Evaluation of PEM Fuel Cell Degradation Through Accelerated Stress Tests to Investigate Heterogeneity of Ageing

Studying polymer electrolyte membrane fuel cell (PEMFC) degradation under real-world operating conditions is crucial to both improve the materials durability and overcome the lack of representativeness of the standardized accelerated stress tests (AST) traditionally adopted to investigate material ageing. Works that perform real-world durability tests showed a heterogeneous PEMFC degradation, with differences that arise mainly in the in-plane direction that follows the reactants path along the flow-field channel, from the inlet towards outlet section. This work investigates ageing of three state-of-art PEMFC with an innovative approach: an effective AST protocol representative of real automotive ageing was conducted on different samples and AST operating conditions were properly tuned to reproduce the behavior of specific sections of cathode channel (inlet, middle and outlet). Loss of catalyst active area (ECSA) appeared to be the prevalent degradation process, with the outlet AST resulting in the highest ECSA reduction. AST performed under dry conditions, typical of cathode inlet section, resulted in a higher oxygen transport resistance increase and in cracks formation within the cathode catalyst layer. Air inlet and outlet appeared to be the most critical sections and the methodology presented allows dedicated analyses devoted to improve materials durability.