Analytical modeling of electrochemical mechanisms in CO2 and CO/CO2 producing Direct Carbon Fuel Cell

The Direct Carbon Fuel Cell (DCFC) is a special type of high temperature fuel cell that directly uses solid carbon particles as anode and fuel. As an electrical power generator of power plants, it has a higher achievable efficiency (80%) than the Molten Carbonate (MCFC) and the Solid Oxide (SOFC) fuel cells, and has less emission than conventional coal-combustion power plants. In this paper, we propose a comparative study based on an analytical model for polarizations calculation in DCFC producing CO2 and a mixture of (CO/CO2) and using a carbonate melt (62 Li2CO3/38 K2CO3 mol%) as electrolyte. The obtained results indicate that when the CO is taken into account in the anode side, the DCFC performance increases by 15% compared to only CO2 producing DCFC system at the same operating conditions (moves from 1350 W m−2 to 1550 W m−2). Simulations lead to understand the effect of the operating conditions (temperature, cathodic gas composition and inlet cathodic pressure) on the performance of the DCFC in order to solve all constraints preventing the development of this type of fuel cell. The comparison of the obtained results with data from literature illustrates a relatively good agreement with an absolute average deviation of about 4%.

► DCFC produces more CO than CO2 at temperatures above 973 K.
► Boudouard reaction is shown as the key chemical reaction affecting DCFC mechanisms.
► Analytical modeling of electrochemical is performed with Boudouard reaction.
► Carbon electro-oxidation to CO offers higher OCV (1.1 V).
► DCFC performance increases by 15% when CO/CO2 mixture is considered as anode gas.