Comprehensive Analysis on the Highly Active and Stable PdAu/C Electrocatalyst for Ethanol Oxidation Reaction in Alkaline Media

摘要

Both the catalytic activity and stability of palladium toward the ethanol oxidation reaction (EOR) in alkaline media are urgently required to be enhanced for the practical application of anion exchange membrane direct ethanol fuel cells (AEM DEFCs). The considerable improvement in the stability induced by the Au element has been well demonstrated; however, the catalytic activity from combining Pd with Au remains unsatisfied. Here, we successfully synthesize a series of PdxAuy/C electrocatalysts with different Pd/Au atomic ratios by a coreduction method, and in contrast to normal acknowledgments, the optimal PdAu/C sample not only possesses good stability but also has strikingly improved activity toward the EOR in alkaline media. Results show that the peak current density and degradation percentage for PdAu/C are, respectively, 84.16 mA/cm(2) and 12% and 59.73 mA/cm(2) and 67% for the pure Pd/C sample. It is anticipated that the striking activity toward the EOR can be attributed to an antipoisoning effect electronically induced by the Au addition, while the good stability can be ascribed to the formation of the stable Pd1Au1 alloy phase. It is also surprisingly revealed by physiochemical and electrochemical characterizations that there exists an unexpected monotone increasing trend for the promoting effect of Au content on Pd, and the compromise between the surface area specific activity and the number of active sites leads to the fact that the PdAu/C sample with Pd/Au atomic ratio of 1:1 has the highest mass activity toward the EOR in alkaline media.