Influence of the coexisting gases on the electrochemical reaction rates between 873 and 1173 K in a CH4-H2O/Pt/YSZ system

The rates of electrochemical reactions were clarified in a CH4-H2O system at the interface of a porous Pt electrode/Y2O3-stabilized ZrO2 (YSZ) electrolyte between 873 and 1173 K to elucidate the kinetics of the anode reaction of solid oxide fuel cells (SOFCs). The dominant electrochemical reaction was found to be the redox process of H-2/H2O, where H-2, C, CO, and CO2 were formed without a current by the chemical reactions in a CH4-H2O system. The partial electrochemical reaction rates of H-2, CO, C, and CH4 were determined. The rate of the electrochemical reaction of CO/CO2 in a CH4-H2O system is larger than that in a CO-CO2 system under anodic polarization at 873 and 973 K. This means both the efficiency and the rate of the utilization of fuels on SOFCs are increased. (C) 2000 Elsevier Science B.V. All rights reserved.