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

A high-performance solid oxide fuel cell La1−xSrxMnO3 (LSM) cathode/metallic interconnect contact material Ni1−xCoxO, added with the mixed ionic-electronic conducting Sm0.2Ce0.8O2−δ (SDC), was proposed as a novel composite cathode for proton-conducting solid oxide fuel cells (H-SOFCs) with BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb) as the electrolyte. The X-ray diffraction (XRD) results indicated that the maximum doped ratio of Ni1−xCoxO was Ni0.7Co0.3O (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.