Molten carbonate fuel cell

The molten carbonate fuel cell (engl. Molten Carbonate Fuel Cell , MCFC ) is a high temperature fuel cell that operates at an operating temperature between 580 ° C and 675 ° C. This type of cell uses an alkali carbonate mixed melt of lithium and potassium carbonate as the electrolyte .

principle

Building an MCFC

A mixture of hydrogen and carbon monoxide is used as the fuel gas on the anode side , which is produced by internal reforming from a methane-containing energy source such as fossil natural gas or biogas . During the subsequent water-gas shift reaction , carbon dioxide is produced (along with additional hydrogen), which mainly escapes as exhaust gas. The oxygen added there reacts under reduction with the CO ₂ from the anode half-cell to form carbonate ions, which migrate through the electrolyte and combine at the anode with the hydrogen to be oxidized to form water and carbon dioxide. The latter is fed to the cathode , so that an electrochemical CO ₂ -CO ₃ ^2- cycle is formed with a constant supply of hydrogen and oxygen, in which water is the product. In the overall process, methane from natural gas or biogas is oxidized to carbon dioxide and water by means of atmospheric oxygen.

The materials for building this type of cell are comparatively inexpensive because they work in a temperature range at which an acceptable reaction rate is achieved without expensive noble metal catalysts and cheaper nickel electrodes can be used. On the other hand, the operating temperature is not yet so high that expensive high - temperature materials can be dispensed with. The type is particularly difficult because of the wear and tear caused by the constant warming up to high temperatures and cooling of the system. The toxicity and flammability of the hydrogen-rich and CO -containing reformate from internal reforming also place high but manageable demands on safety. The MCFC should be used in local and larger power plants in the future.

Reaction equations

	equation
Reforming	${\displaystyle \mathrm {CH_{4}+H_{2}O\longrightarrow CO+3H_{2}} }$ ${\displaystyle \mathrm {CO+H_{2}O\longrightarrow CO_{2}+H_{2}} }$ Steam reforming with shift reaction
anode	${\displaystyle \mathrm {H_{2}+{CO_{3}}^{2-}\longrightarrow H_{2}O+CO_{2}+2\ e^{-}} }$ Oxidation / electron donation
cathode	${\displaystyle \mathrm {{\frac {1}{2}}O_{2}+CO_{2}+2\ e^{-}\longrightarrow {CO_{3}}^{2-}} }$ Reduction / electron uptake
Overall response	${\displaystyle \mathrm {2\ H_{2}+O_{2}+2CO_{2}(K)\longrightarrow 2\ H_{2}O+2CO_{2}(A)} }$ Redox reaction / cell reaction

Web links

• Key figures of an MCFC fuel cell ( Memento from July 7, 2007 in the Internet Archive )