DURABILITY ISSUES IN PRECIOUS-GROUP-METAL FREE PEMFC CATHODES

Replacement of noble metal catalysts used in oxygen reduction reaction (ORR) is a research goal in the proton membrane fuel cells. In this work, mass transport limiting phenomena in Fe-N-C catalyst layers are studied. A specific methodology, that combines in-situ characterization of performance and modelling activity, is adopted to elucidate the contribution of electronic/ionic transport losses in catalyst layer with controlled properties. CCL impedance spectra, which take into account ORR activation and electron, proton, and oxygen transport losses are simulated. Analysis shows that a regime of mixed ion and electron transport limitations describes correctly the main features of impedance spectra. Degradation is negligible under nitrogen at 0.6V, supporting catalysts materials oxidation or water formation as main reasons for performance loss.