Silicon-based photoelectrode and preparation method and application thereof

Abstract

The invention belongs to the technical field of photoelectrochemistry, and provides a silicon-based photoelectrode and a preparation method and application thereof.The preparation method comprises the steps that a compact SiOx layer is directly prepared on a silicon substrate with a natural oxide layer removed through an ultraviolet ozone oxidation technology and serves as an insulating layer, and the silicon-based photoelectrode is prepared; and then a collector and a catalytic effect are achieved by integrating a double-layer metal structure, and the economical and efficient MIS structure photoelectrode is obtained. The ultraviolet ozone oxidation process is simple and convenient, easy to operate and low in cost, and the prepared silicon oxide has fewer hole defects and is more compact, so that the PEC hydrogen evolution reaction (HER) can be effectively improved when the obtained silicon-based photoelectrode is used as a photocathode.

Description

Technical Field

[0001] The invention belongs to the technical field of photoelectrochemistry and relates to a silicon-based photoelectrode and a preparation method and application thereof. Background Art

[0002] Photoelectrochemical water splitting (PEC) has attracted widespread attention as a method to effectively utilize solar energy to convert it into a clean and renewable hydrogen energy supply. It is considered to be one of the potential hydrogen production technologies to address the energy crisis and environmental pollution crisis. In the photoelectrochemical water splitting system, semiconductor photoelectrode materials, as the core part of the electrolytic cell light absorption and energy conversion, are the key to promoting the application of PEC. At present, it has been proven to be an effective modification method to promote the photoelectrochemical water splitting hydrogen evolution by constructing a metal-insulator-semiconductor structure (MIS) on the surface of the photoelectrode to increase the starting potential of the reaction.

[0003] Among them, the insulating layer usually acts as a protective barrier to physically separate the semiconductor material from the electrolyte solution, thereby improving the stability of the semiconductor material. At the same time, it can also act as a tunneling layer to play a regulatory role. In short, it is one of the important structures that affect the photoelectrochemical performance of the MIS structure. In the existing MIS structure design, the insulating layer is often made of SiO 2 , HfO 2 or TiO 2 Compared with other materials, SiO 2 Since it can be directly obtained by oxidation of the silicon substrate, it becomes a more practical choice. 2 The existing methods face the problems of high investment cost, long preparation time and thickness control. However, SiO 2 Although the thin layer method is more economical and simple, it is more difficult to accurately control its thickness and cannot meet the requirements of fine regulation of MIS structural performance through the insulating layer.

[0004] In summary, the existence of many interface problems such as the preparation and thickness control of the insulating layer in the metal-insulator-semiconductor structure and the cost-effectiveness of the electrode limit the application and industrial prospects of the metal-insulator-semiconductor structure in photoelectrochemical water splitting to produce hydrogen. Therefore, a simple, economical and thickness-adjustable insulating layer preparation method is crucial for designing efficient photoelectrodes to improve the overall efficiency of solar water splitting to produce hydrogen. Summary of the invention

[0005] In view of the problems existing in the prior art, the object of the present invention is to provide a silicon-based photoelectrode and a preparation method and use thereof. The preparation method directly prepares a dense SiO2 on a silicon substrate after removing the natural oxide layer by an ultraviolet ozone oxidation process. xThe layer is used as an insulating layer, and the double-layer metal structure is integrated as a collector and a catalyst to obtain an economical and efficient MIS structure photoelectrode. The UV ozone oxidation process is not only simple and convenient, easy to operate, and low in cost, but also has fewer hole defects and is more dense, so that the obtained silicon-based photoelectrode can effectively improve the PEC hydrogen evolution reaction (HER) as a photocathode.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a silicon-based photoelectrode, the preparation method comprising:

[0008] (1) providing a silicon substrate, and removing a natural oxide layer on a surface of the silicon substrate;

[0009] (2) performing ultraviolet ozone oxidation treatment on the side of the silicon substrate where the natural oxide layer is removed, so that the surface of the silicon substrate on this side is oxidized to form a dense SiO x layer, the dense SiO x The layer is an insulating layer;

[0010] (3) Preparing a first metal layer on a surface of the insulating layer away from the silicon substrate, and preparing a second metal layer on a surface of the first metal layer away from the insulating layer, wherein the first metal layer and the second metal layer form a double-layer metal structure to obtain a silicon-based photoelectrode.

[0011] The preparation method of the present invention is carried out by ultraviolet ozone (UV / O 3 ) oxidation process directly on the silicon substrate to prepare ultra-thin silicon oxide layer (dense SiO x The double-layer metal structure is integrated as an insulating layer to act as a collector and catalyst, thus obtaining an economical and efficient MIS structure photoelectrode. The UV-ozone oxidation process is not only simple and convenient, easy to operate, and low in cost, but also has fewer pore defects and is more dense, making the obtained silicon-based photoelectrode as a photocathode effectively improve the PEC hydrogen evolution reaction (HER).

[0012] The following are preferred technical solutions of the present invention, but are not intended to be limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0013] As a preferred technical solution of the present invention, the silicon substrate includes p-Si.

[0014] In the present invention, the preferred silicon substrate is p-Si, which has complete crystallinity and high carrier mobility, as well as good light absorption ability and a suitable band gap (1.1 eV).

[0015] Preferably, the silicon substrate is cleaned and dried before removing the natural oxide layer; the cleaning and drying process includes ultrasonically cleaning the silicon substrate in acetone, isopropanol and ethanol for 5 to 20 minutes, such as 5 minutes, 8 minutes, 10 minutes, 13 minutes, 15 minutes, 18 minutes or 20 minutes, and finally drying with nitrogen, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0016] Preferably, in order to avoid and reduce the influence of natural oxidation on the silicon substrate again after the natural oxide layer is removed, the ultraviolet ozone oxidation treatment should be performed as soon as possible.

[0017] As a preferred technical solution of the present invention, the method for removing the natural oxide layer on the surface of the silicon substrate comprises immersing the silicon substrate in an HF solution.

[0018] Preferably, the mass concentration of the HF solution is 1% to 5%, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0019] Preferably, the soaking time is 1 to 5 minutes, for example, 1 minute, 1.5 minutes, 2 minutes, 2.5 minutes, 3 minutes, 3.5 minutes, 4 minutes, 4.5 minutes or 5 minutes, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0020] In the present invention, the natural oxide layer on the surface of the silicon substrate refers to a silicon oxide layer (SiO 2 layer), which has more defects and greater roughness than the silicon oxide layer prepared by the ultraviolet ozone oxidation process of the present invention.

[0021] As a preferred technical solution of the present invention, the ultraviolet ozone oxidation treatment is carried out in an ultraviolet ozone cleaning machine.

[0022] Preferably, the ultraviolet light for the ultraviolet ozone oxidation treatment is generated by a low-pressure mercury vapor lamp, including ultraviolet light with a wavelength of 185nm, and may also include ultraviolet light with a wavelength of 254nm. The ultraviolet light with a wavelength of 185nm can decompose oxygen molecules in the air, and the generated oxygen atoms react with oxygen to generate ozone. 3 , which has strong oxidizing properties and can oxidize the surface of the silicon substrate to generate the ultra-thin dense SiO x layer.

[0023] Preferably, the time of the ultraviolet ozone oxidation treatment is 1 to 7 minutes, for example, 1 minute, 1.5 minutes, 2 minutes, 2.5 minutes, 3 minutes, 3.5 minutes, 4 minutes, 4.5 minutes, 5 minutes, 5.5 minutes, 6 minutes, 6.5 minutes or 7 minutes, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0024] In the present invention, by adjusting the parameters of the ultraviolet ozone oxidation treatment, especially the treatment time, it is possible to obtain dense SiO x By controlling the layer, the carrier tunneling flux can be affected, thereby reducing the recombination loss, improving the photovoltage and interface charge transfer efficiency, and achieving fine adjustment and optimization of the photoelectrochemical performance of silicon-based photoelectrodes.

[0025] As a preferred technical solution of the present invention, the dense SiO x In the layer, x<2.

[0026] In the present invention, the dense SiO obtained by ultraviolet ozone oxidation treatment x The layer belongs to the low-density suboxide species, that is, x < 2, containing less incompletely oxidized silicon components (suboxides). The atomic arrangement inside the material is more orderly, reducing the positional disorder of silicon atoms, and is different from the SiO formed by natural oxidation. 2 Different layers.

[0027] Preferably, the dense SiO x The average roughness R of the layer q The value is ≤0.4nm, for example, 0.4nm, 0.39nm, 0.38nm, 0.37nm, 0.36nm, 0.35nm, 0.34nm, 0.33nm, 0.32nm, 0.31nm or 0.3nm, etc., preferably ≤0.34nm, but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0028] Preferably, the dense SiO x The thickness of the layer is 0.1 to 1.3 nm, for example, 0.1 nm, 0.2 nm, 0.3 nm, 0.4 nm, 0.43 nm, 0.48 nm, 0.5 nm, 0.52 nm, 0.55 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1 nm, 1.1 nm, 1.2 nm or 1.3 nm, preferably 0.48 to 0.54 nm, more preferably 0.49 to 0.51 nm, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0029] As a preferred technical solution of the present invention, the metal element of the first metal layer includes at least one of Al, Ti, Fe or Co, preferably Al.

[0030] Preferably, the thickness of the first metal layer is 1 to 3 nm, such as 1 nm, 1.2 nm, 1.4 nm, 1.6 nm, 1.8 nm, 2 nm, 2.2 nm, 2.4 nm, 2.6 nm, 2.8 nm or 3 nm, preferably 1.8 to 2.2 nm. However, the thickness is not limited to the above values, and other values ​​not listed in the above range are also applicable.

[0031] In the present invention, the first metal layer is preferably a low work function metal layer, which is closely connected to the dense SiO x When the layers are in contact, the low work function metal element adjusts the band bending degree of the semiconductor-metal interface. At the same time, the first metal layer acts as an adhesion layer, which helps to improve the stability of the second metal layer thereon. Moreover, due to its lower work function, the double-layer metal structure composed of it and the second metal layer can form a higher Schottky contact barrier.

[0032] It should also be noted that due to the first metal layer and the dense SiO x Layers are in direct contact, dense SiO x The oxygen element in the layer will be dense SiO x The interface between the layer and the first metal layer gradually diffuses toward the second metal layer and shows a decreasing concentration trend. x A metal oxide may be formed in the surface layer of the first metal layer near the interface between the layer and the first metal layer.

[0033] As a preferred technical solution of the present invention, the metal element of the second metal layer includes Ni.

[0034] Preferably, the thickness of the second metal layer is 1 to 3 nm, such as 1 nm, 1.2 nm, 1.4 nm, 1.6 nm, 1.8 nm, 2 nm, 2.2 nm, 2.4 nm, 2.6 nm, 2.8 nm or 3 nm, preferably 1.8 to 2.2 nm. However, the thickness is not limited to the above values, and other values ​​not listed in the above range are also applicable.

[0035] In the present invention, the second metal layer is preferably a HER hydrogen evolution metal catalyst layer, and more preferably a non-precious metal catalyst element, such as Ni.

[0036] Preferably, the metal element of the first metal layer is Al, and the metal element of the second metal layer is Ni.

[0037] Compared with other double-layer metal combinations, the double-layer metal structure of Al and Ni has a more superior hydrogen evolution HER reaction activity. This is because the different metal elements in the first metal layer have different affinities for electrons, which leads to differences in charge transfer at the interface between the first metal layer and the second metal layer. The difference in work function between the Al and Ni surfaces is much larger than that of other combinations, indicating that the transfer charge volume of this system is much larger, thus having higher catalytic performance.

[0038] As a preferred technical solution of the present invention, the method of preparing the first metal layer and the method of preparing the second metal layer include evaporation.

[0039] Preferably, the background vacuum degree of the evaporation is less than 5×10 -4 Pa, for example, can be 5×10 -4 Pa, 4×10 -4 Pa, 3×10 -4 Pa, 2×10 -4 Pa or 1×10 -4 Pa, etc., but are not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0040] Preferably, the evaporation rate of the evaporation is For example or etc., but are not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0041] In a second aspect, the present invention provides a silicon-based photoelectrode, wherein the silicon-based photoelectrode is obtained by the preparation method described in the first aspect.

[0042] In a third aspect, the present invention provides a use of the silicon-based photoelectrode described in the second aspect, wherein the use includes photoelectrochemical decomposition of water to produce hydrogen.

[0043] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0044] The preparation method of the present invention directly prepares dense SiO2 on a silicon substrate after removing the natural oxide layer through an ultraviolet ozone oxidation process. x The layer is used as an insulating layer, and the double-layer metal structure is integrated to play the role of collector and catalyst, thus obtaining an economical and efficient MIS structure photoelectrode. The ultraviolet ozone oxidation process is not only simple and convenient, easy to operate, and low in cost, but also the silicon oxide obtained is evenly distributed on the silicon surface, effectively reducing the defect state density. The ultraviolet ozone oxidation process can achieve the dense SiO xThe precise control of the layer thickness effectively reduces the recombination loss and increases the photovoltage by optimizing the thickness, making the resulting silicon-based photoelectrode effectively improve the PEC hydrogen evolution reaction as a photocathode.

[0045] In the present invention, by selecting the metal element of the first metal layer as Al and the metal element of the second metal layer as Ni, the Schottky junction between Al and the silicon substrate can improve the separation efficiency of electron-hole pairs, so that the double-layer metal structure of Al and Ni has a more superior hydrogen evolution HER reaction activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is an optical microscope test image of the silicon-based photoelectrode obtained in Example 1 on the second metal layer side.

[0047] Figure 2 This is an atomic force microscope test image of the interface of the silicon-based photoelectrode obtained in Example 1 on the second metal layer side.

[0048] Figure 3 This is a scanning electron microscope test image of the silicon-based photoelectrode obtained in Example 1 on the second metal layer side.

[0049] Figure 4 This is a HRTEM image of the cross section of the silicon-based photoelectrode obtained in Example 1.

[0050] Figure 5 This is the EDS element distribution map corresponding to the HRTEM image of the cross section of the silicon-based photoelectrode obtained in Example 1.

[0051] Figure 6 The dense SiO obtained in step (2) of Example 1 x AFM test image of the layer.

[0052] Figure 7 This is an AFM test image of the natural oxide layer on the silicon substrate in Comparative Example 1.

[0053] Figure 8 This is a graph showing the electrochemical test results of the silicon-based photoelectrodes obtained in Examples 1 to 4 and Comparative Examples 1 and 2.

[0054] Fig. 9 It is a graph showing the electrochemical test results of the silicon-based photoelectrodes obtained in Example 1 and Examples 5 to 7. DETAILED DESCRIPTION

[0055] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0056] It should be clear to those skilled in the art that the embodiments are only intended to help understand the present invention and should not be considered as specific limitations of the present invention.

[0057] Example 1

[0058] This embodiment provides a method for preparing a silicon-based photoelectrode, the method comprising:

[0059] (1) providing a silicon substrate, wherein the silicon substrate is a p-Si sheet with a size of 1 cm×1 cm; ultrasonically cleaning the silicon substrate in acetone, isopropanol and ethanol for 15 min respectively, and finally drying it with flowing nitrogen for later use; soaking the dried silicon substrate in a HF solution with a mass concentration of 2% for 2 min to remove the natural oxide layer on the surface of the silicon substrate, and then rinsing it with ultrapure water and drying it with flowing nitrogen;

[0060] (2) placing the dried silicon substrate into an ultraviolet ozone cleaning machine, and performing ultraviolet ozone oxidation treatment on the side of the silicon substrate where the natural oxide layer is removed. The ultraviolet light of the ultraviolet ozone oxidation treatment is generated by a low-pressure mercury vapor lamp, and the ultraviolet light wavelength is 185nm and 254nm. The treatment time is 3min to oxidize the surface of the silicon substrate on this side to form a dense SiO x layer (x<2), the dense SiO x The layer is an insulating layer;

[0061] (3) The silicon substrate with the insulating layer was transferred to the sample chamber of the evaporator and vacuumed to 5×10 -4 After Pa, the evaporation rate of the material is adjusted by controlling the current and voltage on the two different evaporation source tungsten boats. First, an aluminum layer with a target thickness of 2nm is obtained by vapor deposition as the first metal layer, and then a nickel layer with a target thickness of 2nm is formed on the first metal layer as the second metal layer. The first metal layer and the second metal layer constitute a double-layer metal structure to obtain a silicon-based photoelectrode.

[0062] Example 2

[0063] This embodiment provides a method for preparing a silicon-based photoelectrode. In the preparation method, the time of ultraviolet ozone oxidation treatment in step (2) is adjusted from 3 minutes to 1 minute. Except for the above, other conditions are exactly the same as those in Example 1.

[0064] Example 3

[0065] This embodiment provides a method for preparing a silicon-based photoelectrode. In the preparation method, the time of ultraviolet ozone oxidation treatment in step (2) is adjusted from 3 minutes to 5 minutes. Except for the above, other conditions are exactly the same as those in Example 1.

[0066] Example 4

[0067] This embodiment provides a method for preparing a silicon-based photoelectrode. In the preparation method, the time of ultraviolet ozone oxidation treatment in step (2) is adjusted from 3 minutes to 7 minutes. Except for the above, other conditions are exactly the same as those in Example 1.

[0068] Example 5

[0069] This embodiment provides a method for preparing a silicon-based photoelectrode. In the preparation method, in step (3), the first metal layer is adjusted from an aluminum layer to a titanium layer. Except for the above, other conditions are exactly the same as those in Example 1.

[0070] Example 6

[0071] This embodiment provides a method for preparing a silicon-based photoelectrode. In the preparation method, in step (3), the first metal layer is adjusted from an aluminum layer to an iron layer. Except for the above, other conditions are exactly the same as those in Example 1.

[0072] Example 7

[0073] This embodiment provides a method for preparing a silicon-based photoelectrode. In the preparation method, in step (3), the first metal layer is adjusted from an aluminum layer to a cobalt layer. Except for the above, other conditions are exactly the same as those in Example 1.

[0074] Comparative Example 1

[0075] This comparative example provides a method for preparing a silicon-based photoelectrode. The preparation method directly uses the cleaned and blow-dried silicon substrate to perform step (3) and retain the natural oxide layer. Except for the above, other conditions are exactly the same as those in Example 1.

[0076] Comparative Example 2

[0077] This comparative example provides a method for preparing a silicon-based photoelectrode, wherein the preparation method only performs steps (1) and (3) and does not perform step (2), that is, the natural oxide layer is removed and the silicon oxide layer is not re-formed. Except for the above, other conditions are exactly the same as those in Example 1.

[0078] Characterization and testing

[0079] Figure 1 , Figure 2 and Figure 3 They are respectively an optical microscope test image of the silicon-based photoelectrode obtained in Example 1 on the second metal layer side, an atomic force microscope test image at the interface, and a scanning electron microscope test image. Figure 1 The optical images show a clear contrast difference between the interface of the silicon substrate covered with the double-layer metal structure and the clean silicon substrate. Figure 2It can be clearly seen that there are no obvious protruding particles and agglomeration on the surface of the double-layer metal structure, and the overall distribution is relatively uniform. The total thickness of the double-layer metal structure can be measured to be 4.13nm. Figure 3 It shows that the surface morphology of the silicon-based photoelectrode is a continuous, flat metal plane.

[0080] Figure 4 and Figure 5 The HRTEM image of the cross section of the silicon-based photoelectrode obtained in Example 1 and the corresponding EDS element distribution map show that there is an amorphous layer with oxygen element distribution and a thickness of about 2.52 nm between the silicon substrate and the nickel layer. Further, according to the distribution of Al element, it is found that the thickness of the aluminum oxide layer is about 2.01 nm. Therefore, it can be inferred that the dense SiO2 formed by ultraviolet ozone oxidation x The thickness of the layer is 0.51nm. This means that the aluminum layer and the dense SiO x The Al atoms on the interface of the layer are from SiO x Capturing oxygen atoms to form aluminum oxide can achieve better optimization effects than simply forming a nickel layer on a silicon oxide layer. Figure 4 and Figure 5 The thickness of the nickel layer can also be measured to be about 2.1 nm, and the actual thickness of the aluminum layer and the nickel layer is very close to the target thickness during evaporation. The present invention also uses a spectroscopic ellipsometer to measure the density of dense SiO x The thickness of the layer was 0.58 nm, which was consistent with the thickness data obtained by EDS analysis. x The thickness of the layer is as follows: 0.204 nm for Example 2, 0.976 nm for Example 3, 1.266 nm for Example 4, 2.258 nm for Comparative Example 1, and 0.13 nm for Comparative Example 2.

[0081] Figure 6 The dense SiO obtained in step (2) of Example 1 x AFM test image of the layer, Figure 7 This is an AFM test image of the natural oxide layer on the silicon substrate in Example 1. By comparison, it can be seen that the dense SiO x The surface of the layer is flat, the pores are obviously smaller, and the average roughness R q The value is 0.388nm, which is significantly smaller than the average roughness R of the natural oxide layer in Comparative Example 1. q The value is 0.556 nm, indicating that the dense SiO prepared by UV-ozone oxidation x A more uniform layer distribution can effectively reduce the interface defect state density, which plays a vital role in the performance of the photoelectrode.

[0082] Furthermore, the silicon-based photoelectrodes obtained in the examples and comparative examples were respectively scraped to remove the oxide layer in the central area of ​​the back of the silicon wafer and cleaned, and a layer of gallium-indium alloy was coated and used to form an ohmic contact between the copper wire and the back of the silicon wafer, and then fixed to a glass plate with an insulating tape, and then the connection between the silicon wafer and the glass plate was sealed with an epoxy resin adhesive to form a photocathode test sample with a reaction window exposed. Then, a photoelectrochemical hydrogen evolution test was performed using a three-electrode system of an electrochemical workstation, with a xenon arc lamp as the light source and calibrated to 100mW·cm -2 The cathode test sample was used as the working electrode, the reference electrode and the counter electrode were Hg / HgO electrode (bottom diameter of about 2 mm) and carbon rod (diameter of about 5 mm), respectively, and 1M KOH (pH = 13.62) was selected as the electrolyte. The current was measured by linear sweep voltammetry with a sweep rate of 20 mV·s -1 By changing the voltage of the working electrode relative to the reference electrode, the current between the carbon rod and the working electrode is measured to obtain the electrochemical polarization curve of the sample.

[0083] Figure 8 The electrochemical test results of the silicon-based photoelectrodes obtained in Examples 1 to 4 and Comparative Examples 1 and 2 show that the dark currents of all photocathodes are close to zero, indicating that the current observed under simulated solar irradiation is attributed to photogenerated carriers. Under illumination conditions, as the time of ultraviolet ozone oxidation treatment increases, the starting potential and saturated light flux density of the obtained silicon-based photoelectrode initially increase and then decrease. It can be seen that based on the tunneling effect, which is the main mechanism of electron transfer within the effective thickness range of the silicon oxide layer, for ultraviolet ozone oxidation treatment, when the treatment time is 3 minutes, the obtained dense SiO with a thickness of 0.58 nm is x The layer can achieve the best optimization effect, and the response current reaches -25mA·cm -2 , the photogenerated carriers can be effectively transferred. For the silicon-based photoelectrode in Example 2 that was treated for only 1 min, an obvious transient photocurrent peak appeared, indicating that there was serious recombination of the interface charges. When the thickness of the insulating layer deviated from this optimal value and gradually increased, the movement of the photogenerated electrons of the silicon-based photoelectrode obtained in Examples 3 and 4 to the electrolyte surface was hindered, and a higher voltage was required to pass through the thicker SiO x Insulation layer.

[0084] Depend on Figure 8 It can also be seen that in the MIS structure, the silicon-based photoelectrode with a native oxidized silicon dioxide layer as the tunnel insulating layer in Comparative Example 1 leads to a low PEC HER activity, which may be due to the limitation of mass transfer through the thickness of the native oxidized silicon dioxide layer and the limitation of the high interface state. The silicon-based photoelectrode obtained in Comparative Example 2 without a silicon dioxide layer has the worst performance, and the silicon oxide insulating layer on the surface is indispensable.

[0085] Fig. 9 are the electrochemical test results of the silicon-based photoelectrodes obtained in Example 1 and Example 5 to Example 7, Fig. 9 It is shown in the figure that compared with the first metal layer in which other metals are matched with the nickel layer, the double-layer metal structure composed of the aluminum layer and the nickel layer has better PEC HER performance.

[0086] In summary, the preparation method of the present invention directly prepares dense SiO2 on a silicon substrate after removing the natural oxide layer through a UV-ozone oxidation process. x The layer is used as an insulating layer, and the double-layer metal structure is integrated to play the role of collector and catalyst, thus obtaining an economical and efficient MIS structure photoelectrode. The ultraviolet ozone oxidation process is not only simple and convenient, easy to operate, and low in cost, but also the silicon oxide obtained is evenly distributed on the silicon surface, effectively reducing the defect state density. The ultraviolet ozone oxidation process can achieve the dense SiO x The precise control of the layer thickness effectively reduces the recombination loss and increases the photovoltage by optimizing the thickness, making the resulting silicon-based photoelectrode effectively improve the PEC hydrogen evolution reaction as a photocathode.

[0087] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0088] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0089] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a silicon-based photoelectrode, characterized in that: The preparation method comprises: (1) providing a silicon substrate, and removing a natural oxide layer on a surface of the silicon substrate; (2) performing ultraviolet ozone oxidation treatment on the side of the silicon substrate where the natural oxide layer is removed, so that the surface of the silicon substrate on this side is oxidized to form a dense SiO x layer, the dense SiO x The layer is an insulating layer; (3) Preparing a first metal layer on a surface of the insulating layer away from the silicon substrate, and preparing a second metal layer on a surface of the first metal layer away from the insulating layer, wherein the first metal layer and the second metal layer form a double-layer metal structure to obtain a silicon-based photoelectrode.

2. The method for preparing a silicon-based photoelectrode according to claim 1, characterized in that: The silicon substrate includes p-Si.

3. The method for preparing a silicon-based photoelectrode according to claim 1 or 2, characterized in that: The method for removing the natural oxide layer on the surface of the silicon substrate comprises soaking the silicon substrate in an HF solution; Preferably, the mass concentration of the HF solution is 1% to 5%; Preferably, the soaking time is 1 to 5 minutes.

4. The method for preparing a silicon-based photoelectrode according to any one of claims 1 to 3, characterized in that: The ultraviolet ozone oxidation treatment is carried out in an ultraviolet ozone cleaning machine; Preferably, the ultraviolet light for the ultraviolet ozone oxidation treatment is generated by a low-pressure mercury vapor lamp, including ultraviolet light with a wavelength of 185 nm; Preferably, the ultraviolet ozone oxidation treatment lasts for 1 to 7 minutes.

5. The method for preparing a silicon-based photoelectrode according to any one of claims 1 to 4, characterized in that: The dense SiO x In the layer, x < 2; Preferably, the dense SiO x The average roughness R value of the layer is ≤0.4nm; Preferably, the dense SiO x The thickness of the layer is 0.1 to 1.3 nm, preferably 0.48 to 0.54 nm.

6. The method for preparing a silicon-based photoelectrode according to any one of claims 1 to 5, characterized in that: The metal element of the first metal layer includes at least one of Al, Ti, Fe or Co, preferably Al; Preferably, the thickness of the first metal layer is 1-3 nm, preferably 1.8-2.2 nm.

7. The method for preparing a silicon-based photoelectrode according to any one of claims 1 to 6, characterized in that: The metal element of the second metal layer includes Ni; Preferably, the thickness of the second metal layer is 1-3 nm, preferably 1.8-2.2 nm.

8. The method for preparing a silicon-based photoelectrode according to any one of claims 1 to 7, characterized in that: The method of preparing the first metal layer and the method of preparing the second metal layer include evaporation; Preferably, the background vacuum degree of the evaporation is less than 5×10 -4 Pa; Preferably, the evaporation rate of the evaporation is 9. A silicon-based photoelectrode, characterized in that: The silicon-based photoelectrode is obtained by the preparation method according to any one of claims 1 to 8.

10. A use of the silicon-based photoelectrode according to claim 9, characterized in that: The use includes photoelectrochemical decomposition of water to produce hydrogen.

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