Titanium dioxide for solar-hydrogen II. Defect chemistry

The present work considers defect disorder of TiO₂ and the related electrical properties, including electrical conductivity and thermoelectric power, at elevated temperatures. Defect chemistry of TiO₂ is described in terms of the relationships between the concentration of defects and oxygen activity. These relationships may be used for the imposition of controlled defect disorder and the related functional properties of TiO₂, including electronic structure and charge transport. It is shown that defect chemistry may be used as a framework for tailoring the photoelectrochemical properties of TiO₂ in order to achieve those properties required for optimised photoelectrode performance in solar-hydrogen generation. Defect chemistry may also be used for the imposition of surface active sites responsible for enhanced photoreactivity between the TiO₂ surface and water.