Hydrogen (H2) will play an important role in developing sustainable transportation worldwide, because in the future it may be produced in virtually unlimited quantities using renewable resources. Hydrogen has been used effectively in a number of internal combustion engine vehicles as pure hydrogen mixed with natural gas. For more information on this fuel blend, see the hydrogen/natural gas blend site.
In addition, hydrogen is used in a growing number of demonstration fuel cell vehicles. Hydrogen and oxygen from air fed into a proton exchange membrane (PEM) fuel cell "stack" produce enough electricity to power an electric automobile, without producing harmful emissions. For more information, see the hydrogen vehicles page.
Reference:
U.S. Department of Energy, Energy Efficiency and Renewable Energy | 
