REACTIVITY OF NIO AND K-DOPED NIO THIN-FILMS ON NI(100) WITH HYDROGEN AND METHANE

The formation and reactivity of multilayer NiO films, both with and without added potassium, have been investigated by using high-resolution electron energy loss spectroscopy, low-energy electron diffraction, and X-ray photoelectron spectroscopy (XPS). The kinetics of oxygen removal by hydrogen and methane were investigated by using time-resolved XPS. At surface temperatures above 600 K, the kinetics are consistent with reaction at the oxide surface, in combination with fast diffusion from subsurface layers. We have found a strong interaction between K and NiO, as evidenced by the formation of K-O bonds, by a high-temperature potassium thermal-desorption peak, and by an enhanced rate of NiO formation on K/Ni(100). For the K-doped NiO film, we found that the reaction rate at 800 K toward CH4 is accelerated, while the reaction rate with H2 is reduced.