Synthesis And Photocatalytic Performance Of Discrete Indium-based Metal Chalcogenide Nanoclusters

Metal chalcogenides have attracted great attention for their visible-light-induced photocatalytic activity.Compared with metal chalcogenide nanomaterials,crystalline metal chalcogenides used as photocatalytic materials have been relatively less studied.Supertetrahedral metal chalcogenide clusters（typically Tn,Pn and Cn）have attracted much attention because of their regular structure,adjustable composition,and outstanding properties.In general,metal chalcogenides Tn clusters tend to form extended structures via corner-sharing chalcogen sites.By contrast,discrete chalcogenide Tn clusters are far less explored,especially for selenides.Prior to this work,the largest reported Tn selenide clusters were still T4 clusters.Highly dispersed metal chalcogenides Tn clusters with high specific surface area and precise composition can be regarded as the smallest quantum dots.Its unique advantages can provide an ideal model for investigating the structure-photocatalytic property relationship.In this thesis,one discrete T3 selenium and six heterometallic T5 selenides（inclduing their Se/S solid solutions）,namely,[Bmmim]₆[In₁₀Se₁₆Cl₄]?（MIm）₂（2-1）（Bmmim=1-butyl-2,3-dimethylimidazolium,MIm=1-methylimidazole）,[Bmmim]₁₂[Cu₅In₃₀Q₅₂Cl₃（Im）](Q=Se（3-1）,Se_48.5S_3.5（3-2）,Im=imidazole),[Bmmim]₁₁[Cd₆In₂₈Q₅₂Cl₃（MIm）](Q=Se（3-3）,Se_28.5S_23.5（3-4）,Se₁₆S₃₆（3-5）),and[Bmmim]₉[Cd₆In₂₈Se₈S₄₄Cl（MIm）₃]（3-6）,have been solvothermally synthesized by a two-step method,in which the IL acts as a reactive solvent and stabilizer.Among them,2-1 could be stably dispersed in dimethylsulfoxide（DMSO）.The solution of 2-1 exhibited much higher photocatalytic hydrogen evolution（～6.5 times）than that in the solid state.3-1 and 3-3 represent the first metal selenides constructed from supertetrahedral T5 clusters.Cu-In-Q based compounds 3-1 and 3-2 exhibited visible light photodegradation of organic dye（crystal violet）,while Cd-In-Q based compounds3-3-3-6 displayed photocatalytic H₂evolution properties with significantly improved efficiencies with the increase of sulfur content in these solid solutions.In addition,the reported T4 cluster[Bmmim]₉[Cd₃In₁₇Se₃₁Cl₄]·（4,4’-bipy）was utilized as the photosensitizer to be combined with Ti O₂.The resultant composite showed significantly improved hydrogen production performance compared with Ti O₂under visible light.The composites exhibited the highest hydrogen-producing activity(333.5μmol·h^-1·g^-1)when8 wt.%of T4 cluster as the photosensitizer was loaded.This is the first study on the effect of metal chalcogenide clusters as new photosensitizers on photocatalytic H₂production.The research presented in this thesis developed a series of discrete metal chalcogenide Tn clusters as photocatalytic materials or photosensitizers,which may provide certain guidance on exploring new efficient photocatalytic materials.