Evolution and distribution of the anode overpotential and its oscillations in a polymer electrolyte membrane fuel cell exposed to carbon monoxide

Abstract

Carbon monoxide (CO) poisoning of polymer electrolyte membrane fuel cells (PEMFCs) remains a challenge for their deployment, and a deeper understanding of the spatiotemporal dynamics involved is needed to develop effective mitigation strategies. In this work, localised reference electrodes were used to measure the anode overpotential at three locations across the active area of a galvanostatically operated cell (0.3 A cm−2) exposed to 100 ppm CO/H2. The anode region closest to the inlet was poisoned more rapidly than the rest of the cell, following a sigmoidal variation, and presented a higher CO coverage. The varying CO concentration, combined with local operating conditions, had a direct impact on the distribution of CO coverage. Additionally, complex self-sustained oscillations of the cell voltage and the anode overpotential were observed and correlated with the rate of CO oxidation in the overall cell. The coexistence of a dominant mean-field coupling area closer to the anode inlet, and a dominant migration coupling region closer to the outlet was identified, consistent with reported modelling predictions for a single straight channel cell. Finally, the cell recovery with pure H2 was shown to be a faster process than the CO adsorption, which follows first-order kinetics and is affected by local conditions.