Abstract: Disclosed is a method of: providing a hydrogenated sp2 carbon allotrope, and releasing hydrogen gas from the carbon allotrope. The method may be used an apparatus having: a vessel for containing the hydrogenated sp2 carbon allotrope, a fuel cell capable of using hydrogen gas a fuel, and a tube for transporting hydrogen gas from the vessel to the fuel cell. The carbon allotrope may be made by: providing a mixture of an sp2 carbon allotrope and liquid ammonia, adding an alkali metal to the mixture, and sonicating the mixture to form a hydrogenated form of the carbon allotrope. The hydrogenated carbon can be at least 3.5 wt % hydrogen covalently bound to the carbon.