Revealing the Impact of Steam Concentration on the Activity and Stability of Double-Perovskite Air Electrodes for Proton-Conducting Electrolysis Cells

Great efforts have been devoted to developing high-performance air electrodes for proton-conducting electrolysis cells (PCECs). However, the stability of existing air electrodes still cannot meet the requirement for practical applications, and the degradation mechanisms require further investigation. Herein, taking porous PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF)–BaZr0.1Ce0.7Y0.1Yb0.1O3−δ (BZCYYb) composite air electrode as the model system, we systematically investigate the impact of steam concentration on the activity and stability of the electrode. The electrode exhibits reduced electrochemical impedance and improved Faradaic efficiency under high steam concentrations. Nevertheless, the hydrogen production performance of the cell degrades rapidly when operating under high steam concentrations (>30%). Such degradation of the cell is mainly attributed to the agglomeration and cation (especially Sr and Ba) segregation of PBSCF, and the decreased oxygen vacancies in BZCYYb caused highly concentrated steams. Our results clarify the critical role of steam on the activity and stability of the air electrode for PCECs. The findings can help guide the development of robust and active catalysts for other high-temperature electrochemical devices.