Composite Oxygen Electrode Based on LSCF and BSCF for Steam Electrolysis in a Proton-Conducting Solid Oxide Electrolyzer

This paper investigates composite oxygen electrodes based on La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) and Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) for proton-conducting solid oxide electrolyzer using BaCe0.5Zr0.3Y0.16Zn0.04O3−δ (BCZYZ) proton conductor. The conductivities of LSCF and BSCF are studied versus temperature and oxygen partial pressure and correlated to the electrochemical properties of the composite oxygen electrodes in symmetric cells and solid oxide electrolyzers at 800°C, respectively. Steam electrolysis is performed in a proton-conducting solid oxide electrolyzer based on composite oxygen electrode LSCF-BCZYZ and BSCF-BCZYZ at 800°C, respectively. I-V and AC impedance spectroscopy tests demonstrate that the oxidation of oxygen electrode is the main process at low voltage; however, the steam electrolysis dominates the whole process at high voltages. The current efficiencies of steam electrolysis is enhanced by ∼20% when the gas fed into oxygen electrode changes from 3%H2O/Air to 3%H2O/Ar.