Studies On Modification Of Titania Nanotubes Arrays And Its Application

Because of the high oxidative power, photostability, nontoxicity and low cost, TiO2 nanotube arrays prepared by anodization are considered to be the most attractive photocatalyst. Howerer, TiO2 is a high band gap (3.2 eV) semiconductor material and can be only used for photoelectrolysis under the ultraviolet (UV) light illumination. Besides, there is another problem about it that the photogenerated charge carriers would recombine during the photocatalytic process. Therefore, carbon nanorod and PbS nanopaiticle was modified on TiO2 nanotube arrays to extend the absorption into the visible region, promoting the charge carriers transfer. And Pt/CNT/TiO2 was investigated on its methanol electrocatalytic oxidation. The details are listed as below:(1) Fabrication, characterization and photocatalytic application of the C-N-doped TiO2 NT/carbon nanorod heteojunction. The C-N-doped TiO2 nanotube (NT)/carbon nanorod composite is fabricated by chemical vapor deposition (CVD). Carbon nanorods are grown from the TiO2 NTs, and partly graphitized, while TiO2 is in the mixture of anatase and rutile. The C-N doping shifts the absorption edge of TiO2 NTs to the visible light region; the formed carbon nanorods promote the charge carrier transfer from the TiO2 surface to the electrolyte. Under the simulated solar light irradiation, the C-N-doped TiO2 NTs show higher photocatalytic activity in the degradation of methyl orange (MO) than the undoped TiO2 NTs.(2) Fabrication, characterization and photocatalytic application of the PbS/TiO2. By using successive ionic layer adsorption and reaction (SILAR) processes and electrodeposition, PbS nanoparticles are attached to the TiO2 NTs with an aim to tune the photoelectrochemical cell to the visible region. Under visible light, PbS nanoparticles inject electrons into TiO2 and thus enable them to be used as photosensitive electrodes. The PbS/TiO2 NT exhibits high adsorption in the visible region and can reach photocurrent at 11.02 mA by SILAR and 5.72 mA by electrodeposition, which is attributed to the increased efficiency of charge separation. The size of PbS nanoparticles deposited by SILAR is smaller. Another method decorates the TiO2 NTs with PbS by an easy and quick electrochemical process. And the structure of the PbS nanoparticles is cubic. This process reduces many complicated and time-consuming steps for fabricating nanoparticles. The present study evaluates the charge transferring from the excited PbS nanoparticles into the TiO2 NTs, comparing the performance of photoelctrochemical cell and photocatalytic made with TiO2/PbS deposited by SILAR versus those made with TiO2/PbS deposited by electrodeposition(3) Fabrication and characterization of Pt modified TiO2 NTs/CNT as anode methanol electrocatalytic oxidation. First, the Ni nanoparticles were electrodeposied to the top surface of TiO2 NTs arrays. With the Polyethylene glycol (PEG) as the carbon source, and the Ni nanoparticles as the carboncatalytic, the TiO2 NTs were successfully modified by the CNTs. The electric properties of the TiO2 NTs modified with CNT were examined by the probe of Fe3+/Fe2+. The dispersed Pt nanoparticles were electrochemically deposited onto the TiO2 NTs/CNT. As an anode, the performance of the composite are investigated in methanol oxidation reaction (MOR). When Pt is at 50.52μg cm-2, the electrocatalysts reaches the highest activity. The enhanced catalytic efficiency is mainly attributed to the superiorly electrical conductivity of the deposited CNT, which facilitates the dispersion of the Pt and the charge transference during the MOR.