Single-side catalyst layer preparation method based on removable masking layer and integrated electrode

Abstract

The invention discloses a preparation method of a single-side catalyst layer based on a removable masking layer and an integrated electrode, and relates to the technical field of water electrolysis hydrogen production and electrochemical device electrode manufacturing. The method comprises the following steps: providing a porous conductive substrate which comprises a first side surface and a second side surface opposite to the first side surface; covering the first side surface with a removable masking material in a molten state or a solution state, so that the removable masking material permeates into the pores of the side surface but does not protrude out of the surface of the upper hole of the second side surface, and forming a masking layer after curing; applying catalyst slurry on the second side surface to form a catalyst layer precursor; carrying out heat treatment on the catalyst layer precursor to shape the catalyst layer precursor; and removing the masking layer to obtain the integrated electrode of which only the second side surface is loaded with the catalyst layer. According to the invention, the temporary masking layer which can be completely removed is introduced to selectively block one side and internal pores of the PTL in the loading process, so that an efficient catalyst layer is only formed on the working surface on the other side, and a technical basis is provided for realizing a high-performance and low-cost PEM electrolytic cell.

Description

Technical Field

[0001] This invention relates to the field of water electrolysis for hydrogen production and the manufacture of electrodes for electrochemical devices, specifically to a method for preparing a single-sided catalytic layer based on a removable masking layer and an integrated electrode. Background Technology

[0002] Proton exchange membrane electrolysis (PEMWE) technology is a key approach to producing high-purity "green hydrogen." Its core component, the membrane electrode assembly (MEA), typically employs an integrated anode structure, where the catalyst layer is directly supported on a porous transport layer (PTL). The PTL is usually made of titanium-based porous materials such as titanium felt or sintered titanium fiber plates, serving multiple functions including electron conduction, transport of reactant water, and oxygen removal.

[0003] Currently, catalyst loading is commonly achieved by coating the catalyst slurry onto the PTL surface using methods such as blade coating, spraying, or screen printing. However, due to the inherent three-dimensional interconnected porous structure of the PTL, this method has a serious inherent drawback: (1) Extremely low catalyst utilization: During the coating process, the catalyst slurry inevitably penetrates into the internal pores of the PTL under the action of capillary force, and may even penetrate completely to the back side. In actual operation, only the catalyst on the surface that is in direct contact with the proton exchange membrane participates in the electrochemical reaction, while the expensive precious metal catalysts (such as iridium and ruthenium oxides) that penetrate into the interior and back side are completely wasted, resulting in a catalyst utilization rate that is usually less than 50%, which significantly increases the manufacturing cost of PEM electrolyzers.

[0004] (2) Deterioration of electrode mass transfer performance: Ineffective catalyst permeation will block the inherent pores of the PTL, significantly increasing the resistance to the transport of reaction water to the catalyst layer and the discharge of generated oxygen. This will exacerbate mass transfer polarization under high current density conditions, leading to increased cell voltage, decreased efficiency, and the potential formation of hot spots due to poor local oxygen evolution, thus damaging the membrane electrode life.

[0005] To address the aforementioned issues, existing technologies have made some attempts, but all have significant limitations. For example, using low-concentration, high-viscosity slurries can reduce permeation to some extent, but it is difficult to precisely control the thickness and uniformity of the catalyst layer, and it cannot completely eliminate permeation. While hot-press transfer or direct deposition (such as sputtering) processes can achieve shallow surface loading, the equipment is complex, the cost is high, the production capacity is low, and the bonding force between the deposited layer and the porous substrate is often weak, making it difficult to meet the needs of large-scale commercial production.

[0006] More importantly, existing technologies lack a simple, efficient, and low-cost solution for achieving precise and controllable loading of catalysts on one side of a PTL. The industry urgently needs a new method that can leverage the advantages of mature slurry coating processes while physically preventing slurry penetration into non-working areas, thereby achieving cost-effective use of precious metal catalysts and the manufacture of high-performance electrodes. Summary of the Invention

[0007] To address the above problems, this invention provides a method for preparing a single-sided catalytic layer based on a removable masking layer and an integrated electrode. By introducing a completely removable temporary masking layer, one side and internal pores of the PTL are selectively blocked during loading, thereby forming a highly efficient catalytic layer only on the other working surface. This provides a technical basis for achieving high-performance, low-cost PEM electrolyzers. This enables precise and efficient loading of noble metal catalysts on porous conductive substrates, fundamentally solving the problems of low utilization and deteriorated mass transfer performance caused by ineffective catalyst permeation.

[0008] According to a first aspect of the present invention, a method for preparing a single-sided catalytic layer based on a removable masking layer is provided, wherein the preparation method includes the following steps: (1) A porous conductive substrate is provided, the substrate including a first side and a second side opposite thereto; (2) A molten or solution-state removable masking material is used to cover the first side of the substrate, so that the removable masking material penetrates into the pores of the side surface but does not protrude from the pore surface of the second side surface, and forms a masking layer after solidification; (3) Apply catalyst slurry to the second side surface to form a catalyst layer precursor; (4) The catalyst precursor is heat-treated to set its shape; (5) Remove the masking layer to obtain an integrated electrode with a catalyst layer loaded only on the second side.

[0009] Furthermore, the removable masking material is selected from paraffin wax, hot melt adhesive, or water-soluble polymer; the porous conductive substrate is titanium felt, titanium fiber sintered plate, or carbon paper.

[0010] Furthermore, when the removable masking material is paraffin wax, it is heated to a molten state and then applied, and the wetting time and temperature are controlled to allow it to penetrate into the pores. The melting point of the paraffin wax is 50-70°C. When the removable masking material is hot melt adhesive, it is applied to the first side and internal cavities by spraying or hot pressing in a molten state. The melting point of the hot melt adhesive is 80-120°C. When the removable masking material is a water-soluble polymer, it is prepared into an aqueous solution and then scraped or sprayed onto the first side surface to wet the internal pores, and then dried to form a film. The water-soluble polymer is polyvinyl alcohol (PVA), agarose, or gelatin, and the aqueous solution concentration is 5-15 wt%.

[0011] Further, in step (2), the removable masking material is applied by scraping, rolling, dipping or spraying.

[0012] Furthermore, in step (3), the catalyst slurry is applied by scraping, spraying or screen printing.

[0013] Further, in step (4), the heat treatment is carried out in air or an inert atmosphere, heated to 250-450°C at a rate of 1-5°C / min, and held at that temperature for 0.5-2 hours.

[0014] Furthermore, in step (5), If the removable masking material is paraffin or hot melt adhesive, it can be removed by heating the electrode to 20-50°C above the melting point of the masking material to make it melt and flow out, and then wiping or cleaning with a low-boiling-point organic solvent. If the removable masking material is a water-soluble polymer, it can be dissolved and peeled off by immersing the electrode in water or using an ultrasonic water bath.

[0015] According to a second aspect of the present invention, an integrated electrode prepared by any of the above methods is provided, wherein the catalytic layer of the integrated electrode is precisely loaded only on the second side of the porous conductive substrate, and its first side and internal pores remain clean and porous.

[0016] According to a third aspect of the present invention, a membrane electrode is provided, wherein it includes an integrated electrode as described above.

[0017] According to a fourth aspect of the present invention, an electrolytic cell is provided, comprising a membrane electrode as described above, wherein the electrolytic cell is a proton exchange membrane electrolytic cell or an anion exchange membrane electrolytic cell.

[0018] Based on the above technical solution, the present invention overcomes the limitations of traditional direct coating technology and achieves the following significant advancements: (1) Revolutionary improvement in catalyst utilization: The temporary shielding layer physically blocks the penetration path of the catalyst slurry into the non-working area. Example 1 shows that the utilization rate of noble metal catalysts (such as Ir) can be increased from <50% to >90% in the traditional method, directly reducing the electrode manufacturing cost by more than 30%. (2) Optimization of overall electrode performance: Effectively avoids mass transfer deterioration caused by catalyst pore blockage, and maintains the original gas-liquid transport channels of the porous substrate. The prepared electrode performs well at high current densities (>2 A / cm²). 2 It exhibits lower concentration polarization and more stable tank voltage. (3) Excellent process versatility and compatibility: The masking material is inexpensive, easy to remove and leaves no residue. Paraffin and hot melt adhesive are suitable for aqueous or organic catalyst slurries, while water-soluble polymers are suitable for organic slurries. This method is seamlessly compatible with existing mature scraping and spraying processes, requires no complex and expensive equipment, and is easy to scale up for production. (4) Enhanced electrode quality and reliability: Since the catalyst layer exists only on the working surface, its bonding force with the substrate and the density and uniformity of the catalyst layer are improved. At the same time, it avoids the potential corrosion damage to the porous titanium substrate caused by harsh pretreatment conditions such as strong acids and strong alkalis, thus ensuring the long-term service life of the electrode. Attached Figure Description

[0019] Figure 1 This is a process flow diagram of the method described in this invention.

[0020] Figure 2 This is a schematic diagram of the paraffin-masking process in Embodiment 1 of the present invention.

[0021] Figure 3 This is a comparative schematic diagram of electrodes obtained by the conventional method and the method of the present invention.

[0022] Figure 4 This is a schematic diagram of the explosive decomposition of the integrated electrode prepared by the present invention applied to the membrane electrode assembly of a PEM electrolyzer. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to embodiments. Those skilled in the art can make adaptive adjustments to the process parameters without departing from the core principles of this invention.

[0024] This invention provides a method for preparing a single-sided catalyst layer based on a removable masking layer and an integrated electrode. It is particularly suitable for addressing the problems of low utilization, high cost, and hindered mass transfer caused by ineffective loading of noble metal catalysts inside porous conductive substrates and on non-working surfaces in technologies such as proton exchange membrane (PEM) water electrolysis and anion exchange membrane (AEM) water electrolysis. Similar technical challenges also exist in fields such as anion exchange membrane water electrolysis (AEMWE) and fuel cells that use porous gas diffusion electrodes.

[0025] The core of the method involves using one of paraffin wax, hot melt adhesive, or water-soluble polymer as a temporary masking material. This material is applied in molten or solution form and impregnated into one side of the surface and near-surface pores of a porous conductive substrate, forming a physical barrier layer after solidification. Subsequently, a catalyst slurry is coated on the exposed surface of the other side of the substrate, and the slurry is confined to that side surface and cannot penetrate. Finally, the masking material is completely removed by heating, dissolving, or peeling to obtain a functionalized electrode with a catalyst layer on only one side.

[0026] Substrate composition: The porous conductive substrate includes porous electrode substrates suitable for water electrolysis or fuel cells, such as titanium felt, titanium fiber sintered plate, carbon paper or nickel foam.

[0027] Masking materials and process parameters: Paraffin wax: Select refined paraffin wax or microcrystalline wax with a melting point of 50-70℃. Heat it to a molten state (70-90℃) and apply it to one side of the substrate by scraping, rolling or dipping. Control the depth of penetration to ensure that it does not penetrate to the other side of the substrate. Hot melt adhesives: Select low melting point (80-120℃), easy-to-peel ethylene-vinyl acetate (EVA) copolymer-based hot melt adhesives, and apply them to one side of the substrate by molten spraying or film hot pressing. Water-soluble polymers: Prepare a 5-15 wt% aqueous solution using polyvinyl alcohol (PVA), agarose, or gelatin, apply by scraping or spraying, and then dry to form a film.

[0028] The method for preparing the single-sided catalyst layer includes the following steps: Substrate pretreatment: The porous conductive substrate is placed in ethanol, acetone and deionized water in sequence for ultrasonic cleaning to remove surface oil and impurities. The cleaning is repeated three times and then dried for later use. Masking layer application and curing: The selected masking material is uniformly applied to the entire surface of one side of the pretreated substrate in molten or solution form. By controlling the pressure, temperature or vacuum conditions, it is promoted to penetrate into the pores. Then, it is cooled to room temperature or dried to allow it to fully cure, forming a sealed plug. Catalyst slurry loading: On the unmasked surface of the substrate, the catalyst slurry (such as iridium black, IrO2 and other water electrolysis catalyst slurries) is loaded onto it by means of scraping, spraying or screen printing. Catalytic layer shaping: Dry the loaded electrode at 80-120℃, and then heat treat it at 250-450℃ for 0.5-2 hours in air or an inert atmosphere to solidify the catalytic layer. Masking layer removal: If the masking layer is paraffin or hot melt adhesive, it will automatically melt and flow out when the temperature is raised above its melting point during the heat treatment and shaping process of the catalyst layer. For residual masking layers that have not completely detached after heat treatment, the electrode can be reheated to 20-50°C above its melting point to promote further melting, and then removed by pouring, gas purging, or wiping with a lint-free cloth. If necessary, low-boiling-point organic solvents (such as n-hexane or petroleum ether) can be used for auxiliary cleaning to ensure no residue remains. If the masking layer is a water-soluble polymer, immerse the electrode in deionized water and ultrasonically vibrate it until the masking layer is completely dissolved and peeled off. Post-processing: The electrode after removing the masking layer is dried to obtain an integrated electrode with a single-sided catalytic layer.

[0029] Specifically, including: (1) Definition of substrate: The porous conductive substrate includes, but is not limited to: titanium felt (porosity 35%-80%, thickness 0.2-2.0mm), titanium fiber sintered board (porosity 20%-60%, thickness 0.5-2.0mm) or carbon paper (porosity 70%-85%, thickness 0.1-0.3mm). (2) Pretreatment: The substrate is ultrasonically cleaned in ethanol, acetone and deionized water for 10-30 minutes each, and then dried in a 60-80℃ drying oven for more than 30 minutes to ensure that surface contaminants and moisture are completely removed. (3) Covering materials: * Paraffin wax: Refined paraffin wax with a melting point of 58-62℃ is selected; * Hot melt adhesive: Transparent low-melting-point hot melt adhesive sticks with ethylene-vinyl acetate (EVA) base and a melting point of approximately 85°C; * Water-soluble polymer: Polyvinyl alcohol (PVA) with a degree of hydrolysis >99% and a molecular weight of approximately 75,000 is selected and prepared into an 8-12 wt% aqueous solution; (4) Catalyst slurry: Typical PEM water electrolysis anode catalyst slurry may contain a mixture of IrO2, Nafion ionomer, and water / alcohol solvent, with a solid content of 5-20 wt%; (5) Heat treatment shaping: The heat treatment of the catalyst layer is carried out in air or inert atmosphere, with a heating rate of 1-5℃ / min, a target temperature of 250-450℃, and a holding time of 0.5-2 hours.

[0030] Figure 1 The diagram sequentially illustrates (a) cleaning the porous conductive substrate; (b) applying and curing a masking layer on the first side of the substrate; (c) loading a catalyst slurry on the second side of the substrate; (d) heat treatment to shape the catalyst layer; and (e) removing the masking layer to obtain the final product—an integrated electrode with a single-sided catalyst layer. This diagram clearly demonstrates the core process steps of the present invention.

[0031] Figure 2 The diagram shows a cross-sectional view, specifically illustrating: (a) molten paraffin wax impregnating the pores on the first side of the titanium felt; (b) the paraffin wax solidifying to form a masking layer; (c) the catalyst slurry being applied to the second side; and (d) after heat treatment, the paraffin wax masking layer being melted and removed. The titanium felt fibers, the paraffin wax masking layer, the catalyst slurry, and the final catalyst layer are clearly labeled in the diagram.

[0032] Figure 3 Two cross-sectional views are compared: (a) the integrated electrode prepared by the conventional blade coating method, showing that the catalyst slurry penetrates the entire substrate (internal pores and both sides); (b) the integrated electrode prepared by the method of the present invention, showing that the catalyst layer exists precisely only on the second side of the substrate, while the first side and internal pores are clean and free of catalyst blockage. This figure intuitively demonstrates the core advantage of the present invention in improving catalyst utilization.

[0033] Figure 4 The component structure is shown, comprising, in sequence: an end plate, a current collector, a porous transport layer, a single-sided catalytic layer electrode prepared according to the present invention, a proton exchange membrane, a catalytic layer electrode on the other side, a porous transport layer, a current collector, and an end plate. The figure highlights that the catalytic layer of the electrode of the present invention exists only on the side that contacts the proton exchange membrane.

[0034] Example 1 Anode fabrication based on paraffin masking and titanium felt substrate: (1) Take a piece of titanium felt with a porosity of 65% and a thickness of 0.6 mm, and clean and dry it according to the above pretreatment standards; (2) Application of paraffin masking layer: Heat refined paraffin to 85°C until it is completely melted. Place the pretreated titanium felt with one side down on the surface of the molten paraffin for 10 seconds, and use capillary action to allow the paraffin to fully wet the surface and near-surface pores of that side. Quickly lift the titanium felt and scrape off the excess wax from the first side surface with a scraper. Then place it on a cooling plate to allow the paraffin to solidify rapidly and form a sealing layer. (3) Catalyst loading and shaping: On the unmasked side of the titanium felt, IrO2 catalyst slurry (solid content 15wt%) was applied using a scraper, and then dried at 80°C for 30 minutes. Then, the temperature was increased to 350°C in air at 3°C / min and kept at that temperature for 1 hour to fully sinter and shape the catalyst layer. (4) Masking layer removal: After heat treatment, most of the paraffin layer has melted and flowed out. Place the electrode on a hot table at 90°C again for 5 minutes and gently wipe away any remaining wax with a lint-free cloth. To completely remove any trace residue in the pores, immerse the electrode in n-hexane at 60°C and ultrasonically clean it for 10 minutes. Finally, rinse it with fresh n-hexane and dry it at 80°C. (5) Effect Verification: Inductively Coupled Plasma Spectroscopy (ICP) analysis showed that the electrode prepared by the method of this invention achieved a catalyst utilization rate (mass of Ir participating in the reaction / total mass of Ir loaded) of 92%, while the utilization rate of the control sample using the traditional direct coating method was only 48%. At 2.0 A / cm 2 Electrolysis tests were conducted at current density, and the electrode cell voltage of the present invention remained stable at 1.78 V without significant fluctuations, indicating smooth mass transfer.

[0035] Example 2 Cathode fabrication based on PVA water-soluble masking and carbon paper substrate: (1) Take a piece of carbon paper (Toray 090) with a porosity of 78% and a thickness of 0.19 mm, and clean and dry it according to the standard pretreatment process; (2) Application of PVA masking layer: Prepare a 10wt% PVA aqueous solution and stir at 80°C until completely dissolved. Use a doctor blade to coat the entire surface of one side of the carbon paper with the PVA solution, with a wet film thickness of 150μm. Then place it at 60°C to dry for 2 hours to form a complete, dense and water-soluble PVA film; (3) Catalyst loading and shaping: On the unmasked side of the carbon paper, Pt / C catalyst slurry (10wt% solid content) was loaded using an air spraying method, with a loading of 0.5 mg Pt / cm. 2 After spraying, the electrode was dried at 70℃ for 20 minutes, and then heated to 300℃ at 2℃ / min under nitrogen protection and held at that temperature for 1 hour to complete the catalytic layer shaping. (4) Masking layer removal: Immerse the heat-treated electrode in deionized water at 40°C and ultrasonically vibrate (40kHz) for 15 minutes. The PVA film will visibly swell rapidly and completely dissolve and detach. Remove the electrode and rinse the surface with fresh deionized water to ensure that there is no PVA residue. Finally, dry it at 80°C. (5) Effect verification: Cross-sectional SEM observation showed that the catalyst layer only existed on the working side of the carbon paper, with a uniform thickness (about 15 μm) and was tightly bonded to the carbon paper fibers. The other side and the internal pores were clear and there was no catalyst blockage.

[0036] Therefore, it can be seen that in the technical solution of this invention: (1) Breakthrough progress in catalyst utilization and cost control: Through the spatial selective barrier effect of the temporary shielding layer, the present invention effectively eliminates the ineffective penetration of precious metal catalysts (such as Ir and Pt) into the porous substrate and non-working surface, increasing the catalyst utilization rate from <50% in the traditional method to more than 90%, directly reducing the electrode manufacturing cost by 30%-40%, and providing a key technical path to solve the pain point of high cost of PEM electrolyzers; (2) Significantly optimized overall electrode performance: The single-sided catalytic layer electrode prepared in this invention maintains high catalytic activity while perfectly inheriting the inherent three-dimensional interconnected pore structure of the porous substrate. This avoids gas-liquid transport resistance caused by catalyst blockage of the pores, achieving high current density (>2 A / cm²). 2 Under normal operating conditions, concentration polarization is significantly reduced, and voltage fluctuation rate is reduced by more than 60%, demonstrating superior operational stability and energy efficiency. (3) Process compatibility and broad industrialization prospects: The paraffin, hot melt adhesive, PVA and other masking materials are inexpensive and easy to obtain. Their application and removal processes are simple and they are seamlessly compatible with existing mature electrode preparation production lines such as scraping and spraying. They do not require complex and expensive vacuum or patterning equipment and have great potential for large-scale industrial application. (4) Inclusivity of process parameters: Any preparation method that uses the masking material type (paraffin wax, hot melt adhesive, water-soluble polymer, etc.) described in the claims to achieve coverage and pore sealing of one side of the porous substrate by any of the methods of impregnation, scraping, spraying, or hot pressing, and falls within the range of heat treatment and removal process parameters described in this invention, shall be within the equivalent protection scope of this invention. (5) Claims Coverage Statement: Any equivalent substitution or adjustment of the specific type of masking material, the type of porous substrate (titanium-based, carbon-based, etc.), the catalyst slurry system or process parameters by a person skilled in the art without departing from the core idea of ​​the present invention (i.e., using a completely removable temporary masking layer to achieve single-sided spatial selective loading of the catalyst on a porous conductive substrate) shall be deemed to fall within the protection scope of the claims of this patent.

[0037] In summary, this invention specifically discloses an integrated electrode, its preparation method, a membrane electrode, and an electrolyzer. Addressing the industry pain point that catalyst slurry easily penetrates into the porous transport layer and non-working surface during loading, leading to significant waste of precious metal catalysts and decreased electrode mass transfer performance, this invention proposes a single-sided precision loading technology based on a removable masking layer. This invention selects paraffin wax, hot melt adhesive, or a water-soluble polymer as the masking material, applying it in a molten or solution form to one side of a porous conductive substrate and controlling the wetting process to ensure it fully fills the pores on that side. After the masking layer solidifies to form a complete barrier, catalyst slurry is applied to the exposed surface on the other side of the substrate by scraping, spraying, or spin coating. After drying and heat treatment to set the catalyst layer, the masking material is removed by heating and melting, solvent dissolution, or physical exfoliation, ultimately obtaining a functional electrode with a uniform catalyst layer only on one side of the porous conductive substrate.

[0038] The core innovation of this invention lies in achieving spatially selective catalyst loading on a porous substrate by introducing a completely removable temporary masking layer. This method effectively blocks catalyst penetration into non-working regions, significantly improving the utilization rate and loading accuracy of precious metal catalysts while reducing manufacturing costs. Simultaneously, it maintains the original pore structure and mass transfer function of the porous substrate, avoiding gas-liquid transport resistance caused by catalyst blockage. This process is highly compatible and applicable to various porous conductive substrates such as titanium felt and carbon paper. It can be applied not only to the preparation of proton exchange membrane electrolysis electrodes for hydrogen production but also extended to the manufacture of anion exchange membrane electrolyzers, fuel cells, and other gas diffusion electrodes, providing a key electrode engineering solution for the development of high-performance electrochemical devices.

[0039] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a single-sided catalytic layer based on a removable masking layer, characterized in that, The preparation method comprises the following steps: (1) providing a porous conductive substrate, which comprises a first side and a second side opposite to the first side; (2) covering the first side of the substrate with a removable masking material in a molten state or a solution state, so that the removable masking material penetrates into the pores of the first side but does not protrude onto the pores of the second side, and forms a masking layer after solidification; (3) applying a catalyst slurry on the second side to form a catalyst layer precursor; (4) performing heat treatment on the catalyst layer precursor to shape it; (5) removing the masking layer to obtain an integrated electrode with a catalyst layer loaded on the second side only.

2. The production method according to claim 1, characterized by, The removable masking material is selected from one of paraffin, hot-melt adhesive or water-soluble polymer; and the porous conductive substrate is titanium felt, titanium fiber sintered plate or carbon paper.

3. The preparation method according to claim 1, wherein: in step (2), the removable masking material is applied by means of blade coating, roller coating, dipping or spraying; in step (3), the catalyst slurry is applied by means of blade coating, spraying or screen printing.

4. The preparation method according to claim 2, characterized in that, in step (2): when the removable masking material is paraffin, the first side is heated to a molten state and the paraffin is allowed to penetrate into the pores of the first side; 5. The preparation method according to claim 2, characterized in that, when the removable masking material is hot-melt adhesive, the first side is sprayed or hot-pressed with the molten hot-melt adhesive and the hot-melt adhesive is allowed to penetrate into the pores of the first side; 6. The preparation method according to claim 2, characterized in that, when the removable masking material is water-soluble polymer, the first side is coated or sprayed with a water solution of the water-soluble polymer and the water-soluble polymer is allowed to penetrate into the pores of the first side.

7. The production method according to claim 6, wherein The water-soluble polymer is polyvinyl alcohol (PVA), agarose or gelatin, and the concentration of the water solution is 5-15 wt%.

8. The method of claim 1, wherein, In step (4), the heat treatment is performed in air or inert atmosphere, the temperature is raised to 250-450℃ at a rate of 1-5℃ / min, and the temperature is kept for 0.5-2 hours.

9. The preparation method according to claim 2, characterized in that, In step (5): when the removable masking material is paraffin or hot-melt adhesive, the integrated electrode is heated to a temperature 20-50℃ higher than the melting point of the masking material to melt the masking material and remove the residue; when the removable masking material is water-soluble polymer, the integrated electrode is immersed in water or ultrasonic water bath to dissolve and peel off the water-soluble polymer.

10. An integrated electrode prepared by the method of any one of claims 1 to 9, characterized in that, The catalyst layer of the integrated electrode is precisely loaded on the second side of the porous conductive substrate, and the first side and the internal pores of the porous conductive substrate remain clean and porous.

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