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Ethanol oxidation reaction (EOR) on Pd 2 Ru/C and Pd/C catalysts in alkaline media is studied comprehensively by cyclic voltammetry, chronoamperometry, in situ FTIR, single fuel cell test and electrochemical impedance spectroscopy measurements. The results show that, as compared to Pd/C, Pd 2 Ru/C favors acetaldehyde formation and hinders its oxidation. Based on X-ray absorption data, which evidence that Ru promotes a larger electronic vacancy of the Pd 4d band, it is expected that the formation of adsorbed ethoxy is favored on Pd 2 Ru/C and followed by its oxidation to acetaldehyde facilitated by oxygenated species provided by Ru. In contrast, acetaldehyde oxidation is more difficult on Pd 2 Ru/C than on Pd/C likely because the adsorption energy of the reactive species is increased. We also show that the performance of Pd 2 Ru/C anode in alkaline direct ethanol fuel cell (ADEFC) is initially better but degrades much more rapidly than that with Pd/C anode under the same test conditions. The degradation is demonstrated to result from the accumulation of large amounts of acetaldehyde, which in alkaline media forms dimers by the aldol condensation reaction. The dimers tend to be responsible for blocking the active sites for further ethanol oxidation. This comprehensive study provides new understandings of the roles of Ru in Pd 2 Ru/C for EOR in alkaline media, unveils the causes of the performance degradation of fuel cells with Pd 2 Ru/C and demonstrates that initial good performances are not necessarily a valid criterion for selecting appropriate anode catalysts for ADEFC applications. [ABSTRACT FROM AUTHOR]

The activity of carbon supported palladium-based catalysts towards ethanol oxidation reaction in alkaline medium is investigated. To this end, Pd and Pd x Ru (x = 1, 6, 12) materials are synthesized supported on Vulcan XC72R by a modified impregnation method. These materials are characterized physicochemically and their composition varies between 40 and 50 wt. % of metal content. The mean size of nanoparticles is below 4 nm, and the size of the majority of particles ranges from 2 to 6 nm. The catalytic activity of these samples is also tested in half-cell and alkaline membrane direct ethanol fuel cell (AMDEFC). Lower onset potential and higher oxidation current densities is observed in palladium-rich bimetallic catalysts. By using the prepared samples as anode of AMDEFC and a commercial membrane of polybenzimidazole as solid electrolyte, the maximum power density is observed for Pd 12 Ru/C, 97 mW cm −2 , almost doubling the value achieved by the catalyst Pd/C (50 mW cm −2 ), and above the obtained by commercial PtRu/C catalyst (89 mW cm −2 ). [ABSTRACT FROM AUTHOR]