Hydrogen is a chemical element present, free in nature, very light and with a large amount of energy per unit mass. From the point of view of energy use, it allows to store large amounts of energy from any primary energy source. One of the most interesting methods to produce hydrogen is the electrolysis of water, a process by which, by means of electric current, the water molecule is dissociated and, in this way, to obtain hydrogen on the one hand, and oxygen on the other. In this way it is possible to store huge amounts of electrical energy in the form of hydrogen with high efficiency. The devices used to produce hydrogen by electrolysis are called electrolysers.