Hydrogen is the most common element in the universe.

It is the lightest chemical element, a colorless, odorless gas, poorly soluble in water, which normally appears as the H2 molecular form. At 0⁰C and 1 atm. is 14.4 times lighter than air. From the point of view of potential storage the low critical hydrogen temperature (-239,9⁰C) is an important parameter, which makes condensation of this gas more difficult than liquefaction of air or most other gases.

It causes serious difficulties in hydrogen storage and transport, and basically we can only compress it to a very high pressure of up to 700 atm nowadays. The unique property of hydrogen is its considerable solubility in some metals. At high temperatures, it dissolves in: platinum, nickel, iron, copper. On one hand, it is a chance to increase the capacity of hydrogen tanks, but can also be a serious problem related to the so-called hydrogen corrosion, such as penetration of hydrogen molecules into the metal structure. It has a significant impact on the durability of e.g. metal reactors and tanks. Currently, multi-layer composite tanks are used to prevent the phenomenon of hydrogen penetrating the walls of the tanks. Intensive research is  conducted to find the most effective hydrogen storage way.

The main sources of hydrogen are: water and organic compounds, mainly based on carbon and hydrogen atoms. So obtaining pure hydrogen requires the use of an appropriate portion of energy.