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3.1.5 Molten Carbonate Fuel Cells
Molten carbonate fuel cells (MCFCs) are another type of high-temperature fuel
cells. A molten mixture of salts, such as lithium, sodium, and potassium carbonate,
is used as the electrolyte. These salts melt and conduct carbonate ions (CO 3
2−
) from
the anode to the cathode when heated to about 600 °C. Molten carbonate salt mixture is suspended in a porous, chemically inert ceramic matrix of beta-alumina solid
electrolyte (BASE). Non-precious metals can be used as catalysts at the anode and
cathode. Molten carbonate fuel cells can reach efficiencies approaching 60%. Due
to the high temperatures at which MCFCs operate, fuels are converted to hydrogen
within the fuel cell itself by a process called internal reforming. Molten carbonate
fuel cells are not prone to poisoning by carbon monoxide or carbon dioxide.
Hydrocarbons have to be used as part of the fuel since the charge carriers in the
electrolyte are carbonate ions. Hydrogen is also needed at the anode. MCFCs are
mainly used for stationary power generation in the 50 kW to 5 MW range. The main
problem with MCFC is the slow dissolution of the cathode in the electrolyte.
References
1. H. Gasteiger, J. Garhe, in Handbook of heterogenous catalysis, ed. by G. Ertl, H. Knozinger,
F. Schuth, J. Weitkamp, vol. 8, (JWWiley VCH, 2008)
2. J.M. King, B. McDonald, Handbook of fuel cells-fundamentals, technology, applications, vol
4 (Wiley, Chichester, 2003), p. 832
3. J.M. King, H.R. Kunz, in Handbook of fuel cells-fundamentals, technology, applications, ed.
by W. Vielstich, A. Lamm, H. A. Gaistager, vol. 1, (Wiley, Chichester, 2003), p. 287
References