Electrochemical Performance of Highly Oxygen‐Permeable Ba(Co,Fe,Y)O 3 ‐Based Cathodes in Protonic Ceramic Fuel Cells

ABSTRACT Protonic ceramic fuel cells (PCFCs) have high energy conversion efficiencies and can be employed as next‐generation fuel cells. However, novel cathode materials with high electrochemical performances at low operating temperatures are required to practically apply PCFCs. BaCo 0.4 Fe 0.4 Zr 0.1 Y 0.1 O 3– δ (BCFZrY) is a promising material for PCFC cathodes owing to its low electrode polarization resistance ( R p ). Herein, instead of Zr doping, BaCo 0.4 Fe 0.4 A 0.1 Y 0.1 O 3– δ (BCF A Y) compounds, where A represents Ti, Mg, or Zn, were evaluated as PCFC cathode materials. BCF A Y ( A : Ti, Mg, or Zn) compounds have a higher oxygen permeability than BCFZrY. The electrochemical properties and power generation performance of the PCFCs with BCF A Y cathodes were measured and compared with those of PCFCs with BCFZrY cathodes. The PCFC with a BCFMgY cathode exhibited the lowest R p , leading to the highest power density, that is, 0.80 W cm −2 at 600°C. In addition, for all PCFCs with BCFY‐based cathodes, the reciprocal area‐specific resistances of R p and oxygen permeability fluxes of the cathode materials had an approximately proportional relationship. Therefore, it was confirmed that PCFC cathodes with a high oxygen permeability had a low cathode polarization resistance, which significantly enhanced the power generation performance of PCFCs.