Researchers from the University of Maryland developed a technique to fold graphene squares into a "box", which opens and closes in response to an electric charge. The researchers packed hydrogen atoms into this "box" - and say that this is the most efficient hydrogen storage device ever - with a storage density of 9.5% hydrogen by weight. This outperforms the DoE's goal for 2020 (7.5%).
The researchers are now working to increase the density and say that they have already demonstrated an even higher density. This research was supported by the US NSF.