Study On Photothermocatalytic Detoxification Of Benzene And Electrochemical Hydrogenation Of TNTAs

TiO2 nanotube arrays(TNTAs) fabricated by the method of direct anodic oxidation of titanium substrate are widely used as photo-catalytic degradation materials of organic contaminants, as sensing materials, supercapacitor and so on due to their excellent one-dimensional properties and high specific surface area. However, when TNTAs are used as photo-catalyst of volatile organic compound(VOC), such as benzene, they are prone to deactivation, which greatly inhibits the widely use of TNTAs. In this paper,highly-ordered TNTAs were prepared by direct anodic oxidation. The photo-catalytic activity of the TNTAs was evaluated by degradation of benzene over the temperature range 40-240°C under UV irradiation and the mechanism of the photothermocatalytic oxidation of benzene was carefully investigated. What’s more, TNTAs were electrochemically hydrogenated by being placed in 0.01 M NaOH solution to act as the cathode to electrolyze water and the photo-catalytic activity of H-TNTAs was carefully examined. The main results of this dissertation are listed as follows:(1) Highly ordered TiO2 nanotube arrays were prepared by anodic oxidation process and the formation mechanism of TiO2 nanotube arrays, as well as the effect of annealing temperature was carefully studied.(2) The photo-catalytic activity of the TNTAs was evaluated by degradation of benzene over the temperature range 40-240°C under UV irradiation and the experiment results indicated that the photo-catalytic activity of TNTAs was best at 200°C and the stability for the detoxification of benzene at 200°C was a lot better than that at 40°C.(3) The mechanism of the photothermocatalytic oxidation of benzene was carefully investigated from the aspects of carbon deposition and water absorption. The study shows that increasing temperature leads to desorption of water molecules, which makes a lot more unoccupied reactive sites available for photo-oxidation of benzene, resulting in the enhancement of the photo-catalytic activity of the TNTAs.(4) TNTAs were successfully hydrogenated using the method of electrochemical hydrogenation. The mechanism that the photo-catalytic activity of H-TNTAs was muchbetter than that of TNTAs was carefully investigated. XPS spectra measurement indicated that Ti3+ and oxygen vacancies were found in H-TNTAs.