H-2 production by water splitting is a promising fuel to store the intermittent energies. However, water splitting is limited by water oxidation. Herein for the first time we used sea sand for support of nano-sized Mn oxide to obtain a new water-oxidizing catalyst. The compound was synthesized by a simple method and characterized by some methods. The water-oxidizing activities of the compound were also studied under cerium(IV) ammonium nitrate and photochemically produced Ru(bpy)(3)(3+). The results showed that the nano-sized manganese oxide coated sea sand is a good manganese-based water-oxidizing catalyst. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.