Anode reaction characteristics in a molten carbonate fuel cell (MCFC) have been investigated in terms of overpotential by varying the temperature for 100 cm(2) class single cells. The temperature range was from 823 to 973 K under atmospheric conditions. Anodic overpotential was measured with the methods of electrochemical impedance spectroscopy (EIS), inert gas step addition (ISA), and reactant gas addition (RA). The cells successfully showed anodic overpcitential at the very extreme temperatures of 823 and 973 K. The results of EIS and ISA revealed that anodic overpotential rose when the temperature increased. This is attributed to the fact that mass transfer resistance through the porous electrode, that is, pore diffusion resistance, was increased at higher temperature. When using the RA method, it was also found that enlarged mass-transfer resistance of the reaction species, H-2, CO2, and H2O, was responsible for the increase in overpotential at higher temperatures. 2016 Elsevier B.V. (C) All rights reserved.