Effect of highly dispersed active sites of Cu/TiO₂ catalyst on CO oxidation

The oxidation of CO over Cu/TiO₂ catalysts containing different Cu loadings was investigated. The activities of the Cu/TiO₂ catalysts were observed to be nearly constant for Cu contents between 3.7 wt% and 10.3 wt%. The characterization of the Cu/TiO₂ catalysts by H₂ temperature-programmed reduction (TPR) suggested the presence of different CuO species with distinct catalytic activities, that is, isolated Cu atoms, highly dispersed CuO, and bulk CuO. The concentration of reducible Cu²⁺ species at low temperatures (437 K) was observed to be independent of Cu content and Cu atom aggregation due to a 773 K treatment. These reduced Cu species are potentially responsible for the activities of Cu/TiO₂ catalysts.