Effect of polytetrafluoroethylene distribution in the gas diffusion layer on water flooding in proton exchange membrane fuel cells

The effect of polytetrafluoroethylene (PTFE) distribution in the gas diffusion layer on water flooding in proton exchange membrane fuel cells was investigated. PTFE was introduced within micropores of carbon papers, to achieve hydrophobicity under different pressures. Carbon papers were subjected to vacuum conditions during immersion in PTFE solution to prepare gas diffusion layers. Residual gas within the carbon papers was eliminated, and PTFE evenly infused within the pores. Cross-sections of the carbon papers indicated that vacuum treatment improved PTFE distribution. The same PTFE content resulted in a decreased water contact angle of the carbon paper because of the greater PTFE content within the micropores. The proportions of hydrophobic and hydrophilic pores within the carbon papers were investigated. The proportion of hydrophobic pores increased during the vacuum treatment. Membrane electrode assemblies (MEAs) were fabricated using the treated hydrophobic carbon papers as gas diffusion layers and were evaluated in a full-sized fuel cell. The uniform PTFE distribution of the carbon paper benefited fuel performance. Electrochemical impedance spectroscopy indicated that the improved MEA possessed favorable resistance to water flooding.