Hydrogen electrooxidation over palladium–gold alloy: Effect of pretreatment in ethylene on catalytic activity and CO tolerance

Abstract Palladium gold alloy powder (PdAu 2 ) was synthesized by reduction of the [Pd(NH 3 ) 4 ][AuCl 4 ] 2 complex with H 2 at 90 °C, and then was additionally heated in a C 2 H 4 (PdAu 2 –C x ) or H 2 flow (PdAu 2 –H 2 ) at 300 °C. The samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and by a set of electrochemical methods. The Pd:Au ratio on the surface of the PdAu 2 alloy suffers marginal changes after heating under C 2 H 4 atmosphere, and decreases as a result of heating in a H 2 flow. Hydrogen oxidation reaction (HOR) over the catalysts was studied using rotating disk electrode at 25 °C in 0.1 M HClO 4 in pure H 2 and in the presence of 1100 ppm of CO. Heat-treatment of the PdAu 2 alloy under H 2 does not improve its HOR activity and CO tolerance (normalized to Pd and total metal surface area), while the PdAu 2 –C x catalyst exhibits substantially enhanced catalytic performance in the HOR both in the absence and in the presence of CO as compared to the parent PdAu 2 alloy. The enhanced activity of the C 2 H 4 -treated PdAu 2 alloy is explained by the promoting action of carbon atoms incorporated into the alloy structure during treatment under C 2 H 4 atmosphere. This supposition is approved by the fact that mild oxidative treatment of the PdAu 2 –C x sample degrades notably its catalytic activity.