This paper presents Pervoskite-type BaCo0.7Ta0.1Fe0.2O3−δ (BCTF) cathode for intermediate temperature proton conducting solid oxide fuel cells (SOFCs). BCTF with cubic phase shows excellent structural stability and adequate chemical stability against CO2/H2O in contrast to BaCo0.8Fe0.2O3−δ. Conductivity of BCTF reaches above 10 S cm−1 in air at intermediate temperatures. Composite cathode polarization resistance (BCTF/BaZr0.1Ce0.7Y0.2O3−δ) in a symmetric cell based on proton conducting BaZr0.1Ce0.7Y0.2O3−δ (BCZY) electrolyte was as low as 0.1 Ω cm2 at 700 °C. The maximum output of anode-supported thin-film SOFC with BCTF/BCZY composite cathode and BCZY electrolyte reaches 255 mW cm−2 when employing humidified H2 as fuel and static air as oxidizer.

A novel BaCe0.4Zr0.3 Sn0.1Y0.2O3−δ (BSY) electrolyte membrane with thickness of 20 μm was fabricated on NiO-based anode substrate via a one-step all-solid-state method followed by a co-sintering at 1450 °C for 5 h. Chemical stability test demonstrated that BSY electrolyte showed adequate chemical stability against CO2 and H2O at intermediate temperature. Besides, the doping of Sn also enhanced the conductivity in humidified hydrogen. With Nd0.7Sr0.3MnO3−σ cathode and hydrogen fuel, the fuel cell generated maximum output of 320, 185 and 105 mW cm−2 at 700, 650 and 600 °C, respectively. The interfacial resistance of the fuel cell was studied under open circuit conditions and the short-term cell performance also confirmed the stability of BSY electrolyte membrane.

BaCe0.9−xYxSn0.1O3−σ (x = 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3) and BaCe0.8Y0.2O3−δ powders were synthesized by a solid-state reaction method. XRD analysis revealed that the BaCe0.8Y0.2O3−δ powders obviously decomposed into CeO2 and BaCO3 after exposure in 5% H2O + 5% CO2 + 90% N2 at 500 °C for 10 h. However, samples containing Sn remains unchanged in the same conditions, demonstrating a better stability in the presence of CO2 and H2O. The conductivity of BaCe0.9−xYxSn0.1O3−δ increased with the increase of Y content (x ≤ 0.20), and the highest value was observed at x = 0.20 while the conductivity significantly decreases with x = 0.30 and 0.35. And the BaCe0.7Sn0.1Y0.2O3−σ displays 0.01 S/cm at 700 °C in humidified hydrogen. Thin BaCe0.7Sn0.1Y0.2O3−σ electrolyte membranes were prepared through suspension spray combined with in situ sintering at 1400 °C. With Nd0.7Sr0.3MnO3−σ as cathode, solid oxide fuel cells were assembled and tested with humid hydrogen as fuel and static air as oxidant. The OCV, peak output and interfacial resistance were 1.04 V, 220 mW/cm2 and 0.95 Ω cm2 at 700 °C, respectively.

BaCe0.7Ti0.1Y0.2O3−δ (BCTY) and BaCe0.8Y0.2O3−δ (BCY) were synthesized by solid-state reaction method at 1300 °C for 24 h. It was found that BCY powders decomposed into BaCO3 and CeO2 after exposure in 94% N2 + 3% CO2 + 3% H2O at 700 °C for 10 h, indicating the instability of BCY in the presence of CO2 and H2O. On the contrary, BCTY powders remained unchanged under the same conditions, showing the improved chemical stability against CO2 and H2O. Thermal expansion test revealed that BCTY and BCY showed similar thermal expansion behavior from room temperature to 1000 °C. The conductivity of BCTY could reach as high as 0.0062 S/cm at 700 °C in humid hydrogen, close to 0.0083 S/cm for BCY. A solid oxide fuel cell (SOFC) with 20-μm thick BCTY electrolyte membrane was prepared with suspension spray and subsequently tested with Nd0.7Sr0.3MnO3−δ as cathode. The maximum output and open circuit voltage exhibited 295 mW/cm2 and 0.95 V with hydrogen as fuel at 700 °C, respectively.