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.