An electrolytic cell for generating hydrogen through the electrolysis of water, including an anodic compartment and a cathodic compartment separated by a solid polymeric electrolyte alkaline membrane. The anodic compartment includes a positive electrode or anode at least partially submerged in a layer of water, and the cathodic compartment includes a negative electrode or cathode. The cell is arranged between a first closing plate and a second closing plate. A tie-rod, provided in the central portion of the first closing plate, passes through the first closing plate, the cell and the second closing plate. A central collector for conveying the hydrogen generated in the cathodic compartment is arranged coaxially to the tie-rod and is in communication with the cathodic compartment through an opening formed in the tie-rod.