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Nitrous oxide (N 2 O) 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 Sr 2 Fe 1·5 Mo 0·5 O 6- δ (SFMO) as electrocatalyst for N 2 O 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 O 2 and N 2 O species, particularly at lower temperatures, where N 2 O thermal decomposition is lower. In terms of electrocatalytic properties, galvanostatic transients were used to assess N 2 O electroreduction on the SFMO electrode. The results showed that, after cathodic polarization, the N 2 O 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 N 2 O reduction can be an attractive tool to be implemented for the reduction of this environmentally damaging gas in SOFC systems. • The viability of SFMO as electrocatalysts for N 2 O reduction is demonstrated. • The N 2 O electroreduction mechanism on the SFMO cathode is outlined. • Competition between O 2 electroreduction and N 2 O decomposition is suggested. [ABSTRACT FROM AUTHOR]

A novel layered double perovskite-based electrode of composition Ba 2 NiMoO 6-δ (BNMO) is proposed for application in Protonic Ceramic Electrochemical Cells (PCECs). Structural characterization by X-ray diffraction (XRD) revealed good chemical compatibility with a BaCe 0.7 Zr 0.1 Y 0.2 O 3- δ (BCZY712) electrolyte and phase stability in oxidizing atmospheres. In this study, symmetrical cells of both the pure BNMO electrode and a composite electrode with 50 vol% of BCZY712 material were prepared by screen printing and sintering in air at 950 °C. Microstructural characterization by Scanning Electron Microscopy (SEM) showed good adhesion of the electrode films with the substrate, while Energy-dispersive Spectroscopy (EDS) revealed good percolation of both phases in the case of the composite electrode. Electrochemical studies made by Electrochemical Impedance Spectroscopy (EIS) on the pure BNMO electrode demonstrated that the total polarization resistance was lower in wet conditions in the case of N 2 atmospheres, corroborating a potential protonic contribution, while in O 2 atmospheres this term was similar between wet and dry conditions, due to dominant p-type electronic conductivity. Conversely, performance was aggravated by the addition of the BCZY712 composite phase; a result clarified to be due to an insufficient level of electronic conductivity in the composite electrode. To the best of our knowledge this is the first study of BNMO for proton conducting applications, providing important information on preparation, compatibility and electrochemical performance, as required for its further optimization. • Pure Ba 2 NiMoO 6-δ (BNMO) and composite BNMO + BaCe 0.7 Zr 0.1 Y 0.2 O 3- δ (BCZY712) electrodes are fabricated. • BCZY712 and BNMO mixtures shown to be chemically stable up to 1100 °C in air and with suitable thermal expansion match. • R p of pure BNMO electrode shows water vapor pressure dependence in N 2 , corroborating a potential protonic contribution. • Comparison between BNMO and composite electrodes revealed electronic transport as the key property for further improvement. [ABSTRACT FROM AUTHOR]

The mixed conducting Sr 2 Fe 1·5 Mo 0·5 O 6- δ (SFM) is a promising cobalt-free oxygen electrode for solid oxide fuel cells (SOFCs). Therefore, we report on modifying the electrode microstructure of a single-phase SFM and the formation of a new composite electrode with ∼34 vol% of Ce 0.8 Pr 0.2 O 2- δ (CPO, which also exhibits mixed conducting behavior). In our assessment, we tested the impact of repeated drying-screen-printing cycles on the deposition of the electrode films. Such a modification resulted in an optimal thickness within the 40–50 μm range while providing a higher solid fraction within the electrode-electrolyte region. This factor decreased the total polarization resistance for both electrode materials, as determined by electrochemical impedance spectroscopy. The results also indicated enhanced surface exchange kinetics with the addition of CPO, where the incorporation reaction is expected to occur at the SFM/CPO interface. Nevertheless, the overall performance of the composite electrode was hampered by an insufficient global electronic conductivity. As a result, the reduced effective electroactive area in the SFM/CPO composite electrode hindered the interfacial charge-transfer process. Our work provides an important investigation of both microstructural and compositional criteria for the future development of SOFC cathode design. • The effect of layer deposition on the R pol of SFM electrodes was examined. • The SFM/CPO composite was first evaluated as an oxygen electrode for SOCs. • The Gerischer element suggested improved oxygen reaction kinetics with CPO. • The reduced effective area impaired interfacial charge transfer in the composite. • The addition of CPO (∼34 vol%) increased the R pol of SFM electrodes due to its lower electronic conductivity. [ABSTRACT FROM AUTHOR]