Effect of the structure of anodic TiO2 nanotube arrays on its photoelectrocatalytic activity

Abstract

Anodic TiO2 nanotube arrays (TNTs) exhibit excellent photoelectrocatalytic activities. However, the influence of TNTs structure on the photoelectrocatalytic activity has not yet been explored systematically. In this study, TNTs were prepared through anodization of Ti foils in electrolytic solution followed by annealing at 350 oC. The morphologies and microstructures of the as-prepared TNTs were characterized by scanning electron microscopy and X-ray diffraction. The photoelectrocatalytic activity of the as-prepared TNTs was tested through the degradation of methyl orange dye. The photoelectrocatalytic activity of TNTs increases with its length. It only takes 28 min for 2.90 um long TNTs to reach 98% degradation percentage, in comparison with that of 36min for 4.16 um long TNTs and 40 min for 7.72μm long TNTs. Better integrity and smoothness of TNTs presents better photoelectrocatalytic activity. E.g.: TNTs annealed at 350 oC for 1h presents better integrity and only take 28 min to obtain 98% degradation percentage, in comparison with that of 32 min for TNTs annealed at 350 oC for 3h. The crystal structure of TNTs with preferred orientation shows better photoelectrocatalytic activity than that with random orientation, which only takes 24 min to reach 98% degradation percentage, in comparison with that of 36 min for random orientated TNTs. Consequently, the photoelectrocatalytic activity of TNTs is highly related with the structure of TNTs.