阅读说明：本技术 一种气体扩散层及其制备方法和应用 (Gas diffusion layer and preparation method and application thereof ) 是由 曹婷婷 米新艳 崔新然 马千里 王茁 李军泽 于 2020-05-06 设计创作，主要内容包括：本发明提供了一种气体扩散层及其制备方法和应用,所述气体扩散层包括多孔支撑层和微孔导电层；其中,所述多孔支撑层的骨架材料为聚合物纤维。本发明提供的气体扩散层具有良好的气体扩散性,并且可以阻隔水分传输；同时本发明提供的气体扩散性的柔韧性较佳,避免了传统材料的易碎性；同时聚合物纤维成本较低,可降低气体扩散层的应用成本。(The invention provides a gas diffusion layer and a preparation method and application thereof, wherein the gas diffusion layer comprises a porous supporting layer and a microporous conducting layer; wherein the skeleton material of the porous support layer is polymer fiber. The gas diffusion layer provided by the invention has good gas diffusivity and can block moisture transmission; meanwhile, the gas diffusivity provided by the invention has better flexibility, and the fragility of the traditional material is avoided; meanwhile, the polymer fiber has lower cost, and the application cost of the gas diffusion layer can be reduced.)

1. A gas diffusion layer comprising a porous support layer and a microporous conductive layer;

wherein the skeleton material of the porous support layer is polymer fiber.

2. The gas diffusion layer of claim 1, wherein the polymer fibers comprise any one of or a combination of at least two of polyamide fibers, polyester fibers, polyvinyl alcohol fibers, polypropylene fibers, or polyacrylonitrile fibers;

preferably, the porous support layer has a polymer fiber cloth as a skeleton;

preferably, the polymer fiber cloth comprises a woven fiber cloth and/or a non-woven fiber cloth;

preferably, the thickness of the polymer fiber cloth is 100-400 μm, the porosity is 60-80%, and the average pore diameter is 10-30 nm.

3. The gas diffusion layer of claim 1 or 2, wherein the porous support layer further comprises an electrically conductive composite material filled in the pores of the framework;

preferably, the mass ratio of the framework material to the conductive composite material is (3-4) to (0.4-1.2);

preferably, the conductive composite includes a conductive agent and a binder;

preferably, the conductive agent is selected from any one or a combination of at least two of conductive carbon black, acetylene black, carbon fiber or graphene;

preferably, the adhesive is selected from any one or a combination of at least two of polytetrafluoroethylene, polyvinylidene fluoride, polychlorotrifluoroethylene, tetrachloroethylene-ethylene copolymer or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer;

preferably, the mass ratio of the conductive agent to the adhesive is (0.5-1): (3-5).

4. A gas diffusion layer according to any of claims 1 to 3, wherein the thickness of the gas diffusion layer is 150-550 μm, and the average pore size is 5-20 nm;

preferably, the porous scaffold layer has an average pore size of 8 to 20 nm;

preferably, the microporous conductive layer has a thickness of 1 to 10 μm and an average pore diameter of 5 to 20 nm.

5. The gas diffusion layer according to any one of claims 1 to 4, wherein the preparation raw materials of the microporous conductive layer comprise a conductive agent, a hydrophobic agent, a pore-forming agent and a solvent;

preferably, the conductive agent is selected from any one or a combination of at least two of conductive carbon black, acetylene black, carbon fiber or graphene;

preferably, the hydrophobic agent is selected from any one or a combination of at least two of polytetrafluoroethylene, polyvinylidene fluoride, polychlorotrifluoroethylene, tetrachloroethylene-ethylene copolymer or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer;

preferably, the pore-forming agent is selected from any one of ammonium carbonate, ammonium bicarbonate, ammonium oxalate, ammonium nitrate, ammonium sulfate, sodium carbonate or sodium sulfate or a combination of at least two of the ammonium carbonate, the ammonium bicarbonate, the ammonium oxalate, the ammonium nitrate, the ammonium sulfate, the sodium carbonate or the sodium sulfate;

preferably, the solvent is selected from any one of water, isopropanol, ethanol, methanol or N, N-dimethylformamide or a combination of at least two thereof;

preferably, the mass ratio of the conductive agent to the hydrophobic agent to the pore-forming agent to the solvent is 1 (0.5-1.5) to (0.1-0.3) to (5-25).

6. Method for the preparation of a gas diffusion layer according to any of claims 1 to 5, characterized in that it comprises the following steps:

(1) filling a conductive composite material in pores of the polymer fiber cloth to obtain a porous supporting layer;

(2) and coating a microporous conductive layer material on the surface of the porous support layer, drying and sintering to obtain the gas diffusion layer.

7. The preparation method according to claim 6, wherein the specific steps of filling the pores of the polymer fiber cloth with the conductive composite material are as follows: soaking the polymer fiber in the conductive composite material for 5-30min, taking out the polymer fiber after soaking is finished, removing the redundant conductive composite material, and then spreading, drying and sintering;

preferably, the conductive composite material further comprises a pore-foaming agent;

preferably, the porogen is selected from any one of ammonium carbonate, ammonium bicarbonate, ammonium oxalate, ammonium nitrate, ammonium sulfate, sodium carbonate or sodium sulfate or a combination of at least two thereof.

8. The method according to claim 6 or 7, wherein the step (2) further comprises standing after the microporous conductive layer material is coated;

preferably, after the standing, the thickness difference of the microporous conductive layer materials is not more than 1 μm;

preferably, the standing time is 5-30 min.

9. The method according to any one of claims 6 to 8, wherein the temperature of the drying in the step (2) is 80 to 150 ℃;

preferably, the drying mode is vacuum drying;

preferably, the sintering temperature is 200-400 ℃;

preferably, the sintering is carried out under a protective atmosphere;

preferably, the protective atmosphere is selected from any one of nitrogen, argon or helium or a combination of at least two thereof.

10. Use of a gas diffusion layer according to any of claims 1 to 5 in a fuel cell.

Technical Field

The invention belongs to the technical field of fuel cell materials, and relates to a gas diffusion layer and a preparation method and application thereof.

Background

Compared with a pure electric vehicle, the hydrogen fuel cell vehicle has the advantages of short hydrogenation time and long endurance, and hydrogen energy is renewable clean energy and has the advantages of wide source, zero pollution, zero emission and no secondary pollutionIs suitable for medium and large-scale storage. As a big international hydrogen-producing country, China has the dual functions of traditional energy hydrogen production and renewable energy hydrogen production, and hydrogen transportation systems and hydrogen adding stations are mature day by day. According to H₂The statistical report data of global hydrogen stations issued by station.org shows that by the end of 2018, 369 hydrogen stations are globally owned, wherein 152 are owned in Europe, 136 are owned in Asia and 78 are owned in North America; by the end of 2018, 26 hydrogenation stations are built or operated in China. The hydrogen energy industry has great advantages, and is disputed by various countries to be applied to the fields of military industry, power generation, modern industry and the like, and the hydrogen energy has been originally exposed to the Fengmai in the field of automobile industry at present. Compared with the traditional new energy automobile, the fuel cell automobile taking hydrogen energy as fuel has the characteristics of long driving range, high power performance, short fuel filling time and the like by virtue of the clean characteristic, is in continuous and rapid development in the field of new energy automobiles, and has considerable application conditions in the future.

The fuel cell system has a structure similar to that of a conventional engine system, a hydrogen storage bottle replaces an oil tank, and a fuel cell stack at the core of the fuel cell system replaces the conventional engine. The core parts of the fuel cell stack are membrane electrode composed of proton exchange membrane, catalyst and gas diffusion layer, the gas diffusion layer plays the role of electron conduction, current collection, gas guide, water drainage and membrane electrode support in the fuel cell stack. The main base material of the gas diffusion layer is usually graphitized carbon fiber paper, gas conduction and water molecule transmission are carried out by utilizing pore travel channels among fibers, and meanwhile, the loose and porous appearance of the carbon fiber paper plays a role in supporting the membrane electrode. However, the traditional graphitized carbon fiber paper is adopted to manufacture the gas diffusion layer, so that the problem exists in the actual operation, the carbon paper is fragile in the transportation and storage processes, the preparation of the hydrophobic layer on the surface of the carbon paper is affected by bending, extruding and needling, and in the production process of the gas diffusion layer, the carbon paper is damaged by bending, soaking and transferring large-size base materials, so that the cost of the gas diffusion layer is increased, and the preparation efficiency is affected.

CN1988225A discloses a gas diffusion layer for a proton exchange membrane fuel cell and a preparation method thereof, wherein the gas diffusion layer comprises a porous support layer and a microporous layer, and the porous support layer is a mesh-shaped and porous structure. The microporous layer is compounded on the surface of the porous support layer close to one side of the catalytic layer. The microporous layer uniformly covers the surfaces of the macropores and the fiber-dense region of the porous support layer and does not penetrate into the interior of the porous support layer. Although the preparation method of the gas diffusion layer provided by the patent is simple, the carbon paper, the carbon cloth and the like used by the gas diffusion layer are fragile and easy to break, and the gas diffusion layer is adversely affected. CN102856567A discloses an integrated renewable fuel cell gas diffusion layer and a preparation method thereof, wherein non-conductive organic synthetic fiber cloth is used as a support body of the diffusion layer, a conductive corrosion-resistant metal/metal oxide network is constructed on the support body, the conductive corrosion-resistant metal/metal oxide network is filled in pores of organic fibers, and a certain hydrophobic agent and a certain bonding agent are combined, so that the diffusion layer achieves proper hydrophilic and hydrophobic properties and a proper pore structure is constructed, and the mass transfer balance of URFC in different working modes is ensured; the gas transmission layer provided by the patent has larger pore diameter and cannot prevent the transmission of moisture; and metal particles are added, so that the weight is heavier, and the application is not facilitated.

Therefore, a gas transmission layer with good flexibility, good hydrophobic gas guiding performance and simple preparation method needs to be developed, so that the application purpose is achieved and the cost can be saved.

Disclosure of Invention

The invention aims to provide a gas diffusion layer and a preparation method and application thereof. The gas diffusion layer provided by the invention has good gas diffusivity and can block moisture transmission; meanwhile, the gas diffusivity provided by the invention has better flexibility, and the fragility of the traditional material is avoided; meanwhile, the polymer fiber has lower cost, and the application cost of the gas diffusion layer can be reduced.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a gas diffusion layer comprising a porous support layer and a microporous conductive layer;

wherein the skeleton material of the porous support layer is polymer fiber.

The polymer fiber is used as a framework material of the porous supporting layer, has the advantages of good flexibility and bending resistance, and can avoid the defect that the carbon paper used in the prior art is fragile; meanwhile, the polymer fiber has lower cost, and is beneficial to reducing the application cost of the gas diffusion layer.

Preferably, the polymer fibers comprise any one of or a combination of at least two of polyamide fibers, polyester fibers, polyvinyl alcohol fibers, polypropylene fibers, or polyacrylonitrile fibers.

Preferably, the porous support layer has a polymer fiber cloth as a skeleton.

Preferably, the polymer fiber cloth comprises a woven fiber cloth and/or a non-woven fiber cloth.

Preferably, the polymer fiber cloth has a thickness of 100-400 μm, such as 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, etc., a porosity of 60-80%, such as 65%, 70%, 75%, etc., and an average pore diameter of 10-30nm, such as 15nm, 20nm, 25nm, etc.

Preferably, the porous support layer further comprises a conductive composite material filled in the pores of the skeleton.

The invention arranges the conductive composite material in the pores of the framework to ensure that the porous supporting layer has good conductivity, and simultaneously, as the pores of the framework are not uniform and exist in a multi-level pore form, small pores which can not be penetrated by partial conductive fillers exist in the framework, and pores with larger pore diameters which can not be completely filled by the conductive composite fillers also exist, so that the finally obtained porous supporting layer still has higher porosity and is convenient for gas diffusion.

Preferably, the mass ratio of the framework to the conductive composite material is (3-4): (0.4-1.2), the 3-4 can be 3.2, 3.4, 3.5, 3.6, 3.8, 3.9, etc., and the 0.4-1.2 can be 0.6, 0.8, 1.0, 1.1, etc.

In the invention, the porous support layer has better conductivity and higher porosity by adjusting the mass ratio of the framework material to the conductive composite material; if the addition amount of the conductive composite material is too low, the conductivity of the porous support layer is poor, and if the addition amount of the conductive composite material is too high, the porosity of the finally obtained porous support layer is low due to the fact that the conductive composite material filled in the pores of the framework is too much, and further the gas diffusion performance in the using process is influenced.

Preferably, the conductive composite includes a conductive agent and a binder.

Preferably, the conductive agent is selected from any one of or a combination of at least two of conductive carbon black, acetylene black, carbon fiber or graphene.

The conductive carbon black is preferably super P and/or Vulcan XC-72; the carbon fiber is preferably Vapor Grown Carbon Fiber (VGCF).

Compared with metal or metal oxide as a conductive agent, the conductive agent selected by the invention has excellent conductivity and light weight, and can be tightly combined with polymer fibers under the action of the adhesive.

Preferably, the binder is selected from any one of or a combination of at least two of polytetrafluoroethylene, polyvinylidene fluoride, polychlorotrifluoroethylene, tetrachloroethylene-ethylene copolymer or tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer.

The adhesive has an adhesive effect on one hand and hydrophobic performance on the other hand, so that the subsequent hydrophobic treatment process of the gas diffusion layer can be reduced by using the adhesive in the conductive composite material, the production steps are simplified, and the cost is saved.

Preferably, the mass ratio of the conductive agent to the adhesive is (0.5-1): (3-5).

Said 0.5-1 can be 0.6, 0.7, 0.8, 0.9, etc., said 3-5 can refer to 3.2, 3.5, 3.7, 4, 4.2, 4.5, 4.7, etc.

If the amount of the conductive filler added is too high, the hydrophobic property of the gas diffusion layer is lowered, and if the amount of the binder added is too high, the electrical conductivity of the gas diffusion layer is affected.

Preferably, the thickness of the gas diffusion layer is 150-550 μm, such as 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm, etc., and the average pore diameter is 5-20nm, such as 6nm, 7nm, 8nm, 10nm, 12nm, 14nm, 15nm, 18nm, 19nm, etc.

Preferably, the porous scaffold layer has an average pore size of 8-20nm, such as 10nm, 12nm, 14nm, 15nm, 18nm, 19nm, and the like.

Preferably, the microporous conductive layer has a thickness of 1-10 μm, such as 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, etc., and an average pore diameter of 5-20nm, such as 8nm, 10nm, 12nm, 15nm, 18nm, etc.

Because the pore diameter of the porous support layer is larger, gas can be ensured to pass through, and meanwhile, moisture can also pass through, so that the gas and the moisture can be better transmitted and managed by arranging the microporous layer with smaller pore diameter.

Preferably, the preparation raw materials of the microporous conducting layer comprise a conducting agent, a hydrophobic agent, a pore-forming agent and a solvent.

Preferably, the conductive agent is selected from any one of or a combination of at least two of conductive carbon black, acetylene black, carbon fiber or graphene.

Preferably, the hydrophobic agent is selected from any one of Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), Polychlorotrifluoroethylene (PCTFE), tetrachloroethylene-ethylene copolymer (ETFE), or tetrafluoroethylene-perfluoroalkylvinyl ether copolymer (PFA), or a combination of at least two thereof.

Preferably, the pore former is selected from any one of ammonium carbonate, ammonium bicarbonate, ammonium oxalate, ammonium nitrate, ammonium sulfate, sodium carbonate or sodium sulfate or a combination of at least two thereof.

Preferably, the solvent is selected from any one of water, isopropanol, ethanol, methanol or N, N-dimethylformamide or a combination of at least two thereof.

Preferably, the mass ratio of the conductive agent to the hydrophobic agent to the pore-forming agent to the solvent is 1 (0.5-1.5) to (0.1-0.3) to (5-25).

The microporous conducting layer is arranged, so that the hydrophobic structure of the gas diffusion layer can be optimized, the gas and moisture conduction can be supported, and the membrane electrode can be supported more effectively. The flexible gas diffusion layer can conduct excessive water and plays a role in water management inside the electric pile.

The 0.5-1.5 can be 0.8, 1.0, 1.2, etc., the 0.1-0.3 can be 0.15, 0.20, 0.25, etc., the 5-25 can be 8, 10, 12, 15, 18, 20, 22, etc.

In a second aspect, the present invention provides a method for preparing a gas diffusion layer according to the first aspect, comprising the steps of:

(1) filling a conductive composite material in pores of the polymer fiber cloth to obtain a porous supporting layer;

(2) and coating a microporous conductive layer material on the surface of the porous support layer, drying and sintering to obtain the gas diffusion layer.

The preparation method provided by the invention is simple, has low cost and is beneficial to industrial production.

Preferably, the specific steps of filling the conductive composite material in the pores of the polymer fiber cloth are as follows: soaking the polymer fiber in the conductive composite material for 5-30min, taking out the polymer fiber after soaking is finished, removing the redundant conductive composite material, and then spreading, drying and sintering.

Preferably, the criteria for removing the excess conductive composite material is that no material liquid remains stranded on the surface of the polymer fiber, and the surface conductive composite material loading reaches 20mg/cm²。

Preferably, the conductive composite material further comprises a pore-foaming agent.

Preferably, the porogen is selected from any one of ammonium carbonate, ammonium bicarbonate, ammonium oxalate, ammonium nitrate, ammonium sulfate, sodium carbonate or sodium sulfate or a combination of at least two thereof.

In order to further improve the porosity of the porous support layer so as to facilitate gas diffusion, a small amount of pore-forming agent can be added into the conductive composite material during the preparation of the porous support layer, and the pore-forming agent is decomposed in the subsequent sintering process.

Preferably, the step (2) further comprises standing after the microporous conductive layer material is coated.

Preferably, after the standing, the thickness difference of the microporous conductive layer material is not more than 1 μm.

Because the material slightly sinks in the standing process, when the thickness difference of the material is not more than 1 μm, the drying and sintering are carried out.

Preferably, the standing time is 5-30min, such as 10min, 15min, 20min, 25min, and the like.

Preferably, the drying temperature in step (2) is 80-150 deg.C, such as 90 deg.C, 100 deg.C, 110 deg.C, 120 deg.C, 130 deg.C, 140 deg.C, etc.

Preferably, the drying mode is vacuum drying.

Preferably, the sintering temperature is 200-400 ℃, such as 250 ℃, 300 ℃, 350 ℃ and the like.

Preferably, the sintering is performed under a protective atmosphere.

Preferably, the protective atmosphere is selected from any one of nitrogen, argon or helium or a combination of at least two thereof.

In a third aspect, the present invention provides the use of a gas diffusion layer according to the first aspect in a fuel cell.

Compared with the prior art, the invention has the following beneficial effects:

(1) the polymer fiber is used as a framework material of the porous supporting layer, has the advantages of good flexibility and bending resistance, and can avoid the defect that the carbon paper used in the prior art is fragile; meanwhile, the polymer fiber has lower cost, which is beneficial to reducing the application cost of the gas diffusion layer;

(2) the gas diffusion layer has good flexibility and folding resistance, good air permeability and good conductivity, wherein the bending radius can reach more than 3cm in a test, and the porosity is 60-80%.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

The following examples and comparative examples relate to materials and brand information as shown in table 1:

TABLE 1