Preparation of TiO2 microspheres with tunable pore and chamber size for fast gaseous diffusion in photoreduction of CO2 under simulated sunlight

Abstract TiO 2 microsphere with tunable pore and chamber size are prepared by a simple solventhermal method and used as catalyst for the photocatalytic CO 2 reduction. It is found that the hollow microsphere with relative lower surface area of 73.8 m 2 g −1 exhibits increased pore size of 18.1 nm and cavity structure, leading to higher CO 2 diffusion coefficient of 5.40 × 10 −5 cm 2 s −1 compared with the solid and yolk/shell microspheres. Therefore, the hollow microsphere possesses more accessible sites for CO 2 adsorption, which finally gives rise to the enhanced CO production rate of 10.9 ± 0.7 μmol g −1 h −1 under simulated sunlight, which is respectively 1.6 and 1.4 times higher than that of solid and yolk/shell microspheres. Electron dynamic study further demonstrates that hollow microsphere shows the highest photocurrent density and the lowest charge recombination among three microspheres structure, which is attributed to the swift CO 2 diffusion providing fresh CO 2 molecules to rapidly scavenge the photo-generated electrons and finally leading to the excellence catalytic reduction performances. This method could be adopted as a general strategy to prepare high performance TiO 2 catalysts with desirable structural qualities for the photocatalytic CO 2 reduction under nature sunlight.