Initially, the electron characteristics of solids have been discussed and proposed as a guide to their catalytic activity . More specifically, the activity of a metal was considered to depend on the values of the electronic work function, the energy density of electron levels at the Fermi surface and the gradient therein . For a series of binary solid solutions containing one of the group 8 elements (Ni, Pd or Pt) together with one of the group I elements (Cu, Ag or Au) and the binary alloys of iron, cobalt and nickel, the efficacy in multiple bond saturation or in dehydrogenation was found to depend largely on the number and the characteristics of the holes in the d-bands of the alloys. Hence, the influence of the electronic properties of a catalyst on its activity was discussed in a nonlocal picture, by relating it to different bulk electronic properties . Modifications in the catalytic activity of a metal catalyst by addition of a second metal were explained by donation or removal of electrons to/from the dominant component, comparable to the concept of Hume-Rothery phases .