Nickel-doped-TiO2 catalysts were prepared by the solgel method and surface modified with gold nanoparticles (AuNPs) by the urea-deposition-precipitation technique. The as-synthesized catalysts were characterized by X-ray diffraction, Raman and XPS spectroscopies, N-2 physisorption, STEM-HAADF microscopy and TPR hydrogen consumption. The Au/TiO2-Ni catalysts were evaluated catalytically performing CO oxidation reactions. The catalyst with nickel content of 1 wt. % (Au/TiO2-Ni 1) showed the highest CO conversion with respect to the high-nickel-content or bare/commercial TiO2 at 0 degrees C. In situ DRIFTS showed a strong participation of both nickel due to the presence of surface-nickel-metallic nanoparticles formed during the CO adsorption process at reaction temperatures above 200 degrees C, and surface-bridged-nickel-CO species. A minor deactivation rate was observed for the Au/TiO2-Ni 1 catalyst in comparison with the Au/TiO2 one. The oxygen vacancies that were created on the solgel-doped TiO2 improved the catalytic behavior during the performance of CO oxidation reactions, and inhibited the AuNP sintering. (C) 2016 Elsevier B.V. All rights reserved.