Sea Urchin-like TiO₂ Based Photocatalysts For Efficient Reduction Of Carbon Dioxide

The development of high-performance photocatalytic CO₂ reduction catalysts is of great significance to alleviate the energy crisis and global warming.Among many photocatalysts,TiO₂has received extensive research and attention due to its stable performance,safety,non-toxicity,and low cost.The photocatalytic reduction of CO₂ to hydrocarbons is still challenging due to the sluggish kinetics and the requirement for the rich electrons.In this thesis,the sea urchin-like TiO₂based photocatalysts were prepared and applied in photocatalytic CO₂ reduction to produce hydrocarbons.Firstly,a sea urchin-like TiO₂ photocatalyst with Ti³⁺defects was synthesized using Ti B₂ as a precursor in a mixed aqueous solution of HCl and Na₂SO₄.The results show that the sea urchin-like TiO₂ is rutile,assembled from nanorods which have a tip with a diameter of about 15nm,and a length of about 2μm.In the photocatalytic CO₂ reduction,the results show that the products of CO₂ reduction are mainly CO,with a small quantity of CH₄,and the yields of CO and CH₄ achieved209.3μmol·g^-1 and 42μmol·g^-1,respectively.Therefore,compared to bulk TiO₂,sea urchin-like TiO₂ exhibited good photocatalytic performance for CO and CH₄,which should be ascribed to its strong light absorption,fast separation of electrons and holes due to the unique sea urchin structure,and the improved adsorption and activation of CO₂due to the Ti³⁺defects.In addition,the metals Pt（Au,Cu）as the co-catalyst was loaded on the sea urchin-like TiO₂respectively for promoting the production of hydrocarbons from CO₂ reduction.Among these,3%Pt/TiO₂ catalyst exhibited the most remarkable improvement.Pt nanoparticles with an average size of 4 nm grow uniformly on the nanorods of the sea urchin structure.As a result,CO and CH₄outputs were as high as 581 mol·g^-1 and 75.4μmol·g^-1,respectively.More importantly,it can also promote the photoreduction of CO₂ to produce C₂hydrocarbon products（C₂H₄,C₂H₆,C₃H₈）.It is revealed that Pt modification on the TiO₂ effectively enhanced the visible light response capability,and the transfer capability of the photogenerated electrons to Pt.Therefore,besides the advantageous effects of the sea urchin-like structure and Ti³⁺defects,the enrichment of electrons on Pt could account for the increased production of CH₄ and C₂ hydrocarbons.