Activated dissociation ofO2on Pb(111) surfaces by Pb adatoms

Abstract

We investigate the dissociation of ${\text{O}}_{2}$ on Pb(111) surface using first-principles calculations. It is found that in a practical high-vacuum environment, the adsorption of molecular ${\text{O}}_{2}$ takes place on clean Pb surfaces only at low temperatures such as 100 K, but the ${\text{O}}_{2}$ easily desorbs at (elevated) room temperatures. It is further found that the Pb adatoms enhance the molecular adsorption and activate the adsorbed ${\text{O}}_{2}$ to dissociate during subsequent room-temperature annealing. Our theory explains the observation of a two-step oxidation process on the Pb surfaces by the unique role of Pb adatoms.