Fuel cell

A fuel cell instead receives a fuel, such as hydrogen, and oxygen or air from outside. The fuel is oxidised electrochemically: reactions at the cell’s two electrodes separate the transfer of electrons, producing a potential difference between its terminals. Connect the terminals through a complete circuit and electrons can flow through that circuit, supplying electrical energy.

A hydrogen–oxygen fuel cell uses a chemical reaction to produce a voltage. Hydrogen and oxygen enter the cell from external supplies. Hydrogen gives up electrons at one electrode, while oxygen gains electrons at the other.

A fuel cell also uses a chemical reaction, but fuel and oxygen are fed in from outside. It can therefore keep supplying electricity while those reactants are provided and the cell remains in working order.

A hydrogen–oxygen fuel cell is constructed so that the reaction transfers much of its energy electrically instead. The electricity can drive an electric motor or another device.