| Rational design of nanostructures endows materials with unique physical and chemical properties,thereby enhancing their performance and broadening their application fields.Hollow multishell structures(HoMSs),as the 3D hierarchical architecture constructed by 0D or 2D building blocks,possess interior cavities and multiple functional shells spatially ordered from outside to inside,have been proved to be able to realize the optimization in mass transfer and effective surface area exposure,which lead them to great achievements in energy storage,catalysis,electromagnetic wave absorption,and drug delivery applications.Benefitting from the introduction and development of sequential templating approach(STA),HoMSs with abundant chemical compositions and various geometry structures have been successfully designed and fabricated in recent years.Based on the deep understanding of STA,this work focuses on the precise synthesis and fine structural control of hollow multishelled structured materials.Firstly,the precise structural control of WO3 HoMSs was achieved by changing the solvent composition for the metal precursor enrichment process and modulating the spatial distribution and existence form of precursors in the carbon sphere template,while the changes of the crystal structure of the materials during the regulation process were studied at the atomic scale.Then,on the basis of precise structural control of WO3 HoMSs,WS2-x HoMSs were synthesized for the first time by sequential sulfidation and etching,and the shell number was doubled compared with WO3 HoMSs.Finally,the energy conversion and storage performance of the above materials were further investigated by various characterizations,revealing the intrinsic mechanism of HoMSs structure on the related performance enhancement.The main studies are as follows.(1)WO3 HoMSs with accurately controlled shell thickness and varied shell numbers have been successfully synthesized,and the effects of shell thickness on the overall photocatalytic proceeding were revealed.By skillfully exploiting the STA,the accurate control of the shell thickness was realized in the range from 35 to 90 nm by optimizing the amount and distribution of tungsten ions adsorbed within the carbonaceous templates via adjusting the solvent composition for precursor synthesis.Moreover,the effects of shell thickness on photocatalytic proceedings were thoroughly investigated.Although the thick-shelled WO3 HoMSs have better light-harvesting performance,thin triple-shelled ones exhibited higher photocatalytic activity owing to the increased charge-carrier separation/transfer efficiency and larger specific areas.Consequently,the thin-3 WO3 HoMSs showed a remarkable photocatalytic water oxidation activity up to 907 μmol g-1 h-1.(2)Starting with triple-shelled WO3 HoMSs precursor as above prepared,sextuple-shelled WS2-x HoMSs with precisely designed shell architecture and atomlevel structure were synthesized through a sequential sulfidation and etching approach.In the sulfidation reaction of WO3 HoMSs,the sulfidation reaction was conducted from the external and internal surfaces of shells.Meanwhile,owing to the nanoscale Kirkendall effect,heterogeneous sextuple-shelled WS2-x/WO3 HoMSs with sulfur vacancies were formed.After removing the residual WO3 in sextuple-shelled WS2-x/WO3 HoMSs through alkaline etching,sextuple-shelled WS2-x HoMSs with delicate shell structures were fabricated.The sulfur vacancy content was further increased because more WS2 nanosheet active edges are exposed after etching treatment.The morphology and structure analysis revealed that the WS2-x HoMSs were assembled by few-layered WS2-x nanosheets with expanded interlayer spacing.(3)Constructing WS2-x@N-C HoMSs by coating WS2-x HoMSs with nitrogendoped carbon,which improved the structural stability while preserving the morphological and structural features of the WS2-x HoMSs.The results of electrochemical kinetic analysis and theoretical calculation showed sextupleshelled WS2-x@N-C HoMSs offers multiple advantages for sodium storage:1)the special structures not only enhance the charge transport but also effectively buffer the stress and volume changes in sodiation/desodiation;2)sulfur vacancies and extended interlayer spacing can significantly reduce the Na+ diffusion energy barrier,thereby improving the Na+ diffusion kinetics;3)the surface carbon layer can effectively improve the conductivity of the material and enhance the structural stability.Benefiting from the above advantages,the sextuple-shelled WS2-x@N-C HoMSs achieved an outstanding sodium storage performance,maintaining a reversible capacity of 241.7 mAh g-1 at 5 A g-1 after 1000 cycles,corresponding to a high retention of 96.7%of the initial capacity. |
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