The present application is directed to gas generators comprising a fuel mixture and a catalyst. The catalyst is contained in a self-regulated reactor or buoy, and selectively opens and closes to produce a gas in accordance with the demand for gas. This fuel mixture is generally a solution formed by dissolving a solid fuel component in a liquid fuel component. The mixing preferably occurs before the first use, and more preferably occurs immediately prior to the first use. The inventive gas generators preferably further comprises a starting mechanism that isolates the solid fuel from the liquid fuel or vice versa before the first use. In one embodiment, the starting mechanism further comprises a catalyst shield mechanism that isolates the catalyst in the reactor or buoy from the liquid and/or the solid fuel prior to the first use.