Study on degradation mechanisms of proton exchange membrane fuel cell under CO poisoning

• CO concentration increase from 25 to 100 ppm, cell poison time decrease by 77.3%. • Operating parameters accelerates CO adsorption while enhancing performance. • CO causes MEA degradation with 14.29% ECSA loss and 24.8% loss of the anode CL. • Uneven degradation of MEA relate to CO distribution and exhibit inlet corrosion. Proton exchange membrane fuel cells (PEMFCs) represent a key technology for hydrogen energy utilization, yet their reliance on high-purity hydrogen restricts further advancement. While hydrogen-rich reforming gas can reduce costs, the CO present in such gas poisons the catalyst. A novel treatment method involves creating a mild hydrogen-deficient environment to enable rapid recovery from high-CO poisoning states. This approach utilizes dual-cell cycling to maintain stable operation in CO-containing environments, though research on this method remains limited. This study quantitatively analyzed the effects of CO concentration, back pressure, humidity, and temperature through multifactor experiments. A 100-hour endurance test under periodic purging conditions revealed fundamentally different degradation pathways: CO exposure caused irreversible damage—a 14.29% loss in electrochemically active surface area, a 34.4% increase in charge transfer resistance, severe catalyst agglomeration, platinum particle growth reaching 55.6%, and oxidation significantly concentrated at the anode inlet due to CO concentration gradients. In contrast, hydrogen operation induced only minor degradation primarily attributable to cathode flooding. This study identified the dual effects of operating parameters, elucidated two distinct failure mechanisms, and provided critical insights for developing mitigation strategies, enabling PEMFC to operate continuously using impure hydrogen fuel.