In situ construction of a highly active surface interface for a Co3O4|ZrO2 catalyst enhancing the CO-PrOx activity

Abstract

Employing a reduction–oxidation pretreatment led to the modification of the Co3O4|ZrO2 catalyst surface for the preferential oxidation of CO. It was shown, using XPS and temperature-programmed studies (O2-, CO-, CO2-TPD), that the amount of Co2+ species, O2 activation, CO2 desorption and CO adsorption sites improved. This was due to the restructuring of Co3O4 to more CoO species on the ZrO2 surface forming a highly active Co3O4–CoO|ZrO2 interface. This restructuring was supported by in situ XRD and XPS analysis which showed a decrease in the Co3O4 phase, without the emergence of metallic cobalt. The stabilization of more CoO species on the catalyst surface led to more basic sites being available on the surface, due to more oxygen anions/OH species, leading to improved CO2 desorption sites, which enhanced the CO oxidation activity. The balancing of these properties led to a 100% CO conversion (under dry and wet conditions) and excellent CO selectivity of 80% under wet conditions was achieved. The present finding highlights the importance of surface modification for improving CO preferential oxidation activity.