Characterization and polarization DRT analysis of a stable and highly active proton-conducting cathode

Abstract The development of high active cathode materials owning low activation energy (Ea) is the most critical core for protonic solid oxide fuel cells (P-SOFCs). Considering this challenge, we herein develop Ba0.9La0.1Co0.4Fe0.4Zr0.1Y0.1O3-δ-BaZr0.1Ce0.7Y0.2O3-δ (BLCFZY-BZCY) composite as a new proton conducting cathode for P-SOFCs. Anode supported single cells with BLCFZY-BZCY cathode show remarkable performance and low electrode Ea of 83.41 kJ mol−1. High power densities of 752 and 206 mW cm−2 are achieved at 700 and 500 °C, respectively, while corresponding electrode interfacial polarization resistances (Rp) are 0.08 and 1.2 Ω cm2. Interestingly, the electrode polarization processes with a high resolution based on the impedance spectra data were further analyzed using the distribution function of relaxation time (DRT). Three same polarization peaks (P1, P2, P3) meaning three rate-limiting steps are existed in the DRT curves with different temperature, where P3 resulting from the cathode-electrolyte interfacial resistance with oxygen species involved reactions is the dominant rate-limiting step with a proportion of over 49.6% while the anode-electrolyte interfacial resistance corresponding to P1 has almost no increase, from 0.03 Ωcm2 to 0.09 Ωcm2. The experimental results demonstrate BLCFZY-BZCY composite can be a promising proton conducting cathode for P-SOFCs.