Controllable Synthesis Of Hierarchically Porous Silica And Carbon Microspheres By Dynamic Template Method And Applications

Hierarchically porous nanomaterials as a new type of porous materials developed in recent years.Unlike traditional single-porous materials,they have two or more pore structures,or contain multiple pore sizes at the same time.Due to the unique pore structure,the material has a large specific surface area,a high pore volume and a rich pore structure,good thermal stability and excellent physical and chemical stability.Recent years,hierarchically porous nanomaterials have been widely used in biomedicine,catalysis,environmental energy and other fields due to their excellent properties.Among many inorganic hierarchically porous nanomaterials,silicon-based materials and carbon-based materials have been widely studied and applied to many field due to their large specific surface area,good thermal stability and hydrothermal stability,and stable physical and chemical properties.At present,although some studies have reported the synthesis of silicon-based materials and carbon-based materials,there are still some unsolved problems,such as the morphology and size of materials are difficult to control,the need for a variety of templates in the preparation process,the cumbersome operation process and has adverse effects on the environmental,high cost and so on.The purpose of this thesis is to develop a simple and efficient synthesis strategy of inorganic hierarchically porous materials to achieve precise control of the morphology and size of the material.Based on the research of the synthesis method,the application of as-synthesized samples in the field of catalysis and energy storage was studied.Cage-like hierarchically mesoporous hollow silica microspheres templated by mesomorphous polyelectrolyte-surfactant complexes for noble metal nanoparticles immobilizationHollow silica microspheres with hierarchically mesoporous shell structure have shown great application value in the fields of immobilization,catalysis and drug delivery systems,and have attractedwidespread attention.However,the synthesis of hierarchically mesoporous hollow silica materials still faces enormous challenges.In this chapter,we introduce the dynamic template mechanism into the synthesis of hollow hierarchically mesoporous silica materials.In the synthesis,anionic polyelectrolyte polyacrylic acid(PAA)and a cationic surfactant cetylpyridinium chloride(CPC)were co-assembled by charge to form organic mesomorphous complexes and used as templates,TEOS and 3-aminotriethoxysilane were used as silicon source and aminosilicon source to synthesize hollow hierarchically mesoporous silica microsphere.The effect of 3-aminotriethoxysilane on the morphology and pore structure of the prepared silica microspheres was investigated by simply adjusting the amount of aminosilicon source added,and the mechanism of synthesis the hollow hierarchically mesoporous silica microspheres were further explored.A series of characterizations of the morphology and structure of the synthesized samples were carried out by means of scanning electron microscopy(SEM),transmission electron microscopy(TEM),nitrogen adsorption and X-ray diffraction(XRD).The results show that the silica materials with hollow structure are synthesized by the "dynamic template method",and the secondary nanopore distribution with mesopores and large size are obtained,interestingly the shell structure is uniformly modified with amino functional groups.This unique hollow structure and rich in organic functional groups will make it a great application value in practical applications.Subsequently,silica-supported noble metal nanoparticle catalysts were prepared by using the synthesized hollow hierarchically mesoporous silica microspheres as catalyst carrier,and the catalytic performance of catalytic reduction of p-nitrophenol was evaluated.The results show that the catalyst has high catalytic efficiency and cycle life.Three-dimensional sulculs-like hierarchically nanoporous carbon materials: controllable synthesis,activation and for high performance supercapacitor electrodesCarbon-based materials with hierarchically mesoporous structure,which exhibits the advantages of pore size and has a synergistic effect during electrochemical charge-discharge.In hierarchically mesoporousstructure carbon materials,micropores generally increase the specific surface area of the material to increase the electric double layer capacitance;and mesopores act as a fast transport channel for ions,accelerating the kinetics of ion migration;Used as an ion buffer-storage container to improve the power performance of EDLC at high current densities.At present,the great challenge faced in preparing nanocarbon materials having a hierarchically pore structure interconnecting macropores and mesopores is how to make the arrangement of the channels in the material long-range.A hierarchically mesoporous nano-carbon material(SHNC)with a three-dimensional sulculs-like structure was synthesized in one step by using dynamic template method,and it was applied as an electrode material in the field of supercapacitors.We use mesomorphous complexes formed by anionic polyelectrolyte polyacrylic acid(PAA)and cationic surfactant(CPC)under alkaline conditions as templates,and silica formed by tetraethyl orthosilicate(TEOS)as a support skeleton,sucrose as a carbon source.The synthesized SHNCMs have interconnected micropores,ordered mesopores,and large-sized secondary nanopores.In addition,the pore structure of SHNCMs can be controlled by simply adjusting the amount of sucrose and PAA added in the system.Subsequently,activated grooved hierarchically mesoporous pore carbon materials(ASHNCMs)were also prepared by using potassium hydroxide as an activator.The application of SHNCMs as electrode materials to supercapacitors and their electrochemical performance showed that the materials have excellent capacitance properties,including high specific capacitance,high rate performance,low equivalent resistance and excellent cycle stability.