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Abstract

In this communication, a comprehensive review on halocarbon adsorption on solid surfaces is presented. The physical and chemical properties of surfaces, for which adsorbed halocarbons readily dissociate, are dominated by the respective halogens, hence, the published data on halogen adsorption on surfaces are also presented in a tabulated form. A complete reference list on halogen overlayers is provided. The adsorption of halocarbons is discussed with reference to their surface chemistry while technological as well as some environmental aspects are also mentioned. The available results are discussed according to the substrate surfaces used. In general, one can distinguish between substrates where some halocarbons adsorb molecularly or with partial fragmentation and those surfaces where the halocarbons dissociate completely and the atomic fragments remain adsorbed or absorb in the selvedge. The former class of substrates includes those which catalyse elimination reactions in the adsorbed phase (e.g. platinum). The latter case has been observed for iron surfaces, where after CFCI3 adsorption, a pronounced effect on the geometry and stability of the surface layer composed of chlorine atoms by the absorbed fragments (i.e. carbon and fluorine) has been noted. This vertical interaction of the coabsorbed (absorbed) atomic species in the selvedge is more pronounced than the effect of the lateral interaction in the adsorbed layer and might be of general importance in more complicated adsorption systems. We cannot offer an explanation for the physical basis of these vertical interaction effects, but these effects clearly demonstrate that, in certain systems, a separation between surface and solid state chemistry is arbitrary.