Optimum reductants ratio for CO₂ reduction by overlapped Cu/TiO₂

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.