O2-enhanced methanol oxidation reaction at novel Pt-Ru-C co-sputtered electrodes

A Pt-Ru-C electrode has been developed using a co-sputtering technique for use as the anode catalyst of a mixed-reactant fuel cell. The physical and electrochemical characteristics of the electrodes demonstrate that co-sputtered Pt and Ru form a Pt-Ru alloy. The crystallite sizes of the catalysts investigated in this study are reduced by the addition of C to the Pt-Ru alloy. Cu stripping voltammograms suggest that the sputtering of C and the formation of the Pt-Ru alloy synergically increase the electrochemical surface area of the electrodes. The methanol oxidation performances of the prepared electrodes were evaluated in N-2 and O-2 atmospheres; the Pt-Ru-C electrodes achieve an O-2-induced negative shift in the onset potential of the methanol oxidation (E-onset) and enhance the methanol oxidation current density in the O-2 atmosphere. The mechanism of O-2-enhanced methanol oxidation with a negative E-onset at the Pt-Ru-C electrodes is attributed to a change in the electronic structure of Pt due to the formation of Pt-Ru alloy and the generation of O-based adsorption species by the reduction of O-2. Finally, the composition of the Pt-Ru-C electrode for the O-2-enhanced methanol oxidation with a negative E-onset was found to be optimal at an atomic ratio of Pt: 0.24-0.80, Ru: 0.14-0.61, and C: 0.06-0.37. (C) 2012 Elsevier Ltd. All rights reserved.