Transition metal hydroxides play an important role in the development of high-efficiency electrocatalysts for water splitting. Here we report an advanced electrocatalyst made of NiCo layered double hydroxide (NiCo LDH) supported by three-dimensional (3D) NiCo foam (NCF). The microstructure and physicochemical properties of the NiCo LDH are custom-modified by the N2/Ar radio-frequency (RF) plasma. The plasma enables effective doping of the NiCo LDH catalyst with nitrogen (partial nitridization), leading to the substantial improvement of electrocatalytic performance of the N-doped NiCo LDH (N-NiCo LDH) for overall water splitting in 1 M KOH. The overpotentials required to transfer a current density of 10 mA cm−2 (η10) in the HER and OER processes are 100 mV and 190 mV, respectively. At this current density, the H2 and O2 amounts generated by the N-NiCo LDH catalyst in 1 M KOH electrolyte are about 90 and 48 μmol h-1, respectively. The demonstrated electrocatalytic performance is very competitive with other state-of-the-art catalysts based on similar layered double hydroxide materials systems.