NiO–CoFe 2 O 4 electrocatalyst prepared on Ni foam by one-step hydrothermal method for efficient overall water splitting

The development of non-noble bifunctional electrocatalysts with low cost, high performance and stability for overall water splitting is particularly important for solving energy problems in future. In this paper, a micron spherical NiO–CoFe2O4 film composed of nanosheets was synthesized on Ni foam (NF) as a high-efficiency bifunctional electrode through one-pot hydrothermal method. The NiO–CoFe2O4/NF owns excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activity and stability due to the combination effect between NiO and CoFe2O4, good electrical conductivity of three-dimensional (3D) porous Ni foam and unique flower-spherical structure of NiO–CoFe2O4/NF. In alkaline solution, HER and OER only need low overpotential of 97 mV and 157 mV to reach 10 mA cm−2 current density, respectively. In addition, NiO–CoFe2O4 is used as both anode and cathode to overall water splitting in an alkaline electrolyte requires 1.54 V to realize a current density of 10 mA cm−2. The work provides an easy way for the preparation of bifunctional electrocatalysts for overall water splitting.