La 3+ 's Effect on the Surface (101) of Anatase for Methylene Blue Dye Removal, a DFT Study.

Density functional theory (DFT) is a widely used method for studying matter at the quantum level. In this study, the surface (101) of TiO 2 (anatase phase) was considered to develop DFT calculations and explain the effect of lanthanum ion (La 3+ ) on the electronic properties, adsorption capacity, and photocatalytic activity of this semiconductor. Due to the presence of the La 3+ ion, the bandgap energy value of La/TiO 2 (2.98 eV) was lower than that obtained for TiO 2 (3.21 eV). TDOS analysis demonstrated the presence of hybrid levels in La/TiO 2 composed mainly of O2 p and La5 d orbitals. The chemical nature of the La-O bond was estimated from PDOS analysis, Bader charge analysis, and ELF function, resulting in a polar covalent type, due to the combination of covalent and ionic bonds. In general, the adsorption of the methylene blue (MB) molecule on the surface (101) of La/TiO 2 was energetically more favorable than on the surface (101) of TiO 2 . The thermodynamic stability of doping TiO 2 with lanthanum was deduced from the negative heat-segmentation values obtained. The evidence from this theoretical study supports the experimental results reported in the literature and suggests that the semiconductor La/TiO 2 is a potential catalyst for applications that require sunlight.