THERMALLY ACTIVATED OXIDATION OF NH3 ON PT(111) - INTERMEDIATE SPECIES AND REACTION-MECHANISMS

Results of a study of the thermally activated reactions of ammonia with atomic and molecular oxygen on Pt(111) are presented. Ultrahigh vacuum, surface sensitive techniques such as temperature programmed desorption and reaction spectroscopies (TPD, TPRS), electron energy loss spectroscopy (EELS), Auger electron spectroscopy (AES), and low energy electron diffraction (LEED) were used in this study. H2O, NO, and N-2 are produced in various amounts depending on reactant concentrations. Stable intermediate species OH, NH, and NH2 are identified by EELS. Assignment of reaction mechanisms based on liberation of hydrogen via stepwise N-H bond cleavage by atomic oxygen and OH is made through an EELS analysis of reaction intermediates and a TPRS analysis of NH3 coverage dependences of product distributions. A forthcoming report will describe the photo-induced reaction of NH3 and O-2 coadsorbed on Pt(111).