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 an yttria stabilized zirconia 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, CI; Ce, and Lu oxide layers on the YSZ surface. Ln particular, the deposition of the Mn oxide layer increased the maximum power density from 161 to 213 mW cm(-2) in a mixture of methane and air having a volume ratio of methane to oxygen of 1/1 at a flow rate of 300 mt min(-1) (methane 52 Int min(-1), oxygen 52 mL min(-1), nitrogen 196 mt min(-1)), and at an operating temperature of 950 degrees 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 an increasing power density with decreasing thickness of the solid electrolyte. The maximum power density was 256 mW cm(-2) at a solid electrolyte thickness of 0.3 mn. The B-type cell showed an increased power density for a decreased gap between the two electrodes. The maxi mum power density was 143 mW cm(-2) for a gap of 0.5 mm between the two electrodes. In addition, the long-term stability of the single-chamber SOFC was also studied and found to have a direct relationship with the carbon deposition on the GDC-containing Ni electrode. (C) 2000 The Electrochemical Society. S0013-4651(99)10-044-2. All rights reserved.