Long-range ordering of stable, surface-bound intermediates: RAIRS, TPRS and STM studies of toluene oxidation on Ag(110)

Abstract

There is long-term interest in catalyst poisoning due to the buildup of carbonaceous species on catalytic metal surfaces. These species are often derived from the reactants themselves in reactions parallel to the primary catalytic cycle. Generally, these species are believed to be randomly distributed on the surface, with locally high concentrations. Using scanning tunneling microscopy (STM), we have found that upon annealing to 400 K a stable intermediate formed by partial oxidation of toluene on Ag(110) forms highly ordered domains with a length scale well over 1000 Å, limited only by the size of surface terraces. Temperature-programmed reaction spectroscopy and STM suggest the intermediate to be adsorbed benzoate species, C6H5CHOO, which decomposes to carbon dioxide and benzene near 550 K when heated.