Electrocatalytic Activity of Supported Au-Pt Nanoparticles for CO Oxidation and O2 Reduction in Alkaline Medium

Various Pt- and Au-based nanocatalysts prepared by water-in-oil microemulsion method were used to study CO stripping and the oxygen reduction reaction in alkaline medium. It was shown that the particle size increases with the amount of gold in the bimetallic composition, which could be explained by rapid reduction kinetic of gold salt in comparison to that observed with platinum one. This results in the faster formation of nuclei followed by a more rapid growth of the particles. Geometric effects responsible for strong adsorption of CO on high content gold-platinum nanoparticles are discussed as well as the appearing special feature of gold during CO stripping experiments. The absence of a prepeak potential on Au70Pt30/C nanoparticles could be due to a very small amount of weakly adsorbed CO on the surface. A CO-adsorbed layer seems to be so stable and compact that it does not present a formation of holes involving a low decrease in repulsive interactions between CO molecules and a shift of the main oxidation peak towards positive potentials. Moreover, the modification of the strength of the Pt-OH bond due to the presence of gold was described as well as the high catalytic activity of gold-based nanoparticles toward the oxygen reduction reaction in 0.1 M NaOH.