By adding 0.5 mol% Li2O, YSZ was densified at 1250 °C, and also had a high conductivity of 0.0313 S cm−1 at 800 °C.

This paper investigates the equilibrium species and theoretical electromotive forces (EMF) of cell fed with 3% H 2 O humidified simulated underground coal gasification (UCG) gas, and the performance of anode-supported NiO-Gd 0.1 Ce 0.9 O 2-δ (GDC)||GDC||Ba 0.9 Co 0.7 Fe 0.2 Nb 0.1 O 3-δ (B 0.9 CFN) cell operated on the UCG gas. Results show that EMF values are always above 1.05 V, and the UCG gas fed cell exhibits maximum power densities of 0.151, 0.299, 0.537 and 0.729 W·cm -2 at 500, 550, 600 and 650 o C, respectively, slightly inferior to that of hydrogen fed cell of 0.330, 0.544, 0.765 and 0.936 W·cm -2 , respectively, as a result of sluggish reaction kinetics of UCG gas at the anode. However, the synergy between slow anode reaction kinetics and sufficient and fast migration of oxygen ions to the anode attributing to the using of GDC electrolyte and B 0.9 CFN cathode suppresses carbon deposition at intermediate temperatures. Only slight current density decrease ranged from 0.2959 to 0.2790 A·cm -2 is observed during the 480 h of durability testing under constant 0.7 V output voltage at 600 o C for the UCG gas fed cell. And subsequent * Corresponding author. Tel.2 SEM inspection of the tested cell indicates no measurable carbon deposition on the anode surface, thereby demonstrating that UCG gas is a promising fuel for utilization in SOFCs.