Ultrafine cobalt oxide nanoparticles embedded in porous SiO2 matrix as efficient and stable catalysts for methane combustion

Ultrafine cobalt oxide nanoparticles embedded in porous SiO2 matrix were facilely prepared by a spontaneous deposition method, which were applied to catalytic methane combustion. Among the serial of CoOx@SiO2-T catalysts, the CoOx@SiO2-400 catalyst with the smallest particle size ((similar to)1.3 nm) has the highest activity, showing an obvious size-dependent activity. Based on the XPS, O-2-TPD and H-2-TPR analyses, it indicated that the CoOx@ SiO2-400 catalyst possessed a higher ratio of surface absorbed oxygen and lattice oxygen (O-ads/O-latt) and more active sites, which enabled the enhancement of its catalytic activity. Compared with simply supported CoOx@SiO2-400 catalyst, the embedded CoOx@SiO2-400 catalyst show superior catalytic performance under dry/ moisture conditions owing to silica encapsulation. As for possible CH4 combustion mechanism, the intermediate of Co-formate is determined by in-situ DRIFTS.