1. Hydrogen production by electrolysis: general principle

The production of hydrogen by electrolysis of water (liquid or vapor) is based on an electrochemical decomposition reaction, using direct electric current, of the water molecule (H ₂ O) into hydrogen (H ₂ ) and oxygen (O ₂ ). This reaction, given by the equation (1) , takes place in an electrochemical cell that typically consists of two electrodes (anode and cathode) connected to a direct current generator, separated by an electrolyte that acts as an ionic conductor and separator of the reaction products. This electrolyte can be of different types (alkaline liquid, solid) and determines the operating parameters, in particular the temperature, of the electrolyzer...