Efficient visible-light photocatalysts from Gd–La codoped TiO2 nanotubes

Robust visible-light Gd–La codoped TiO2 nanotubes were successfully synthesized via an ultrasonic hydrothermal method and the photocatalytic activities were evaluated by photodegrading Rhodamine B (RB). The calcined Gd–La codoped TiO2 nanotubes have significantly enhanced photocatalytic activities than the uncalcined ones. The La3+ and Gd3+ in the lattices of rare earth oxides may be substituted by Ti4+, creating abundant oxygen vacancies and surface defects for electron trapping and dye adsorption, accelerating the separation of photogenerated electron–hole pairs and RB photodegradation. The formation of an excitation energy level below the conduction band of TiO2 from the binding of electrons and oxygen vacancies decreases the excitation energy of Gd–La codoped TiO2 nanotubes, resulting in robust photocatalysts. The results suggest that Gd–La codoped TiO2 nanotubes calcined at 500 °C are very promising for enhancing the photocatalytic activity of photocatalysts in visible-light region.