Molecular Hydrogen Storage in Novel Binary Clathrate Hydrates at Near-Ambient Temperatures and Pressures, excerpt from DOE Hydrogen Program 2006 Progress Report

Program Scope Clathrate hydrates are inclusion compounds in which guest molecules occupy the cages formed by a hydrogen-bonded water network [1]. Solid gas clathrate hydrates generally form at high pressures and temperatures near or even above the ice point. Pure hydrogen hydrates have been reported to form cubic structure II hydrates under extreme conditions (200 MPa at 280 K) [2]. We have recently demonstrated that hydrogen molecules can be stored in binary H2/THF (tetrahydrofuran) clathrate hydrates at pressures nearly two orders of magnitude lower than that in pure hydrogen hydrates [3]. This decreased pressure (Figure 1) makes binary clathrate hydrates a more feasible hydrogen storage material, with a unique combination of advantages not found in any other class of materials. Hydrogen storage is completely reversible is this material, since the gas molecules are free within the clathrate hydrate framework. Determination of a fundamental understanding of the structure, molecularlevel dynamics, and H2 formation/release rates and mechanisms in these novel crystalline compounds is the main objective of our research. The final goal of this project is develop binary clathrate hydrates that will efficiently store and release molecular hydrogen at near-ambient temperatures and pressures, achieving targets for energy density, energy uptake, and release kinetics.