Adsorption of gases on Pt/Ni (111) systems

The chemisorptive properties of bimetallic systems could be sometimes very different in comparison with those of the pure metallic components. The (1 1 1) face of Pt-50-Ni-50 alloys has shown a clear decrease in their chemiso rptive capacity when compared with Pt(1 1 1) or Ni(1 1 I). In the present w ork, we study the adsorption of the H atom as well as CO and benzene molecu les on a Pt/Ni(1 1 1) surface. Our approach was based on a semiempirical mo lecular orbital method in the cluster approximation. The binding energy of different molecules decreases significantly with respect to the pure metal surfaces, in agreement with the available experimental information. These r esults can be related and explained taking into consideration the electroni c changes of the Pt states in the overlayer. (C) 2000 Elsevier Science B.V. All rights reserved.