ABSTRACT
A general interpretation of the structure of Pd catalysts promoted by metal ions is given which is based on thermodynamic (electrochemical) considerations and in situ measurement of the oxidation state. The promoter may be reduced either to metal forming adatoms or several atomic layers, or to lower valence state ions, depending on the relative position of catalyst and metal deposition potentials. The role of reaction conditions and the presence of organic compounds are discussed. As examples, the catalytic performance of supported Pd catalysts modified by Ge4+, Pb2+, Cu2+ and Sn2+ ions are studied in hydrogenation, hydrodehalogenation and hydrogenolysis reactions.
