Failure behavior of gas diffusion layer in proton exchange membrane fuel cells

Past studies exhibit that the performance constancy of proton exchange membrane fuel cells relate to the multiphase transport of mass, heat, and electricity in the cell, a critical of which is the gas diffusion layer. However, there is little effort devote to the gas diffusion layer degradation mechanism in a real fuel cell stack. In this study, the degradation mechanism of a commercial gas diffusion layer is investigated after the durability test of a 1 kW fuel cell stack. The results confirm that the degradation of the gas diffusion layer makes a great contribution to the membrane electrode assembly regression. The dissolution of non-graphitized carbon and polytetrafluoroethylene leads to structural damage and hydrophobicity loss of microporous substrate. In addition, the strength decay behavior of carbon fiber is detected. These degradations lead to the loss of support capability and hydrophobicity of gas diffusion layer. The combined effect of these factors leads to a decrease in the effective gas transfer path of the gas diffusion layer under high current density, which leads to a decline in fuel cell performance. This study provides an essential basis for the design of a high-durability gas diffusion layer for proton exchange membrane fuel cells.