Preparation And Electrocatalysis Of Supported Nano Oxides Based On Ti

Nanostructured materials have attracted a lot of attention due to the novel physicochemical property and wide application prospect. It is one of the electrochemistry development trends to apply nanostructured materials in catalysts. Nanostructured materials have more contact surface for chemical reaction because of smaller size and higher specific surface area. Besides, they have more surface active sites and higher catalytic activity result from incompetence of surface atomic coordinate, different states of bond and electronic between surface and inside, and so on. In this paper, BaTiO₃ nanocubes based on Ti foil, Na₂Ti₃O₇ nanowires, TiO₂ nanorod arrays based on Ti foil were fabricated, and the synthetic mechanisms, structures, morphologies were analyzed. Then, the nanostructured materials were used as the support for noble metal deposite. The structures, morphologies, and the electrocatalytic activities for H2O₂, methanol, ethanol of the supported nanostructured materials were studied. And their applications in electrochemical sensors, fuel cells, et al. were explored. The details are described as follows:1)The BaTiO₃ nanocubes were prepared directly on Ti foils through the composite-hydroxide-mediated method. The size of BaTiO₃ nanocubes and the thickness of the BaTiO₃ layer depend on the growth time. The nanostructured Pt was synthesized on BaTiO₃/Ti by electrochemical deposition. The morphology of BaTiO₃ nanocube on Ti foil, Pt catalysts deposited on BaTiO₃/Ti were characterized by FESEM, EDS. The results indicated that numerous Pt nanoflowers were deposited on the top of 48 h BaTiO₃ nanocubes. The 48 h Pt/BaTiO₃/Ti electrode had better performances in AC impedance spectra and determination of H2O₂, which provided a response current of 116?A cm^-2and response time of 4 s when each of 0.1 mM H2O₂ was added into 0.1 M PBS at pH 7.4. The linear detection of H2O₂ ranges from 5.0×10^-7M to 1.1×10^-3M (R2 = 0.999). Electrooxidations of methanol and ethanol were investigated on 48 h Pt/BaTiO₃/Ti and Pt/Ti electrodes in both acidic and alkaline media using cyclic voltammetry and linear sweep voltammetry. The 48 h Pt/BaTiO₃/Ti electrode showed higher electrocatalytic activity for oxidation of methanol and ethanol in both media. (in chapter 2)2) The Na₂Ti₃O₇ nanowires adsorbed with a large number of Ag nanoparticles (Ag/Na₂Ti₃O₇ nanowires) were prepared at a temperature of less than 100?in a sealed vessel, using Na₂Ti₃O₇ nanowires as precursor. The morphology and structure of Ag/Na₂Ti₃O₇ nanowires were characterized by XRD, FESEM, EDS. And the activity of the Ag/Na₂Ti₃O₇ catalyst electrode for the detection of H2O₂ was investigated using cyclic voltammetry and chronoamperometry. Electrochemical measurements indicate that the Ag/Na₂Ti₃O₇ catalyst facilitates H2O₂ redox remarkably in phosphate buffer solution. The Ag/Na₂Ti₃O₇ catalyst electrode exhibits a large linear range (50?M to 2.5 mM), a low detection limit (1.0?M), a short response time (within 3 s), high stability and very good reproducibility (92% remains after 30 days) for the detection of H2O₂. (in chapter 3)3) Pt nanoparticles deposited on Na₂Ti₃O₇ nanowires were prepared and used for the electrooxidation of methanol and ethanol. The Na₂Ti₃O₇ nanowires were used as the 3D frame for loading Pt nanoparticles. XRD, FESEM and EDS were employed to characterize the sample. Electrocatalytic activity and stability for the electrooxidation of methanol and ethanol were studied by cyclic voltammetry and chronoamperometry. The electrochemical studies reveal that the catalytic activity of Pt/Na₂Ti₃O₇ electrocatalyst is almost threefold higher than that of Pt/C electrocatalyst at the same loading of Pt. (in chapter 4)4) Vertically aligned TiO₂ nanorod arrays were prepared directly on the Ti foil through a one-step environmentally friendly and template-free solution method. XRD, FESEM and EDS were employed to characterize the synthesized samples. The control of morphology and size of the TiO₂ nanorods could be achieved by varying the solution concentration, hydrothermal temperature and synthesis time. The influence of nanorod size on the conductivity has been investigated by electrochemical impedance spectroscopy, and the results indicate that the electrical conductivity of thin nanorod arrays is better than that of thick nanorod arrays. Meanwhile, the electrode based on the thin TiO₂ nanorod arrays has shown highly sensitive and steady photocurrent response under simulated sunlight and UV illumination due to the higher specific surface area and directionality. (in chapter 5)5) Pt nanoparticles on TiO₂ nanorod arrays have been prepared and used for the electrooxidation of ethanol in acidic and alkaline media. FESEM and HRTEM observations reveal that the Pt nanoparticles about 3 nm in diameter are uniformly dispersed on the TiO₂ nanorod arrays. Because of the three-dimensional structure of the TiO₂ support for well-dispersed Pt nanoparticles, the Pt/TiO₂/Ti electrocatalyst has a larger active surface area as compared to the Pt/C and Pt/Ti electrocatalysts. Meanwhile the Pt/TiO₂/Ti electrocatalyst displays much better catalytic activity and higher stability for the ethanol electrooxidation in both acidic and alkaline media than the Pt/C and Pt/Ti electrocatalysts as a result of synergistic effect of Pt nanoparticles and the TiO₂ support. (in chapter 6)...