High Selectivity of Visible-Light-Driven La-doped TiO2 Photocatalysts for NO Removal

Semiconductors mediated by rare earth metals (REMs) have attracted attention with regard to the degradation of pollutants. In order to enhance the visible response of TiO2, La-doped TiO2 (La-TO) photocatalysts with visible-light-driven capacity for NO removal were successfully synthesized in this study via a facile sol-gel method followed by calcination. A series of La-TiO2 samples with differing weight ratios were evaluated for their photocatalytic performances. It was found that 3% La integrated with TiO2 (in mass ratio) could enhance the removal efficiency of NO (up to 32%) under solar light, which is more than twice that seen with pure TiO2. The resulting products were characterized by a series of techniques, such as XRD, FTIR, UV-vis DRS, BET and (photo) electrochemical analysis. The results indicated that La-doped TiO2 can harvest visible light due to the relatively narrow band gap (from 2.98 to 2.75 eV). More importantly, La dopant improved electronhole separation and suppressed charge carrier recombination, due to the synergistic effect. Furthermore, La-doped TiO2 increased the photo-oxidation efficiency of the transformation from NO to NO3-, owing to inhibition of the production of intermediate NO2 (0.02%). To the best of our knowledge, this study is the first time that La-doped TiO2 has been used to eliminate NO (at the ppb level) in the atmosphere. This study provides a facile and controllable route to fabricate La-TO photocatalyst for NO abatement with high selectivity of NO2 under visible light.