Compatibility of proton conducting La6WO12 electrolyte with standard cathode materials

Mixed ionic and electronic conductors (MIEC) such as LSM (La0.7Sr0.3MnO3 − δ), LSCM (La0.75Sr0.25Cr0.5Mn0.5O3 − δ) and BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3 − δ) have been investigated as potential cathode materials with La6WO12 (LWO) proton conducting electrolyte for use in protonic ceramic fuel cells (PCFC). Different cathode — LWO powder mixtures have been subjected to high temperature treatment (1150 °C during 144 h in air) and studied by X-ray powder diffraction (XRPD) and scanning electron microscopy (SEM). The analysis of the results reveals that LWO is chemically and mechanically stable with LSM and LSCM but reacts with BSCF. Symmetrical cells cathode/LWO/cathode have been studied by electrochemical impedance spectroscopy (EIS). The minimum of area specific resistance (ASR) values have been found for LSM cathode (in humidified air at 750 °C: ASRLSM = 4.3 Ω·cm2; ASRLSCM = 15.5 Ω·cm2; ASRBSCF = 9.7 Ω·cm2). Composite cathodes using a two-phase ceramic/ceramic (cer–cer) approach were also studied. In the case of LSM/LWO cathode cer–cer, it allows a significant decrease of the ASR value.