Development of a novel type of composite cathode material for proton-conducting solid oxide fuel cells

A high-performance solid oxide fuel cell La_1−xSr_xMnO₃ (LSM) cathode/metallic interconnect contact material Ni_1−xCo_xO, added with the mixed ionic-electronic conducting Sm_0.2Ce_0.8O_2−δ (SDC), was proposed as a novel composite cathode for proton-conducting solid oxide fuel cells (H-SOFCs) with BaZr_0.1Ce_0.7Y_0.1Yb_0.1O_3−δ (BZCYYb) as the electrolyte. The X-ray diffraction (XRD) results indicated that the maximum doped ratio of Ni_1−xCo_xO was Ni_0.7Co_0.3O (NC3O), also shown that NC3O was chemically compatible with SDC at temperatures up to 1400 °C. The TEC of NC3O was also measured to check its thermal compatibility with other components. Laboratory-sized tri-layer cells of NiO–BZCYYb/BZCYYb/NC3O-SDC were fabricated and tested with humidified hydrogen (∼3% H₂O) as fuel and static air as oxidant, respectively. A maximum power density of 204 mW cm⁻² and a low interfacial polarization resistance Rp of 0.683 Ω cm² were achieved at 700 °C. The results have indicated that the NC3O-SDC composite is a simple, stable and cost-effective cathode material for H-SOFCs.