(629n) Photocatalytic Conversion of CO2 to Fuels by Nanostructured CeO2-TiO2/SiO2 Catalysts

Fossil fuel consumption carries with the significant drawback of environment impact – CO2 emissions that lead to global warming. Conversion of CO2 to useful chemicals such as methane or syngas under mild reaction conditions has promising application prospects. TiO2 is well known as an excellent photocatalyst due to its reusable, inexpensive and easily available properties. However, the  photocatalytic activity of CO2 reduction by TiO2 is low partly due to the fast recombination rate of photo-generated electron-hole pairs. Cerium is a particular lanthanide element which has two oxidation states – Ce(III) and Ce(IV). The oxidation states enable CeO2 to trap photo-generated electrons and thus reduce the electron-hole recombination rate. On the other hand, surface area and surface hydroxyl groups can also influence photocatalytic activity. SBA-15, a mesoporous silica with 1-D pores has been widely used as an effective support for catalyst. In this work, CeO2-TiO2 catalysts with varying compositions were first synthesized via sol-gel preparation method using cerium nitrate and titanium butoxide as precursors. CeO2-TiO2/SiO2 catalysts were finally prepared by adding SBA-15 into the Ce-Ti sol. The catalysts were characterized by XRD, BET, SEM, TEM, UV-vis diffuse reflectance spectroscopy, etc. The photocatalytic activity of CO2 reduction with water was evaluated under UV-vis irradiation. CH4 was found to be the major products measured by a GC-TCD/FID. Catalysts with optimal Ce/Ti ratio and catalyst/support ratio were identified in this study.