Investigation of ceria-molten carbonate electrolyte, composite anode and its catalytical effect on various carbon fuels in molten carbonate direct coal/carbon fuel cell

Abstract

In order to improve the power density of molten carbonate direct coal/carbon fuel cell (MC-DCFC), a composite electrolyte of ceria-carbonate and ceria-coal/carbon anode are used. Electrochemical impedance spectroscopy (EIS) results reveal that ohmic resistance decreases 15–56.5 % in ceria-molten carbonate electrolyte. The surface morphology exhibit core–shell structures, which increase CO32− ionic transportation between the electrolyte surface and ceria-core particle. Among the all-carbon fuels, bituminous coal and graphite powders obtain a peak power density of 160 and 186 mW/cm2 with a maximum current density of 850 and 924 mA/cm2, respectively, at 700 ℃. In contrast, the catalytical effect of CeO2 (50 wt%) is analyzed on four different carbon fuels at 600 ℃. Incorporating ceria in graphite fuel lowers the apparent activation energy and enhances the reactivity. The EIS analysis displays the low charge transfer resistance in ceria-carbon fuel due to the indirect electrochemical redox. Ceria-graphite (≥100 µm) electrode achieves the highest power density of 203 mW/cm2 with a maximum current density of 1009 mA/cm2 for MC-DCFC at 600 ℃. In Ceria-graphite anode indirect redox pathway works together with direct electrochemical oxidation contributing to the high-power density, resulting in the maximum power density increase by 19.1 % compared to the carbonate electrolyte.