Vibrational Spectroscopic Studies of the Structure of Species Derived From the Chemisorption of Hydrocarbons on Metal Single-Crystal Surfaces

This review is primarily concerned with the identification of the structures of chemisorbed complexes formed between hydrocarbons and metal sur­ faces through the use of various forms of vibrational spectroscopy (1) . Thc identification of the chemisorbed species and the study of their reactivities by spectroscopic methods provides an essential basis for the understanding of many classes of metal-catalyzed reactions of hydrocarbons such as hydrogenation/dehydrogenation, hydrogenolysis, isomerization, and metathesis. The particular emphasis of this article is on the study of species formed on metal single crystals that are cut so that specific surfaces of known atomic arrangements, e.g. the [1 1 1], [100], and [1 10] surfaces of face­ centered cubic (fcc) metals, are exposed to the hydrocarbon adsorbate. Such experiments have become feasible during the past 15 years or so. The principal vibrational spectroscopic techniques used for this purpose are high resolution electron energy loss spectroscopy (EELS) (2) and reflec­ tion/absorption infrared spectroscopy (RAIRS) (3). In recent years i t has been shown that results obtained with these simplified single-crystal systems are of great value III interpreting