Preparation Of Mesoporous Metal Oxide Semiconductor Fibers By Self-assembly Of Unimolecular Micelles In Electrospinning Beam Stream And Their Applications In The Energy Field

Recently,mesoporous metal oxides(MOs)with nanostructure have gained increasing attention in many application fields such as catalysis,energy conversion and storage,sensor technique,and sensitized solar cells.Particularly,one-dimensional(1D)nanofibers(NFs)attract great interest owing to its large aspect ratio,which can provide short and effective mass/electron transfer pathways.However,1D MOs with both mesoporous structure and fibrous morphology have rarely been obtained for some limitations of the material synthesis methods.Therefore,the development of effective strategy for mesoporous MO NFs is greatly demanded.This research demonstrates a facile and universal strategy for preparing a series of mesoporous MO NFs by self-organization of unimolecular micelles in beam stream.The prepared mesoporous MO NFs could be applied in many fields.In this paper,two kinds of mesoporous fibers are chosen as examples,they could show excellent performance when used for visible light photocatalytic degradation of tetracycline and lithium-sulfur battery cathodes as well.The specific research results are as follows:(1)The atom transfer radical polymerization(ATRP)method is used to synthesize?-cyclodextrin-polystyrene-block-poly(tert-butyl acrylate)-Bromine(?-CD-PS-b-Pt BA-Br).In a typical synthesis process,21-arm brominated cyclodextrin is used as initiator,styrene(St)and tert-butyl acrylate(t BA)are monomers,cuprous bromide(Cu Br)and N,N,N',N'',N''-Pentamethyldiethylenetriamine(PMDETA)are chosen as the catalytic system.The?-cyclodextrin-polystyrene-block-poly(tert-butyl acrylate)-block-poly(ethylene oxide)(?-CD-PS-b-Pt BA-b-PEO)is synthesized by combining poly(ethylene oxide)methyl ether(m PEO)with intermediate product.After hydrolysis,the final product?-cyclodextrin-polystyrene-block-poly(acrylic acid)-block-poly(ethylene oxide)(?-CD-PS-b-PAA-b-PEO)is obtained.The relative molecular weight and polymer dispersity index(PDI)derived from the gel permeation chromatography(GPC)value is?439000 and?1.33,respectively.(2)Herein,we develop a universal strategy by applying ?-CD-PS-b-PAA-b-PEO as template in the preparation of mesoporous metal oxide(e.g.,Ti O₂,Zr O₂,WO₃,Ce O₂)nanofibers(NFs),Mesoporous Ti O₂ nanofibers(m-TNF)are selected as an example,the fiber has a large specific surface area(145.59 m~2 g^-1)and a uniform pore size(?10.8 nm),and then Pt-loaded m-TNF(m-TNF/Pt)is obtained by light deposition.Compared with m-TNF/Pt,m-TNF and commercial P25Ti O₂,the photocatalytic degradation of tetracycline(TC)is tested under visible light irradiation.Both m-TNF/Pt and m-TNF showed better performance than P25.Among them,the performance of m-TNF/Pt is particularly outstanding,its photodegradation efficiency of TC within 100 minutes reaches 81.4%,and it also shows an excellent cycle stability.(3)The strategy mentioned above can also be extended to prepare composite NFs of bi-MOs(e.g.,Ti O₂/WO₃,Ti O₂/Zr O₂,Ti O₂/Ce O₂),which also possess a straight fibrous structure with uniform mesopores.Mesoporous Ti O₂/WO₃ composite fibers(m-TWNF)are chosen as the research interest.The specific surface area of m-TWNF is 118.3 m~2 g^-1 and the pore diameter is?10.8 nm.The m-TWNF@S/C is mixed with sulfur and conductive carbon and work as cathode material.The initial discharge capacity measured at 0.2 A g^-1 is 1145 m Ah g^-1,it could still maintain a specific capacity of 525 m Ah g^-1 after 200 cycles,which is significantly better than the positive electrode material TiO₂.