The reaction of KMnO4 with cobalt nanoparticles coated with SiO2 layers forms a highly dispersible, magnetically separable and environmentally friendly catalyst toward water oxidation. The compound was characterized by scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, X-ray Photoelectron Spectroscopy, X-ray diffraction, electron spectroscopy, Fourier transform infrared spectroscopy and atomic absorption spectroscopy. The nano-sized catalyst shows self-healing in the presence of cerium(IV) ammonium nitrate and under the water-oxidation conditions. The turnover frequencies for the catalyst toward water oxidation in the presence of cerium(IV) ammonium nitrate and [Ru(bpy)(3)](3+) are 0.15 and 0.25 (mmol O-2/mol Mn.s), respectively. Copyright (c) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.