Ni-Pd core-shell nanoparticles with Pt-like oxygen reduction electrocatalytic performance in both acidic and alkaline electrolytes

Fabrication of non-Pt high-performance oxygen reduction reaction (ORR) catalysts is essential for the application of fuel cells. In this work, monodisperse bimetallic Ni-Pd core-shell nanoparticles (NPs) with tunable shell compositions and contents were synthesized by using a modified one-pot colloidal approach and characterized. Also, the core shell structure dependence of their ORR performance without the interruption of an intermetallic phase was explored. The core-shell structured catalysts (Ni@Pd3/C NPs) exhibited a robust ORR activity and stability with a high onset potential of 0.99 V, a half-wave potential of 0.87 V and an average electron transfer number of 3.91 in 0.1 M HClO₄. Furthermore, a high onset potential of 0.98 V, a half-wave potential of 0.86 V and an average electron transfer number of 3.98 were achieved in 0.1 M KOH. These results are comparable to those of the commercially available Pt/C catalysts. Moreover, the catalysts also maintained a good long-term cycling stability in both acidic and alkaline electrolytes. Thus, this work demonstrates that the ORR performance of the Ni-Pd alloy could be boosted through constructing the core-shell structure with a Pd-enriched surface and the Ni-Pd model alloy could be further applied to assess the role of the Pd-based core-shell structure in other electrochemical catalytic reactions.