Low-Loading Sub-3 nm PtCo Nanoparticles Supported on Co–N–C with Dual Effect for Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells

Developing low-loading Pt-based catalysts possessing glorious catalytic performance can accelerate oxygen reduction reaction (ORR) and hence significantly advance the commercialization of proton exchange membrane fuel cells. In this report, we propose a hybrid catalyst that consists of low-loading sub-3 nm PtCo intermetallic nanoparticles carried on Co–N–C (PtCo/Co–N–C) via the microwave-assisted polyol procedure and subsequent heat treatment. Atomically dispersed Co atoms embedded in the Co–N–C carriers diffuse into the lattice of Pt, thus forming ultrasmall PtCo intermetallic nanoparticles. Owing to the dual effect of the enhanced metal–support interaction and alloy effect, as-fabricated PtCo/Co–N–C catalysts deliver an extraordinary performance, achieving a half-wave potential of 0.921 V, a mass activity of 0.700 A mgPt–1@0.9 V, and brilliant durability in the acidic medium. The fuel cell employing PtCo/Co–N–C as the cathode catalyst with an ultralow Pt loading of 0.05 mg cm–2 exhibits an impressive peak power density of 0.700 W cm–2, higher than that of commercial Pt/C under the same condition. Furthermore, the enhanced intrinsic ORR activity and stability are imputed to the downshifted d-band center and the strengthened metal–support interaction, as revealed by density functional theory calculations. This report affords a facile tactic to fabricate Pt-based alloy composite catalysts, which is also applicable to other alloy catalysts.