Fuel Cells

A fuel cell is a device that produces electricity directly from a chemical reaction between a fuel and an oxidant, most commonly hydrogen and oxygen. Unlike a battery, which stores a fixed amount of energy and must be recharged or replaced, a fuel cell continues to generate power as long as fuel and oxygen are supplied to it. This makes it more like an engine that runs on fuel, but one that converts chemical energy into electricity without combustion.

Inside a fuel cell, the fuel and the oxidant are kept apart by an electrolyte and a pair of electrodes. Hydrogen is fed to one electrode, where it gives up electrons that flow through an external circuit as electric current before reaching the other electrode, where they combine with oxygen. The transfer of electrons in this controlled oxidation-reduction reaction is what produces the current. Because the reaction does not involve burning, fuel cells can convert chemical energy to electricity efficiently and quietly.

The main by-product of a hydrogen fuel cell is water, with little or no harmful emission at the point of use, which makes the technology attractive for clean energy. Fuel cells are used to power vehicles, to supply electricity for buildings, and as a source of energy where quiet, reliable power is needed. Their wider use depends on producing and distributing suitable fuel, especially hydrogen, in a practical and sustainable way. Animations and applets help illustrate the flow of ions and electrons that the process involves.

Frequently asked questions

How is a fuel cell different from a battery?

A battery stores a fixed amount of energy, while a fuel cell keeps producing electricity as long as fuel and oxygen are supplied, much like an engine running on fuel.

What does a hydrogen fuel cell produce?

It produces electricity, heat, and water. Because water is the main by-product, the cell emits little or no pollution at the point of use.

How does a fuel cell generate electricity?

Hydrogen at one electrode releases electrons that flow through an external circuit as current before combining with oxygen at the other electrode, in a controlled redox reaction.