We show that simply by corroding Ni foam in an aqueous solution, it is possible to produce nanostructured surfaces. When Ni foam was corroded in water or an aqueous solution containing NaCl, a dense array of Ni(OH)(2) nanosheets was produced on the surface of the foam. When corroded in the presence of RuCl3, the nanostructured surface composed of Ni(OH)(2) nanosheets decorated with ultrasmall RuO2 nanoparticles was obtained. At an applied voltage of 1.7 V, the combination of these two nanostructured surfaces yielded a water-splitting current density more than three times that obtained on the commercial Pt wire electrodes. (C) 2015 Elsevier B.V. All rights reserved.