Synthesis of TiO2 nanoparticles using novel titanium oxalate complex towards visible light-driven photocatalytic reduction of CO2 to CH3OH

TiO2 nanoparticles (NPs) with controlled crystalline structure and morphology were synthesized by a facile hydrothermal method using a novel titanium oxalate complex. The structure, morphology, and spectral properties of the synthesized TiO2 NPs were characterized by X-ray diffraction, Raman spectroscopy, scanning/transmission electron microscopy, and UV-vis diffuse reflectance spectroscopy. The titania phases of anatase, rutile, or brookite can be easily tuned by tailoring the solution pH during reaction. Highly ordered flower-like rutile could be obtained with oxalic acid additive. The synthesized TiO2 catalysts showed excellent visible light absorption and remarkable photocatalytic activity for CO2 reduction to CH3OH under both UV-vis and visible light irradiation, mainly due to doped carbon and nitrogen. Bicrystalline anatase-brookite composite afforded maximum CH3OH yield, attributed mainly to the unique electrical band structures and efficient charge transfer between the two crystalline phases. (C) 2012 Elsevier B.V. All rights reserved.