Modification of palladium surfaces by bismuth adatoms or clusters: Effect on electrochemical activity and selectivity towards polyol electrooxidation

The syntheses of Bi-modified Pd catalysts with a controlled size distribution are presented as well as the characterizations of their structures and of their surfaces. Effects of the modification either of non-supported Pd nanospheres by spontaneous deposition of Bi or of carbon-supported Pd-based nanomaterials by decoration with bismuth clusters on the electrocatalytic activity towards glycerol electrooxidation were evaluated and compared in alkaline medium. The method of bismuth deposition has a dramatic effect on the activity of the palladium based catalysts: spontaneous deposition of Bi on non-supported Pd nanoparticles leads to relatively low activity enhancement, whereas decoration of carbon-supported Pd nanoparticles by Bi2O3 and Bi(OH)3 clusters leads to very high activity increase at low overpotentials. In situ infrared spectroscopy indicated that the modification of Pd by Bi did not affect the selectivity of glycerol oxidation, whereas in the case of Pt containing catalyst, a dramatic change in selectivity occurred at low potentials.