Editing Fuel cell (section)

====Molten-carbonate fuel cell====
{{Main|Molten carbonate fuel cell}}
[[Molten carbonate fuel cell]]s (MCFCs) require a high operating temperature, {{convert|650|°C|abbr=on|-1}}, similar to [[Solid oxide fuel cell|SOFCs]]. MCFCs use lithium potassium carbonate salt as an electrolyte, and this salt liquefies at high temperatures, allowing for the movement of charge within the cell – in this case, negative carbonate ions.<ref name=moltencarb>[http://www.fossil.energy.gov/programs/powersystems/fuelcells/fuelcells_moltencarb.html "Molten Carbonate Fuel Cell Technology"]. U.S. Department of Energy, accessed 9 August 2011</ref>

Like SOFCs, MCFCs are capable of converting fossil fuel to a hydrogen-rich gas in the anode, eliminating the need to produce hydrogen externally. The reforming process creates {{CO2}} emissions. MCFC-compatible fuels include natural gas, [[biogas]] and gas produced from coal. The hydrogen in the gas reacts with carbonate ions from the electrolyte to produce water, carbon dioxide, electrons and small amounts of other chemicals. The electrons travel through an external circuit, creating electricity, and return to the cathode. There, oxygen from the air and carbon dioxide recycled from the anode react with the electrons to form carbonate ions that replenish the electrolyte, completing the circuit.<ref name=moltencarb/> The chemical reactions for an MCFC system can be expressed as follows:<ref>[http://www.fctec.com/fctec_types_mcfc.asp "Molten Carbonate Fuel Cells (MCFC)"]. FCTec.com, accessed 9 August 2011 {{webarchive |url=https://web.archive.org/web/20120303125426/http://www.fctec.com/fctec_types_mcfc.asp |date=3 March 2012 }}</ref>

:''Anode reaction'': CO<sub>3</sub><sup>2−</sup> + H<sub>2</sub> → H<sub>2</sub>O + CO<sub>2</sub> + 2e<sup>−</sup>
:''Cathode reaction'': CO<sub>2</sub> + ½O<sub>2</sub> + 2e<sup>−</sup> → CO<sub>3</sub><sup>2−</sup>
:''Overall cell reaction'': H<sub>2</sub> + ½O<sub>2</sub> → H<sub>2</sub>O

As with SOFCs, MCFC disadvantages include slow start-up times because of their high operating temperature. This makes MCFC systems not suitable for mobile applications, and this technology will most likely be used for stationary fuel cell purposes. The main challenge of MCFC technology is the cells' short life span. The high-temperature and carbonate electrolyte lead to corrosion of the anode and cathode. These factors accelerate the degradation of MCFC components, decreasing the durability and cell life. Researchers are addressing this problem by exploring corrosion-resistant materials for components as well as fuel cell designs that may increase cell life without decreasing performance.<ref name=Types1/>

MCFCs hold several advantages over other fuel cell technologies, including their resistance to impurities. They are not prone to "carbon coking", which refers to carbon build-up on the anode that results in reduced performance by slowing down the internal fuel [[Fossil fuel reforming|reforming]] process. Therefore, carbon-rich fuels like gases made from coal are compatible with the system. The United States Department of Energy claims that coal, itself, might even be a fuel option in the future, assuming the system can be made resistant to impurities such as sulfur and particulates that result from converting coal into hydrogen.<ref name=Types1/> MCFCs also have relatively high efficiencies. They can reach a fuel-to-electricity efficiency of 50%, considerably higher than the 37–42% efficiency of a phosphoric acid fuel cell plant. Efficiencies can be as high as 65% when the fuel cell is paired with a turbine, and 85% if heat is captured and used in a [[cogeneration|combined heat and power]] (CHP) system.<ref name=moltencarb/>

FuelCell Energy, a Connecticut-based fuel cell manufacturer, develops and sells MCFC fuel cells. The company says that their MCFC products range from 300&nbsp;kW to 2.8&nbsp;MW systems that achieve 47% electrical efficiency and can utilize CHP technology to obtain higher overall efficiencies. One product, the DFC-ERG, is combined with a gas turbine and, according to the company, it achieves an electrical efficiency of 65%.<ref>[http://www.fuelcellenergy.com/products.php "Products"]. FuelCell Energy, accessed 9 August 2011 {{webarchive |url=https://archive.today/20130111041426/http://www.fuelcellenergy.com/products.php |date=11 January 2013 }}</ref>