PNNL

Abstract

Titanium dioxide (TiO2) is a versatile material that finds uses as a promoter in heterogeneous catalysis, gas sensor, in protective and optically active coatings, as a pigment in paints, and most importantly, as a promising photoactive material in the photocatalytic degradation of enivironmental pollutants [1] [2] and in solar cells [3]. TiO2 exists in three common crystallographic phases rutile, anatase and brookite. Commercial TiO2 powder catalysts are a mixture of rutile anatase and, for reasons not yet completely understood, anatase is the more photocatalytically active form [1]. Many detailed surface investigations have been performed on single-crystalline rutile TiO2 in order to understand, and ultimately control, the surface chemistry underlying all these applications. A rather complete understanding of the surface properties of rutile has evolved [4]. In comparison, next to nothing is known about the surface properties of the technologically more important anatase phase, mainly for lack of appropriate single-crystalline specimens.