Low thermal-expansion and high proton uptake for protonic ceramic fuel cell cathode

Nowadays, the excessive thermal expansion behavior of Co-based electrode always leads to the cell degradation or delamination. Especially for BaCoO_3-δ-type perovskite oxides, as the result of the large ionic radius of Ba²⁺ (1.61 Å), the phase structures of these materials are not stable. Herein, we developed a novel single-phase electrode Ba₂Sc_0.1Nb_0.1Co_1.5Fe_0.3O_6-δ (BSNCF) with a stable cubic perovskite structure and suitable thermal expansion coefficient (TEC, 11.9 × 10⁻⁶ K⁻¹), which showed a great stability in symmetrical cell area specific resistances (ASRs) subjecting to the harsh thermal cycling procedure with 30 cycles between 300 °C and 600 °C (increased from 0.197 Ω cm² to 0.222 Ω cm²,13% increase). The high-temperature hard X-ray absorption spectroscopy measurement directly monitored a small change of Co valence in BSNCF as the temperatures rising. Also, BSNCF exhibits well proton uptake for its appropriate oxygen-site basicity and excellent surface reaction activity. The single cell based on BSNCF achieved an outstanding peak power density of 977 mW cm⁻² at 600 °C.