Weakening Intermediate Bindings on CuPd/Pd Core/shell Nanoparticles to Achieve Pt‐Like Bifunctional Activity for Hydrogen Evolution and Oxygen Reduction Reactions

Although Pd is a potential substitution of Pt‐based catalysts for the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), the binding of *H and oxygenated (*O, *OOH, *OH) intermediates on Pd are stronger than on Pt, leading to its inferior activity for HER and ORR. In this work, CuPd/Pd core/shell nanoparticles with an ultrathin Pd shell (0.5 nm) are developed, which demonstrate the Pt‐like bifunctional activity for HER and ORR in acid electrolytes. The overpotential at 350 mA cm−2 for HER and the half‐wave potential for ORR on the optimal CuPd/Pd core/shell NPs are 76 mV and 0.854 V versus reversible hydrogen electrode (RHE), respectively, which are comparable to that of Pt and among the best of the reported Pd‐based catalysts. Density functional theory calculations indicate that the significantly enhanced HER/ORR activity on CuPd/Pd core/shell NPs with 0.5 nm Pd shell stem from the compressive strain induced downshift of d‐band center for Pd (by 2.0%), which weakens the binding strength of *H and oxygenated intermediates and promotes the reaction kinetics. The lowered d‐band center of CuPd/Pd core/shell nanoparticles with ultrathin 0.5 nm Pd shells weakens the intermediate bindings, which leads to the Pt‐like bifunctional activity for highly efficient hydrogen evolution reaction and oxygen reduction reaction reactions, and is promising for use in water electrolysis and a H2 powered fuel cell.