Hydrogen, the first element in the periodic table
Hydrogen is regularly mentioned as one of the energy sources of the future, especially for transportation.
Dihydrogen is a “clean” fuel in the sense that its combustion generates only water vapor.
Hydrogen is not present in the atmosphere except in trace amounts.
The most common source of hydrogen is water, whose molecules are composed of two hydrogen atoms and one oxygen atom.
Therefore, it is not a primary or fossil energy source, but a means of energy storage, just like a battery.