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.