La_0.8Sr_0.2Co_1-xNi_xO_3-δ as the Efficient Triple Conductor Air Electrode for Protonic Ceramic Cells

Highly efficient mixed H+/e–/O2– triple conducting air electrodes are indispensable for improving the electrochemical performance of protonic ceramic fuel cells and electrolysis cells (PCFC/ECs) operating at intermediate temperatures. This study demonstrates that single perovskite-type La0.8Sr0.2Co1-xNixO3-δ families (LSCN, x = 0–0.3) are efficient H+/e–/O2– triple conductors due to a pronounced hydration ability at elevated temperatures with a related enthalpy of −107 kJ mol–1. Thermogravimetry confirmed that the oxides were capable of a 0.01 mole fraction proton uptake at 600 °C and pH2O of 0.023 atm. Reversible protonic ceramic cells were fabricated using these oxides as an air electrode and exhibited promising performance with a peak power density of 0.88 W cm–2 in fuel cell mode and an electrolysis current of 1.09 A cm–2 at a thermal neutral voltage in electrolysis cell mode at 600 °C. Impedance analysis confirmed that the polarization resistance of the La0.8Sr0.2Co0.7Ni0.3O3-δ cell was 0.09 Ω cm2 under an open circuit potential at 600 °C, which is much smaller than the polarization resistances reported for cells with a single or double perovskite-type triple conductor. The current results indicate that mixed H+/e–/O2– triple phase conducting LSCN oxides are promising air electrodes for protonic ceramic cells operating in the intermediate temperature region at approximately 600 °C.