ADSORPTION, DESORPTION AND SURFACE-REACTIONS OF CO AND NO ON PD(320)

Adsorption, desorption and a surface reaction between coadsorbed CO an d NO on a stepped Pd{320} (Pd(S)[3(110) x (100)]) surface have been st udied using molecular beam surface scattering (MBSS), temperature-prog rammed desorption/reaction (TPD/TPR) and X-ray photoelectron spectrosc opy (XPS). CO adsorbs molecularly on Pd{320} with an initial sticking probability close to unity at 300 K, and reversibly desorbs upon heati ng according to the first-order desorption kinetics. NO adsorption on Pd{320} is molecular in the temperature range of 300-400 K as indicate d by MESS and XPS. NO desorbs molecularly in addition to the formation of relatively large amounts of N-2 and N2O near 500 K. Coadsorbed NO and CO are observed to react upon heating to produce an extremely narr ow TPR peak of CO2 at similar to 470 K. The location and half-width of the CO2 TPR peak are almost independent of the initial coverages of C O and NO, which indicates an autocatalytic behaviour of the NO-CO reac tion kinetics on Pd{320}. (C) 1998 Elsevier Science B.V. All rights re served.