| Silicate materials have been widely used in adsorption, catalysis, durg delivery and other fields because of their simple preparation, rich source, cheap price, and unique porous structure. But some insintric disadvantages such as poor electrical conductivity limit their application. Therefore, this project aims at improving the performance of silicate materials through the design of composite system and programmed synthesis of hierarchical nanostructure with different dimensionalities. The results show that synergistic effect of silicate and carbon component greatly enhance the adsorption, electrochemical, and photocatalytic performance.1. One-dimensional coaxial structured nickel silicate @ carbon nanotube composite was synthesized using carbon nanotubes as physical templates and conductive agent, and the electrochemcial performance of the nanostructure as lithium ion battery anode was studied. Layered nickel silicate exhitbits a large layer spacing of 0.74 nm, which could accomodate the intercalation and deintercalation of not only lithium ions, but also sodium ions. Carbon nanotubes improve the electroical conductivity of the composite and benifit the electrons and ions diffusion; the hollow tubular structure could also accomodate the volume change caused by the insertion and extraction of lithium ions during the charge and discharge process, thus improving the cycling stability. The discharge capacity of coaxial nickel silicate @ carbon nanotube composite remains at 489 mA h/g after 50 cycles at current density of 50 mA/g, which is nearly four times than that of pure nickel silicate nanotube (107 mA h/g).2. Two-dimensional sandwich structured magnesium silicate/ graphene oxide composite was prepared by hydrothermal method, and the adsorption performance of organic dyes and heavy metal ions was investigated. The composite material exhibits high BET specific surface area of of 450 m2/g. The adsorption isotherm of methylene blue and lead ion fits Langmuir adsorption model, and the maximum adsorption capacities are 424 and 416 mg/g respectively, which are 271% and 126% higher than that of pure magnesium silicate. Graphene oxide not only serve as supporting matrix for the well dispersion of magnesium silicate nanoplates to improve the specific surface area of the composite; the abundant oxygen containing functional groups of graphene oxide also provides more adsorption site. Moreover, the micro-scale size of the compostie improve the good separabiltiy under gravity.3. Three-dimensional core-shell structured magnesium oxide @ mesoporous silica composite was prepared a two-step method, and the adsorption performance of organic dyes and heavy metal ions was studied. The composite material exhibits high BET specific surface area of 567 m2/g. The mesoporous silica shell not only improves the mechanical stability of the magnesium oxide and prevent the structural damage during mechanical stirring process, but also provide concentration gradient to enhance the mass transfer effect and improved adsorption performance. The maximum adsorption capacities of magnesium oxide @ mesoporous silica for lead ion and methylene blue were 3155 mg/g and 420 mg/g, respetively, which is much higher thant the 2454 mg/g and 61 mg/g of pure metal silicate.4. Carbon nanotube (CNT) @ Silver silicate (AgSiOx) and graphene oxide (GO) @ AgSiOx composites was prepared wth enhanced visible light photodegradation performance of methyl blue than that of pure AgSiOx. However, the influence of CNT or GO content on the improvement efficiency is different. The photodegradation efficiency of AgSiOx@CNT first increases and then decreases with the increase of CNT content; while the removal efficiency of pollutant by AgSiOx@GO increases with the increase of GO content owing to its high oxygen-containing functional groups. Therefore, AgSiOx@CNT shows better removal efficiency than that of AgSiOx@GO at low carbon phase content and AgSiOx@GO shows better removal efficiency than that of AgSiOx@CNT at high carbon phase content. |
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