Comparison of phosgene formation from adsorption of carbon tetrachloride on oxygen modified Ir(111) and oxygen modified Ir(110)

Abstract

The production of phosgene was observed when a pure carbon tetrachloride molecular beam was impinged on the oxygen modified Ir (111) and Ir(110) surfaces. Although the mechanism of phosgene formation is believed to be identical on the two surfaces, important differences in reactivity were observed. The phosgene production of oxygen modified Ir(111) was greater than the oxygen modified Ir(110) surface. Oxygen atoms are more tightly bound to the Ir(110) surface making it less reactive for the production of phosgene. Formation of the surface oxide on Ir(110) (which begins to occur if the surface is heated above 550 K) reduces adsorption of carbon tetrachloride, which necessarily decreases phosgene formation. The Ir(110) surface may also cause a more rapid decomposition of the adsorbed CCl2 intermediate. Phosgene production on oxygen modified Ir(110) also demonstrated a maximum at 500 K, whereas phosgene production on oxygen modified Ir(111) decreased with increasing temperature.