The Research Of Carbon Fiber Paper Used For Gas Diffusion Layer In Fuel Cell

Proton exchange membrane fuel cell (PEMFC) is the potential clean energy in future, and it has become the focus in fuel cell field. Gas diffusion layer (GDL) is a very important component in PEMFC, which backs up the catalyst layer, provides passage for reactant gas and water generated from fuel cell, and transmits electrical energy. Carbon fiber paper is widely used as GDL substrate. Some foreign companies have produced carbon fiber paper with high performances for commercial use. Although our country can produce carbon fiber paper, its performances are not good enough to use in PEMFC. Carbon fiber paper has become one of the obstacles for PEMFC development.This paper has developed three ways to produce carbon fiber paper by carbon fiber felt made in our country for solving this problem. The two-dipping process is the best way to produce carbon fiber paper, which proved by many experiments, and its process parameters in every step have been confirmed ether. For researching the microstructure of carbon fiber paper, this paper used fractal dimension to illustrate the microstructure constructed by short-cut carbon fiber, resin carbon and pore quantificationally. According to the fractal dimension, the microstructure of carbon fiber paper can be studied more easily and the process could be improved more valid. The achievements of this research are following:The best ratio of shout-cut carbon fiber and resin carbon was 1:0.7 in carbon fiber paper through experiments. The parameters of molding process are: molding pressure, l-3MPa; molding temperature, 140-170℃; curing time, 20-30min. The pretreatment dipping-carbonization process is the best way to manufacture high performance carbon fiber paper and the performances of carbon fiber paper produced by this process are: thickness, 0.30mm; density, 0.42g/cm³, porosity, 77%; gas permeability, 2800 mL·mm/(cm²Â·hr·mmAq), and tensile strength, 18MPa. The surface of CNTs is decorated by mixed acid( H₂SO₄ / HNO₄ = 3:1). The decorated CNTs can be dispersed well in the phenolic resin solution. The performances of carbon fiber paper added decorated CNTs are: thickness, 0.30mm, density, 0.42g/cm³, porosity, 77%, gas permeability, 2400 mL·mm/(cm²Â·hr·mmAq), and tensile strength, 13MPa. Fractal dimension is used to characterize the carbon fiber paper microstructure. The comparisons of fractal dimensions between self-made and Toray carbon fiber paper show that the fractal dimension of self-made carbon fiber paper is close to Toray's, while the fractal dimension of pore is a little higher.