Direct electrochemical power generation from carbon in fuel cells with molten hydroxide electrolyte

Historically, despite its compelling cost and performance advantages, the use of a molten metal hydroxide electrolyte has been ignored by direct carbon fuel cell (DCFC) researchers, primarily due to the potential for formation of carbonate salt in the cell. This article describes the electrochemistry of a patented medium-temperature DCFC based on a molten hydroxide electrolyte, which overcomes the historical carbonate formation. An important technique discovered for significantly reducing carbonate formation in the DCFC is to ensure a high water content of the electrolyte. To date, four successive generations of DCFC prototypes have been built and tested to demonstrate the technology - all using graphite rods as their fuel source. These cells all used a simple design in which the cell containers served as the air cathodes and successfully demonstrated the ability to deliver more than 40 A with the current density exceeding 250 mA/cm(2). Conversion efficiency greater than 60% was achieved.