Mechanistic investigation on the voltage collapse of polymer electrolyte membrane fuel cell under high-temperature and low-humidity conditions

Abstract

Polymer electrolyte membrane fuel cell (PEMFC) operating under high-temperature and low-humidity (HTLH) conditions enables more efficient and compact fuel cell system through smaller radiators (less parasitic power) and smaller humidifier, but exerts negative influence on conductivity of perfluorosulfonic acid (PFSA) membrane, which is the most commercial proton conductor for PEMFC at current state. Although great progress has been made on the R&D of advanced PFSA-based material, a huge gap from material to PEMFC still exists due to its complicated physico-chemical processes. In this work, after a slight rise of operation temperature, we observe the unexpected voltage collapse of PEMFC under HTLH conditions and non-active zone (nearly zero local current density) is found to fast propagate from air inlet to the rest area during this period. For the first time, temporal–spatial numerical reconstruction of this dynamic process reveals that the current in-plane redistribution raises the local mass transfer losses but make limited contribution. Instead, the water being transferred from anode to cathode due to proton's dragging effect leads to severe anode ionomer dehydration, dominating such process. Finally, suggestions are provided as following: (a) raising membrane conductivity under dry condition or reducing proton's dragging coefficient could significantly improve PEMFC's performance under HTLH condition; (b) particular attention should be paid to the water content of anode ionomer for PEMFC design and system control.