Fe doped Ni₅P₄ nanosheet arrays with rich P vacancies via phase transformation for efficient overall water splitting

Proper vacancy engineering is considered as a promising strategy to improve intrinsic activity, but it is challenging to construct rich vacancies by a simple strategy. Herein, Fe doped Ni₅P₄ nanosheet arrays with rich P vacancies are developed via a facile phase transformation strategy. Based on systematic investigations, we have demonstrated that an optimized surface electronic structure, abundant active sites and improved charge transport capability can be effectively achieved by vacancy engineering. Consequently, Fe doped Ni₅P₄ with rich vacancies show remarkable catalytic performances with 94.5 mV for the hydrogen evolution reaction (HER) and 217.3 mV for the oxygen evolution reaction (OER) at 10 mA cm^-2, respectively, as well as good durability. When directly employed as working electrodes, the as-obtained Fe doped Ni₅P₄ with rich vacancies can attain 10 mA cm^-2 at a low voltage of 1.59 V. This work demonstrates a feasible strategy for rationally fabricating electrocatalysts with rich vacancies via a simple phase transformation.