Photocatalytic reduction of CO2 with water vapor on surface La-modified TiO2 nanoparticles with enhanced CH4 selectivity

Abstract Surface La-modified TiO 2 nanoparticle samples were prepared by a simple sol–gel method. The structure and properties of the catalysts were characterized and analyzed by means of XRD, TEM, BET, UV–vis DRS, CO 2 -TPD, XPS, Raman and Theoretical Calculation. The most La 3+ was found to deposit onto the TiO 2 in the form of La 2 O 3 particles, and a tiny number of La atoms modify TiO 2 by substituting the surface Ti atom in the form of Ti O La, leading to the generation of oxygen vacancies and Ti 3+ for balancing the charge. The La-modified TiO 2 photocatalysts were investigated in the photocatalytic reduction of CO 2 with water vapor under the 300 W Xe arc lamp irradiation. The La-modified TiO 2 showed high CH 4 yield of 3.457 μmol under 20 h light irradiation, which is 13 times of that over commercial P25. The enhanced photocatalytic performances were attributed to the synergistic effects of basic characteristics of La 2 O 3 for CO 2 adsorption, the oxygen vacancies for water vapor activation and Ti 3+ for electron separation.