In this paper, the Co 3 O 4 catalysts prepared by the liquid phase precipitation method were investigated with respect to their activity and stability in CO oxidation reaction. The Co 3 O 4 catalysts were comparatively investigated by thermal gravimetry analysis (TG-DTG), X-ray powder diffraction (XRD), N 2 adsorption, CO titration and O 2 -temperature program desorption (O 2 -TPD). The results of XRD show that all the catalysts exist as a pure Co 3 O 4 phase with the spinel structure. The high catalytic activity observed at ambient temperature is followed by a gradual decrease. The CO titration experiments show that the Co 3 O 4 catalysts possess active oxygen species. The total amount of active oxygen species and the specific surface area decrease with increasing calcination temperature. The O 2 -TPD results indicate that O 2 -and O -are the possible active oxygen species.

Without use of any surfactant or oxidant, a series of Co 3 O 4 catalysts have been prepared from cobalt nitrate aqueous solution via a very simple liquid-precipitation method with ammonium acid carbonate followed by calcination at various temperatures. The catalytic performance of the Co 3 O 4 for CO oxidation has been studied with a continuous flowing laboratory microreactor system. The results show that the CO conversion of all the samples can reach 100% at ambient temperature. The catalyst calcined at 300°C is able to maintain its activity for CO complete oxidation more than 500 min at 25°C and about 240 min even at )78°C. High reaction temperature results in a high catalytic stability, while the catalytic stability decreases with further increasing the reaction temperature. Characterizations with X-ray powder diffraction and transmission electron microscopy suggest that all the samples exist as a pure Co 3 O 4 phase with the spinel structure, the samples are apt to aggregate and the specific surface area gradually decreases with increasing the calcination temperature, which directly leads to the decrease of catalytic stability. Furthermore, the amount of active oxygen species measured by CO titration experiments appears to be critical for catalytic performance.

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