NOVELTY - Producing hydrogen gas comprises: providing electrolytic cell (3) comprising anode (8) and cathode (9), anode compartment (4), cathode compartment (6), and cation exchange membrane; introducing first aqueous solution in anode compartment; introducing second aqueous solution in cathode compartment; applying electrical potential difference between anode and cathode; reacting aluminum with aqueous alkaline solution; transferring at least part of sodium aluminate product to anode compartment; and transferring at least part of liquid phase of reaction mixture to cathode compartment.    USE - The method is useful for producing hydrogen gas.    ADVANTAGE - The method: lowers the hydrogen gas production costs than the conventional methods; and is simple to use.    DETAILED DESCRIPTION - Producing hydrogen gas comprises: providing an electrolytic cell (3) comprising an anode (8) and a cathode (9), an anode compartment (4) which is disposed the anode, a cathode compartment (6) which is disposed the cathode, and a cation exchange membrane disposed between the anode and cathode compartments, in which the cation exchange membrane is permeable to cations and arranged to allow passage of a cation from the anode compartment to the cathode compartment; introducing a first aqueous solution (which is alkaline or neutral) in the anode compartment so as to immerse at least part of the anode; introducing a second aqueous solution (which is alkaline or neutral) in the cathode compartment so as to immerse at least part the cathode; applying an electrical potential difference between the anode and the cathode so as to cause electrolysis of the water contained in the first and second aqueous solutions; reacting aluminum with an aqueous alkaline solution so as to produce hydrogen gas and sodium aluminate; transferring at least part of the sodium aluminate product to the anode compartment to obtain an alumina precipitated in the anode compartment; and transferring at least part of liquid phase of the reaction mixture contained in the anode compartment to the cathode compartment. INDEPENDENT CLAIMS are also included for:    (1) a hydrogen gas production plant, comprising: at least one electrolytic cell; a first fluid transfer device fluidly connected to the anode compartment and the cathode compartment, where the first fluid transfer device is arranged to transfer a part of the liquid phase of a reaction mixture contained in the anode compartment, from the anode compartment to the cathode compartment; and a second fluid transfer device fluidly connected to the anode compartment and arranged to supply sodium aluminate to the anode compartment; and    (2) a device for producing electrical energy, comprising the hydrogen gas production plant, and a hydrogen gas fuel cell arranged to apply an electrical potential difference between the anode and the cathode, where the hydrogen gas fuel cell is configured to be supplied with hydrogen gas from the hydrogen gas produced in at least one electrolytic cell.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the hydrogen gas production plant.    Electrolytic cell (3)    Anode compartment (4)    Cathode compartment (6)    Anode (8)    Cathode (9)