Photoreduction of CO2 to fuels under sunlight using optical-fiber reactor

An optical-fiber reactor is employed to photocatalytically reduce CO2 with H2O to fuels under UVA artificial light and concentrated natural sunlight. The optical fiber is coated with gel-derived TiO2-SiO2 mixed oxide-based photocatalysts. Fe atom is found to insert into the TiO,-SiO, lattice during sot-gel process, resulting in the full visible light absorption as well as the effect on product selectivity of the derived catalyst. Under UVA, ethylene is mainly produced on Cu-Fe/TiO2 catalyst with the quantum yield of 0.0235%, whereas Cu-Fe/TiO2-SiO2 catalyst is observed to favor methane production with the quantum yield of 0.05%. Meanwhile, the overall energy efficiency is found to be much higher on Cum-Fe/TiO2-SiO2 (0-0182%) than on its Cu-Fe/TiO2 counterpart (0.0159%). There is only methane evolved over both bare TiO2-SiO2 and Cu-Fe/TiO2-SiO2 catalysts under natural sunlight with the production rates of 0.177 and 0.279 mu mol/gcat h, respectively. For the former catalyst, the increase in light intensity is not found to compensate the inherent electron-hole recombination in the TiO2-SiO2-acac catalyst, whereas the superior photoactivity of Cu-Fe/TiO2-SiO2 catalyst under natural sunlight could be ascribed to its full absorption of visible light. (c) 2008 Elsevier B.V. All rights reserved.