Liquid or solid, the conductive material of the electrolyte makes it possible to control the passage of electrons.

A tank continuously supplies the anode and cathode with fuel : in the case of a hydrogen fuel cell, the anode receives hydrogen and the cathode oxygen, in other words air.
The anode causes the oxidation of the fuel and the release of electrons, which are forced by the ion-charged electrolyte to pass through an external circuit. This external circuit therefore offers a continuous electric current.

Ions and electrons, gathered in the cathode, then recombine with the second fuel, usually oxygen. This is reduction, generating water and heat in addition to electric current.
As long as it is supplied, the battery runs continuously.

At the anode, we therefore have an electrochemical oxidation of the hydrogen :

H2 → 2H+ + 2nd-

At the cathode, the reduction of oxygen is observed :

1⁄2O2 + 2H+ + 2nd- → H2O

The overall balance sheet is then :

H2 + 1/2 O2 → H2O

Proton Exchange Membrane Fuel Cells (PEMFC) :
PEMFCs use a polymer membrane, often Nafion®, as the electrolyte. They operate at relatively low temperatures (around 80-100°C) and are mainly used in transport applications, such as hydrogen cars, due to their fast start and high power density.

Solid oxide fuel cells (SOFCs) :
SOFCs use a solid electrolyte, such as yttria-stabilized zirconium oxide (YSZ), and operate at high temperatures (around 600-1000°C). They are efficient for stationary power generation and cogeneration due to their high efficiency and low sensitivity to fuel impurities.

High-Temperature Solid Oxide Fuel Cells (HT-SOFC) :
HT-SOFCs are a variant of SOFCs that operate at even higher temperatures (above 800°C). They offer high efficiencies and can be powered by a variety of fuels, making them an attractive option for stationary applications requiring high efficiency.

Fused carbonate fuel cells (FCFCs) :
MCFCs use a carbonate electrolyte that is fused at high temperatures (about 600-700°C). They are efficient for cogeneration and can run on fuels containing carbon dioxide, making them useful for capturing and storing CO2.

Alkaline fuel cells (AFCs) :
CFLs use an alkaline electrolyte, usually an aqueous solution of potash or sodium hydroxide. They are efficient and inexpensive, but they require platinum-based catalysts and work best with pure hydrogen, which limits their applications.

Phosphoric acid fuel cells (PAFC) :
PAFCs use a phosphoric acid electrolyte contained in a polybenzimidazole acid membrane. They operate at relatively high temperatures (around 150-220°C) and are often used in stationary cogeneration and power generation applications.

Proton exchange membrane (PEM) fuel cells :
PEM fuel cells are among the most commonly used, especially in transportation and stationary applications. They offer a high return, usually between 40% and 60%. However, this efficiency can vary depending on factors such as operating temperature, hydrogen pressure, and losses in the system.

Solid oxide fuel cells (SOFCs) :
SOFC fuel cells are known to offer high efficiencies, typically in excess of 50%. Some advanced SOFC fuel cells can achieve efficiencies of more than 60%. They are often used in stationary applications where high efficiency is essential.

High-Temperature Solid Oxide Fuel Cells (HT-SOFC) :
HT-SOFCs operate at much higher temperatures than conventional SOFCs, allowing them to achieve even higher efficiencies, typically in excess of 60%. These fuel cells are mainly used in stationary and cogeneration applications.

Fused carbonate fuel cells (FCFCs) :
MCFC fuel cells can achieve high efficiencies, typically between 50% and 60%. They are often used in cogeneration applications where waste heat can be recovered and used efficiently.

Clean transportation :
Fuel cells can be used as a power source for fuel cell vehicles (FCVs), such as cars, trucks, buses, and trains. PCVs use hydrogen as a fuel and generate electricity by combining hydrogen with oxygen from the air. They only generate water and heat as by-products, providing a clean alternative to internal combustion engine vehicles.

Stationary energy :
Fuel cells can be used as a stationary power source for a variety of applications, including backup and backup systems, telecommunications facilities, cell towers, base stations, energy management systems for commercial and residential buildings, and distributed power generation systems.

Portable Electronics :
Fuel cells can power portable electronic devices such as laptops, smartphones, tablets, and field measuring devices. Their high energy density and extended runtime make them an attractive solution for applications that require portable, long-life power.

Military Applications :
Fuel cells can be used in military applications such as drones, military vehicles, field surveillance and communication equipment, and defense systems, providing reliable and discreet power in demanding environments.

Space applications :
In the space industry, fuel cells are used to power satellites, space stations, and space probes. Their high efficiency, reliability, and low weight make them an attractive power source for long-term space missions.

Industrial applications :
Fuel cells can be used in a variety of industrial applications such as cogeneration, distributed power generation, wastewater treatment, heat and power generation for industrial processes, and hydrogen production from renewable sources.