Effect of Through-Plane Polytetrafluoroethylene Distribution in a Gas Diffusion Layer On a Polymer Electrolyte Unitized Reversible Fuel Cell

This study is an investigation into the relationship between through-plan polytetrafluoroethylene (PTFE) distribution on a gas diffusion layer (GDL) and unitized reversible fuel cell (URFC) performance. Titanium (Ti) -felt was used for the oxygen-side GDL and treated with 10wt.% PTFE dispersion to enhance hydrophobicity. The PTFE distribution dependence on the PTFE drying conditions was examined using scanning electron microscopy (SEM)-based energy dispersive X-ray spectroscopy (EDS) imaging. The EDS image maps revealed that the PTFE distribution strongly depended on the drying condition of the PTFE; drying under atmospheric pressure yielded a highly heterogeneous PTFE distribution in the through-plane direction, whereas drying under vacuum pressure yielded a relatively uniform PTFE distribution. The cell performance of URFC was then evaluated based on measured current-voltage characteristics during both electrolysis and fuel cell operation modes. Results verified that compared with non-uniform distribution, a uniform PTFE distribution in the Ti-felt GDL improved the fuel cell performance.