Impact of the modification of carbon-supported, Pt-based catalysts by irreversibly adsorbed Sn, Ru and Rh on ethanol oxidation

Abstract

The oxidation of ethanol was studied at Snad-, Ruad- and Rhadmodified and unmodified PtC, Pt3Sn/C and Pt3Ru2/C catalysts. Potentiodynamic, quasi-steady-state and chronoamperometric measurements were used to investigate the activity and stability of the catalysts. Irreversible adsorption of a small amount of each of the adatoms (?10 % surface coverage) enhanced the activity of the Pt/C and Pt3Sn/C catalysts. The onset potential was shifted by ?50 mV towards lower values and the current densities over the whole studied potential region were up to two times higher with respect to the unmodified catalysts. On the other hand, the addition of Snad or Rhad slightly increased the activity of Pt3Ru2/C, while the presence of Ruad decreased its activity for ethanol oxidation. The catalytic action of Snad and Ruad was associated mostly with their ability to adsorb oxygen-containing species at lower potentials than Pt, permitting a bifunctional mechanism to proceed. Rhad also acted on the C-C bond breaking activation as well as source of oxygen containing species, increasing in this way the activity of the modified surfaces for ethanol oxidation.