Anode modeling of a molten-carbonate based direct carbon fuel cell

The Direct Carbon Fuel Cell (DCFC) is a type of fuel cell using solid carbon as fuel and molten carbonate as electrolyte. Although the primary anodic reaction is believed to be a 4-electron carbon oxidation reaction, to explain the performance of the DCFC in practice it is necessary to consider the 2-electron CO oxidation reaction as well as the reverse Boudouard reaction. Taking these multiple reactions into account, this work develops a 1-D macrohomogeneous model, and investigates the current and concentration distribution in the DCFC anode. The result shows that the active zone is mostly located on the portion of the anode bed nearest the electrolyte matrix. The dimensionless analysis of the electrode's resistance ratios suggests that the DCFC anode performance is mainly limited by ohmic losses and the relatively slow kinetics of the anodic reactions. To improve the performance of the DCFC, increasing effective electrical conductivity of the carbon particle bed by an order of magnitude, for example by a small fraction of inert metallic additives, can increase the cell efficiency appreciably. Besides causing the anode bed to be fully used, the rise in effective electrical conductivity of the anode bed appreciably improves the power density of DCFC.