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

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.