A device for generating hydrogen gas is provided. The device (101) comprises a first hydrogen-containing composition (107) that reacts with a second composition to evolve hydrogen gas; a dispenser (105) adapted to apply the first composition to a first porous member (109); and a conduit (111) adapted to supply the second composition to the first porous member. In a preferred embodiment, the first composition is selected from the group consisting of hydrides, borohydrides and boranes, the second composition is water, and the dispenser is spring-loaded and is charged with the first composition. As the first composition reacts with water at the interface to evolve hydrogen gas, the dispenser forces the reaction product across the interface and out of the dispenser, where it will not interfere with the progress of the hydrogen evolution reaction.