Comparative Analysis of Performance Decline and Anode Degradation in Polymer Electrolyte Membrane Fuel Cells under Fuel Starvation: A Strategy for Electrode Condition Assessment Using Full Electrode Equivalent Circuit Model and Anode-Separated Distribution of Relaxation Times

This work investigates the impact of anode catalyst layer (CL) degradation in Polymer Electrolyte Membrane Fuel Cells (PEMFCs) under fuel starvation using accelerated stress tests (ASTs). Anode cycling ASTs simulate intermittent fuel starvation and reveal that reduced hydrogen oxidation reaction (HOR) kinetics drive predominant anode degradation. Cyclic voltammetry results show a significantly greater decline in electrochemical surface area in the anode CL compared to the cathode, emphasizing the impact of anode degradation on PEMFC performance decay. A rapid decrease in ionic resistance in low-humidity non-faradaic EIS and SEM images of aged MEAs reveals that structural changes in the anode carbon support structure are the primary degradation mechanism after ASTs. The increase in anode CL charge transfer resistance as the AST progresses aligns with anode impedance data fitting results using the Transmission Line Model and cathode impedance data fitting results using the Full Electrode Circuit Model. The distribution of relaxation times analysis on the separated anode circuit from cathode ORR impedance data indicates shifts in relaxation time, representing anode resistance changes. This work advances the understanding of anode degradation mechanisms under fuel starvation and provides insights into developing improved AST protocols and impedance analysis techniques to enhance PEMFC durability and performance.