High-Loading Intermetallic Pt₃Co/C Core–Shell Nanoparticles as Enhanced Activity Electrocatalysts toward the Oxygen Reduction Reaction (ORR)

A facile, seed-mediated growth method and postannealing treatment have been employed to synthesize a single-phase 40% mass loading intermetallic Pt₃Co/Vulcan electrocatalyst, enabling the electrocatalytic layer to be thinner and thus lowering the mass transport resistance for the ORR in proton exchange membrane fuel cells (PEMFCs). These 40% Pt₃Co/C nanocatalysts exhibited superior kinetics toward the ORR, relative to a 20% Pt₃Co/C catalyst, and only showed a slight degradation in the half-wave potential and electrochemical surface area after a 4000-cycle stability test. The high activity and stability are attributed to a stable intermetallic Pt3Co core with a Pt shell two to three atomic layers thick, as well as to its good dispersion on the support. This seed-mediated growth approach and postannealing treatment provide a new strategy to ensure single-phase formation and uniform particle size distribution for other high-mass-loading binary intermetallic/alloy electrocatalyst systems and can contribute to the practical commercialization of PEMFCs, especially in high-current-density applications, such as automotive