Evaluating liquid-water generation in catalyst layers of polymer electrolyte fuel cells based on adsorption isotherm measurements and lattice density functional theory calculations

Abstract

The power generation performance of polymer electrolyte fuel cells is known to be greatly deteriorated by the reduction in oxygen diffusivity caused by capillary condensation of water vapor in catalyst layers. In this study, we investigated the effect of lattice density functional theory (L-DFT) calculation parameters on the adsorption/desorption behavior by comparison with experimentally obtained sorption isotherms. In the sorption isotherm measurements, humidity-controlled gas was introduced into a catalyst layer, and the mass of adsorbed water was measured with a magnet suspension balance. Then, L-DFT calculations were performed using realistic structural data reconstructed from continuous cross-sectional images of the catalyst layer to investigate the effect of L-DFT wettability parameters. We found that optimization of the model parameters and consideration of the wettability of ionomer were required to better reproduce capillary phenomena in the catalyst layer using L-DFT calculations.