Electrooxidation of ethanol on carbon-supported Pt-Pd nanoparticles

Carbon supported Pt-Pd nanoparticles with varying Pt content have been investigated as anodes in direct ethanol fuel cell. To gain insight on possible changes in the mechanism of electrooxidation of ethanol on Pt when it is alloyed with Pd, the products' yield have been determined as a function of cell voltage and anode composition in combination with ex situ electrochemical experiments. It has been determined that ethanol electrooxidation current density decreased almost linearly as Pd amount increased, with small local maximum imposed on the linear activity plot for nanoparticles with 1:1 Pt:Pd ratio. This maximum has been correlated to increased acetic acid production, which was the result of so-called bi-functional mechanism. The relative amount of acetic acid has been found to be inversely proportional to amount of CO2 produced in wide range of conditions, where production of acetaldehyde was not correlated with production of other products. This observation was explained based on the possible paths of ethanol electrooxidation and competition between the adsorbed species for catalyst's surface. Overall the complex response of the system investigated can be understood in terms of interplay between bifunctional mechanism and ensemble effect and the electronic effects, albeit small, cannot be completely excluded. (C) 2012 Elsevier B.V. All rights reserved.