Dependence of PEM fuel cell performance on catalyst loading

This study focuses on a determination of the cell voltage losses observed for Pt and PtRu loading reductions in H₂/air and reformate/air polymer/electrolyte-membrane fuel cells (PEMFC). Experiments with catalyst-coated membranes (CCM) of varying anode and cathode catalyst loadings with H₂/O₂ and H₂/air demonstrate that the anode catalyst loading in state-of-the-art membrane electrode assemblies (MEAs) operating on pure H₂ can be reduced to 0.05 mg_Pt/cm ² without significant voltage losses, while the cell voltage losses upon a reduction of the cathode catalyst loading from 0.40 to 0.20 mg _Pt/cm² for optimized MEAs amounts to 10-20mV, consistent with purely kinetic losses due to the oxygen reduction reaction. It is shown that H₂/air operation with state-of-the-art MEAs very closely approaches the Pt-specific power density (in units of g_Pt/kW) for large-scale automotive fuel cell applications with pure H₂ feed. For reformate/air operation, PtRu anode loadings can be reduced to 0.20 mg _PtRu/cm² for reformate containing 100 ppm CO with a 2% air-bleed. Any further reduction will, however, require either a change in operating conditions (i.e. lower CO concentration or cell temperature ≫80°C) or novel, more CO-tolerant anode catalysts.