Implication of palladium geometric and electronic structures to hydrogen activation on bulk surfaces and clusters

A great body of theoretical results obtained preferentially with density-fu nctional methods in the last decade is analyzed with emphasis on the relati onship between the orientation of the surface for semiinfinite mono-metalli c bulk palladium and the cluster-size for finite palladium particles. It is demonstrated that the crystallographic orientation of a surface influences the local electronic structure and the geometric configuration of catalyti c centers and this way changes their catalytic properties. Weakly bound mol ecularly adsorbed states and atomic adsorbates in the most reactive low-coo rdinated positions are especially sensitive to such changes. The unique fea ture of small palladium clusters, their ground state magnetism affects main ly the dynamics of dissociative adsorption and leads to the stabilization o f pre-dissociated forms of adsorbate. (C) 2001 Elsevier Science B.V. All ri ghts reserved.