Photochemical Water Oxidation by Manganese Oxides Supported on Zeolite Surfaces

Photocatalytic properties of disordered birnessite‐like Mn oxides deposited on the zeolite Y surface is investigated. Synthesis was carried out by ion‐exchanging Mn 2+ along with M 2+ =Ba 2+ , Sr 2+ , Ca 2+ , Mg 2+ into zeolite, followed by precipitation of nanosized Mn oxides on the zeolite surface after reaction with KMnO 4 . These samples are labeled M 2+ MnO x ‐Y, and they were treated with K + to prepare KMnO x ‐Y(M 2+ ). XRD, XPS, Raman, and electron microscopy provided information on the comparative structural features for M 2+ MnO x ‐Y and KMnOx‐Y(M 2+ ). Photocatalytic water oxidation using these samples was evaluated using Ru(bpy) 3 2+ ‐S 2 O 8 2− system. The catalytic activity of KMnOx‐Y(M 2+ ) is higher than M 2+ MnO x ‐Y, for comparable Mn loadings, and forms the interesting observation in this paper. For M 2+ MnO x ‐Y, the catalytic activity normalized to the Mn content followed the order: Ba 2+ > Sr 2+ > Ca 2+ > Mg 2+ and is possibly reflection of the lower Mn loadings, which leads to smaller MnO x crystallites.