Photoelectrode and Its Preparation Method and Application

Abstract

The present invention relates to the field of photoelectrochemical technology, and particularly to a photoanode and a preparation method thereof. The photoanode includes a semiconductor light absorber, a protective layer, and a cocatalyst layer; the protective layer is disposed on the surface of the semiconductor light absorber, and the cocatalyst layer is disposed on the surface of the protective layer; the protective layer is formed by alternately laminating at least two layers of a transition metal oxide layer and an atomic-level metal particle layer; both sides of the protective layer are transition metal oxide layers; the cocatalyst layer is an atomic-level metal particle layer. The photoanode has good photoelectrochemical conversion efficiency and stability, and its saturation current density value can reach 35 mA / cm<supgt;2< / supgt; and stably operate in strong acids and strong alkalis for more than 300 h.

Description

[0001] Field of the method

[0002] The present invention relates to the field of photoelectrochemical technology, and particularly to a photoanode and a preparation method and application thereof.

[0003] Background method

[0004] Solar energy is a renewable energy source that is inexhaustible. The energy radiated to the earth per second is about 1.47×10 14 Joules, which is equivalent to the energy released by burning 5 million tons of coal, far exceeding the total energy of all life on earth and having high utilization value. The ways to utilize solar energy to synthesize chemical substances and fuels mainly include three systems: photocatalysis, photovoltaic-electrocatalysis, and photoelectrochemistry. Among them, considering the technical readiness level, availability, economy, raw materials, etc., photoelectrochemistry has the best cost performance compared with the other two systems and has broad potential application prospects in the field of photochemical conversion.

[0005] The photoanode is the core component of the photoelectrochemical reaction system, which determines the photoelectrochemical reaction efficiency and the device life, and participates in functions such as light absorption, carrier generation, separation and transfer, and interfacial catalytic reaction. It can absorb light energy to generate electron-hole pairs, and then separate and transport the generated charge carriers to the semiconductor-electrolyte interface for reaction. Commonly used photoanode materials include transition metal oxide semiconductors (TiO2, CuO, etc.) and non-oxide semiconductors (silicon, nitrides, etc.). In order to improve the performance of the above materials, the improvement of the transition metal oxide semiconductor TiO2 mainly adopts the formation of composite materials with noble metals. For example, the Au / TiO2 composite structure forms a layer of Au film on the TiO2 nanotube and undergoes high-temperature annealing to improve the light absorption rate and photoelectric conversion properties. Another example is cobalt-ruthenium co-doped titanium dioxide, which is used for the absorption of light in different bands to expand the spectral response range of the material. The improvement of the non-oxide semiconductor Si mainly changes the structure of silicon. For example, taking crystalline silicon particles as raw materials, ethanol as a solvent, and polyvinylpyrrolidone as an additive, ultrathin crystalline silicon nanosheets are made through two steps of ultrasonic exfoliation and electrophoretic deposition to improve the carrier mobility. Another example is to deposit molybdenum disulfide and an active thin film layer on the silicon wafer to promote the generation of photogenerated carriers and reduce the impedance.

[0006] However, the above photoanodes cannot overcome the technical problem that the stability and conductivity of the photoanode are difficult to be compatible, which limits the application of the photoanode. Summary of the invention

[0007] Based on this, it is necessary to provide a photoanode for long-term stable and efficient conversion of solar energy to chemical energy, a preparation method thereof, and an application thereof.

[0008] In one aspect of the present invention, a photoanode is provided, which includes a semiconductor light absorber, a protective layer, and a cocatalyst layer; the protective layer is disposed on the surface of the semiconductor light absorber, and the cocatalyst layer is disposed on the surface of the protective layer;

[0009] The protective layer is formed by alternately laminating a transition metal oxide layer and an atomic-level metal particle layer at least twice; both sides of the protective layer are transition metal oxide layers;

[0010] The cocatalyst layer is an atomic-level metal particle layer.

[0011] In one embodiment, the semiconductor material in the semiconductor light absorber is a metal compound of Group VI A elements or a silicon-based semiconductor material, and includes the following technical features:

[0012] The metal compound of Group VI A elements is one or more of indium oxide, copper selenide, silver selenide, tin selenide, copper sulfide, and silver sulfide;

[0013] The silicon-based semiconductor material is an n+p-type or p+n-type silicon wafer, and the silicon wafer is polycrystalline silicon or single-crystalline silicon.

[0014] In one embodiment, the thickness of the transition metal oxide layer is 0.5 - 5 nm; the thickness of the atomic-level metal particle layer is 0.5 - 2 nm.

[0015] In one embodiment, the transition metal oxide in the transition metal oxide layer is one or more of titanium oxide, nickel oxide, cobalt oxide, copper oxide, cadmium oxide, tungsten oxide, zirconium oxide, iron oxide, and manganese oxide.

[0016] In one embodiment, the particle size of the metal particles in the atomic-level metal particle layer is 0.5 - 2 nm.

[0017] In one embodiment, the metal in the atomic-level metal particle layer is one or two of noble metals and transition metals.

[0018] In one embodiment, the noble metal is one or more of platinum, gold, silver, rhodium, palladium, and ruthenium; the transition metal is one or more of copper, iron, cobalt, nickel, titanium, and chromium.

[0019] An embodiment of the present invention also provides a method for preparing a photoanode, including:

[0020] (a) Preparing a semiconductor light absorber using a semiconductor material;

[0021] (b) Alternately depositing a transition metal oxide layer and an atomic-level metal particle layer on the semiconductor light absorber at least twice by magnetron sputtering to obtain a photoanode.

[0022] In one embodiment, step (b) includes:

[0023] Using a first transition metal as a sputtering target and oxygen as a sputtering gas, depositing the transition metal oxide layer on the surface of the semiconductor light absorber; then using a second transition metal and / or a noble metal as a sputtering target and an inert gas as a sputtering gas, depositing the atomic metal particle layer;

[0024] Repeating the deposition of the transition metal oxide layer and the atomic metal particle layer alternately at least twice to obtain the photoanode;

[0025] The first transition metal is one or more of titanium, nickel, cobalt, copper, cadmium, tungsten, zirconium, iron, and manganese; the second transition metal is one or more of copper, iron, cobalt, nickel, titanium, and chromium.

[0026] The present invention also provides the application of the above photoanode in water splitting, carbon dioxide reduction, nitrogen reduction, and nitrogen oxide reduction.

[0027] Beneficial effects:

[0028] (1) By providing multiple protective layers on the semiconductor light absorber, the protective layers include a transition metal oxide layer and an atomic metal particle layer, and the outermost atomic metal particle layer serves as a catalytic layer, which has high photoelectrochemical conversion efficiency and stability, and its saturation current density value can reach 35 mA / cm 2 , and it can operate stably in strong acids and alkalis for more than 300 h. The protective layer can not only conduct carriers but also play a protective role. The atomic particles in the catalytic layer can conduct carriers, and the multi-layer stacked protective layers can be effectively combined to jointly play the roles of carrier conduction and protection performance.

[0029] (2) The preparation method of the highly efficient and stable multi-layer structured photoanode of the present invention realizes the deposition and thickness control of the multi-layer structure through a magnetron sputtering method, which is simple in operation, low in cost, and has stable product quality, and can be applied to industrial production. Description of the drawings

[0030] Figure 1 Cross-sectional scanning electron microscope image of the (Cu-WO2) 18 / Si multi-layer photoanode provided for Example 1;

[0031] Figure 2 Scanning electron microscope image of the surface of the (Au-TiO2)5 / Si photoanode provided for Example 2;

[0032] Figure 3 Comparative analysis diagram of the (Au-TiO2)5 / Si, Au / Si, and TiO2 / Si photoanodes as photoanodes in the oxygen evolution reaction;

[0033] Figure 4 The comparative analysis diagrams of (Pt-CoO)5 / SnSe, SnSe, and Pt-CoO / SnSe photoanodes as photocathodes in the hydrogen evolution reaction;

[0034] Figure 5 The photoelectrochemical stability test of the (Pt-CoO)5-SnSe photoanode. Specific implementation manners

[0035] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0036] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the invention, the meaning of "a plurality" is at least two, such as two, three, etc., unless otherwise specifically defined. In the description of the present invention, the meaning of "several" is at least one, such as one, two, etc., unless otherwise specifically defined.

[0037] The terms "preferably", "more preferably", etc. in the present invention refer to the embodiments of the present invention that can provide certain beneficial effects in certain cases. However, in the same case or other cases, other embodiments may also be preferred. In addition, the description of one or more preferred embodiments does not imply that other embodiments are not available, nor is it intended to exclude other embodiments from the scope of the present invention.

[0038] When a numerical range is disclosed herein, the above range is considered continuous and includes the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to an integer, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0039] Unless otherwise specified, all percentages, fractions, and ratios are calculated based on the total mass of the compositions of the present invention. Unless otherwise specified, all masses of the listed components are given for the content of the active substances, and thus they do not include solvents or by-products that may be contained in commercially available materials. The term "mass percentage content" herein may be represented by the symbol "%" in this text. Unless otherwise specified, all molecular weights herein are weight-average molecular weights expressed in daltons. Unless otherwise specified, all formulations and tests herein occur in an environment of 25 °C. The terms "comprising", "including", "containing", "having" or other variants herein are intended to cover non-closed inclusion, and no distinction is made between these terms. The term "including" means that other steps and components can be added without affecting the final result. The compositions and methods / processes of the present invention comprise, consist of, and consist essentially of the essential elements and limitations described herein, as well as any additional or optional components, ingredients, steps, or limitations described herein. No distinction is made between the terms "efficacy", "performance", "effect", and "efficiency" in this text.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the description of the present invention herein are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0041] The present invention provides a photoanode, which comprises a semiconductor light absorber, a protective layer, and a cocatalyst layer; the protective layer is disposed on the surface of the semiconductor light absorber, and the cocatalyst layer is disposed on the surface of the protective layer;

[0042] The protective layer is formed by alternately laminating at least two layers of a transition metal oxide layer and an atomic-level metal particle layer; the two sides of the protective layer are transition metal oxide layers;

[0043] The cocatalyst layer is an atomic-level metal particle layer.

[0044] In a specific example, the semiconductor material in the semiconductor light absorber is a metal compound of Group VI A elements or a silicon-based semiconductor material, and specifically includes the following technical features:

[0045] The metal compound of Group VI A elements is one or more of indium oxide, copper selenide, silver selenide, tin selenide, copper sulfide, and silver sulfide.

[0046] The silicon-based semiconductor material is selected as an n + p-type or p + n-type silicon wafer, and the silicon wafer is polycrystalline silicon or single-crystalline silicon. Further, the n +The p-type silicon wafer is prepared by cleaning the n-type silicon wafer, coating the surface with an ethanol or aqueous solution of B2O3, and performing heat treatment in a vacuum or inert atmosphere at a temperature of 500 to 1000 °C; wherein the concentration of the ethanol or aqueous solution of B2O3 is 0.001 to 10 mol / L; the heat treatment time is 1 to 60 min. The p + The n-type silicon wafer is prepared by cleaning the p-type silicon wafer, coating the surface with an ethanol or aqueous solution of P2O5, and performing heat treatment in a vacuum or inert atmosphere at a temperature of 500 to 1000 °C; wherein the concentration of the ethanol or aqueous solution of P2O5 is 0.001 to 10 mol / L; the heat treatment time is 1 to 60 min.

[0047] In a specific example, the thickness of the transition metal oxide layer is 0.5 - 5 nm. When the protective layer is too thick, carriers cannot be transmitted, and when the protective layer is too thin, it is difficult to play a protective role; the thickness of the atomic-level metal particle layer is 0.5 - 2 nm.

[0048] In a specific example, the transition metal oxide in the transition metal oxide layer is one or more of titanium oxide, nickel oxide, cobalt oxide, copper oxide, cadmium oxide, tungsten oxide, zirconium oxide, iron oxide, and manganese oxide.

[0049] In a specific example, the particle size of the metal particles in the atomic-level metal particle layer is 0.5 - 2 nm.

[0050] In a specific example, the metal in the atomic-level metal particle layer is one or two of noble metals and transition metals. Further, the noble metal in the noble metal particles is one or more of platinum, gold, silver, rhodium, palladium, and ruthenium; the transition metal in the transition metal particles is one or more of copper, iron, cobalt, nickel, titanium, and chromium.

[0051] The present invention also provides a method for preparing a photoanode, including:

[0052] (a) Preparing a semiconductor light absorber using a semiconductor material;

[0053] (b) Alternately depositing a transition metal oxide layer and an atomic-level metal particle layer on the semiconductor light absorber at least twice by magnetron sputtering to obtain a photoanode.

[0054] In a specific example, the semiconductor material is n + p-type silicon wafer, and the step (a) includes:

[0055] Cleaning the n-type silicon wafer, coating the surface with an ethanol or aqueous solution of B2O3, and performing heat treatment in a vacuum or inert atmosphere at a temperature of 500 to 1000 °C to obtain n +p-type silicon wafer; wherein the ethanol or aqueous solution of B2O3 is 0.001 to 10 mol / L; the heat treatment time is 1 to 60 minutes; the n + The p-type silicon wafer is subjected to activation cleaning by a magnetron sputtering method.

[0056] In a specific example, the semiconductor material is p + n-type silicon wafer, and the step (a) includes:

[0057] After cleaning the p-type silicon wafer, a P2O5 ethanol or aqueous solution is coated on the surface, and heat treatment is carried out at a temperature of 500 to 1000 °C in a vacuum or inert atmosphere to obtain p + n-type silicon wafer; wherein the ethanol or aqueous solution of P2O5 is 0.001 to 10 mol / L; the heat treatment time is 1 to 60 minutes; the n + The p-type silicon wafer is subjected to activation cleaning by a magnetron sputtering method.

[0058] In a specific example, the semiconductor material is a metal compound of Group VI A elements, and the step (a) includes:

[0059] The conductive glass substrate is cleaned and subjected to activation cleaning by a magnetron sputtering method to obtain an activated glass substrate; using a high-purity metal compound of Group VI A elements as a target, high-purity argon gas as a sputtering gas, and depositing a metal compound film of Group VI A elements on the activated glass substrate by a magnetron sputtering method to obtain a semiconductor light absorber; the process parameters for the process of depositing the metal compound film of Group VI A elements are: chamber pressure 0.3 to 5.0 Pa, DC power 100 to 1000 W, and film thickness 0.1 to 10 μm.

[0060] In a specific example, the activation cleaning by the nuclear magnetic sputtering method includes: when the vacuum degree reaches 10 -4 Pa or less, high-purity inert gas is introduced as an ionization gas, the pulsed bias power supply is turned on, and plasma is generated by glow discharge for activation cleaning; the process parameters for the activation cleaning process are: pressure 3 to 10.0 Pa, pulsed bias 0 to -1200 V, and cleaning time 5 to 60 minutes.

[0061] In a specific example, the step (b) includes:

[0062] Using a first transition metal as a sputtering target and oxygen as a sputtering gas, depositing the transition metal oxide layer on the surface of the semiconductor light absorber; then using a second transition metal and / or a noble metal as a sputtering target and an inert gas as a sputtering gas, depositing the atomic-level metal particle layer;

[0063] The deposition of the transition metal oxide layer and the atomic-level metal particle layer is alternately repeated at least twice to obtain the photoanode;

[0064] The first transition metal is one or more of titanium, nickel, cobalt, copper, cadmium, tungsten, zirconium, iron, and manganese; the second transition metal is one or more of copper, iron, cobalt, nickel, titanium, and chromium.

[0065] In a specific example, the process parameters for depositing the transition metal oxide layer are: chamber pressure of 0.3 - 5.0 Pa, RF pulse power of 50 - 300 W, and film thickness of 1 - 50 nm.

[0066] In a specific example, the process parameters for depositing the atomic-level metal particle layer are: chamber pressure of 0.3 - 5 Pa, DC power of 20 - 100 W, and particle size of 0.5 - 2 nm.

[0067] The present invention further provides the application of the above-mentioned photoanode in water splitting, carbon dioxide reduction, and nitrogen and nitrogen oxide reduction.

[0068] The following are specific examples for further illustration.

[0069] Example 1

[0070] A (Cu-WO2) 18 / Si photoanode, and its preparation method is as follows:

[0071] Preparation of the semiconductor light absorber: Select a p-type Si(100) substrate as the base, ultrasonically clean it, and then coat the surface with a dilute solution of P2O5 ethanol with a concentration of 0.1 mol / L. Then, perform a high-temperature treatment at 900 °C for 10 min in a vacuum or inert atmosphere, and take it out after cooling to room temperature. Place the above-treated p + n silicon wafer in the sample stage of a magnetron sputtering coating machine. When the vacuum degree reaches below 10 -4 Pa, introduce high-purity argon gas as the ionization gas, adjust the chamber pressure to 8.6 Pa, turn on the pulsed bias power supply, adjust it to -900 V, generate plasma by glow discharge, and perform activation cleaning on the silicon surface. After the plasma activation is completed, turn off the bias.

[0072] (Cu-WO2) 18 / Si photoanode preparation: Select a high-purity tungsten target as the sputtering target, use high-purity oxygen as the sputtering gas, adjust the chamber pressure to 2.0 Pa, after depositing for 500 s, close the oxygen valve, open high-purity argon gas as the sputtering gas, adjust the chamber pressure to 1.0, switch the high-purity Cu target to the sputtering target, deposit for 5 s and then close it. This is one Cu-WO2 unit layer. Repeat this process 18 times to obtain a (Cu-WO2) 18 / Si multi-layer photoanode.

[0073] Example 2

[0074] An (Au-TiO2)5 / Si photoanode, and its preparation method is as follows:

[0075] Preparation of semiconductor light absorber: Select an n-type Si(100) substrate as the base. After ultrasonic cleaning, coat the surface of the n-type silicon wafer with a dilute solution of B2O3 ethanol or water with a concentration of 0.1 mol / L, and then perform high-temperature treatment at 900 °C for 10 min in a vacuum or inert atmosphere, and take it out after cooling to room temperature. Put the above-treated n + p silicon wafer into the sample stage of a magnetron sputtering coating machine. When the vacuum degree reaches below 10 -4 Pa, introduce high-purity argon gas as the ionization gas, adjust the chamber pressure to 8.6 Pa, turn on the pulsed bias power supply, adjust it to -1000 V, and generate plasma by glow discharge to activate and clean the silicon surface. After the plasma activation is completed, turn off the bias voltage.

[0076] Preparation of (Au-TiO2)5 / Si photoanode: Select a high-purity titanium target as the sputtering target, use high-purity oxygen as the sputtering gas, adjust the chamber pressure to 1.0 Pa, after depositing for 120 s, close the oxygen valve, open high-purity argon gas as the sputtering gas, adjust the chamber pressure to 1.0 Pa, convert the high-purity gold target to the sputtering target, deposit for 5 s and then close. This is one Au-TiO2 unit layer. Repeat this process 5 times to obtain an Au-TiO2 / Au-TiO2 / Au-TiO2 / Au-TiO2 / Au-TiO2 / Si multi-stage photoanode.

[0077] Example 3

[0078] A (Pt-CoO)5 / SnSe photoanode, and its preparation method is as follows:

[0079] Preparation of semiconductor light absorber: After ultrasonic cleaning, put the conductive glass ITO into the sample stage of a magnetron sputtering coating machine. When the vacuum degree reaches below 10 -4 Pa, introduce high-purity argon gas as the ionization gas, adjust the chamber pressure to 8.6 Pa, turn on the pulsed bias power supply, adjust it to -1000 V, and generate plasma by glow discharge to activate and clean the silicon surface. After the plasma activation is completed, turn off the bias voltage. After activation, use the magnetron sputtering method to prepare a SnSe compound thin film. Select a high-purity SnSe compound material as the sputtering target, use high-purity argon gas as the sputtering gas, apply a pulsed negative bias to the substrate, and the deposition parameters are: the chamber pressure is 0.4 Pa, the substrate bias is 0 V, and the deposition time is 60 min. After deposition, turn off the argon valve.

[0080] (Pt-CoO)5 / SnSe photoanode preparation: Select a high-purity cobalt target as the sputtering target, use high-purity oxygen as the sputtering gas, adjust the chamber pressure to 1.0 Pa, after depositing for 120 s, close the oxygen valve, open high-purity argon as the sputtering gas, adjust the chamber pressure to 1.0 Pa, convert the high-purity platinum target to the sputtering target, deposit for 5 s and then close. This is one Pt-CoO unit layer. Repeat this process 5 times to obtain the (Pt-CoO)5-SnSe photoanode material.

[0081] Comparative Example 1

[0082] TiO2 / Si photoanode preparation: Treat the silicon wafer according to step (1) of Example 2, and then deposit a TiO2 layer on the treated silicon wafer. Select a high-purity titanium target as the sputtering target, use high-purity oxygen as the sputtering gas, adjust the chamber pressure to 0.1 Pa, after depositing for 600 s, close the oxygen valve to obtain the TiO2-Si photoanode.

[0083] Comparative Example 2

[0084] Au / Si photoanode preparation:

[0085] Semiconductor light absorber preparation: Select an n-type Si(100) substrate as the base. After ultrasonic cleaning, clean the n-type silicon wafer, coat the surface with a dilute solution of B2O3 ethanol or water with a concentration of 0.1 mol / L, and then perform high-temperature treatment at 900 °C for 10 min in a vacuum or inert atmosphere, and take it out after cooling to room temperature. Put the above-treated n + p silicon wafer into the sample stage of the magnetron sputtering coating machine. When the vacuum degree reaches below 10 -4 Pa, introduce high-purity argon as the ionization gas, adjust the chamber pressure to 8.6 Pa, turn on the pulsed bias power supply, adjust it to -1000 V, and generate plasma by glow discharge to perform activation cleaning on the silicon surface. After the plasma activation is completed, turn off the bias.

[0086] Au / Si photoanode preparation: Open high-purity argon as the sputtering gas, adjust the chamber pressure to 1.0 Pa, convert the high-purity gold target to the sputtering target, deposit for 5 s and then close to obtain the Au / Si photoanode.

[0087] Comparative Example 3

[0088] Pt-CoO / SnSe photoanode preparation: The difference between this preparation method and that of Example 3 is that only one Pt-CoO unit layer is deposited without repetition. Other processes and parameters are exactly the same as those of Example 3.

[0089] Comparative Example 4

[0090] SnSe photoanode preparation: The preparation method is consistent with step 1 of Example 2.

[0091] Performance Test

[0092] The cross-sectional scanning electron microscopy image of the (Cu-WO2) / Si multilayer optoelectrode obtained in Example 1 is shown in the appendix 18 As shown, it can be seen from the figure that the thickness of each Cu-WO2 layer is about 5 nm, and there are 18 layers in total. Figure 1 As shown, it can be seen from the figure that the thickness of each Cu-WO2 layer is about 5 nm, and there are 18 layers in total.

[0093] The surface analysis of the (Au-TiO2)5 / Si optoelectrode obtained in Example 2 was carried out using a field emission scanning electron microscope, as shown in the appendix Figure 2 As shown, Au nanoparticles are evenly distributed on the surface of the optoelectrode, and the surface of the optoelectrode is dense without agglomeration of large particles and other phenomena.

[0094] The (Au-TiO2)5 / Si optoelectrode, TiO2 / Si optoelectrode, and Au / Si optoelectrode obtained in Example 2, Comparative Example 1, and Comparative Example 2 were used as photoanodes in the photoelectrochemical decomposition of water to produce oxygen. A three-electrode electrolytic cell (with the photoanode as the working electrode, a Pt wire as the counter electrode, and Ag / AgCl as the reference electrode) was carried out in a 1 M NaOH aqueous solution through a PEC 1000 black box system, and a solar simulator (xenon light source, FX300) was used to irradiate sunlight (AM 1.5G, 100 mW·cm -2 ). Before each measurement, a reference silicon solar cell and a reader for the irradiance of the solar simulator were used. Linear sweep voltammetry (JV) data without iR compensation were collected using a CHI 630E electrochemical workstation. During the measurement, the voltage was linearly scanned at a scan rate of 0.005 V·s -1 . The readings of Ag / AgCl were converted to RHE using the following relationship.

[0095] E(RHE) = E(Ag / AgCl) + 0.197 V + 0.059 × pH

[0096] As shown in the appendix Figure 3 As shown, compared with other optoelectrodes, the (Au-TiO2)5 / Si optoelectrode has excellent oxygen evolution potential and high photocurrent response, while the TiO2 / Si and Au / Si optoelectrodes have lower photocurrents in the photocatalytic oxygen evolution reaction.

[0097] The (Pt-CoO)5 / SnSe photoanodes, Pt-CoO / SnSe photoanodes, and SnSe photoanodes obtained in Example 3 and Comparative Examples 3 and 4 were used as photocathodes in the photocatalytic water splitting reaction for hydrogen production. A three-electrode electrolytic cell (with the photocathode as the working electrode, a Pt wire as the counter electrode, and Ag / AgCl as the reference electrode) was carried out in a 0.05 M H2SO4 aqueous solution through a PEC1000 black box system, and a solar simulator (xenon light source, FX300) was used to irradiate sunlight (AM 1.5G, 100 mW·cm -2 ). Before each measurement, linear sweep voltammetry (JV) data without iR compensation were collected using a reference silicon solar cell and a radiometer for the irradiance of the solar simulator, with or without illumination, using a CHI 630E electrochemical workstation. During the measurement, the voltage was linearly scanned at a scan rate of 0.005 V·s -1 . The readings of Ag / AgCl were converted to RHE using the following relationship.

[0098] E(RHE) = E(Ag / AgCl) + 0.197 V + 0.059 × pH

[0099] The results of the hydrogen evolution reaction are as Figure 4 shown. Among them, the (Pt-CoO)5 / SnSe photoanode has a lower hydrogen evolution potential, while the potential of the SnSe photoanode in the reaction exceeds 400 mV.

[0100] The (Pt-CoO)5 / SnSe photoanode obtained in Example 3 was subjected to a stability test. A three-electrode electrolytic cell (with the photocathode as the working electrode, a Pt wire as the counter electrode, and Ag / AgCl as the reference electrode) was carried out in a 0.05 M H2SO4 aqueous solution through a PEC 1000 black box system, and a solar simulator (xenon light source, FX300) was used to irradiate sunlight (AM1.5G, 100 mW·cm -2 ). Before each measurement, i-t data without iR compensation were collected using a reference silicon solar cell and a radiometer for the irradiance of the solar simulator, with or without illumination, using a CHI 630E electrochemical workstation. During the measurement, the operating voltage was 0 V vs RHE.

[0101] The results are as Figure 5 shown. It can be seen that the multi-level structure photoanode can operate stably for more than 300 h, reaching the industrial application level.

[0102] The method features of the above-described embodiments can be combined arbitrarily. For the sake of concise description, not all possible combinations of the method features in the above embodiments are described. However, as long as there is no contradiction in the combination of these method features, it should be considered as the scope described in this specification.

[0103] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A photoelectrode, characterized in that, The photoanode includes a semiconductor light absorber, a protective layer, and a cocatalyst layer; the protective layer is disposed on the surface of the semiconductor light absorber, and the cocatalyst layer is disposed on the surface of the protective layer; The protective layer is formed by alternately laminating at least two layers of a transition metal oxide layer and an atomic-level metal particle layer; the two sides of the protective layer are transition metal oxide layers; The cocatalyst layer is an atomic-level metal particle layer.

2. The optoelectrode according to claim 1, wherein The semiconductor material in the semiconductor light absorber is a metal compound of a Group VIA element or a silicon-based semiconductor material, and includes the following technical features: The metal compound of the Group VIA element is one or more of indium oxide, cuprous selenide, silver selenide, tin selenide, cuprous sulfide, and silver sulfide; The silicon-based semiconductor material is an n+p-type or p+n-type silicon wafer, and the silicon wafer is polycrystalline silicon or single-crystalline silicon.

3. The optoelectrode according to any one of claims 1-2, characterized in that The thickness of the transition metal oxide layer is 0.5 - 5 nm; the thickness of the atomic-level metal particle layer is 0.5 - 2 nm.

4. The optoelectrode according to any one of claims 1-2, characterized in that, The transition metal oxide in the transition metal oxide layer is one or more of titanium oxide, nickel oxide, cobalt oxide, copper oxide, cadmium oxide, tungsten oxide, zirconium oxide, iron oxide, and manganese oxide.

5. The optoelectrode according to any one of claims 1-2, characterized in that, The particle size of the metal particles in the atomic-level metal particle layer is 0.5 - 2 nm.

6. The optoelectrode according to any one of claims 1-2, characterized in that, The metal in the atomic-level metal particle layer is one or two of noble metals and transition metals.

7. The optoelectrode according to any one of claims 6, characterized in that, The noble metal is one or more of platinum, gold, silver, rhodium, palladium, and ruthenium; the transition metal is one or more of copper, iron, cobalt, nickel, titanium, and chromium.

8. A method for preparing a photoanode, characterized in that, Including: (a) Preparing a semiconductor light absorber using a semiconductor material; (b) Alternately depositing at least two layers of a transition metal oxide layer and an atomic-level metal particle layer on the semiconductor light absorber by magnetron sputtering to obtain a photoanode; Wherein the outermost layer deposited on the semiconductor light absorber is an atomic-level metal particle layer.

9. The method for preparing the optoelectrode according to claim 8, wherein, The step (b) includes: Using a first transition metal as a sputtering target and oxygen as a sputtering gas to deposit the transition metal oxide layer on the surface of the semiconductor light absorber; then using a second transition metal and / or a noble metal as a sputtering target and an inert gas as a sputtering gas to deposit the atomic-level metal particle layer; Alternately repeating the deposition of the transition metal oxide layer and the atomic-level metal particle layer at least two times to obtain the photoanode; The first transition metal is one or more of titanium, nickel, cobalt, copper, cadmium, tungsten, zirconium, iron, and manganese; the second transition metal is one or more of copper, iron, cobalt, nickel, titanium, and chromium.

10. Application of the photoanode according to any one of claims 1 - 7 in water splitting, carbon dioxide reduction, nitrogen reduction, and nitrogen oxide reduction.

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