Berkeley Lab team develops new high-performance solid-state H2 storage material: graphene oxide (GO)/Mg nanocrystal hybrid
Researchers at Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a new, environmentally stable solid-state hydrogen storage material constructed of Mg nanocrystals encapsulated by atomically thin and gas-selective reduced graphene oxide (rGO) sheets.
This material, protected from oxygen and moisture by the rGO layers, exhibits dense hydrogen storage (6.5 wt% and 0.105 kg H2 per liter in the total composite). As rGO is atomically thin, this approach minimizes inactive mass in the composite, while also providing a kinetic enhancement to hydrogen sorption performance.
These multilaminates of rGO-Mg are able to deliver exceptionally dense hydrogen storage and provide a material platform for harnessing the attributes of sensitive nanomaterials in demanding environments. An open-access paper on the work is published in the journal Nature Communications.
Hydrogen is the ultimate carbon-free energy carrier—it possesses the highest energy density among chemical fuels and water is the sole combustion product. Although major car manufacturers have made commitments to hydrogen as a ‘fuel of the future’, hydrogen storage for FCEVs (fuel cell electric vehicles) currently relies on compressed gas tanks. These are unable to meet long-term storage targets and severely compromise on-board occupancy.
Metal hydrides for solid-state hydrogen storage are one of the few materials capable of providing sufficient storage density required to meet these long-term targets. However, simultaneously meeting gravimetric, volumetric, thermodynamic and kinetic requirements has proven challenging, owing to the strong binding enthalpies for the metal hydride bonds, long diffusion path lengths and oxidative instability of zero-valent metals. Although nanostructuring has been shown to optimize binding enthalpies3, synthesis and oxidative stabilization of metallic nanocrystals remains a challenge. Protection strategies against oxidization and sintering of nanocrystals often involve embedding these crystals in dense matrices, which add considerable ‘dead’ mass to the composite, in turn decreasing gravimetric and volumetric density. Thus, although metal hydrides show the most promise for non-cryogenic applications, it remains true that no single material has met all of these essential criteria.
Here we demonstrate mixed dimensional reduced graphene oxide (GO)/Mg nanocrystal hybrids as a novel high-performance materials platform for solid-state hydrogen storage.—Cho et al.
These graphene-encapsulated magnesium crystals act as “sponges” for hydrogen, offering a very compact and safe way to take in and store hydrogen. The nanocrystals also permit faster fueling, and reduce the overall “tank” size.
The graphene shields the nanocrystals from oxygen and moisture and contaminants, while tiny, natural holes allow the smaller hydrogen molecules to pass through. This filtering process overcomes common problems degrading the performance of metal hydrides for hydrogen storage.
Among metal hydride-based materials for hydrogen storage for fuel-cell vehicle applications, our materials have good performance in terms of capacity, reversibility, kinetics and stability.—Eun Seon Cho, postdoc at Berkeley Lab and lead author
The research, conducted at Berkeley Lab’s Molecular Foundry and Advanced Light Source, is part of a National Lab Consortium, dubbed HyMARC (Hydrogen Materials—Advanced Research Consortium) (earlier post) that seeks safer and more cost-effective hydrogen storage.
Co-author Jeff Urban, a Berkeley Lab staff scientist, is Berkeley Lab’s lead scientist for HyMARC.
This work suggests the possibility of practical hydrogen storage and use in the future. I believe that these materials represent a generally applicable approach to stabilizing reactive materials while still harnessing their unique activity—concepts that could have wide-ranging applications for batteries, catalysis, and energetic materials.—Jeff Urban
The work was supported by the Department of Energy Office of Basic Energy Sciences and Office of Energy Efficiency and Renewable Energy, the Bay Area Photovoltaic Consortium (BAPVC), and the US-India Partnership to Advance Clean Energy-Research (PACE-R) for the Solar Energy Research Institute for India and the US (SERIIUS).
Eun Seon Cho, Anne M. Ruminski, Shaul Aloni, Yi-Sheng Liu, Jinghua Guo & Jeffrey J. Urban (2016) “Graphene oxide/metal nanocrystal multilaminates as the atomic limit for safe and selective hydrogen storage” Nature Communications 7, Article number: 10804 doi: 10.1038/ncomms10804