Repetitive hot-press approach for performance enhancement of hydrogen fuel cells

For Nafion 212-based PEM fuel cells assembled with gas diffusion electrodes, two stage hot-press with conditioning or hydration between presses was found to improve performance and to allow the cell to sustain higher current densities. Testing refuted additional time as a driving factor for increased performance and the optimal hot-press time of 3 min from literature is confirmed. The two-stage hot-press process is shown to decrease ohmic resistance and to increase performance by a greater factor for Nafion 212 than Nafion 115. Tafel plots are constructed to focus on kinetics and give insight into the behavior of each membrane. Gains from hot-press and sequential hot-pressings are shown to be largely due to the suppression of kinetic overpotential. A correlation between water content and fuel cell performance in hot-press processes indicates that excessive hot-press limits the water content of a membrane, lending further support to an existence of an optimal hot-press time.