Effects of applied bias and dopants on the photocatalytic degradation of aqueous dye solution by TiO2/Ti electrode

The photocatalytic degradation of organics in aqueous solution is an active research field. Currently, the relatively low degradation efficiency is the key problem to be solved that caused by the simple recombination of the photo-generated electrons and holes. The electrode was prepared by anodic oxidation on titanium thin plate and produced multiporous nano-crystalline titanium dioxide film with anatase structure on titanium substrate. In order to inhibit the simple recombination of the electrons and holes, the electric potential bias was applied to the electrode to drive away the chargers. The change of the photocurrent and the discolouration of the dye solution containing either methylene blue or acid red G with different magnitude of the applied bias were measured. It shows that the photocurrent increased by three orders of magnitude from mu A to mA level by the applied bias. Correspondingly, the discolouration rate of the methylene blue in dye solution was increased greatly with the increasing applied bias up to 3.5V. The different kinds of transitional metal ions dopants of Mn2+, Cr3+, Fe3+, and Ni2+ to the electrodes was done by anodic oxidation method. The effects of different types of dopants on the photocatalytic activity were revealed by measuring the degradation of an organics aqueous solution containing a dye using a combination of ultraviolet light energy in the presence of these electrodes. The photocatalytic efficiency, which was remarkably enhanced by the incorporation of Mn2+, Cr3+, Mn2+, showed the largest enhancement. However, Fe3+ changed only slightly, and Ni2+ showed no enhancement. These effects were related to the difference of these transitional metal dopants electron work function values and also to the difference of their ionic radii in respect to that of Ti4+. The configuration of the reactor for water treatment with the rotating electrode and 365nm wavelength UV radiation was described.