The role of interfacial lattice Ag+ on titania based photocatalysis

Ag-0/Ag+/TiO2 composites were prepared via alkalescent hydrothermal process in aqueous ammonia, and Ag+/TiO2 was prepared by eluting the Ag-0 cluster from the Ag-0/Ag+/TiO2 composites with K-3[Fe(CN)(6)]/aqueous ammonia. Methyl orange (MO) and Rhodamine B (RhB) were used to test the photocatalytic activity of the photocatalysts. The photocatalytic activity of the composites was greatly improved after eluting Ag-0 clusters from the Ag-0/Ag+/TiO2 composites. Interfacial lattice Ag+ cations but not Ag-0 clusters are responsible for improving the photocatalytic performance of the composites in this work. XPS measurement shows that the chemical state of the interfacial lattice Ag+ cation is different with the surface chemical adsorbed Ag+ cation. Surface chemical adsorbed Ag+ cation is invalid to promote the photocatalytic activity of TiO2 while Na+ cation can cancel the promotional effect of the interfacial lattice Ag+ cation by competitively occupying the interfacial lattice defects. The 2 h turn over numbers of the interfacial lattice Ag+ cations to the degradation of MO and RhB reach 8 and 10, respectively, which show that the interfacial lattice Ag+ cations act as recyclable catalytic sites but not one-time consumptive species. (c) 2012 Elsevier B.V. All rights reserved.