Cu₂O-CuO hollow nanospheres as a heterogeneous catalyst for synergetic oxidation of CO

Copper oxides have attracted great attention in oxidation of CO due to its high activity at low temperature. In this work, uniform Cu₂O nanospheres were synthesized through a high-temperature polyol process, and they were further transformed into a series of Cu₂O-CuO nanosphere catalysts with a tunable Cu²⁺/Cu⁺ ratio by controlled calcination in air. On the basis of the study of surface composition and the corresponding catalytic activities, a synergetic catalytic mechanism was proposed where CO adsorbed on CuO is oxidized into CO₂ by lattice oxygen of CuO, and O₂ molecules adsorbed on Cu₂O split into oxygen adatoms and transfer to fill the oxygen vacancies on CuO. The synergetic mechanism explains well the high activity and good stability of the Cu₂O-CuO catalyst as well as the self-activation effect of uncalcined catalysts.