Improvement of a single-chamber solid-oxide fuel cell and evaluation of new cell designs

The performance of a single-chamber solid-oxide fuel cell (SOFC) made from a YSZ solid electrolyte with a 25 wt% Ce0.8Gd0.2O1.9 (GDC)-containing Ni anode and a 15 wt% MnO2-containing La0.8Sr0.2MnO3 cathode was found to be significantly enhanced by the deposition of Mn, Ga, Cr, Ce, and Lu oxide layers on the YSZ surface. In particular, the deposition of the Mn oxide layer increased the maximum power density from 161 to 213 mW/cm2 in a mixture of methane and air having a CH4/O2 volume ratio of 1/1 at a flow rate of 300 mL/min, and at an operating temperature of 950 C. This effect was the result of the promoted anodic and cathodic reactions. Two types of cell designs were examined for the single-chamber SOFC; the two electrodes were deposited on opposite surfaces (A-type cell) and on the same face (B-type cell) of the solid electrolyte. The A-type cell showed increasing power density with decreasing electrolyte thickness. The maximum power density was 256 mW/cm2 at a solid electrolyte thickness of 0.3 mm. The B-type cell showed an increased power density for a decreased gap between the electrodes. The maximum power density was 143 mW/cm2 for a gap of 0.5 mm. The long-term stability of the SOFC was also studied and found to have a direct relationship with carbon deposition on the GDC-containing Ni electrode. 18 refs.