Thickness effects of anode catalyst layer on reversal tolerant performance in proton exchange membrane fuel cell

Abstract

Real-world driving conditions will likely cause hydrogen starvation at the anode chambers of stacks to trigger voltage reversal events, posing a tremendous challenge to the durability of proton exchange membrane fuel cells (PEMFCs). The reversal-tolerant anode (RTA), a material-based solution, that inclusion of oxygen evolution reaction (OER) catalyst into the anode is usually employed to cope with the voltage reversal issue. In this work, we investigate the impact of anode catalyst layer thickness on the voltage reversal performance of the membrane-electrode assemblies (MEAs) with conventional anodes (Pt/C catalyst) and RTAs doped with IrO2 catalyst, a representative OER catalyst. We find that regardless of how thick the anode catalyst layer is, the conventional MEAs exhibit almost similar voltage reversal behaviors and times, only about 1 min to reach the shutdown voltage (−2.5 V). As for the RTA MEAs, a surprising thickness effect that the thinner RTA with the same IrO2 loading shows superior voltage reversal tolerance. Notably, an ultra-thin RTA (~2 μm) exhibits the reversal tolerance time of 310 min, which is five times higher reversal tolerance time than most of the reported RTAs. We conclude that this thickness effect mainly results from the ionomer distribution on the OER catalyst. Besides, we observe that the RTA with a higher ionomer content shows the better reversal tolerance performance. Our work highlights the importance of the OER Triple-Phase-Boundary (TPB) and the need for improved electrode designs for robust RTAs.