Optimum reductants ratio for CO<sub>2</sub> reduction by overlapped Cu/TiO<sub>2</sub>

Abstract

Cu-doped TiO2 (Cu/TiO2) film photocatalyst was prepared by combination of sol-gel and dip-coating process, and pulse arc plasma method. The effect of Cu/TiO2 photocatalyst on CO2 reduction performance with reductants of H2O and H2 was investigated. In addition, this study investigated overlapping two Cu/TiO2 coated on netlike glass fiber discs in order to utilize the light effectively as well as increase the amount of photocatalyst used for CO2 reduction. The characterization of prepared Cu/TiO2 film coated on netlike glass fiber was analyzed by SEM, EPMA, TEM and EELS. Furthermore, the CO2 reduction performance of Cu/TiO2 film was tested under illumination of Xe lamp with or without ultraviolet (UV) light, respectively. As a result, the best CO2 reduction performance has been achieved under the condition of CO2/H2/H2O = 1:0.5:0.5 with UV light illumination as well as without UV light illumination. Under the illumination condition with UV light, the highest concentration of CO for Cu/TiO2 overlapped is 1.4 times as large as that for single Cu/TiO2, while the highest concentration of CH4 for Cu/TiO2 overlapped is 1.7 times as that for single Cu/TiO2. Under the illumination condition without UV light, the highest molar quality of CO per weight of photocatalyst for Cu/TiO2 overlapped is 1.1 times as that for single Cu/TiO2. The theoretical molar ratio of CO2/H2O or CO2/H2 to produce CO is 1:1, while the theoretical molar ratio of CO2/H2O or CO2/H2 to produce CH4 is 1:4. Since the molar ratio of CO2/H2/H2O = 1:0.5:0.5 can be regarded as the molar ratio of CO2/total reductants = 1:1, it is believed that the results of this study follow the reaction schemes of CO2/H2O and CO2/H2.