Preparation and evaluation of a multi-component catalyst by using a co-sputtering system for anodic oxidation of ethanol

In this study, a remarkable promotion of ethanol electrooxidation by a Pt-Ru-W alloy is reported for an improvement of the anodic reaction of a direct ethanol fuel cell (DEFC). Pt-based binary and ternary electrocatalysts including Pt-Ru-W deposited onto a Au substrate were prepared by co-sputtering process. By using this process, several metals can be arranged simultaneously and uniformly. The catalysts deposited onto Au were evaluated for anodic electrode in 1 mol dm−3 ethanol + 0.5 mol dm−3 sulfuric acid by electrochemical measurements. The performance of Pt-Ru-W was desirable in comparison to that of binary alloys, such as Pt-W, Pt-Sn and Pt-Ru, which exhibit higher catalytic activity than single Pt metal layer electrode. Ethanol electrooxidation on Pt-Ru-W alloy showed a cathodic shift in the onset potential and a higher current density than the binary alloy electrodes. It was found that Pt-Ru-W ternary catalyst effects to not only methanol oxidation reaction but also ethanol oxidation reaction and that the current density of ethanol oxidation with Pt-Ru-W is about 2/3 to that of methanol at 0.5 V versus Ag/AgCl. The onset potentials for the ethanol oxidation reaction matched well the anodic peak potentials of the background volutammograms, i.e., 0.15 V versus Ag/AgCl for Pt-Ru-W and 0.35 V versus Ag/AgCl for Pt-W and Pt-Ru electrodes. That is, it was postulated that the background peak current indicates the generation of oxide species like metalOH necessary to complete the ethanol oxidation to CO2.