Conductive Nb-doped TiO2 thin films with whole visible absorption to degrade pollutants

Titanium dioxide (TiO2) is widely applied as a photocatalyst; however, its widespread use is limited by its wide band gap; moreover, it is challenging and interesting to make TiO2 absorb the whole range of visible light. In this study, conductive Nb-doped TiO2 (NTO) thin films have been demonstrated to increase the photocatalytic performance of anatase TiO2 due to whole visible-light absorption and efficient charge transfer. Interestingly, the origin of the whole visible absorption was ascribed to the extended free-carrier absorption (FCA) based on theoretical calculations and electrical properties. The NTO thin film with a high degree of (004) orientation showed better photocatalytic performance than others due to its better absorption, more effective charge transfer, and greater ability to completely degrade pollutants. In addition, a synergistic effect for the enhancement of photocatalytic performance was observed when the thin films were irradiated by alternating the wavelength of the LED light source between 365 nm and 515 nm. We have also demonstrated that these thin films are suitable for self-cleaning coatings.