| TiO2 and Li4Ti5O12 are two important titanium-based compounds. TiO2 has been widely used in a varity of photocatalytic applications because of itsgood chemical stability, non-toxicity low cost, and good photocatalytic activity. While Li4Ti5O12 has been used as a cathode candiate of Li-ion battery due to its good electrochemical properties indcluding high cycling stability, low volume change after current charging and so on.In this thesis, we developed a simple hydrothermal method to synthesize novel N-doped graphene-hybridized TiO2 nanomaterials (N-TiO2/N-rGO) using an ionic liquid of [Bmim][BF4] as an ethching agent. With this method, the N doping could be realized both in TiO2 and reduced graphene oxide (rGO) simultaneously. Meanwhile, the exposure of high energy facets of TiO2 can be reached due to the F- etching during the preparation. The as-prepared N-TiO2/N-rGO photocatalysts show superior photocatalytic activity based on theirhigh electron conductivity resulted from the graphene hybridization, N doping, and exposure of high energy crystal facets. Based on this result, we designed to synthesize a new kind of cathode materials of graphene-hybridized lithium titanate with N doped (N-LTO/N-rGO) via a hydrothermal method using N-TiO2/N-rGO as a precursor and LiOH solution as a lithium source. The obtained N-LTO/N-rGO nanomaterials possess the characteristics of small particle size, N doping, and graphene hybridization. Therefore, as anode materials of Li-ion battery, N-LTO/N-rGO nanomaterials havewide discharge platform, high capacity, and good cyclic stability, thusare considered to be a series of important materials for Li-ion battery.In the first charpter, the development of TiO2 and Li4Ti5O12 materials for uses in photocatalysis and Li-ion battery was reviewed. The structure, preparation, property, and application of TiO2 and Li4Ti5O12 were summariedBased on, the aim and research content of this thesis were proposed.In the second charpter, graphene-hybridized TiO2 (N-TiO2/N-rGO) photocatalysts doped with N element were synthesized via an ionic liquid assisted hydrothermal etching method using TBOT as a precursor and an ionic liquid of [Bmim][BF4] as a crystal facets directing agent. With this method, the N doping could be realized both in TiO2 and reduced graphene oxide (rGO) simultaneously. Meanwhile, the exposure of high energy facets of TiO2 can be reached due to the F- etching during the preparation.The obtained N-TiO2/N-rGO photocatalysts were characterized by means of X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), UV-vis diffuse reflectance spectroscopy (DRS), infrared spectroscopy (IR), fluorescence spectra (FL), X-ray photoelectron spectroscopy (XPS). It is found that the N-TiO2/N-rGO photocatalysts consist of TiO2 nanoparticals with small sizes uniformly dispersed on graphene sheetsshow a strong response to visible light with a high separation rate of electron-hole pairs. To eveluate the photocatalytic performance of N-TiO2/N-rGO photocatalysts, the photodegradation of organic dyes was used as a model reaction. The mechanism of the enhancement of photocatalytic activity was clarified by the free radicals capture experiments and transient photovoltage tests. The results prove that the enhancement of photocatalytic activity is resulted from the high electronic transmission rate and high electron-hole separation efficiency due to the graphene hybridization. Meanwhile, the exposure of high energy facets and N doping play important roles for improving the photocatalytic performance. The N-TiO2/N-rGO phtocatalystspossessing high photocatalytic activity ten times higher than commercial P25 show the great potential for use in photocatalysis.In the third charpter, the N-doped lithium titanate/N-doped graphene (N-LTO/N-rGO) cathode nanomaterials were synthesized via a simple hydrothermal method using N-TiO2/N-rGO as precursors. It is revealed thatthe graphene-hybridized Li4Ti5O12 (N-LTO/N-rGO) anode nanomaterials with two dimensional layered structures can be successfully obtained by modulating the molar ratio of Ti and Li precursora at 1:3 The N-LTO/N-rGO anode nanomaterials were characterized by means of XRD, SEM, TEM and XPS. XPS characterization confirms the doping of N element in Li4Ti5O12 and rGO simutanously. The electrochemical property was tested by CV curve and EIS spectra through assembling a half Li-ion battery. As it was reported that the performance of Li-ion battery was generally effected by the electrical conductivity and the diffusion rate of Li+, the obtained N-LTO/N-rGO in our work are expected to have good performance as anode nanomaterials forLi-ion battery because of their high diffusion rate of Li+ and excellent electron conductivity. The discharge capacity of optimized N-Li4Ti5O12/N-rGO anode nanomaterial is 165 mAh/g, which is close to the theoretical value of The discharge capacity of Li4Ti5O12. The excellent battery performance of N-Li4Ti5O12/N-rGO can be ascribed to several reasons. Firatly, N-doped graphene has better electrical conductivity. Secondly, N-Li4Ti5O12 has more sites for Li+ insertion and also possesses better electrical conductivity. Thirdly, two dimensional structural configuration of N-Li4Ti5O12/N-rGO with small particle size of N-Li4Ti5Oi2 makes the diffusion path of Li+much shorter. Thus, N-LTO/N-rGO anode materials show excellent battery performance and show great potential for use in Li-ion battery.In the fifth charpter, the summary was given and the prospect was proposed. |
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