Titanium dioxide for solar-hydrogen V. Metallic-type conduction of Nb-doped TiO₂

The present work considers quasi-metallic electrical properties for TiO₂. The quasi- metallic effect may be produced by the incorporation of a small amount of donor-type ions, such as Nb, into the TiO₂ lattice forming a solid solution. The metallic properties can be obtained in strongly reduced conditions, which may be achieved by annealing of the specimen at elevated temperatures in the gas phase of very low oxygen activities. The observed effect paves the way for processing photoelectrode with substantially enhanced charge transport.