Electronic and Lattice Strain Dual Tailoring for Boosting Pd Electrocatalysis in Oxygen Reduction Reaction

Abstract

Deliberately optimizing the d-band position of an active component via electronic and lattice strain tuning is an effective way to boost its performance for a given catalytic reaction. We herein demonstrate this concept by constructing core-shell Au@NiPd nanoparticles with NiPd alloy shells of only three atomic layers through combining an Au catalysis with the galvanic replacement reaction. In the as-prepared core-shell nanostructures, the Au that has larger electronegativity in the core region modulates the Pd electronic configuration, while the Ni atoms alloyed in the ultrathin shells neutralize the lattice stretching in Pd shells exerted by the Au cores, equipping the active Pd metal with a favorable d-band position for electrochemical oxygen reduction reaction (ORR), as verified by experimental characterizations and theoretical calculations. In particular, when served as ORR electrocatalysts in an alkaline medium, the core-shell Au@NiPd nanoparticles with a Ni/Pd atomic ratio of 3/7 in the sub-nano shell region (Au@Ni3Pd7) exhibit a half-wave potential of 0.92 V, specific activity of 3.7 mA cm-2 and mass activity of 0.65 A mg-1 at 0.9 V vs. reversible hydrogen electrode (RHE), much better than those of their core-shell Au@Pd counterparts, commercial Pd/C and Pt/C catalyst, as well as the majority of the recently reported Pd- even Pt-based electrocatalysts. This study highlights the synthetic novelty and concept of dual tailoring for enhancing the electrocatalytic behavior of an active metal, which might be inspirable for developing other catalysts with desired efficiency towards a large variety of target reactions.