Electrochemical Performance of 100cm2 Class Direct Carbon-Molten Carbonate Fuel Cell (DC-MCFC)

One of major difficulties in developing direct carbon fuel cells is the high anode polarization in the carbon oxidation, which ultimately leads to the large loss of overall performance in direct carbon fuel cells. The molten carbonates (having the high ionic conductivity and good stability under CO₂ environments) have been suggested to deal with this issue because they can facilitate the carbon oxidation by extending the electrochemical reaction sites from three phase boundary of anode to the bulk carbon surface. The molten carbonate fuel cell (MCFC) is the ideal choice for applying such molten carbonates into direct carbon fuel cells. Note that the molten carbonates such as Li₂CO₃ and K₂CO₃ are used in the electrolyte material in MCFC. However, the underlying mechanism in operating and developing MCFC-based direct carbon fuel cells is still unclear.

In this work, we present the effect of various operating parameters such as temperature, molten carbonate/carbon ratio and different Ni thin layers inserted between matrix (electrolyte support) and carbon green sheet on the electrochemical performance of 100cm² class direct carbon - molten carbonate fuel cell (DC-MCFC). In addition, we attempt to understand the oxidation behavior of carbon in wet carbon anode (the composite of carbon and molten carbonates) of DC-MCFC. We find that in DC-MCFC, CO is produced via two electron transfer reaction [C (s) + CO₃^-2 → CO₂ (g) + CO (g) + 2e^-] and is further oxidized with CO₃^-2[CO(g) + CO₃^-2 → 2CO₂ (g) + 2e^-] at CCV condition, indicating that CO is responsible for determining the DC-MCFC performance.