Metastable Hybrid Intermetallic Pt2CoNi/C: An Interface-Optimized Cathode Catalyst with Cooperative Facet Coupling for Proton Exchange Membrane Fuel Cells

Abstract

Designing cathode catalysts that combine high activity with long-term durability remains a key challenge for proton exchange membrane fuel cells (PEMFCs). Herein, we introduce a previously unreported hybrid intermetallic Pt2CoNi/C catalyst prepared through a simple one-step molten salt synthesis (MSS) method. This straightforward approach provides precise control over atomic arrangement and enables stabilization of a metastable hybrid intermetallic structure that is difficult to achieve using conventional synthesis methods. The resulting catalyst exhibits hexagonal nanoparticles featuring partial atomic ordering and the coexistence of (001) and (111) facets within individual particles. This distinctive surface structure promotes a synergistic interplay of electronic and strain effects, significantly enhancing oxygen reduction reaction (ORR) activity. Importantly, the catalyst also demonstrates excellent durability, maintaining its electrochemical performance even after 50,000 potential cycles in acidic conditions. When evaluated in a practical PEMFC at 60 °C with a low cathode loading of 0.3 mg cm–2, Pt2CoNi/C achieves peak power densities of 0.92 W cm–2 in H2/O2 and 0.70 W cm–2 in H2–air operation. Density functional theory calculations reveal that ordered–disordered interfacial sites exhibit higher ORR onset potentials due to the optimized adsorption energy of reaction intermediates. Overall, this work highlights Pt2CoNi/C as an effective interface-engineered hybrid intermetallic cathode catalyst for next-generation PEMFCs.