Analysis of the thermochemistry of C 2 hydrocarbons on transition metal surfaces using a refined BOC-MP approach

Abstract

A refined version of the BOC-MP (bond-order-conservation Morse-potential) approach has been used to calculate the heats of adsorption and the activation barriers for dissociation and recombination of C 2H x species on transition metal surfaces, such as Fe/W(110), Ni(111), and Pt(111). The calculations reveal distinct periodic patterns of C 2H x transformations. In particular, it is found that most of the decomposition routes of ethylene and acetylene are strongly exothermic on Fe and W, but are mildly endothermic on Pt. Accordingly, the calculations predict that C-H and C-C bond cleavage from the gas phase occurs practically without activation on Fe and W, but with finite activation barriers on Ni and especially Pt. The conceivable pathways of C 2H x decompositions are discussed in detail. The projections of the refined BOC-MP approach are in much better agreement with experiment, as compared with our previous calculations.