First‐Principles Study of the Effects of La^2+/3+ Doping and Oxygen Vacancies on TiO₂ Magnetism, Carrier Lifetime, Activity, and Absorption Spectra

The effects of photocatalytic performance and magnetism between La doping and oxygen vacancy on rutile and anatase TiO₂ systems are rarely compared. Oxygen vacancies in rutile and anatase TiO₂ are also experimentally challenging to control accurately. Herein, the first‐principles generalized gradient approximation (GGA + U) method is used to investigate the effects of La²⁺/La³⁺doping and oxygen vacancy on TiO₂ magnetism and photocatalytic performance. Results of magnetic calculation show that La²⁺ doping and oxygen vacancies are magnetic to TiO₂, whether rutile or anatase, and that the bound magnetic polaron is the source of ferromagnetism in the anatase Ti₁₅La²⁺O₃₁ system. The anatase Ti₃₀La₂²⁺O₆₂ system can achieve room‐temperature ferromagnetism at Curie temperature. The calculation results of photocatalytic performance show that the anatase‐type Ti₁₅La³⁺O₃₁ system has minimum formation energy, the highest stability, maximum electric dipole moment, the strongest carrier activity, the strongest polarization ability, the slowest electron–hole recombination, the longest lifetime, and remarkable absorption spectrum redshift among the tested systems.