Adsorption of H 2 and CO on clean and oxidized (110) Pt

Abstract

Binding states and sticking coefficients of CO and H 2 on clean and oxide covered (110) planes of Pt are examined using flash desorption mass spectrometry to characterize binding states and Auger electron spectroscopy (AES) to characterize oxide densities. It is found that on the oxide both adsorbates have new binding states with significantly higher binding energies than on the clean surface. For H 2 the binding states associated with the clean surface are also shifted to higher energies as the oxide coverage increases. The oxide state for H 2 desorbs with first order kinetics, and isotope exchange experiments are used to examine exchange between isotopes and between states. The initial sticking coefficients for CO are 1.0 and 0.85 on clean and oxidized surfaces, and the initial sticking coefficient for H 2 increases from 0.15 on the clean surface to 0.28 on the oxidized surface. Enhanced bonding on the oxide is interpreted in terms of models involving microfacets, electronic structure alteration, and compound formation.