A Direct Carbon Fuel Cell (DCFC) is a fuel cell that uses a carbon rich material as a fuel. The cell produces energy by combining carbon and oxygen, which releases carbon dioxide as a by-product.
The total reaction of the cell is C + O2 → CO2. The process in half cell notation:
Anode: C + 2 O2- → CO2 + 4 e-
Cathode: O2 + 4 e- → 2 O2-
Despite this release of carbon dioxide, the direct carbon fuel cell is more environmentally friendly than traditional carbon burning techniques. Due to its higher efficiency, it requires less carbon to produce the same amount of energy. Also, because pure carbon dioxide is emitted, carbon capture techniques are much cheaper than for conventional power stations. Utilized carbon can be in the form of coal, coke, char, or a non-fossilized source of carbon.
The second one is molten hydroxides fuel cell. William W. Jacques obtained an US Patent 555,511 in this type of fuel cell in 1896. Prototypes have been demonstrated by the research group, SARA, Inc.
The fourth is a molten tin anode solid oxide fuel cell design, which utilizes molten tin and tin oxide as an inter stage reaction between oxidation of the carbon dissolving in the anode and reduction of oxygen at the solid oxide cathode.