Microtubular solid oxide fuel cells fabricated by gel-casting: the role of supporting microstructure on the mechanical properties

Different cell configurations of anode-supported microtubular solid oxide fuel cells (mT-SOFCs) using samaria-doped ceria (SDC) as the electrolyte were fabricated. Several cells were processed varying the porosity and wall thickness (outer diameter) of NiO-SDC tubular supports. Suitable aqueous slurry formulations of NiO-SDC for gel-casting were prepared using agarose, as a gelling agent, and sucrose, as a pore former. The subsequent NiO-SDC anode functional layer (AFL), the SDC electrolyte and the La0.6Sr0.4Co0.2Fe0.8O3-d-SDC cathode were deposited by spray-coating. Afterwards, the electrochemical performance of different single cells was tested under humidified hydrogen as the fuel and air as the oxidant. The mechanical strength of the supporting tubes at different processing stages (green, pre-/post-sintering, post-reduction, post-redox cycle conditions) were also determined to study the macro-mechanical failure behaviour of the cells. In addition, the mechanical strength of half-cells with different porosity, sintering temperature and wall thickness in the tubular supports was also determined. For this purpose, the modulus of rupture was measured by a three point bending test. This study shows that the electrochemical properties and mechanical strength are feasible for further development of anode-supported mT-SOFCs fabricated by gel-casting