Direct decomposition of nitrogen monoxide over a K-deposited Co(0 0 0 1) surface: Comparison to K-doped cobalt oxide catalysts

The influence of deposited potassium on the oxidation and NO reactivity of a Co(0 0 0 1) surface was studied using X-ray photoelectron spectroscopy. The formation of surface CoO was observed when the clean Co(0 0 0 1) surface was exposed to O₂ at 500 K. In contrast, the Co atoms on the K-deposited Co(0 0 0 1) surface remained at a lower oxidation state, CoO_x (0 < x < 1). No adsorption or dissociation of NO occurred on the CoO/Co(0 0 0 1) surface at 320 K, whereas a NO₂^? species formed on the oxidized K/Co(0 0 0 1) surface. This species is considered to be an intermediate in NO decomposition. It was concluded that the role of potassium was (i) to form the NO₂^? intermediate, and (ii) to keep the Co surface partially oxidized (CoO_x) as the active site for the dissociation of the NO₂^? species.