Fabrication Of Hollow TiO₂ Nanomaterials And Application In Photocatalysis

TiO2 hollow nanostructures have attracted significant attention because they possess low density,high surface area,and unique void struture,which provide many new opportunities to the design of highly active nanostructured catalysts.Asymmetric triblock copolymeric nanoaggregates serve as versatile templates to obtain hollow nanostructures with better morphological and size control.However,traditional post-polymerization self-assembly techniques are less efficient in fabricating these kinds of template because they are invariably conducted in dilute(<1%)solution.In this article,hollow anatase nanospheres with good photocatalytic activity were prepared with micelles of asymmetric triblock copolymer,which were obtained on a large scale in one pot by using polymerization induced self-assembly and reorganization method.Besides,preparation of titania hollow nanorod was also explored with similar protocol by using styrene as monomer in PISR route.First,PGMMA-b-PDMAEMA-b-PBzMA copolymeric micelles with corona-shell-core architecture were prepared via RAFT dispersion polymerization of benzyl methacrylate(BzMA)in methanol with solid content of 15%w/w.Sequentially,a negatively charged inorganic titania precursor——titanium(IV)bis(ammonium lactate)dihydroxide(TALH)was used to coordinate exclusively into shell compartment of the micellar templates.TiO2/copolymer hybrid micelles of size about 50 nm were obtained by smooth hydrolysis and condensation upon stepwise heating.TEM images reveal synthesized hybrid spheres with good dispersibility exhibited apparent three-layered architecture.Furthermore,the copolymeric templates were removed by calcination to obtain anatase hollow spheres of size about 3 3nm with uniform void,which were confirmed by XRD and TEM.The fabricated anatase hollow spheres show much better photocatalytic activity in the degradation of methyl orange aqueous solution than a solid anatase analogue,which has smaller size of 25nm.Moreover,RAFT dispersion polymerization of styrene in ethanol was carried out to prepare PMEO2MA-b-PDMAEMA-b-PSt copolymeric nanomaterials with various morphologies including spherical micelle,nanorod and vesicle,as determined by TEM.Copolymeric nanorods were selected as templates to fabricate hybrid TiO2/copolymeric hybrid nanorod via similar route described above.TEM reveal successful deposition of TiO2 on copolymeric nanorod template.However,hollow nanorods were not obtained by following calcination,as observed by TEM,which were presumably induced by improper experimental conditions.