SURFACE RESTRUCTURING AS A MECHANISM FOR BOND BREAKING AND CATALYTIC REACTIONS AT METAL SURFACES

Low energy electron diffraction surface crystallography studies indicate that the more open crystal surfaces with higher Miller index restructure more readily when clean. These investigations also uncovered the predominance of adsorbate induced restructuring of surface atoms. It is suggested that one mechanism of chemical bond breaking for adsorbate molecules is surface restructuring induced bond scission and that catalytic processes on metals can be induced by the restructuring of surface atoms around the adsorbate species. While direct experimental evidence is lacking, many of the properties of the chemisorption bond and the catalytic activity on metal surfaces can be explained by the surface restructuring model. These are a) higher activity for bond breaking on more open surfaces, b) bond breaking in narrow temperature ranges and sequentially as the temperature is increased, c) the higher surface dissociation probability of molecules with higher incident kinetic energy, and d) the structure sensitivity and insensitivity of catalytic reactions.