Photoelectrocatalytic Decomposition of Acid Red 4 in Aqueous Solution Using Prepared TiO2 Nanotube Arrays of Various Lengths

TiO2 nanotubes with controlled tube lengths were prepared by the anodization method and were utilized to investigate the photocatalytic and photoelectrocatalytic activities on Acid Red 4 decomposition in aqueous solution. Effects of annealing temperature and ramping rate on the surface dimension and crystal phase composition of prepared TiO2 nanotubes were studied. For Acid Red 4 decomposition by photoelectrocatalytic process, experiments using TiO2 nanotube exhibited up to 90% enhancement than those using granular TiO2-coated film due to the better charge transport ability of nanotube structure. Decomposition of Acid Red 4 by photocatalytic and photoelectrocatalytic processes for experiments using TiO2 nanotube was enhanced with increasing nanotube length in the length range of 500-1,000 nm. For experiments using TiO2 nanotube longer than 1,000 nm, photocatalytic and photoelectrocatalytic decomposition of Acid Red 4 were retarded.