Sharing All of The World

Sandia-induced changes elevate the plentiful, 37-cents-a-gram molly from being a welterweight outsider in the energy-catalyst field -- put crudely, a lazy bum that never amounted to much -- to a possible contender with the heavyweight champ.
The improved catalyst, expected to be the subject of an Oct. 7 Nature Communications paper, has already released four times the amount of hydrogen ever produced by molly from water.
To Sandia postdoctoral fellow and lead author Stan Chou, this is just the beginning: "We should get far more output as we learn to better integrate molly with, for example, fuel-cell systems," he said.
An additional benefit is that molly's action can be triggered by sunlight, a feature which eventually may provide users an off-the-grid means of securing hydrogen fuel.
Hydrogen fuel is desirable because, unlike gasoline, it doesn't release carbon into the atmosphere when burned. The combustion of hydrogen with oxygen produces an exhaust of only water.
In Chou's measured words, "The idea was to understand the changes in the molecular structure of molybdenum disulfide (MOS?), so that it can be a better catalyst for hydrogen production: closer to platinum in efficiency, but earth-abundant and cheap. We did this by investigating the structural transformations of MOS? at the atomic scale, so that all of the materials parts that were 'dead' can now work to make H? [hydrogen]."
The rind of an orange
in what sense were the parts "dead," one might ask?
Visualize an orange slice where only the rind of the orange is useful; the rest -- the edible bulk of the orange -- must be thrown away. Molly exists as a stack of flat nanostructures, like a pile of orange slices. These layers are not molecularly bolted together like a metal but instead are loose enough to slide over one another -- a kind of grease, similar to the structure of graphene, and with huge internal surface areas.
But here's the rub: While the edges of these nanostructures match platinum in their ability to catalyze hydrogen, the relative immense surface area of their sliding interiors are useless because their molecular arrangements are different from their edges. Because of this excess baggage, a commercial catalyst would require a huge amount of molly. The slender edges would work hard like Cinderella, but the stepsister interiors would just hang out, doing nothing.
Chou, who works on two-dimensional materials and their properties, thought the intent should be to get these stepsisters jobs.
Empowering the center
"There are many ways to do this," said co-author Bryan Kaehr, "but the most scalable way is to separate the nanosheets in solution using lithium. With this method, as you pull the material apart, its molecular lattice changes into different forms; the end product, as it turns out, is catalytically active like the edge structure."
To determine what was happening, and the best way to make it happen, the Sandia team used computer simulations generated by coauthor Na Sai from the University of Texas at Austin that suggested which molecular changes to look for. The team also observed changes with the most advanced microscopes at Sandia. including the FEI Titan, an aberration-corrected transmission electron microscope able to view atoms normally too small to see on most scopes.
"The extended test period made possible by the combined skills of our group allowed the reactions to be observed with the amount of detail needed," said Chou.
Lacking these tools, researchers at other labs had ended their tests before the reaction could complete itself, like a cook taking sugar and water off the stove before syrup is produced, resulting in a variety of conflicting intermediate results.
Ending confusion
"Why Stan's work is impactful is that there was so much confusion as to how this process works and what structures are actually formed," said Kaehr. "He unambiguously showed that this desirable catalytic form is the end result of the completed reaction."
Said Sandia Fellow and University of New Mexico professor Jeff Brinker, another paper author, "People want a non-platinum catalyst. Molly is dirt cheap and abundant. By making these relatively enormous surface areas catalytically active, Stan established understanding of the structural relation of these two-dimensional materials that will determine how they will be used in the long run. You have to basically understand the material before you can move forward in changing industrial use."
Kaehr cautions that what's been established is a fundamental proof of principle, not an industrial process. "Water splitting is a challenging reaction. It can be poisoned, stopping the molly reaction after some time period. Then you can restart it with acid. There are many intricacies to be worked out.
"But getting inexpensive molly to work this much more efficiently could drive hydrogen production costs way down."
'Green' inorganic photosynthesis
Not requiring electricity to prompt the reaction may be convenient in some circumstances and also keep costs down.
"A molly catalyst is essentially a 'green' technology," said Chou. "We used sunlight for the experiment's motive power. The light is processed through a dye, which harvests the light. A photocatalytic process stores that energy in the chemical bonds of the liberated hydrogen molecule.
"It's a kind of photosynthesis, but using inorganic materials rather than plants," Chou continued. "Plants use enzymes powered by sunlight to break up water into hydrogen and oxygen in a delicate process. We're proposing a similar thing here, but in a more rapid reaction and with sturdier components."
Kaehr said, "You could generate hydrogen and use it whenever. Hydrogen doesn't lose charge over time or suffer from conversion inefficiencies as do batteries in a solar car."
Other paper authors were Ping Lu, Eric Coker, Sheng Liu and Ting Luk, all from Sandia Labs, and Kateryna Artyushkova from the University of New Mexico.
The work was supported by the Department of Energy's Office of Science, and through its user facilities at the Sandia/Los Alamos-run Center for Integrated Nanotechnologies and National Energy Research Scientific Computing Center. The Texas Advanced Computing Center also added value.

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The above post is reprinted from materials provided by DOE/Sandia National Laboratories. Note: Materials may be edited for content and length.

"The material created by us is considerably cheaper and the process of its synthesis is less complicated than that of the currently used analogue material. Also, both materials have very similar efficiency of converting solar energy into electricity. That means that our semiconductors have similar characteristics to the known alternatives, but are much cheaper," says professor Vytautas Getautis, head of the chemistry research group responsible for the discovery.
The solar cells containing organic semiconductors created at KTU were constructed and tested by physicists at Lausanne. The tests revealed outstanding results: the effectivity of the cells' converting solar energy into electricity was 16.9 percent. There are only a few organic semiconductors in the world affording such a high solar cell efficiency.
Prof Getautis says that the material created at KTU will be used in the construction of future solar cells: almost all solar cells are made from inorganic semiconductors. Hybrid, semi-organic solar cells are still being developed and perfected at the research centres all over the world.
KTU and Swiss Federal Institute of Technology Lausanne registered the invention at the European Patent Office.
The work was featured in Angewandte Chemie International Edition.

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The above post is reprinted from materials provided by Kaunas University of Technology (KTU). Note: Materials may be edited for content and length.

"This work means there's an opportunity to use composite metal foam to develop safer systems for transporting nuclear waste, more efficient designs for spacecraft and nuclear structures, and new shielding for use in CT scanners," says Afsaneh Rabiei, a professor of mechanical and aerospace engineering at NC State and corresponding author of a paper on the work.
Rabiei first developed the strong, lightweight metal foam for use in transportation and military applications. But she wanted to determine whether the foam could be used for nuclear or space exploration applications -- could it provide structural support, protect against high impacts and provide shielding against various forms of radiation?
To that end, she and her colleagues conducted multiple tests to see how effective it was at blocking X-rays, gamma rays and neutron radiation. She then compared the material's performance to the performance of bulk materials that are currently used in shielding applications. The comparison was made using samples of the same "areal" density -- meaning that each sample had the same weight, but varied in volume.
The most effective composite metal foam against all three forms of radiation is called "high-Z steel-steel" and was made up largely of stainless steel, but incorporated a small amount of tungsten. However, the structure of the high-Z foam was modified so that the composite foam that included tungsten was not denser than metal foam made entirely of stainless steel.
The researchers tested shielding performance against several kinds of gamma ray radiation. Different source materials produce gamma rays with different energies. For example, cesium and cobalt emit higher-energy gamma rays, while barium and americium emit lower-energy gamma rays.
The researchers found that the high-Z foam was comparable to bulk materials at blocking high-energy gamma rays, but was much better than bulk materials -- even bulk steel -- at blocking low-energy gamma rays.
Similarly, the high-Z foam outperformed other materials at blocking neutron radiation.
The high-Z foam performed better than most materials at blocking X-rays, but was not quite as effective as lead.
"However, we are working to modify the composition of the metal foam to be even more effective than lead at blocking X-rays -- and our early results are promising," Rabiei says. "And our foams have the advantage of being non-toxic, which means that they are easier to manufacture and recycle. In addition, the extraordinary mechanical and thermal properties of composite metal foams, and their energy absorption capabilities, make the material a good candidate for various nuclear structural applications."
The paper, "Attenuation efficiency of X-ray and comparison to gamma ray and neutrons in composite metal foams," is published in Radiation Physics and Chemistry. Lead author is Shuo Chen, a recent Ph.D. graduate at NC State. The paper was co-authored by Mohamed Bourham, a professor of nuclear engineering at NC State. The work was supported by DOE's Office of Nuclear Energy under Nuclear Energy University Program grant number CFP-11-1643.

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The above post is reprinted from materials provided by North Carolina State University. The original item was written by Afsaneh Rabiei. Note: Materials may be edited for content and length.