EFFECT OF SURFACE COMPOSITION AND STRUCTURE ON ELEMENTARY CHEMICAL REACTIONS ON METALLIC SUBSTRATES.

Studies of chemical reactions on well-defined surfaces have considerable potential for providing fundamental knowledge of surface reactivity and guidelines for the understanding of catalytic materials. This paper discusses the author's work on the effect of surface composition and structure on the adsorption and desorption of H//2, CO, H//2O, CO//2, HCOOH, H//2CO, CH//3OH, and CH//3CH//2OH on single crystals of nickel, copper, and copper-nickel alloys. In addition, the results are presented on his studies concerning the kinetics and mechanism of three mode reactions, (1) the decomposition of carboxylic acids, (2) the oxidation of alcohols, and (3) the oxidation of formaldehyde on these surfaces. It is demonstrated that the application of the methods of surface science to the study of heterogeneous reactivity affords the opportunity to elucidate the nature of many interesting effects. Among these are (1) structure sensitivity; (2) the effects of adlayers, including poisons or promoters, on activity and selectivity; (3) the nature of adsorbate/adsorbate interactions, including such interactions as CO and H//2; (4) the existence of stable reaction intermediates and the rate constants for the elementary reaction steps in which they engage; and (5) the elucidation of the inter- and intramolecular mechanisms of reactions occurring on the surface.