THE ADSORPTION OF CO, O2, AND H-2 ON PT(100)-(5X20)
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The adsorption/desorption characteristics of CO, O2, and H2 on the Pt(100)-(5 20) surface were examined using flash desorption spectroscopy. Subsequent to adsorption at 300 K, CO desorbed from the (520) surface in three peaks with binding energies of 28, 31.6 and 33 kcal gmol-1. These states formed differently from those following adsorption on the Pt(100)-(1 1) surface, suggesting structural effects on adsorption. Oxygen could be readily adsorbed on the (520) surface at temperatures above 500 K and high O2 fluxes up to coverages of 2 3 of a monolayer with a net sticking probability to ssaturation of 10-3. Oxygen adsorption reconstructed the (5 20) surface, and several ordered LEED patterns were observed. Upon heating, oxygen desorbed from the surface in two peaks at 676 and 709 K; the lower temperature peak exhibited atrractive lateral interactions evidenced by autocatalytic desorption kinetics. Hydrogen was also found to reconstruct the (5 20) surface to the (1 1) structure, provided adsorption was performed at 200 K. For all three species, CO, O2, and H2, the surface returned to the (5 20) structure only after the adsorbates were completely desorbed from the surface. 1981.
