Editing Electrochemical cell (section)

=== Fuel cell ===
[[File:Solid oxide fuel cell protonic.svg|thumb|Scheme of a proton-conducting fuel cell]]
{{main|Fuel cell}}
A [[fuel cell]] is an electrochemical cell that reacts hydrogen fuel with oxygen or another oxidizing agent, to convert chemical energy to [[electricity]].<ref name=":0">{{Cite web |title=Fuel Cells |url=https://www.energy.gov/eere/fuelcells/fuel-cells |access-date=2025-02-02 |website=US Department of Energy |language=en}}</ref>

Fuel cells are different from [[Battery (electricity)|batteries]] in requiring a continuous source of fuel and oxygen (usually from air) to sustain the chemical reaction, whereas in a battery the chemical energy comes from chemicals already present in the battery.<ref name=":0" />

Fuel cells can produce electricity continuously for as long as fuel and [[oxygen]] are supplied.<ref name=":0" />

They are used for primary and backup power for commercial, industrial and residential buildings and in remote or inaccessible areas. They are also used to power [[fuel cell vehicle]]s, including [[forklift]]s, automobiles, buses, boats, motorcycles and submarines.{{cn|date=December 2024}}

Fuel cells are classified by the type of electrolyte they use and by the difference in startup time, which ranges from 1 second for [[proton-exchange membrane fuel cell]]s (PEM fuel cells, or PEMFC) to 10 minutes for [[solid oxide fuel cell]]s (SOFC).<ref>{{Cite web |title=Comparison of Fuel Cell Technologies |url=https://www.energy.gov/eere/fuelcells/comparison-fuel-cell-technologies |access-date=2025-05-06 |website=Energy.gov |language=en}}</ref><ref>{{Cite web |last=Vskills |first=Team |title=Principle and Working Of Fuel Cell |url=https://www.vskills.in/certification/tutorial/principle-and-working-of-fuel-cell/ |access-date=2025-05-06 |website=Tutorial |language=en-US}}</ref>

There are many types of fuel cells, but they all consist of:

;anode: At the anode a catalyst causes the fuel to undergo oxidation reactions that generate [[proton]]s (positively charged hydrogen ions) and electrons. The protons flow from the anode to the cathode through the electrolyte after the reaction. At the same time, electrons are drawn from the anode to the cathode through an external circuit, producing [[direct current]] electricity.{{cn|date=December 2024}}
;cathode: At the cathode, another catalyst causes hydrogen ions, electrons, and oxygen to react, forming water.{{cn|date=December 2024}}
;electrolyte: Allows positively charged hydrogen ions (protons) to move between the two sides of the fuel cell.{{cn|date=December 2024}}

A related technology are [[Flow battery|flow batteries]], in which the fuel can be regenerated by recharging. Individual fuel cells produce relatively small electrical potentials, about 0.7 volts, so cells are "stacked", or placed in series, to create sufficient voltage to meet an application's requirements.<ref>{{Cite journal |last1=Qi |first1=Zhaoxiang |last2=Koenig |first2=Gary M. |date=2017-07-01 |title=Review Article: Flow battery systems with solid electroactive materials |journal=Journal of Vacuum Science & Technology B |volume=35 |issue=4 |pages=040801 |doi=10.1116/1.4983210 |bibcode=2017JVSTB..35d0801Q |issn=2166-2746|doi-access=free }}</ref> In addition to electricity, fuel cells produce water, heat and, depending on the fuel source, very small amounts of [[nitrogen dioxide]] and other emissions. The [[Efficient energy use|energy efficiency]] of a fuel cell is generally between 40 and 60%; however, if waste heat is captured in a [[cogeneration]] scheme, efficiencies up to 85% can be obtained.{{cn|date=December 2024}}

In 2022, the global fuel cell market was estimated to be $6.3 billion, and is expected to increase by 19.9% by 2030.<ref>{{Cite web |title=Fuel Cell Market Size, Share & Trends Analysis Report, 2030 |url=https://www.grandviewresearch.com/industry-analysis/fuel-cell-market |access-date=2023-04-18 |website=www.grandviewresearch.com |language=en}}</ref> Many countries are attempting to enter the market by setting renewable energy [[Gigawatt|GW]] goals.<ref>{{Cite web |title=Renewable energy targets |url=https://energy.ec.europa.eu/topics/renewable-energy/renewable-energy-directive-targets-and-rules/renewable-energy-targets_en |access-date=2023-04-22 |website=energy.ec.europa.eu |language=en}}</ref>