Oxidation of CO by 02 over ZnO Studied by FTIR Spectroscopy

Abstract

The adsorption of CO at room temperature on finely divided ZnO surfaces, studied by FTIR, shows reversible bands (2250-2050 cm-I) and irreversible absorption bands (1800-600 cm-I ). The irreversible absorption bands (1800-600 cm-I) are assigned to various species such as bi- and monodentate carbonates. The band position of the reversibly adsorbed species depends on the extent of the surface carbonates, formed by the oxidation of CO. The order of introduction of CO and 02 and whether the ZnO surface is oxidised or reduced, gave significantly different results in terms of species formed from irreversible adsorption. The strongest carbonate formation occurred on heating to 185 oc after 02 was added to the pre-adsorbed CO on an oxidised ZnO surface at room temperature followed by heating to 185°c in the presence of the two-gas mixture.