FIZIKA A 4 (1995) 2, 171-179

INTERACTION OF H₂ (D₂) AND POTASSIUM WITH Ag(111) AND Ag(110)

VLADIMIR ZHUKOV On leave from the Technical University St. Petersburg, Russian Federation.,
KLAUS D. RENDULIC and ADOLF WINKLER
Institut für Festkörperphysik, Technische Universität Graz, Petersgasse 16, A-8010 Graz, Austria

Received 7 April 1995

Adsorption and coadsorption of H₂ (D₂) and potassium on the single-crystal silver surfaces (111) and (110) have been studied using thermal desorption spectroscopy, work function measurements and LEED. Atomic hydrogen was used to cover the silver surfaces, since a very high activation barrier makes molecular adsorption impossible. From the Ag(111) surface hydrogen desorbs in a single peak with a close to second order reaction and a desorption energy of 29.4 kJ/mol. Hydrogen desorption from Ag(110) is characterized by two overlapping desorption peaks which are very sensitive to small amounts of water coadsorption. Upon hydrogen saturation (0.65 ML) on Ag(111), the work function increases by 240 meV. Coadsorbed potassium shifts the desorption temperature for H₂ dramatically by 250 K to higher temperature on both surfaces. Simultaneous desorption of hydrogen and potassium on both silver surfaces with a ratio of 1 K-atom to 4H₂ molecules indicates the formation of a potassium-hydrogen complex in the coadsorbate.

UDC 538.971
PACS 68.45.Da

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