OH radical generation in a photocatalytic reactor using TiO2 nanotube plates

• The conditions for the synthesis of TiO2 nanotubes array on Ti plate were optimized.
• Confirmation of crystalline structure of TiO2 nanotubes was conducted after annealing.
• OH radical generation was confirmed in the photocatalytic reactor with TiO2 nanotube plate.
• More OH radicals were formed with longer nanotubes grown on Ti plate.

In order to use TiO2 nanotubes grown on a Ti plate as a photocatalyst, self-organized oxide nanotube layers were grown by anodization in a glycerol based electrolyte. The ultimate conditions for the synthesis of the TiO2 nanotube array on the Ti plate were investigated by comparing the morphology, length, and inner diameter of the nanotubes. They were significantly affected by the applied anodic voltage, anodization time, and composition of the electrolyte such as the water and fluoride ion concentration. The crystallographic structures of TiO2 nanotubes before and after annealing were compared. The photocatalytic reactor used in this study consisted of two parallel and closely spaced TiO2 nanotube plates. The plates were squares while a UV lamp was inserted perpendicularly to them. OH radical generation in the photocatalytic reactor was monitored by using a probe compound, parachlorobenzoate (pCBA). The steady state OH radical concentration was compared depending on the length of nanotubes and crystallographic structure. The longer the nanotubes, the higher the steady state OH radical concentration.