Influence of calcination and pretreatment conditions on the activity of Co3O4 for CO oxidation

The influence of calcination and pretreatment conditions on the structure of Co3O4 and its activity for CO oxidation were studied. TG analysis indicated that the precursor of Co3O4 prepared by a precipitation method was present in the form of cobalt hydroxide carbonate, calcination of which within the temperature range of 150-400 degrees C in air resulted in the formation of cubic phase Co3O4. N-2 adsorption-desorption, powder X-ray diffraction, transmission electron microscopy, and activity test results showed that the prepared Co3O4 samples were comprised of nanoparticles, with the specific surface area and size distribution closely related to the calcination temperature. Over these samples, a size dependence of the catalytic activity for CO oxidation was clearly observed. As identified by positron annihilation lifetime spectrum, low temperature oxygen temperature-programmed desorption, and durability testing for CO oxidation, pretreatment of Co3O4 in N-2 within the temperature range 150-250 degrees C favors the formation of surface oxygen vacancy clusters, the occurrence of which would be beneficial for the adsorption and activation of O-2, and also for the catalytic oxidation of CO. Meanwhile, the reconstruction of oxygen vacancies on the surface of Co3O4, induced by the pretreatment process, was also discussed. (C) 2013, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.