A high-performance three-dimensional Ni-Fe layered double hydroxide/graphene electrode for water oxidation

Water oxidation to evolve oxygen is the key step in water splitting and is related to a variety of energy systems. Here, we report a facile electrodeposition process to immobilize nickel-iron layered double hydroxide (Ni-Fe LDH) nanoplates on three-dimensional electrochemically reduced graphene oxide (3D-ErGO) for water oxidation. This Ni-Fe LDH/3D-ErGO electrode has a three-dimensional interpenetrating network with Ni-Fe nanoplates uniformly decorated on graphene sheets. It has an electrochemically active surface area (EASA) 3.3 times that of conventional planar electrodes. The open porous structure of this electrode also makes its EASA fully accessible to the electrolyte for water oxidation and easy release of oxygen gas. This electrode can be directly used for catalysing the oxygen evolution reaction (OER) in alkaline media without using a binder and conductive additive, exhibiting a small overpotential of 0.259 V and a low Tafel slope of 39 mV dec^-1. It outperforms the precious IrO₂ catalyst in activity, kinetics, and electrochemical stability.