Electrochemical process for the production of pressurized gaseous hydrogen by electrolysis then depolarization

Electrochemical process for the production of pressurized gaseous hydrogen, characterized in that it consists essentially of implementing, in at least one chamber, at least one step El of electrolysis of an electrolyte comprising at least one solvent, preferably aqueous, this electrolysis step El converting electrical energy into chemical energy, with production of gaseous oxygen in a chamber El, and at least one step C° of converting this chemical energy into oxidation-reduction energy with production of gaseous hydrogen in a closed chamber C° that is identical to or different from, preferably identical to, chamber El;

• wherein:
• the electrolyte comprises Mm+ ions, M corresponding to the redox pair (Mm+/M), and Aa+ ions of at least one depolarization additive A corresponding to a redox pair (Aa+/A) where:
• the absolute value of the overvoltage of the hydrogen evolution reaction on the metal M is greater than the difference Eth(H+/H2)−Eth(Mm+/M) in acidic medium and than the difference Eth(H2O/H2)−Eth(Mm+/M) in basic medium;
• Eth(Aa+/A)<Eth(H+/H2) in acidic medium;
• Eth(Aa+/A)<Eth(H2O/H2) in basic medium;
• m is an integer;
• preferably between −5 and 5, and more preferably between −4 and 4
• a is an integer;
• preferably between −5 and 5, and more preferably between −4 and 4
• the absolute value of the overvoltage of the hydrogen evolution reaction on the metal A is less than the difference Eth(H+/H2)−Eth(Mm+/M) in acidic medium and than the difference Eth(H2O/H2)−Eth(Mm+/M) in basic medium;
• the electrolysis step El is initiated by supplying current between the anode and the cathode;
• Aa+ and Mm+ are respectively deposited in the form of A and M on the cathode during the electrolysis step El and gaseous oxygen is released at the anode;
• the electrolysis step El is stopped by cutting off the supply of current between the anode and the cathode;
• local depolarization effects then appear between A, M, and the H+ ions, said effects leading to the production of gaseous hydrogen and dissolution of M and A into Mm+ and Aa+ at the electrode which serves as the cathode during step El;
• which corresponds to the conversion step C′;
• The gaseous hydrogen thus produced is collected, preferably under a pressure PHyd;
• The gaseous hydrogen thus collected is possibly stored outside the chamber.