Ethylene adsorption on platinum: kinetics, bonding, and relevance to catalysis.

Ethylene adsorption on platinum(111) single-crystal surfaces involves two states, a di-sigma species irreversibly bonded on the clean surface, and a second pi reversible adsorption which develops at high coverages. The two states display significantly different kinetic behavior, but they can slowly interchange. This suggests an adsorption mechanism at high coverages via an initial interaction with the few metal atoms left exposed by an imperfect monolayer followed by a collective rearrangement of the neighboring molecules into a new compressed layer.