H₂ Storage in Molecular Compounds

Increasing worldwide energy consumption, exhaustion of fossil fuel resources and global environmental and ecological problems have provoked intensive searches for future clean energy resources. Hydrogen is postulated to be one of the best alternative fuels to gasoline for future transportation systems. Developing prototype cars powered by hydrogen fuel cells (see below) is an area of high interest to American industry. The key scientific challenge is to develop hydrogen storage materials with high gravimetric and volumetric hydrogen densities. Current materials such as liquid hydrogen, which requires massive gas cylinders, metal hydrides, which are difficult to regenerate, and ammonia borane, which suffer problems in absorption/desorption reversibility, suffer from issues that limit their widespread applicability as H₂ storage media.

Relative Storage Capacities of H₂ Storage Media

Inclusion compounds represent a class of H₂ storage materials where significant 'quantum' increases in storage capacity (> 50% over existing levels) may be possible while maintaining good reversibility, favorable kinetics, and usable P-T conditions. LANL researchers have made several significant contributions to the development and understanding of H₂-clathrate and MOFs (see papers on the publication list). One of the most important observations is that the H₂-H₂ bond distances within the cages of H₂ clathrate are shorter than those in solid hydrogen! This demonstrates a pressurization/squeezing effect within the cage structure of the clathrate. Neutron diffraction results have demonstrated temperature-dependent localization/delocalization behavior within the large cage of H₂ clathrate.

Top - Relative Bond Lengths Between H₂ Clathrate & Solid H₂
Middle - Neutron Diffraction Results - H₂ Clathrate
Bottom - H₂ Localization/delocalization Behavior in H₂ Clathrate & H₂ Site Occupancies as a Function of T

LANL researchers have also taken this research 'out of the lab' recently having been granted a patent for new method for the fast-synthesis of H₂ clathrate.

Patented LANL H₂ Clathrate Synthesis Method from Ice Speeds Reaction Times