Facile Deficiency Engineering in a Cobalt‐Free Perovskite Air Electrode to Achieve Enhanced Performance for Protonic Ceramic Fuel Cells

Abstract As a crucial component responsible for the oxygen reduction reaction (ORR), cobalt‐rich perovskite‐type cathode materials have been extensively investigated in protonic ceramic fuel cell (PCFC). However, their widespread application at a commercial scale is considerably hindered by the high cost and inadequate stability. In response to these weaknesses, the study presents a novel cobalt‐free perovskite oxide, Ba 0.95 La 0.05 (Fe 0.8 Zn 0.2 ) 0.95 O 3‐δ (BLFZ0.95), with the triple‐conducting (H + |O 2− |e − ) property as an active and robust air electrode for PCFC. The B‐site deficiency state contributes significantly to the optimization of crystal and electronic structure, as well as the increase in oxygen vacancy concentration, thus in turn favoring the catalytic capacity. As a result, the as‐obtained BLFZ0.95 electrode demonstrates exceptional electrochemical performance at 700 °C, representing extremely low area‐specific resistance of 0.04 Ω cm 2 in humid air (3 vol.% H 2 O), extraordinarily high peak power density of 1114 mW cm −2 , and improved resistance against CO 2 poisoning. Furthermore, the outstanding long‐term durability is achieved without visible deterioration in both symmetrical and single cell modes. This study presents a simple but crucial case for rational design of cobalt‐free perovskite cathode materials with appreciable performance via B‐site deficiency regulation.