Revealing the critical role of low voltage excursions in enhancing PEM fuel cell catalyst degradation by automotive hydrogen/air potential cycling experiments

The durability of Polymer Electrolyte Membrane Fuel Cells under dynamic operation still needs to be improved. To understand the automotive voltage cycling-induced catalyst degradation, the loss of the electrochemically active surface area (ECSA) is investigated through an experimental campaign on Membrane Electrode Assemblies. Ad-hoc hydrogen/air accelerated protocols were designed to evaluate the voltage profile impact in a range relevant for both automotive and heavy duty transport application (<0.90 V). Besides the well-known aging dependence on the upper potential limit, this work evidences the critical role of the short-stops, characterized by low voltage transients. Effort was spent in studying this procedure parameters (voltage level, duration, scan rate, humidification). The accelerated ECSA loss is due to Pt nanoparticles coarsening as proved by transmission electron microscopy and is suspected dominated by Pt cathodic dissolution, incentivized during excursions towards very low potentials (<0.4 V). These findings help the development of system mitigation strategies.