XPS and XAS Studies on Molecular and Dissociative Adsorption of Nitric Oxide on Rh

The adsorption and desorption behaviors of NO on polycrystalline Rh were investigated by X-ray absorption spectroscopy (XAS) and X-ray photoelectron spectroscopy (XPS). XAS analysis elucidated the symmetry of N-Rh bond of dissociatively adsorbed NO in addition to the molecular orientation and bond length of molecularly adsorbed NO. XPS analysis gave quantitative information on the formation of molecularly and dissociatively adsorbed species. Combination of both results suggested that the molecularly adsorbed NO with the axis normal to the Rh plane might not be the precursor of the dissociative adsorption.