Molten Carbonate Fuel Cell (MCFC)

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Molten Carbonate Fuel Cell (MCFC)

  • A schematic diagram of a molten carbon fuel cell is shown in Figure. It is a high temperature fuel cell.
Molten Carbonate Fuel Cell
  • The fuel, oxidant, electrodes and the electrolyte used are as follows :

Fuel : Mixture of H2, and CO
Oxidant : O2, or air
Electrodes : Porous nickel electrodes
Electrolyte : Mixture of carbonate salts either lithium carbonate and potassium carbonate or lithium carbonate and sodium carbonate.

  • Since it uses the carbonates of alkali metals as electrolytes in molten (liquid) phase, its operating temperatures must be in the range of (650°C-700°C). The electrolytes are held in a sponge like ceramic matrix. When the mixture of carbonate salts are heated they become conducive to CO—3 ions.
  • The carbonate ions so produced flow from cathode to anode where they combine with hydrogen to produce CO2, water (H2O) and electrons and while combining with CO it produce CO2, and electrons.
  • The electrons flow from anode to cathode to generate electrical power and heat.

At anode :  H2
+ CO—3 = H2O + CO2 + 2e

                       CO
+ CO—3 = 2CO2 + 2e

At cathode : O2 + 2 CO2
+ 4e = 2CO—3

Overall cell reaction : H2
+ CO + O2 = H2O + CO2 + heat

The e m.f. produced by each cell is theoretically 1V and actual e.m.f. of 0.8 V at 700°C. The expected efficiency is about 60%.

Advantages of MCFC system :

  1. It uses comparatively cheaper fuels like H2, and CO.
  2. It can utilize even fossil fuel like coal for producing the H2, and CO by its gasification.
  3. Discharges are mainly water vapour, CO2, and N2, (if air is used as oxidant) at a temperature exceeding 550°C. These hot gases can be used for generation of steam for power generation or as process heat for industries.
  4. Efficiency of cell is high in the range of 60%. It’s overall efficiency can be further increased by utilizing the heat of the products in co-generation plant.

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