Construction of multi-dimensional core/shell Ni/NiCoP nano-heterojunction for efficient electrocatalytic water splitting

Abstract

Tuning structure, morphology and electronic state of electrocatalysts is essential to achieve highly efficient water splitting. Herein, we report synthesis of snap bean-like multi-dimensional core/shell Ni/NiCoP nano-heterojunctions (NHs) by adopting a solid phase transformation strategy. In the special structure, Ni nanoparticles are enclosed and strung by single phased NiCoP, forming strings of Ni/NiCoP core/shell heterojunctions, which showed improved stability and activity for both hydrogen evolution (HER) and oxygen evolution reactions (OER). X-ray photoelectron spectroscopy and synchrotron-radiation-based X-ray absorption spectroscopy reveal that interactions at the interface of Ni/NiCoP greatly changed electronic structures, which is a key intrinsic factor to underpin the enhanced electrocatalytic performance. Density functional theory calculations demonstrate Ni/NiCoP interface provide more optimal binding strength for H adatom and H2O molecule for HER, strong capture of hydroxyl, high valence Ni/Co species for OER. All these peculiarities facilitate the electrocatalytic process: only 1.57 V was needed to reach the current density of 10 mA·cm−2 for the overall water splitting using Ni/NiCoP NHs as both electrodes. This work demonstrates a facile strategy for synthesis of sophisticated catalytic interface at nano level and endows nano-heterojunction catalysts with enhanced performance for catalytic applications.