Impact of the OER Activity and Stability of IrO 2 Anode Co–Catalysts on the Durability of Membrane Electrode Assemblies under Transient Operation Conditions of a PEM Fuel Cell

IrO 2 is widely used as an anode co–catalyst in proton exchange membrane fuel cells (PEMFCs) to mitigate cell reversal (CR) induced damages. In this study, two types of IrO 2 anode co–catalysts with different reduction resistances in H 2 atmosphere are implemented into membrane electrode assemblies (MEAs) and subjected to accelerated stress tests (ASTs), combining start–up/shut–down (SUSD) and CR cycles within two protocols. Protocol 1 starts with a segment of SUSD cycles followed by a segment of CR cycles, while Protocol 2 combines SUSD and CR cycles within the same segments. Although Protocol 1 helps to isolate the performance losses induced by SUSD and CR cycles, Protocol 2 introduces a more realistic testing scenario and captures the complex interplay of concurrent degradation mechanisms. The results of Protocol 2 show that the detrimental impact of iridium dissolution from the reducible anode co–catalyst outweighs the benefit of its higher OER activity at the early stages of the AST, while the advantage of its higher OER activity becomes apparent in the later stages of the AST. This study shows that OER activity and reduction resistance are critical for benchmarking anode OER co–catalysts, with the optimal balance dictated by system–specific operating conditions.