Nano-structural variation of highly aligned anodic Titania nanotube arrays for gas phase photocatalytic application

Highly aligned titania (TiO2) nanotube (NT) arrays have been grown on titanium sheet by using a self organized anodic oxidation method at different potentials (34-74 V) in a NH4F and ethylene glycol based electrolyte. Two sets of TiO2 NT arrays have been fabricated with and without using cooling systems. Without cooling system, the solution temperature is increased from 25 °C (room temperature) to 63 °C with increase of anodization potential from 34 to 74 V. The temperature has been maintained to 25 °C by using water based cooling system. In both sets of samples, the pore diameter of TiO2 NT arrays increases with increase of anodization potential. The maximum pore diameter has been (outer: 224 nm, inner: 172 nm) achieved with TiO2 NT arrays (at 74 V) without using cooling system. The photocatalytic activity of the TiO2 NT arrays is evaluated by the decomposition of methanol by the use of Fourier transform infrared spectrophotometer. The TiO2 NT (at 44 V) sample has been fabricated without using cooling system, which shows the higher photocatalytic activity than the sample at other potentials. Using cooling system, the TiO2 NT (at 54 V) sample shows the higher photo-decomposing property than the sample at other potentials. The TiO2 NT (at 54 V) sample with cooling system shows the higher rate (photocatalytic activity) constant (k = 0.0216) than the TiO2 NT (at 44 V) sample without using cooling system (k = 0.0186). The photocatalytic activity has been correlated with the nanostructural variation of TiO2 NT arrays at different potentials without (self-grown solution temperature) and with water based cooling systems.