Pt-Rh Surfaces Research Articles

Mechanism of the ammonia formation from NO-H2. A model study with Pt-Rh alloy single crystal surfaces

The reduction of NO by H2 was studied over three different Pt-Rh single crystal surfaces, i.e. Pt-Rh(111), (410) and (100). The adsorption and dissociation of NO was studied by HREELS, LEED, XPS, AES and TDS. It was found that the dissociation of NO and its reaction with H2 is very surface structure sensitive. The selectivity towards nitrogen and the dissociation activity increases in the same order, i.e. Pt-Rh(111) < (100) < 410). Nitrogen atoms were easily hydrogenated at 400 K in hydrogen to NH x (x = 1 or 2) on the surface. A model is proposed in which the selectivity of the NO-H2 reaction over Pt-Rh surfaces is determined by the relative amounts of hydrogen, NO and nitrogen adatoms on the surface.