3. Hydrogen purification

For fuel cells to work properly and last a long time, the hydrogen must be pure, with a 3N (99.9%) grade or higher, and above all free of carbon oxides (less than 20 ppm). This is why the gas produced by the methods described above usually needs to be purified, with the exception of water electrolysis production processes, which already include this step. Several processes are available:

• separation by membranes a few hundred nanometers to a few millimeters thick, and selective adsorption, which uses porous aluminosilicate-type materials, will, under the effect of a transfer force, allow or prevent the passage of certain components