In this work, a new gas phase photocatalytic reduction system was designed to convert CO2 into fuels. The optimal conditions (such as humidity, initial concentration of CO2 and the placement of powder photocatalyst in the reactor) for CO2 photocatalytic reduction were systematically investigated with the commercial photocatalyst TiO2 Evonik P25 in the homemade gas phase reactor. Methane (CH4) and hydrogen (H2) were the main products. Also carbon monoxide (CO) was detected. The photocatalytic reduction rate was decreasing with increasing dilution of CO2 by Helium. The humidity is the key role for the CO2 photocatalytic reduction as the source of needed H+ and hydroxyl radicals, the best value of relative humidity was experimentally set to 51.8% leading to the highest yields of all products (CH4, H2 and CO). In addition, the photocatalytic conversion was also influenced by the different placement of photocatalyst, the perfectly spread sample which possessed more effective gas-solid contact showed higher conversion than that of piled one.Keywords: CO2 reduction, Photocatalysis, TiO2
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