Identification of CuO Species in High Surface Area CuO−CeO₂Catalysts and Their Catalytic Activities for CO Oxidation

Abstract

Nanosized CuO−CeO2 catalysts with high surface area (>90 m2 g-1) were prepared by a modified citrate sol−gel method with incorporation of N2 thermal treatment. CO temperature-programmed reduction results indicated that there are three CuO species in the catalyst, namely, the finely dispersed CuO, the bulk CuO, and the Cu2+ in the CeO2 lattice. Using CO oxidation as a model reaction, catalytic activity of each species was evaluated. It was found that the finely dispersed CuO species had the highest activity (183.3 mmolCO gCu-1 h-1) and the bulk CuO had medium activity (100.4 mmolCO gCu-1 h-1), while the Cu2+ in the CeO2 lattice had the lowest activity (21.3 mmolCO gCu-1 h-1). Furthermore, the Cu2+ species in the CeO2 lattice could migrate to the catalyst surface to form finely dispersed CuO under high-temperature calcination or under reaction conditions, which could consequently enhance the catalytic activity.