ACETATE FORMATION, STABILIZATION AND SURFACE EXPLOSION ON RH(111)

The adsorption of acetic acid on Rh(111) has been studied using molecular beam reaction spectroscopy and temperature-programmed desorption. A stable acetate is formed which decomposes at 390 K to yield CO2 and H-2 in the gas phase, leaving adsorbed carbon on the surface. In the presence of coadsorbed oxygens atoms, the pattern is completely altered, showing the presence of a stabilised acetate species manifesting an autocatalytic decomposition - a surface ''explosion''. The exact peak temperature and width is strongly dependent on the amount of oxygen which is coadsorbed, but the explosion features can be mathematically described with a model in which acetate species themselves block each others decomposition. The role of the adatom appears to be both as a poison and as a template for forming very ordered acetate adlayers.