A bifunctional cathode enabling efficient decomposition and utilization of nitrous oxide in protonic ceramic fuel cells for power generation

Protonic ceramic fuel cells (PCFCs) have been recognized as promising power generation devices for future clean energy systems, owing to their relatively low activation energy for proton migration and high energy conversion efficiency. In certain application scenarios, the use of N2O (a potent greenhouse gas), as an alternative oxidant to air, presents a feasible strategy. Herein, we report for the first time the operation of PCFCs employing N2O as the oxidant. A hybrid Pr2Ni0.6Co0.4O4-δ (PNCO-214) catalyst is developed, comprising Ruddlesden-Popper (R-P) structured Pr4Ni1.8Co1.2O10-δ (PNCO-4310) and Fluorite structured Pr6O11 (PO-611), which synergistically exhibits exceptional catalytic activity toward both N2O decomposition and the oxygen reduction reaction, achieving over 92% conversion and area specific resistance of 1.301 Ω·cm² at 600 °C. Quasi-in-situ temperature-dependent FTIR and electrochemical impedance spectroscopy analyses reveal that abundant oxygen vacancies in PNCO-214 facilitate rapid adsorption and dissociation of N2O into N2 and O2, while also promoting the surface exchange kinetics of proton/oxygen during ORR. When applied in an anode-supported single cell with PNCO-214 cathode operating under N2O, outstanding power density and low resistance are achieved, delivering 0.801 W·cm-2 and 0.245 Ω·cm2 at 600 °C. Satisfactory performance is also maintained even when the temperature is reduced to 500 °C. Furthermore, the single cell demonstrates relatively good stability with negligible degradation over 130 hours at 600 °C and 0.7 V. These findings underscore the potential of PNCO-214 as a highly effective cathode catalyst for enabling the use of N2O as a viable oxidant in PCFCs for specific industrial applications.