Temperature programmed desorption study of the adsorption and absorption of hydrogen on and in Cu(111)

TPD studies of the interaction of atomic hydrogen with Cu(111) as a function of coverage indicate the formation of chemisorbed and absorbed species at 98 K. At low coverage a single desorption feature, β, is observed at 330 K. This desorption feature has been observed previously and assigned to desorption of chemisorbed surface species with a saturation coverage of 0.5 ML. With increasing exposure, two more desorption features, α 1 and α 2, are observed at 200 and 220 K, respectively. The α 1 state saturates quickly with a relative population density of approximately 1 2 that of the β peak. The α 2 state, however, did not saturate. At higher exposures, desorption from the α 2 state was greater than ten times the saturated β state. The α 2 state exhibited zeroth order desorption kinetics with an activation energy for desorption of 8.8 kcal/mol and was attributed to desorption of an absorbed species from the bulk.