An Auger spectroscopic study of the kinetic behavior of adsorbed oxygen on palladium

The adsorption of oxygen on polycrystalline palladium, the kinetics of the reaction of adsorbed oxygen with carbon monoxide and the amount of adsorbed oxygen present during the catalyzed reaction, $\text{CO +}\text{1}\text{2}\text{O}{}_2\text{→ CO}{}_2$, were studied by Auger electron spectroscopy. At temperatures below 783 K, the initial sticking probability is high (~0.8). Adsorbed oxygen and CO react with high probability and low activation energy to form carbon dioxide. The reaction is first order with respect to carbon monoxide pressure and zero order in oxygen coverage. Oxygen coverages measured during the CO-oxidation reaction decrease sharply around P_CO ? P_O2 and are very small when P_CO >P_O2. The reaction kinetics are discussed using a modified Eley-Rideal mechanism involving strongly adsorbed oxygen atoms and surface carbon monoxide in a short-lived state. The oxygen adsorption phenomena are correlated with the reaction kinetics.