Strontium iron molybdenum oxide as electrocatalyst for nitrous oxide reduction in solid oxide fuel cells

Abstract

Nitrous oxide (N2O) is an environmentally damaging gas and alternative methods for its abatement are needed. In this work, we developed an electrochemical route using the mixed ionic electronic conductor Sr2Fe1·5Mo0·5O6-δ (SFMO) as electrocatalyst for N2O reduction in the temperature range of 600–800 °C, at ambient pressure, for application in Solid Oxide Fuel Cells (SOFCs). The electrode mechanism, studied by electrochemical impedance spectroscopy (EIS), is discussed to involve a competition between both O2 and N2O species, particularly at lower temperatures, where N2O thermal decomposition is lower. In terms of electrocatalytic properties, galvanostatic transients were used to assess N2O electroreduction on the SFMO electrode. The results showed that, after cathodic polarization, the N2O conversion increases. In particular, a highest Faradaic efficiency (|Λ|) of 3.94 was obtained at 600 °C. The reversibility of the mechanism was also assessed, and the results showed that the reaction rate returns to its open circuit value upon current interruption. This work indicates, therefore, that the electrochemical promotion of N2O reduction can be an attractive tool to be implemented for the reduction of this environmentally damaging gas in SOFC systems.