How fuel cells work

A fuel cell is a device for harnessing the energy that is liberated when hydrogen, or a hydrogenrich fuel, reacts with oxygen to produce water. Normally, when hydrogen and oxygen react a flame and heat energy is produced. In a fuel cell a flame is not produced, and the reaction produces both heat and electricity.

In some ways a fuel cell is similar to a battery. Both are electrochemical devices in which an electric current is produced from chemical reactions that take place at the electrodes. A battery, however, stores electricity and needs regular recharging or replacement; a fuel cell will continue producing electricity as long as it is supplied with fuel.

A single fuel cell consists of an electrolyte sandwiched between two thin porous electrodes, the anode and the cathode. The anode of the cell is usually coated with a special catalyst which splits each hydrogen molecule into two protons (H+ ions) and two negatively charged electrons.

The electrons leave the anode and provide the electrical current in the external circuit to which the fuel cell is connected. Oxygen, usually from air, is fed to the cathode of the cell where it reacts with protons and the electrons returning from the external circuit to produce water.