Preparation And Photocatalytic Performance Of Ultra-thin Mesoporous Black TiO₂ Nanosheets And Their Composites

Two-dimensional TiO₂ nanosheets have high specific surface area,abundant surface active sites and short transport distance of photogenerated carriers,showing favorable photocatalytic performance,and are also excellent hosts for building heterojunction composite materials.However,due to its wide band gap,anatase TiO₂can only absorb ultraviolet light,which limits the utilization of sunlight.In addition,the lower efficiency of photogenerated charge separation significantly limits the improvement of photocatalytic performance.Based on this,we demonstrate the synthesis of 2D ultrathin mesoporous anatase TiO₂ nanosheets with surface defects,which are synthesized by a strategy of evaporation-induced self-assembly,solvothermal and high-temperature surface hydrogenation methods.After surface hydrogenation,the band gap becomes narrow and the light response range is extended to visible light region.As the host,the composite materials are constructed to further improve the efficiency of photocharge separation and photocatalytic performance.In this paper,the relationship between the preparation of ultrathin mesoporous black TiO₂ nanosheets and their complexes and the photocatalytic performance are studied.The main contents are divided into the following three aspects:1.2D ultrathin mesoporous anatase TiO₂ nanosheets with surface defects are prepared by evaporation-induced self-assembly,solvothermal and high-temperature surface hydrogenation methods?SDUATNs?.The thickness of nanosheet is 6 nm and this ultrathin structure is conducive to the diffusion and transmission of photogenerated carriers.The existence of surface defects reduces the band gap to 2.97 e V,extends the light response range to visible light region,and improves the separation efficiency of photogenerated electron hole pairs,thus promoting the photocatalytic hydrogen production performance.The photocatalytic hydrogen production for the SDUATNs is about 3.73 mmol h^-1 g^-1,which is appropriately 3 times higher than that of pristine white TiO₂ nanosheets(1.31 mmol h^-1 g^-1).This excellent performance is attributed to the fast electron transport channels and mesoporous structure with large specific surface area of two-dimensional ultrathin nanomaterials,which provide abundant surface active sites.2.Using ultrathin mesoporous anatase black TiO₂ nanosheets as host materials,Pt nanoparticles/ultrathin mesoporous anatase black TiO₂ nanosheets nanocomposites?Pt-SDUATNs?are prepared by ultrasonic impregnation,liquid nitrogen freezing and in-situ photoreduction.The uniform size of Pt nanoparticles is closely coupled on the surface of the defective TiO₂ nanosheets,which is conducive to the transfer of photogenerated electrons to Pt as a cocatalyst,thus improving the efficiency of photocatalytic hydrogen production.Pt-SDUATNs catalyst has favorable visible light absorption?2.66 e V?and excellent photocatalytic hydrogen production performance(6.15 mmol h^-1 g^-1),which is about 1.7 times higher than that of SDUATNs.The photocatalytic hydrogen production performance of 0.2%loaded monodisperse Pt nanoparticles is much better than that of 0.5%H₂PtCl₆ solution,which greatly improves the utilization of Pt as a cocatalyst.3.Using Pt nanoparticles/ultrathin mesoporous anatase black TiO₂ nanosheets as host materials,Cu nanoparticles/Pt nanoparticles/ultrathin mesoporous anatase black TiO₂ nanosheets nanocomposites?Cu-Pt-SDUATNs?are prepared by a strategy of ultrasonic wet impregnation and high-temperature surface hydrogenation reduction.Due to the surface plasmon resonance?SPR?effect of metal Cu,the complex expands the absorption of visible light,and further promotes the transport and separation of photo generated carriers by the synergistic effect between Pt nanoparticles and Cu nanoparticles,thus improving the separation efficiency of photo generated electron-hole pairs.Under the condition of simulated sunlight AM 1.5G,Cu-Pt-SDUATNs has favorable photocatalytic hydrogen production performance(8.51 mmol h^-1 g^-1),which is1.4 times higher than that of Pt-SDUATNs.This new synthesis strategy provides a new idea for the development of plasma photocatalytic composite materials for solar energy conversion,and has a potential application prospects in the field of clean energy.