A series of Er-, Yb-, Ho-, Tb-, Gd-, Pr-TiO2 nanotubes (RE-NTs) was prepared via an electrochemical method. The as-prepared photocatalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis absorption, scanning electron microscopy (SEM) and luminescent spectroscopy. The experiments demonstrated that toluene in the gas phase was successfully degraded under visible light (LEDs lambda(max) = 465 nm) using RE-NTs. In the presence of the most active sample (Ho-NTs), the photodegradation of toluene reached 30% after 60 min of vis irradiation. To investigate the localization of RE in the TiO2 structure, computer simulations were performed using the plane-wave-based Vienna ab-initio simulation package (VASP) implementing spin-polarized density-functional theory (DFT) and the generalized gradient approximation (GGA). It is proposed that during the electrochemical process, TiO2 systems with new Ho-f states below the conduction band of TiO2 is formed. The photocatalytic activity under Vis irradiation is attributable not to (OH)-O-center dot but to other forms of reactive oxygen species (O-2(center dot-), HO2 center dot, H2O2). (C) 2016 Elsevier B.V. All rights reserved.