Hierarchically nanostructured porous TiO2(B) with superior photocatalytic CO2 reduction activity

Hierarchically nanostructured, porous TiO2(B) microspheres were synthesized by a microwave-assisted solvothermal method combined with subsequent heat treatment in air. The materials were carefully characterized by scanning and transmission electron microscopy, X-ray diffraction, CO2 adsorption, and a range of spectroscopies, including Raman, infrared, X-ray photoelectron and UV-Vis spectroscopy. The hierarchical TiO2(B) particles are constructed by ultrathin nanosheets and possess large specific surface area, which provided many active sites for CO2 adsorption as well as CO2 conversion. The TiO2(B) nanostructures exhibited marked photocatalytic activity for CO2 reduction to methane and methanol. Anatase TiO2 and P25 were used as the reference photocatalysts. Transient photocurrent measurement also proved the higher photoactivity of TiO2(B) than that of anatase TiO2. In-situ infrared spectrum was measured to identify the intermediates and deduce the conversion process of CO2 under illumination over TiO2(B) photocatalyst.