A fuel cell converts the chemical energy in hydrogen and oxygen into direct current electrical energy by electrochemical reactions. Fuel cells are devices that convert hydrogen gas directly into low-voltage, direct current electricity. The cell has no moving parts.

The process is essentially the reverse of the electrolytic method of splitting water into hydrogen and oxygen. In the fuel cell, the cathode terminal is positively charged and the anode terminal is negatively charged. These electrodes are separated by a membrane. Hydrogen gas is converted into electrons and protons (positive hydrogen ions) at the anode. The protons pass through the membrane to the cathode, leaving behind negatively charged electrons. This creates a flow of direct current electricity between the terminals when connected with an external circuit. This current can power an electric motor placed in this circuit. The hydrogen ions, electrons, and oxygen combine at the cathode to form water, the only byproduct of the process.

Currently, most hydrogen is made from natural gas through a process known as reforming. Reforming separates hydrogen from hydrocarbons by adding heat. Hydrogen can also be produced from a variety of sources including water and biomass.

Fuel cells are self-contained power generation devices that are able to produce reliable electricity for residential, commercial, industrial and transportation applications. A fuel cell can convert hydrogen directly into electricity that can be used to power an electric car, for example, or a home.