Effect of copper state on the properties of CuOx/TiO2 catalysts for low-temperature CO oxidation

A comprehensive study of supported CuO x /TiO 2 catalysts for low-temperature oxidation of carbon monoxide was conducted. The composition, structure, morphology, electronic state of the active phase for the samples were studied depending on calcination temperature and copper loading by XRD, XANES, EXAFS, HR TEM, EPR, XPS, and H 2 -TPR. It was found that after calcination of the samples at 300 °C, copper on anatase surface is in Cu 2+ state. At low concentrations (0.5–1 wt.%), copper exists predominantly as isolated ions and very small CuO clusters. As the copper concentration increases to 4 wt.%, small CuO nanoparticles measuring 1–3 nm are additionally formed. These sites actively engage in redox Cu 2+ – Cu + /Cu 0 interactions, ensuring high activity in CO oxidation, which was confirmed by XPS. Increasing calcination temperature of catalysts to 500 °C activates the sintering of copper clusters, leading to a decrease in activity. CuO x /TiO 2 materials demonstrated high activity, stability during 30-hour testing, and 7-hour tolerance to 100 ppm of toxic SO 2 impurity. CuO x /TiO 2 has been shown to be promising for low-temperature CO oxidation due to the availability of catalyst components and simple synthesis procedure.