**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 or NH3 was investigated. In addition, the overlapping two Cu/TiO2 coated on netlike glass discs were also investigated. The CO2 reduction performance of Cu/TiO2 film was tested under illumination of Xe lamp with or without ultraviolet (UV) light, respectively. As to the condition of CO2/H2/H2O, 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. The theoretical molar ratio of CO2/H2O or CO2/H2 to produce CO is 1:1. 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 scheme of CO2/H2O and CO2/H2. On the other hand, as to the condition of CO2/NH3/H2O, the best CO2 reduction performance has been achieved under the condition of CO2/H2/ H2O = 1:1:1 with UV light illumination as well as without UV light illumination.

**Keywords:** CO2 reduction, Cu/TiO2 photocatalyst, reductants combination, visible light, overlapping effect
