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 H₂/N₂ (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 H₂/O₂ and H₂/air performance, the oxygen reduction reaction activity, and the H⁺/O₂ transport resistances. The BoL H₂/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 H₂/air performance correlates quantitatively with the cathode rf, so that a 4-fold increase in Pt cathode loading yields a ∼21-fold improved H₂/air performance retention.