Adsorption of NO on potassium-modified Cu (100) vicinal surfaces

The interaction of nitric oxide, NO, with clean and potassium-modified copper surfaces: Cu (001), Cu (119) and Cu (115), in the temperature range of 125-800 K, was investigated using photoelectron spectroscopy based on synchrotron radiation (SR-PS). At 125 K nitric oxide, on the non-modified surface, dissociates and molecules of N₂O obtained by a reaction dominates on the substrate. The sticking coefficient increases with the presence of steps on the surface. Successive annealing of the surface leads to desorption and dissociation of the adsorbed species, at 500 K to chemisorption of remaining oxygen and nitrogen indicating formation of copper oxide and copper nitride. Pre-adsorbed potassium observably increases the sticking coefficient and the alkali metal reacts with the incoming nitric oxide molecules. Apart from the mentioned species, the presence of a nitrate salt (K-NO_x) is deduced from the spectra. Heat treatment of the potassium modified copper causes surface reactions with the appearance of potassium compounds as well. Among the three Cu surfaces, changes concerning the sticking coefficient and different possibility of nitrogen capture after adsorbate dissociation were found. Surface reactions follow the same pattern on the three surfaces.