Synergistic localized interface engineering alleviating PGM-based catalyst from sulfonate poisoning in fuel cells via balanced adsorption modulation

The performance of proton-exchange-membrane fuel cell (PEMFC) is known to be highly restrained by the nano-micro-scale ionomer-catalyst interface structure. The commonly used ionomers in the catalyst layer are functionalized by forming a nanoscale network with platinum-group-metal (PGM) based catalyst. The imbalanced binding strengths of sulfonate groups to the PGM surface compared to the carbon support surface lead to the favorable occupation of active sites for oxygen reduction reaction (ORR) and the declining performances in membrane electrode assembly (MEA). In this work, by employing a dual strategy on PGM and carbon support, a catalyst/support design is proposed to significantly reduce the variance in adsorption energies of sulfonate to the PGM and carbon surface. The balanced adsorption of sulfonate groups enables a more uniform distribution of ionomer on the catalyst surface with enhanced catalytic activity. The PtCo/CNH-N catalyst not only achieves a power density far exceeding that of its counterpart in MEA but also exhibits high stability against ionomer poisoning throughout potential cycling. Combining experimental evidence and theoretical calculation, this work corroborates the essential role of balanced binding strengths of sulfonate groups to PGM and carbon surface, and provides insight into the ionomer poisoning issue towards the design of a highly stable catalyst for PEMFC.