Influence of dimensions, inter-distance and crystallinity of titania nanotubes (TNTs) on their photocatalytic activity

The aim of this study is to explore the influence of structural parameters of titania nanotubes (TNTs) including pore diameters, length, nanotube inter-distance and crystallinity on their photocatalytic properties. TNTs were prepared under various experimental conditions of applied potential, anodization time and the electrolyte water content. The morphology and crystalline structures of the prepared TNTs were characterized using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The results showed that the nanotube length, diameters and nanotube inter-distance were significantly affected by different anodization conditions. The photocatalytic activities of the prepared TNTs were evaluated via the degradation of rhodamine B in aqueous solution under mercury-xenon (Hg(Xe)) lamp irradiation monitored by UV-visible spectroscopy. The influence of TNT structural properties including tube length, inter-tube distance and crystallinity on their photocatalytic activity was evaluated. It was found that TNTs with shorter and larger nanotube inter-distances have better degradation rates of rhodamine B than long tubes. Moreover, the TNTs annealed at 650 °C to produce an anatase-rutile mixture (86.5 and 13.5% respectively) exhibited higher photocatalytic activity than other TNTs annealed at 250 °C, 450 °C, and 850 °C.