Electrochemical system for the electrolysis of water, comprising: • a main inlet for receiving water to be electrolyzed, a first outlet for providing hydrogen produced and a second outlet for providing oxygen produced; • an electrolysis device comprising a membrane-electrode assembly formed of a first anode and of a first cathode separated from one another by a first proton-exchange membrane, the first anode being suitable for carrying out the oxidation of the water and the first cathode being suitable for carrying out the reduction of the protons, o the first anode being in fluidic connection with an inlet connected to the main inlet and with an outlet; • characterized in that it comprises: • a separation device comprising a membrane-electrode assembly formed of a second anode and of a second cathode separated from one another by a second proton-exchange membrane, the second anode being suitable for carrying out the oxidation of the hydrogen and the second cathode being suitable for carrying out the reduction of the protons, o the second cathode being in fluidic connection with an outlet connected to the first outlet of the electrochemical system; o the second anode being in fluidic connection with an inlet connected to the outlet of the first anode and with an outlet connected to the second outlet of the electrochemical system. • a main inlet for receiving water to be electrolyzed, a first outlet for providing hydrogen produced and a second outlet for providing oxygen produced; • an electrolysis device comprising a membrane-electrode assembly formed of a first anode and of a first cathode separated from one another by a first proton-exchange membrane, the first anode being suitable for carrying out the oxidation of the water and the first cathode being suitable for carrying out the reduction of the protons, o the first anode being in fluidic connection with an inlet connected to the main inlet and with an outlet; o the first anode being in fluidic connection with an inlet connected to the main inlet and with an outlet; • characterized in that it comprises: • a separation device comprising a membrane-electrode assembly formed of a second anode and of a second cathode separated from one another by a second proton-exchange membrane, the second anode being suitable for carrying out the oxidation of the hydrogen and the second cathode being suitable for carrying out the reduction of the protons, o the second cathode being in fluidic connection with an outlet connected to the first outlet of the electrochemical system; o the second anode being in fluidic connection with an inlet connected to the outlet of the first anode and with an outlet connected to the second outlet of the electrochemical system. • a separation device comprising a membrane-electrode assembly formed of a second anode and of a second cathode separated from one another by a second proton-exchange membrane, the second anode being suitable for carrying out the oxidation of the hydrogen and the second cathode being suitable for carrying out the reduction of the protons, o the second cathode being in fluidic connection with an outlet connected to the first outlet of the electrochemical system; o the second anode being in fluidic connection with an inlet connected to the outlet of the first anode and with an outlet connected to the second outlet of the electrochemical system. o the second cathode being in fluidic connection with an outlet connected to the first outlet of the electrochemical system; o the second anode being in fluidic connection with an inlet connected to the outlet of the first anode and with an outlet connected to the second outlet of the electrochemical system.