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

Abstract

Cu-doped TiO 2 (Cu/TiO 2 ) film photocatalyst was prepared by combination of sol-gel and dip-coating process, and pulse arc plasma method. The effect of Cu/TiO 2 photocatalyst on CO 2 reduction performance with reductants of H 2 O and H 2 was investigated. In addition, this study investigated overlapping two Cu/TiO 2 coated on netlike glass fiber discs in order to utilize the light effectively as well as increase the amount of photocatalyst used for CO 2 reduction. The characterization of prepared Cu/TiO 2 film coated on netlike glass fiber was analyzed by SEM, EPMA, TEM and EELS. Furthermore, the CO 2 reduction performance of Cu/TiO 2 film was tested under illumination of Xe lamp with or without ultraviolet (UV) light, respectively. As a result, the best CO 2 reduction performance has been achieved under the condition of CO 2 /H 2 /H 2 O = 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/TiO 2 overlapped is 1.4 times as large as that for single Cu/TiO 2 , while the highest concentration of CH 4 for Cu/TiO 2 overlapped is 1.7 times as that for single Cu/TiO 2 . Under the illumination condition without UV light, the highest molar quality of CO per weight of photocatalyst for Cu/TiO 2 overlapped is 1.1 times as that for single Cu/TiO 2 . The theoretical molar ratio of CO 2 /H 2 O or CO 2 /H 2 to produce CO is 1:1, while the theoretical molar ratio of CO 2 /H 2 O or CO 2 /H 2 to produce CH 4 is 1:4. Since the molar ratio of CO 2 /H 2 /H 2 O = 1:0.5:0.5 can be regarded as the molar ratio of CO 2 /total reductants = 1:1, it is believed that the results of this study follow the reaction schemes of CO 2 /H 2 O and CO 2 /H 2 .