Three‐Dimensional Graphene‐Foam‐Supported Hierarchical Nickel Iron Phosphide Nanosheet Arrays as Efficient and Stable Bifunctional Electrocatalysts for Overall Water Splitting

Abstract The development of stable non‐noble metal‐based electrocatalysts with high performance for overall water splitting is critical in the field of renewable energy. Herein, we combined nickel iron phosphide (NiFe‐P) nanosheets with three‐dimensional porous graphene foam (3DGF) as a substrate to design a bifunctional electrocatalyst NiFe‐P@3DGF with excellent catalytic activity towards oxygen and hydrogen evolution reactions (OER and HER, respectively) under alkaline conditions. At a current density of 10 mA cm −2 , the overpotentials for the OER and HER are less than 189 and 131 mV, respectively, and the stabilities exceed 50 h. Furthermore, this bifunctional catalyst also exhibits excellent water‐splitting capability with a cell voltage of 1.57 V at 10 mA cm −2 . The special structure of the 3DGF substrate with its large surface area, high conductivity, and robust skeleton, as well as the unique core–shell structure of NiFe (oxy)hydroxides/phosphide formed throughout the reaction promote the high activity of the electrocatalyst. Therefore, this work provides a new perspective to exploit the efficient bifunctional electrocatalyst using porous 3DGF as the substrate.