Bifunctional Strontium-Iron Doped Neodymium Cobaltite: A Promising Electrocatalyst for Intermediate Temperature Solid Oxide Fuel Cells and CO2 Electrolyzer

A novel intermediate temperature solid oxide fuel cell cathode, Nd-0.Sr-67(0).Co-33(0).Fe-8(0).O-2(3-delta) (NSCF), synthesized via auto-combustion, exhibits exceptional mixed ionic-electronic conducting properties with a cubic perovskite structure. At 800 degrees C, NSCF demonstrates high electrical (1003 S cm(-1)) and ionic (1.676 x 10(-2) S cm(-1)) conductivities, with activation energies of 0.0335 and 0.481 eV, respectively. Electronic analysis confirms its metallic nature, while the calculated oxygen migration energy (0.455 eV) correlates with experimental ionic conduction activation energy. The negative bulk oxygen vacancy formation energy (-38.70 kcal mol(-1)) indicates efficient oxygen reduction reaction and CO2 electrolysis kinetics. Electrical conductivity relaxation shows non-debye behavior, with D-chem of 5 x 10(-4) cm(2) s(-1) and K-ex of 6.450 x 10(-4) cm (-1)s at 800 degrees C. NSCF exhibits low interfacial polarization resistance (0.05 Omega cm(2)) and area-specific resistance (0.025 Omega cm(2)), further reducing to 0.014 Omega cm(2) with an NSCF-GDC Gadolinium doped ceria interlayer. An anode-supported cell achieves peak power densities of 2.27, 1.52, and 0.86 W cm(-2) at 800, 750, and 700 degrees C, respectively. In SOEC mode, NSCF demonstrates excellent CO2 reduction capability of constant current density of -1.1 A cm(-2) with stable 55-h performance, which establishes its potential both as IT-SOFC cathode and CO2 electrolysis catalysts.