Gold-modified lanthanum ferrite-based semiconductor film photoelectrochemical water decomposition photo-anode and preparation method thereof

Abstract

The invention relates to a gold-modified lanthanum ferrite-based semiconductor film photoelectrochemical water decomposition photo-anode and a preparation method thereof, and belongs to the field of photoelectrochemical water decomposition hydrogen production. The photoanode comprises a transparent conductive substrate, a wide bandgap semiconductor layer located on the conductive substrate, an Au nanoparticle layer located on the wide bandgap semiconductor layer, and a LaFeO3 absorption layer located on the Au nanoparticle layer. According to the invention, the p-type LaFeO3 semiconductor is applied to the construction of the photo-anode through the design of a special structure, the light absorption range of the photo-anode is expanded, the photocurrent density of the photo-anode is enhanced, the photoelectric conversion efficiency of the photo-anode is improved by combining the wide bandgap semiconductor TiO2 and utilizing the local surface plasmon effect of Au nanoparticles, and the photoelectric conversion efficiency of the photo-anode is improved. The method is of great significance to improvement of the overall light-to-hydrogen conversion efficiency of an electrode system. And the photoanode is simple and convenient to prepare, can be produced on a large scale, is low in raw material cost and environment-friendly, and is expected to be commercially applied to the field of photoelectrochemical water decomposition.

Description

Technical Field

[0001] The invention relates to the field of photoelectrochemical water decomposition hydrogen production, and in particular to an Au-modified LaFeO3-based semiconductor film photoelectrochemical water decomposition photoanode and a preparation method thereof. Background Art

[0002] Hydrogen energy is pollution-free and has high energy density. It is the most promising emerging energy to replace traditional fossil energy. At present, the main methods of hydrogen production include fossil energy reforming hydrogen production, water electrolysis hydrogen production, biomass hydrogen production and photolysis water hydrogen production. Fossil energy reforming hydrogen production will produce carbon dioxide emissions, which is not conducive to the realization of carbon neutrality goals; water electrolysis hydrogen production has high energy consumption and high cost; biomass hydrogen production still needs to be further improved; photolysis water hydrogen production directly uses solar energy and is a very potential pollution-free hydrogen production technology. Photoelectrocatalytic hydrogen production, as a key technology for photolysis water hydrogen production, has obvious advantages among many hydrogen production methods. It can directly convert solar energy into chemical energy. Its principle is to use photosensitive semiconductors to generate electron-hole pairs when exposed to sunlight, and transfer carriers into the electrolyte under the assistance of an external bias voltage to carry out water decomposition reaction. The external bias voltage uses the electric field to promote electron migration, which can hinder the recombination of photogenerated carriers and is more efficient than pure photocatalysis.

[0003] In conventional photoelectrocatalytic systems, the core is the working electrode. Generally, n-type semiconductors are used as photoanodes for the production of oxygen, while p-type semiconductors are used as photocathodes for the production of hydrogen. Both types of photoelectrodes are extremely important, but the photoanode is the oxidation reaction of water to produce oxygen. The kinetics of this reaction are relatively slow and it is the bottleneck step of the entire water decomposition reaction. There are many choices of photoanode materials at present. Metal oxides such as ZnO have good light absorption ability and chemical stability, but usually have disadvantages such as low carrier mobility and narrow light absorption range. Carbon-based materials such as graphene and carbon nanotubes have good conductivity and chemical stability, but are poor in light absorption efficiency. Semiconductor materials such as CdS have strong light absorption ability, but are often accompanied by the risk of toxicity and harm, and are more susceptible to photocorrosion under light.

[0004] Solid oxides such as perovskite materials are widely used in photoanodes because they have a wide light absorption range, higher carrier mobility than many traditional materials, and can adjust the photoelectric properties by changing the chemical composition. The raw materials are usually abundant and low-cost, and have long-term stability. Lanthanum ferrite (LaFeO3) is a typical perovskite structure material that perfectly possesses the above advantages. Its raw materials are abundant and low-cost, the synthesis method is relatively simple, and it is easy to mass produce. La and Fe are relatively stable under normal conditions and have little harm to the environment and human health. LaFeO3 is a p-type semiconductor with a band gap energy of 2.1 to 2.2 eV, which is a suitable band structure. LaFeO3-based photoanodes have a wide light absorption range and can effectively absorb visible light. Lanthanum ferrite has good electron-hole separation and migration capabilities after photoexcitation, all of which help to improve the photoelectric conversion efficiency. In addition, LaFeO3-based photoanodes have good anti-photocorrosion properties, excellent redox stability and good electrochemical properties, which makes them very promising in the field of photoelectrochemical water splitting. However, the performance of LaFeO3 single material is limited, and special structural design is needed in combination with other materials to further improve its photoelectrochemical performance.

[0005] Thanks to the localized surface plasmon effect (LSPR), precious metal nanoparticles such as gold (Au) exhibit strong broadband light absorption characteristics in the visible light region. Driven by the external electromagnetic field, free electrons near the surface of precious metal nanoparticles can undergo periodic oscillations, localizing light within a few nanometers around the metal nanoparticles, thereby enhancing the light absorption efficiency of the surrounding semiconductors. In addition, the local electromagnetic field enhancement effect generated by the precious metals will promote the band gap transition of nearby semiconductors, thereby generating more photogenerated electron-hole pairs. The driving effect of the local enhanced electromagnetic field of the precious metals can accelerate the rapid separation of photogenerated electron-hole pairs, thereby improving the photoelectric conversion efficiency of the photoelectrode.

[0006] Therefore, under the action of LSPR effect, through special structural design and modification of Au nanoparticles, the light absorption capacity of LaFeO3-based photoanode can be enhanced, its light absorption range can be expanded, and its photoelectric conversion efficiency can be improved. In addition, the entire preparation process of Au-modified LaFeO3-based photoanode is simple and convenient, and large-scale production can be achieved. Although Au is expensive, the nano-level dosage and large-scale production can greatly reduce the cost of Au, which is of great significance to the improvement of photoanode performance and the overall light-to-hydrogen conversion efficiency of the electrode system. Summary of the invention

[0007] In view of the problems existing in the prior art, the purpose of the present invention is to provide an Au-modified LaFeO3-based semiconductor thin film photoelectrochemical water splitting photoanode and a preparation method thereof. The photoanode uses LaFeO3 material as the main absorption layer, and a special structure of a TiO2 layer, an Au nanoparticle layer, and a LaFeO3 absorption layer is sequentially constructed on a transparent conductive substrate to obtain a photoanode with strong light absorption ability, high photoelectric conversion efficiency, and strong working stability. The photoanode is used as the working electrode of a three-electrode system, further improving the overall photoelectric conversion efficiency and stability of the electrode system under electrical assistance.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] The invention discloses an Au-modified LaFeO3-based semiconductor thin film photoelectrochemical water splitting photoanode. The Au-modified LaFeO3-based photoanode comprises a transparent conductive substrate, a wide bandgap semiconductor layer on the conductive substrate, an Au nanoparticle layer on the wide bandgap semiconductor layer, and a LaFeO3 absorption layer on the Au nanoparticle layer. The structure of the photoanode is LaFeO3 / Au / TiO2 / FTO. The structure of the Au-modified LaFeO3-based photoanode with better performance after improvement is LaFeO3 / TiO2 / Au / TiO2 / FTO.

[0010] Furthermore, the transparent conductive substrate is a FTO glass sheet.

[0011] Furthermore, the wide bandgap semiconductor layer is a TiO2 layer.

[0012] Furthermore, the thickness of the wide bandgap semiconductor layer is 400-600 nm.

[0013] Furthermore, the thickness of the Au nanoparticle layer is 6 nm.

[0014] Furthermore, the Au nanoparticles have a particle size of 15 to 50 nm.

[0015] Furthermore, the LaFeO3 absorption layer is a double layer.

[0016] Furthermore, the overall thickness of the LaFeO3 absorption layer is 400-600 nm.

[0017] Furthermore, the Au-modified LaFeO3-based semiconductor thin film photoelectrochemical water splitting photoanode is a working electrode in a three-electrode system, and the electrode system also includes an Ag / AgCl reference electrode, a Pt counter electrode, and an electrochemical workstation, which provides a voltage source, and the working electrode, reference electrode and counter electrode are connected to the electrochemical workstation.

[0018] The present invention also provides a method for preparing an Au-modified LaFeO3-based semiconductor thin film photoelectrochemical water splitting photoanode, comprising the following steps:

[0019] Step 1, using liquid deposition technology and annealing technology to grow TiO2 thin film on FTO;

[0020] Step 2, using vacuum evaporation technology and annealing technology to prepare the Au nanoparticle layer;

[0021] Step three, preparing the LaFeO3 thin film layer by using sol-gel spin coating and annealing technology.

[0022] In view of the technical problems existing in the above-mentioned prior art and the difficulty of solving the problems, the technical solutions to be protected by the present invention and the results and data in the research and development process are closely combined to analyze in detail and deeply how the technical solutions of the present invention solve the technical problems and some creative technical effects brought about after solving the problems. The advantages and positive effects of the technical solutions to be protected by the present invention are:

[0023] The Au-modified LaFeO3-based photoanode of the present invention uses LaFeO3 material as an absorption layer, and constructs a photoanode with a special structure by sequentially stacking a TiO2 layer, an Au nanoparticle layer, and a LaFeO3 absorption layer on a transparent conductive substrate, thereby realizing the application of LaFeO3 material as the main absorption layer in the photoanode.

[0024] The testing method of the present invention utilizes the enhanced electromagnetic field of localized surface plasmons to improve the light absorption efficiency of the photoanode, increase the number of electron-hole pairs, and achieve enhancement of the photocurrent density.

[0025] This method obtains high-quality Au nanoparticles with uniform particle size on a TiO2 film with adjustable thickness, and utilizes the localized surface plasmons and enhanced electromagnetic field generated by the Au nanoparticles to improve the light absorption efficiency of the LaFeO3-based photoanode, expand its light absorption range, and accelerate the separation of photogenerated electron-hole pairs, thereby improving the photocurrent density and photoelectric conversion efficiency of the photoanode in the wavelength range of 500 to 700 nm.

[0026] Compared with the prior art, the beneficial effects of the present invention are embodied in:

[0027] First, the Au-modified LaFeO3-based photoanode has higher light absorption efficiency, wider light absorption range, and higher photoelectric conversion efficiency, as described below:

[0028] 1) LaFeO3 has good electron-hole separation and migration capabilities after light excitation. This material can be used as the absorption layer of the photoanode to help improve the photoelectric conversion efficiency;

[0029] 2) Due to the LSPR effect of Au nanoparticles, a locally enhanced electromagnetic field is generated, which promotes the separation of LaFeO3 carriers, thereby enhancing the photocurrent density and thus improving the photoelectric conversion efficiency;

[0030] 3) Au nanoparticles can be approximated as converging antennas, transferring the energy of incident light to the surrounding LaFeO3 absorption layer, thereby increasing the number of electron-hole pairs and thus enhancing the photocurrent density;

[0031] 4) The LSPR effect of Au nanoparticles is in the wavelength range of 500-700nm, and the light absorption of LaFeO3 is almost non-existent in this range, which directly expands the overall light absorption range of the photoanode and also enhances its photoelectric conversion efficiency in the wavelength range of 500-700nm.

[0032] Second, regarding the technical solution as a whole, the technical effects and advantages of the technical solution to be protected by the present invention are described in detail as follows:

[0033] 1) The preparation of Au-modified LaFeO3-based photoanodes includes four preparation methods: liquid phase deposition, vacuum evaporation, spin coating, and annealing. Each method is simple and convenient and can achieve large-scale production of photoanodes;

[0034] 2) The raw materials of Au-modified LaFeO3-based photoanode are all low-priced and easily available except Au. Although Au is expensive, the use of nano-scale and large-scale production can greatly reduce the cost of Au. That is, once mass production is carried out, the cost of the photoanode can be further reduced;

[0035] 3) The raw materials of Au-modified LaFeO3-based photoanode are environmentally friendly. Elements such as Au and Ti are non-toxic to the environment. Elements La and Fe are generally relatively stable and are not easy to release toxic ions, so they have little harm to the environment and human health.

[0036] 4) Au-modified LaFeO3-based photoanode is corrosion-resistant, has strong chemical stability, and can be used for a long time.

[0037] Third, as auxiliary evidence of the inventiveness of the claims of the present invention, it is also reflected in the following important aspects:

[0038] 1) The technical solution of the present invention fills the technical gap in the industry at home and abroad: due to the limitation of the number of photogenerated electron-hole pairs and the bandgap width of LaFeO3 material, its light absorption range and photoelectric conversion efficiency are limited. The addition of wide bandgap semiconductor TiO2 film expands the light absorption range of the photoanode, and the modification of Au particles further expands the light absorption range of the photoanode and improves the photocurrent density and photoelectric conversion efficiency of the photoanode by relying on the LSPR effect.

[0039] 2) The technical solution of the present invention overcomes technical prejudice: Traditional photoanodes generally choose n-type semiconductor materials, but LaFeO3 is a p-type semiconductor, and it still achieves application in the field of photoanodes, which has a certain reference significance for the application of other p-type semiconductors in photoanodes or n-type semiconductors in photocathodes. In addition, it is generally believed that precious metals such as Au are not suitable for production and preparation due to their high prices, but the actual small amount and large-scale production can control the cost lower. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0041] Figure 1 This is a flow chart of the method for preparing the Au-modified LaFeO3-based photoanode provided in the second embodiment of the present invention with the best performance.

[0042] Figure 2 This is a schematic diagram of the structure of the Au-modified LaFeO3-based photoanode provided in the second embodiment of the present invention with the best performance.

[0043] Figure 3 These are scanning electron microscope (SEM) photos provided by Comparative Example 1, Comparative Example 2, and Comparative Example 4 of the present invention, as well as an energy spectrum analysis diagram of Comparative Example 4.

[0044] Figure 4 It is a graph of ultraviolet absorption spectrum data provided by Example 1, Example 2 and Comparative Example 1 and Comparative Example 3 of the present invention.

[0045] Figure 5 The on-off data diagrams provided from left to right are respectively Example 2, Example 1, and Comparative Example 1 of the present invention.

[0046] Figure 6 From top to bottom are the photoelectric conversion efficiency (IPCE) data diagrams provided by Example 2, Example 1, and Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Based on the embodiments in the present invention, other embodiments obtained by ordinary technicians in this field without making creative work are all within the scope of protection of the present invention. The experimental methods described in the following embodiments are conventional methods unless otherwise specified; the reagents and materials, unless otherwise specified, can be obtained from public commercial channels.

[0048] Spatially relative terms such as "below," "beneath," "below," "above," "upper," etc. are used in this specification to explain the positioning of one element relative to a second element. These terms are intended to encompass different orientations of the device in addition to different orientations than those depicted in the figures.

[0049] In addition, the use of terms such as "first", "second", etc. to describe various elements, layers, regions, sections, etc. is not intended to be limiting. The use of "having", "containing", "including", "comprising", etc. is open-ended, indicating the presence of the stated elements or features, but does not exclude additional elements or features. Unless the context clearly states otherwise.

[0050] The present invention provides an Au-modified LaFeO3-based semiconductor thin film photoelectrochemical water splitting photoanode and a preparation method thereof. The present invention provides two preferred embodiments, two comparative examples, and one test example, which are specifically as follows.

[0051] Example 1: The working electrode of this example is a Au-modified LaFeO3-based photoanode. Figure 1 The steps shown are as follows: Figure 2 The photoanode includes a transparent conductive substrate, a TiO2 layer on the transparent conductive substrate, an Au nanoparticle layer on the TiO2 layer, and a LaFeO3 absorption layer on the Au nanoparticle layer. The transparent conductive substrate is a FTO glass substrate. The TiO2 layer is disposed on the transparent conductive substrate, with a thickness of 400 to 600 nm. The Au nanoparticle layer is disposed on the TiO2 layer, with a thickness of 6 nm, and the particle size of the Au nanoparticles is 15 to 50 nm. The LaFeO3 absorption layer is disposed on the Au nanoparticle layer, with a thickness of 400 to 600 nm.

[0052] In the first embodiment, the photoanode is used as a working electrode of a three-electrode system, and the electrode system includes a working electrode, a reference electrode and a counter electrode. The reference electrode is an Ag / AgCl reference electrode, and the counter electrode is a Pt counter electrode.

[0053] In the first embodiment, the electrode system also includes an electrochemical workstation, which provides an external bias for the electrode system, and the working electrode, the reference electrode and the counter electrode are respectively connected to the electrochemical workstation. After being exposed to sunlight, the LaFeO3-based photoanode excites electron-hole pairs, and the holes enter the electrolyte under the combined action of the spatial electric field and the external bias to carry out the oxygen evolution half-reaction, and the electrons are transferred to the surface of the Pt sheet counter electrode on the other side to participate in the hydrogen evolution half-reaction. In this process, the TiO2 layer plays a role in promoting the separation of carriers by constructing a spatial electric field with the absorption layer, and the localized surface plasmon effect generated by the Au nanoparticle layer further promotes the process: under illumination, the localized surface plasmon can enhance the localized electromagnetic field intensity around the metal nanoparticles, thereby effectively improving the light absorption capacity, realizing the convergence of light by the localized surface plasmon, and promoting the separation of carriers; absorbing more incident light in the electrode system can generate more electron-hole pairs, so that more photocurrent can be generated after the electron-hole pairs are separated.

[0054] In combination with the Au-modified LaFeO3-based photoanode, the first embodiment of the present invention further provides a method for preparing the photoanode. The preparation method is described in detail below.

[0055] The TiO2 layer was grown on the FTO glass substrate using liquid deposition technology and annealing technology. 0.2M ammonium fluorotitanate solution and 0.4M boric acid solution were mixed in a volume ratio of 1:1, and the FTO glass was placed in the mixture for 6 hours. The mixture was then annealed at 500°C for 5 hours using a muffle furnace to obtain a TiO2 thin film layer with a thickness of 400 to 600 nm. A photoelectrode with a TiO2 structure was obtained.

[0056] The Au nanoparticle layer is deposited on the surface of the TiO2 thin film layer by vacuum evaporation technology, and the Au metal film layer is 6nm thick. The Au nanoparticle layer is annealed at 500°C for 30min using a muffle furnace to obtain an Au nanoparticle layer with a particle size of 15 to 50nm. The Au / TiO2 structure photoelectrode is obtained.

[0057] The LaFeO3 absorption layer was prepared by sol-gel spin coating. 4 mmol of lanthanum nitrate hexahydrate, 4 mmol of ferric nitrate nonahydrate and 8 mmol of citric acid monohydrate were dissolved in 10 ml of ethylene glycol monomethyl ether, stirred at 60 ° C for 2 hours, then aged for 24 hours, and filtered through PTFE to obtain the precursor solution. The Au / TiO2 photoelectrode was fixed on the chuck of the gelling machine, and the precursor solution was dripped on its surface. The wet film was spun at 500 r / min for 5 seconds and 4000 r / min for 30 seconds to obtain a wet film. The wet film was baked at 200 ° C for 3 minutes and annealed at 600 ° C for 5 minutes to obtain a layer of LaFeO3 film. In order to make the film reach a certain thickness, the spin coating process was repeated twice, and then it was annealed at 600 ° C for 2 hours using a muffle furnace to obtain the LaFeO3 absorption layer. The photoanode of the LaFeO3 / Au / TiO2 structure was obtained.

[0058] Example 2: This example uses the method of Example 1 to make a photoelectrode and construct an electrode system, except that the Au nanoparticle layer is inside the TiO2 layer. The TiO2 layer that was originally deposited for 6 hours is divided into two times, first depositing for 5 hours and then evaporating the Au nanoparticle layer, followed by depositing the TiO2 layer for 1 hour. A photoanode with a LaFeO3 / TiO2 / Au / TiO2 structure is obtained.

[0059] Comparative Example 1: In this comparative example, a photoelectrode is prepared and an electrode system is constructed according to the method of Example 1, except that the photoelectrode does not have an Au nanoparticle layer. A LaFeO3 / TiO2 photoanode is obtained.

[0060] Comparative Example 2: In this comparative example, a photoelectrode is prepared and an electrode system is constructed according to the method of Example 1, except that the photoelectrode does not have a LaFeO3 absorption layer, and a Au / TiO2 photoanode is obtained.

[0061] Comparative Example 3: In this comparative example, a photoelectrode is made and an electrode system is constructed according to the method of Example 1, except that the photoelectrode has only a TiO2 layer. The obtained structure is a TiO2 photoanode.

[0062] Comparative Example 4: In this comparative example, a photoelectrode is manufactured and an electrode system is constructed according to the method of Example 1, except that the photoelectrode has only a LaFeO3 absorption layer. The obtained structure is a LaFeO3 photoanode.

[0063] Test example:

[0064] On-off data test conditions: The electrolyte solution used is 0.1mol / L KOH solution, and the pH value of the solution is 13. Before starting the test, oxygen is introduced into the electrolyte solution for 30 minutes. The wavelength of the light source can be divided into three intervals of 380-800nm, 440-800nm, and 540-800nm ​​by the filter and the monochromator. During the photoelectrochemical test, the potential is set to (-0.5)-(+0.5)V (relative to the Ag / AgCl reference electrode), increasing in steps of 0.1V; at each potential, the photoanode is tested for its response to light in the three wavelength intervals of 380-800nm, 440-800nm, and 540-800nm. The acquisition time of the photocurrent signal is 5s, and each wavelength interval is tested four times.

[0065] Photoelectric conversion efficiency (IPCE) test conditions: The electrolyte solution used is 0.1mol / L KOH solution, and the pH value of the solution is 13. Before starting the test, oxygen is introduced into the electrolyte solution for 30 minutes. The light source is set to monochromatic light through a filter and a monochromator, and increases in steps of 10nm in the visible light range. The light intensity at each wavelength is tested in advance by a light intensity tester. During the photoelectrochemical test, the potential is set to -0.4V (relative to the Ag / AgCl reference electrode); the acquisition time of the photocurrent signal is 5s, and the test is performed four times at each wavelength. After the test is completed, the IPCE value at each wavelength is calculated by the formula.

[0066] Figure 3 It is a scanning electron microscope (SEM) photo provided by comparative example 1, comparative example 2, and comparative example 4 of the present invention, and an energy spectrum analysis diagram of comparative example 4, wherein LaFeO3 is referred to by the abbreviation "LFO". In the figure, a and b are a cross-sectional view of comparative example 4 (LFO film) and its energy spectrum analysis diagram. In the figure, c is the surface condition of comparative example 1 (LFO / TiO2), and the surface of LFO prepared on TiO2 is smooth. In the figure, d is the surface condition of comparative example 2 (Au / TiO2), and it can be seen that Au nanoparticles have been evenly loaded on TiO2, and the particle size is relatively uniform, with a particle size of 15 to 50 nm, which is conducive to the LSPR effect and improves the photoelectric performance of the photoanode. Example 1 and Example 2, which are further prepared on the basis of comparative example 2, do have better photoelectrocatalytic performance in subsequent tests.

[0067] Figure 4It is a graph of ultraviolet absorption spectrum data provided by Example 1, Example 2 and Comparative Example 1 and Comparative Example 3 of the present invention, wherein LaFeO3 is referred to by the abbreviation "LFO". Comparative Example 1 (LFO / TiO2) adds an LFO absorption layer on the basis of Comparative Example 3 (TiO2), which produces stronger light absorption in the area near 400nm. Based on Comparative Example 1, Example 1 (LFO / Au / TiO2) and Example 2 (LFO / TiO2 / Au / TiO2) add Au nanoparticles with LSPR effect in two ways, both of which result in LSPR absorption peaks near 600nm. Among them, the method of Example 2 produces a higher LSPR absorption peak. This is because the Au nanoparticles in the TiO2 interlayer are not in direct contact with the LFO, and the leakage current will be smaller, resulting in stronger light absorption near 600nm.

[0068] Figure 5 The on-off data graphs provided from left to right for Example 2, Example 1, and Comparative Example 1 of the present invention, respectively, are tested in a solution with a pH value of 13. The three photoanodes are tested for their response to light at each potential of (-0.5)-(+0.5)V (relative to the Ag / AgCl reference electrode) in the three wavelength ranges of 380-800nm, 440-800nm, and 540-800nm. Among them, the photocurrent density generated by Example 1 and Example 2 is significantly higher than that of Comparative Example 1, because the modification of Au nanoparticles with LSPR effect enables the photoanode to improve the light absorption efficiency, thereby producing a significantly enhanced light response.

[0069] Figure 6 The photoelectric conversion efficiency (IPCE) data graphs provided by Example 2, Example 1, and Comparative Example 1 of the present invention are shown from top to bottom. The test was conducted at a potential of -0.4V (relative to the Ag / AgCl reference electrode) in a solution with a pH value of 13. Among them, the IPCE curves of Example 1 and Example 2 produce LSPR absorption peaks near 600nm compared with Comparative Example 1. This is because the modification of Au nanoparticles enables the photoanode to increase the light absorption range. The peak value of the IPCE curve of Example 2 at 600nm is even about 5 times that of Example 1, which shows that the Au nanoparticles in the TiO2 interlayer that are not in direct contact with the LFO have a better LSPR effect on the enhancement effect of the photoanode.

[0070] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited thereto. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention shall be equivalent replacement modes and shall be covered within the protection scope of the present invention.

Claims

1. An Au-modified LaFeO3-based semiconductor thin film photoelectrochemical water splitting photoanode, characterized in that: The Au-modified LaFeO3-based photoanode comprises a transparent conductive substrate, a wide bandgap semiconductor layer on the conductive substrate, an Au nanoparticle layer on the wide bandgap semiconductor layer, and a LaFeO3 absorption layer on the Au nanoparticle layer. The structure of the photoanode is LaFeO3 / Au / TiO2 / FTO. The structure of the improved Au-modified LaFeO3-based photoanode with better performance is LaFeO3 / TiO2 / Au / TiO2 / FTO.

2. The Au-modified LaFeO3-based semiconductor thin film photoelectrochemical water splitting photoanode according to claim 1, characterized in that: The transparent conductive substrate is a FTO glass sheet.

3. The Au-modified LaFeO3-based semiconductor thin film photoelectrochemical water splitting photoanode according to claim 1, characterized in that: The wide bandgap semiconductor layer is a TiO2 layer.

4. The Au-modified LaFeO3-based semiconductor thin film photoelectrochemical water splitting photoanode according to claim 3, characterized in that: The thickness of the wide bandgap semiconductor layer is 400-600 nm.

5. The Au-modified LaFeO3-based semiconductor thin film photoelectrochemical water splitting photoanode according to claim 1, characterized in that: The thickness of the Au nanoparticle layer is 6 nm.

6. The Au-modified LaFeO3-based semiconductor thin film photoelectrochemical water splitting photoanode according to claim 5, characterized in that: The Au nanoparticles have a particle size of 15 to 50 nm.

7. The Au-modified LaFeO3-based semiconductor thin film photoelectrochemical water splitting photoanode according to claim 1, characterized in that: The LaFeO3 absorption layer is a double layer.

8. The Au-modified LaFeO3-based semiconductor thin film photoelectrochemical water splitting photoanode according to claim 7, characterized in that: The overall thickness of the LaFeO3 absorption layer is 400-600 nm.

9. The Au-modified LaFeO3-based semiconductor thin film photoelectrochemical water splitting photoanode according to any one of claims 1 to 8, characterized in that: The photoanode is a working electrode in a three-electrode system, and the electrode system also includes an Ag / AgCl reference electrode, a Pt counter electrode, and an electrochemical workstation. The electrochemical workstation provides a voltage source, and the working electrode, reference electrode, and counter electrode are connected to the electrochemical workstation.

10. A method for preparing an Au-modified LaFeO3-based semiconductor thin film photoelectrochemical water splitting photoanode according to any one of claims 1 to 9, characterized in that: The following steps are involved: Step 1, using liquid deposition technology and annealing technology to grow TiO2 thin film on FTO; Step 2, using vacuum evaporation technology and annealing technology to prepare the Au nanoparticle layer; Step three, preparing the LaFeO3 thin film layer by using sol-gel spin coating and annealing technology.

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