The solid-solid interface:: Explaining the high and unique photocatalytic reactivity of TiO2-based nanocomposite materials

This article reviews the role of solid-solid interface between phases and materials in photocatalytic reactions. We hypothesize that the solid-solid interface is a key structural feature that facilitates charge separation to hinder recombination and enhance photocatalytic efficiency, and may be the locus of defect sites that act as catalytic "hot spots". The focus of this article is TiO2-based photocatalytic materials and we present the work of others and some of our recent work synthesizing, characterizing, and testing TiO2-based nanocomposites, especially mixed-phase titanium dioxide. The implications of this deeper understanding of structure-function relationships to energy applications are also discussed. (C) 2007 Elsevier B.V. All rights reserved.