Catalytic gasification of carbon in a direct carbon fuel cell

Abstract

The present study investigates the catalytic properties of metallic species commonly present in brown coal (Ca, Fe, and Mg), towards Boudouard (CO₂) gasification, by individually doping pure carbon black with these species, and examining their electrochemical performance in a direct carbon fuel cell (DCFC). Thermogravimetric analysis was used to study the effect of added catalysts on carbon oxidation at 850 °C and compared to those of chars produced from a Victorian brown coal. The relative catalytic activities of dopants were found to increase from Mg < Fe < Ca, in the presence of CO₂. The carbon black fuels doped with the catalytic species, when tested in a direct carbon fuel cell, were also found to influence the fuel cell performance under both N₂ and N₂/CO₂ anode purge gases in line with relative catalytic activities of dopants. Electrochemical impedance spectroscopy measurements, under open circuit conditions, were used to assess the nature of performance variations in fuel cell environments. Availability of gaseous CO via in-situ Boudouard gasification of the fuel is believed to be the primary differentiating factor for various carbon fuels in cell operation. Finally, it was established that the catalytic dopants added to the carbon fuel had an effect on the equilibrium oxygen partial pressure in the C/CO/CO₂ system and hence the open circuit voltage.