U.S. Department of Energy: Energy Efficiency and Renewable Energy

Fuel Cell Technologies OfficeHydrogen Production

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Photo of hydrogen production in photobioreactor

Hydrogen, chemical symbol "H", is the simplest element on earth. An atom of hydrogen has only one proton and one electron. Hydrogen gas is a diatomic molecule—each molecule has two atoms of hydrogen (which is why pure hydrogen is commonly expressed as "H2"). Although abundant on earth as an element, hydrogen combines readily with other elements and is almost always found as part of another substance, such as water, hydrocarbons, or alcohols. Hydrogen is also found in biomass, which includes all plants and animals.

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Content Last Updated: 12/15/2008