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

Abstract

A novel intermediate temperature solid oxide fuel cell cathode, Nd₀.₆₇Sr₀.₃₃Co₀.₈Fe₀.₂O₃_-δ (NSCF), synthesized via auto-combustion, exhibits exceptional mixed ionic-electronic conducting properties with a cubic perovskite structure. At 800 °C, NSCF demonstrates high electrical (1003 S cm⁻¹) and ionic (1.676 × 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 × 10⁻⁴ cm² s⁻¹ and K_ex of 6.450 × 10⁻⁴ cm ⁻¹s at 800 °C. NSCF exhibits low interfacial polarization resistance (0.05 Ω cm²) and area-specific resistance (0.025 Ω cm²), further reducing to 0.014 Ω cm² 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 °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.