Boosting the Voltage Cycling Durability of Proton Exchange Membrane Fuel Cell via Increasing the Cathode Electrode Roughness Factor

Load cycling compromises the durability of proton exchange membrane fuel cells (PEMFCs), leading to a loss of the electrochemically active surface area ( ECSA ) of platinum in the cathode electrode. This study investigates the impact of cathode Pt loading (∼0.2–0.8 mg Pt cm MEA − 2 ) on the degradation rate during voltage cycling accelerated stress tests (ASTs) under H 2 /N 2 (anode/cathode), whereby the cathode electrodes were prepared with the same catalyst and thus vary ∼4-fold in thickness. An analysis of the voltage loss terms was performed at beginning-of-life (BoL) and over the course of the AST, monitoring the evolution of the cathode ECSA and roughness factor ( rf ) as well as the evolution of the differential-flow H 2 /O 2 and H 2 /air performance, the oxygen reduction reaction activity, and the H + /O 2 transport resistances. The BoL H 2 /air performance at 95 and 70% relative humidity increases with Pt loading and electrode thickness, indicating that the increased proton conduction resistance is negligible compared to the decrease of the local oxygen transport resistance term. Furthermore, over the course of the voltage cycling AST, the H 2 /air performance correlates quantitatively with the cathode rf , so that a 4-fold increase in Pt cathode loading yields a ∼21-fold improved H 2 /air performance retention.