Effect of Crystal Imperfections on Reactivity and Photoreactivity of TiO2 (Rutile) with Oxygen, Water, and Bacteria

The present work considers the effect of crystal imperfections (point defects) on several properties of TiO2 (rutile), such as semiconducting properties and segregation-induced surface properties as well as crystalline structure-related quantities, such as lattice parameter and electronic structure. This work considers the defect disorder of rutile and its solid solutions in terms of both intrinsic and extrinsic defects. The collected empirical data and the related theoretical models indicate that the development of oxide semiconductors with enhanced performance as photocatalysts and photoelectrodes requires recognition of the profound influence of crystal imperfections (point defects) on reactivity and photoreactivity. The effect of defect disorder on the performance of rutile is discussed in terms of its photocatalytic properties in solar water disinfection. The chemistry of the photocatalytic system, consisting of the semiconducting photocatalyst immersed in water involving bacteria, is considered in terms of (i) the reactivity at the oxide/H2O interface leading to the formation of active radical species, (ii) the transport of these species toward bacteria, and (iii) the reactivity of the species with bacteria. It has been documented that changes in defect disorder result in substantial variations of these properties within the stability range of the single phase of rutile. It is shown that defect chemistry may be used as a framework in the modification of semiconducting properties as well as the reactivity and photoreactivity of TiO2 with oxygen, water, and bacteria. The well-defined standard in the studies of TiO2-based materials is proposed.