Water splitting is a very promising method to produce hydrogen. However, water oxidation is a crucial step for hydrogen production since it can provide cheap electrons for proton reduction. Herein a nanosized Mn oxide immobilized on carbon black as a reasonable catalyst for water oxidation is reported. The composites were synthesized by a simple, lowcost procedure using different ratios of carbon black and Mn oxide. Catalysts were characterized by scanning electron microscopy, energy-dispersive spectroscopy (EDX), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), electronic spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and atomic absorption spectroscopy (AAS). In the next step, the water-oxidizing activities of the composites were observed in the presence of cerium(IV) ammonium nitrate. The composites were reasonable catalysts with turnover frequencies of similar to 0.07 (mmol O-2/mol Mn s). In addition to the water-oxidizing activity, the self-healing for this composite in the experimental condition was also studied. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.