This schematic shows high-capacity magnesium nanocrystals encapsulated in a gas-barrier polymer matrix to create a new and revolutionary hydrogen storage composite material. Credit: Image from Jeff Urban |
Since the 1970s, hydrogen has been touted as a
promising alternative to fossil fuels due to its clean combustion—unlike
hydrocarbon-based fuels, which spew greenhouse gases and harmful pollutants,
hydrogen’s only combustion by-product is water. Compared to gasoline, hydrogen
is lightweight, can provide a higher energy density, and is readily available.
But there’s a reason we’re not already living in a hydrogen economy: to replace
gasoline as a fuel, hydrogen must be safely and densely stored, yet easily accessed.
Limited by materials unable to leap these conflicting hurdles, hydrogen storage
technology has lagged behind other clean energy candidates.
In recent years, researchers have attempted to
tackle both issues by locking hydrogen into solids, packing larger quantities
into smaller volumes with low reactivity—a necessity in keeping this volatile
gas stable. However, most of these solids can only absorb a small amount of
hydrogen and require extreme heating or cooling to boost their overall energy
efficiency.
Now, scientists with the U.S. Department of Energy
(DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) have designed a new
composite material for hydrogen storage consisting of nanoparticles of
magnesium metal sprinkled through a matrix of polymethyl methacrylate. This
pliable nanocomposite rapidly absorbs and releases hydrogen at modest
temperatures without oxidizing the metal after cycling—a breakthrough in
materials design for hydrogen storage, batteries, and fuel cells.
“This work showcases our ability to design
composite nanoscale materials that overcome fundamental thermodynamic and
kinetic barriers to realize a materials combination that has been very elusive
historically,” says Jeff Urban, Deputy Director of the Inorganic
Nanostructures Facility at the Molecular Foundry, a DOE Office of Science
nanoscience center and national user facility located at Berkeley Lab.
“Moreover, we are able to productively leverage the unique properties of
both the polymer and nanoparticle in this new composite material, which may
have broad applicability to related problems in other areas of energy
research.”
Transmission electron micrographs of an air-stable composite comprised of metallic magnesium nanocrystals in a gas-barrier polymer matrix that enables the high density storage and rapid release of hydrogen without the need for heavy, expensive metal catalysts. Credit: Images from National Center for Electron Microscopy |
Urban, along with coauthors Ki-Joon Jeon and
Christian Kisielowski used the TEAM 0.5 microscope to observe individual
magnesium nanocrystals dispersed throughout the polymer. With the
high-resolution imaging capabilities of TEAM 0.5, the researchers were also
able to track defects—atomic vacancies in an otherwise-ordered crystalline framework—providing
insight into the behavior of hydrogen within this new class of storage
materials.
“Discovering new materials that could help us
find a more sustainable energy solution is at the core of the Department of
Energy’s mission. Our lab provides outstanding experiments to support this
mission with great success,” says Kisielowski. “We confirmed the
presence of hydrogen in this material through time-dependent spectroscopic
investigations with the TEAM 0.5 microscope. This investigation suggests that
even direct imaging of hydrogen columns in such materials can be attempted
using the TEAM microscope.”
“The unique nature of Berkeley Lab encourages
cross-division collaborations without any limitations,” said Jeon, now at
the Ulsan National Institute of Science and Technology, whose postdoctoral work
with Urban led to this publication.
To investigate the uptake and release of hydrogen
in their nanocomposite material, the team turned to Berkeley Lab’s Energy and
Environmental Technologies Division (EETD), whose research is aimed at
developing more environmentally friendly technologies for generating and
storing energy, including hydrogen storage.
“Here at EETD, we have been working closely
with industry to maintain a hydrogen storage facility as well as develop
hydrogen storage property testing protocols,” says Samuel Mao, director of
the Clean Energy Laboratory at Berkeley Lab and an adjunct engineering faculty
member at the University of California (UC), Berkeley. “We very much enjoy
this collaboration with Jeff and his team in the Materials Sciences Division,
where they developed and synthesized this new material, and were then able to
use our facility for their hydrogen storage research.”
Adds Urban, “This ambitious science is
uniquely well-positioned to be pursued within the strong collaborative ethos
here at Berkeley Lab. The successes we achieve depend critically upon close
ties between cutting-edge microscopy at NCEM, tools and expertise from EETD,
and the characterization and materials know-how from MSD.”
