Modulating the photo-active anatase TiO₂ by cationic co-dopants: A case of iron and lanthanum

The electronic band structure of TiO 2 could be modulated by dopants to harvest the major part of the solar spectrum. A cationic pair of dopant comprising of iron and lanthanum is studied in the lattice of anatase TiO 2 and modifications in the geometrical structure, band structure and optical response are observed. Ferrum and lanthanum doping reduced the band gap of TiO 2 along with inducing visible light absorption. Isolated states due to Fe are created above top of the valence band in Fe@TiO 2 . In case of La@TiO 2 , the La states successfully mixed with the valence and conduction band reducing the band gap. Substitutional La at Ti site in Fe@TiO 2 changed the nature of Fe 3d in the band structure and strongly contributed to the narrowing of band gap. The Fe and La co-doped TiO 2 possess reduced band gap with superior optical response in the visible regime. The Fe and La as cationic pair of dopant synergistically stabilize the system with the improved optical response explaining the experimental observation of enhanced photoactivity.