Photocatalytic reduction of CO₂ with H₂O vapor on TiO₂  has attracted more attention because it is a promising “green chemistry” way for the direct conversion of CO₂ to value-added fuels (CO, methane, methanol, etc.) driven by sunlight. However, the drawback in weak interaction between TiO₂ and CO₂ molecules limited CO₂ photoreduction.  

A research team led by Prof. WANG Chuanyi at Xinjiang Technical Institute of Physics & Chemistry of Chinese Academy of Sciences employed ceria as a basic promoter to strengthen the interaction of CO₂ with photocatalyst surface and fabricated highly dispersed CeO₂/TiO₂ and bare TiO₂ catalysts.  

Researchers prepared highly dispersed CeO₂ on TiO₂ catalysts by a one-pot hydrothermal method using titanium (IV) bis (ammonium lactate) dihydroxides as Ti source and Ce(NO₃)₃？6H₂O as Ce source, respectively. They found the presence of CeO_2-x and ceria？titania interfaces in CeO_2-x/TiO₂ catalysts strengthens the bonding of CO₂ with catalyst surfaces and increases the production of b-CO₃^2？ and b-HCO₃^？ species. The process was different from m-CO₃^2？, b-CO₃^2？ and b-HCO₃^？ surface species, which could be easily transformed to surface CO₂^？ in the presence of H₂O under simulated sunlight irradiation. 

Based on the microcalorimetric measurement and in situ infrared spectroscopy (IR), the results showed that the strengths and states of CO₂ adsorption and the course of photoreduction of CO₂ with H₂O vapor.  

The research team proposed for the first time experimentally that  the surface CO₂^？ species is derived from b-CO₃^2？ and b-HCO₃^？ but not from gaseous and physisorbed CO₂ molecules. 

The study deepens the understanding of the role of ceria in CO₂ photoreduction at TiO₂ catalysts and the course of catalysis of CO₂ photoreduction in the presence of H₂O vapor. It has been published in Journal of Catalysis.  

The work was supported by the National Nature Science Foundation of China, the CAS Hundred Talent Program, the CAS-SAFEA International Partnership Program for Creative Research Teams, etc. 

Figure: A scheme of route for CO₂ photoreduction with H₂O vapor (Image by XTIPC)