Interaction of H2O,CO, and H2 with Pt(111) and Pt(111)+K surfaces |
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Authors: | J. E. Müller |
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Affiliation: | (1) Institut für Schicht- und Ionentechnik, Kernforschungsanlage Jülich, D-5170 Jülich, Fed. Rep. Germany |
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Abstract: | The potential energy and surface dipole were calculated as a function of the geometry of the coadsorbed systems using the cluster method and theoretical oscillation frequencies and work function changes were compared with experiment. It was found that the K fills unoccupied Pt 5d states and reduces the local polarizability of the metal. The H2O molecule binds to the K atom, such that the H atoms point towards the surface inducing an increase in the work function. For the CO molecule a charge transfer (KCO) through the surface stabilizes the bond and induces a change of adsorption place (on-topbridge). The K increases the tendency to H2 dissociation because of the local decrease of the work function. Zero-point energy effects add important dynamical features to the electronic H2- surface interaction. Three examples for the Pt(111)-H2 system are presented: (i) A virtual attractive potential well produced by the softening of the H-H bond near the surface, (ii) a virtual potential barrier for dissociation due to the hindering of molecular rotations at the surface, and (iii) a change in the apparent surface temperature in H2 desorption processes. |
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Keywords: | 73.20Hb |
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