Preparation Of TiO₂Nanotubes By Anodic Oxidation

Titanium dioxide (TiO₂) is an important inorganic functional material with good optical,photosensitive, gas sensing etc features. This material has important applications prospects inthe field of photocatalytic degradation of pollutants, all kinds of sensors, solar cells,photovoltaic and other high tech solution and becomes a hot researching area in domestic andabroad. Titanium dioxide nano materials include nano particles, nano wires, nano tubes andother forms. Due to titanium dioxide nano tubes having a greater specific surface area,surface energy and stronger adsorption capacity, it has abstract widespread concern innational researchers. The common methods of synthesis of nano tubes are: template method,microwave method, and anodic oxidation. However, in most cases the template method needto remove the template, so that production cost becomes higher; titanium dioxide nano tubesprepared diameter by microwave method has relatively small inner diameter, usually smallerthan20nm; although the titanium dioxide nano tubes prepared by the anodic oxidationmethod has complicated process and post processing after preparation of nano tubes,however, titanium dioxide nano tubes prepared by anodic oxidation has larger diameter anduniform nano tube arrays. And with this method one end of the titanium nano tubes is closedand another end is open. All the nano tubes were neatly perpendicular to the surface oftitanium with oxidation. Many researchers hope that through the addition of nano particles ofspecific catalyst, this can help the dispersion of this catalyst homogeneously.In this article of titanium dioxide nano tube materials were prepared by anodic oxidationwith different systems (NH₄F system and HF heteropoly acid system) as the electrolyte.Titanium dioxide nano tube array with big inner diameter was successfully prepared on puretitanium surface. By using of X ray Diffraction (XRD), Scanning Electron Microscopy(SEM), Transmission Electron Microscopy (TEM), UV visible Spectrophotometer (UV VIS)and Gas Chromatography (GC), the prepared titanium dioxide nano tubes is characterized for crystalline materials, surface morphology and photocatalytic activity. Solution of methylorange is used as target photo degradation of material to study the photocatalytic activity oftitanium dioxide nano tube array in organic compounds. Also titanium dioxide nano materialsused as photocatalytic catalysts in the decomposition of organic pollutant is explored. Byusing ultra pure water and the water added with sacrificial agent methyl alcohol, applicationof titanium dioxide nano tubes in water splitting of hydrogen generating is studied.The main results are as follows:(1) Titanium dioxide nano materials prepared by different systems of electrolyte aredifferent: in the electrolysis process HF and POM hetero polyacid electrolyte system tend togenerate titanium dioxide nano wire or ribbon structure; NH₄F electrolyte system generatedaligned titanium dioxide nano tubes on the titanium surface.(2) The anodizing time, voltage and electrolyte concentration conditions have muchimpacts on the TiO₂nano structure such as wall thickness and inner diameter. The bestcondition for the preparation of TiO₂nano tubes is: NH₄F concentration of0.030.06mol/L,the oxidation voltage used is60V, oxidation time for the810h. Under this condition, TiO₂nano tubes arrays in the range of90¹20nm diameter, wall thick about35nm with smoothwall and aligned tubes.(3) Titanium dioxide nano materials photocatalytic experiments show that this materialhas good photocatalytic activity on the decomposition of methyl orange under ultravioletlight.(4) Titanium dioxide nano materials photocatalytic experiments in water splitting showthat pure titanium dioxide nano materials on the decomposition of water is weak under fullband of light; by adding methanol as sacrificial agent, water splitting is improved; by Ptdoping to titanium dioxide nano material the photocatalytic hydrogen production activityincreased significantly.