An investigation to enhance the performance of molten carbonate-direct coal/carbon fuel cells through improvements in anode layouts and the compositions of carbonate electrolyte

Abstract

Two anode configurations are systematically tested in composite electrolytes of molten carbonate with Cs2CO3 at various temperatures using different carbon fuels, including bituminous coal, bituminous coal char, carbon black, and graphite powder. The results of electrochemical impedance spectroscopy show that electrolytes composed of (Li-K)2CO3 62:38 doped with 20 wt% Cs2CO3 and utilizing graphite powder as a fuel exhibit reduced ohmic and charge transfer resistance. This can be attributed to the decreased surface tension, which enhances the gas solubility of the reactants within the electrolytic matrix. The analysis of particle size distribution through laser diffraction reveals that the graphite specimen has the smallest mean particle size, resulting in an enhanced rate of electrochemical oxidation. The ultimate and proximate analysis indicates that graphite powder has a lower moisture and ash ratio along with a significantly higher fixed carbon content compared to other carbon fuels. Therefore, the obtained V-j &P-j curves in Anode 1 illustrate that graphite powder yields the highest current density and power density of 903 mA/cm2 and 172 mW/cm2, respectively, at an operating temperature of 680 °C under the laboratory conditions. These values surpass those reported in the existing literature. In contrast, Anode 2 exhibits low performance, due to ash particles regime-controlled at the lower part of the chamber during the coal pyrolysis. Based on results, we suggest that graphite powder is the promising fuel candidate for MC-DCFC to achieve the higher performance.