The effort to produce aconvenient hydrogen storage medium has been ongoing now for generations and I findit difficult to get too excited. I alsofind it difficult to get excited generally about hydrogen because we lackeffective storage.
Here is another solid effortshowing some success. At least they havesomething not needing excessive temperature work. Again it appears promising and we will waitand see were this goes.
Actual storage capacity is notunderstood here as yet.
New material designed for hydrogen storage
By BenCoxworth
13:49 March 15, 2011
Scientists from the U.S. Department of Energy's Lawrence BerkeleyNational Laboratory have created a composite material that they claim can storehydrogen densely and safely, yet that also allows it to be easily accessed forcreating electricity. Some materials that are currently used for hydrogenstorage have a relatively small capacity, and need to be superheatedor supercooled in order to work at peak efficiency. The new material, however,is said not to have either of these limitations.
The Berkeley Lab researcherscreated the pliable nanocomposite from a matrix of polymethyl methacrylate,which is a polymer related to Plexiglas, with nanoparticles of magnesiumsprinkled throughout. It reportedly is able to absorb and release hydrogen at"modest temperatures," without oxidizing the magnesium after cycling.
To confirm that hydrogen was present within the magnesium, theresearchers observed the nanoparticles through the world's most powerfultransmission electron microscope, the TEAM 0.5 – also located at Berkeley Lab.
"This work showcases our ability to design composite nanoscalematerials that overcome fundamental thermodynamic and kinetic barriers torealize a materials combination that has been very elusive historically,"said Jeff Urban, Deputy Director of the Inorganic Nanostructures Facility atBerkeley Lab's Molecular Foundry. "Moreover, we are able to productivelyleverage the unique properties of both the polymer and nanoparticle in this newcomposite material, which may have broad applicability to related problems inother areas of energy research."
The team's findings were recently published in the journal Nature Materials.
Abstract
Hydrogen is a promising alternative energy carrier that canpotentially facilitate the transition from fossil fuels to sources of cleanenergy because of its prominent advantages such as high energy density (142 MJ kg−1;ref. 1),great variety of potential sources (for example water, biomass, organicmatter), light weight, and low environmental impact (water is the solecombustion product). However, there remains a challenge to produce a materialcapable of simultaneously optimizing two conflicting criteria—absorbing hydrogen stronglyenough to form a stable thermodynamic state, but weakly enough to release iton-demand with a small temperature rise. Many materials under development,including metal–organic frameworks2,nanoporous polymers3,and other carbon-based materials4,physisorb only a small amount of hydrogen (typically 1–2 wt%) at roomtemperature. Metal hydrides were traditionally thought to be unsuitablematerials because of their high bond formation enthalpies (for example MgH2 hasa ΔHf∼75 kJ mol−1), thus requiring unacceptably high release temperatures5 resultingin low energy efficiency. However, recent theoretical calculations6, 7 andmetal-catalysed thin-film studies8 haveshown that microstructuring of these materials can enhance the kinetics bydecreasing diffusion path lengths for hydrogen and decreasing therequired thickness of the poorly permeable hydride layer that forms duringabsorption. Here, we report the synthesis of an air-stable composite materialthat consists of metallic Mgnanocrystals (NCs) in a gas-barrier polymermatrix that enables both the storage of a high density of hydrogen(up to 6 wt%of Mg, 4 wt% for the composite) and rapid kinetics (loading in <30 minat 200 °C). Moreover, nanostructuring of the Mg provides rapid storagekinetics without using expensive heavy-metal catalysts.
No comments:
Post a Comment