Methanol decomposition on Ru(0001) during continuous exposure at room temperature

Using infrared vibrational spectroscopy, we have studied the chemical reactivity of methanol on Ru(0001) under experimental conditions closer to real catalysts than those existing in most of the literature. We have performed experiments in the pressure range from 10− 8 to 10− 3 mbar, exposing the surface to large gas doses at room temperature. We show the co-existence of two active paths: one involves the complete dehydrogenation of methanol into CO, the other one promotes the scission of the CO bond of methanol, leaving carbon and oxygen on the surface, which, after large exposures, deactivate the surface towards a further evolution of the molecular adlayer. In no case, the presence of stable reaction intermediates is detected along either of the two reaction paths. We have compared the behavior of flat ruthenium surfaces with those having a variable concentration of controlled surface defects. Surface defects, mainly steps, seem to accelerate the rate of both reaction paths, but do not activate any new reaction path or stabilize intermediates.