Resolving mass transport losses at the catalyst layer of polymer electrolyte membrane fuel cells through semi-empirical modelling

Abstract

In this study, the sources of oxygen transport resistance in a polymer electrolyte membrane (PEM) fuel cell are resolved using two different approaches: pore network modelling and empirical modelling. This is achieved by applying operando imaging and electrochemical performance testing results to the pore network model and empirical model, respectively. In the literature, the impact of liquid water on oxygen transport resistance in a 5-layer membrane electrode assembly is typically attributed to the accumulation of liquid water within the gas diffusion layer. A comparison of the oxygen transport resistance values predicted by pore network modelling to the values predicted by empirical modelling shows that empirical models significantly overpredict the contribution of the substrate within gas diffusion layers to oxygen transport resistance at limiting current conditions (up to 440%). Statistical analysis of the discrepancy (residual) between the values of the oxygen transport resistance of the substrate predicted by the empirical and pore network models indicates that the residual can be attributed to oxygen transport resistance in locations that are related to water production but independent of the relative humidity of the inlet: the catalyst layer (CL) and/or CL-microporous layer interface.