The performance of a solid oxide fuel cell (SOFC) is strongly associated with the activity and durability of the cathode, where the oxygen reduction reaction occurs. In this study, we report our findings in the development of an Nb-doped PrBa_0.8Ca_0.2Co₂O_6−δ (PrBa_0.8Ca_0.2Co_2−xNb_xO_6−δ, x = 0, 0.025, 0.05, and 0.1, denoted as PBCCN_x) perovskite composite as the SOFC cathode. Analyses of X-ray diffraction (XRD) patterns and energy-dispersive transmission electron microscopy (TEM-EDS) images suggest that after being treated at 950 °C in air, PBCCN_0.05 mainly contains phases of Ca- and Nb-doped PrBaCo₂O_6−δ double perovskite, PrCoO₃ perovskite with Ca and Nb doping, and Ba₃Ca_1.18Nb_1.82O_9−δ. When evaluated as an SOFC cathode, the PBCCN_0.05 mixture has shown a low polarization resistance of 0.0074 Ω∙cm² at 800 °C in La_0.8Sr_0.2Ga_0.8Mg_0.2O₃ electrolyte symmetrical cells. Accordingly, anode-supported single cells with a configuration of Ni–Zr_0.84Y_0.16O_2−δ (YSZ)/YSZ/Gd_0.1Ce_0.9O_2−δ/PBCCN_0.05 display high electrochemical performance, with a peak power density of 1.81 W∙cm⁻² and a reasonable durability of 100 h at 800 °C. PBCCN_0.05 possesses a higher concentration of oxygen vacancies, a faster oxygen surface adsorption‒dissociation rate, and an increased mass ratio of PrCoO₃ perovskite with Ca and Nb doping compared to PrBa_0.8Ca_0.2Co₂O_6−δ without Nb doping.

Ammonia has been recognized as a promising fuel for solid oxide fuel cells (SOFCs) because of its relatively high hydrogen content and high energy density. However, the effective catalysis of ammonia on the surface of state-of-the-art anode greatly hinders the further development of direct ammonia SOFCs. In this study, we report our findings of surface activating and stabilizing of a Ni-based cermet anode for highly efficient and durable operation on ammonia fuel, achieved by a surface coating of CeO_2−δ nanoparticles (NPs). When incorporated into a Ni-yttria-stabilized zirconia (Ni-YSZ) anode-supported single cell, the coatings demonstrate an improved electrochemical reaction activity and stability, achieving a high peak power density of 0.941 W·cm⁻² at 700 °C, and a promising stability of ~ 60 h (degradation rate of 0.127% h⁻¹ at 0.5 A·cm⁻²), much better than those of cells with a bare anode (~ 0.673 W·cm⁻² and degradation rate of 0.294% h⁻¹ at 0.5 A·cm^-2). The catalytic NPs significantly enhance the reaction activity toward the decomposition of ammonia and oxidation of hydrogen, especially at low temperatures (< 700 °C), as confirmed by the detailed distribution of relaxation time (DRT) analyses of the impedance spectra of the cells on NH₃ fuel.