Effect of applying pressure during carbonization process on structure and properties of carbon paper for gas diffusion layer

Carbon paper is one of the most commonly used materials for the gas diffusion layer of proton exchange membrane fuel cell, and its performance is the premise to ensure the stable operation of the cell. In order to improve the structure and properties of carbon paper and make it better meet the performance requirements of fuel cell, this study was conducted to press different amounts of graphite plates in the carbonization process to control the applied pressure and analyze the microstructure evolution and mechanism of carbon paper under different pressure. In addition, the effects of applied pressure on the in-plane resistivity, pore size distribution, surface roughness and mechanical properties of carbon paper were also studied. The results show that applying pressure helps to restrain the cracking of resin carbon, reduce the generation of cracks and improve graphitization degree of carbon paper to a certain extent. Furthermore, with the increase of applied pressure, the surface roughness of carbon paper is reduced gradually, while the average and maximum apertures also decrease. When the applied pressure reaches 3600 Pa, compared with the samples without pressure, the in-plane resistivity of carbon paper decreases from 17.15 mΩ·cm to 12.79 mΩ·cm, the tensile strength and flexural strength are improved by 150% and 82.9% respectively.