LAUSR

Abstract A simple one-pot approach to the in situ construction of ultrathin shells is developed to create a new highly efficient and durable Pt-based electrocatalyst for the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR). Herein, the synthesized ultrathin PdPtAg-shells are located on twinned PdAg nanocrystals and deposited onto graphene (G) (denoted by PdAg@PdPtAg/rGO). The PdAg@PdPtAg/rGO nanocrystal shows a low overpotential of 22 mV at 10 mA cm−2 and excellent electrochemical stability with 99.5% retention over either 12 h or 30 000 cycles of HER. Meanwhile, its ORR activities in acidic and alkaline media are very high and better than that of commercially available Pt/C. Both the experimental and calculated results suggest that the presence of an ultrathin PdPtAg alloy shell synthesized on a PdAg twinned support is the main reason for the greatly enhanced activities. Moreover, the twinned PdAg nanocrystal provides a number of twinned grain boundaries and defect sites (such as step, edge and kink sites). This typical structure represents a new strategy for synthesizing high-performance Pt-based catalysts, promoting their practical applications in energy conversion and storage devices.