Mechanistic insights into N2O abatement over SFCMO-based direct ammonia solid oxide fuel cell: polarization behavior and environmental application

Solid-oxide fuel cells (SOFCs) are investigated for N 2 O abatement, targeting the decomposition of this potent greenhouse gas while generating electricity as by-product. Although O 2 is typically the oxidant in SOFCs, N 2 O can also serve this role, as N 2 O decomposes into N 2 and O 2 under operating conditions. This work analyzes a double-perovskite Sr 2 Fe 1.45 Co 0.05 Mo 0.5 O 6− δ (SFCMO) as a cathode for N 2 O reduction. Dilatometry indicated an average thermal expansion coefficient of 10.7 x 10 -6 °C -1 , compatible with common SOFC electrolytes. The SFCMO|GDC|YSZ|Ni-YSZ cell was tested with O 2 or N 2 O, while the anode was fueled with NH 3 . Electrochemical characterization of the cell was performed via electrochemical impedance spectroscopy (EIS) and distribution function of relaxation times (DFRT) between 600 – 750 °C. Analysis indicated that surface exchange was the rate-limiting step of the oxygen reduction reaction. N 2 O as a source of oxygen atoms, which effectively lowers the oxygen partial pressure ( ) at the cathode, may increase the concentration of oxygen vacancies and enhance surface redox activity. Accordingly, the cell supplied with N 2 O exhibited more than a 30 % increase in power density compared to operation with O 2 , with an average N 2 O conversion of ∼41.7 %. These findings demonstrate SFCMO electrode as an efficient electrocatalyst for N 2 O abatement for intermediate-temperature SOFCs fueled by ammonia.