Preparation And Properties Of Novel Yolk-Shell Nanosphere Composite Materials

The yolk-shell structure nanosphere is a spherical hollow cavity structure composite material having a unique nanoshell surrounding its inner functional nanoparticle,and can exert the synergistic advantages of the hollow nanosphere and the functional nanoparticle,which has a wide range of applications in adsorption and separation,biomedicine,catalysis,energy and other fields,and is an extensive research area of materials science.Although significant advances have been made in the research of yolk-shell nanospheres,the design,synthesis and application of novel functional yolk-shell nanospheres,especially noble metal@hollow polymers and their carbon nanospheres,are still big challenge.In this paper,two key scientific issues surrounding the creation and preparation of yolk-shell nanospheres were innovated.By means of supercross-linking chemical reactions,a variety of novel noble metal@hollow polymers and charcoal with microporous shell structures were designed and synthesized.Based on the successful preparation,the structure regulation rules of the new materials obtained were studied,and their application in lithium-sulfur batteries,small-molecule chemical reaction catalysis,antibacterial,and electrochemical hydrogen evolution reaction catalysis were discussed.The obtained research results are as follows:?1?Design,structure regulation and application of Au@hollow microporous polymer and its carbon nanospheresOn the basis of successful synthesis of Au@SiO₂ core-shell nanospheres,Au@SiO₂@poly?chloromethylstyrene?nanospheres with multi-core shell structure were prepared by surface modification and emulsion polymerization.Subsequently,by using the characteristics of the methylene group of polychloromethylstyrene as a self-crosslinking reaction,under the condition of adding additional crosslinking agent,a rich micropore network structure can be built inside the shell.And after removing the SiO₂ template component,a monodispersed Au@hollow microporous polymer nanosphere with a micropore shell structure was obtained.Due to the rigid structure of the polychloromethyl styrene shell,after the high-temperature carbonization treatment,the Au@hollow microporous polymer nanospheres can be converted into Au@hollow microporous carbon nanospheres with high conductivity.The results show that Au@hollow microporous polymer and carbon nanospheres have good spherical morphology,and their specific surface area can reach as high as 871 and970 m² g^-1,respectively.In addition,it was found that the process sequence of removing SiO₂ template components has a significant effect on the nanostructure of Au@hollow microporous carbon nanospheres.Removal of the SiO₂ template component followed by carbonization is more beneficial to obtain high specific surface area Au@hollow microporous carbon nanospheres than removing the SiO₂ template component after carbonization.By controlling the carbonization time,the specific surface area of the Au@hollow microporous carbon nanospheres can be controlled in the range of 642 to970 m² g^-1,but the increase in the carbonization time will damage the nanoballoon appearance of the resulting material.The test results show that the Au@hollow microporous carbon nanospheres have a significant role in the catalytic hydrogenation of p-nitrophenol to p-aminophenol.When used as an elemental sulfur carrier,the introduction of Au nanoparticles can not only improve the conductivity of the electrode material,but also catalyze the conversion of sulfur to lithium sulfide,resulting in a strong chemical adsorption of soluble polysulfides,thereby significantly improving the electrochemical performance of the material.Therefore,compared to hollow microporous carbon nanospheres/sulfur composites without nano-Au particles,the Au@hollow microporous carbon nanospheres/sulfur composites have more obvious advantages when used as cathode materials for lithium-sulfur batteries.At 0.1 C,it has a high discharge capacity of 1385 mAh g^-1,and can still maintain 712 mAh g^-11 after 25 cycles.?2?Design,structure regulation and application of Ag@hollow microporous carbon nanospheresWith the help of Au@hollow microporous carbon nanospheres,a rigid cross-linked polychloromethylstyrene shell was constructed on the surface of Ag@SiO₂ nanospheres by template-hypercrosslinking,and after carbonization and removal of the SiO₂ template group,the Ag@hollow microporous carbon nanospheres with good spherical morphology were prepared.On the basis of successful preparation,its application in antibacterial and handling formaldehyde gas was explored.The performance test results show that Ag@hollow microporous carbon nanospheres have excellent antibacterial properties and can successfully inhibit the growth of E.coli.Besides,the new material has excellent adsorption properties for formaldehyde gas.After adsorption for 48 h,its maximum adsorption capacity can reach 86.76 mg m^-3.?3?Design,structure regulation and application of Pt@hollow microporous carbon nanospheresOn the basis of synthesizing Pt@SiO₂ core-shell nanospheres,the multi-core shell-structured noble metal@SiO₂@polystyrene composite nanospheres was prepared by surface modification and emulsion polymerization.After ultra-cross-linking,carbonization and removal of SiO₂ template components and other steps,Pt@hollow microporous carbon nanospheres with electrocatalytically active nano-platinum cores were successfully prepared.It was found that with increasing the amount of styrene added,the particle size and shell thickness of Pt@hollow microporous carbon nanoballs continued to increase.Typical Pt@hollow microporous carbon nanospheres have particle sizes and shell thickness of 260 nm and 40 nm,respectively.The test results found that Pt@hollow microporous carbon nanospheres have good electrochemical catalytic hydrogen evolution reaction characteristics,and have better efficient than commercial Pt/C catalysts.