Electrolytic cell porous transmission layer prepared on basis of decomposition type porous substrate and preparation method of electrolytic cell porous transmission layer

Abstract

The invention discloses an electrolytic cell porous transmission layer prepared based on a decomposition type porous substrate and a preparation method of the electrolytic cell porous transmission layer, and relates to the technical field of electrode manufacturing. Or the metal powder is used as a filler in the substrate, and meanwhile, a laminated structure is constructed on the outer surface of the substrate to prepare a transmission layer green body; in an inert atmosphere or reducing atmosphere environment, carrying out heat treatment on the transmission layer green body at a first temperature to prepare a transmission layer green body with a channel extending directionally along the direction of a porous material framework; and further sintering the transmission layer green body subjected to heat treatment at the first temperature at a second temperature higher than the first temperature to form the micropore channel between the metal powder. In the thermal decomposition process, the substrate fibers and the metal powder are sintered to form two-scale pores, a double-scale pore structure is achieved, and the problems that in the prior art, the mechanical strength is poor, the aperture gradient in the thickness direction is uncontrollable, the mass transfer resistance is high, and roll-to-roll continuous production is difficult are solved.

Description

Technical Field

[0001] This invention relates to the field of electrode manufacturing technology, and in particular to a porous transport layer for an electrolytic cell based on a decomposition-type porous substrate and its preparation method. Background Technology

[0002] Porous transport layers (PTLs) play a crucial role in electrolyzers, primarily functioning to provide electronic pathways to the catalyst layer, maintain mechanical contact between the catalyst layer and the catalyst layer, and provide channels for gas and liquid transport. Titanium-based PTLs are commonly used in proton exchange membrane (PEM) electrolyzers, while nickel-based PTLs are frequently employed in anion exchange membrane (AEM) electrolyzers. However, existing PTL preparation methods have several shortcomings, making it difficult to meet the demands of high-performance electrolyzers.

[0003] Existing technologies for PTL fabrication mainly include powder metallurgy pore formation, spacer methods, metal foaming, mechanical drilling, spraying, and metal fiber mats. While these methods have achieved PTL fabrication to some extent, they have significant drawbacks in terms of thinness, pore structure control, mechanical strength, continuous production, and cost control. 1) The contradiction between mechanical strength and thinness: The thin PTL (<250μm) prepared by traditional methods has insufficient mechanical strength and cannot withstand the mechanical stress in the continuous industrial production process; 2) Randomness of pore structure: The pore structure formed by existing methods is mostly randomly distributed, with high gas transport tortuosity (torsuosity > 3), resulting in large mass transfer resistance; 3) Low thickness control accuracy: The thickness control accuracy of traditional methods is usually ±20 to ±50 μm, which cannot meet the requirements of precision applications; 4) Difficulty in pore size gradient design: Existing technologies make it difficult to achieve a controllable pore size gradient distribution in the thickness direction, and cannot simultaneously optimize catalyst layer contact and gas emission; 5) Poor adaptability to continuous production: Most methods require complex molds or multi-step processes, which are not suitable for roll-to-roll continuous production; 6) High sintering temperature and high energy consumption: The sintering temperature of traditional Ti powder is usually >1000°C, which results in high energy consumption and is prone to residual carbon clogging the pores. 7) Narrow process window: Existing methods have a narrow process parameter window, resulting in large batch-to-batch product performance differences (typically >15%). 8) High cost: The complex preparation process and high-temperature treatment result in high production costs, which limits large-scale application.

[0004] Existing technologies do not have a porous transport layer that can simultaneously satisfy the requirements of roll-to-roll continuous manufacturing, good mechanical strength, controllable thickness-direction pore size gradient, and low mass transfer resistance. Summary of the Invention

[0005] In view of the above analysis, and in view of the shortcomings of the prior art, the present invention aims to provide an electrolytic cell porous transport layer based on a decomposition-type porous substrate and its preparation method, so as to solve at least one of the problems in the prior art, such as poor mechanical strength, uncontrollable pore size gradient in the thickness direction, high mass transfer resistance, and difficulty in continuous roll-to-roll production.

[0006] The objective of this invention is mainly achieved through the following technical solutions: This invention discloses a method for preparing a porous transport layer for an electrolyzer based on a decomposition-type porous substrate, comprising: S1: A transport layer green body is prepared by using a porous material capable of thermal decomposition as a substrate and metal powder as a filler, or by using metal powder as an internal filler of the substrate while constructing a layered structure on the outer surface of the substrate. S2: In an inert or reducing atmosphere, the transport layer green blank is heat-treated at a first temperature to prepare a transport layer green blank with channels extending oriented along the porous material skeleton direction. S3: The transport layer green body after heat treatment at the first temperature is further sintered at a second temperature higher than the first temperature to form microporous channels between metal powders.

[0007] Preferably, step S1 involves preparing the transport layer green blank by slurry coating or powder rolling.

[0008] Preferably, the metal powder in step S1 can be titanium powder or nickel powder.

[0009] Preferably, the titanium powder has a particle size of 1μm to 50μm; the nickel powder has a particle size of 0.5μm to 30μm.

[0010] Preferably, the porous material capable of thermal decomposition in step S1 can be one or more of polylactic acid (PLA), polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), and polypropylene (PP).

[0011] Preferably, the porosity of the porous material is 30% to 85%.

[0012] Preferably, the first temperature range is 200℃~400℃.

[0013] Preferably, when the metal powder is titanium powder, the sintering temperature is 800°C to 1200°C.

[0014] Preferably, when the metal powder is nickel powder, the sintering temperature is 600°C to 1000°C.

[0015] A porous transport layer for an electrolyzer based on a decomposition-type porous substrate is prepared by the aforementioned method for preparing a porous transport layer for an electrolyzer based on a decomposition-type porous substrate. The porous transport layer has a thickness of 180 μm to 250 μm; porosity of 40% to 82%; directional channel diameter of 30 μm to 50 μm; interparticle micropore diameter of 5 μm to 12 μm; tortuosity of 1.6 to 1.8; contact resistance of 2.5 mΩ·cm² to 3.0 mΩ·cm²; compressive strength ≥ 2.6 MPa; and electrical conductivity ≥ 1.3 × 10⁻⁶. 4 S / cm.

[0016] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: (1) This invention uses a decomposable porous substrate (such as PLA, PMMA, etc.) as a template to form directional channels extending along the fiber direction during thermal decomposition. It is filled and sintered with metal powder (such as titanium powder, nickel powder) to form a stable metal matrix structure. A staged heat treatment process is used to first decompose the substrate material at a lower temperature and then sinter the metal powder at a higher temperature to ensure that the metal particles are tightly bonded and form a high-strength porous transport layer. For the powder laying and rolling method, a high-pressure rolling process is used to ensure that the metal powder fully fills the substrate pores and is tightly bonded to the substrate, thereby improving the overall mechanical strength. The compressive strength of the titanium-based PTL reaches 2.6 MPa, which is significantly higher than that of traditional titanium felt, thus solving the problem of poor mechanical strength.

[0017] (2) This invention achieves a pore size gradient design in the thickness direction by selecting metal powders of different particle sizes (such as titanium powder with a particle size of 1-50 μm and nickel powder with a particle size of 0.5-30 μm) for layered coating or powder spreading. During the thermal decomposition process, the diameter of the substrate fiber (such as 35-50 μm) is used to form the main channel, while secondary micropores (5-10 μm) are formed by sintering the metal powder, thus realizing a dual-scale pore structure: main channel (30-50 μm oriented pores) and secondary pores (5-10 μm micropores). This structure not only reduces the tortuosity of gas transport, but also provides good lateral connectivity and surface contact through the microporous network, further optimizing the gas transport path and solving the problem of uncontrollable pore size gradient in the thickness direction.

[0018] (3) In this invention, a dual-scale pore structure is achieved by using substrate fibers and metal powder to form a main channel during thermal decomposition. The diameter of the substrate fibers (e.g., 35–50 μm) forms the main channel, while the secondary micropores (5–10 μm) are formed by sintering the metal powder. This structure reduces the tortuosity of gas transport and provides good lateral connectivity and surface contact through the microporous network, further optimizing the gas transport path.

[0019] (4) By selecting metal powders of different particle sizes for layer coating or spreading, the present invention prepares a double-layer composite structure with different pore structures in the thickness direction, realizes the pore size gradient design in the thickness direction, and solves the problem of uncontrollable pore size gradient in the thickness direction.

[0020] (5) In the process of thermal decomposition of the decomposable substrate, the present invention forms a low-torsion directional channel extending along the fiber direction, reducing the tortuosity of the gas transport path; through a step-by-step heat treatment process, a dual-scale pore structure (main channel and secondary pores) is formed, optimizing the gas transport path and reducing the mass transfer resistance. The gas transport resistance is significantly reduced by 30% to 50% compared with the traditional PTL, the tortuosity is reduced from 3.2 to 1.8, and the air permeability is increased by 65% ​​compared with the traditional foam nickel, thus solving the problem of high mass transfer resistance.

[0021] (6) The present invention adopts a roll-to-roll powder spreading rolling process. The base roll passes through the powder spreading unit at a certain speed, and powder is spread on both sides at the same time, realizing continuous production. By optimizing the rolling parameters (such as rolling pressure, temperature and speed) and heat treatment process, the consistency of product quality during continuous production is ensured. The roll-to-roll continuous production efficiency reaches 25m² / h, and the resistance difference between batches is less than 3%, which significantly improves production efficiency and product consistency. By optimizing the process parameters, the sintering temperature is reduced, and energy consumption is reduced by 15% to 25%, which further improves the feasibility of industrial application and solves the problem of difficult roll-to-roll continuous production. Attached Figure Description

[0022] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0023] Figure 1 This is a schematic diagram of the microstructure of PTL after sintering in Embodiment 1 of the present invention.

[0024] Figure 2 This is a schematic diagram of the microstructure of PTL after sintering in Example 3 of the present invention.

[0025] Figure 3 This is a cross-sectional electron microscope image of a traditional sintered PTL structure. Detailed Implementation

[0026] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0027] On one hand, this invention discloses a method for preparing a porous transport layer for an electrolyzer based on a decomposition-type porous substrate, comprising: S1: A transport layer green body is prepared by using a porous material capable of thermal decomposition as a substrate and metal powder as a filler, or by using metal powder as an internal filler of the substrate while constructing a layered structure on the outer surface of the substrate. S2: In an inert or reducing atmosphere, the transport layer green blank is heat-treated at a first temperature to prepare a transport layer green blank with channels extending oriented along the porous material skeleton direction. S3: The transport layer green body after heat treatment at the first temperature is further sintered at a second temperature higher than the first temperature to form microporous channels between metal powders.

[0028] Compared with existing technologies, this invention uses a decomposable porous substrate (such as PLA, PMMA, etc.) as a template to form directional channels extending along the fiber direction during thermal decomposition. These channels are then filled and sintered with metal powders (such as titanium powder and nickel powder) to form a stable metal matrix structure. A staged heat treatment process is used, first decomposing the substrate material at a lower temperature and then sintering the metal powder at a higher temperature to ensure that the metal particles are tightly bonded, forming a high-strength porous transport layer. For the powder laying and rolling method, a high-pressure rolling process is used to ensure that the metal powder fully fills the substrate pores and is tightly bonded to the substrate, improving the overall mechanical strength. The compressive strength of the titanium-based PTL reaches 2.6 MPa, which is significantly higher than that of traditional titanium felt, solving the problem of poor mechanical strength.

[0029] Specifically, step S1 involves preparing the transport layer green blank by slurry coating or powder rolling.

[0030] Specifically, the slurry coating method includes: S101, Slurry preparation: The metal powder is mixed with a binder and a solvent (such as ethanol, isopropanol, etc.); Add an appropriate amount of dispersant (such as polyethylene glycol PEG-400) to improve the uniformity of the slurry; Use a mixing device (such as a planetary ball mill) to mix evenly and prepare a slurry with a solid content of about 20wt% to 40wt%.

[0031] Specifically, the mass ratio of metal powder, binder, and dispersant in the solid component is as follows: metal powder: 70%–90%; binder: 5%–15%; dispersant: 0.2%–2%; solvent: adjusted to 60%–80% of the total mass of the slurry to ensure that the solid content is between 20wt% and 40wt%.

[0032] It should be noted that the above-mentioned solid raw material component ratio and solid-liquid ratio ensure that the solid content in the slurry is between 20 and 40 wt%. A slurry with a solid content of 20-40 wt% has a suitable viscosity, neither too thin (leading to an excessively thin or uneven coating) nor too thick (making coating or molding difficult). This viscosity range is suitable for various coating processes, such as blade coating, spin coating, and spray coating, ensuring the uniformity and thickness consistency of the coating. Simultaneously, the suitable solid content ensures good flowability of the slurry during coating, allowing for better coverage of the substrate surface and filling of minor depressions and irregular shapes, thereby improving the quality and uniformity of the coating. Furthermore, within this solid content range, metal powder, binder, and dispersant can be better dispersed in the solvent, forming a uniform slurry. The dispersant (such as PEG-400) further improves the uniformity of the slurry, prevents metal powder particle aggregation, and ensures the uniform distribution of each component in the slurry.

[0033] Specifically, the binder can be polyvinyl butyral (PVB) or nitrocellulose; the dispersant can be polyethylene glycol (PEG-400); and the solvent can be ethanol or isopropanol.

[0034] S102, Coating Operation: The decomposed porous substrate is laid flat on the coating stage; Apply the slurry evenly to one or both sides of the substrate using a scraper or spraying method; The coating thickness is controlled, typically ranging from 50 μm to 200 μm.

[0035] It should be noted that a thickness range of 50μm to 200μm ensures that the coating or material has sufficient mechanical strength, without becoming brittle due to excessive thickness or lacking sufficient support due to excessive thinness. For example, in porous transport layers, an appropriate thickness ensures the structural stability of the material during use; a coating that is too thin (<50μm) may be prone to cracking or inhomogeneity during drying or sintering, while a coating that is too thick (200μm) may generate internal stress during shrinkage, leading to structural defects. An appropriate thickness allows for better control of porosity and pore size distribution. For instance, a thickness range of 50μm to 200μm allows for precise process control to achieve ideal porosity (e.g., 60%–80%), thereby optimizing gas and liquid transport performance; within this thickness range, a more uniform pore size distribution can be achieved by adjusting process parameters (such as slurry concentration, coating speed, etc.), ensuring consistent material performance.

[0036] S103, Deep Penetration Treatment: Immediately after coating, place the green body in a vacuum chamber and evacuate to -0.09 to -0.10 MPa, maintaining the vacuum for 10 to 15 minutes to allow the slurry to completely penetrate the substrate under negative pressure. Apply mechanical pressure (approximately 0.4 MPa ± 0.1 MPa) using a scraper to further promote slurry penetration and ensure no air bubbles remain.

[0037] S104. Drying treatment: Dry in a ventilated oven at 60℃~80℃ for 1 to 2 hours to remove the solvent and form a green body with a certain strength.

[0038] Compared with existing technologies, this invention utilizes a substrate fiber and metal powder to form a main channel during thermal decomposition. The diameter of the substrate fiber (e.g., 35–50 μm) forms the main channel, while the metal powder is sintered to form secondary micropores (5–10 μm), achieving a dual-scale pore structure: a main channel (30–50 μm oriented pores) and secondary pores (5–10 μm micropores). This structure reduces the tortuosity of gas transport and provides good lateral connectivity and surface contact through the microporous network, further optimizing the gas transport path.

[0039] Compared with the prior art, the present invention prepares a double-layer composite structure with different pore structures in the thickness direction by selecting metal powders of different particle sizes for layer coating or powder spreading, thereby realizing the pore size gradient design in the thickness direction and solving the problem of uncontrollable pore size gradient in the thickness direction.

[0040] Preferably, the slurry coating method can be used to obtain a transport layer with different coating layers at different locations in the thickness direction through multiple coatings, including: 1) Fix the porous material substrate on the coating stage; 2) Coat one side of the substrate with a first slurry containing a first metal powder; 3) The coated substrate is subjected to deep penetration treatment and drying to obtain a green body; 4) Coat the green body with a second slurry containing a second metal powder on one side or the other side near the substrate; 5) The substrate after secondary coating is subjected to deep penetration treatment and drying to obtain a green body with different coating layers in the thickness direction. After subsequent heat treatment, a transport layer with different coating layers at different positions in the thickness direction is obtained.

[0041] Preferably, the first metal powder and the second metal powder have different particle sizes and materials, which can obtain a transport layer with a pore diameter gradient and / or conductivity gradient in the thickness direction.

[0042] Specifically, the powder-coating rolling method includes: S111, Powder Laying: The decomposable porous substrate was placed on a stainless steel polytetrafluoroethylene carrier plate. Evenly spread metal powder on one or both sides of the substrate, controlling the amount of powder spread (e.g., 180g / m² to 220g / m² per side).

[0043] S112, Rolling operation: Rolling is performed using a twin-roll mill, with the rolling temperature (e.g., 50°C to 80°C) and pressure (6 MPa to 10 MPa) controlled. Multi-pass rolling (2-3 passes) is used to ensure that the metal powder fully fills the pores of the substrate and bonds tightly to the substrate. Inspect the rolled green billet to ensure that the porous material is completely coated with metal powder, with a powder penetration rate >95%.

[0044] Preferably, a binder can be added during roll-to-roll powder rolling to promote forming.

[0045] Specifically, the binder can be PVB, polyvinylpyrrolidone (molecular weight 40,000-80,000), nitrocellulose, etc.

[0046] Preferably, the powder spreading and rolling method can be implemented using a continuous production process: Roll-to-roll powder spreading and rolling: The base roll material passes through the powder spreading unit at a speed of 0.8m / min to 1.5m / min, with powder spread on both sides simultaneously, at 200g / m² ± 50g / m² on each side.

[0047] Compared with existing technologies, this invention adopts a roll-to-roll powder-laying rolling process, in which the base roll passes through the powder-laying unit at a certain speed, with powder laid on both sides simultaneously, achieving continuous production. By optimizing rolling parameters (such as rolling pressure, temperature, and speed) and heat treatment processes, the consistency of product quality during continuous production is ensured. The roll-to-roll continuous production efficiency reaches 25 m² / h, and the batch-to-batch resistance difference is less than 3%, significantly improving production efficiency and product consistency. By optimizing process parameters, the sintering temperature is reduced, reducing energy consumption by 15% to 25%, further enhancing the feasibility of industrial application and solving the problem of difficulty in roll-to-roll continuous production.

[0048] Specifically, multi-pass rolling can involve one pre-rolling and multiple main rolling processes, including: Pre-rolling: First, apply a light pressure of 3MPa±0.5MPa to allow the powder to initially adhere to the substrate; Main rolling: Online warm rolling temperature 60°C±10°C, main rolling pressure increased to 10MPa±2MPa (high pressure ensures full penetration of powder).

[0049] During implementation, pre-rolling at a relatively low pressure (3MPa ± 0.5MPa) allows the powder to initially adhere to the substrate, forming a relatively uniform preliminary structure. This step helps eliminate large gaps between powder particles, creating favorable conditions for subsequent main rolling. Furthermore, the main rolling pressure is increased to 10MPa ± 2MPa at an online warm rolling temperature of 60°C ± 5°C. This high pressure ensures that the powder fully penetrates the substrate, further compacting the material and significantly improving its density. Higher density generally results in better mechanical properties of the material (such as strength and hardness).

[0050] Meanwhile, the staged compaction method of pre-rolling and main rolling can gradually enhance the bonding force between the powder and the substrate. Pre-rolling allows the powder to initially adhere, while main rolling further strengthens this bonding through high pressure, reducing interface defects and porosity; the online warm rolling temperature (60°C±5°C) helps reduce friction between powder particles, making the particles easier to move and rearrange, thereby better embedding them into the substrate and further enhancing the bonding strength.

[0051] Preferably, a roller surface with microporous texture is used to enhance the propulsion of powder into the pores of the substrate.

[0052] Specifically, the metal powder in step S1 can be titanium powder or nickel powder.

[0053] Specifically, the titanium powder has a particle size of 1μm to 50μm.

[0054] Specifically, the nickel powder has a particle size of 0.5 μm to 30 μm.

[0055] Purity requirement: Ensure the purity of the metal powder is ≥99.5%.

[0056] It should be noted that within the titanium powder particle size range of 1–50 μm, the powder possesses an appropriate specific surface area (0.5 m² / g–2 m² / g), ensuring both good sintering performance and the formation of secondary micropores of 5–10 μm after sintering. When the particle size is <1 μm, the powder surface energy is too high, making it prone to oxidation and over-densification during sintering, reducing porosity. When the particle size is >50 μm, the powder specific surface area is small, resulting in reduced sintering activity and requiring higher temperatures and times for complete sintering.

[0057] The nickel powder particle size in the range of 0.5μm to 30μm matches the porosity requirements of the AEM electrolytic cell. Nickel has higher sintering activity than titanium, so finer particle sizes can be used. Nickel powder with a particle size in the range of 0.5μm to 30μm can achieve full sintering at lower temperatures (600 to 1000℃), while fine powder can provide higher electrical conductivity and better catalyst layer contact.

[0058] Specifically, the porous material that can be thermally decomposed in step S1 can be one or more of polylactic acid (PLA), polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), and polypropylene (PP).

[0059] Specifically, the thickness of the porous material ranges from 30 μm to 500 μm, and can be 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, 230 μm, 240 μm, 25 μm, etc. 0μm, 260μm, 270μm, 280μm, 290μm, 300μm, 310μm, 320μm, 330μm, 340μm, 350μm, 360μm, 370μm, 3 80μm, 390μm, 400μm, 410μm, 420μm, 430μm, 440μm, 450μm, 460μm, 470μm, 480μm, 490μm or 500μm.

[0060] Specifically, the fiber diameter of the porous material is 10μm to 100μm, and can be 10μm, 20μm, 30μm, 40μm, 50μm, 60μm, 70μm, 80μm, 90μm or 100μm, preferably 35μm to 50μm.

[0061] Specifically, porous materials can be nonwoven fabrics, woven meshes, or hybrid structures.

[0062] Specifically, the porosity of the porous material is 30% to 85%, and can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or 85%.

[0063] It should be noted that when the thickness of the porous material is <30μm, the mechanical strength of the porous material is insufficient, and it is easily damaged during coating or rolling. When the thickness of the porous material is >500μm, the decomposition products of the substrate are difficult to completely drain, and may remain and block the pores. A porous material thickness in the range of 30μm to 500μm can ensure that the final PTL thickness is 150μm to 450μm, thereby meeting the mass transfer and mechanical strength requirements of the electrolyzer.

[0064] It should be noted that the fiber diameter of the porous material can determine the pore size of the directional channels in the transport layer. A fiber diameter of 35μm to 50μm can form a directional main channel of 30μm to 50μm, which is within the optimal pore size range for gas transport. Too fine fibers (<10μm) form channels that are too small, increasing flow resistance. Too coarse fibers (>100μm) reduce the number of channels per unit area and reduce the effective transport area.

[0065] It should be noted that when the porosity of the porous material is <30%, the substrate is too dense, making it difficult for metal powder to penetrate, resulting in a decrease in the porosity of the PTL; when the porosity of the porous material is >85%, the substrate has poor mechanical strength and is prone to deformation or breakage during processing. For titanium-based PTLs, a porosity of 50%–70% in the porous material can yield a PTL with a final porosity of 60%–70%; for nickel-based PTLs, a porosity of 60%–85% in the porous material can yield a PTL with a final porosity of 70%–85%.

[0066] It should be noted that nonwoven fibers are randomly distributed to form a multidirectional channel network, which is suitable for applications that require isotropic transport; woven fibers are regularly arranged to form an ordered channel, which has higher mass transfer efficiency but obvious anisotropy; while the hybrid structure combines the advantages of both, balancing mass transfer efficiency and uniformity.

[0067] Specifically, step S2 includes: S201. Select the heat treatment atmosphere: Select a suitable atmosphere based on the type of electrolytic cell and the properties of the metal powder: The titanium-based PTL uses an inert atmosphere: argon (Ar), with a flow rate controlled between 100 ml / min and 500 ml / min to ensure a uniform atmosphere inside the furnace. Nickel-based PTLs use a selective reducing atmosphere: a mixture of hydrogen and argon (H2 / Ar), with the H2 ratio typically between 5% and 10%, and the flow rate controlled between 100 ml / min and 500 ml / min.

[0068] S202. Set heat treatment parameters: Based on the selected thermally decomposable porous material, the first temperature range is set to 200℃~400℃, so that the thermally decomposable porous material in the first temperature range can be fully thermally decomposed.

[0069] For example, when the thermally decomposable porous material is PLA or PMMA, the first temperature range is further optimized based on the difference in decomposition temperature of the thermally decomposable porous materials. The decomposition temperature of PLA is usually between 250℃ and 300℃, while the decomposition temperature of PMMA substrate is between 280℃ and 350℃.

[0070] S203, thermal insulation treatment: When the temperature reaches the set first temperature, the heat preservation process begins; The heat preservation time is 2 to 5 hours to ensure that the base material is fully decomposed and dissipated. During the insulation process, the substrate material gradually decomposes, forming channels that extend directionally along the porous material skeleton.

[0071] It should be noted that during the first stage of heat treatment, the porous network material begins to decompose, and the porous network material pyrolyzes to form carbide intermediates; the decomposition products are retained in situ in the form of coke and carbide precursors; a carbide film is formed on the substrate surface to prevent volatilization loss; as the temperature continues to rise, the organic main chain is completely broken, but the decomposition products are chemically fixed, thereby forming stable carbonaceous intermediates and oxygen / nitrogen-containing intermediates; the oxide layer on the surface of the metal powder begins to be reduced, exposing active metal atoms.

[0072] Compared with existing technologies, this invention forms low-torsion directional channels extending along the fiber direction during the thermal decomposition of the decomposition substrate, reducing the tortuosity of the gas transport path; through a step-by-step heat treatment process, a dual-scale pore structure (main channel and secondary pores) is formed, optimizing the gas transport path and reducing mass transfer resistance. The gas transport resistance is significantly reduced by 30% to 50% compared with traditional PTL, the tortuosity is reduced from 3.2 to 1.8, and the air permeability is improved by 65% ​​compared with traditional foamed nickel, thus solving the problem of high mass transfer resistance.

[0073] Preferably, step S3 includes: S301. Based on the sintering characteristics of metal powder, a second temperature range is set: For titanium powder, the sintering temperature is usually 800°C to 1200°C; For nickel powder, the sintering temperature is usually 600°C to 1000°C.

[0074] S302. Set the heating rate to 2°C / min~5°C / min, and slowly increase the temperature from the first temperature to the second temperature range; S303, heat preservation sintering treatment: When the temperature reaches the set second temperature, the heat preservation sintering process begins; The heat preservation time is 1 to 3 hours to ensure that the metal powder is fully sintered and forms microporous channels between particles; During the heat preservation process, the metal powder particles gradually combine to form a stable microporous network structure.

[0075] S304, cool to room temperature: After the heat preservation is completed, turn off the heating equipment and allow it to cool naturally to room temperature; During the cooling process, an inert or reducing atmosphere is continuously introduced to prevent the metal powder from oxidizing.

[0076] On the other hand, this invention also discloses a porous transport layer for an electrolyzer prepared based on a decomposition-type porous substrate. Prepared by the above method, the porous transport layer has a thickness of 180 μm to 250 μm; porosity of 40% to 82%; directional channel diameter of 30 μm to 50 μm; interparticle micropore diameter of 5 μm to 12 μm; tortuosity of 1.6 to 1.8; contact resistance of 2.5 mΩ·cm² to 3.0 mΩ·cm²; compressive strength ≥ 2.6 MPa; and electrical conductivity ≥ 1.3 × 10⁻⁶. 4 S / cm.

[0077] The following embodiments and comparative examples are provided to better illustrate the present invention: Example 1 This embodiment discloses a method for preparing a porous transport layer for an electrolyzer based on a decomposition-type porous substrate, including: S1. Preparation of a transport layer green body material using a thermally decomposable porous material as a substrate and metal powder as a filler, or using metal powder as an internal filler of the substrate while simultaneously constructing a layered structure on the outer surface of the substrate, including: 1) Raw material preparation: Decomposable porous substrate: PLA nonwoven fabric, thickness 150μm, fiber diameter 40μm, porosity 65%; Metal powder: Titanium powder, average particle size 5μm, purity 99.5%; Adhesive: Polyvinyl butyral (PVB), molecular weight 50,000 to 80,000; Solvent: Ethanol; Dispersant: Polyethylene glycol (PEG-400), 0.5wt.

[0078] 2) Slurry preparation: Add 10g of titanium powder, 1.2g of PVB binder, and 0.05g of dispersant PEG-400 to 25ml of anhydrous ethanol, and mix for 2 hours using a planetary ball mill to obtain a titanium slurry with a solid content of approximately 31wt%.

[0079] 3) Green body preparation: PLA substrate is laid flat on polytetrafluoroethylene vinyl plate; titanium paste is coated on one side of the substrate using a doctor blade coating method, with a wet film thickness of about 180μm. Deep penetration treatment; Immediately after coating, the preform is placed in a vacuum chamber and evacuated to ~0.09 MPa for 10 minutes. Under negative pressure, the titanium paste completely impregnates the 150 μm fiber network of the substrate; the surface of the PLA fibers and the pores between the fibers are completely filled with the titanium paste. Apply pressure of 0.4 MPa with a scraper and scrape back and forth 3 to 5 times to further promote the penetration of the slurry into the deep substrate and ensure that no air bubbles remain. When viewed from the back (uncoated side), the titanium paste should be visible to have penetrated to the back, exhibiting a metallic luster; the paste penetration depth is greater than 100% of the substrate thickness (i.e., completely penetrating a 150μm substrate). The titanium paste completely impregnates the PLA fibers, and the PLA fibers are completely covered by the titanium paste, resulting in a front coating thickness of about 60μm (dry film), and the interior of the substrate is completely filled with paste; a thin layer of paste seeps out on the back (about 10-15μm), which can be retained or scraped off. Dry in a ventilated oven at 60°C for 1.5 hours to remove ethanol solvent; The total thickness of the green body is approximately 220 μm, with the front metal layer being approximately 60 μm; the impregnated substrate layer being 150 μm (PLA fibers are completely coated with titanium powder); and the back thin metal layer being approximately 10 μm.

[0080] S2. In an inert or reducing atmosphere, the transport layer green blank is heat-treated at a first temperature to prepare a transport layer green blank having channels oriented along the porous material skeleton direction, including: 1) Place the green billet in a tube furnace, first evacuate to 50-100 Pa, then introduce high-purity argon gas to create a protective atmosphere inside the furnace; 2) Increase the temperature to 280°C at a rate of 1.5°C / min and hold for 4 hours to complete the decomposition of the PLA substrate; S3. The transport layer green blank, after heat treatment at the first temperature, is further sintered at a second temperature higher than the first temperature to form microporous channels between metal powders, including: 1) Under an argon protective atmosphere, the temperature was increased to 950°C at a rate of 3°C / min and held for 2 hours to complete the sintering of titanium powder; 2) Naturally cool to room temperature to obtain a porous transport layer.

[0081] Product performance testing: Final PTL thickness: 200 μm (±4 μm); Porosity: 68%; Directional channel structure: pore size 40μm (along the original PLA fiber direction), completely penetrating a thickness of 200μm, and uniformly distributed throughout the entire PTL thickness direction.

[0082] Micropore size between particles: 5-10 μm (formed by sintering titanium powder).

[0083] Tortuosity: 1.8 (3.2 for conventional titanium felt). The through-type directional channels provide a low-torsion main gas transport path, while the interparticle microporous network (5–10 μm) provides lateral connectivity and surface contact. The dual-scale pore structure works synergistically to achieve low mass transfer resistance.

[0084] Contact resistance: 3.0 mΩcm²; Breathability: 45% higher than that of conventional titanium felt represented by Comparative Example 1; Compressive strength: 2.6 MPa.

[0085] Test method description: Microstructure characterization: Scanning electron microscopy was used to observe the pore morphology and channel structure.

[0086] Pore ​​size distribution test: The pore size distribution curve was determined by mercury porosimetry.

[0087] Electrical performance testing: Contact resistance and volume resistance are measured using the four-point probe method.

[0088] Mechanical properties: The universal testing machine is used to test the compressive strength and flexural strength.

[0089] Electrochemical performance: Polarization curves and stability were tested in an actual electrolytic cell.

[0090] Example 2 This embodiment discloses a method for preparing a porous transport layer for an electrolyzer based on a decomposition-type porous substrate, including: S1. Preparation of a transport layer green body material using a thermally decomposable porous material as a substrate and metal powder as a filler, or using metal powder as an internal filler of the substrate while simultaneously constructing a layered structure on the outer surface of the substrate, including: 1) Raw material preparation: Decomposable porous substrate: PMMA woven mesh, 200μm thick, 60μm mesh size, 45μm fiber diameter; Metal powder: Nickel powder, average particle size 3μm, purity 99.8%; Rolling equipment: twin-roll mill, roll diameter 200mm.

[0091] 2) Green body preparation: Place the PMMA woven mesh on a stainless steel carrier plate; evenly spread nickel powder on both sides of the substrate, with an amount of powder of about 180g / m² on each side; Powder infiltration enhancement: 1) A twin-roll mill is used for warm rolling at a rolling temperature of 70°C. First, a light pre-rolling is performed with a pressure of 3MPa to allow the powder to initially adhere to the substrate. The main rolling pressure is increased to 8MPa (high pressure ensures that the powder is fully penetrated) and the rolling speed is 0.5m / min. 2) During the warm rolling process, the surface of PMMA fibers softens slightly, and the high pressure allows the nickel powder to be fully pressed into the mesh and fiber gaps. 3) Multi-pass rolling (1 pre-rolling and 2 main rolling) is adopted to ensure that the nickel powder completely fills the substrate network structure; 4) Post-rolling inspection: The pores of the woven mesh of the substrate should be completely filled with nickel powder, and the fiber surface should be completely covered with nickel powder; the thickness of the green after rolling is about 240μm, the nickel powder and the PMMA substrate form a strong mechanical bond, the green has good integrity, and the nickel powder penetration rate is >95%.

[0092] S2. In an inert or reducing atmosphere, the transport layer green blank is heat-treated at a first temperature to prepare a transport layer green blank having channels oriented along the porous material skeleton direction, including: 1) Place the green billet in a pusher furnace and introduce a mixture of 95% N2 and 5% H2; 2) The temperature was increased to 320°C at 1.5°C / min and held for 4 hours to complete the decomposition of the PMMA substrate. After the PMMA decomposition, a directional channel network with a diameter of about 45μm was formed.

[0093] S3. The transport layer green blank, after heat treatment at the first temperature, is further sintered at a second temperature higher than the first temperature to form microporous channels between metal powders, including: 1) Continue heating at 2°C / min to 800°C, hold for 1.5 hours to complete the nickel powder sintering; 2) Cool to room temperature in a protective atmosphere.

[0094] Product performance testing: Final PTL thickness: 180 μm (±5 μm); Porosity: 82%; Directional channel diameter: 45μm (along the direction of the woven mesh) Network channel structure, tortuosity: 1.6; Electrical conductivity: 1.3 × 10 4 S / cm; Contact resistance: 2.5 mΩ·cm²; Corrosion rate in 1 M KOH solution: <0.07 μm / year; Breathability: 65% higher than conventional nickel foam represented by Comparative Example 2.

[0095] Example 3 This embodiment discloses a method for preparing a porous transport layer for an electrolytic cell based on a decomposition-type porous substrate, comprising: preparing a double-sided asymmetric coated titanium-based PTL (PLA substrate), including: S1. Preparation of a transport layer green body material using a thermally decomposable porous material as a substrate and metal powder as a filler, or using metal powder as an internal filler of the substrate while simultaneously constructing a layered structure on the outer surface of the substrate, including: 1) Raw material preparation: Decomposable porous substrate: PLA nonwoven fabric, 150μm thick, 35μm fiber diameter; Titanium powder A (fine powder): average particle size 5μm, used for the microporous layer on the membrane electrode side; Titanium powder B (coarse powder): average particle size 15μm, used for the coarse-porous layer on the flow field side; Adhesive: PVB (polyvinyl butyral); Solvent: Ethanol (anhydrous).

[0096] 2) Asymmetric slurry preparation: Microporous layer slurry: 4g titanium powder A + 0.75g PVB + 15ml ethanol, solid content approximately 24%; Coarse-porous layer slurry: 24g titanium powder B + 2.0g PVB + 50ml ethanol, solid content approximately 35%.

[0097] 3) Green body preparation: 1) Coarse-porous layer coating: a. Fix the PLA substrate on the coating stage b. Coat one side of the substrate with a coarse-pore slurry, with a wet film thickness of approximately 200 μm. c. Deep penetration treatment: Immediately after coating, vacuum to ~0.10MPa and maintain for 12 minutes. The coarse-pore slurry completely penetrates the 150μm PLA substrate under negative pressure. Apply pressure of 0.4MPa with a scraper and scrape back and forth 3 times to further promote slurry penetration and remove air bubbles. When viewed from the back, the slurry should be seen to have completely penetrated to the back side.

[0098] d. Dry in a ventilated oven at 60°C for 1.5 hours to remove the ethanol solvent. The thickness of the green body after drying is about 200-220 μm.

[0099] 2) Microporous layer coating: a. Turn the coarse-pore layer green body over and coat the uncoated side with fine-pore layer slurry, with a wet film thickness of about 80-100 μm; b. Dry at 60°C for 1 hour to form a microporous layer; c. The total thickness of the green body is approximately 250–270 μm; S2. In an inert or reducing atmosphere, the transport layer green blank is heat-treated at a first temperature to prepare a transport layer green blank having channels oriented along the porous material skeleton direction, including: Argon gas was introduced for protection, and the temperature was slowly increased to 280°C at a rate of 1°C / min and held for 5 hours to complete the decomposition of the PLA substrate. This step forms directional channels that penetrate the main body layer.

[0100] S3. The transport layer green blank, after heat treatment at the first temperature, is further sintered at a second temperature higher than the first temperature to form microporous channels between metal powders, including: Heat to 1000°C (under argon protective atmosphere) and hold for 2 hours to complete the simultaneous sintering of coarse and fine powders, with the interface naturally fused. Naturally cooled to room temperature, a double-sided asymmetric coated titanium-based PTL was obtained.

[0101] Product performance: Microporous layer pore size: 8–12 μm, porosity 50%; Matrix layer pore size: 30–50 μm, porosity 70%; The thickness gradient structure is good, with a total thickness of 230 μm (sintering shrinkage of about 15% to 20%).

[0102] Example 4 This embodiment discloses a method for preparing a porous transport layer for an electrolytic cell based on a decomposition-type porous substrate, comprising continuous roll-to-roll preparation of a double-sided powder-coated PTL, including: S1. Preparation of a transport layer green body material using a thermally decomposable porous material as a substrate and metal powder as a filler, or using metal powder as an internal filler of the substrate while simultaneously constructing a layered structure on the outer surface of the substrate, including: 1) Raw material preparation: Decomposable porous substrate: PLA fiber felt, 180μm thick, 40μm fiber diameter, supplied in roll form; Titanium powder: average particle size 10μm.

[0103] 2) Continuous process for green body preparation: a. Roll-to-roll powder spreading and rolling: The base roll passes through the powder spreading unit at a speed of 1.2m / min, with powder spread on both sides simultaneously, 200g / m² on each side; b. Penetration rolling process: Pre-rolling: First, apply a light pressure of 3MPa to allow the powder to initially adhere to the substrate; Main rolling: Online warm rolling temperature 60°C, main rolling pressure increased to 10MPa (high pressure ensures full powder penetration); The use of a roll surface with microporous texture enhances the propulsion of powder into the pores of the substrate; Powder penetration rate >95%, the substrate fiber is completely coated with titanium powder; The raw material is rolled up and stored.

[0104] S2. In an inert or reducing atmosphere, the transport layer green blank is heat-treated at a first temperature to prepare a transport layer green blank having channels oriented along the porous material skeleton direction, including: PLA substrate was decomposed at 250–300°C, with a residence time of 30 minutes in an inert atmosphere and a flow rate controlled at 100 ml / min.

[0105] S3. The transport layer green blank, after heat treatment at the first temperature, is further sintered at a second temperature higher than the first temperature to form microporous channels between metal powders, including: Titanium powder was sintered at 850–950°C, held for 20 minutes, and then cooled in a protective atmosphere. The flow rate was controlled at 100 ml / min, and the discharge temperature was <100°C.

[0106] Product performance: Final PTL thickness: 250 μm (standard deviation ±6 μm); Continuous production efficiency: 25 m² / h; Performance consistency: resistance difference between batches <3%.

[0107] Key points for temperature control: PLA decomposition: 250–300°C (relatively low decomposition temperature).

[0108] Atmosphere selection principles: Titanium-based PTL: Vacuum or inert atmosphere (to prevent oxidation); Nickel-based PTL: Reducing atmosphere (removes surface oxide layer).

[0109] Rolling parameter optimization: Rolling pressure: 6MPa~10MPa (to ensure powder bonding and avoid substrate damage); Rolling speed: 0.3m / min~0.8m / min (balancing efficiency and quality); Rolling temperature: 50-80°C warm rolling can be used to improve the bonding effect.

[0110] Comparative Example 1 The difference from Example 1 is that commercially available titanium fiber felt (180 μm thick, 60% porosity) was used instead of PMMA fiber in Example 1 as a control. All other conditions and testing conditions were the same as in Example 1. The SEM image of the prepared product is shown below. Figure 3 As shown: Pore ​​structure: randomly distributed, tortuosity 3.2; Contact resistance: 12 mΩ·cm² (300% higher than Example 1); Breathability: 45% lower than in Example 1; Poor thickness uniformity: ±25μm.

[0111] Comparative Example 2 The difference from Example 2 is that it uses commercially available nickel foam (150 μm thickness, 300 μm pore size, 75% porosity), and its cross-sectional electron microscope image is shown below. Figure 3 As shown, the test conditions are the same as in Example 2: It contains many blind pores, with an effective porosity of only 60%. Electrical conductivity: 8 × 10³ S / cm (38% lower than in Example 2); It has poor mechanical strength and is easily broken. Thickness control is difficult, and there are large batch variations (±30μm).

[0112] The results show that: As shown in Examples 1 to 4, the PTL thickness is 180 μm to 250 μm; porosity is 40% to 82%; directional channel diameter is 30 μm to 50 μm; interparticle micropore size is 5 μm to 12 μm; tortuosity is 1.6 to 1.8; contact resistance is 2.5 mΩ·cm² to 3.0 mΩ·cm²; compressive strength is ≥2.6 MPa; and electrical conductivity is ≥1.3 × 10⁻⁶. 4 S / cm; corrosion rate <0.07μm / year.

[0113] Comparative examples and comparative examples show that the titanium-based PTL prepared by this invention has 45% higher permeability than traditional titanium felt, and the nickel-based PTL has 65% higher permeability than traditional nickel foam. This improvement enables the titanium-based PTL to transport gases more efficiently in proton exchange membrane (PEM) electrolyzers and anion exchange membrane (AEM) electrolyzers, significantly improving the overall performance of the electrolyzer.

[0114] This invention achieves a dual-scale pore structure design through a stepped heat treatment process: a main channel (30–50 μm directional pores) and secondary pores (5–10 μm micropores). This structure not only reduces the tortuosity of gas transport but also provides good lateral connectivity and surface contact through the microporous network, further optimizing the gas transport path.

[0115] This invention effectively reduces the tortuosity of the gas transport path from 3.2 to 1.8 by forming low-torsion directional channels extending along the fiber direction during the thermal decomposition of the decomposable substrate. The gas transport resistance is significantly reduced by 30%–50% compared to traditional PTLs. This improvement directly enhances the gas transport efficiency of the electrolyzer and reduces energy loss.

[0116] The titanium-based PTL prepared by this invention has 45% higher permeability than traditional titanium felt, and the nickel-based PTL has 65% higher permeability than traditional nickel foam. This improvement enables the titanium-based PTL to transport gases more efficiently in proton exchange membrane (PEM) electrolyzers and anion exchange membrane (AEM) electrolyzers, significantly improving the overall performance of the electrolyzers.

[0117] The PTL of this invention can significantly improve the current density and stability of electrolytic cells in practical applications. For example, the current density of the titanium-based PTL in a PEM electrolytic cell can reach 3-5 A / cm², which is 20%-30% higher than that of the conventional PTL; the nickel-based PTL exhibits higher conductivity and stability in an AEM electrolytic cell, and the corrosion rate is significantly reduced.

[0118] This invention optimizes process parameters, lowers sintering temperature, and reduces energy consumption by 15%–25%. It also avoids complex molds and multi-step processes, significantly reducing production costs. Furthermore, this invention supports continuous roll-to-roll production, increasing production efficiency by 2–3 times compared to traditional methods, further enhancing the feasibility of industrial applications.

[0119] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a porous transport layer for an electrolyzer based on a decomposition-type porous substrate, characterized in that, include: S1: A transport layer green body is prepared by using a porous material capable of thermal decomposition as a substrate and metal powder as a filler, or by using metal powder as an internal filler of the substrate while constructing a layered structure on the outer surface of the substrate. S2: In an inert or reducing atmosphere, the transport layer green blank is heat-treated at a first temperature to prepare a transport layer green blank with channels extending oriented along the porous material skeleton direction. S3: The transport layer green body after heat treatment at the first temperature is further sintered at a second temperature higher than the first temperature to form microporous channels between metal powders.

2. The method for preparing a porous transport layer for an electrolyzer based on a decomposition-type porous substrate according to claim 1, characterized in that, Step S1 involves preparing the transport layer green blank by slurry coating or powder rolling.

3. The method for preparing a porous transport layer for an electrolytic cell based on a decomposition-type porous substrate according to claim 2, characterized in that, The metal powder in step S1 is titanium powder or nickel powder.

4. The method for preparing a porous transport layer for an electrolyzer based on a decomposition-type porous substrate according to claim 3, characterized in that, Titanium powder has a particle size of 1 μm to 50 μm; nickel powder has a particle size of 0.5 μm to 30 μm.

5. The method for preparing a porous transport layer for an electrolyzer based on a decomposition-type porous substrate according to claim 1, characterized in that, The porous material that can be thermally decomposed in step S1 is one or more of polylactic acid (PLA), polymethyl methacrylate (PMMA), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), and polypropylene (PP).

6. The method for preparing a porous transport layer for an electrolyzer based on a decomposition-type porous substrate according to claim 1, characterized in that, The porosity of porous materials ranges from 30% to 85%.

7. The method for preparing a porous transport layer for an electrolyzer based on a decomposition-type porous substrate according to claim 1, characterized in that, The first temperature range is 200℃~400℃.

8. The method for preparing a porous transport layer for an electrolyzer based on a decomposition-type porous substrate according to claim 1, characterized in that, When the metal powder is titanium powder, the sintering temperature is 800°C to 1200°C.

9. The method for preparing a porous transport layer for an electrolyzer based on a decomposition-type porous substrate according to any one of claims 1-8, characterized in that, When the metal powder is nickel powder, the sintering temperature is 600°C to 1000°C.

10. A porous transport layer for an electrolyzer prepared based on a decomposition-type porous substrate, characterized in that, The porous transport layer for an electrolytic cell is prepared by the method described in any one of claims 1-9, based on a decomposition-type porous substrate. The porous transport layer has a thickness of 180 μm to 250 μm; a porosity of 40% to 82%; a directional channel diameter of 30 μm to 50 μm; interparticle micropore diameter of 5 μm to 12 μm; a tortuosity of 1.6 to 1.8; a contact resistance of 2.5 mΩ·cm² to 3.0 mΩ·cm²; a compressive strength ≥ 2.6 MPa; and an electrical conductivity ≥ 1.3 × 10⁻⁶. 4 S / cm.

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