Two-Dimensional Matched Organic Semiconductor-TiO₂ Nanoheterostructure Construction And Photocatalytic CO₂ Reduction Performance

The conversion of CO₂into high value-added fuels and chemicals using solar energy as the driving force for photocatalysis is one of the ideal ways to solve current energy and environmental problems.Therefore,there is an urgent need to develop new photocatalytic systems with high CO₂reduction performance TiO₂materials have been widely studied as a typical semiconductor photocatalytic material,but they still have disadvantages such as poor photogenerated charge separation,low photoavailability,and lack of catalytic sites.In this thesis,we propose to prepare ultra-thin two-dimensional TiO₂nanosheets and construct dimensionally matched heterojunction photocatalytic materials with two-dimensional organic semiconductor materials to promote photogenerated charge separation,expand the visible light response of TiO₂and enhance the efficiency of catalytic reduction reaction to achieve a highly active CO₂reduction conversion process,and reveal the mechanism of photogenerated charge separation and catalytic process.Firstly,ultra-thin TiO₂nanosheets were prepared by a one-step hydrothermal method,and then the physically encapsulated Ionic liquid（IL）porous graphic carbon nitride（PCN）and TiO₂nanosheets were assembled by a hydroxyl-induced assembly method to form two-dimensional matched nanoheterojunctions.The two-dimensional structure increases the interfacial contact area and shortens the photogenerated charge transfer distance to facilitate the interfacial photogenerated charge transfer,and the IL is introduced to further promote the charge separation by modulating the electrons.In addition,the imidazole cation in IL can effectively adsorb and activate CO₂to enhance the catalytic reaction efficiency.The best IL-PCN/TiO₂photocatalytic CO yield reaches 22.8μmol g^-1h^-1,which achieves a 6-fold performance improvement compared with TiO₂nanosheets.Next,a new two-dimensional matched heterojunction（Zn Pc/TiO₂）was constructed by self-assembly of zinc phthalocyanine（Zn Pc）and TiO₂nanosheets.Subsequently,Au nanoparticles were modified on the TiO₂surface to promote the dispersion of Zn Pc by the coordination between Au and N in phthalocyanine molecules,which further enhanced the optimal loading of Zn Pc to expand visible light absorption,promote charge separation and expose more single-atom Zn-N₄catalytic centers.The optimal loading of Zn Pc/Au-TiO₂material system achieved a CO yield of 37.4μmol g^-1h^-1under all-light conditions with a 10-fold improvement in performance compared with TiO₂nanosheets.