La_(0.8)Sr_(0.2)MnO_3-La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_3 Composite Cathodes for Anode Supported Solid Oxide Fuel Cells

摘要

Anode supported solid oxide fuel cells (SOFC) with tape cast NiO/YSZ anode substrates, thin film YSZ electrolytes, and La_(0.8)Sr_(0.2)MnO_3 (LSM) -La_(0.9)Sr_(0.1)Ga_(0.8)Mg_(0.2)O_3 (LSGM) composite cathodes were fabricated and tested at 800°C using humidified hydrogen as fuel and air as the oxidant. The composition and processing temperature of the LSGM/LSM composite cathodes were varied and the resulting effects on cell performance were studied. A minimum in the cathodic overpotential was found at a composition of 50 wt % LSGM and 50 wt % LSM and at a firing temperature of 1150°C, with the overpotential increasing at compositions and temperatures above and below 50 wt% and 1150°C, respectively. The optimized composite cathode exhibited a cathodic overpotential of 0.14 V at 3 A/cm~2 at 800°C. The anodic overpotentials and ohmic resistance were similar from cell to cell, while changes in the cathodic overpotential largely dictated the cell performance. The maximum power density for a cell containing the optimized cathode was 1.4 W/cm~2 at a current density of 2.6 A/cm~2 at 800°C.