A high performance composite ionic conducting electrolyte for intermediate temperature fuel cell and evidence for ternary ionic conduction

The performance of a composite electrolyte composed of a samarium doped ceria (SDC) and a ternary eutectic carbonate melt phase was examined. The formation temperature of a continuous carbonate melt phase is crucial to the high conductivity of this material. The electrolyte contains 30 and 50 wt% carbonate exhibited a sharp increase of conductivity at a temperature close to the melting point of the eutectic carbonate, ca 400 °C, which is more than 100 °C lower than those electrolytes using binary carbonate. At around 650 °C, and with CO2/O2 used as the cathode gas, the fuel cell gave a power output 720 mW cm−2 at a current density 1300 mA cm−2. Water was measured in both the anode and cathode outlet gases and CO2 was detected in the anode outlet gas. When discharged at 800 mA cm−2, a stable discharge plateau was obtained. The CO2 in the cathode gas enhances the power output and the stability of the single cell. Based on these experimental facts, a ternary ionic conducting scheme is proposed and discussed.