Infrared spectroscopy adsorbed ethylene

Studies to determine the nature of intermediate species have been made on a variety of transition metals, and especially on Pt, with emphasis on the Pt(lll) surface. Techniques such as TPD (temperature-programmed desorption), SIMS, NEXAFS (see Table VIII-1) and RAIRS (reflection absorption infrared spectroscopy) have been used, as well as all kinds of isotopic labeling (see Refs. 286 and 289). On Pt(III) the surface is covered with C2H3, ethylidyne, tightly bound to a three-fold hollow site, see Fig. XVIII-25, and Ref. 290. A current mechanism is that of the figure, in which ethylidyne acts as a kind of surface catalyst, allowing surface H atoms to add to a second, perhaps physically adsorbed layer of ethylene this is, in effect, a kind of Eley-Rideal mechanism. 

E. L. Force, A. T. Bell, The relationship of adsorbed species observed by infrared spectroscopy to the mechanism of ethylene oxidation over silver, /. Catal. 40 (1975) 356. 

Carter and coworkers in 1965 (32) examined alumina using infrared spectroscopy as the surface catalyzed ethylene hydrogenation reaction. By knowing the number of molecules in the system, the rate, and the total number adsorbed on active and inactive sites, they were able to conclude that one possible explanation of their results was that the site density was very low. 

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