Carbon support–dependent activity and durability of intermetallic PtCo@Pt catalysts in practical polymer electrolyte membrane fuel cells

With the increasing demand for highly durable electrocatalysts for long-lifetime fuel cells, intermetallic alloy catalysts with small and uniform particle sizes have attracted considerable attention. Herein, intermetallic PtCo@Pt catalysts derived from approximately 2 nm Co@Pt nanoparticles were systematically investigated to elucidate the influence of carbon support structure on intermetallic phase formation and oxygen reduction reaction (ORR) activity. Solid carbon (SC) and porous carbon (PC) supports were employed to distinguish support-dependent effects on nanoparticle growth, distribution, and chemical ordering. After intermetallic transformation, both catalysts retained particle sizes of approximately 3–4 nm. In half-cell measurements, the PtCo@Pt/SC catalyst exhibited a higher current at 0.9 V (0.84 A mg −1 Pt ) than PtCo@Pt/PC (0.64 A mg −1 Pt ) and commercial Pt/C (0.29 A mg −1 Pt ). In contrast, the PtCo@Pt/PC catalyst delivered a higher current density of 0.358 A cm −2 at 0.8 V under membrane electrode assembly (MEA) conditions, outperforming PtCo@Pt/SC (0.204 A cm −2 ) and Pt/C (0.192 A cm −2 ). Notably, the trends observed in half-cell measurements differed from those in single-cell performance, indicating that catalyst performance is governed not only by catalytic activity but also by electrode-level factors such as carbon pore structure, ionomer distribution, and mass transport characteristics. These findings highlight the critical role of carbon support architecture in catalyst and electrode design for polymer electrolyte membrane fuel cells.