A device for generating hydrogen by hydrolysis of a hydride comprising a reactor containing the hydride in solid form, in the divided state or not, and comprising at least one orifice for removing the hydrogen produced; means for releasing the water required for the hydrolysis reaction; and at least one envelope suitable for isolating the hydride from the water required for the hydrolysis reaction, the envelope being made from a consumable material. According to the present invention, the envelope is suitable for contacting the water with the hydride in a site capable of serving as the seat of the hydrolysis reaction and of moving in the reactor as the material constituting the envelope is consumed by the hydrolysis reaction products.