storage including complex borohydrides, or aluminohydrides, and ammonium salts. These hydrides have an upper theoretical hydrogen yield limited to about 8.5% by weight. Amongst the compounds that contain only B, N, and H (both positive and negative ions), representative examples include: amine boranes, boron hydride ammoniates, hydrazine-borane complexes, and ammonium octahydrotriborates or tetrahydroborates. Of these, amine boranes (and especially ammonia borane) have been extensively investigated as hydrogen carriers. During the 1970s and 1980s, the U.S. Army and Navy funded efforts aimed at developing hydrogen/deuterium gas-generating compounds for use in the HF/DF and HCl chemical lasers, and gas dynamic lasers. Earlier hydrogen gas-generating formulations used amine boranes and their derivatives. Ignition of the amine borane(s) forms boron nitride (BN) and hydrogen gas. In addition to ammonia borane (H3BNH3), other gas-generators include diborane diammoniate, H2B(NH3)2BH4. Physical storage In this case hydrogen remains in physical forms, i.e., as gas, supercritical fluid, adsorbate, or molecular inclusions. Theoretical limitations and experimental results are considered concerning the volumetric and gravimetric capacity of glass microvessels, microporous, and nanoporous media, as well as safety and refilling-time demands. Zeolites Zeolites are microporous and highly crystalline aluminosilicate materials. As they exhibit cage and tunnel structures, they offer the potential for the encapsulation of non-polar gases such as H2. In this system, hydrogen is physisorbed on the surface of the zeolite pores through a mechanism of adsorption that involves hydrogen being forced into the pores under pressure and low temperature. Therefore, similar to other porous materials, its hydrogen storage capacity depends on the BET surface area, pore volume, the interaction of molecular hydrogen with the internal surfaces of the micropores, and working conditions such as pressure and temperature. Research shows that the channel diameter is also one of the parameters determining this capacity, especially at high pressure. In this case, an effective material should exhibit a large pore volume and a channel diameter close to the kinetic diameter of the hydrogen molecule (dH=2.89 Å). Table below shows the hydrogen uptake of several zeolites at liquid nitrogen temperature (77K): Porous or layered carbon Activated carbons are highly porous amorphous carbon materials with high apparent surface area. Hydrogen physisorption can be increased in these materials by increasing the apparent surface area and optimizing pore diameter to around 7 Å. These materials are of particular interest due to the fact that they can be made from waste materials, such as cigarette butts which have