Suppressing phosphate poisoning via ionic liquid interface engineering for high-performance high-temperature PEMFCs

High-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) are promising and critical for heavy-duty vehicle applications. Phosphoric acid (PA) is essential for proton conduction at elevated temperatures but strongly adsorbs onto platinum, hindering the oxygen reduction reaction (ORR) and causing significant performance losses. This study explores an ionic liquid (IL) as a surface modifier to mitigate PA adsorption and enhance catalyst performance. Compared to the state-of-the-art, experimental results show notable improvements in catalyst activity on high-temperature rotating disk electrode (HT-RDE) and membrane electrode assembly (MEA) performance. Electrochemical analyses reveal that the ionic liquid effectively minimizes PA interaction with platinum while maintaining active site availability. The optimal ionic liquid-to-carbon (IL/C) ratio was determined, with variations in performance providing insights into the improvement mechanism. Long-term durability test, simulating start-up and shutdown cycles, confirms MEA stability under operational conditions. These findings establish a promising strategy to mitigate PA poisoning, significantly boosting HT-PEMFC performance and advancing the technology toward commercialization. © 2025 Elsevier B.V.