Carbon Nanotube Materials for Hydrogen Storage

Although hydrogen provides more energy than either gasoline or natural gas on a weight basis, its drawbacks for vehicular use become apparent when the weight, volume, and round-trip energy costs of a hydrogen fuel storage system are considered. New approaches enabling more compact, lightweight, and energy efficient hydrogen storage are required in order for the wide-spread use of hydrogen poweredvehicles to become a reality. Although several hydrogen storage options exist, no approach satisfies all of the efficiency, size, weight, cost and safety requirements for transportation use. We have shown in previous work that carbon single-wall nanotubes (SWNTs) are essentially elongated pores of molecular dimensions and are capable of stabilizing hydrogen at relatively high temperatures andlow pressures by adsorption. This behavior is unique to these materials and indicates the SWNTs are the ideal building block for constructing safe, efficient, and high energy density adsorbents for hydrogen storage applications. In past work we developed these new materials. During this year we have made additional significant progress in manipulating and understanding the behavior of SWNTs sothat high performance adsorbents may be fabricated in a cost effective manner. Specifically, we have verified that hydrogen is stablilized by physical rather than chemical interactions, measured the strength of interaction to be approx. 5 times higher than for adsorption on planar graphite, performed infrared adsorption spectroscopy to determine the chemical nature of the surface terminationsbefore, during, and after oxidation, and developed laser-based methods for the high-yield synthesis of these important new materials.