Gas-dynamic and electro-chemical optimization of catalyst layers in high temperature polymeric electrolyte membrane fuel cells

We investigate the impact of catalyst (Pt) particle distribution on gas dynamics, electro-chemistry and consequently the performance of high temperature polymeric electrolyte membrane (HTPEM) fuel cells. We demonstrate that optimal distribution of catalyst can be used as an effective mitigation strategy for phosphoric acid loss and crossover of reagents through the membrane. First, we recognize that one of the reasons for performance degradation of HTPEM fuel cells originates from the gas dynamic pulling at the interface between the catalyst layer and membrane. Hence, we show that this can be greatly alleviated by choosing a proper catalyst particle distribution within the catalyst layer (CL). A simplified three-dimensional macroscopic model of the membrane electrode assembly (MEA) with catalyst layer made of three or five sublayers with different catalyst loadings, have been developed to analyze the effect of the proposed mitigation strategy on gas dynamics within the catalyst layer and the overall cell performance. This simplified macroscopic model predicts significant reduction (up to 4 times) in pulling using a feasible mitigation strategy, at the cost of only 9% efficiency reduction at high current densities.