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

Palladium gold alloy powder (PdAu2) was synthesized by reduction of the [Pd(NH3)4][AuCl4]2 complex with H2 at 90 °C, and then was additionally heated in a C2H4 (PdAu2–Cx) or H2 flow (PdAu2–H2) 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 PdAu2 alloy suffers marginal changes after heating under C2H4 atmosphere, and decreases as a result of heating in a H2 flow. Hydrogen oxidation reaction (HOR) over the catalysts was studied using rotating disk electrode at 25 °C in 0.1 M HClO4 in pure H2 and in the presence of 1100 ppm of CO. Heat-treatment of the PdAu2 alloy under H2 does not improve its HOR activity and CO tolerance (normalized to Pd and total metal surface area), while the PdAu2–Cx catalyst exhibits substantially enhanced catalytic performance in the HOR both in the absence and in the presence of CO as compared to the parent PdAu2 alloy. The enhanced activity of the C2H4-treated PdAu2 alloy is explained by the promoting action of carbon atoms incorporated into the alloy structure during treatment under C2H4 atmosphere. This supposition is approved by the fact that mild oxidative treatment of the PdAu2–Cx sample degrades notably its catalytic activity.

Figure optionsDownload as PowerPoint slideHighlights
► [Pd(NH3)4][AuCl4]2 complex as precursor for PdAu2 catalyst for HOR.
► Heat-treatment of PdAu2 in C2H4 flow enhances catalytic activity of alloy in HOR.
► Heat-treatment of PdAu2 in C2H4 flow enhances CO tolerance of alloy during HOR.
► Rise of activity of C2H4-treated PdAu2 is due to incorporation of C atoms in alloy.