Study On Preparation And Photocatalytic Performance In CO₂ Reduction Of Defective TiO₂ Heterojunction Material Derived From TiB₂

In modern society,the energy crisis and global warming have been two serious issues for human beings to face,the development of high-performance photocatalytic CO₂ reduction catalyst is of great significance to alleviate these two problems at the same time.Among various photocatalysts,TiO₂ received extensive research and attention owing to its unique characteristics,such as chemical inertness,non-toxicity,and low cost.Recent studies have found that Ti³⁺defects in TiO₂ can promote the utilization of visible light.In addition,the Ti³⁺defects on the surface of the photocatalyst are also conducive to the adsorption of CO₂,H₂O and other reactants on its surface,thereby promoting the progress of the photocatalytic reaction.However,the current construction of Ti³⁺defects in TiO₂ often involves complex high-temperature reduction and other treatment processes.In this study,TiB₂ was used as a precursor to synthesize Ti³⁺deficient TiO₂ with different morphologies,and then modified with Sn S₂ to form a heterostructure.The photocatalytic CO evolution performance under full light and visible light were also studied.Using TiB₂ as the precursor and HF aqueous solution as the morphology control reagent,a deep blue Ti³⁺defective TiO₂ nanosheet TiO₂-B was synthesized by hydrothermal method.As a control sample,white TiO₂ nanosheets TiO₂-W were obtained by high-temperature oxidation of TiO₂-B.Furthermore,two heterojunction catalysts Sn S₂/TiO₂-B and Sn S₂/TiO₂-W were constructed by combining TiO₂-B and TiO₂-W with Sn S₂,respectively.The results show that both TiO₂-B and TiO₂-W are anatase,having a truncated double-cone morphology that exposes only the{001}and{101}crystal planes,forming a surface heterojunction.Compared with TiO₂-W,TiO₂-B,which contains a lot of Ti³⁺defects,shows excellent visible light absorption performance,but still does not have a good charge transfer ability.Sn S₂/TiO₂-B,modified by Sn S₂,not only has excellent light absorption performance but also has the best photo-generated charge separation ability,and therefore shows the best photocatalytic CO₂ reduction performance.Under visible light,with Sn S₂/TiO₂-B as a catalyst,the CO generation rate is 58μmol?h^-1?g^-1,which is 2 and 19 times that of TiO₂-B and Sn S₂,respectively.The results show that the charge transport at the interface between TiO₂-B and Sn S₂ in the heterojunction catalyst Sn S₂/TiO₂-B conforms to the Z-type electron transfer mechanism.Using TiB₂ as a precursor and a mixed aqueous solution of HCl and Na₂SO₄ as a morphology control reagent,Ti³⁺defective sea urchin-like TiO₂-G was synthesized,followed by Sn S₂ loading on TiO₂-G,and three heterojunctions with different loadings were synthesized:Sn S₂-5/TiO₂-G,Sn S₂-15/TiO₂-G and Sn S₂-25/TiO₂-G.The results show that the sea urchin-shaped TiO₂-G is rutile,and is composed of tipped nanorods with a diameter of about 35 nm and a length of about 2μm.In heterojunction catalysts,Sn S₂ grows uniformly on the surface of TiO₂ nanorods.As the loading of Sn S₂ increases,the distribution of Sn S₂ nanosheets on the surface of TiO₂-G nanorods changes from monodisperse to large-scale aggregate coverage.The construction of Sn S₂-X/TiO₂-G heterojunction effectively improves the visible light absorption ability and photogenerated carrier transfer ability of TiO₂-G.When the loading of Sn S₂ is 15%,the heterojunction catalyst exhibits the best photocatalytic performance,and the CO yields in the full light range and the visible light range are729μmol?g^-1?h^-1 and 73μmol?g^-1?h^-1,respectively,and has good cycle stability.