Formation and hydrogenation of ethylidene on the Pt(111) surface

Hydrocarbon intermediates formed in the course of ethylene adsorption and decomposition on Pt(1 1 1) were investigated using reflection absorption infrared spectroscopy (RAIRS) and mass spectrometry. The ethylidene (CHCH3) species is identified on the basis of RAIRS peaks at 2960 and 1387 cm(-1) that are assigned to the CH3 asymmetric stretch and the CH3 symmetric bend, respectively. It is found that the highest ethylidene coverage can be produced by ethylene exposure to the surface at temperatures around 280 K. Ethylidene undergoes rapid hydrogenation upon exposure to 2 x 10(-7) Torr of H-2 at 250 K to produce gas-phase ethane, as detected by a mass spectrometer. The results indicate that ethylidene could be an intermediate in ethylene hydrogenation on transition metal surfaces near room temperature. (C) 2004 Elsevier B.V. All rights reserved.