Editing Solid oxide fuel cell (section)

===DCFC===
For the direct use of solid coal fuel without additional gasification and reforming processes, a [[direct carbon fuel cell]] ([http://www.materialsviews.com/direct-carbon-fuel-cells-ultra-low-emission-technology-power-generation/ DCFC]) has been developed as a promising novel concept of a high-temperature energy conversion system. The underlying progress in the development of a coal-based DCFC has been categorized mainly according to the electrolyte materials used, such as solid oxide, molten carbonate, and molten hydroxide, as well as hybrid systems consisting of solid oxide and molten carbonate binary electrolyte or of liquid anode (Fe, Ag, In, Sn, Sb, Pb, Bi, and its alloying and its metal/metal oxide) solid oxide electrolyte.<ref>{{cite journal | last1 = Giddey | first1 = S | last2 = Badwal | first2 = SPS | last3 = Kulkarni | first3 = A | last4 = Munnings | first4 = C | year = 2012 | title = A comprehensive review of direct carbon fuel cell technology | journal = Progress in Energy and Combustion Science | volume = 38 | issue = 3| pages = 360–399 | doi = 10.1016/j.pecs.2012.01.003 | bibcode = 2012PECS...38..360G }}</ref> People's research on DCFC with GDC-Li/Na<sub>2</sub>CO<sub>3</sub> as the electrolyte, Sm<sub>0.5</sub>Sr<sub>0.5</sub>CoO<sub>3</sub> as cathode shows good performance. The highest power density of 48&nbsp;mW*cm<sup>−2</sup> can be reached at 500&nbsp;°C with O<sub>2</sub> and CO<sub>2</sub> as oxidant and the whole system is stable within the temperature range of 500&nbsp;°C to 600&nbsp;°C.<ref>{{Cite journal|last1=Wu|first1=Wei|last2=Ding|first2=Dong|last3=Fan|first3=Maohong|last4=He|first4=Ting|date=30 May 2017|title=A High Performance Low Temperature Direct Carbon Fuel Cell|journal=ECS Transactions|language=en|volume=78|issue=1|pages=2519–2526|doi=10.1149/07801.2519ecst|bibcode=2017ECSTr..78a2519W|osti=1414432|issn=1938-6737|url=https://www.osti.gov/biblio/1414432}}</ref>

'''SOFC operated on [[landfill gas]]'''

Every household produces waste/garbage on a daily basis. In 2009, Americans produced about 243 million tons of municipal solid waste, which is 4.3 pounds of waste per person per day. All that waste is sent to landfill sites. Landfill gas which is produced from the decomposition of waste that gets accumulated at the landfills has the potential to be a valuable source of energy since methane is a major constituent. Currently, the majority of the landfills either burn away their gas in flares or combust it in mechanical engines to produce electricity. The issue with mechanical engines is that incomplete combustion of gasses can lead to pollution of the atmosphere and is also highly inefficient.{{citation needed|date=December 2023}}

The issue with using landfill gas to fuel an SOFC system is that landfill gas contains hydrogen sulfide. Any landfill accepting biological waste will contain about 50-60 ppm of hydrogen sulfide and around 1-2 ppm mercaptans. However, construction materials containing reducible sulfur species, principally sulfates found in gypsum-based wallboard, can cause considerably higher levels of sulfides in the hundreds of ppm. At operating temperatures of 750&nbsp;°C hydrogen sulfide concentrations of around 0.05 ppm begin to affect the performance of the SOFCs.{{citation needed|date=December 2023}}

Ni + H<sub>2</sub>S → NiS + H<sub>2</sub>

The above reaction controls the effect of sulfur on the anode.

This can be prevented by having background hydrogen which is calculated below.

At 453 K the equilibrium constant is 7.39 x 10<sup>−5</sup>

ΔG calculated at 453 K was 35.833 kJ/mol

Using the standard heat of formation and entropy ΔG at room temperature (298 K) came out to be 45.904 kJ/mol

On extrapolation to 1023 K, ΔG is -1.229 kJ/mol

On substitution, K<sub>eq</sub> at 1023 K is 1.44 x 10<sup>−4</sup>. Hence theoretically we need 3.4% hydrogen to prevent the formation of NiS at 5 ppm H<sub>2</sub>S.<ref>{{Cite thesis|last=Khan|first=Feroze|date=1 January 2012|title=Effect of Hydrogen Sulfide in Landfill Gas on Anode Poisoning of Solid Oxide Fuel Cells|url=http://rave.ohiolink.edu/etdc/view?acc_num=ysu1338838003|publisher=Youngstown State University}}</ref>