Preparation and catalytic performance of Co3O4 catalysts for low-temperature CO oxidation

Without use of any surfactant or oxidant, a series of Co3O4 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 Co3O4 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 degrees C is able to maintain its activity for CO complete oxidation more than 500 min at 25 degrees C and about 240 min even at -78 degrees 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 Co3O4 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.