Hydrogen-Mediated Thin Pt Layer Formation on Ni3N Nanoparticles for the Oxygen Reduction Reaction

A simple wet-chemical route for the preparation of core–shell-structured catalysts was developed to achieve high oxygen reduction reaction (ORR) activity with a low Pt loading amount. Nickel nitride (Ni3N) nanoparticles were used as earth-abundant metal-based cores to support thin Pt layers. To realize the site-selective formation of Pt layers on the Ni3N core, hydrogen molecules (H2) were used as a mild reducing agent. As H2 oxidation is catalyzed by the surface of Ni3N, the redox reaction between H2 and Pt­(IV) in solution was facilitated on the Ni3N surface, which resulted in the selective deposition of Pt on Ni3N. The controlled Pt formation led to a subnanometer (0.5–1 nm)-thick Pt shell on the Ni3N core. By adopting the core–shell structure, higher ORR activity than the commercial Pt/C was achieved. Electrochemical measurements showed that the thin Pt layer on Ni3N nanoparticle exhibits 5 times higher mass activity and specific activity than that of commercial Pt/C. Furthermore, it is expected that the proposed simple wet-chemical method can be utilized to prepare various transition-metal-based core–shell nanocatalysts for a wide range of energy conversion reactions.