阅读说明：本技术 燃料电池用气体扩散层及其制备方法 (Gas diffusion layer for fuel cell and method for preparing the same ) 是由 赵天寿 孙静 巫茂春 于 2021-08-27 设计创作，主要内容包括：本发明提供一种燃料电池用定向有序气体扩散层及其制备方法,涉及燃料电池技术领域。本发明的气体扩散层包括层叠设置的支撑层和微孔层；所述支撑层包括若干定向有序排列的第一碳纤维丝,以及若干交叉分布于所述第一碳纤维丝之间的第二碳纤维丝,所述第二碳纤维丝用于连接和支撑所述第一碳纤维丝；所述第一碳纤维丝和所述第二碳纤维丝的直径为1-20μm,相邻两根第一碳纤维丝之间的距离为10-30μm；所述微孔层包括若干直径为50-500nm的第三碳纤维丝,若干所述第三碳纤维丝之间相互堆叠形成微孔,所述微孔的孔径为0.1-1μm。本发明的气体扩散层采用静电纺丝法制备得到。本发明的气体扩散层可有效提高的排水性和透气性。(The invention provides a directional ordered gas diffusion layer for a fuel cell and a preparation method thereof, and relates to the technical field of fuel cells. The gas diffusion layer comprises a support layer and a microporous layer which are arranged in a laminated manner; the supporting layer comprises a plurality of first carbon fiber yarns which are arranged in an oriented and ordered manner, and a plurality of second carbon fiber yarns which are distributed among the first carbon fiber yarns in a crossed manner, wherein the second carbon fiber yarns are used for connecting and supporting the first carbon fiber yarns; the diameters of the first carbon fiber filaments and the second carbon fiber filaments are 1-20 micrometers, and the distance between every two adjacent first carbon fiber filaments is 10-30 micrometers; the microporous layer comprises a plurality of third carbon fiber yarns with the diameter of 50-500nm, the third carbon fiber yarns are mutually stacked to form micropores, and the pore diameter of each micropore is 0.1-1 mu m. The gas diffusion layer is prepared by an electrostatic spinning method. The gas diffusion layer of the present invention can effectively improve water drainage and gas permeability.)

1. A gas diffusion layer for a fuel cell, comprising a support layer and a microporous layer which are laminated; the supporting layer comprises a plurality of first carbon fiber yarns which are arranged in an oriented and ordered manner, and a plurality of second carbon fiber yarns which are distributed among the first carbon fiber yarns in a crossed manner, wherein the second carbon fiber yarns are used for connecting and supporting the first carbon fiber yarns; the diameters of the first carbon fiber filaments and the second carbon fiber filaments are 1-20 micrometers, and the distance between every two adjacent first carbon fiber filaments is 10-30 micrometers; the microporous layer comprises a plurality of third carbon fiber yarns with the diameter of 50-500nm, the third carbon fiber yarns are mutually stacked to form micropores, and the pore diameter of each micropore is 0.1-1 mu m.

2. The gas diffusion layer for a fuel cell according to claim 1, wherein the first carbon fiber filaments have a volume percentage of 50 to 95% in the support layer.

3. The gas diffusion layer for a fuel cell according to claim 1, wherein the thickness of the support layer is 100-300 μm.

4. The gas diffusion layer for a fuel cell according to claim 1, wherein the microporous layer has a thickness of 10 to 50 μm.

5. The gas diffusion layer for a fuel cell according to any one of claims 1 to 4, wherein the contact angle of the support layer is 100-170 °.

6. The gas diffusion layer for a fuel cell according to any one of claims 1 to 4, wherein the contact angle of the microporous layer is 100-170 °.

7. A method for producing a gas diffusion layer for a fuel cell according to any one of claims 1 to 6, comprising the steps of:

s1, preparing a spinning solution with the mass concentration of 10-15 wt% from a high molecular polymer, adding a water repellent, uniformly mixing, and performing electrostatic spinning to obtain a supporting layer;

s2, preparing a spinning solution with the mass concentration of 5-10 wt% from a high molecular polymer, and performing electrostatic spinning on one side of a supporting layer to obtain a composite fiber membrane with the supporting layer and a microporous layer integrated; or

Preparing a high molecular polymer into spinning solution with the mass concentration of 5-10 wt%, performing electrostatic spinning to form a microporous layer, and overlapping one side surface of the supporting layer and one side surface of the microporous layer to form a composite fiber membrane;

s3, pre-oxidizing and carbonizing the composite fiber membrane to obtain the gas diffusion layer.

8. The method according to claim 7, wherein the high molecular polymer is selected from the group consisting of: polyacrylonitrile, pitch, lignin, polyimide, polyvinylidene fluoride, polyvinyl alcohol, polyvinyl pyrrolidone; the water repellent is selected from: one or more of polytetrafluoroethylene, fluorinated ethylene propylene and polydimethylsiloxane.

9. The method according to claim 7, wherein in S1, the parameters of electrospinning are as follows: the diameter of the needle is 0.2-2mm, and the advancing speed of the spinning solution is 0.5-2mL h^-1The distance between the needle and the receiver is 10-50cm, the rotating speed of the receiving end rotating wheel is 100-1000rpm, and the voltage between the needle and the receiving end is 0.5-1.5kV cm^-1The temperature is 20-35 ℃, and the relative humidity is 40-70%; in S2, parameters of electrospinning: the distance between the needle and the receiver is 10-50cm, and the voltage between the needle and the receiving end is 0.5-1.5kV cm^-1The spinning temperature range is 20-35 ℃, and the relative humidity is 20-70%.

10. The method as claimed in any one of claims 7 to 9, wherein the pre-oxidation temperature in S3 is 220-300 ℃, and the temperature rise rate is 1-10 ℃ for min^-1The pre-oxidation time is 1-3 h; the carbonization temperature is 800-3000 ℃, and the heating rate is 2-10 ℃ for min^-1The carbonization time is 0.5-5 h.

Technical Field

The invention relates to the technical field of fuel cells, in particular to a gas diffusion layer for a fuel cell and a preparation method thereof.

Background

The fuel cell is a novel green and environment-friendly chemical device, and can directly convert chemical energy of fuel into electric energy. Fuel cells use fuel and oxygen/air as raw materials, with proton exchange membrane fuel cells using hydrogen as the fuel. Proton exchange membrane fuel cells have received extensive research and attention in recent years due to their higher power density and lower operating temperature. The membrane electrode is a core component of a proton exchange membrane battery and is generally prepared by hot pressing a gas diffusion layer, a catalyst layer and a proton exchange membrane.

Gas diffusion layers are typically comprised of a support layer and a microporous layer, and function to support the catalytic layer, conduct current and heat and gases, and drain water. The function of the microporous layer mainly comprises reducing the contact internal resistance of the catalytic layer and the supporting layer, and the compact structure can effectively prevent the catalytic layer from permeating into the supporting layer. The microporous layer may also aid in the transport of water and gases, preventing flooding of the catalytic layer. In general, the gas diffusion layer is required to have good electrical conductivity, thermal conductivity, water-repellency, and gas permeability.

Common support layer materials include conductive porous materials such as carbon paper, carbon cloth, and the like. The traditional microporous layer is generally formed by spraying carbon powder and polytetrafluoroethylene material on the surface of a support layer. Existing commercial gas diffusion layers need to be further optimized for gas and water transport in the stack.

Disclosure of Invention

In view of the above, it is desirable to provide a gas diffusion layer for a fuel cell, which can effectively improve water drainage and gas permeability of the gas diffusion layer, thereby improving power of the fuel cell.

The invention provides a gas diffusion layer for a fuel cell, which comprises a supporting layer and a microporous layer which are arranged in a stacked manner; the supporting layer comprises a plurality of first carbon fiber yarns which are arranged in an oriented and ordered manner, and a plurality of second carbon fiber yarns which are distributed among the first carbon fiber yarns in a crossed manner, wherein the second carbon fiber yarns are used for connecting and supporting the first carbon fiber yarns; the diameters of the first carbon fiber filaments and the second carbon fiber filaments are 1-20 micrometers, and the distance between every two adjacent first carbon fiber filaments is 10-30 micrometers; the microporous layer comprises a plurality of third carbon fiber yarns with the diameter of 50-500nm, the third carbon fiber yarns are mutually stacked to form micropores, and the pore diameter of each micropore is 0.1-1 mu m.

The gas diffusion layer for a fuel cell can effectively improve the permeability of the diffusion layer and improve the air discharge and water discharge. When the supporting layer is used, the supporting layer is arranged perpendicular to the flow channel, so that the accumulation of liquid water under the ribs can be effectively reduced, and the flooding of the fuel cell is relieved; the microporous layer adopts compact electrostatic spinning carbon fibers, can reduce the contact resistance between the catalyst layer and the support layer, and has better transmission performance compared with the traditional carbon powder and hydrophobic particle mixed structure.

In one embodiment, the first carbon fiber filaments occupy 50 to 95% by volume of the support layer.

In one embodiment, the thickness of the support layer is 100-300 μm.

In one embodiment, the microporous layer has a thickness of 10-50 μm.

In one embodiment, the contact angle of the support layer is 100-170 °. The contact angle of the support layer is the contact angle of water on the support layer.

In one embodiment, the microporous layer has a contact angle of 100-. The contact angle of the microporous layer is the contact angle of water on the microporous layer.

The invention also provides a preparation method of the gas diffusion layer for the fuel cell, which comprises the following steps:

s1, preparing a spinning solution with the mass concentration of 10-15 wt% from a high molecular polymer, adding a water repellent, uniformly mixing, and performing electrostatic spinning to obtain a supporting layer;

s2, preparing a spinning solution with the mass concentration of 5-10 wt% from a high molecular polymer, and performing electrostatic spinning on one side of a supporting layer to obtain a composite fiber membrane with the supporting layer and a microporous layer integrated; or

Preparing a high molecular polymer into spinning solution with the mass concentration of 5-10 wt%, performing electrostatic spinning to form a microporous layer, and overlapping one side surface of the supporting layer and one side surface of the microporous layer to form a composite fiber membrane;

s3, pre-oxidizing and carbonizing the composite fiber membrane to obtain the gas diffusion layer.

In the preparation method, the water repellent is added in the preparation process of the supporting layer, so that the hydrophobicity of the supporting layer can be improved, the removal of water generated by the fuel cell is facilitated, and the flooding of the cell is relieved.

In one embodiment, the high molecular weight polymer is selected from: polyacrylonitrile, pitch, lignin, polyimide, polyvinylidene fluoride, polyvinyl alcohol, polyvinyl pyrrolidone.

In one embodiment, the water repellent is selected from: one or more of polytetrafluoroethylene, fluorinated ethylene propylene, polydimethylsiloxane and polyvinylidene fluoride. The addition amount of the water repellent is 5-20% of the mass of the spinning solution.

In one embodiment, the solvent for formulating the dope is selected from: polyacrylonitrile, dimethylformamide and water.

In one embodiment, in S1, the parameters of electrospinning are: the diameter of the needle is 0.2-2mm, and the advancing speed of the spinning solution is 0.5-2mL h^-1The distance between the needle and the receiver is 10-50cm, the rotating speed of the receiving end rotating wheel is 100-1000rpm, and the voltage between the needle and the receiving end is 0.5-1.5kV cm^-1The temperature is 20-35 ℃, and the relative humidity is 40-70%.

In one embodiment, in S2, the parameters of electrospinning are: the distance between the needle and the receiver is 10-50cm, and the voltage between the needle and the receiving end is 0.5-1.5kV cm^-1The spinning temperature range is 20-35 ℃, and the relative humidity is 20-70%.

The third carbon fiber filaments in the microporous layer may be partially distributed in an oriented manner (i.e., a portion of the third carbon fiber filaments are distributed in an oriented manner, and another portion of the third carbon fiber filaments are distributed in a crossed manner), or may be distributed in a disordered manner. Under the condition that the rotating speed of the rotary wheel is higher in the electrostatic spinning process, such as 500-1000rpm, ordered fiber yarns with a certain proportion can be formed, so that an ordered microporous layer structure is formed; when the rotating wheel speed is low, such as below 100rpm, disordered fiber yarns are obtained.

In one embodiment, in the S3, the pre-oxidation temperature is 220-300 ℃, and the temperature rise rate is 1-10 ℃ for min^-1The pre-oxidation time is 1-3 h; the carbonization temperature is 800-3000 ℃, and the heating rate is 2-10 ℃ for min^-1The carbonization time is 0.5-5 h.

In one embodiment, the carbonization process is carried out in an inert gas atmosphere selected from the group consisting of: argon, nitrogen or a mixed gas of argon and hydrogen (the mass fraction of hydrogen in the mixed gas is less than or equal to 10 percent).

In one embodiment, the method further comprises the following steps: and (3) immersing the gas diffusion layer into a water repellent agent, taking out, drying and sintering in vacuum to obtain the hydrophobized gas diffusion layer.

In one embodiment, the hydrophobization step is specifically: and (3) immersing the gas diffusion layer into a water repellent, taking out, drying at 120 ℃ for 1h, and then sintering at 350 ℃ for 1h in vacuum to obtain the hydrophobized gas diffusion layer. Preferably, the water repellent is a Polytetrafluoroethylene (PTFE) emulsion.

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

the gas diffusion layer for the fuel cell can effectively improve the permeability of the diffusion layer and improve the air permeability and the water drainage; the supporting layer is arranged perpendicular to the flow channel, so that the accumulation of liquid water under the ribs can be effectively reduced, and the flooding of the fuel cell is relieved; the microporous layer adopts compact electrostatic spinning carbon fibers, so that the contact resistance between the catalyst layer and the support layer can be reduced, and the transmission performance is improved.

Drawings

Fig. 1 is a schematic view of the structure of a gas diffusion layer in an example.

Fig. 2 is a schematic diagram illustrating the operation of the gas diffusion layers according to the embodiment.

FIG. 3 is an electron micrograph of the support layer in the example.

In the figure, 10, gas channels, 11, gas inlets, 12, gas outlets, 20, bipolar plates, 30, support layers, 40, microporous layers.

Detailed Description

To facilitate an understanding of the invention, a more complete description of the invention will be given below in terms of preferred embodiments. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Example 1

A gas diffusion layer, as shown in fig. 1, comprising a support layer and a microporous layer, which are stacked, prepared by the following method:

(1) weighing 3g of Polyacrylonitrile (PAN) and 16g N, N-dimethylformamide, adding 1g of polyvinylidene fluoride (PVDF), uniformly mixing, heating and dissolving in a water bath at 70 ℃ to prepare 15 wt% spinning solution. Taking 15mL of 15 wt% spinning solution, connecting a 15G needle (the inner diameter is 1.40mm), and carrying out electrostatic spinning, wherein the parameters of the electrostatic spinning are as follows: the advancing speed of the spinning solution is 1.0mL h^-1The voltage is 17kV, the distance from the needle head to the receiving end is 17cm, the rotating speed of the receiving rotating wheel is 500rpm, the ambient temperature is 25 ℃, the relative humidity is 55%, and the spinning time is 10 h. Spinning was completed to obtain a support layer having a thickness of 200 μm. The supporting layer comprises first carbon fiber filaments which are arranged in an oriented and ordered manner and a few second carbon fiber filaments which are distributed among the first carbon fiber filaments in a crossed manner (as shown in figure 3), the second carbon fiber filaments are used for connecting and supporting the first carbon fiber filaments, and the proportion of the first carbon fiber filaments to the second carbon fiber filaments is about 8: 2. the first carbon fiber filaments and the second carbon fiber filaments have a diameter of about 7 μm. The distance between two adjacent first carbon fiber filaments is about 50 μm. The contact angle of water on the support layer was tested to be 130 °.

(2) Weighing 1g of polyacrylonitrile and 19g N, N-dimethylformamide, uniformly mixing, heating and dissolving in a water bath at 70 ℃ to prepare 5 wt% spinning solution. Taking 10mL of 5 wt% spinning solution, connecting a 20G needle (the inner diameter is 0.60mm), and performing electrostatic spinning on one side surface of the supporting layer, wherein the parameters of the electrostatic spinning are as follows: the advancing speed of the spinning solution is 1.0mL h^-1The voltage is 17kV, the distance from the needle head to the receiving end is 20cm, the rotating speed of the receiving rotating wheel is 100rpm, the ambient temperature is 25 ℃, the relative humidity is 40%, and the spinning time is 10 h. And spinning is completed to obtain a microporous layer with the thickness of 20 mu m, and the microporous layer and the supporting layer form an integrated composite fiber membrane. Compared with the microporous layer, the microporous layer is relatively compact and is formed by stacking disordered third carbon fiber yarns, a plurality of micropores are formed on the surface of the microporous layer, the diameter of each third carbon fiber yarn is about 100nm, and the pore diameter of each micropore is about 1 mu m. The contact angle of water on the support layer was tested to be 120 °.

(3) Placing the composite fiber membrane in a muffle furnace, and heating at a rate of 1 deg.C for min^-1And raising the temperature to 250 ℃ for pre-oxidation for 2 h.

(4) Carbonizing in nitrogen atmosphere at a heating rate of 5 deg.C for min^-1And heating to 1500 ℃ for carbonization for 1 h.

(5) And (3) immersing the gas diffusion layer into polytetrafluoroethylene emulsion, taking out the gas diffusion layer, drying the gas diffusion layer for 1h at 120 ℃, sintering the gas diffusion layer for 1h at 350 ℃, and naturally cooling the gas diffusion layer to room temperature to obtain the gas diffusion layer.

Comparative example 1

Conventional carbon paper gas diffusion layers.

Experimental example 1

The gas diffusion layers of the examples and comparative examples were installed in the fuel cell, respectively, with the first carbon fiber filaments of the support layer perpendicular to the flow channels (see fig. 1). And (3) carrying out performance test on each fuel cell under the same condition, wherein the test conditions are as follows: humidity 80%, temperature 70 ℃, hydrogen and air side metering ratios of 1.5 and 2.5, respectively, and back pressure 1 atm.

The test results are: the power of the fuel cell corresponding to the gas diffusion layer of example 1 was 1.3W cm^-2@2A cm^-2Comparative example 1, the conventional carbon paper gas diffusion layer corresponds to a fuel cell power of 1.2W cm^-2@2A cm^-2. Compared with the traditional carbon paper gas diffusion layer, the gas diffusion layer of the embodiment 1 has the power improved by about 0.1W cm^-2@2A cm^-2. The working principle of the gas diffusion layer of the present invention in a dye cell is shown in fig. 2.

The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.