mol L -1 , HF concentration is 2.0 mol L -1Silver plating solution. Measure 19.5 ml of deionized water and place it in a plastic beaker, put it in a suitable rotor, then add 85 mg of AgNO3, stir it thoroughly at room temperature for 1 hour, and then transfer the solution to a centrifuge tube. Add 5.5 ml of HF (40wt%) to the centrifuge tube, place the centrifuge tube on an oscillator, and oscillate for 5 minutes to shake the mixed solution to obtain the silver plating solution. Then let the washed silicon wafer stand in a 2wt% HF solution for 2 minutes. After taking it out, quickly put it into the silver plating solution, heat it in a water bath to 70°C, and take it out after 5 minutes. The reducing Si-H bonds generated by the reaction of silicon with hydrofluoric acid in the silver plating solution will undergo a redox reaction with the oxidizing silver ions. As a cathode reaction, the resulting nano-Ag particles are deposited on the surface of the silicon wafer. Measure 18.5 ml of deionized water and place it in a centrifuge tube, then add 1 ml of a concentration of 1 mol L -1 of H2O2 (30 wt%) and 5.5 ml of 5.0 mol L -1 HF (40wt%) was added, and the mixed solution was shaken for 5 minutes to be evenly mixed. The silicon wafer with silver particles on the surface obtained in the first step was placed in the etching solution, heated to 70°C in a water bath, and taken out after standing for 10 minutes. The obtained silicon wafer was placed in 20wt% nitric acid to remove the residual silver particles, and then rinsed and soaked with water. After drying, the silicon nanowire array under metal-assisted chemical etching was obtained.

[0031] The polythiophene solution was diluted 50 times and dripped on the silicon nanowire array for secondary spin coating at a speed of 100 rpm for 30 seconds, and then 800 rpm for 30 seconds. The spin-coated silicon wafer was placed in a tube furnace and heated at 100°C for 30 minutes in a helium atmosphere to obtain a polythiophene and silicon composite photoanode array. It was coupled with metal 304 stainless steel to form a double electrolytic cell system, with the anolyte being a 0.5M Na2SO4 solution and the catholyte being a NaCl solution with a mass concentration of 3.5%. A 300W high-pressure xenon lamp with a wavelength of ≥400nm was used as a visible light source to study the photocathodic protection performance of the photoanode for metals. Under illumination conditions, the metal corrosion potential was reduced to -310mV.

[0032] Example 3

[0033] Cut the silicon into 1cm*2cm rectangular wafers, and place them in deionized water, anhydrous ethanol, acetone, anhydrous ethanol, and deionized water for ultrasonic cleaning for 5 minutes. Place the wafers in the piranha solution. APM Solution HPM Solution The silicon wafers were heated in a 40°C water bath for 10 minutes to remove organic pollutants, oxide films, particles, metals and other pollutants on the surface of the silicon wafers, and then rinsed with deionized water. The silicon nanowire arrays were etched using a "top-down" metal ion-assisted chemical etching method. First, the AgNO3 concentration was set to 0.04 mol L -1 , HF concentration is 4.0 mol L -1 Silver plating solution. Measure 19.5 ml of deionized water and place it in a plastic beaker, put it in a suitable rotor, then add 85 mg of AgNO3, stir it thoroughly at room temperature for 1 hour, and then transfer the solution to a centrifuge tube. Add 5.5 ml of HF (40wt%) to the centrifuge tube, place the centrifuge tube on an oscillator, and oscillate for 5 minutes to shake the mixed solution to obtain the silver plating solution. Then let the washed silicon wafer stand in a 2wt% HF solution for 2 minutes. After taking it out, quickly put it into the silver plating solution, heat it in a water bath to 70°C, and take it out after 5 minutes. The reducing Si-H bonds generated by the reaction of silicon with hydrofluoric acid in the silver plating solution will undergo a redox reaction with the oxidizing silver ions. As a cathode reaction, the resulting nanosilver particles are deposited on the surface of the silicon wafer. Measure 18.5 ml of deionized water and place it in a centrifuge tube, then add 1 ml of a concentration of 0.5 mol L -1 H2O2 (30wt%) and 5.5ml of 4.0molL -1 HF (40wt%) was added, and the mixed solution was shaken for 5 minutes. The silicon wafer with silver particles on the surface obtained in the first step was placed in the etching solution, heated to 50°C in a water bath, and taken out after standing for 15 minutes. The obtained silicon wafer was placed in 20wt% nitric acid to remove the residual silver particles, and then rinsed and soaked with water. After drying, the silicon nanowire array under metal-assisted chemical etching was obtained.

[0034] The polythiophene solution was drop-coated on the silicon nanowire array and subjected to secondary spin coating at a speed of 200 rpm for 40 seconds, then 500 rpm for 20 seconds. The spin-coated silicon wafer was placed in a tube furnace and heated at 100°C for 30 minutes in a helium atmosphere to obtain a polythiophene and silicon composite photoanode array. It was coupled with metal 304 stainless steel to form a double electrolytic cell system, with the anolyte being a 0.5M Na2SO4 solution and the catholyte being a 3.5% NaCl solution. A 300W high-pressure xenon lamp with a wavelength of ≥400nm was used as a visible light source to study the photocathodic protection performance of the photoanode for metals. The results showed that under illumination conditions, the metal corrosion potential was reduced to -400mV.

[0035] Example 4

[0036] Cut the silicon into 1cm*2cm rectangular silicon wafers, and place them in deionized water, anhydrous ethanol, acetone, anhydrous ethanol, and deionized water for ultrasonic cleaning for 15 minutes. Place the silicon wafers in the piranha solution in turn. APM Solution HPM Solution The silicon wafers were heated in a 60°C water bath for 20 minutes to remove organic pollutants, oxide films, particles, metals and other pollutants on the surface of the silicon wafers, and then rinsed with deionized water. The silicon nanowire arrays were etched using a "top-down" metal ion-assisted chemical etching method. First, the AgNO3 concentration was set to 0.03 mol L -1 , HF concentration is 5.0 mol L -1 Silver plating solution. Measure 19.5 ml of deionized water and place it in a plastic beaker, put it in a suitable rotor, then add 85 mg of AgNO3, stir it thoroughly at room temperature for 1 hour, and then transfer the solution to a centrifuge tube. Add 3.5 ml of HF (40wt%) to the centrifuge tube, place the centrifuge tube on an oscillator, and oscillate for 5 minutes to shake the mixed solution to obtain a silver plating solution. Then let the washed silicon wafer stand in a 2wt% HF solution for 2 minutes. After taking it out, quickly put it into the silver plating solution, heat it in a water bath to 70°C, and take it out after 5 minutes. The reducing Si-H bonds generated by the reaction of silicon with hydrofluoric acid in the silver plating solution will undergo a redox reaction with the oxidizing silver ions. As a cathode reaction, the resulting nanosilver particles are deposited on the surface of the silicon wafer. Measure 18.5 ml of deionized water and place it in a centrifuge tube, then add 1 ml of a concentration of 0.5 Mol L -1 H2O2 (30wt%) and 5.5ml of 4.0molL -1 HF (40wt%) was added, and the mixed solution was shaken for 5 minutes. The silicon wafer with silver particles on the surface obtained in the first step was placed in the etching solution, heated to 50°C in a water bath, and taken out after standing for 15 minutes. The obtained silicon wafer was placed in 20wt% nitric acid to remove the residual silver particles, and then rinsed and soaked with water. After drying, the silicon nanowire array under metal-assisted chemical etching was obtained.

[0037] The polythiophene solution was diluted 20 times and drop-coated on the silicon nanowire array for secondary spin coating at a speed of 100 rpm for 40 seconds, and then 600 rpm for 30 seconds. The spin-coated silicon wafer was placed in a tube furnace and heated at 100°C for 30 minutes in a helium atmosphere to obtain a polythiophene and silicon composite photoanode array. It was coupled with metal 304 stainless steel to form a double electrolytic cell system, with the anolyte being a 0.5M Na2SO4 solution and the catholyte being a 3.5% NaCl solution. A 300W high-pressure xenon lamp with a wavelength of ≥400nm was used as a visible light source to study the photocathodic protection performance of the photoanode for metals. Under illumination conditions, the metal corrosion potential was reduced to -290mV.

[0038] Example 5

[0039] Cut the silicon into 1cm*2cm rectangular wafers, and place them in deionized water, anhydrous ethanol, acetone, anhydrous ethanol, and deionized water for ultrasonic cleaning for 5 minutes. Place the wafers in the piranha solution. APM Solution HPM Solution The silicon wafers were heated in a 60°C water bath for 20 minutes to remove organic pollutants, oxide films, particles, metals and other pollutants on the surface of the silicon wafers, and then rinsed with deionized water. The silicon nanowire arrays were etched using a "top-down" metal ion-assisted chemical etching method. First, the AgNO3 concentration was set to 0.03 mol L -1 , HF concentration is 5.0 mol L -1 Silver plating solution. Measure 19.5 ml of deionized water and place it in a plastic beaker, put it in a suitable rotor, then add 85 mg of AgNO3, stir it thoroughly at room temperature for 1 hour, and then transfer the solution to a centrifuge tube. Add 3.5 ml of HF (40wt%) to the centrifuge tube, place the centrifuge tube on an oscillator, and oscillate for 5 minutes to shake the mixed solution to obtain a silver plating solution. Then let the washed silicon wafer stand in a 2wt% HF solution for 2 minutes. After taking it out, quickly put it into the silver plating solution, heat it in a water bath to 70°C, and take it out after 5 minutes. The reducing Si-H bonds generated by the reaction of silicon with hydrofluoric acid in the silver plating solution will undergo a redox reaction with the oxidizing silver ions. As a cathode reaction, the resulting nanosilver particles are deposited on the surface of the silicon wafer. Measure 18.5 ml of deionized water and place it in a centrifuge tube, then add 1 ml of a concentration of 0.5 Mol L -1 H2O2 (30wt%) and 5.5ml of 4.0molL -1 HF (40wt%) was added, and the mixed solution was shaken for 5 minutes. The silicon wafer with silver particles on the surface obtained in the first step was placed in the etching solution, heated to 50°C in a water bath, and taken out after standing for 15 minutes. The obtained silicon wafer was placed in 20wt% nitric acid to remove the residual silver particles, and then rinsed and soaked with water. After drying, the silicon nanowire array under metal-assisted chemical etching was obtained.

[0040] The polythiophene solution was diluted 1 times and dripped on the silicon nanowire array for secondary spin coating at a speed of 300 rpm for 5 seconds, and then 2000 rpm for 120 seconds. The spin-coated silicon wafer was placed in a tube furnace and heated at 150°C for 5 minutes in a helium atmosphere to obtain a polythiophene and silicon composite photoanode array. It was coupled with metal 304 stainless steel to form a double electrolytic cell system, with the anolyte being a 0.5M Na2SO4 solution and the catholyte being a NaCl solution with a mass concentration of 3.5%. A 300W high-pressure xenon lamp with a wavelength of ≥400nm was used as a visible light source to study the photocathodic protection performance of the photoanode for metals. Under illumination conditions, the metal corrosion potential was reduced to -390mV.

Claims

1. A method for preparing a full-spectrum silicon-based composite photoanode array, characterized in that: The following steps are involved: Step 1: Preparation of silicon nanowire arrays First, N-type silicon is cut into rectangular silicon wafers, which are then placed in deionized water, anhydrous ethanol, acetone, anhydrous ethanol, and deionized water for ultrasonic cleaning. Then, the silicon wafers are placed in piranha solution, APM solution, and HPM solution for water bath heating for cleaning. Afterwards, the silicon wafers are rinsed with deionized water. The rinsed silicon wafer is placed in the HF solution at room temperature, and then taken out and placed in the silver plating solution. The silver plating solution includes AgNO3 and HF, and the concentration of AgNO3 is 5-100 mmol L -1 , HF concentration is 1~5 mol L -1 , and then take it out after heating in a water bath; then put the silicon wafer covered with silver particles into an etching solution, which includes H2O2 and HF, and the concentration of H2O2 is 0.1-1 mol L -1 , HF concentration is 1~5 mol L -1 , heat in a water bath and then take it out after standing; after the corrosion is completed, place it in nitric acid to remove the remaining silver particles; Then rinse and soak with water, and after drying, a silicon nanowire array under metal-assisted chemical etching is obtained; Step 2: Full-spectrum silicon-based composite photoanode array A conductive polymer solution is prepared, wherein the conductive polymer in the conductive polymer mixed solution is polythiophene, polyaniline or polypyrrole, and the conductive polymer mixed solution is diluted with anhydrous ethanol and / or water as a diluent, and the volume ratio of the conductive polymer to the diluent is 1 to 50; then a silicon nanowire array is placed in the conductive polymer solution, taken out after soaking, and then spin-coated, with a spin-coating speed of 100 to 2000 rpm for 5 to 120 seconds, and heated after spin-coating to obtain a full-spectrum silicon-based composite photoanode array, the heating is located in a tubular furnace, the heating temperature is 40 to 150°C, the time is 5 minutes to 2 hours, and the atmosphere is an inert atmosphere.

2. The full-spectrum silicon-based composite photoanode array prepared by the method for preparing the full-spectrum silicon-based composite photoanode array as claimed in claim 1.

3. The full-spectrum silicon-based composite photoanode array according to claim 2, characterized in that: The coating thickness of the conductive polymer is 1 micron.

4. The use of the full-spectrum silicon-based composite photoanode array as claimed in claim 2, characterized in that: The full-spectrum silicon-based composite photoanode array is directly used as a photoanode and connected to the protected metal through a wire.

Images