Effects of UPD adlayer of foreign metals on the oxidation of ethanol on carbon supported Pt-based catalysts

Abstract

Oxidation of ethanol was studied at SnUPD, RuUPD and RhUPD modified and unmodified Pt/C, Pt3Sn/C and Pt3Ru2/C catalysts. All unmodified catalysts were characterized by XRD. Potentiodynamic and chronoamperometric measurements were used to establish their catalytic activity for ethanol oxidation. Underpotential deposition of small amount of each one adatoms (~10%) enhanced the activity of Pt/C and Pt3Sn/C catalysts. The onset potential is shifted for ~0.05 V towards lower values and the current densities in the whole potential region studied are up to two times higher regarding to unmodified catalysts. On the other hand, addition of SnUPD or RhUPD slightly increases the activity of Pt3Ru2/C, while the presence of Ruad adlayer decreases its activity for ethanol oxidation. Catalytic action of Sn and Ru adatoms was associated mostly with their ability to adsorb oxygen containing species at lower potentials than Pt, permitting bifunctional mechanism to proceed. Rh adatoms act on the C-C bond breaking activation increasing in this way the activity of modified surfaces for the ethanol oxidation. Pt3Sn/C modified by ~10% SnUPD is the best catalyst studied. Its activity enhanced more than two times in respect to Pt3Sn/C catalyst.