Tunnelling mode of superoxide radical anion decay on palladium-promoted yttria

Abstract

The decay of the adsorbed superoxide radical anions in hydrogen in palladium-promoted yttria is accelerated when the content of palladium ions is increased. The decay kinetics are polyexponential and reflect the tunnelling mode of electron transfer (or electron tunnelling) to superoxide ions. Pd⁺ ions appearing during the reduction seem to be efficient electron donors for the adsorbed dioxygen species at low and ambient temperatures. Hydration of the doped oxide surface may increase the rate of superoxide reduction. This effect is ascribed to change in the frequency factor. The ionic states of transition metals often detected in supported catalysts may have significant impact on the adsorbed molecules even without contact with the adsorbed species.