GaN-based photocatalytic device based on microporous structure and preparation method of GaN-based photocatalytic device

Abstract

The invention discloses a GaN-based photocatalytic device based on a microporous structure. The GaN-based photocatalytic device structurally comprises a substrate layer, a GaN-based layer, a GaN-based layer and a GaN-based layer from bottom to top, an n-GaN layer; a multiple quantum well layer; a p-GaN layer; a micropore which penetrates through the p-GaN layer and the multi-quantum well layer and exposes the n-GaN layer is etched in the device. The invention also discloses a preparation method and application thereof. According to the device disclosed by the invention, through introduction of the micropore array structure, the diffusion path of a liquid-phase reactant to an active interface is remarkably shortened, and rapid desorption of gas in the reaction process is promoted, so that the interface mass transfer efficiency of the device is effectively improved; the Pt catalyst loaded in the holes further enhances interface reaction kinetics, and the hydrogen production performance of photocatalytic water decomposition is improved. Experimental results show that under the same reaction system and illumination condition, compared with a traditional GaN-based photocatalytic device with a plane structure, the device has better hydrogen production performance.

Description

Technical Field

[0001] This invention relates to a GaN-based photocatalytic device with a microporous structure and its preparation method, belonging to the field of semiconductor photocatalysis and photoelectrochemical technology. Background Technology

[0002] Photocatalytic water splitting for hydrogen production is an important technological pathway that uses solar energy as the sole energy input and enables clean energy conversion. Compared with traditional water electrolysis or fossil fuel-based hydrogen production methods, this technology has advantages such as mild reaction conditions, simple system structure, and environmental friendliness, and has therefore attracted widespread attention.

[0003] Among numerous photocatalytic material systems, GaN and its related InGaN / GaN heterostructures are considered ideal for constructing solid-state photocatalytic devices due to their excellent chemical stability, corrosion resistance, and tunable bandgap characteristics. By constructing p-GaN / multiple quantum well / n-GaN structures, a built-in electric field can be formed inside the device, effectively promoting the separation and transport of photogenerated carriers, thereby improving the efficiency of photocatalytic reactions.

[0004] However, most existing GaN-based photocatalytic devices employ planar structures, where the reaction interface relies primarily on the macroscopic diffusion of liquid reactants, resulting in limited mass transfer efficiency. Furthermore, gases generated during the photocatalytic reaction tend to accumulate on the planar surface, forming bubbles that further hinder the exposure of active sites and the reaction itself. Even with the introduction of co-catalysts, simple material or interface modifications are insufficient to fundamentally solve the mass transfer limitations caused by the planar structure.

[0005] Therefore, there is an urgent need for a GaN-based photocatalytic device that can effectively improve the mass transfer conditions at the reaction interface and further enhance the photocatalytic reaction efficiency through structural design without significantly increasing device complexity. Summary of the Invention

[0006] This invention discloses a GaN-based photocatalytic device based on a microporous structure. By constructing micropores on the device surface, the diffusion efficiency of reactants and the desorption capacity of bubbles are significantly improved, thereby achieving efficient photocatalytic water splitting to produce hydrogen.

[0007] The technical solution adopted in this invention is as follows: A GaN-based photocatalytic device based on a microporous array structure, the structure of which, from bottom to top, comprises: Substrate layer; n-GaN layer; Multiple quantum well layers; p-GaN layer; The device is etched with micropores penetrating the p-GaN layer and the multiple quantum well layer, and exposing the n-GaN layer.。 Preferably, the micropores are a micropore array with a pore diameter of 5-20 μm, a pore spacing of 5-100 μm, and a pore depth of 600-1200 nm. Preferably, the inner wall and bottom of the micropore are loaded with metal Pt, and the loading thickness is 1-10 nm.

[0008] Preferably, the substrate is a sapphire substrate.

[0009] Preferably, the n-GaN layer has a thickness of 1-2 μm and a doping concentration of 1×10⁻⁶. 18 -5×10 18 cm -3 .

[0010] Preferably, the multiple quantum well layer is an InGaN / GaN multiple quantum well layer with 8-20 periods, and the InGaN well layer thickness is 3 nm and the GaN barrier layer thickness is 15 nm in each period.

[0011] Preferably, the p-GaN layer has a thickness of 100-300 nm and a doping concentration of 1×10⁻⁶. 19 cm -3 -1×10 20 cm -3 .

[0012] This invention also discloses a method for fabricating the above-mentioned GaN-based photocatalytic device, the steps of which include: (1) An n-GaN layer, a multi-quantum well layer, and a p-GaN layer are sequentially deposited on the substrate to form a pn junction; (2) Etch the device surface to form a micropore that penetrates the p-GaN layer and the multiple quantum well layer, and expose the n-GaN layer to obtain a GaN-based photocatalytic device.

[0013] Preferably, the method further includes step (3): directionally depositing a metal catalyst in the n-GaN region on the inner wall and bottom of the micropores.

[0014] The device of this invention significantly shortens the diffusion path of liquid reactants to the active interface and promotes rapid gas desorption during the reaction by introducing a microporous array structure, thereby effectively improving the interfacial mass transfer efficiency of the device. The Pt catalyst supported in the pores further enhances the interfacial reaction kinetics and improves the photocatalytic water splitting for hydrogen production performance. Experimental results show that, under the same reaction system and illumination conditions, this device has superior hydrogen production performance compared to traditional planar GaN-based photocatalytic devices.

[0015] The present invention has the following beneficial effects: (1) Significantly improve mass transfer efficiency: By introducing a microporous array structure on the surface of GaN-based photocatalytic devices, the diffusion path of liquid reactants to the active interface of semiconductors is shortened, and a fast desorption channel is provided for the gas generated during the reaction, which effectively reduces the problem of bubbles covering the reaction interface, thereby significantly improving the overall mass transfer efficiency of the device in liquid-phase photocatalytic reactions.

[0016] (2) Structure-driven performance enhancement mechanism: This invention enhances photocatalytic performance by controlling the surface geometry of the device, rather than simply relying on changes in the material system or the type of cocatalyst. This structure control strategy has good versatility and scalability, and is easy to promote and apply under different semiconductor systems and reaction conditions. By exposing the n-GaN active region, photogenerated electrons can obtain a faster transport channel to the solid-liquid interface; combined with the high catalytic activity of the Pt cocatalyst, it effectively promotes the hydrogen evolution reaction (HER).

[0017] Differences and advancements compared to existing technologies: Compared to traditional planar GaN-based photocatalytic devices, this invention achieves synergistic optimization of mass transfer conditions and interfacial reaction kinetics at the reaction interface by introducing a microporous array structure and loading a metal catalyst layer within the micropores. Under the same reaction system and illumination conditions, the hydrogen production performance of the device exhibits a trend of planar structure < microporous array structure < microporous array with metal catalyst loaded within the pores. This indicates that the microporous array effectively improves reactant diffusion and gas desorption, while the metal catalyst within the pores further enhances the interfacial reaction process. Therefore, this invention represents a significant advancement over existing technologies in terms of structural design and performance improvement mechanisms. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the GaN-based photocatalytic device based on a microporous structure according to the present invention; Figure 2 This is a scanning electron microscope (SEM) image of Pt modified with a microporous array; Figure 3 This is a schematic diagram of the reaction device and hydrogen production results under the conditions of 0.4 M ascorbic acid solution and 300 W simulated light source irradiation with an Air Mass 1.5 Global filter; Figure 4 This is a comparison chart of hydrogen production rates for each device. Detailed Implementation

[0019] The present invention will be further described below with reference to the embodiments, but the description of the embodiments does not limit the scope of protection of the present invention in any way.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Furthermore, while this document provides examples of parameters containing specific values, it should be understood that the parameters need not be exactly equal to the corresponding values, but can approximate the corresponding values ​​within acceptable error tolerances or design constraints. Directional terms mentioned in the embodiments, such as “up,” “down,” “front,” “back,” “left,” “right,” etc., are only for reference to the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the scope of protection of this invention.

[0021] Unless otherwise specified, all substances or instruments used in the following examples can be obtained from conventional commercial sources.

[0022] Example 1: Fabrication of GaN-based photocatalytic devices with microporous arrays A 2 μm doping concentration of 2×10⁻⁶ was sequentially epitaxially grown on a sapphire substrate. 19 cm -3 n-GaN, 200 nm InGaN / GaN multiple quantum wells (MQWs) and 100 nm doping concentration 1×10 20 cm -3 The p-GaN is used to form a pn junction. Subsequently, a regular array of micropores is fabricated on the device surface using photolithography and dry etching processes, so that the micropores penetrate into the n-GaN layer. The micropores have a diameter of 10 µm, a spacing of 40 µm, and a depth of 1 µm. The resist is removed, the device is cleaned, and dried for later use.

[0023] Example 2: Deposition of metal catalysts The microporous array GaN-based device prepared in Example 1 was placed in an electron beam evaporation system and subjected to high vacuum of 5 × 10⁻⁶. - 6 Pt metal catalyst deposition was performed under Torr conditions. The deposition rate was 0.1–0.2 Å·s. -1 Pt catalyst was selectively deposited on the inner walls and bottom of the micropores in the exposed n-GaN regions, forming a Pt catalyst layer supported within the pores. The deposition thickness of the Pt catalyst layer was 10 nm. After deposition, the device was removed, cleaned, and dried to obtain a GaN-based photocatalytic device with a Pt metal catalyst supported within the micropores. The resulting device structure is shown below. Figure 1 As shown, the scanning electron microscope (SEM) image is as follows. Figure 2 As shown.

[0024] Example 3: Photocatalytic water splitting for hydrogen production test like Figure 3As shown, the device was placed in a reaction system containing 0.4 M ascorbic acid (AA) solution, and a photocatalytic reaction was carried out under AM 1.5G simulated sunlight irradiation conditions. The hydrogen production rate was determined by gas volume method to be 4.25 mL / h (60 min). Devices with identical parameters but without etched micropore arrays, and devices with only etched micropore arrays but without Pt metal catalyst deposition, were simultaneously subjected to photocatalytic reactions under the same conditions. The results are as follows. Figure 4 As shown.

[0025] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A GaN-based photocatalytic device based on a microporous structure, the structure of which comprises, from bottom to top: Substrate layer; n-GaN layer; Multiple quantum well layers; p-GaN layer; The device is characterized by having micropores etched through a p-GaN layer and a multi-quantum well layer, and exposing an n-GaN layer.

2. The GaN-based photocatalytic device according to claim 1, characterized in that: The micropores are micropore arrays with a pore diameter of 5-20 μm, a pore spacing of 5-100 μm, and a pore depth of 600-1200 nm.

3. The GaN-based photocatalytic device according to claim 1, characterized in that: The inner wall and bottom of the micropores are loaded with metal Pt, with a loading thickness of 1-10 nm.

4. The GaN-based photocatalytic device according to claim 1, characterized in that: The substrate is a sapphire substrate.

5. The GaN-based photocatalytic device according to claim 1, characterized in that: The n-GaN layer has a thickness of 1-2 μm and a doping concentration of 1×10⁻⁶. 18 -5×10 18 cm -3 .

6. The GaN-based photocatalytic device according to claim 1, characterized in that: The multiple quantum well layer is an InGaN / GaN multiple quantum well layer with 8-20 periods. The InGaN well layer thickness is 3 nm and the GaN barrier layer thickness is 15 nm in each period.

7. The GaN-based photocatalytic device according to claim 1, characterized in that: The p-GaN layer has a thickness of 100-300 nm and a doping concentration of 1×10⁻⁶. 19 cm -3 -1×10 20 cm -3 .

8. The method for fabricating the GaN-based photocatalytic device according to any one of claims 1-7, characterized in that... The steps include: (1) An n-GaN layer, a multi-quantum well layer, and a p-GaN layer are sequentially deposited on the substrate to form a pn junction; (2) Etch the device surface to form a micropore that penetrates the p-GaN layer and the multiple quantum well layer, and expose the n-GaN layer to obtain a GaN-based photocatalytic device.

9. The preparation method according to claim 8, characterized in that, It also includes step (3): directional deposition of metal Pt in the n-GaN region on the inner wall and bottom of the micropore to obtain a GaN-based photocatalytic device.

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