Hydrogen Storage Materials

On-board Hydrogen storage is the bottleneck for vehicle application s . In order to achieve the FreedomCar targets in 2010 proposed by DOE, the gravimetric hydrogen density should be ~ 6 mass%, and be able to be operated at ambient conditions (< 373 K and 2 atm). It has been demonstrated that the safest way to store hydrogen is solid state material. Currently, there are three types of materials that have shown promise for hydrogen storage: metal hydrides, carbon based materials such as carbon nanotubes, and complex hydrides. Although some of the metal hydrides, such as MgH2, have very high gravimetric hydrogen density, they usually have high activation temperatures and release hydrogen slowly. Carbon nanostructures have low gravimetric hydrogen storage density (~ 2 mass%), and are not suitable for on-board application. Recent advances in complex hydrides, especially catalyzed NaAlH4, have shown the reversible adsorption and desorption of up to 4.2 mass% hydrogen at 180 degree C, and have stimulated a lot of research.

In order to improve the properties of hydrogen storage materials, there are two general methodologies: finding novel materials, especially complex hydrides, or to tailor the microstructures of existing storage materials, especially into nanostructures. We are interested in the latter .