Ethylene epoxidation on Ag/YSZ electrochemical catalysts: Understanding of oxygen electrode reactions

Thomas Cavoué (1) , A. Caravaca (1) , Ioanna Kalaitzidou (1) , F. Gaillard (2) , Mathilde Rieu (3, 4) , Jean-Paul Viricelle (3, 4) , P. Vernoux (1)

1 CARE - IRCELYON-Catalytic and Atmospheric Reactivity for the Environment
2 IRCELYON - Institut de recherches sur la catalyse et l'environnement de Lyon
3 PTSI-ENSMSE - Département Procédés de Transformations des Solides et Instrumentation
4 LGF-ENSMSE - Laboratoire Georges Friedel

In this study, we have investigated, for the very first time, the oxygen electrode reactions on Ag/YSZ electrochemical catalysts both in oxygen and under reaction conditions compatible with the ethylene epoxidation reaction. Electrochemical Impedance Spectroscopy (EIS) in combination with in-situ Raman spectroscopy and catalytic activity measurements were used to identify and understand the main oxygen reaction pathways. The results obtained suggested that the rate limiting step under an O₂ reaction atmosphere (at 300 °C) is the O₂ adsorption/dissociation process on the Ag catalyst-electrode. In addition, the polarization resistance increased with time under the presence of O₂. This was attributed to the formation of Ag₂O on the catalyst surface or near surface, which limits the oxygen electrode reactions. Finally, we observed that the addition of ethylene in the feed stream hinders the electrode reaction, due to its competitive chemisorption with oxygen on Ag. These results give new insights into the design of selective Ag/YSZ catalyst for ethylene epoxidation.

Mots clés: Ethylene epoxidation; Oxygen electrode reaction; Electrochemical Impedance Spectroscopy (EIS); Ag/YSZ

Domaines: Autre; Génie des procédés

Thomas Cavoué, A. Caravaca, Ioanna Kalaitzidou, F. Gaillard, Mathilde Rieu, et al.. Ethylene epoxidation on Ag/YSZ electrochemical catalysts: Understanding of oxygen electrode reactions. Electrochemistry Communications, 2019, 105, pp.106495. ⟨10.1016/j.elecom.2019.106495⟩. ⟨hal-02184495⟩