A simple way of preparation of Ni-modified and Ni,N-co-modified rutile TiO2 from an industrial grade amorphous titanium dioxide via impregnation followed by calcination at 1073 K in argon (Ni-TiO2) or ammonia (Ni,N-TiO2) atmosphere with different Ni:TiO2 ratios is presented. New materials were characterized by means of: XRD, XPS, elemental analysis, UV-Vis/DR spectroscopy, SEM, EPR and N-2 adsorption at 77 K. The photocatalytic activity of the materials was studied during decomposition of acetic acid under irradiation with UV or Vis light with wavelengths longer than 400 nm or 450 nm. The obtained results suggest the occurrence of a charge transfer between TiO2 and NiTiO3 phases resulting in a relatively high activity of XNi-TiO2 materials under the irradiation up to 400 nm. A band-gap narrowing of TiO2 after ammonia treatment was proved on the basis of UV-Vis/DR spectra for all the co-modified samples. The influence of Ti3+ ions on the band-gap narrowing and consequently photocatalytic activity of XNi,N-TiO2 and possible electron transfer from rutile conduction band to metallic Ni is here discussed. (C) 2013 Elsevier B.V. All rights reserved.