Abstract
A-site dopant concentration driven oxygen non-stoichiometry in (Ba/La)1-xSrxCoyFe1-yO3-δ based mixed ionic and electronically conducting (MIEC) air electrodes having 0.2≤x≤0.6 and y = 0.8 was investigated through phase stability study vis-à-vis oxygen non-stoichiometry concentration (δ) determination and corelated with the vacancy mediated charge compensation mechanism in terms of oxygen reduction (ORR)/oxygen evolution (OER) reactions. The optimization for both BSCF and LSCF systems are found to be at La/Ba: Sr as 1.5:1. Optimized BSCF and LSCF-6482 based heterostructure (LS@BS) having hetero-interface was synthesized by adopting heterogeneous-heteromolecular nucleation and growth of LS on the seed of BS. While comparatively lower interfacial polarization of ∼0.0108 Ω cm2 is obtained for LS@BS heterostructure, the same for BSCF-6482 and LSCF-6482 are found to be 0.23 Ω cm2 and 0.02 Ω cm2 at 800 °C on GDC-based symmetrical cells. The time dependent losses in current under constant anodic (+0.8V) and cathodic potential (−0.8V) for 200h @800 °C for LS@BS and LSCF-6482are found to be ∼0.015 mA h−1 and ∼0.03 mA h−1 respectively and clinically corelated with the cell microstructure. Fuel-electrode supported cell with LS@BS air electrode exhibits a maximum current density of 2.4A.cm−2 @0.5V in FC and 0.48 A cm−2@1.5V, 60%RH (H2 flux 0.2Nlh−1.cm−2) having increasing trend with percentage RH in EC mode.
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