NOVELTY - The system for production (5-1), conversion and reproduction (5-3) of gas-liquid-gas hydrogen cycle (5-5) with absorption of carbon dioxide (CO2) (5-4) with change of each state, comprises a water electrolyzer device composed of an electrolysis chamber, electrodes, an electrolyte and a solid and/or flexible membrane, a device for transformation of hydrogen gas in a stable liquid by mixture of CO2, and a device for production of hydrogen gas at less than 0.1 volts without emission of CO2. A second electrolyzer of highly alkaline and/or saturated solution of CO2 is arranged.    USE - The system is useful for production, conversion and reproduction of gas-liquid-gas hydrogen cycle, which is useful in stationary, mobile, submersible and/or wheeled vehicles (claimed).    ADVANTAGE - The system is capable of energy efficiently and economically producing, converting and reproducing the gas-liquid-gas hydrogen with high production, avoids the risk during the storage of hydrogen by transforming it into a stable liquid (methanol) and emissions of CO2, and avoids the constraints of cleanliness and minimizes the pollution of air thus preventing the adverse effect on the earth's climate and ecosystem.    DETAILED DESCRIPTION - The system for production (5-1), conversion and reproduction (5-3) of gas-liquid-gas hydrogen cycle (5-5) with absorption of carbon dioxide (CO2) (5-4) with change of each state, comprises a water electrolyzer device composed of an electrolysis chamber, electrodes, an electrolyte and a solid and/or flexible membrane, a device for transformation of hydrogen gas in a stable liquid by mixture of CO2, and a device for production of hydrogen gas at less than 0.1 volts without emission of CO2. A second electrolyzer of highly alkaline and/or saturated solution of CO2 is arranged for producing hydrogen. The hydrogen product reacts with CO2 for producing proper methanol, and is produced by electrolysis of methanol. An electrochemical and/or photochemical capturing device is equipped with system for reduction of CO2 catalyzed by a complex of ruthenium, nickel, rhenium, ruthenium nanoparticles, rhenium nanoparticles, platinum, porous nanoparticles, structured nanoparticles and self-assembled nanoparticles without liquid solution, and powered by a renewable and/or conventional energy source. Catalysts are deposited on the electrodes by piezo-electric impression on solid or flexible substrate.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a process for production, storage and reproduction of hydrogen (Drawing includes non-English language text).    Production (5-1)    Storage (5-2)    Reproduction (5-3)    Carbon dioxide (5-4)    Gas-liquid-gas hydrogen cycle. (5-5)