Carbon-shell on PtCo for mitigating hydrocarbon poisoning toward efficient electrochemical oxygen reduction

Polyfluoroalkyl substances (PFAS) regulations are accelerating the transition of proton-exchange-membrane fuel cells (PEMFCs) toward PFAS-free hydrocarbon electrolytes. However, aromatic fragments leached from these membranes during PEMFC operation can poison Pt-based oxygen reduction reaction catalysts, undermining activity and durability. Here we report a poisoning-tolerant intermetallic PtCo catalyst protected by an ultrathin carbon overlayer. Carbon-coated intermetallic PtCo nanoparticles are obtained via oleylamine-assisted annealing, forming a few-layer carbon shell. Using benzenesulfonic acid as a representative aromatic contaminant, the carbon-coated intermetallic PtCo preserves onset potential and half-wave potential under poisoning and after 5,000 accelerated durability cycles, whereas Pt/C and uncoated intermetallic PtCo/C exhibit pronounced losses in hydrogen adsorption features and negative shifts in onset potential. These results indicate that the carbon shell substantially suppresses aromatic adsorption and stabilizes Oxygen Reduction Reaction performance, revealing a tunable activity–tolerance trade-off. This protection concept offers a generalizable design rule for PEMFCs employing hydrocarbon membranes and for other electrochemical systems exposed to aromatic species.