Low-Loaded Catalyst Layers For Proton Exchange Membrane Fuel Cell Dynamic Operation Part 2: Modeling Study

Numerous models have been developed to simulate the performance and degradation mechanisms of proton exchange membrane fuel cell (PEMFC) components. The Nernst and Butler-Volmer approaches, in a single-step reaction, often describe the hydrogen oxidation reaction (HOR) and the oxygen reduction reaction (ORR), the latter being of higher complexity as it involves numerous intermediate species. The experimental work and dataset from the first part of this study [1], obtained in differential single-cell (DC) on low-loaded cathode catalyst layers (20 and 100 µg_Pt cm_geo⁻²), have been used to further study the behavior of the cathode Pt/C electrocatalyst. The objective is to introduce a detailed electrocatalytic description in one-dimensional through-thickness models, particularly the Pt surface oxide formation/reduction: the reaction is decomposed into several elementary steps associated with the surface state of Pt, as well as the formation of ‘bulk’ Pt-oxides, formed via the chemical place-exchange reaction under nitrogen (H₂/N₂) and oxygen (H₂/O₂) atmospheres. This electrochemical path was successfully implemented into a complete ORR performance model at the cathode; it provides a more comprehensive description of the physical and electrochemical phenomena involved in low-loaded cathode catalyst layers during non-stationary PEMFC operation, which helps to capture the hysteresis phenomena observed experimentally during polarization curve measurements.