  Hydrogen can be stored in containers or in materials. In materials it can
exist in molecular or atomic forms. The atomic form can further exist as
multiple phases. Molecular hydrogen can be adsorbed on the surface or can be
present inside the material. In the current work, we demonstrate for the first
time, a methodology to store hydrogen in nearly all conceivable forms. At the
heart of this strategy is the novel concept of storage of molecular hydrogen in
metal Pd nanocontainers. The existence of multiple phases of hydrogen is
confirmed by x ray diffraction, Raman spectroscopy, nuclear magnetic resonance
and pressure-composition isotherm measurements. Enhancement in storage capacity
as compared to nanocrystals of the same mass is observed (36 percent increase
at 1 atm and 25C). About 18 percent of the hydrogen stored is in the molecular
form and interestingly this is achieved at room temperature and 1 atm pressure.
