The Controllable Construction And Photocatalytic Properties Of Nano-Octahedral CdIn₂S₄-Based Nanocomposites

With the rapid development of the world economy,environmental pollution and energy crisis are becoming two of the most serious problems,which affect human health and hinder sustainable development.Thus,exploring a renewable eco-friendly and cost-effective alternative energy and highly efficient technology for water purification are urgently required.Currently,semiconductor-based photocatalysis,as one of the most promising strategies to solve these two issues,has obtained great attention.To expedite the advancement of photocatalysis,great efforts have been devoted to design highly-efficient and visible-light-driven photocatalysts with superior photostability.Among these,ternary metal sulfide has attracted worldwide research interest due to its unique electronic structure and excellent photoelectric properties.CdIn₂S₄,as one of the ternary sulfides,its superior physicochemical stability,narrow bandgap and suitable band edge potentials endow it with excellent prospects.However,the research towards this material is still limited at present.Meanwhile,the high electron-hole recombination rate greatly hinders its practical applications.Thus,it is of practical significance to adopt feasible strategies to modify CdIn₂S₄ for enhancing its photocatalytic performance.Here,novel CdIn₂S₄ octahedra with unique nanostructure and several CdIn₂S₄-based hybrid heterostructures were designed and developed via some facile synthetic methods.The morphology,microstructure and optical properties of CdIn₂S₄-based photocatalysts were measured by a series of techniques.Photocatalytic water spitting for hydrogen evolution or photodegradation were adopted to systematically evaluate the photocatalytic performance and photostability of as-obtained photocatalysts.Finally,the interface charge transfer path and possible reaction mechanism were revealed.The main research contents were listed as follows:1.The 3D CdIn₂S₄ nano-octahedron/2D ZnO nanosheet heterojunctions?CIS/ZO-x?were firstly fabricated via a facile and green impregnation-hydrothermal method,where three-dimensional?3D?CdIn₂S₄ nano-octahedrons densely anchor onto the both sides of 2D ZnO nanosheets to form an embedded nanostructure with intimately interfacial contacts.Various characterization techniques were adopted to measure the morphologies,structures and optical properties of as-prepared CIS/ZO-x heterojunctions in detail.The photocatalytic performance of the as-prepared CIS/ZO-x was evaluated via the photodegradation of Tetracycline hydrochloride?TCH?under visible light irradiation,and the result shows that the hybridization of ZnO nanosheets with CdIn₂S₄ nano-octahedrons significantly enhances the photocatalytic activity of heterojunction.The high stable and reusable sample CIS/ZO-2 possesses the highest photocatalytic activity?94.04%?.Interesting,the removal efficiency of TCH and the rate constant are much higher than those of numerous previously reported composite photocatalysts.The synergistic effect and the unique 3D/2D hybrid structure with intimately interfacial contacts are primarily responsible for the enhanced photocatalytic activity.A possible photocatalytic mechanism for the TCH photodegrdation over CIS/ZO sample is also proposed.2.The novel CdIn₂S₄/TiO₂?CIS/THS?hollow composite photocatalyst was firstly designed and synthesized via a facile in-situ growth process,where the CdIn₂S₄ nano-octahedra densely attached on the surface of TiO₂ hollow spheres to form the unique hybrid heterostructure.The as-synthesized CIS/THS heterojunctions exhibit much superior photocatalytic activities for hydrogen evolution and Methyl Orange?MO?decomposition in comparison to pure CdIn₂S₄ and TiO₂ hollow spheres.The experimental results display that the CIS/THS-3 sample with the 30 wt.%of TiO₂presents the optimal photocatalytic performance.The enhanced photocatalytic activities can be assigned to the synergistic effect,optimized light-harvesting capacity and the formation of hybrid heterostructure for boosting interfacial charge transfer and separation.Furthermore,based on the trapping results and ESR analysis,the possible type-?interface charge transport mechanism also was proposed.3.The novel core-shell CdIn₂S₄/Ta₃N₅?CIS/TN?nanocomposite photocatalyst was designed and successfully fabricated via the facile in-situ hydrothermal process.The as-prepared CIS/TN heterostructures all showed high dual-functional photocatalytic performances for H₂ generation and Methyl Orange?MO?decomposition.The sample CIS/TN-3 with the 3 wt.%of Ta₃N₅ possessed the highest H₂ production of 122.6?mol·h^-1·g^-1,which was about 2.43 times as high as that of CdIn₂S₄ nano-octahedra.Also,it presented the optimal MO photodegradation efficiency?92.2%?and its rate constant was 2.79 times higher than that of pure CdIn₂S₄.Besides,the as-prepared hybrid also possesses superior photostability and repeatability.On the basis of experimental results and analysis,the wonderful dual-functional photocatalytic performance could be attributed to the broad spectral adsorption region and efficient transfer of photoinduced charge carriers between the intimate heterogeneous interface.