Carbon–air fuel cell without a reforming process

Abstract

This paper describes a direct carbon–air fuel cell (DCFC) which uses a molten hydroxide electrolyte. In DCFCs, carbon is electrochemically directly oxidized to generate the power without a reforming process. Despite its compelling cost and performance advantages, the use of molten metal hydroxide electrolytes has been ignored by DCFC researches, primarily due to the potential lack of invariance of the molten hydroxide electrolyte caused by its reaction with carbon dioxide. This paper describes the electrochemistry of a patented medium-temperature DCFC based on molten hydroxide electrolyte, which overcomes the historical carbonate formation.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 delivering more than 40 A with the current density exceeding 250 mA/cm2. The cathode is of non-porous structure made of an inexpensive Fe–Ti alloy, and gaseous oxygen is introduced into the cell by bubbling humid air through the electrolyte. Results obtained indicated that the cell operation was under a mixed Ohmic-mass transfer control. Anode and cathode reaction mechanisms are also discussed.