Transport Resistances in Fuel-Cell Catalyst Layers

Mass-transport resistances observed with low platinum (Pt) loadings in polymer-electrolyte fuel-cell (PEFC) catalyst layers (CLs) limit performance and thus, present challenges for necessary further Pt reduction to enable commercialization. It is believed that this resistance is due to mass-transport resistance near the Pt surface, probably due to transport through the ionomer thin-film layer on the Pt/C particles; the nature and genesis of this resistance needs to be explored further. In this study, a hydrogen-pump configuration operated at limiting-current is used to study local mass-transport limitations in CLs. Using an agglomerate model, analytical expressions for the total resistance at limiting current are developed to identify critical parameters controlling this resistance. The dependence of CL resistance on these parameters is examined.