Theoretical electromotive force and performance of SOFC fed with different fuel gases

The equilibrium species and theoretical electromotive force of cells fed with NH3 and 3% H2O humidified H2, CH4, C3H8 and underground coal gasification (UCG) gas on the basis of minimum Gibbs free energy were calculated, whilst the open circuit voltage (OCV), V-I characteristics and long-term stability of NiO-GDC||GDC||Ba0.9Co0.7Fe0.2 Nb0.1O3-δ (B0.9CFN) anode-supported cells operated in above five fuels were evaluated. The results showed that direct utilization of hydrocarbon fuels in anode could achieve a desirable electromotive force (EMF) no less than 1.05 V, while the OCV for ceria-based cells was comparatively poorer due to the presence of electronic conductivity. Besides, the synergy effect between stagnant kinetics of hydrocarbons reforming and the relatively sufficient O2- supply due to fast migration of oxide ions suppressed carbon deposition at low operating temperatures for ceria-based SOFC. Furthermore, the UCG gas fed cell exhibited peak power densities as high as 0.151, 0.299, 0.537 and 0.729 W·cm-2, respectively at 500, 550, 600 and 650°C, and showed no evident performance decay and carbon deposition on anode after discharging at 600°C under a constant voltage of 0.6 V for 120 h, thereby demonstrating UCG gas is a promising fuel for direct utilization in SOFC. © All Rights Reserved.