Coadsorption of oxygen and caesium on silver (110)

The coadsorption of oxygen and caesium on silver has been studied by means of UPS and TPD. Adsorption of oxygen on a caesiated surface occurs in two stages, with a sticking coefficient, s, of nearly one in the first stage. In the second stage, the sticking coefficient is lower, but still higher than on the clean surface. After adsorption, the oxygen is present in two states, which are identified in TPD. These are ascribed to oxygen atoms adsorbed directly adjacent to Cs atoms, and those more distant from the Cs. Shifts in the Cs 5p lines are consistent with this assignment. The relevance to industrial catalysis of partial oxidation reactions over silver (e.g. epoxidation of ethylene) is discussed.