A preparation method of a bubble self-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction

Abstract

The application provides a preparation method of a bubble self-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction, and relates to the technical field of preparation of an electrocatalytic hydrogen evolution electrode for hydrogen production by electrolysis of water. After performing surface pretreatment on a conductive substrate, the application uses a femtosecond laser to process a gradient hole array and a surface microcolumn array on the substrate, so that the gradient hole array and the microcolumn array are spatially interwoven to form a three-dimensional gas-liquid mass transfer channel and a two-dimensional capillary network with super-wetting characteristics, and a hydrogen evolution reaction catalyst is loaded on the micro-nano structure composite surface to form a catalytically active layer. In the process of electrocatalytic hydrogen evolution, the gradient hole array guides the bubbles generated in situ in the hole to be oriented to separate from the large aperture end, an asymmetric pressure field is formed on both sides of the hole, the microcolumn array provides a capillary pumping effect to continuously supplement the electrolyte, so that a bubble self-driven one-way mass transfer electrode is obtained, the bubble shielding is weakened, and the mass transfer efficiency and the electrocatalytic hydrogen evolution performance are improved.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic hydrogen evolution electrode preparation technology for water electrolysis to produce hydrogen, and in particular to a method for preparing a bubble-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction. Background Technology

[0002] In the water electrolysis hydrogen production industry, bubbles generated at high current densities accumulate on the electrode surface, forming a "bubble shielding layer" that severely hinders mass transfer and reaction, becoming a key bottleneck restricting electrolysis efficiency and equipment scaling. Existing solutions mainly fall into two categories: one is to accelerate bubble detachment by improving the static wettability of the electrode, but this relies on tangential buoyancy to drive bubble detachment from the electrode surface, failing to overcome the spatial limitations in the electrode's normal direction; the other is to introduce external fields such as ultrasound and magnetic fields for active intervention, but this presents problems such as high energy consumption, complex equipment, and potential damage to the catalyst layer.

[0003] Therefore, there is an urgent need for a novel electrode design principle and preparation technology that can utilize the reaction's own energy to endogenously regulate bubble behavior. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing a bubble-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction. The method utilizes a gradient pore array to guide the normal detachment of bubbles and uses a two-dimensional capillary network of micropillars to continuously replenish the electrolyte, thereby enhancing unidirectional mass transfer and reducing bubble shielding.

[0005] To achieve the above objectives, the present invention provides the following solution: A method for preparing a bubble-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction, comprising: A surface pretreatment is performed on the conductive substrate to obtain a pretreated substrate; A femtosecond laser processing system is used to perform three-dimensional scanning ablation processing on the pre-treated substrate to form a gradient hole array that penetrates the pre-treated substrate. The gradient hole array is a tapered through-hole that penetrates the substrate, with the hole diameter varying linearly or non-linearly along the depth direction and having a large-diameter end and a small-diameter end. A femtosecond laser processing system is used to perform fill-in scanning ablation on a pre-defined columnar region on a pre-treated substrate surface to form a micro-column array; The gradient pore array and the micropillar array are arranged in a spatially interwoven manner, and the two (gradient pore array and micropillar array) together form a three-dimensional through gas-liquid mass transfer channel. The micropillar array is made into a two-dimensional capillary network, and the surface of each micropillar in the micropillar array is made into a micro-nano composite rough structure, so that the micropillar array has superwetting properties and forms a micro-nano structure composite surface. A hydrogen evolution reaction catalyst is loaded onto a micro / nano structure composite surface to form a catalytic active layer, which covers the inner and outer surfaces of the micropillars and gradient pores. During the electrocatalytic hydrogen evolution reaction, the gradient pore array guides the bubbles generated in situ within the gradient pores to detach oriented from the large-diameter end, and forms an asymmetric pressure distribution on both sides of the gradient pores to drive the electrolyte to flow in a predetermined direction, thus forming a unidirectional mass transfer channel for the electrolyte. The micropillar array provides capillary pumping to continuously replenish the electrolyte, resulting in a bubble-driven unidirectional mass transfer electrode.

[0006] Preferably, the conductive substrate is one of nickel, titanium, stainless steel or other conductive materials.

[0007] Preferably, a surface pretreatment is performed on the conductive substrate to obtain a pretreated substrate, comprising: Mechanical polishing is performed on the conductive substrate surface to obtain a mirror-finish surface; The mechanically polished conductive substrate was placed in acetone, anhydrous ethanol and deionized water respectively for ultrasonic cleaning to remove oil stains. The conductive substrate, after ultrasonic cleaning, is immersed in hydrochloric acid solution to perform acid etching to remove the surface oxide layer, and then rinsed with deionized water and dried to obtain a pretreated substrate.

[0008] Preferably, forming a gradient hole array penetrating the pretreated substrate on the pretreated substrate includes: Configure the gradient hole array as a tapered through-hole that penetrates the substrate; The diameter of the tapered through hole is set to vary linearly or non-linearly along the depth direction to form a large-diameter end and a small-diameter end; The diameter of the large aperture end is limited to 400μm to 1000μm, and the diameter of the small aperture end is limited to 100μm to 800μm; The ratio of the large-diameter end diameter to the small-diameter end diameter is limited to 1.2 to 5.0, and the hole depth is limited to 500 μm to 2000 μm; The inclination angle of the hole sidewall is limited to 80° to 110°, and the center distance between adjacent gradient holes is limited to 1.5 to 3.0 times the diameter of the larger hole end.

[0009] Preferably, forming a micropillar array includes: The micropillar array is configured as a periodically arranged columnar structure; The period of the micropillar array is limited to 50 μm to 100 μm, and the height of the micropillar array is limited to 50 μm to 300 μm; The shape of the micro-pillar array is limited to one of the following: cylindrical, square, or regular polygonal pillars. The column diameter is limited to 10 μm to 150 μm, and the column center-to-center spacing is limited to 20 μm to 150 μm.

[0010] Preferably, the gradient pore array and the micropillar array are spatially interwoven, together forming a three-dimensional, interconnected gas-liquid mass transfer channel, including: Place the micropillars around the gradient apertures; or... Some gradient holes are directly fabricated in the micropillar array region.

[0011] Preferably, a micro-nano composite rough structure is formed on the surface of each micropillar in the micropillar array to enable the micropillar array to possess superwetting properties and form a micro-nano composite surface, including: Micro-nano composite rough structures are formed on the surface of micropillars by femtosecond laser processing; This ensures that the contact angle of the micropillar array in the aqueous electrolyte is less than 10°.

[0012] Preferably, a femtosecond laser processing system is used to perform three-dimensional scanning ablation processing on the pretreated substrate, including: The laser power is limited to 8W to 20W; The repetition frequency is limited to 100kHz to 2MHz; The scanning speed is limited to 0.5 m / s to 2 m / s; The number of scans is limited to 30 to 100 to ensure the passage is clear.

[0013] Preferably, a hydrogen evolution reaction catalyst is supported on the micro / nano-structured composite surface to form a catalytically active layer, comprising: Hydrogen evolution reaction catalysts were loaded onto micro / nano-structured composite surfaces using electrochemical deposition, hydrothermal methods, or chemical vapor deposition. The catalyst for the hydrogen evolution reaction is limited to one or more of the following: layered bimetallic hydroxides, transition metal disulfides, transition metal phosphides, alloys, or metal nanoparticles. The thickness of the catalytic active layer is limited to 10 nm to 2 μm; The mass loading of the hydrogen evolution reaction catalyst is limited to 0.5 mg / cm² to 5.0 mg / cm².

[0014] Preferably, the tapered through hole is one of a circular tapered hole, a triangular tapered hole, a rectangular tapered hole, a hexagonal tapered hole, or an irregular polygonal tapered hole.

[0015] The present invention discloses the following technical effects: (1) In the case of hydrogen production by water electrolysis, the present invention addresses the bottleneck of mass transfer obstruction caused by the accumulation of bubbles on the electrode surface to form a bubble shielding layer under high current density conditions. The invention employs a gradient hole array that penetrates the pretreated substrate and defines the large-diameter end and the small-diameter end. This allows the bubbles generated in situ in the gradient holes to detach directionally from the large-diameter end and form an asymmetric pressure distribution on both sides of the gradient holes. This drives the electrolyte to flow in a predetermined direction, forming a unidirectional mass transfer channel for the electrolyte and driving the formation of a unidirectional flow field. This reduces the blockage of the reaction interface caused by bubble coverage from the source and improves the accessibility of the effective reaction area on the electrode surface.

[0016] (2) In view of the problems of existing solutions relying on tangential buoyancy to drive bubble detachment, difficulty in breaking through the electrode normal space limitation, and the introduction of external field intervention such as ultrasound and magnetic field leading to high energy consumption, complex equipment and easy to affect the catalyst layer, the present invention uses an asymmetric pressure field caused by gradient hole array to achieve bubble normal directional detachment. At the same time, a micro-pillar array is formed on the surface of the pretreated substrate and a two-dimensional capillary network is formed. The electrolyte is continuously replenished by capillary pumping, realizing endogenous bubble management without external field energy input and forming a stable unidirectional mass transfer state.

[0017] (3) The present invention forms a three-dimensional gas-liquid mass transfer network by interweaving gradient pore array with micropillar array; micro-nano composite rough structure is formed on the surface of micropillar and has superwetting characteristics; hydrogen evolution reaction catalyst is loaded on the micro-nano structure composite surface to form a catalytic active layer covering the inner and outer surfaces of micropillar and gradient pore, so that electrolyte supply, bubble detachment and active layer utilization form a closed loop synergy, reducing local mass transfer resistance and maintaining continuous renewal of reaction interface, thereby improving the overall mass transfer efficiency of electrode in hydrogen evolution reaction process. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart of the method provided in an embodiment of the present invention; Figure 2 SEM images of the surface morphology of FNCR electrodes prepared by femtosecond laser according to embodiments of the present invention; Figure 3 The SEM image of the cross-sectional morphology of a gradient hole with a radius of 400 μm prepared by femtosecond laser is provided for the embodiments of the present invention. Figure 4 SEM image of a micropillar structure cross-section with a period of 50 μm and a height of 190 μm prepared by femtosecond laser according to an embodiment of the present invention; Figure 5 This is a high-magnification SEM image of the FeCo / FNCR electrode after 1000 cycles of voltammetry activation, provided in an embodiment of the present invention. Figure 6 High-resolution HRTEM image of the FeCo / FNCR electrode provided in an embodiment of the present invention; Figure 7 A high-resolution Fe 2p XPS spectrum of the FeCo / FNCR electrode provided in an embodiment of the present invention; Figure 8 A schematic diagram of the high-resolution Co 2p XPS spectrum of the FeCo / FNCR electrode provided in an embodiment of the present invention; Figure 9 A high-resolution Ni 2p XPS spectrum of the FeCo / FNCR electrode provided in an embodiment of the present invention; Figure 10 The FeCo / FNC electrode and FeCo / FNCR electrode provided in the embodiments of the present invention are used at a current density of 1000 mA·cm⁻¹ -2 Cross-sectional bubble evolution image at time; Figure 11 A schematic diagram of the HER LSV polarization curves of Ni, FNC, FeCo / Ni, FeCo / FNC and FeCo / FNCR electrodes in 1MKOH solution without iR correction, provided for embodiments of the present invention; Figure 12 A schematic diagram of the HERTafel slope curves of Ni, FNC, FeCo / Ni, FeCo / FNC and FeCo / FNCR electrodes provided in the embodiments of the present invention; Figure 13 A schematic diagram of the Nyquist curves of the electrochemical impedance spectroscopy of Ni, FNC, FeCo / Ni, FeCo / FNC and FeCo / FNCR electrodes provided in the embodiments of the present invention; Figure 14 A schematic diagram of the fitting results of the double-layer capacitance C_dl of Ni, FNC, FeCo / Ni, FeCo / FNC and FeCo / FNCR electrodes provided in the embodiments of the present invention; Figure 15 The FeCo / FNCR electrode provided in this embodiment of the invention operates at a current density of 10 mA·cm⁻¹. -2 A schematic diagram showing the volume of hydrogen gas released during water separation for 35 minutes and the corresponding Faraday efficiency under a test area of ​​10mm×10mm. Figure 16A schematic diagram showing the calculated Gibbs free energy change of FeCo-LDH formed after 1000 cyclic voltammetric activation of the FeCo / FNCR electrode provided in this embodiment of the invention along the HER reaction pathway; Figure 17 The FeCo / FNC electrode and FeCo / FNCR electrode provided in the embodiments of the present invention, in 1.0 M KOH solution, have a current density of 10–1000 mA·cm. -2 A schematic diagram of the timing potential curve at that time; Figure 18 The FeCo / FNCR electrode provided in this embodiment of the invention operates at 1000 mA·cm⁻¹ in a three-electrode system. -2 A schematic diagram of the time-potential curve after 1000 hours of operation at industrial current density; Figure 19 The embodiment of the present invention provides a method for handling the same hydrogen flux (=5.2×10). -7 kg·m -2 ·s -1 Simulation statistics of the effect of arrayed holes of different radii (r=200~500 µm) on liquid phase velocity; Figure 20 A schematic diagram illustrating the structural morphology and compositional distribution of the MoS2 / FNCR electrode and the CoP / FNCR electrode constructed by hydrothermal method and phosphating process, respectively, as provided in the embodiments of the present invention. Figure 21 This is a schematic diagram comparing the overall electrocatalytic hydrogen evolution performance of FNC electrodes and FNCR electrodes using different catalyst mounting methods and different catalyst types, as provided in embodiments of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The purpose of this invention is to provide a method for preparing a bubble-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction. The method generates an asymmetric pressure field through a gradient pore array to form a unidirectional flow field, and continuously replenishes the liquid with the help of micro-column capillary pumping, so as to achieve rapid bubble discharge and keep the reaction interface in a renewed state.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0023] Figure 1 A flowchart of the method provided in the embodiments of the present invention, such as Figure 1 As shown, the present invention provides a method for preparing a bubble-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction, comprising: Step 100: Perform surface pretreatment on the conductive substrate to obtain a pretreated substrate; Step 200: The pre-treated substrate is subjected to three-dimensional scanning ablation processing using a femtosecond laser processing system to form a gradient hole array penetrating the pre-treated substrate; the gradient hole array is a tapered through hole penetrating the substrate, the hole diameter varies linearly or non-linearly along the depth direction and has a large-diameter end and a small-diameter end; Step 300: A femtosecond laser processing system is used to perform a fill-in scanning ablation process on a pre-defined columnar region on the surface of the pre-treated substrate to form a micro-column array; Step 400: Arrange the gradient pore array and the micropillar array in a spatially interwoven manner, so that the two together form a three-dimensional through gas-liquid mass transfer channel. Step 500: Make the micropillar array form a two-dimensional capillary network, and make the surface of each micropillar in the micropillar array form a micro-nano composite rough structure, so that the micropillar array has superwetting properties and forms a micro-nano structure composite surface. Step 600: Load the hydrogen evolution reaction catalyst onto the micro / nano structure composite surface to form a catalytic active layer, so that the catalytic active layer covers the inner and outer surfaces of the micropillars and gradient pores; Step 700: During the electrocatalytic hydrogen evolution reaction, the gradient pore array guides the bubbles generated in situ in the gradient pores to detach from the large-diameter end and form an asymmetric pressure distribution on both sides of the gradient pores to drive the electrolyte to flow in a predetermined direction, forming a unidirectional mass transfer channel for the electrolyte. Step 800: The micropillar array provides capillary pumping to continuously replenish the electrolyte, resulting in a bubble-driven unidirectional mass transfer electrode.

[0024] In this embodiment, a bubble-driven unidirectional mass transfer electrode for electrocatalytic hydrogen evolution reaction is provided. The electrode includes a conductive substrate, a micropillar array formed on the surface of the conductive substrate, a gradient pore array penetrating the conductive substrate, and a catalytically active layer loaded on the micro / nano structure composite surface, forming an electrode structure with characteristics of a three-dimensional through-flow gas-liquid mass transfer network and a two-dimensional capillary network.

[0025] The conductive substrate is selected from one of the following alkali-resistant conductive materials: nickel, titanium, or stainless steel (e.g., 304, 316L). The preferred conductive substrate is commercially pure nickel foil with a purity of not less than 99.9% and a thickness of 1 mm to 3 mm, to ensure sufficient mechanical strength and conductivity, while also being suitable for subsequent laser processing and electrochemical applications.

[0026] Micropillar arrays are periodically fabricated on the surface of a conductive substrate. The period of the micropillar array is 50 μm to 100 μm, and the height of the micropillars is 50 μm to 300 μm. In terms of structure and distribution, the micropillar arrays are arranged periodically on the substrate surface, forming a two-dimensional capillary network. Regarding geometric parameters, the column shape is preferably cylindrical, square, or other regular polygonal columns. The column diameter Dp is 10 μm to 150 μm, preferably about 50 μm; the column height Hp is 50 μm to 300 μm, preferably 150 μm to 200 μm; and the column spacing P is 20 μm to 150 μm, preferably about 50 μm. After femtosecond laser processing, a micro-nano composite rough structure is formed on the surface of the micropillars, resulting in a contact angle of less than 10° in the aqueous electrolyte, thus possessing superwetting properties and providing a structural basis for rapid wetting and capillary pumping of the electrolyte.

[0027] The gradient via array is configured as tapered through-holes penetrating the conductive substrate, with the via diameter varying linearly or non-linearly along the depth direction. In terms of geometric parameters, the large-diameter end diameter D_large is 400 μm to 1000 μm, preferably 400 μm to 800 μm; the small-diameter end diameter D_small is 100 μm to 800 μm, preferably 200 μm to 600 μm; the ratio of the aperture size D_large to D_small is 1.2 to 5.0, preferably 1.5 to 2.5. The via depth H_hole is 500 μm to 2000 μm, preferably 800 μm to 1200 μm. The sidewall inclination angle α relative to the substrate plane is 80° to 110°, preferably 95° to 105°. Regarding the via spacing, the center-to-center distance between adjacent gradient vias is 1.5 to 3.0 times the large-diameter end diameter. In terms of spatial relationship, the gradient hole array and the micropillar array are interwoven in space. The micropillars can be arranged around the gradient holes, or some gradient holes can be directly processed in the micropillar array area. Together, they form a three-dimensional gas-liquid mass transfer network, providing channels for the directional detachment of bubbles and the replenishment of electrolyte.

[0028] The catalytic active layer is supported on a micro / nano-structured composite surface of micropillars and gradient pores, forming a supported catalyst structure. The catalytic active layer includes a support and an active component, wherein the support is the aforementioned conductive substrate with a micropillar array and gradient pore array. The active component is a hydrogen evolution reaction catalyst covering the surface of the support, which can be one or more of layered bimetallic hydroxides, transition metal disulfides, transition metal phosphides, alloys, or metal nanoparticles. Layered bimetallic hydroxides include, for example, FeCo-LDH and NiFe-LDH; transition metal disulfides include, for example, MoS2 and WS2; transition metal phosphides include, for example, CoP and Ni2P; and alloys or metal nanoparticles include, for example, FeCo alloys and Pt nanoparticles. Regarding the physical properties of the active layer, the thickness of the catalytic active layer is 10 nm to 2 μm, preferably 50 nm to 200 nm. The mass loading of the catalytically active metal is from 0.5 mg / cm² to 5.0 mg / cm², preferably from 1.0 mg / cm² to 2.0 mg / cm², to maintain good mass transfer channels and electron conduction pathways while ensuring a high density of active sites. This structural configuration enables the electrode to simultaneously achieve efficient gas evolution, rapid bubble removal, and continuous electrolyte replenishment during electrocatalytic hydrogen evolution, providing a structural basis for self-driven unidirectional mass transfer behavior of bubbles.

[0029] Preferably, the key to this embodiment lies in the gradient aperture array, which utilizes the in-situ bubble evolution process to spontaneously generate an asymmetric potential field, thereby driving high-speed local two-phase flow. This flow, which adaptively enhances with increasing current density, actively intervenes in bubble dynamics, fundamentally changing the escape mechanism from "buoyancy-dominated" to "shear-dominated".

[0030] Furthermore, in this embodiment, a method for preparing a bubble-driven unidirectional mass transfer electrode for electrocatalytic hydrogen evolution reaction is provided. The method includes three stages: substrate pretreatment, femtosecond laser micro / nanostructure fabrication, and catalyst active layer loading, to construct a micro / nanostructured composite electrode with a micropillar array, a gradient pore array, and a catalyst active layer loaded on the surface of a conductive substrate.

[0031] In the substrate pretreatment stage, a conductive substrate is selected as the electrode framework material. For example, a nickel foil with dimensions of 10cm × 10cm × 0.1cm is used as the conductive substrate. 3The reagents used for pretreatment include hydrochloric acid (HCl, 3 mol / L), acetone (CH3COCH3), anhydrous ethanol (C2H5OH), and deionized water. The specific steps are as follows: First, the conductive substrate surface is mechanically polished with 2000-grit sandpaper to obtain a mirror-like finish. Then, the polished conductive substrate is sequentially placed in acetone, anhydrous ethanol, and deionized water, and ultrasonically cleaned for 15 to 30 minutes in each solvent to remove surface oil and residual organic impurities. After ultrasonic cleaning, the conductive substrate is immersed in a 3 mol / L HCl solution at room temperature for 5 to 15 minutes to remove the oxide layer on the substrate surface. After acid etching, the conductive substrate surface is rinsed with a large amount of deionized water and dried with nitrogen gas to obtain the pretreated substrate.

[0032] In the femtosecond laser micro / nano structure fabrication stage, a femtosecond laser processing system is used to construct micro / nano structures on the pre-treated substrate. The femtosecond laser processing system includes a femtosecond laser with a center wavelength of 1030 nm, a pulse width of 500 fs, and an adjustable repetition frequency, along with a three-dimensional scanning galvanometer. First, gradient hole array fabrication is performed: when fabricating the gradient holes, the laser power P_hole is set to 8W to 20W, preferably 12W to 18W; the repetition frequency f_hole is set to 100kHz to 2MHz, preferably 500kHz to 1MHz; the scanning speed v_hole is set to 0.5m / s to 2m / s, preferably 0.8m / s to 1.5m / s; and the number of scans N_hole is set to 30 to 100 times to ensure that the gradient holes penetrate the conductive substrate. Based on the pre-designed gradient hole geometry parameters, including the small hole diameter D_small, the large hole diameter D_large, the hole depth H_hole, and the sidewall inclination angle α, the laser power, repetition frequency, scanning speed, scanning path, and focal position are set by the program to control the laser focus to perform three-dimensional scanning ablation inside and on the surface of the substrate, removing material layer by layer, and forming a tapered through gradient hole array with the hole diameter changing linearly or non-linearly along the depth direction.

[0033] Subsequently, the micropillar array is fabricated: During fabrication, the laser power P_pillar is set to 5W to 10W, preferably 7W to 8W; the repetition frequency f_pillar is set to 100kHz to 1MHz, preferably 200kHz to 500kHz; and the scanning speed v_pillar is set to 0.1m / s to 1m / s, preferably 0.2m / s to 0.6m / s. The scanning strategy employs a fill-in scanning method within a pre-defined pillar area, with a line spacing of 50μm to 150μm, preferably approximately 50μm; and the number of scans N_pillar is set to 20 to 100 times, preferably approximately 50 times. Based on the designed micropillar geometry parameters, including pillar diameter D_p, pillar height H_p, and pillar spacing P, the material in the interpillar region is selectively ablated layer by layer using a femtosecond laser in areas with or without fabricated gradient holes, leaving the unablated areas intact and protruding to form the micropillar array. The processing sequence of gradient hole structures and micropillar arrays can be adjusted according to specific design requirements. A preferred approach is to process the gradient hole array with deep hole structures first, and then process the micropillar array with fine surface structures to reduce the risk of damage to the micropillar structures during deep hole processing.

[0034] In the catalyst active layer loading stage, a hydrogen evolution reaction catalytic active layer is loaded onto the micro / nano structure surface formed by femtosecond laser processing using methods such as electrochemical deposition, hydrothermal method, or chemical vapor deposition (CVD). Raw materials include electrodes with completed micro / nano structure processing (e.g., labeled FNC electrode and FNCR electrode) and an electrolyte or reaction solution containing the target metal precursor. Taking the loading of FeCo-LDH precursor by electrochemical deposition as an example, the deposition solution includes 0.05 mol / L to 0.2 mol / L FeSO4·7H2O, 0.1 mol / L to 0.3 mol / L CoSO4·7H2O, 0.3 mol / L to 0.7 mol / L NaH2PO4·2H2O, and 0.1 mol / L to 0.3 mol / L Na3C6H5O7·2H2O (sodium citrate, as a complexing agent). Electrochemical deposition was performed using a three-electrode system, with a micro / nano-structured electrode as the working electrode, a graphite electrode as the counter electrode, and a Hg / HgO electrode as the reference electrode. Deposition was carried out under constant potential or constant current conditions at 25°C: in constant potential mode, the potential was set to −1.8V to −2.2V (relative to Hg / HgO); in constant current mode, the current density was set to −50mA / cm². 2 Up to −200mA / cm 2The deposition time was 100 to 500 s (relative to the geometric area of ​​the conductive substrate). After deposition, the electrode was removed from the deposition solution and rinsed with deionized water and anhydrous ethanol to remove residual electrolyte, and then dried at room temperature. To obtain a FeCo-LDH structure with high hydrogen evolution activity, the electrode was placed in a 1 mol / L KOH solution, and cyclic voltammetry scans were performed at a scan rate of 50 mV / s for 500 to 1000 cycles within a potential window of −0.8 V to 0 V (relative to Hg / HgO) to convert the deposited FeCo alloy into a FeCo-LDH catalytic active layer in situ.

[0035] Taking the hydrothermal method for supporting the MoS2 catalytic active layer as an example, 0.1 mmol / L to 1.0 mmol / L (NH4)6Mo7O is added to deionized water during the preparation of the reaction solution. 24 A homogeneous solution was prepared using 4H₂O and 5 mmol / L to 20 mmol / L CH₃CSNH₂ (thioacetamide). The electrode with the completed micro / nano structure was placed in a stainless steel high-pressure reactor with a polytetrafluoroethylene liner, and the above reaction solution was added to the reactor to achieve a filling degree of 80%. The hydrothermal reaction was carried out at a temperature range of 180℃ to 220℃ for 12 to 24 hours. After the reaction was completed, the electrode was allowed to cool naturally to room temperature, removed, and rinsed with deionized water and anhydrous ethanol to remove residual reactants and byproducts. Subsequently, it was vacuum dried at 60℃ to obtain a micro / nano structured electrode with MoS₂ loaded on its surface.

[0036] For other types of hydrogen evolution catalysts, chemical vapor deposition or other mature loading processes can be used to deposit the catalytic active layer. The appropriate precursor gas source, carrier gas, and reaction atmosphere are selected based on the target catalyst type and thermal stability. Parameters such as reaction temperature, reaction time, and gas flow rate are adjusted within a process window known in the art to achieve uniform deposition of the catalytic active layer on the micro / nanostructure composite surface. Through the above-described substrate pretreatment, femtosecond laser micro / nanostructure construction, and catalytic active layer loading steps, a bubble-driven unidirectional mass transfer electrode with a gradient pore array, micropillar array, and loaded catalytic active layer is obtained, providing a structural basis for achieving directional bubble detachment and continuous electrolyte replenishment during electrocatalytic hydrogen evolution.

[0037] Example 1: Preparation and performance evaluation of FeCo-LDH / FNCR electrode In this embodiment, a nickel sheet is used as a conductive substrate. A gradient pore array and a micropillar array are constructed by femtosecond laser and then loaded with a FeCo-LDH catalytic active layer to obtain a bubble-driven unidirectional mass transfer electrode (labeled as FeCo-LDH / FNCR electrode, or simply FeCo / FNCR electrode).

[0038] In the structural fabrication phase, a femtosecond laser processing system was used to perform two-step laser processing on the nickel sheet. The first step involved a three-dimensional scanning ablation of the nickel sheet using a laser power of 15W and a repetition rate of 1MHz to create gradient holes with a large hole radius of 400μm and a small hole radius of 300μm, each approximately 1mm deep. These gradient holes were arranged periodically in a 5×5 array with a period of 2mm. Subsequently, the laser parameters were adjusted to a power of 7.5W and a repetition rate of 500kHz to perform a fill-in scan on the nickel sheet surface, forming a micropillar array with a period of approximately 50μm and a height of approximately 190μm.

[0039] In the catalytic active layer loading stage, the FNCR electrode with micro-nano structure was placed in the electrodeposition solution for electrochemical deposition to obtain the FeCo alloy precursor deposition layer; then, 1000 cycles of cyclic voltammetric activation were performed in the potential window of 1 mol / L KOH to transform the deposition layer in situ into a layered bimetallic hydroxide structure, thus obtaining the FeCo-LDH / FNCR electrode.

[0040] In terms of structural characterization, scanning electron microscopy (SEM) images showed that the gradient pore array penetrated the nickel substrate with a gradient change in pore size along the depth direction, and the micropillar array was periodically arranged on the nickel sheet surface and spatially interwoven with the gradient pores. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) results confirmed that the catalytic active layer was a FeCo-LDH structure and was successfully loaded on the inner and outer surfaces of the micropillars and gradient pores.

[0041] In terms of bubble behavior testing, an application of 2000 mA / cm² was performed in 1 mol / L KOH. 2 Current density and high-speed imaging results show that hydrogen evolution bubbles detach directionally along the substrate normal direction and are rapidly discharged from the large-diameter end of the gradient pores, realizing unidirectional bubble migration and interface renewal.

[0042] Regarding electrochemical performance, linear sweep spectroscopy showed that the electrode achieved 10 mA / cm² in 1 mol / L KOH. 2 The overpotential required for hydrogen evolution current density is approximately 15 mV, and the Tafel slope is approximately 42 mV / dec. In the constant current durability test, at 1000 mA / cm²... 2 After 1000 hours of continuous operation at current density, the overpotential only increased by about 1%, demonstrating good stability.

[0043] In terms of mass transfer verification, computational fluid dynamics (CFD) simulation and microflow field observation confirmed that the discharge of bubbles in the gradient hole induces local flow, forming a unidirectional high-speed microflow field along the channel direction. The local flow velocity can reach more than 3.25 mm / s and increases with the increase of current density and gas flux, indicating that the electrode has the ability to self-drive fluid supply under high current density.

[0044] Example 2: Fabrication of MoS2 / FNCR electrode (hydrothermal loading) In this embodiment, an FNCR electrode with a gradient pore and micropillar structure formed by femtosecond laser processing was used as a substrate, and a MoS2 catalytic active layer was loaded via a hydrothermal reaction. The FNCR electrode was placed in a solution containing 0.1 mmol / L to 1.0 mmol / L (NH4)6Mo7O 24 The reaction solution of 4H₂O and 5 mmol / L to 20 mmol / L CH₃CSNH₂ was placed in a reaction vessel lined with polytetrafluoroethylene and reacted at 180 °C to 220 °C for 12 h to 24 h. After cooling, washing, and drying, a MoS₂ / FNCR electrode was obtained. SEM and TEM results showed that MoS₂ sheets uniformly covered the inner and outer surfaces of the micropillars and gradient pores. Electrochemical tests showed that the overpotential of the MoS₂ / FNCR electrode was lower than that of the MoS₂ electrode without the micro / nano structure, and the bubble detachment behavior was significantly improved under high current density.

[0045] Example 3: Preparation of CoP / FNCR electrode (hydrothermal + phosphating) In this embodiment, a Co-based precursor is first loaded using a hydrothermal method, followed by CoP formation using a chemical vapor deposition (CVD) process. The hydrothermal step places the FNCR electrode in a Co-containing substrate. 2+ The precursor was reacted in a reaction solution to obtain a Co-based hydrothermal deposition layer; subsequently, the electrode was placed in a chemical vapor phase reactor containing a P source gas for phosphating, converting the precursor into CoP. Characterization and electrochemical tests both showed that the CoP / FNCR electrode had higher catalytic activity and stronger mass transfer capability.

[0046] Figure 2 This is a SEM image of the FNCR electrode surface after femtosecond laser processing. The image shows a periodic micro / nano structure on the surface after femtosecond laser scanning ablation, providing a foundational surface roughening structure for subsequent micropillar array processing and catalytic active layer loading, while ensuring good structural continuity and mechanical support on the electrode surface. Figure 3 This is a SEM image of the gradient hole cross-section fabricated by a femtosecond laser. The gradient hole cross-section has a conical structure, with the hole diameter gradually increasing from the smaller diameter end to the larger diameter end along the depth direction, with a radius of approximately 400 μm and a sidewall angle of approximately 100°. The internal structure of the hole is intact and penetrates the substrate thickness, providing a physical channel for the directional discharge of gas along the normal direction and the formation of an asymmetric pressure field during subsequent electrocatalysis. Figure 4 This is a SEM image of the cross-section of the micropillar structure fabricated by a femtosecond laser. The micropillars have a period of approximately 50 μm and a height of approximately 190 μm, arranged in a regular array. The micropillars form a two-dimensional capillary network and provide a capillary pumping path for electrolyte replenishment. Their fabrication dimensions and period, along with the spatial distribution of the gradient hole array, form a synergistic structure, enabling gas-liquid dual-channel mass transfer. Figure 5This is a high-magnification SEM image of the FeCo / FNCR electrode after 1000 cycles of cyclic voltammetry activation. The image shows a continuous deposition of the catalytic active layer on the surface of the micropillar and the inner and outer walls of the gradient pores. The surface exhibits a lamellar or clustered stacked structure, providing a high density of active sites for the electrocatalytic hydrogen evolution reaction. Figure 6 This is a high-resolution HRTEM image of the FeCo / FNCR electrode. The lattice fringes are clearly resolved, and the nanoscale lattice structure and phase boundary features can be observed, indicating that the formed catalytic active layer possesses nanoscale structural integrity, providing structural evidence for studying the microscopic origin of catalytic activity. Figure 7 This is the high-resolution XPS spectrum of Fe 2p from the FeCo / FNCR electrode. The figure shows the Fe 2p... 3 / 2 and Fe 2p 1 / 2 Peak fitting showed Fe 2+ with Fe 3+ The coexistence state indicates that the Fe element in the active layer has multiple valence states. Figure 8 High-resolution XPS spectra of Co 2p in FeCo / FNCR electrodes. 3 / 2 and Co 2p 1 / 2 Peak fitting yields Co 2+ and Co 3+ The valence state signal indicates that cobalt in the deposited catalyst also exhibits a multivalent structure. Figure 9 High-resolution XPS spectrum of Ni 2p for FeCo / FNCR electrode. The Ni 2p signal indicates Ni 2+ The presence of valence state as the dominant catalytic state, accompanied by satellite peak characteristics, further verifies that the FeCo-LDH catalytic active layer can form a stable interface with the nickel-based support.

[0047] Figure 10 It demonstrates the effect at a current density of 1000 mA·cm -2 The differences in the cross-sectional evolution behavior of bubbles when using FeCo / FNC electrodes and FeCo / FNCR electrodes under different conditions. Figure 10 Part a corresponds to the FeCo / FNC electrode. During electrolysis, bubbles mainly grow and aggregate along the electrode surface, disperse in the detachment direction, and do not form a clear local electrolyte flow path. Figure 10 Part b in the diagram corresponds to the FeCo / FNCR electrode. Under the same conditions, bubbles generated within the gradient pore array region detach directionally along the normal direction, forming a visible electrolyte flow field around the electrode, thus replenishing the electrode surface with electrolyte. This bubble evolution image provides experimental observational evidence for subsequent analysis of the influence of gradient pore array and micropillar array structures on gas-liquid mass transfer behavior.

[0048] Figure 11The linear sweep voltammetric polarization curves of Ni, FNC, FeCo / Ni, FeCo / FNC, and FeCo / FNCR electrodes obtained in 1M KOH solution are shown. The sweep rate was 1 mV·s. -1 Furthermore, iR compensation was not performed. The current density-potential relationship of different electrodes in the figure allows for a direct comparison of the hydrogen evolution current output level of each electrode at the same overpotential, providing experimental basis for evaluating the hydrogen evolution activity of the FeCo / FNCR electrode in the entire series of electrodes. Figure 12 Tafel slope curves for Ni, FNC, FeCo / Ni, FeCo / FNC, and FeCo / FNCR electrodes are presented. Each data point is derived from... Figure 11 The polarization curves were converted from those in the figure, with the ordinate representing overpotential and the abscissa representing the logarithm of current density. The Tafel slopes of different electrodes reflect the kinetic characteristics of the hydrogen evolution reaction. The FeCo / FNCR electrode corresponds to a lower Tafel slope value, indicating that this structure has faster reaction kinetics in the HER process. Figure 13 The Nyquist plots for Ni, FNC, FeCo / Ni, FeCo / FNC, and FeCo / FNCR electrodes under HER operating conditions are shown. The horizontal axis represents the real impedance Z', and the vertical axis represents the negative imaginary impedance −Z''. By comparing the semicircular diameter and high-frequency intersection position of each electrode, the differences in charge transfer resistance and interfacial resistance of different electrode structures can be analyzed. Among them, the FeCo / FNCR electrode exhibits a relatively small charge transfer resistance, which is beneficial to the rapid charge transfer at the catalytic interface. Figure 14 The relationship between the current density difference measured at different scan rates and the scan rate for Ni, FNC, FeCo / Ni, FeCo / FNC, and FeCo / FNCR electrodes is shown, which is used to fit the double-layer capacitance C_dl. The slope of each straight line corresponds to the C_dl value of the corresponding electrode, which can be used as an indirect characterization of the apparent electrochemical specific surface area of ​​the electrode. The FeCo / FNCR electrode corresponds to a larger C_dl value, indicating that the micro / nano-structured composite surface and the catalytic active layer provide more effective area to participate in electrochemical reactions. Figure 15 FeCo / FNCR electrode in 1M KOH solution at 10 mA·cm -2 The hydrogen evolution volume and Faraday efficiency of water electrolysis at the given current density for 35 min are shown in the figure. The dotted line in the figure represents the comparison between the actual collected H2 volume and the theoretically calculated volume, along with the corresponding Faraday efficiency. The results indicate that under the given conditions, the actual hydrogen production of the FeCo / FNCR electrode is highly consistent with the theoretical value, and the Faraday efficiency is close to 100%, verifying the charge-mass conversion efficiency of the electrode during long-term hydrogen evolution. Figure 16The free energy changes of the FeCo-LDH catalytic phase formed on the FeCo / FNCR surface after 1000 cyclic voltammetric activation along the HER reaction pathway are presented in the graph. The horizontal axis represents the reaction axis, and the vertical axis represents the corresponding intermediates (including H). Gibbs free energies for the adsorbed state and for the formation of 1 / 2 H2. The figure shows the free energy curves for different active sites (e.g., Fe sites and Co sites), used to compare the thermodynamic advantages of each site for hydrogen adsorption and desorption processes, providing theoretical support for explaining the high HER activity exhibited by FeCo-LDH on this electrode. Figure 17 FeCo / FNC and FeCo / FNCR electrodes were tested in 1.0 M KOH solution at different current densities (10, 50, 100, 200, 300, 400, 500 and 1000 mA·cm). -2 The chronopotential curves are shown. The horizontal axis represents the test time, and the vertical axis represents the potential relative to the reversible hydrogen electrode. Different colored segments correspond to different current density conditions and can be used to evaluate the potential stability of the electrode under various current loads. The FeCo / FNCR electrode exhibits small potential decay at high current densities, indicating that this structure has good electrochemical stability under long-term high-current operation.

[0049] Figure 18 The results show the performance of the FeCo / FNCR electrode in a three-electrode system in 1M KOH electrolyte at 1000 mA·cm⁻¹. -2 The chronopotential curves for the electrocatalytic hydrogen evolution reaction at current density were obtained at a test temperature of 25℃. As shown in the figure, during continuous operation for 1000 hours, the electrode operating potential exhibited a slow and controllable upward trend, without significant potential abrupt changes or deactivation, indicating that the FeCo / FNCR electrode possesses good electrochemical stability under industrial current density conditions. The "Refresh electrolyte / 120h" label in the figure corresponds to electrolyte replacement every 120 hours to avoid interference from electrolyte concentration changes on the potential readings. These results verify the long-term durability of the described multi-scale structure electrode under strong gas evolution environment and high current density, providing experimental evidence for its application in industrial-scale water electrolysis.

[0050] Figure 19 The results show that under the same hydrogen flux conditions (5.2 × 10⁻⁶), -7 kg·m -2 ·s -1 The influence of gradient aperture pore arrays with different aperture sizes on the liquid phase velocity field and liquid phase streamline distribution is shown below. Figure 19As shown in figures a1 to a4, the liquid phase velocity field distribution obtained by finite element simulation shows significant differences when the pore sizes are 200 μm (FNCR-200), 300 μm (FNCR-300), 400 μm (FNCR-400), and 500 μm (FNCR-500), respectively. The velocity field exhibits localized enhancement in the central region of the gradient pores, while the velocity diffusion region expands outward with increasing pore size. Figures b1 to b4 show the three-dimensional trajectory distribution of the liquid phase streamlines. As can be seen from the figures, the gas generated within the gradient pores drives the liquid to flow continuously along the pore direction. The spatial distribution and reflux morphology of the streamlines differ under different pore size conditions; increasing the pore size leads to enhanced liquid phase disturbance and an expansion of the streamline range. The simulation results of this embodiment verify the controllable effect of the gradient pore structure scale on localized liquid convection and flow disturbance, providing a theoretical basis for the self-driven unidirectional mass transfer phenomenon in the subsequent electrocatalytic gas evolution process.

[0051] Figure 20 The structural morphology and compositional distribution characterization of MoS2 / FNCR and CoP / FNCR electrodes constructed via hydrothermal and phosphating processes, respectively, are shown. Figure 20 As shown in section a1, the scanning electron microscope image of the MoS2 / FNCR electrode shows that the gradient pore structure and the micropillar array remain intact, indicating that the hydrothermal growth process did not destroy the multi-scale structural framework formed by laser processing. Figure 20 As shown in section a2, high-magnification scanning electron microscopy images reveal a rough nanostructure composed of stacked MoS2 nanosheets formed on the surface of the micropillars and pore walls, which is beneficial for increasing the density of catalytic active sites. Figure 20 As shown in section a3, the energy dispersive spectroscopy (EDS) elemental distribution diagram of the MoS2 / FNCR electrode shows that Mo, S, Ni and O elements are uniformly distributed, with Mo and S elements mainly distributed on the surface of the micropillars and pore walls, verifying the successful loading of the MoS2 catalyst layer.

[0052] Correspondingly, such as Figure 20 As shown in section b1, scanning electron microscopy images of the CoP / FNCR electrode reveal a continuous and complete nanoparticle structure forming in both the gradient pore region and the micropillar region. Figure 20 As shown in section b2, high-magnification scanning electron microscopy images further reveal that the structure is mainly composed of fine-scale granular CoP growth bodies, covering the surface of the micropillars and the sidewalls of the gradient pores. Figure 20 As shown in section b3, the energy dispersive spectroscopy (EDS) elemental distribution diagram proves that Co, P, Ni and O elements have a uniform distribution on the surface. The co-distribution of Co and P elements characterizes the existence of the CoP phase after phosphating, indicating that the catalytic active layer was successfully loaded on the FNCR electrode structure.

[0053] Figure 21This paper presents a comparison of the overall electrocatalytic hydrogen evolution performance of FNC and FNCR electrodes using different catalyst loading methods and catalyst types. Specifically, it includes FeCo / FNC and FeCo / FNCR electrodes with FeCo catalyst supported by electrodeposition, MoS2 / FNC and MoS2 / FNCR electrodes with MoS2 catalyst supported by hydrothermal method, and CoP / FNC and CoP / FNCR electrodes with CoP catalyst supported by a combined hydrothermal and CVD method. Figure 21 HER were selected at 10 mA·cm -2 and 100mA·cm -2 Overpotential η at time 10 With η 100 Tafel slope, double-layer capacitance C_dl, and bubble contact angle are used as comprehensive performance indicators to characterize key performance parameters of the electrode, such as catalytic kinetics, aqueous wettability, and the number of surface active sites. Figure 21 It is evident that, under the same catalyst and loading method, the FNCR electrode exhibits superior results in all five indicators mentioned above. Compared with the corresponding FNC electrode, it has lower overpotential, smaller Tafel slope, higher double-layer capacitance, and larger bubble contact angle. This indicates that the FNCR structure constructed using gradient pore array and micropillar two-dimensional capillary network helps to improve aqueous phase diffusion, reduce bubble coverage, and enhance the effective utilization of the electrode active surface.

[0054] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0055] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for preparing a bubble-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction, characterized in that, include: A surface pretreatment is performed on the conductive substrate to obtain a pretreated substrate; A femtosecond laser processing system is used to perform three-dimensional scanning ablation processing on the pretreated substrate to form a through-hole array on the pretreated substrate; the gradient hole array is a tapered through-hole that penetrates the substrate, the hole diameter varies linearly or non-linearly along the depth direction and has a large-diameter end and a small-diameter end; The femtosecond laser processing system is used to perform a fill-in scanning ablation process on a preset columnar region on the surface of the pretreated substrate to form a micro-column array; The gradient pore array and the micropillar array are arranged in a spatially interwoven manner, together forming a three-dimensional through gas-liquid mass transfer channel. The micropillar array is made into a two-dimensional capillary network, and the surface of each micropillar in the micropillar array is made into a micro-nano composite rough structure, so that the micropillar array has superwetting properties and forms a micro-nano structure composite surface. A hydrogen evolution reaction catalyst is loaded onto the micro / nano structure composite surface to form a catalytic active layer, which covers the inner and outer surfaces of the micropillar and the gradient pores. During the electrocatalytic hydrogen evolution reaction, the gradient pore array guides the bubbles generated in situ within the gradient pores to detach oriented from the large-diameter end, and forms an asymmetric pressure distribution on both sides of the gradient pores to drive the electrolyte to flow in a predetermined direction, thus forming a unidirectional mass transfer channel for the electrolyte. The micropillar array provides capillary pumping to continuously replenish the electrolyte, resulting in the bubble-driven unidirectional mass transfer electrode.

2. The method for preparing a bubble-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction according to claim 1, characterized in that, The conductive substrate is one of nickel, titanium, stainless steel or other conductive materials.

3. The method for preparing a bubble-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction according to claim 1, characterized in that, A surface pretreatment is performed on the conductive substrate to obtain a pretreated substrate, including: Mechanical polishing is performed on the surface of the conductive substrate to obtain a mirror-finished surface; The mechanically polished conductive substrate was placed in acetone, anhydrous ethanol and deionized water respectively for ultrasonic cleaning to remove oil stains. The conductive substrate, after ultrasonic cleaning, is immersed in hydrochloric acid solution to perform acid etching to remove the surface oxide layer, and then rinsed with deionized water and dried to obtain the pretreated substrate.

4. The method for preparing a bubble-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction according to claim 1, characterized in that, Forming a through-hole array on the pretreated substrate includes: The gradient hole array is configured as a tapered through-hole penetrating the substrate; The diameter of the tapered through hole is set to vary linearly or non-linearly along the depth direction to form the large-diameter end and the small-diameter end; The diameter of the large aperture end is limited to 400 μm to 1000 μm, and the diameter of the small aperture end is limited to 100 μm to 800 μm; The ratio of the diameter of the large aperture end to the diameter of the small aperture end is limited to 1.2 to 5.0, and the aperture depth is limited to 500 μm to 2000 μm; The inclination angle of the hole sidewall is limited to 80° to 110°, and the center distance between adjacent gradient holes is limited to 1.5 to 3.0 times the diameter of the large-diameter end.

5. The method for preparing a bubble-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction according to claim 1, characterized in that, Forming a micropillar array includes: The micropillar array is configured as a periodically arranged column structure; The period of the micropillar array is limited to 50 μm to 100 μm, and the height of the micropillar array is limited to 50 μm to 300 μm; The shape of the micro-pillar array is limited to one of the following: cylindrical, square, or regular polygonal pillars. The column diameter is limited to 10 μm to 150 μm, and the column center-to-center spacing is limited to 20 μm to 150 μm.

6. The method for preparing a bubble-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction according to claim 1, characterized in that, The gradient pore array and the micropillar array are spatially interwoven, together forming a three-dimensional, interconnected gas-liquid mass transfer channel, including: The micropillars are positioned around the gradient apertures; or... Some of the gradient holes are directly fabricated in the micropillar array region.

7. The method for preparing a bubble-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction according to claim 1, characterized in that, To create a micro-nano composite rough structure on the surface of each micropillar in the micropillar array, thereby enabling the micropillar array to possess superwetting properties and form a micro-nano composite surface, including: The micro-nano composite rough structure is formed on the surface of the micropillars by femtosecond laser processing; The contact angle of the micropillar array in the aqueous electrolyte is less than 10°.

8. The method for preparing a bubble-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction according to claim 1, characterized in that, The pretreated substrate is subjected to three-dimensional scanning ablation processing using a femtosecond laser processing system, including: The laser power is limited to 8W to 20W; The repetition frequency is limited to 100kHz to 2MHz; The scanning speed is limited to 0.5 m / s to 2 m / s; The number of scans is limited to 30 to 100 to ensure the passage is clear.

9. The method for preparing a bubble-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction according to claim 1, characterized in that, A hydrogen evolution reaction catalyst is supported on the micro / nano structure composite surface to form a catalytically active layer, including: The hydrogen evolution reaction catalyst was loaded onto the micro / nano structure composite surface using electrochemical deposition, hydrothermal method, or chemical vapor deposition. The hydrogen evolution reaction catalyst is limited to one or more of layered bimetallic hydroxides, transition metal disulfides, transition metal phosphides, alloys, or metal nanoparticles. The thickness of the catalytic active layer is limited to 10 nm to 2 μm; The mass loading of the hydrogen evolution reaction catalyst is limited to 0.5 mg per square centimeter to 5.0 mg per square centimeter.

10. The method for preparing a bubble-driven mass transfer electrode for electrocatalytic hydrogen evolution reaction according to claim 1, characterized in that, The tapered through hole is one of the following: a circular tapered hole, a triangular tapered hole, a rectangular tapered hole, a hexagonal tapered hole, or an irregular polygonal tapered hole.

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