Photoreduction of CO2 over the well-crystallized ordered mesoporous TiO2 with the confined space effect

Ordered mesoporous titanium dioxide with crystalline wall was successfully synthesized by combining evaporation induced self-assembly process with two-step calcination processes. The ordered mesoporous titanium dioxide not only shows a higher production efficiency of CH4, which is 71 times and 53 times higher than that of commercial titanium dioxide (P25) and disordered mesoporous titanium dioxide, respectively, but also exhibits a better stability for CO2 photoreduction. The remarkable performance of the ordered mesoporous titanium dioxide for CO2 photoreduction probably benefits from the confined space effect of ordered mesoporous structure because (1) the active sites exist not only on the surface of the particles, but also exist in the pores; (2) gas molecules collide with the pore walls more frequently in the case of Knudsen diffusion; (3) the highly ordered mesoporous structure develops a high-efficient CO2 adsorption ability, smooth flow of gas molecules and improved separation and transport of electron-hole. (C) 2014 Elsevier Ltd. All rights reserved.