Diversity of TiO 2 : Controlling the Molecular and Electronic Structure of Atomic-Layer-Deposited Black TiO 2

Visually black, electrically leaky, amorphous titania (am-TiO ) thin films were grown by atomic layer deposition (ALD) for photocatalytic applications. Broad spectral absorbance in the visible range and exceptional conductivity are attributed to trapped Ti in the film. Oxidation of Ti upon heat treatment leads to a drop in conductivity, a color change from black to white, and crystallization of am-TiO . ALD-grown black TiO , without any heat treatment, is subject to dissolution in alkaline photoelectrochemical conditions. The best photocatalytic activity for solar water splitting is obtained for completely crystalline white TiO .