The poisoning of D₂ dissociative chemisorption on Pt(111) by coadsorbed O₂

We have measured the dissociative chemisorption probability of D2 on Pt(111) as a function of molecular oxygen coverage and have found that the probability decreases linearly with O2 coverage. The results suggest that O2 poisons the chemisorption sterically by blocking approximately two adsorption sites per coadsorbed oxygen molecule. We conclude that the influence on the sticking probability of increasing the work function by coadsorbing oxygen is small, in contrast to the dramatic decrease in the sticking by coadsorbed potassium, which has previously been attributed to a decrease in the work function. © 1991.