A kind of conductive gas diffusion layer of fuel cell and its preparation method

Abstract

The invention provides a fuel cell conductive gas diffusion layer and a preparation method thereof. The diffusion layer includes a porous conductive substrate, and a conductive porous microporous layer attached to at least one side of the porous conductive substrate, and the porous conductive substrate is a carbon fiber fabric. , carbon paper or carbon cloth; the carbon fiber fabric is woven or non-woven. This method realizes the uniform distribution of the electronically conductive material and the hydrophobic polymer binder in the microporous layer on the micro-nano scale, avoids the local agglomeration and phase separation of the two, and the micro-porous layer of the prepared gas diffusion layer has a micro- and nano-scale The upper composition and structure are precise and controllable, and can be designed arbitrarily to meet the functional requirements of gas-liquid transmission in the gas diffusion layer, and to avoid liquid flooding during the discharge process of the fuel cell.

Description

technical field [0001] The invention relates to the field of electrochemistry, in particular to a gas diffusion layer, a preparation method thereof and a fuel cell. Background technique [0002] A fuel cell is an electrochemical reaction device that directly converts the chemical energy of fuel molecules into electrical energy. It has many advantages such as high energy efficiency and low environmental pollution. Compared with other types of fuel cells, the anode reaction of proton exchange membrane fuel is the oxidation reaction of hydrogen, the cathode is the reduction reaction of oxygen, and the discharge product is water. It is a kind of clean energy and is expected to be used in vehicle power, military equipment, mobile and portable energy equipment been widely applied. [0003] Membrane electrode is the core component of proton exchange membrane fuel cell, mainly composed of solid proton exchange membrane, catalytic layer and gas diffusion layer. Among them, the poro...

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Problems solved by technology

However, the structure and technology of the existing gas diffusion layer are formed by directly coating the mixture slurry prepared by mechanically mixing PTFE resin and conductive carbon powder on the surface of the support layer. , surface physical properties, solubility, etc., the conductive carbon powder and the polymer binder in the microporous layer prepared by the above slurry are easy to agglomerate and separate phases, resulting in a large number of cracks and large cracks on the surface of the microporous layer. The pore structure and large surface roughness will cause uneven condensation and coalescence of liquid water, causing the electrode to be flooded; at the same time, it will also cause waste of catalyst (catalysts buried in the cracks of the microporous layer are mostly ineffective), and micro The large surface roughness of the pore layer will also induce roughness on the surface of the catalytic layer, which will damage the electrolyte membrane when the electrode is hot-pressed, resulting in cross-leakage of the membrane electrode

[0005] In order to improve the uniformity of the pore structure of the microporous layer and its surface roughness, Patent Document 1 (Japanese Patent Application Laid-Open No. 2015-79639) proposes a gas diffusion electrode preparation technology. A microporous layer is formed on the surface, and then stamped to reduce its surface roughness, but the pore structure of the microporous layer is easily damaged during the stamping process, which reduces the diffusion performance of the reaction gas and affects the discharge performance of the battery; the Chinese invention patent CN107851805 builds a double Microporous layer strategy to improve the surface roughness of the gas diffusion layer, wherein the main component of the first microporous layer in contact with the conductive base layer is conductive carbon spheres, and the second microporous layer has a linear structure of conductive material (linear conductive The aspect ratio of the material is 30-5000)

The above scheme is either through the molding process of the gas diffusion layer, or through the adjustment of the structure of the gas diffusion layer, the microporous layer is changed from a single layer to a multi-layer, which reduces the surface roughness of the microporous layer, and lacks the main function of the microporous layer. In terms of the adjustment of the composition / structure of the micro-area, we start to strengthen the regulation of the macroscopic pore structure and roughness of the microporous layer. The designability of the gas diffusion layer is low, and it is difficult to combine the theoretical simulation technology of material transfer for calculation and optimal design.

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