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

Surface La-modified TiO2 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, CO2-TPD, XPS, Raman and Theoretical Calculation. The most La3+ was found to deposit onto the TiO2 in the form of La2O3 particles, and a tiny number of La atoms modify TiO2 by substituting the surface Ti atom in the form of Ti-O-La, leading to the generation of oxygen vacancies and Ti3+ for balancing the charge. The La-modified TiO2 photocatalysts were investigated in the photocatalytic reduction of CO2 with water vapor under the 300 W Xe arc lamp irradiation. The La-modified TiO2 showed high CH4 yield of 3.457 mu mol 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 La2O3 for CO2 adsorption, the oxygen vacancies for water vapor activation and Ti3+ for electron separation. (C) 2014 Elsevier B.V. All rights reserved.