Hierarchical Gd–La codoped TiO2 microspheres as robust photocatalysts

Robust Gd–La codoped TiO2 microspheres with diameter of 2∼3 μm were successfully synthesized via a hydrothermal method using poly(ethylene glycol)-block–poly(propylene glycol)-block–poly(ethylene glycol) as a template. The photocatalytic activity of the Gd–La codoped TiO2 microspheres evaluated by photodegrading methyl orange (MO) has been significantly enhanced compared to that of undoped TiO2 microspheres. Ti4+ may substitute for La3+ and Gd3+ in the lattices of rare earth oxides to create abundant oxygen vacancies and surface defects for electron trapping and dye adsorption, accelerating the separation of photogenerated electron–hole pairs and MO photodegradation. The formation of an exciton 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 microspheres, resulting in robust photocatalysts. The results suggest that Gd–La codoped TiO2 microspheres calcined at 350 °C are very promising for enhancing the photocatalytic activity of photocatalysts.