Enhanced activity and durability of high-temperature proton exchange membrane fuel cells enabled by ionic liquid-modified Pt-Ni nanochains

The performance of high-temperature proton exchange membrane fuel cells (HT-PEMFCs) is severely limited by the poisoning effect and low oxygen solubility of the phosphoric acid (PA) electrolyte. To address this, we report an innovative catalyst architecture consisting of one-dimensional hollow PtNi nanochains coated with a functional ionic liquid (IL), termed PtNi@IL/C. This design creates a multifunctional interface that demonstrates exceptional PA tolerance, achieving an oxygen reduction reaction (ORR) half-wave potential of 0.840 V in a PA-containing electrolyte, which is 90 mV higher than commercial Pt/C. The IL coating synergistically enhances performance by suppressing PA adsorption on Pt active sites while simultaneously boosting O2 mass transport through its high oxygen solubility, and providing a highly efficient proton conduction pathway. As a result, a membrane electrode assembly utilizing the PtNi@IL/C catalyst achieves a high peak power density of 521 mW cm−2 at 150 °C. Furthermore, the catalyst exhibits outstanding durability, with a negligible 4 mV activity loss after 5000 electrochemical cycles and only a 2 % power density decay in single-cell tests, significantly outperforming the 14.3 % decay of Pt/C. This stability is attributed to the IL mechanically reinforcing the porous nanochain structure, preventing degradation. This work presents a powerful catalyst-interface engineering strategy for developing next-generation, high-performance fuel cells.