Identification of reaction intermediates and products in the dehalogenation of trichloroethene on Cu(110)

The decomposition of trichloroethene, C2HCl3, on Cu(110) has been investigated as a function of temperature by RAIRS, HREELS and TPD. This has provided a detailed identification of intermediate surface species involved in the dechlorination reaction. Multilayers form readily at 85 K, desorbing at 140 K. A weakly perturbed molecular species exists at 150 K that is converted, with increasing temperature, to a CCH intermediate at the surface. This ethynyl intermediate subsequently disproportionates to produce C2H2 and a carbon deposit at the surface. At T>300 K, C2H2 desorption competes with the trimerisation reaction that leads to benzene evolution at 370 K. Cl atoms are retained at the surface up to high temperatures.