The molten carbonate fuel cell (MCFC) gets its name because it uses molten carbonate salt as the electrolyte. MCFCs are high-temperature fuel cells in which the electrolyte is suspended in a porous, chemically inert ceramic matrix. They are currently being operated on natural gas and other fuels containing methane in stationary applications in the wastewater treatment, industrial, hotel and government markets.
They must operate at the extremely high temperature of 650°C (roughly 1,200°F) or above to obtain good conductivity of the electrolyte. This enables the use of non-precious metals as catalysts at the anode and cathode, reducing costs and enables reformation of gaseous fuels to hydrogen within the fuel cell eliminating the need to supply hydrogen to the fuel cell. MCFCs can reach efficiencies approaching 60 percent; when the waste heat is captured and used, overall fuel efficiencies can be as high as 85 percent.
The anode process involves a reaction between hydrogen and carbonate ions (CO3=) from the electrolyte which produces water and carbon dioxide (CO2) while releasing electrons to the anode. The cathode process combines oxygen and CO2 from the oxidant stream with electrons from the cathode to produce carbonate ions which enter the electrolyte. The need for CO2 in the oxidant stream requires a system for collecting CO2 from the anode exhaust and mixing it with the cathode feed stream.
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