Fabrication and characterization of microtubular solid oxide cell supported with nanostructured mixed conducting perovskite fuel electrode

Abstract

Mixed ionic and electronic conducting (MIEC) perovskites demonstrate advantages over Ni-cermet as fuel electrode materials for solid oxide cells (SOCs). However, SOCs are primarily electrolyte-supported planar designs in literature when MIEC perovskite fuel electrodes are employed, which are relatively easy to fabricate but usually have high electrolyte ohmic resistance. Perovskite fuel electrode-supported designs are rarely studied particularly for microtubular SOCs. In this research, (La0.3Sr0.7)0.9Ti0.9Ni0.1O3-δ-Sm0.2Ce0.8O1.9 (LSTN-SDC) electrode-supported microtubular cell LSTN-SDC/YSZ/(La0.8Sr0.2)0.95MnO3-δ is fabricated and characterized. The LSTN-SDC microtubular substrate is prepared using an in-house built spinneret extrusion system in combination with modified phase inversion method, featuring radially well-aligned microchannels open at the inner surface. A thin YSZ electrolyte of ~15 μm and (La0.8Sr0.2)0.95MnO3-δ electrode of ~25 μm are then fabricated on the substrate, respectively. Upon reducing treatment, nickel is exsolved from LSTN grains and uniformly decorated onto grain surface as Ni nanoparticles, and therefore on inner surface of microchannels in the substrate. With CO/CO2 gas mixture as the fuel, the complicated electro-/chemical reactions are identified in the substrate electrode. The electrolysis process in combination with surface catalytic process of nanostructured electrode substrate leads to highly efficient CO production from CO2 with conversion efficiencies of well above 100%. The electrolysis also facilitates to regenerate surface catalytic functionality of nanostructured electrode substrate. The redox stability advantages of the cell are demonstrated in both alternative reduction (CO)/oxidation (air) atmospheric conditions and reversible operating mode.