Manganese oxides supported on nano-sized metal oxides as water-oxidizing catalysts for water-splitting systems: 3-Electrochemical studies

Hydrogen formation by water splitting is very promising to store energy. Water oxidation in water splitting significantly affects the efficiency of hydrogen generation due to the need to apply high overpotential. Among of different compounds, Mn oxides are promising water-oxidizing catalysts. Herein we study the electrochemistry of Mn oxide supported on KAl3(SO4)(2)(OH)(6), Co3O4, CuO, Fe3O4, MgO, NiO, SiO2, SnO2, TiO2, WO3, Zeolite, ZnO or ZrO2. The electrochemical studies showed that redox-active supports such as NiO, Co3O4, Fe3O4 and CuO could significantly change characteristic of Mn oxides. In our experimental conditions, cyclic voltammograms for Mn oxide supported on these redox active supports are significantly different from pure Mn oxides. We found that the effect of support on the water oxidation depend on the conditions of water oxidation. The pure redox-inactive supports such as SiO2, zeolite, MgO and KAl3(SO4)(2)(OH)(6) without Mn oxide showed similar potential to start water oxidation. However, ZnO showed better activity toward water oxidation than other redox-inactive supports. Among pure redox active supports, Co3O4 is excellent for water oxidation. After the deposition of Mn oxides on the supports, the formed compounds showed complicated effect toward water oxidation. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.