Strain-Modulated Platinum–Palladium Nanowires for Oxygen Reduction Reaction

Abstract

Electrocatalytic activity of alloy nanocatalytsts can be manipulated effectively by tuning their physical properties (ensemble, geometric, and ligand effects) to afford optimal surface structure and compositions for proton exchange membrane fuel cell (PEMFC) application. Herein, highly catalytic platinum-palladium nanowires (Pt_<i>n</i>Pd_100-<i>n</i> NWs) with a subtle lattice strain and Boerdijk-Coxeter helix type morphology are synthesized through a surfactant-free, thermal single phase solvent method. X-ray diffraction results show that Pt_<i>n</i>Pd_100-<i>n</i> NWs are exposed through the (111) facets and their shrinking or expanding lattice parameters can be modulated by the alloy compositions. Electrochemical results reveal that their high catalytic activity correlates with the lattice shrinking, facets, and bimetallic compositions, showing higher activity when the ratio of Pt and Pd is ∼78:22, which is further supported by DFT results. Compared to the nanoparticle type platinum-palladium alloyed catalysts with similar metal compositions (Pt_<i>n</i>Pd_100-<i>n</i> NPs), the Pt_<i>n</i>Pd_100-<i>n</i> NWs exhibit significantly improved electrocatalytic activity and stability for the oxygen reduction reaction. These findings open new strategies to design the highly active and stable alloy nanocatalysts with controllable compositions.