Comparison Between Anode-Supported and Electrolyte-Supported Ni-CGO-LSCF Micro-tubular Solid Oxide Fuel Cells

Two types of micro-tubular hollow fiber SOFCs (MT-HF-SOFCs) were prepared using phase inversion and sintering; electrolyte-supported, based on highly asymmetric Ce0.9Gd0.1O1.95(CGO) HFs and anode-supported based on co-extruded NiO-CGO(CGO)/CGO HFs. Electroless plating was used to deposit Ni onto the inner surfaces of the electrolyte-supported MT-HF-SOFCs to form Ni-CGO anodes. LSCF-CGO cathodes were deposited on the outer surface of both these MT-HF-SOFCs before their electrochemical performances were compared at similar operating conditions. The performance of the anode-supported MT-HF-SOFCs which delivered ca. 480 mW cm–2 at 600 °C was superior to the electrolyte-supported MT-HF-SOFCs which delivered ca. six times lower power. The contribution of ohmic and electrode polarization losses of both FCs was investigated using electrochemical impedance spectroscopy. The electrolyte-supported MT-HF-SOFCs had significantly higher ohmic and electrode polarization ASR values; this has been attributed to the thicker electrolyte and the difficulties associated with forming quality anodes inside the small (<1 mm) lumen of the electrolyte tubes. Further development on co-extruded anode-supported MT-HF-SOFCs led to the fabrication of a thinner electrolyte layer and improved electrode microstructures which delivered a world leading 2,400 mW cm–2. The newly made cell was investigated at different H2 flow rates and the effect of fuel utilization on current densities was analyzed.