Gas diffusion layer with gradient pore structure and membrane electrode assembly

Abstract

The utility model provides a gas diffusion layer with a gradient pore structure and a membrane electrode assembly. The gas diffusion layer comprises a substrate layer and a macroporous coating attached to the surface of the substrate layer, the average thickness of the matrix layer is 250-500 [mu] m, and the average pore size is not greater than 50 [mu] m; the macroporous coating is a Ti coating, the average thickness of the macroporous coating is 40-90 [mu] m, the average pore size of the macroporous coating is not smaller than 15 [mu] m, and the average pore size of the macroporous coating is smaller than that of the matrix layer. According to the gas diffusion layer provided by the utility model, through uniform and gradient pore arrangement, high-efficiency gas transmission efficiency is maintained, and the gas diffusion layer has excellent conductive performance.

Description

Technical Field

[0001] The utility model belongs to the technical field of fuel cells, and more specifically relates to a gas diffusion layer and a membrane electrode assembly with a gradient pore structure. Background Art

[0002] As an important component in fuel cells or electrolyzers, the gas diffusion layer not only provides a transport channel for gaseous reactants and liquid solutions, but also provides a conduction channel for electricity and heat.

[0003] The commonly used gas diffusion layer currently consists of a porous carbon fiber base layer and a microporous layer. The porous carbon fiber base layer usually uses carbon paper or carbon cloth, with a thickness of 100 - 400 μm, and its main function is to support the microporous layer and stabilize the membrane electrode structure. The microporous layer usually refers to the carbon powder layer on the base layer, with a thickness of 10 - 100 μm, and its main function is to improve the pore structure of the base layer, reduce the contact resistance between the base layer and the catalytic layer, enable the reaction gas to quickly pass through the diffusion layer and be evenly distributed on the surface of the catalytic layer for reaction, and at the same time, timely drain away the generated water to prevent the catalytic layer from being flooded.

[0004] For example, patent CN218498104U provides a gas diffusion layer and a fuel cell. The gas diffusion layer includes a porous carbon fiber base layer and a microporous layer that are in contact with each other; the porous carbon fiber base layer is arranged close to the electrode plate of the fuel cell, and the microporous layer is arranged close to the catalytic layer of the fuel cell; a flow channel is arranged on one side surface of the porous carbon fiber base layer close to the electrode plate. This solution also provides a fuel cell prepared from the above gas diffusion layer. By arranging a flow channel on the porous carbon fiber base layer of the fuel cell gas diffusion layer, the problem of difficult processing of flow channels on the electrode plate can be avoided, and the problem of the transport and uniform distribution of reaction gases in the fuel cell can also be well solved; at the same time, the electrode plate can be thinned, and the power density and battery performance of the fuel cell stack can be greatly improved.

[0005] However, the pore distribution between the layers in the current gas diffusion layer cannot meet the transmission requirements of liquid, gas, electricity, and heat. Exploring a more reasonable layered pore structure for the gas diffusion layer and improving the transmission efficiency of water - gas - electricity - heat is an urgent problem to be solved in the current field. Summary of the Utility Model

[0006] In view of the defects existing in the above-mentioned prior art, the present utility model provides a gas diffusion layer and a membrane electrode assembly with a gradient pore structure. The gas diffusion layer includes a substrate layer and a macroporous coating attached to the surface of the substrate layer. The average thickness of the substrate layer is 250 - 500 μm, and the average pore diameter is not greater than 50 μm. The macroporous coating is a Ti coating, with an average thickness of 40 - 90 μm, an average pore diameter not less than 15 μm, and the average pore diameter of the macroporous coating is smaller than that of the substrate layer. The gas diffusion layer provided by the present utility model maintains high gas transmission efficiency and excellent electrical conductivity through uniform and gradient pore settings.

[0007] In a first aspect, the present utility model provides a gas diffusion layer with a gradient pore structure, including a substrate layer and a macroporous coating attached to the surface of the substrate layer;

[0008] The average thickness of the substrate layer is 250 - 500 μm, and the average pore diameter is not greater than 50 μm;

[0009] The macroporous coating is a Ti coating, with an average thickness of 40 - 90 μm, an average pore diameter not less than 15 μm, and the average pore diameter of the macroporous coating is smaller than that of the substrate layer.

[0010] Further, the substrate layer is a titanium felt substrate, and the porosity of the substrate layer is 57% - 76%.

[0011] Further, the porosity of the macroporous coating is 40% - 65%.

[0012] Further, the average pore diameter of the substrate layer is 30 - 50 μm, and the average pore diameter of the macroporous coating is 15 - 25 μm.

[0013] Further, the gas diffusion layer further includes a microporous coating, and the microporous coating is attached to the surface of the macroporous coating;

[0014] The microporous coating is a Ti coating, with an average thickness of 5 - 10 μm, and the average pore diameter of the microporous coating is smaller than that of the macroporous coating.

[0015] Further, the average pore diameter of the microporous coating is 5 - 10 μm.

[0016] Further, the porosity of the microporous coating is 30% - 45%.

[0017] Further, the average surface roughness of the microporous coating is 5 - 15 μm.

[0018] Further, the average particle size of the particles in the macroporous coating is 25 - 40 μm, and the average particle size of the particles in the microporous coating is 20 - 80 nm.

[0019] In a second aspect, the present utility model further provides a membrane electrode assembly, comprising: a proton exchange membrane, a catalyst layer, and a gas diffusion layer;

[0020] The gas diffusion layer includes a substrate layer and a macroporous coating attached to the surface of the substrate layer;

[0021] The average thickness of the substrate layer is 250 - 500 μm, and the average pore diameter is not greater than 50 μm;

[0022] The macroporous coating is a Ti coating. The average thickness of the macroporous coating is 40 - 90 μm, the average pore diameter of the macroporous coating is not less than 15 μm, and the average pore diameter of the macroporous coating is less than the average pore diameter of the substrate layer.

[0023] Further, the substrate layer is a titanium felt substrate, and the porosity of the substrate layer is 57% - 76%.

[0024] Further, the porosity of the macroporous coating is 40% - 65%.

[0025] Further, the average pore diameter of the substrate layer is 30 - 50 μm, and the average pore diameter of the macroporous coating is 15 - 25 μm.

[0026] Further, the gas diffusion layer further includes a microporous coating, and the microporous coating is attached to the surface of the macroporous coating;

[0027] The microporous coating is a Ti coating. The average thickness of the microporous coating is 5 - 10 μm, and the average pore diameter of the microporous coating is less than the average pore diameter of the macroporous coating.

[0028] Further, the average pore diameter of the microporous coating is 5 - 10 μm.

[0029] Further, the porosity of the microporous coating is 30% - 45%.

[0030] Further, the average surface roughness of the microporous coating is 5 - 15 μm.

[0031] Further, the average particle size of the particles in the macroporous coating is 25 - 40 μm, and the average particle size of the particles in the microporous coating is 20 - 80 nm.

[0032] In a third aspect, the present utility model further provides a fuel cell, comprising any one of the above-mentioned membrane electrode assemblies.

[0033] In a fourth aspect, the present utility model further provides an electrolytic cell, comprising any one of the above-mentioned membrane electrode assemblies.

[0034] The gas diffusion layer and the membrane electrode assembly with a gradient pore structure provided by the present utility model have at least the following technical effects:

[0035] (1) The gas diffusion layer provided by the present utility model maintains high gas transmission efficiency and has excellent electrical conductivity through uniform and gradient pore settings.

[0036] (2) At the same time, for the gradient pore settings of the gas diffusion layer, the moisture content in the adjacent catalyst layer structure can also be ensured, avoiding affecting the performance of the membrane electrode assembly due to excessive or insufficient moisture. Description of the Drawings

[0037] By referring to the accompanying drawings and reading the following detailed description, the above and other objects, features, and advantages of the exemplary embodiments of the present disclosure will become readily understood. In the drawings, several embodiments of the present disclosure are shown in an exemplary rather than restrictive manner, and the same or corresponding reference numerals represent the same or corresponding parts, wherein:

[0038] Figure 1 is a schematic structural diagram of the gas diffusion layer with the first gradient pore structure of the embodiment of the present utility model;

[0039] Figure 2 is a schematic structural diagram of the gas diffusion layer with the second gradient pore structure of the embodiment of the present utility model;

[0040] Figure 3 is a schematic structural diagram of a membrane electrode assembly of the embodiment of the present utility model.

[0041] Description of the reference numerals: 1 - gas diffusion layer, 11 - substrate layer, 12 - macroporous coating, 13 - microporous coating, 2 - catalyst layer, 3 - proton exchange membrane. Detailed Embodiments

[0042] In order to make the objects, technical solutions, and advantages of the present utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0043] The terms used in the embodiments of the present utility model are only for the purpose of describing specific embodiments, and are not intended to limit the present utility model. The singular forms "a", "the", and "said" used in the embodiments of the present utility model and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. "Plural" generally includes at least two.

[0044] It should also be noted that the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, such that a commodity or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such commodity or device. Without further limitation, an element defined by the statement "comprising one..." does not exclude the presence of additional identical elements in the commodity or device comprising said element.

[0045] The gas diffusion layer is a key component in proton exchange membrane electrolyzers / fuel cells, and has multiple functions such as supporting the membrane assembly, supplying reaction water, removing gas products, and reducing ohmic resistance. To overcome the problem that the pore distributions in each layer of the current gas diffusion layer are uneven and the pore design between layers is irregular, resulting in low transmission efficiency of water-gas-electricity-heat in the gas diffusion layer.

[0046] The present utility model designs uniform and gradient pores in the gas diffusion layer, so that the gas diffusion layer maintains high gas diffusion efficiency and has excellent electrical conductivity.

[0047] The optional embodiments of the present utility model will be described in detail below with reference to the accompanying drawings.

[0048] See Figure 1 As shown, the present utility model provides a gas diffusion layer 1 with a gradient pore structure, which includes a matrix layer 11 and a macroporous coating 12 attached to the surface of the matrix layer.

[0049] Among them, the matrix layer uses a titanium felt matrix, and the titanium felt matrix has properties such as high strength, good heat insulation, high temperature resistance, corrosion resistance, and easy processing. The above characteristics enable the titanium felt matrix to play an important role in the gas diffusion layer, and can improve the performance and durability of the electrolyzer / fuel cell.

[0050] There are various choices for the thickness of the common titanium felt matrix. For example, 0.25mm, 0.4mm, 0.6mm, 0.8mm, 1.0mm, 2.0mm, 3.0mm, etc. The porosity of the titanium felt matrix is usually between 60-70%, which helps the mass transfer of gas-liquid.

[0051] The pore size range of the titanium felt matrix is relatively wide, generally between 1μm and 100μm. The larger pore size makes the titanium felt have better permeability and air permeability, but the larger pore size will reduce the electron transport efficiency and also increase the water loss; the smaller pore size will increase the mass transfer resistance.

[0052] Different combinations of parameters such as pore size, porosity, and pore distribution can affect the mass transfer efficiency and mechanical properties of the titanium felt matrix. The gas diffusion layer with a gradient pore structure given by the present utility model attaches a macroporous coating to the titanium felt matrix, and the required titanium felt matrix cannot be too thick, and the porosity and average pore size are moderate.

[0053] Therefore, the average thickness of the matrix layer 11 is 250 - 500 μm. The average pore size is not more than 50 μm, and preferably, the average pore size of the matrix layer 11 is 30 - 50 μm. The porosity of the matrix layer 11 is 57% - 76%.

[0054] To further improve the performance of the matrix layer, a macroporous coating 12 is coated on the surface of the matrix layer 11. The macroporous coating 12 is a Ti coating. The average thickness of the macroporous coating 12 is 40 - 90 μm. The average pore size of the macroporous coating 12 is not less than 15 μm, and the average pore size of the macroporous coating 12 is less than the average pore size of the matrix layer 11. Preferably, the average pore size of the macroporous coating 12 is 15 - 25 μm.

[0055] Preferably, the content of Ti element in the macroporous coating 12 is not less than 95 wt%. The porosity of the macroporous coating 12 is 40% - 65%.

[0056] At this time, the gas diffusion layer with a gradient pore structure formed by the titanium felt matrix attached with the macroporous coating has a conductivity not less than 4×10 5 S·m -1 , and the specific value is (4 - 8)×10 5 S·m -1 .

[0057] The macroporous coating 12 can improve the conductivity, catalytic activity, and antioxidant ability of the titanium felt matrix. In addition, the gradient pore structure formed by the macroporous coating 12 and the matrix layer 11 can improve the water management ability of the gas diffusion layer 1 to improve the liquid water transport.

[0058] As Figure 2 shown, the gas diffusion layer 1 further includes a microporous coating 13, and the microporous coating 13 is attached to the surface of the macroporous coating 12;

[0059] The microporous coating 13 is also a Ti coating. The average thickness of the microporous coating 13 is 5 - 10 μm. The average pore size of the microporous coating 13 is less than the average pore size of the macroporous coating 12. Preferably, the average pore size of the microporous coating is 5 - 10 μm; the content of Ti in the microporous coating 13 is not less than 95 wt%.

[0060] In addition, the porosity of the microporous coating 13 is 30% - 45%. The average surface roughness of the microporous coating 13 is 5 - 15 μm.

[0061] In this embodiment, a microporous coating 13 is reattached to the surface of the macroporous coating 12 to further optimize the pore structure of the gas diffusion layer, forming a three-layer gradient pore structure. The three-layer gradient pore structure can precisely control the transport and distribution of water, gas, electricity, and heat.

[0062] There are various coating methods for the macroporous coating 12 and the microporous coating 13. For example, they can be coated by spraying, impregnation-calcination method, physical deposition, chemical deposition, casting, etc.

[0063] When using Ti powder as the raw material to form the macroporous coating 12 and the microporous coating 13, the average particle size of the particles in the macroporous coating 12 is 25 - 40 μm, and the average particle size of the particles in the microporous coating 13 is 20 - 80 nm.

[0064] As Figure 3 shown, the present utility model also provides a membrane electrode assembly, including: a proton exchange membrane 3, a catalytic layer 2, and a gas diffusion layer 1 with the above-mentioned gradient pore structure.

[0065] The present utility model also provides a fuel cell, including any one of the above-mentioned membrane electrode assemblies.

[0066] The present utility model also provides an electrolytic cell, including any one of the above-mentioned membrane electrode assemblies.

[0067] Through the optimized design of the pore structure (involving porosity, pore size, and pore size gradient distribution), the present utility model designs a gas diffusion layer with better performance.

[0068] Performance test:

[0069] Performance tests are carried out on gas diffusion layer samples with two gradient pore structures as Figure 1 , as Figure 2 . The performance tests mainly measure the current density. Among them, the electrolyte used for measuring the current density is a KOH solution with a mass fraction of 30%. The operating temperature of the electrolytic cell is 80°C. An I-V (current density - voltage) curve graph is measured, and the current density at a voltage of 1.8 V is obtained.

[0070] Sample 1 includes a substrate layer and a macroporous coating. The average thickness of the substrate layer is 300 μm, the average pore size is 30 μm, and the porosity is about 60%; the macroporous coating is a Ti layer, the average thickness of the macroporous coating is 60 μm, the average pore size is 20 μm, and the porosity is 50%.

[0071] Sample 2 includes a substrate layer, a macroporous coating, and a microporous coating. The parameters of the substrate layer and the macroporous coating are the same as those of Sample 1. The microporous coating is a Ti layer, the average thickness of the microporous coating is 10 μm, the average particle size is 10 μm, and the porosity is 40%.

[0072] Through the test of the current density, it can be known that the current density of the electrolytic cell with Sample 1 and Sample 2 as the gas diffusion layer is greater than 2.1 A / cm 2 . The gas diffusion layers with gradient pore structures of Sample 1 and Sample 2 both meet the performance requirements.

[0073] The above introduces the preferred embodiments of the present invention, aiming to make the spirit of the present invention clearer and easier to understand, rather than to limit the present invention. Any modifications, substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection defined by the appended claims of the present invention.

Claims

1. A gas diffusion layer with a gradient pore structure, characterized in that: It includes a substrate layer and a macroporous coating layer attached to the surface of the substrate layer; The average thickness of the substrate layer is 250-500 μm, and the average pore size is no more than 50 μm; The macroporous coating is a Ti coating, the average thickness of the macroporous coating is 40-90 μm, the average pore size of the macroporous coating is not less than 15 μm, and the average pore size of the macroporous coating is smaller than the average pore size of the substrate layer.

2. The gas diffusion layer with gradient pore structure as claimed in claim 1, characterized in that: The base layer is a titanium felt base layer, and the porosity of the base layer is 57%-76%.

3. The gas diffusion layer with gradient pore structure according to claim 1, characterized in that: The porosity of the macroporous coating is 40%-65%.

4. The gas diffusion layer with gradient pore structure according to claim 1, characterized in that: The average pore size of the substrate layer is 30-50 μm, and the average pore size of the macroporous coating layer is 15-25 μm.

5. The gas diffusion layer with gradient pore structure as claimed in claim 1, characterized in that: The gas diffusion layer also includes a microporous coating layer, which is attached to the surface of the macroporous coating layer; The microporous coating is a Ti coating, the average thickness of the microporous coating is 5-10 μm, and the average pore size of the microporous coating is smaller than the average pore size of the macroporous coating.

6. The gas diffusion layer with gradient pore structure as claimed in claim 5, characterized in that: The average pore size of the microporous coating is 5-10 μm.

7. The gas diffusion layer with gradient pore structure as claimed in claim 5, characterized in that: The porosity of the microporous coating is 30%-45%.

8. The gas diffusion layer with gradient pore structure as claimed in claim 5, characterized in that: The average surface roughness of the microporous coating is 5-15 μm.

9. The gas diffusion layer with gradient pore structure as claimed in claim 5, characterized in that: The average particle size of the particles in the macroporous coating is 25-40 μm, and the average particle size of the particles in the microporous coating is 20-80 nm.

10. A membrane electrode assembly, characterized in that: include: A proton exchange membrane, a catalyst layer and a gas diffusion layer with a gradient pore structure as claimed in any one of claims 1 to 9.

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