Analysis of gadolinium-doped ceria-ternary carbonate composite electrolytes for solid oxide fuel cells

Doped ceria-carbonate electrolytes have high ionic conductivity and shows good solid oxide fuel cell (SOFC) performance at low temperature (400–600 °C). Various compositions of unary, binary, and ternary gadolinium-doped ceria-carbonate electrolytes are prepared using (Na, Li, K, Sr)-CO3 and GDC. The electrolytes are physically and electrochemically characterized using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and two-probe AC-conductivity methods. In the unary gadolinium-doped ceria-carbonate composite electrolytes, best ionic conductivity is shown by 25 wt% Li2CO3-GDC electrolyte (0.077 S cm−1 at 600 °C). The ternary carbonate composite mixture of 25 wt% (LiNaK)2CO3-GDC exhibits higher ionic conductivity (0.29 S cm−1 at 600 °C) than binary and unary carbonate electrolytes. The enhanced conductivity may be due to lower eutectic temperature of (LiNaK)2CO3 rendering larger (LiNaK)2CO3-GDC interface. At 600 °C, the peak power density for the cell of ternary carbonate, 25 wt% (LiNaK)2CO3-GDC electrolyte and binary carbonate, 25 wt% (LiNa)2CO3-GDC electrolyte is 224 mW cm−2 (at 555 mA cm−1) and 180 mW cm−2 (at 417 mA cm−1), which would enable them to be used as electrolytes for low-temperature SOFC.