Advanced symmetric solid oxide fuel cell with an infiltrated K ₂NiF₄-Type La₂NiO₄ electrode

Advanced symmetric solid oxide fuel cells (SOFCs) with a reducible electrode were proposed. Specifically, La₂NiO₄ + La _0.9Sr_0.1Ga_0.8Mg_0.2O _3-δ (LSGM) [or Sm_0.2Ce_0.8O_1.9 (SDC)] composite electrodes were successfully fabricated by an infiltration method and tested for power generation. X-ray diffraction (XRD) results demonstrated there was no noticeable phase reaction between infiltrated La ₂NiO₄ and LSGM (or SDC) scaffold, and scanning electron microscopy (SEM) analysis indicated that the La₂NiO₄ phase formed as nanoparticles that decorated the surface of the scaffold. Different from conventional symmetric SOFCs, the electrode material La₂NiO ₄ of current cells was reduced under an anode atmosphere to form metallic nickel as a high active catalyst for fuel oxidation. After the reduction, the electrode morphology and geometric integrity were maintained for the infiltrated electrode. For thick electrolyte-supported symmetric SOFCs with infiltrated La₂NiO₄ electrodes, an attractive maximum power density of ∼550 mW cm^-2 was achieved at 800 C operating on hydrogen fuel, significantly higher than similar cells with stable perovskite oxide electrodes, as reported in the literature. It suggested that the unreduced and reduced La₂NiO₄ performed well as a cathode for the oxygen reduction reaction and as an anode for fuel electro-oxidation, respectively. In addition, a favorable operating stability was demonstrated for a symmetric SOFC with an infiltrated La₂NiO₄ electrode. It provides a new way for developing cost-effective SOFCs with huge application opportunities.