Effect of fuel composition on the performance of ceramic-based solid oxide fuel cell anodes

Solid oxide fuel cell (SOFC) anodes based on electronically conducting ceramics have potential advantages over conventional Ni-YSZ anodes, including better fuel flexibility, stability under redox cycling, and sulfur tolerance. Here we report on anodes based on La_0.8Sr_0.2Cr _0.98V_0.02O₃ that also contained Ce _0.9Gd_0.1O_1.95 (GDC) and a small amount (5 wt.%) of NiO, and describe results for these electrodes in SOFCs with GDC electrolytes. Microstructural evaluation showed the desired porous microstructure. Metallic Ni, if present in the anodes after reduction, was below the X-ray diffraction detection limit; the Ni may instead have dissolved in the perovskite phase. Cell performance with hydrogen was evaluated using current-voltage measurements and electrochemical impedance spectroscopy - anode polarization resistance values were generally larger than typically reported for Ni-YSZ anodes under comparable test conditions. The SOFCs were found to operate well with slightly humidified hydrocarbon fuels including methane, ethane, propane, and butane, but showed slight degradation over several hours apparently due to coking. However, initial cell performance was recovered by switching to H₂ fuel or by exposing the anodes to air. Cell performance was stable during several hydrogen-air and propane-air reduction-oxidation cycles.