Study Of Ru Polypyridyl Complex-TiO₂-Cu Assembly And Its Visible Light CO₂ Photoreduction Property

With the rapid development of social economy,the excessive consumption of fossil energy has caused a large amount of carbon dioxide emissions,leading to a global energy and environmental crisis.To solve this problem,scientists have proposed“artificial light synthesis”with an aim to convert carbon dioxide and water into hydrocarbons or hydrogen.However,the practical application of solar photocatalytic reduction of carbon dioxide is restricted by the wide band gap of semiconductors,the high recombination efficiency of photo-generated carrier and the poor CO₂ activation ability.The polypyridyl complex of ruthenium{[Ru（bpy）₂(4,4′-（PO₃H₂）₂bpy]（Br）₂,RuP}is commonly employed as light absorbers to photosensitize catalysts for the effective utilization of solar light.Cu compounds possess good CO₂ activation ability and good multielectron transfer properties.TiO₂ can be used as substrates,and their conduction bands can also be used as mediators for the photoinduced electron transfer process.Herein,we build a well-designed bridge-like nanostructure,RuP light absorber-TiO₂ bridge-Cu catalyst.And it exhibits superior CO₂ photoreduction activity.The main results and conclusions are as follows:1.The well-designed nanostructure RuP-TiO₂-Cu catalyst was synthesized.The investigation in electron transfers shows that the photoexcited electrons were generated by the light absorber RuP and then migrated to the conduction band of TiO₂and finnally trapped on the Cu surface,in the meantime,the photogenerated holes were left in RuP.Therefore,the electron and hole can be separated effectively,the RuP-TiO₂-Cu assembly exhibits superior CO₂ photoreduction activity under visible light irradiation（λ>420 nm）.2.The relationship of the TiO₂ band structure and the visible light CO₂photoreduction activity of RuP-TiO₂-Cu was systematically investigated.The results suggested that RuP-T₁-Cu with lower conduction band of T₁ has a higher electron transfer rate under visible light irradiation.In other words,the electronic structure of the mediator TiO₂ influences the electron transfer of RuP-TiO₂-Cu,which further has an influence on the CO₂ photoreduction activity of the complex.In this work,Brookite TiO₂ was adopted as a bridge in improving the charge separation of the RuP（light absorber）-Cu（catalyst）assembly in the visible light-driven CO₂photoreduction process.The electronic band structure of brookite TiO₂ influences the electron movement transfer.Given its effective charge separation,this RuP-TiO₂-Cu assembly exhibits superior CO₂ photoreduction activity under visible light irradiation.This study provides a facile and general approach toward an efficient artificial photosynthesis.