Performance comparison of composite cathode: Mixed ionic and electronic conductor and triple ionic and electronic conductor with BaZr0.1Ce0.7Y0.1Yb0.1O3-δ for highly efficient protonic ceramic fuel cells

Rapid oxygen (O2-) electroreduction rate and high electrochemical activity towards proton (H+) and electron (e(-)) are required properties of cathode for highly efficient protonic ceramic fuel cells (PCFCs). Herein, we investigate the effect of composite cathodes on electrochemical performance under PCFC operating conditions. To introduce protonic properties in cathodes, the proton-conducting oxide (PCO), BaZr0.1Ce0.7Y0.1Yb0.1O3-delta (BZCYYb) is blended with (i) Sm0.5Sr0.5CoO3-delta (SSC) as a mixed ionic and electronic conductor (MIEC) and (ii) PrBa0.5Sr0.5Co1.5Fe0.5O5+delta (PBSCF) as a triple ionic and electronic conductor (TIEC). Interestingly, the peak power density (PPD) ratio of SSC-BZCYYb/SSC shows over 200% enhancement, whereas the PPD ratio of PBSCF-BZCYYb/PBSCF is attained only 95.3% at 500 ?. Such a difference can be attributed to the extended H2O (gas) formation site of SSC-BZCYYb, which reduces the non-charge transfer resistance (R-3) of SSC-BZCYYb as measured by impedance spectra and fitting analysis. On the other hand, the composite effect of PBSCF-BZCYYb is relatively insignificant because of the sufficient proton uptake properties of PBSCF. In sum, the composite strategy is a more effective way to improve the performance of MIEC cathode than TIEC cathode at typical PCFC operating temperatures.