| Highly anisotropic two dimensional nanomaterials with atomic thickness have attracted great attention since graphene was found in 2004.For the limited size in one dimension,this kind of unique structure possesses quantum confinement effect and special surface effect,which lead to distinctive physicochemical properties from the common bulk materials,and owns tremendous potentials in catalysis,electrochemistry,adsorption,separation,electricity,photology,magnetics and et al.Titanium oxide nanosheets have the extremely broad applications in the fields of environment,energy storage,catalysis and et al.Nevertheless,the structure modulation/assembling of titanium oxide nanosheets and the related properties study are much less investigated.Besides,the facile mass synthesis of about 1 nm thick and high quality titanium oxide nanosheets with defined structure is still challenging.This thesis focuses on the study of the assembling,hybrid,and crystal transformation of TiO2 nanosheets derived from liquid-exfoliated monolayer titanate nanosheets.Furthermore,their performance for photocatalysis and electrochemical energy storage are also explored.The detailed research achievements are described briefly below:1.A facile method of loading nanoparticles was developed to avoid the restack of ultrathin nanosheets.Several nanosheets sols including titanate,a-ZrP,GO,and MgAl hydrotalcite were prepared through liquid exfoliation method.（1）The wet Pd/TiONS（TiONS:titanate nanosheets）was prepared by loading Pd nanoparticles on TiONS in liquid phase,and was used directly to catalyze the selectively hydrogenation of phenol to cyclohexanone.This catalyst possessed high specific surface area because the ultathin 0.9 nm thick TiONS support did not restack exceedingly in the processes of preparation and catalytic reaction.And the loaded Pd nanoparticles are about 1.9 nm in diameter.As a result,it showed much higher catalytic activity than the dried Pd/TiONS on the hydrogenation of phenol.（2）Ultrathin TiO2 nanosheets isolated by SiO2 nanoparticles were obtained by assembling liquid exfoliated nanosheets with-14 nm SiO2 nanoparticles.The SiO2 nanoparticles played a key role to sustain the nanosheets and preserve them from restacking and sintering during drying and calcination procedures.2.The preparation and performance of ultrathin TiO2 nanosheets.Based on the prior work,the minium amount of Sio2 nanoparticles was optimized to keep the ultrathin structure of TiONS.The calcination at 500℃ made the crystal structure of the TiONS transform from lepidocrocite type titanate to anatase TiO2 nanosheets,which exhibited several distinct features:0.6 nm thickness,high-energy（116）facets exposed primarily,-0.4 eV higher bandgap than bulk anatase.As a photocatalyst,the obtained anatase TiO2 nanosheets show excellent catalytic performance on the degradation of Rhodamine B under UV light irradiation.Furthermore,SiO2 in the hybrid powder could be etched by NaOH solution.And free-standing TiO2 nanosheets with specific surface area of 200 m2 g-1 was obtained through the subsequent removal of sodium ions by acid followed by calcination.3.The controlled synthesis and application in lithium ion battery of TiO2@carbon core-shell nanosheets.This distinct hybrid nanomaterial was synthesized by assembling TiONS with organic carbon sources and further in-situ carbonization.The obtained TiO2@carbon core-shell nanosheets consisted of closely conbined 1.1 nm thick TiO2 nanosheet core and 2.2 nm thick carbon layer shell.The ultrathin two dimensional structure shortened the motion path of lithium ions,which benifit the fast insertion/extraction of lithium ion.While the carbon shell improved the conductivity and stability of the TiO2@carbon core-shell nanosheets.Meanwhile,the introduced carbon layers also enhanced the whole capacity because of the high capacity of this kind of carbon layers.As an anode for litium ion battery,it exhibited high capacity,good rate performance and excellent cyclability(549 mAh g-1 after 300 cycles at 0.23 A g’1 and 385 mAh g’1 after 2000 cycles at 4.6 A g-1). |
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