Cu/CeO₂-TiO₂（B） With Oxygen Vacancies For Efficient Visible-light Photocatalytic Reduction Of CO₂

At present,photocatalytic reduction of CO₂ developed by artificial photosynthesis has attracted much attention,because it can convert CO₂ into CO,CH₄ and other clean fuels using sustainable green solar energy.TiO₂ has been used as a photocatalyst to reduce CO₂ because of its good stability,low economic cost,suitable position of the VB and CB,non-toxic,easy preparation and other advantages.However,the shortcomings of TiO₂,such as low light utilization caused by its bandgap,low carrier separation efficiency,and weak CO₂adsorption capacity,limit its photocatalytic efficiency.A variety of modification technologies can make up for the deficiency of TiO₂,among which morphology control,defect engineering and cocatalyst loading are three common methods.TiO₂（B）of 3D nano-flower has a[010]channel that can promote the diffusion of small molecules and facilitate electronic transmission.It has a large specific surface area that can provide rich reaction sites.The high surface energy of the（010）face can facilitate the formation of oxygen vacancies,thus improving the photocatalytic activity.The construction of defects on TiO₂（B）can control band structure,broaden the light absorption to the visible light region,and improve the solar light utilization.The cocatalyst Cu is rich in resources and economic cost is low.Schottky junction can be formed between Cu and TiO₂（B）to promote charge separation and Cu acted as the active center to adsorb and activate CO₂.CeO₂ can promote the dispersion of Cu on TiO₂（B）,promote the adsorption and activation of CO₂,and reduce the reaction energy barrier.Therefore,in order to improve the photocatalytic performance of TiO₂（B）,we designed and synthesized TiO₂（B）nanoflowers assembly incorporated with oxygen vacancy,Cu and CeO₂ for CO₂photoreduction.We explored the effects of oxygen defects,Cu and CeO₂ on the photocatalytic reduction of CO₂ by TiO₂（B）nanoflowers and researched the reaction mechanism.It is mainly divided into the following two parts:（1）Visible-light catalytic reduction of CO₂ on Cu-TiO₂（B）with oxygen vacancy.TiO₂（B）（TB）nanoflowers were prepared by hydrothermal method using Ti Cl₃.The UV light induced TB to produce oxygen vacancy,the Cu TB-1.5 nanoflowers containing both oxygen vacancy and Cu were prepared by the photoreduction method.they have been successfully synthesized,and TB is nanoflowers about 100 nm.Oxygen defects can broaden the light absorption of TB to the visible light region,and Cu can promote the transfer of photogenerated electrons on TB and act as the active center.Both Oxygen defects and Cu can promote the photogenerated charge separation efficiency of TB.The yields of CO and CH₄ of Cu₁TB-1.5under visible light are 5.72 and 0.02μmol·g^-1·h^-1,in which CO is 15.5 times of TB,selectivity is 99.6%,and has good stability.Both oxygen vacancy and Cu are conducive to the adsorption of CO₂ by TB,and the formation of reaction intermediate COOH*,and then the formation of CO.（2）Visible-light catalytic reduction of CO₂ on Cu/CeO₂-TiO₂（B）with oxygen vacancy.CeO₂-TiO₂（B）was prepared by water bath using Ce（NO₃）₃ as the precursor,and Cu Ce TB-1.5 with oxygen vacancy was prepared by photoreduction method.CeO₂ was successfully introduced without changing the structure and morphology of Cu₁TB-1.5,and CeO₂ could promote the dispersion of Cu on the surface of TB.CeO₂ can further promote the separation of Cu₁TB-1.5 photogenerated charges,enhance the adsorption of CO₂,and promote the activation and conversion of CO₂.The CO and CH₄yields of Cu₁Ce₂TB-1.5 under visible light are 8.39 and 0.04μmol·g^-1·h^-1.Among them,the yield of CO is 22.7 times of TB and 1.47 times of Cu₁TB-1.5 respectively,and the selectivity is up to 99.5%.In the process of photocatalysis,CeO₂ can promote the adsorption and activation of CO₂ on the catalyst,and generate CO and CH₄ through reaction intermediates COOH*and·CH₃ respectively.