Using sustainable energies, large-scale electrochemical and photochemical hydrogen production from water splitting are greatly limited by water-oxidation reaction. Herein we report that nanolayered Mn oxide obtained in the reaction of KMnO4 and Mn2CO10 is a good catalyst toward water oxidation. The Mn oxide was synthesized by a simple method and characterized by scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and atomic absorption spectroscopy. In the next step, the water oxidizing activity of the oxide was considered in the presence of cerium(IV) ammonium nitrate. The compound shows good water-oxidizing activity with turnover frequencies of similar to 0.5 (mmol O-2/(mol Mn.s)) toward water oxidation. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.