Abstract: Photocatalytic reduction of CO_2 is a challenging renewable energy production technology.However,due to the rapid recombination of photogenerated electron hole pairs and the limited utilization of visible light,TiO_2 shows low photocatalytic reaction efficiency.In order to improve the efficiency of photocatalytic reduction of CO_2 by Ti O_2,it is an effective way to modify TiO_2 by metal.In this paper,Pt and Cu_2O nanoparticles were co-deposited on the surface of TiO_2 nanocrystals by chemical reduction method.The influence of Pt and Cu co-modification on the photocatalytic reduction of CO_2 by Ti O_2 was systematically studied.The experimental results show that Pt deposition tends to promote the production of CH_4 and H_2.However,Cu_2O can suppress H2 production and exhibites lower CH_4 selectivity than that of Pt.Furthermore,after co-deposition of Pt and Cu_2O on Ti O_2 crystal,the formation of H_2 is inhibited,and CO_2 is selectively converted to CH_4,with a selectivity of 96.6%.The characterization experiments and a series of photocatalytic reduction selectivity experiments show that Pt can not only capture the photogenerated electrons,but also improve the electron density on the catalyst,which is conducive to the multi-electron reduction reaction and the formation of CH_4 with high selectivity.Cu_2O enhances the chemical adsorption of CO_2 on TiO_2 and inhibites the adsorption of water,thus the formation of H_2 is inhibited and the selectivity of photogenerated electrons for CO_2 reduction is improved.In addition,Cu_2O in Pt-Cu/TiO_2 after the reaction is almost completely reduced to Cu,which may be caused by the process of photocatalytic reaction,Pt deposition can promote the transfer of photogenerated electrons to Cu_2O. This phenomenon can provide more electrons for the photocatalytic reduction while reducing Cu_2O to zero valent Cu,which is conducive to the selective generation of CH_4.Therefore,Pt-Cu/TiO_2 catalyst can selectively reduce CO_2 to CH_4.After three cycles of tests,the activity of the catalyst is not reduced and has good stability.