The Reverse Boudouard Reaction in Direct Carbon Fuel Cells

Abstract

The Direct Carbon Fuel Cell (DCFC) has generated renewed attention recently, because of its potentially very high conversion efficiency. However, the performance of DCFC appears to be appreciably limited by the reverse Boudouard reaction, also termed "carbon corrosion" reaction. This paper aims to understand this limitation, by investigating the mechanism of carbon corrosion in molten carbonate. The open-circuit potential behavior of carbon in molten carbonate is measured. Analysis of its time-dependence suggests that in molten carbonate medium the reverse Boudouard reaction occurs as a result of two compensating electrochemical reactions. In addition, the wettability of the carbon electrode in molten carbonate plays an important role in the potential behavior. Direct observation confirms that the wetting phenomena are driven not only by capillary forces but also by the reverse Boudouard reaction. Finally, it is concluded that the anodic reaction of DCFC appears to be composed of multiple electrochemical reactions.