Double perovskite oxides Sr2MMoO6 (M = Fe and Co) as cathode materials for oxygen reduction in alkaline medium

The oxygen reduction reaction (ORR) was studied on Sr2MMoO6 (M = Fe and Co) double perovskites, prepared by a solid-state reaction, in 0.5 M NaOH at 25 °C with a rotating disk electrode (RDE). The two oxide powders were characterized by X-ray diffraction, scanning electron microscopy and BET analysis. The electrochemical techniques considered are linear voltammetry, steady state polarization and ac impedance spectroscopy. The electrocatalysts (SFMO/C, SCMO/C) consisting of the double perovskite oxides and carbon (Vulcan XC-72) were mixed and spread out into a thin layer on a glassy carbon substrate. At room temperature, a significantly electrocatalytic activity is observed for both electrocatalysts. Compared to SFMO/C, the SCMO/C electrocatalyst was found to show a relatively high electrocatalytic activity for O2 reduction, which agrees well with the results obtained using the ac impedance spectroscopy.

Graphical abstractThe oxygen reduction over the surface of the electrocatalysts exhibiting high currents shows that SCMO/C electrocatalyst is slightly more active than the SFMO/C one. The relatively high electrochemical activity of the first may be ascribed to its high specific surface area providing a higher electrode current.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► SCMO/C and SFMO/C as catalysts for oxygen reduction were studied. ► SCMO/C catalyst showed a relatively high activity. ► A change in the reaction mechanism from a direct “four-electron pathway” to a “peroxide pathway” was observed.