Carbon fiber and graphene compounded high-strength porous material, and gas diffusion layer and preparation method therefor

A gas diffusion layer formed by combining a carbon fiber and graphene, comprising a porous and air-permeable conductive carbon material layer formed by compounding a carbon fiber monofilament with graphene and having a porosity of greater than or equal to 70%;

• wherein the conductive carbon material layer comprises a support layer and a microporous layer on the support layer;
• the support layer comprises a porous material layer formed by compounding the carbon fiber monofilament with large graphene, the large graphene is of 1-5 graphene atomic layers, and single nanosheet graphene has an area greater than 50 square micrometers;
• the carbon fiber monofilament has a diameter of 5-7 micrometers and a length greater than 10 centimeters;
• a method for preparing the gas diffusion layer comprises:
• splitting a tow into filaments by spreading a liquid film to form a liquid film for infiltrating the filaments, wherein the filaments and the filaments form a network infiltrated and covered by the liquid film, and an area of filament-liquid film is enlarged to more than 10 times relative to that of the tow;
• an oxygen-containing hydrophilic functional group on a surface of a carbon fiber filament is compatible with an aqueous solution to form a solid-liquid film, the solid-liquid film has a thickness of 0.5-500 micrometers, and two sides of a film surface of the solid-liquid film are in contact with air;
• a liquid film is formed between the carbon fiber filaments has a viscosity of 1.7-1000 Pa·s;
• the solid-liquid film is expanded by more than 10 times, an area of the liquid film is expanded by receiving a liquid, and a distance between the carbon fiber filaments is synchronously increased along with an expansion of the area of the liquid film;
• a method for preparing the liquid film comprises the following steps:
• (1) preparing a solution, wherein components of the solution comprise polymers, a solvent is water, a total mass percentage concentration of the polymers is 0.1-5%, and the polymers are 1-4 of sodium carboxymethyl cellulose, polyvinyl alcohol, polyacrylic acid, and waterborne polyurethane;
• (2) performing oxidation hydrophilicity of carbon fiber bundles, removing a sizing agent, and then performing heat oxidation or electrochemical oxidation in concentrated nitric acid;
• (3) soaking the carbon fiber bundles in the solution on a water-permeable base film together, so as to infiltrate carbon fiber bundle filaments in the solution;
• and (4) stretching the carbon fiber bundles towards two sides at a controlled speed, supplying the solution to the liquid film, and keeping the area of the liquid film from being broken during an increase.