Facile and environmentally benign one-step titanium anodization method for TiO2 nanotubes (NTs) formation in a presence of ionic liquids (ILs) was proposed. Influence of the IL structure and its content in ethylene glycol electrolyte on morphology, surface properties and photoactivity of the TiO2 NTs was investigated. Possible interactions between IL and TiO2 NTs as well as the mechanism of NTs formation during anodic oxidation process were proposed. The outer diameter, wall thickness, and length of the IL-NTs were found to be proportionally related with increasing length of the hydrocarbon chain in the imidazolium cation of the IL (from 2 to 8), IL content, anodization potential and water content up to 10 vol.%. Moreover, for the first time, the effect of the IL's structure on the UV-vis and Vis light-induced photoactivity of the IL-Ti02 NTs was presented, and the active species ((OH)-O-center dot and O-2(center dot-) radicals) involved in the photocatalytic reaction of phenol degradation were determined. The sample that exhibited the highest photoactivity under Vis irradiation (0.63 mu mol dm(-3) min(-1)) and greatest amounts of generated (OH)-O-center dot was TiO2 NTs prepared at anodization potential 90V in the electrolyte containing 0.1 mol of 1-octyl-3-methylimidazolium tetrafluoroborate [OMIM][BF4] (represented by F-content) and 10 vol.% of water. Phenol degradation rate remained at level about 1.50 and 0.42 timol dm(3) min(-1) after 60 min of UV-vis and Vis irradiation after four cycles in the presence of [OMIM][BF4] and thus obtained IL-NTs exhibited photostability. The reaction proceeds under mild reaction conditions, is step economical and provides one-dimensional nanostructures that meet the specifications for use in diverse photocatalytic applications. (C) 2017 Elsevier B.V. All rights reserved.