Modification and photocatalytic activity of open channel TiO2 nanotubes array synthesized by anodization process

Abstract

Titanium dioxide nanotubes (TNTs) with an open-top-tube morphology were synthesized by adjusting the anodization parameters. The main effective parameters were determined to be the multi-step anodization, alteration of anodization time, and agitation of the electrolyte. The simultaneous influence of agitation and prolonging the anodization time was studied on the obtained structure. The multi-step anodization process was shown to be a promising approach to obtain well-ordered TiO2 nanotubes. Accordingly, the entrance of the tubes came to be opened and the diameter of the surface pores increased from ~45 to 60 nm. By increasing the anodization time, chemical etching intensifies, especially on the upper part of the TNTs resulting in the formation of a nanograss structure. Applying agitation in prolonged anodization process showed to have destructive effects on the surface ordering and synthesis of nanograss free TNTs. However, it was found that subsequent agitation using ultrasonic pulses is an effective approach to obtain an open-top tube morphology. The DRS results indicated no difference in the band gap energy for different steps and anodization times. The photocatalytic activity of the open-top-tube TNTs was found to be promising in the degradation of methylene blue (MB) reaching 85% after 480 min irradiation.