Achieving electrocatalytic activity toward oxygen reduction reaction based on Ruddlesden–Popper type cathode catalyst for solid oxide fuel cells

Ruddlesden‒Popper (R‒P) layered perovskite Sr₃Fe₂O_7−δ (SFO) is considered a promising cathode catalyst for solid oxide fuel cells (SOFCs) because of its unique layered structure. However, its insufficient oxygen reduction reaction (ORR) activity at reduced temperatures leads to high polarization resistance, significantly degrading cell performance. This study introduces Nd-doped Sr_2.9Nd_0.1Fe₂O_7−δ (SNFO) as a candidate cathode material, focusing on its phase structure, oxygen desorption behavior, catalytic activity, and oxygen reduction reaction kinetics. At 700 °C, the SNFO catalyst delivers outstanding ORR activity, with a polarization resistance of 0.20 Ω·cm² and a peak power density (PPD) of 803 mW·cm⁻². Distribution of relaxation times (DRT) analysis revealed that the ORR kinetics of the SNFO cathode are primarily limited by the oxygen adsorption‒dissociation process. In addition, density functional theory (DFT) calculations demonstrate that SNFO has a lower oxygen vacancy formation energy, an enhanced O₂ adsorption capacity, and optimized overall oxygen dissociation energetics. This study identifies SNFO as a promising cathode electrocatalyst for SOFCs.