Controllable Preparation Of Hollow Micro-/Nanostructures And Their Applications In Environment And Energy

Environmental pollution and energy shortages are one of the great challenges in China and even the world.Development of advanced materials for envirornmental remediation and energy storage has provided new approaches for solving above problems.Hollow micro-/nanostructures with unique physicochemical prarea,low density,tunable inner cavity and good encapsulation ability,have show advantages operties,such as large specific surface in the applications of environmental remediation and energy storage.Because of the technical limitations in the field of hollow micro-/nanostructures such as complex synthesis processes,monotonous control strategies and lack of shaping technique,the aim of dissertation is to simplify the process,optimize the structure and property,clarify the relationship between property and performance and thus construct advanced materials with high catalytic activity,large capacity and excellent stability for environmental remediation and energy storage.The reaserch has been focused on the controllable synthesis of hollow micro-/nanostructures and the relationships between property and performance of applications in pollutant degradation/detection and energy storage.The main conclusions are as follows:(1)Several novel syntheitic strategies have been developed to sequentially simpify the fabrication process,optimize the structure and improve the electrochemical performace.Based on the previous Stober-carbon and silica/carbon systems,three kinds of formation mechanisms,including melamine modified silica/carbon assembly,amine induced silica/carbon assembly and surfactant-free based self-assembly are proposed by adjusting surfactant,carbon precursor,caralyst et al.On this basis,serveral kinds of porous carbon materials including N-doped single-shell hollow carbon spheres,yolk-shell hollow carbon spheres,and double-shells hollow carbon spheres have been synthesized,which possess good dispersibility,uniform morphology,large surface area(up to 2464m2 g-1),high pore volume(up to 2.36 cm3 g-1)and nitrogen content(up to 6.3%).Electrochemical test results demonstrate that N-doped double-shells hollow carbon spheres show the best supercapacitor performance.At the current density of 1 A g-1,the specific capacity is high up to 380 F g-1,which is larger to that of most reported porous carbons.(2)The inevitable inward contraction of metal-organic frameworks(MOFs)during carbonization process have significantly restrict the structural diversity of the obtained carbon materilas.Herein,we develop a rigid interface induced outward contraction process for fabraicating MOFs based hollow mesoporous carbon nnacubes(HMCNCs),which possess hollow c\vity.outer microporous shell and inner mesoporous framework,as well as large surface area(1085.7m2g-1),high porosity(3.77cm3 g-1)and nitrogen content(12.2%).By desinging the interface-free and soft-interface systems and model construction,we directly prove the induced role of rigid interface during the carbonization process.Moreover,When used as a cathode material for Li-SeS2 batteries,the HMCNCs deliver a stable capacity and an outstanding rate capability.(3)We extend the two-solvents method from two dimensional mesoporous silica to zero dimensional hollow mesoporous silica sphere for the preparation of Fe0@SiO2 and Ag@SiO2 yolk-shell nanoreactors(YSNs).Chracterization results indicate that the as-sytheszied YSNs possess active cores,accessible mesoporous channels,protective shells and hollow cavities.To show the structure-enhanced effect of YSNs,the FeO@SiO2and Ag@SiO2YSNs are used as catalysts for degradation of phenol in Fenton oxidation and sensor materials for detection of hydrogen peroxide,respectively,which possess remarkable performances.Furthermore,a series of control samples are designed which further clarify the confined catalysis mechamisn of YSNs,paving new ways for development and application of novel YSNs.(4)The functional carbon materials(e.g.hollow mesoporous carbon spheres and MOFs based carbon)are creatively introduced into the electrospinning process and further synthesize three kinds of novel composite carbon fibers,including mulberry-like N-doped hollow mesoporous carbon spheres fiber,mulberry-like Fe/N co-doped hollow mesoporous carbon spheres fiber and Co/N co-doped hierarchical carbon fiber.Chracterization results indicate that the resultant fibers have successfully integrate the merits of HMCSs(i.e.high surface area and micro-meso-macropores)and carbon fibers(i.e.large aspect ratio,high conductivity,and favorable flexibility).Electrochemical test results demonstrate that the composit fibers show superior supercapacitor and oxygen reduction reaction performance than the hollow mesoporous carbon spheres or MOFs-based carbon materials and blank carbon fibers.We systematically explore the electrochemical enhanced-effect of one dimensional modularization,which will provide theoretical foundations for construction and application of functional hierarchical porous carbon fiber.