NOVELTY - The electrolysis device comprises a cathode (1) immersed in an electrolytic solution comprising a weak acid and having a pH of 7-8.5, an anode (3) immersed in the electrolytic solution to form an electrochemically active biofilm at a surface of the anode, and a unit for collecting hydrogen. The anode comprises a biodegradable organic compound. The anode immersed electrolytic solution comprises microorganisms or consortia of microorganisms obtained from a natural medium, and marine sediments. The microorganisms are sown in the electrolytic solution.    USE - The electrolysis device such as a proton exchange membrane, a cationic membrane, a ceramic, an ultrafiltration membrane, an anion exchange membrane, a bipolar membrane and a polymeric gas separator is useful in an installation for the synthesis of hydrogen (all claimed), which is useful as an energy source for vehicles.    ADVANTAGE - The electrolysis device is simple, compact and reliable for producing hydrogen at high production rate with less consumption of energy and without any environmental risks.    DETAILED DESCRIPTION - The electrolysis device comprises a cathode (1) immersed in an electrolytic solution comprising a weak acid and having a pH of 7-8.5, an anode (3) immersed in the electrolytic solution to form an electrochemically active biofilm at a surface of the anode, and a unit for collecting hydrogen. The anode comprises a biodegradable organic compound. The anode immersed electrolytic solution comprises microorganisms or consortia of microorganisms obtained from a natural medium, and marine sediments. The microorganisms are sown in the electrolytic solution. The seeding is carried out by adding aqueous water effluents, marine sediments, biofilms or composts or pure cultures of microorganisms. The concentration of the weak acid is present between 0.1 moles per liter and the solubility of the electrolyte solution in which the cathode is immersed. The electrolytic solutions are separated by an element for allowing migration of ions between anodic and cathodic compartments. The organic compound is natural, synthetic or biomass derived organic compound. An INDEPENDENT CLAIM is included for an electrochemical process for synthesis of hydrogen.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of an electrolysis device.    Cathode (1)    Permeable membrane (2)    Anode (3)    Hydrogen measuring device (4)    Valve. (5)