Visible light responsive TiO2 nanoparticles modified using Ce and La for photocatalytic reduction of CO2: Effect of Ce dopant content

Abstract

Photocatalytic reduction of CO2 in aqueous solution was performed using TiO2 photocatalysts modified with Ce and La under fluorescent light irradiation. The photocatalysts were prepared using modified sol–gel method with Ce doping content varied between 0 and 2wt%. Comprehensive characterization using XRD, XPS, nitrogen physisorption, SEM, EDX, PL and UV–vis spectroscopy revealed that the introduction of cerium affected the surface, structural and optical properties of the photocatalyts. Among all the doped photocatalysts, 1.5wt% Ce/La/TiO2 showed the highest photocatalytic activity under fluorescent light irradiation. In the liquid phase, a maximum yield of 317.7μmol/gcat for CH3OH was achieved whereas CH4 and CO were the main products in the gas phase with maximum yields of 262.8 and 119.4μmol/gcat, respectively. The addition of Ce and La was found to inhibit the growth of anatase TiO2, increase the surface area and improve the optical properties of the photocatalyst. The existence of Ce3+/Ce4+ mixture was also found to effectively inhibit the electron–hole recombination, enhancing the photocatalytic activity of Ce/La co-doped TiO2.