1,2-Dichloroethene on Cu(1 1 0): Adsorption, dechlorination and trimerisation reactions

The adsorption and reactions of cis-1,2-dichloroethene on Cu(1 1 0) have been investigated using Reflection Absorption Infrared Spectroscopy, Temperature Programmed Desorption and Molecular Beam Adsorption Reaction Spectroscopy, and the behaviour compared with that of the previously studied [S. Haq, S.C. Laroze, C. Mitchell, N. Winterton, R. Raval, Surf. Sci. 531 (2003) 145] trans isomer. No isomerisation between the cis and trans isomers was seen. The data reveal that, although the related positions of the Cl atoms force different adsorption geometries for the two isomers, the behaviour of both compounds follows a very similar general reaction pathway which is critically temperature-dependent and can be described in terms of three main regimes: Regime I occurring at low temperatures in which intact molecular adsorption occurs; Regime II, extending over the temperature range of 155–280 K, in which desorption/dechlorination events are triggered; and, finally, Regime III, over 280–450 K, is governed, for both isomers, by the behaviour of the acetylene intermediate at the surface which trimerises to form benzene and desorbs above 350 K.

Graphical abstractAdsorption and reactions of cis-1,2-dichloroethene on Cu(1 1 0) can be described in terms of three main regimes: I (<150 K) intact molecular adsorption; II (155–280 K) desorption/dechlorination; and finally, III (>280–450 K) trimerisation of the acetylene intermediate at the surface to form benzene which desorbs above 350 K. Although the related positions of the Cl atoms force different adsorption geometries for cis- and trans-1,2-dichloroethene, the behaviour of the two compounds is similar. No isomerisation between the cis and trans isomers was seen.Figure optionsDownload full-size imageDownload as PowerPoint slide