Performance of yttria-stabilized zirconia fuel cell using H2-CO2 gas system and CO-O2 gas system

This paper reports the performance of an yttria-stabilized zirconia fuel cell (YSZ) using five kinds of gas systems. The final target of this research is to establish the combined fuel cell systems which can produce a H2 fuel and circulate CO2 gas in the production process of electric power. A large electric power was measured in the H2-O2 gas system and the CO-O2 gas system at 1073 K. The formation process of O2− ions in the endothermic cathodic reaction (1/2O2+2e−→O2−) controlled the cell performance in both the gas systems. The electric power of the H2-CO2 gas system, which allowed to change CO2 gas into a CO fuel (H2+CO2→H2O+CO) in the cathode, was 1/31-1/11 of the maximum electric power for the H2-O2 gas system. This result is related to the larger endothermic energy for the formation of O2− ions from CO2 molecules at the cathode (CO2+2e−→CO+O2−) than from O2 molecules. The CO-H2O gas system and the H2-H2O gas system was expected to produce a H2 fuel in the cathode (CO+H2O→H2+CO2, H2+H2O→H2+H2O). Although relatively high OCV values (open circuit voltage) were measured in these gas systems, no electric power was measured. At this moment, it was difficult to apply H2O vapor as an oxidant to the cathodic reaction in a YSZ fuel cell.