Impregnation of microporous SDC scaffold as stable Solid Oxide Cell BSCF-based air electrode.

Abstract

Barium strontium cobaltite-ferrite (Ba1-xSrxCoyFe1-yO3-δ, BSCF) is a widely studied mixed ionic-electronic conductor material for air electrode in solid oxide cells (SOC). Despite having excellent features, due to fast oxygen surface exchange and oxygen bulk diffusion, it lacks long-term stability. Electrode/electrolyte thermal expansion coefficient (TEC) mismatch and structural instability at temperature lower than 900 °C are responsible for the increase of electrode polarization which becomes a crucial issue for the long-term stability. In this work, SOC stability was studied by adding a thin porous samarium-doped ceria (SDC) backbone on top of the dense SDC electrolyte. The porous SDC backbone was then infiltrated by precursor nitrates to obtain a Ba0.5Sr0.5Co0.8Fe3-δ composition. The SEM investigation showed a nano-sized BSCF-based layer covering the backbone structure. In addition, symmetrical cells were studied in the 400-700 °C temperature range under anodic and cathodic polarization showing unexpected behavior associated to the electrode microstructure. The modified electrode synergistically enhanced ORR and OER by showing no oxygen vacancies clustering which induces a higher polarization resistance. Ageing procedure was performed for over 120 hours at 600 °C under switched current load of ± 0.2 A·cm-2. The prepared system showed high stability coupled with remarkable electrocatalytic performance and good mechanical properties.