A liquid tin anode solid oxide fuel cell is operated at 900°C with a variety of fuel feeds, including argon, hydrogen, coal and a coal-water slurry. Characterization of anode performance is carried out by open circuit potential monitoring, linear potential sweeps, and electrochemical impedance spectroscopy combined with equivalent circuit modeling. A cathode symmetric cell is analyzed and modeled to isolate impedance contributions resulting from ionic resistance, cathode mass transport, and cathode charge transfer; results are used to isolate anode mass transport and charge transfer impedances in the fuel cell. Open circuit potential measurements under hydrogen fuel indicate that the dominant anode reaction is electrochemical oxidation of H2, while oxidation of Sn to SnO2 becomes the principal anodic process when the cell is fed with argon, coal, or coal-water slurry. Some chemical reduction of SnO 2 to Sn by chemical reaction with coal is indicated by the cell potential.