Gold-TiO₂-Nickel catalysts for low temperature-driven CO oxidation reaction

Graphical abstract: - Highlights: • Nickel-doped TiO₂ catalysts (1 wt. %) drive the CO oxidation at low temperature. • DRIFTS reveals the participation of nickel during the CO oxidation. • Ni(CO)₂ bridged species are detected by DRIFTS. • Au/TiO₂-Ni 1 is the most active and stable catalyst with respect to undoped TiO₂. • Ti³⁺ species corroborate Ni doped TiO₂ and surface oxygen vacancies. - Abstract: Nickel-doped-TiO₂ catalysts were prepared by the sol–gel 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, N₂ 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 °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 °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 sol–gel-doped TiO₂ improved the catalytic behavior during the performance of CO oxidation reactions, and inhibited the AuNP sintering.