An XPS study of carbon monoxide and nitric oxide adsorption on platinum (410): Unusual dissociation activity

The adsorption of NO and CO on platinum (410) is studied by X-ray photoemission spectroscopy (XPS). It is found that the (410) surface shows unusual activity for NO and CO bond breaking. CO is found to adsorb molecularly on Pt (410) at 300 K, but it partially dissociates upon heating to 500 K. NO is found to adsorb dissociatively under all conditions studied. By comparison, the low index faces of platinum and stepped surfaces considered previously give negligible dissociation of CO and negligible dissociation of NO up to 450 K. The (410) surface is also unusual from an orbital symmetry standpoint; in fact, it was predicted to be unusually active for NO and CO bond breaking based on Woodward-Hoffman ideas. The present results show, then, that Woodward-Hoffman (i.e., orbital symmetry conservation) methods could yield valuable insights into the nature of active sites on single crystal catalysts.