TUNNELING MODE OF SUPEROXIDE RADICAL-ANION DECAY ON PALLADIUM-PROMOTED YTTRIA

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