A molecular beam surface scattering study of ammonia oxidation on the Pt(111) crystal face

The catalyzed reaction of ammonia and molecular oxygen on a Pt(111) single-crystal surface was studied over the crystal temperature range of 550-1100 K. A molecular beam-surface scattering technique was utilized and two-photon ionization was used to probe the NO product. Two different NO production kinetics were observed. These could be characterized by activation energies of 29 ± 4 and 14 ± 3 kcal/mol for the faster and slower processes, respectively. The internal energy distributions of the scattered NO product, e.g., rotational and vibrational energies, were found to have a lower temperature than the crystal temperature. Possible reaction mechanisms are discussed.