Diffuse LEED study of di-sigma ethylene on Pt(111): Adsorption on the three-fold hollow site

By means of diffuse LEED, we have determined that di-{sigma} bonded ethylene adsorbs at a three-fold hollow site on Pt(111). This is contrary to the long-held assumption of bridge site adsorption, implying instead an asymmetry between the two carbon atoms. This allows a much simpler picture of the dehydrogenation mechanism of ethylene on platinum to be constructed, for example, wherein rearrangement occurs without requiring the molecule to move to a new site. This new site assignment also allows reinterpretation of previously studied coadsorption systems, such as ethylene with ethylidyne, potassium or oxygen, with site-blocking as at least a partial explanation of the observed effects.