Application of transient response method to the study of heterogeneous catalysis: I. Nature of catalytically active oxygen on manganese dioxide for the oxidation of carbon monoxide at low temperatures

Abstract

The nature and the behavior of the surface oxygen species on manganese dioxide were studied in detail by means of the transient response method. The surface oxygen on manganese dioxide during the oxidation of carbon monoxide at −15 °C was classified into two parts, O s h and O s l , and O s h was found to be responsible for the catalytic activity of this oxide. The amount of O s h determined by the transient response method was in good agreement with that obtained by the analysis with the KI method which was used in our previous work. It was concluded that the O s h is in the forms of O 2 − or O − and is rapidly regenerated with the gaseous oxygen during the catalytic oxidation of carbon monoxide. This regeneration seems to take place instantaneously upon the release of electrons as the sequence of the reactions between the ionized oxygen species and the gaseous carbon monoxide followed by the desorption of carbon dioxide formed. The O s l , probably in the form of oxygen molecules, can transform into O s h , but the rate is very slow.