Enhancing CO2 photoconversion activity of TiO2 via synergistic effects of La-doping and ammonia vapor heat treatment

A novel, sample and economical method was used to prepare the new co-doped TiO 2 photocatalysts and evaluated for CO 2 photoconversion under visible-light irradiation. The La(NO 3 ) 3 -TiO 2 photocatalyst was obtained by the sol–gel method and then was heat treated with different concentrations of ammonia vapor. It was found that the synergistic modification of TiO 2 photocatalyst by La(NO 3 ) 3 and ammonia vapor could improve its photocatalytic performance under visible light. The photocatalytic assessment presented a significantly amelioration in CO 2 photoconversion, giving 3.078 μmol CH 4 production in 4 h. The structures and properties of the photocatalysts were characterized and analyzed by means of XRD, SEM-EDS, HRTEM, BET, XPS, FTIR, ICP-AES, UV–vis DRS and theoretical calculation. The performance of the photocatalyst could be correlated to contributions of various phenomena such as larger specific surface area and the co-exposed (1   0   1) and (0   0   1) facets of anatase TiO 2 . Finally, the most likely substituted structures were obtained. The results of DFT + U theoretical calculation showed that La and N could modify TiO 2 by replacing surface Ti atoms and internal O atoms, respectively.