Manganese oxide as a water-oxidizing catalyst: from the bulk to Ångström-scale

Abstract

Ångström-scale particles of Mn oxide within the HY zeolite were synthesized and characterized. The compound shows water-oxidizing activity in the presence of cerium(IV) ammonium nitrate as an oxidant. However, the rate of decomposition to MnO₄⁻ for the compound is also high and stability is low in the presence of high (>0.2 M) concentrations of cerium(IV) ammonium nitrate. On the other hand, separated Mn ions incorporated in a tungstate cluster (molecular dimensions of ∼7 × 9 × 4 Å) show no water oxidation in the presence of cerium(IV) ammonium nitrate. These experiments confirm the importance of the size of the catalyst and also cooperation among Mn ions for water oxidation.