A nanostructured nickel–cobalt alloy with an oxide layer was fabricated and its superior catalytic activity towards the electrochemical oxygen evolution reaction in alkaline media was investigated. Firstly, a NiCo–SiO₂ composite film was prepared via a potentiostatic electro-codeposition method. Then the SiO₂ template was etched and the NiCo component was activated leading to the generation of a NiCoO_x layer during consecutive CV scans in concentrated alkaline solution. The results show that this nanostructured NiCo alloy with the oxide layer can provide a current density of 100 mA cm⁻² in 1.0 M KOH at a low overpotential of 326 mV and exhibits good stability towards water oxidation. The excellent OER performance is enabled with the unique metal-oxide structure, which allows high electrical conductivity in the metal and high catalytic activity on the oxide.