Preparation And Photoelectric Properties Of Titanium-based Composite Nanomaterials

Since the 21st century,a fast-growing industry and the rising global population are the key factors contributing to the water pollution that causes intense carcinogenic toxicity to most organisms,which poses a serious threat to human life and ecosystem.Therefore,the development of renewable energy and the reduction of water pollution has become one of the most urgent social problem.Semiconductor photocatalytic materials can convert solar energy into electrochemical energy,and are widely used in the fields of environmental purification,photocatalytic hydrogen production and organic degradation.TiO₂ has attracted great attention among various semiconductor materials.Nevertheless,the wide band gap and severe charged carrier recombination ofTiO₂ result in a relatively low photocatalytic efficiency.Therefore,the synthesis of new visible-light responsive photocatalysts is of great important.On the basis of non-toxic and stable properties of titanium dioxide,titanium-based nanomaterials increase the light response range,reduce the compound efficiency of electron hole pairs and thus effectively improve their photocatalytic capacity.The main contents of the paper are as follows:1. A novel Z-scheme Bi₂MoO₆ nanosheets/TiO₂ nanosphere?BT?heterojunction in which numerous Bi₂Mo O₆ nanosheets uniformly grow on the surface of TiO₂ nanospheres was synthesized through a simple two-step hydrothermal process.The resulting heterostructures possess high surface areas and porous structures,providing abundant active sites for photocatalysis.The“line-to-surface”synergistic effect endow the Z-scheme heterojunction with high transfer efficiency of photogenerated carriers and increased electron lifetime for photodegradation.As a result,the as-made BT photocatalysts present super photocatalytic performance and excellent cyclic stability for the photodegradation of 4-nitrophenol in water than pure Bi₂Mo O₆ andTiO₂.2. A hierarchical heterostructure of CoTiO₃@NiO with well-defined core-shell among which longitudinally aligned NiO nanosheets are in situ incorporated onto CoTiO₃ sub-microbelts was prepared via a combination of solution precipitation and calcination.Promoted photo-generated electron-hole separation efficiency and more active sites are achieved in the system through the profitable Z-scheme carrier transmission mechanism and special core-shell structure.The TC removal efficiency by the optimized CoTiO₃@NiO is 2.15 and 1.75 times of that for pure NiO and CoTiO₃respectively,proving that the resultant hierarchical core-shell CoTiO₃@NiO displays greatly improved photocatalytic efficiency compared with pristine CoTiO₃sub-microbelts and NiO nanoclusters.3. A three-dimensional popcorn-like TiO₂ mesoporous sphere with tunable Pt contents has been synthesized by a combination of hydrothermal process and chemical reduction.The Pt nanoparticle on theTiO₂ facilitates the collection and transfer of the photogenerated electrons originated from the mesoporousTiO₂.Density functional theory?DFT?calculated results further confirm the faster carries separation in Pt/TiO₂.The specific three-dimensional structure endows Pt/TiO₂ spheres with enhanced light scattering ability,a high surface area,and porous structure.As a consequence,the novel Pt/TiO₂ mesoporous spheres present multiple fold enhancement on the Rh B photodegradation efficiency compared with that of neatTiO₂,in which 1.0%Pt/TiO₂presents the highest photocatalytic activity.4. A CdS/MXene nanocomposite that CdS nanoparticles are uniformly grow on the surface of MXene was synthesized through a simple solvent-thermal method with DMSO as solvent.The obtained structure has a large specific surface area,which can effectively absorb pollutants and provide more active sites.Additionally,MXene as an efficient cocatalyst can promote the carrier transport and inhibit the composition of photogenerated electron holes of CdS.The result shows that the photocatalytic performance of the system can be significantly improved by loading CdS nanoparticles on Ti₃C₂ nanosheet and the composite structure has good cyclic stability.The photodegradation efficiency of TC reached 94.7% within 60 min.