High thermal stability of three-dimensionally ordered nano-composite cathodes for solid oxide fuel cells

• Three-dimensionally ordered nano-composite cathode is prepared.
• The nano-meter scale cathode shows high thermal stability even after 1000 °C sintering.
• The polarization resistance of the cathode remains stable for 100 h at 650 °C.
• The impedance behavior was similar to that of mixed ionic-electronic conductor.

A non-close-packed (NCP) silica opal connected by cylindrical rods was prepared using a selective etching technique. Using sol-gel impregnation of the NCP silica opal template, La0.8Sr0.2MnO3/Zr0.84Y0.16O2 (LSM/YSZ) composite cathodes were fabricated for solid oxide fuel cells. The microstructure of the as-prepared cathode revealed three-dimensionally (3D) ordered hollow spheres connected by cylindrical tubes. Even after high-temperature sintering at 1000 °C, the 3D ordered nano-network remained stable. Electrochemical impedance spectroscopy was used to study the oxygen reduction reaction kinetics of the 3D ordered LSM/YSZ electrode. The impedance behavior was similar to that of a mixed ionic-electronic conductor, different from the behavior of traditional micro-scaled LSM/YSZ electrodes. The nanometer-scale particle size and continuous nano-network are the main reasons for this divergence in behavior.