Amorphous manganese oxide-coated montmorillonite as an efficient catalyst for water oxidation

Abstract

Amorphous manganese oxide-coated montmorillonite hybrids were synthesized and characterized by SEM, N₂ adsorption–desorption isotherms, TEM, EDX, XRD, FTIR and AAS. The compounds show efficient water oxidation activity (0.22 mmol O₂/mol Mn.s) with a turnover number of ∼3 in 1 h in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant. Effects of manganese oxide content, calcination temperature, concentration of oxidant on the water oxidation activity of the compounds were studied and compared with other manganese oxides. The O₂ evolution was analyzed by Yagi's kinetic model. The activation energy parameter, leaking of manganese ions into solution, and a cooperatively proposed mechanism for manganese oxide toward water oxidation were also reported for the hybrid.