Adsorption and decomposition of nitric oxide and ammonia on a stepped platinum single crystal surface

Abstract

The adsorption of nitric oxide and ammonia on the Pt(S)-[12(111) × (111)] surface has been studied using low energy electron diffraction, Auger electron spectroscopy, and thermal desorption spectroscopy; at saturation the adsorbed NO forms a 2 × 2 overlayer structure. Auger results and approximate desorption results confirm that the saturated surface corresponds to a coverage of about 3.8 × 10 14 adsorbed nitrogen containing species per square centimeter ( θ max) or about 1 4 of the platinum surface atom concentration. Partial dissociation of the desorbing NO occurs as evidenced by thermal desorption of N2 and O 2 from the surface. The fraction of adsorbed nitrogen desorbed as N2 decreases from 100% below 0.1 θ max to about 30% at saturation. A surface saturated with ammonia corresponds to about 9 × 10 13 nitrogen containing species per cm 2. Significant dissociation of the desorbing NH 3 occurs at all coverages studied as evidenced by thermal desorption of N 2 and H 2.