COADSORPTION OF BENZENE AND HYDROGEN ON RU(001)

Coadsorption of benzene and hydrogen on the close-packed plane of Ru has been investigated. Using HREELS and TDS, we show that desorption of hydrogen off the benzene-covered surface is indeed governed by the dehydrogenation process, as proposed earlier. The signal in question can be easily separated from the corresponding one of coadsorbed hydrogen, which desorbs at clearly lower temperatures. Only slight mutual influences exist in the vibrational modes of both coadsorbate species at 250 K. Clear evidence for isotopic exchange between H(ad) and C6D6 at temperatures considerably below dehydrogenation is found by TPD as well as by vibrational spectroscopy. These exchange reactions are found to be fully reversible, but only a fraction of the hydrogen can be exchanged. Reaction mechanisms as well as possible explanations for this particular behavior are discussed.