Polarization modeling and performance optimization of a molten sodium hydroxide direct carbon fuel cell (MHDCFC)

An electrochemical model for a molten sodium hydroxide direct carbon fuel cell (MHDCFC) is developed based on electrochemical reaction dynamics, mass transfer, and electrode processes in the cell. Activated carbon and graphite are considered the main fuels, and static and dynamic parameters describing polarizations are taken into account for valuation and optimization of cell performance. Asymmetric reaction compartments are used in the MHDCFC, and the effect of the anodic compartment height on polarization is described first. The cell performance mainly depends on temperature (T), the pressures in the anodic (Pan) and cathodic compartments (Pcat), the anodic compartment height (H1), and the fuel type. Besides, cell performance is affected by ohmic polarization, anode activation polarization, cathode concentration polarization, and cathode activation polarization, in order of precedence. At Pan of 1.8 atm, Pcat of 1.7 atm, H1 of 0.06 m, and T of 773-973 K, the efficiencies (e) of the cells with activated carbon and graphite are higher than 50% at current densities of 0-500 A m−2 and 0-700 A m−2, respectively. The maximum power densities (e > 50%) are achieved for activated carbon and graphite and reach 367.6626 W m−2 and 498.9687 W m−2, respectively.