Nepedia
Back to Discover
Advanced Reader
💻

Fuel cell

technology Maturity 9-11 Next article →

A fuel cell is an electrochemical cell designed to convert chemical energy into electricity.

Fuel Cell Block Diagram
Fuel Cell Block Diagram

It achieves this conversion through a pair of redox reactions. Unlike most batteries, which store chemical energy within their own structure, a fuel cell requires a continuous supply of fuel and an oxidizing agent. Hydrogen is a common fuel, while oxygen from the air often serves as the oxidizing agent. Because they do not rely on internal stores, fuel cells can produce electricity continuously as long as these reactants are supplied. This makes them a unique tool for generating steady power.

To understand how a fuel cell works, one must look at its three primary components: the anode, the cathode, and the electrolyte.

Solid oxide fuel cell protonic
Solid oxide fuel cell protonic

The process begins at the anode, where a catalyst triggers an oxidation reaction. This reaction causes the fuel to split into ions and electrons. In many cells, these are positively charged hydrogen ions, also known as protons. The electrolyte is a special substance that allows these ions to pass through to the other side. However, the electrolyte is electrically insulating, meaning it blocks the flow of electrons.

Because the electrons cannot pass through the electrolyte, they are forced to travel through an external circuit to reach the cathode. This flow of electrons through the wire produces direct current electricity.

PEM fuelcell
PEM fuelcell

Once the ions and electrons reach the cathode, they undergo a second reaction. At the cathode, another catalyst facilitates a reaction between the ions, the electrons, and the oxygen. This process typically results in the formation of water and sometimes other products. By separating the paths of the ions and the electrons, the cell creates a controlled loop of moving energy.

Fuel cells are categorized by their electrolyte type and their start-up speeds. For example, proton-exchange membrane fuel cells (PEMFC) are known for rapid activation, starting in as little as one second. In contrast, solid oxide fuel cells (SOFC) may require up to 10 minutes to start.

SEM micrograph of an MEA cross section
SEM micrograph of an MEA cross section

Because an individual fuel cell produces a relatively small electrical potential—roughly 0.7 volts—they are often combined into a "stack." By placing cells in series, engineers can increase the voltage to meet specific needs. They can also connect cells in parallel to increase the available current.

The history of this technology spans nearly two centuries. Sir William Grove first described crude fuel cells in 1838.

1839 William Grove Fuel Cell
1839 William Grove Fuel Cell

Later, in 1932, Francis Thomas Bacon developed a hydrogen-oxygen fuel cell that allowed for practical commercial use. This led to the development of the alkaline fuel cell, or Bacon fuel cell. NASA utilized these cells starting in the mid-1960s to power satellites and space capsules. These missions demonstrated that fuel cells could provide both electricity and drinking water for astronauts.

Today, fuel cells are used in a wide variety of applications. They provide primary and backup power for residential, commercial, and industrial buildings. They are also vital for remote or inaccessible locations. In transportation, fuel cells power diverse vehicles, including automobiles, buses, trains, boats, and motorcycles.

Toyota mirai trimmed
Toyota mirai trimmed

Even submarines use this technology for propulsion.

U Boot 212 HDW 1
U Boot 212 HDW 1

In some settings, such as hospitals or universities, stationary fuel cells are used in cogeneration schemes. These schemes capture waste heat to improve efficiency. While standard fuel cell efficiency ranges between 40% and 60%, cogeneration can push efficiency up to 85%.

While fuel cells are often associated with clean energy, their emissions depend on the fuel source. When using pure hydrogen, the primary byproduct is water vapor and heat.

condensation
condensation

However, if hydrocarbon fuels like methanol or diesel are used, the process may release carbon dioxide. PEMFCs generally produce fewer nitrogen oxides than SOFCs because they operate at lower temperatures. This chemical versatility allows fuel cells to connect to many different energy systems, making them a significant part of modern electrochemical research.

628 words

Where will your curiosity go next?

Keep exploring at your chosen reading level.

🖼️ Images & Media (15)
File:Fuel cell NASA p48600ac.jpg
Fuel cell NASA p48600ac.jpg
File:Solid oxide fuel cell protonic.svg
Solid oxide fuel cell protonic.svg
File:AllByYear-2023-10-24.png
AllByYear-2023-10-24.png
File:1839 William Grove Fuel Cell.jpg
1839 William Grove Fuel Cell.jpg
File:Fuel Cell Block Diagram.svg
Fuel Cell Block Diagram.svg
File:PEM fuelcell.svg
PEM fuelcell.svg
File:condensation.jpg
condensation.jpg
File:SEM micrograph of an MEA cross section.jpg
SEM micrograph of an MEA cross section.jpg
File:U Boot 212 HDW 1.jpg
U Boot 212 HDW 1.jpg
File:Fuelcell.jpg
Fuelcell.jpg
File:Toyota mirai trimmed.jpg
Toyota mirai trimmed.jpg
File:Element One.jpg
Element One.jpg

+ 3 more

More to explore

What is Nepedia?

A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.