High-Loading Platinum-Cobalt Intermetallic Compounds with Enhanced Oxygen Reduction Activity in Membrane Electrode Assemblies

Abstract

Platinum-based intermetallic compounds (IMCs) are emerging as promising oxygen reduction reaction (ORR) catalysts in proton exchange membrane fuel cells (PEMFCs). However, large-scale synthesis of supported IMCs catalysts with small particle size and high loading remains a significant challenge, greatly hindering the applications of IMCs in PEMFCs. Herein, carbon-supported PtCo IMCs with a metal loading of ∼40% and a mean size of ∼5 nm were successfully prepared via a simple impregnation method and display excellent performances in membrane electrode assemblies (MEA). The ordering degree of the PtCo IMCs can be tuned by carefully manipulating the annealing conditions. X-ray photoelectron spectroscopy characterizations demonstrate that the electronic interactions between Pt and Co are strengthened due to highly ordered structure of PtCo IMCs, thus promoting the ORR performance. The optimized PtCo IMCs exhibit an excellent ORR performance with a specific activity of 2.02 mA cm⁻² and mass activity of 0.92 A mgPt⁻¹ at 0.9 V (vs. RHE), which are approximately 5 times and 6 times higher than those of the commercial Pt/C. More importantly, the PtCo IMCs also display enhanced performance in MEA, and the power density at 1.5 A cm⁻² and 2.5 A cm⁻² is 0.949 W cm⁻² and 1.244 W cm⁻², respectively, thus reducing the Pt usage by 40% compared to Pt/C. This work offers a facile route for the scale preparation of platinum-based intermetallic compounds and promotes their practical applications in PEMFCs.