Creating power from water

March 25, 2011 by Katie Gatto

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Image credit: J. Am. Chem. Soc., 2009, 131 (11), pp 3838-3839. DOI: 10.1021/ja900023k

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(PhysOrg.com) -- Creating power from water. I bet when I say that you picture a damn or a large turbine being pushed by hundreds of thousands of gallons of water, all rushing at tremendous speeds. It is a cool, and accurate, image of how most power comes from water. That is not to say that it is the only way that power can come from water.

Researchers at the The Tata Group have been working with Daniel Nocera, an MIT scientist and founder of SunCatalytix, have found a new way to coax power out of water. If you're wondering how that was accomplished here are the basics.

The research team placed an artificial sheet of artificial cobalt- and phosphate-coated silicon into a jar of water. This produced an effect similar to photosynthesis. The splitting of hydrogen from water was used to generate power from the sun. Interestingly enough, this technique was able to produce more power than the current generation of solar panels.

This technology, which can be used with gray water, could be used to power a mini power plant, that would be about the size of a refrigerator, according to the researchers. Of course, those plans could change, since this research is really only it its early stages. By next year the team expects to be able to power a small home with only roughly a bottle and a half of water. While specifics of the deal have not been made public at this time, The Tata Group's mission is to bring basic needs and other essential resources to low-income peoples, and the best guess is that this technology will involve that market.

More information: http://www.suncatalytix.com/tech.html

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Helping Hydrogen: Student Inventor Tackles Challenge of Hydrogen Storage

Listen to a podcast interview with Lemelson-MIT Rensselaer Student Prize-Winner Javad Rafiee.

$30,000 Lemelson-MIT Collegiate Student Prizes Awarded to Inventive Students Nationwide; Four Leading Institutes Celebrate 2010 Winners

Determined to play a key role in solving global dependency on fossil fuels, Javad Rafiee, a doctoral student in the Department of Mechanical, Aerospace, and Nuclear Engineering at Rensselaer Polytechnic Institute, has developed a new method for storing hydrogen at room temperature.

Rafiee has created a novel form of engineered graphene that exhibits hydrogen storing capacity far exceeding any other known material. For this innovation, which brings the world a step closer to realizing the widespread adoption of clean, abundant hydrogen as a fuel for transportation vehicles, Rafiee is the winner of the 2010 $30,000 Lemelson-MIT Rensselaer Student Prize. He is among the four 2010 $30,000 Lemelson-MIT Collegiate Student Prize winners announced today.

“Invention is the key ingredient of progress, and the Lemelson-MIT Rensselaer Student Prize rallies our students to innovate world-changing solutions for the grand challenges facing all people of all nations,” said Rensselaer President Shirley Ann Jackson. “Javad Rafiee has the vision of a robust national hydrogen economy and a world less dependent on oil and gasoline. I applaud his efforts toward this noble goal, and congratulate him on this prestigious award. I thank all of the Lemelson-MIT Rensselaer Collegiate Student Prize winners and finalists for their effort, zeal, and for being ambassadors of progress.”

Rafiee is the fourth recipient of the Lemelson-MIT Rensselaer Student Prize. The prize, first given in 2007, is awarded annually to a Rensselaer senior or graduate student who has created or improved a product or process, applied a technology in a new way, redesigned a system, or demonstrated remarkable inventiveness in other ways.

"This year’s winners from the Massachusetts Institute of Technology, California Institute of Technology, Rensselaer Polytechnic Institute, and University of Illinois at Urbana-Champaign shine light on the significance of collegiate invention. They have the ability to transform seemingly implausible ideas into reality and are the true entrepreneurial leaders of their generation,” said Joshua Schuler, executive director of the Lemelson-MIT Program.

For videos and photos of the winner and award finalists, as well as a Webcast of the announcement ceremony, please visit: www.eng.rpi.edu/lemelson.

Enabling Greener Transportation with Graphene
Hydrogen storage has proven to be a significant bottleneck to the advancement and proliferation of fuel cell and hydrogen technologies in cars, trucks, and other applications. Rafiee has developed a new method for manufacturing and using graphene, an atom-thick sheet of carbon atoms arranged like a nanoscale chain-link fence, to store hydrogen. His solution is inexpensive and easy to produce.

With adviser and Rensselaer Professor Nikhil Koratkar, Rafiee used a combination of mechanical grinding, plasma treatment, and annealing to engineer the atomic structure of graphene to maximize its hydrogen storage capacity. This new graphene has exhibited a hydrogen storage capacity of 14 percent by weight at room temperature – far exceeding any other known material.

This 14-percent capacity surpasses the U.S. Department of Energy 2015 target of realizing a material with hydrogen storage capacity of 9 percent by weight at room temperature. Rafiee said his graphene is also one of the first known materials to surpass the Department of Energy’s 2010 target of 6 percent.

Rafiee’s graphene exhibits three critical attributes that result in its unique hydrogen storage capacity. The first is high surface area. Graphene’s unique structure, only one atom thick, means that each of its carbon atoms is exposed to the environment and, in turn, to the hydrogen gas. The second attribute is low density. Graphene has one of the highest surface area-per-unit masses in nature, far superior to even carbon nanotubes and fullerenes.

The third attribute is favorable surface chemistry. After oxidizing graphite powder and mechanically grinding the resulting graphite oxide, Rafiee synthesized the graphene by thermal shock followed by annealing and exposure to argon plasma. These treatments play an important role in increasing the binding energy of hydrogen to the graphene surface at room temperature, as hydrogen tends to cluster and layer around carbon atoms.

Talented Engineer
Rafiee joined Rensselaer in 2008, following an internship at the City University of Hong Kong and earning his bachelor’s and master’s degrees in mechanical and manufacturing engineering from the University of Tabriz in Iran. At Rensselaer, Rafiee and his brother, Mohammad, joined the research group of Mechanical, Aerospace, and Nuclear Engineering Professor Nikhil Koratkar.

“Javad is extremely knowledgeable, has great confidence in his abilities, and has demonstrated a very high level of creativity and originality. However, it is his deep passion and enthusiasm for research and discovery coupled with his amazing drive and energy that differentiates him from his peers,” Koratkar said. “This passion and excitement for discovery and innovation is not something that can be taught or learned. It is an intrinsic quality of an individual – either you have it or you don’t — and Javad is the most intellectually curious student I have ever had the privilege to advise here at Rensselaer.”

In his time at Rensselaer, Rafiee has authored five, and co-authored three, journal papers in various disciplines, ranging from materials science and mechanical engineering, to computer science and urology.

Rafiee is from Tehran, Iran, and expects to earn his doctorate in 2011. Following graduation, he and his brother plan to start their own business with a focus on clean energy and green manufacturing.

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Silicon nanotubes could exceed their carbon counterparts in hydrogen storage efficiency

Posted: April 21, 2008

(Nanowerk Spotlight) Safe, efficient and compact hydrogen storage is a major challenge in order to realize hydrogen powered transport. According to the U.S. Department of Energy's Freedom CAR program roadmap, the on-board hydrogen storage system should provide a gravimetric density of 6 wt% at room temperature to be considered for technological implementation. Currently, the storage of hydrogen in the absorbed form is considered as the most appropriate way to solve this problem. Research groups worldwide are seeking and experimenting with materials capable of absorbing and releasing large quantities of hydrogen easily, reliably, and safely. One candidate material that is being considered as a candidate for hydrogen storage media is single-walled carbon nanotubes (SWCNT).

So far, carbon nanotubes have been unable to meet the DOE's hydrogen storage target. This even has led to a decision by the DOE to discontinue future applied research and development investment in pure, undoped SWCNTs for vehicular hydrogen storage applications. Although most of the previous studies have focused on hydrogen storage through physisorption, recent Density Functional Theory calculations for SWCNT indicate the potential for up to 7.5 wt% hydrogen storage capacity for this material through chemisorption (see our Spotlight: "New carbon nanotube hydrogen storage results surpass Freedom Car requirements").

New theoretical work from China suggests that silicon nanotubes can store hydrogen more efficiently than their carbon nanotube counterparts. This raises the possibility that, after powering the micro-electronics revolution, silicon could also become a key material for the future hydrogen economy.

"Compared to carbon, silicon has more electrons in the outer shells, which leads to higher polarizability and a stronger dispersion force" Dr. Dapeng Cao explains to Nanowerk. "Motivated by this observation, we employ a multiscale theoretical method, which combines the first-principle calculation and a grand canonical Monte Carlo simulation, to predict the adsorption capacity of hydrogen in silicon nanotube (SiNT) arrays at a temperature of 298°K (25°C) and pressure range from 1 to 10 MPa. Our calculations show that silicon nanotubes can adsorb hydrogen molecules more efficiently than carbon nanotubes under normal fuel cell operating conditions."

Cao, is a professor and vice director of the Lab of Molecular and Materials Simulation at the Beijing University of Chemical Technology. Together with other members of the Lab he published their recent findings in the March 19, 2008 online edition of The Journal of Physical Chemistry (Silicon Nanotube as a Promising Candidate for Hydrogen Storage: From the First Principle Calculations to Grand Canonical Monte Carlo Simulations).

Left: Schematic representations of a (5,5) SiNT cluster model, where all the terminals are saturated with H atoms and the brown yellow and gray spheres represent Si and H atoms, respectively. Right: Gravimetric adsorption capacity of hydrogen in the rhombic SiNT array at T=298°K and P=10 MPa, resulting in 2.88 wt%. A comparative simulation with CNTs results in gravimetric density of 1.96 wt%. (Images: Dr. Cao)

Following the successful synthesis of silicon nanotubes by the chemical vapor deposition method in 2002, researchers developed numerous other methods to fabricate these SiNTs and well-aligned SiNT arrays. Because silicon has more electrons in the outer shells than carbon – which leads to higher polarizability and a stronger dispersion force – scientists theorized that SiNTs may exhibit a stronger van der Waals attraction to hydrogen than CNTs.

"Our multiscale theoretical method combines the first-principle calculations to obtain the binding energy between hydrogen and the SiNT and a grand canonical Monte Carlo simulation to evaluate the hydrogen adsorption capacity in the SiNT arrays, where the calculated binding energy is provided as an input in the Monte Carlo simulation" Cao explains.

The researchers found that geometrical arrangement of the tubes as well as the diameter and curvature of the tube affect the adsorption of hydrogen in the SiNT array.

Since SiNTs are a novel material, there is no experimental data available yet with regard to their hydrogen storage capability. Experimental work needs to be conducted to confirm this theoretical findings. Cao points out that the separation between silicon nanotubes affects the capacity of hydrogen storage significantly. Therefore one of the challenges for conducting practical experiments will be control of the optimal separation between SiNTs in the preparation of well-aligned arrays.

By Michael Berger. Copyright 2008 Nanowerk LLC Source

Tiny buckyballs squeeze hydrogen like giant Jupiter

3/23/2008 12:13:21 PM

Hydrogen could be a clean, abundant energy source, but it's difficult to store in bulk. In new research, materials scientists at Rice University have made the surprising discovery that tiny carbon capsules called buckyballs are so strong they can hold volumes of hydrogen nearly as dense as those at the center of Jupiter.

The research appears on the March 2008 cover of the American Chemical Society's journal Nano Letters.

"Based on our calculations, it appears that some buckyballs are capable of holding volumes of hydrogen so dense as to be almost metallic," said lead researcher Boris Yakobson, professor of mechanical engineering and materials science at Rice. "It appears they can hold about 8 percent of their weight in hydrogen at room temperature, which is considerably better than the federal target of 6 percent."

The Department of Energy has devoted more than $1 billion to developing technologies for hydrogen-powered automobiles, including technologies to cost-effectively store hydrogen for use in cars. Hydrogen is the lightest element in the universe, and it is very difficult to store in bulk. For hydrogen cars to be competitive with gasoline-powered cars, they need a comparable range and a reasonably compact fuel system. It's estimated that a hydrogen-powered car with a suitable range will require a storage system with densities greater than those found in pure, liquid hydrogen.

Yakobson said scientists have long argued the merits of storing hydrogen in tiny, molecular containers like buckyballs, and experiments have shown that it's possible to store small volumes of hydrogen inside buckyballs. The new research by Yakobson and former postdoctoral researchers Olga Pupysheva and Amir Farajian offers the first method of precisely calculating how much hydrogen a buckyball can hold before breaking.

Buckyballs, which were discovered at Rice more than 20 years ago, are part of a family of carbon molecules called fullerenes. The family includes carbon nanotubes, the typical 60-atom buckyball and larger buckyballs composed of 2,000 or more atoms.

"Bonds between carbon atoms are among the strongest chemical bonds in nature," Yakobson said. "These bonds are what make diamond the hardest known substance, and our research showed that it takes an enormous amount of internal pressure to deform and break the carbon-carbon bonds in a fullerene."

Using a computer model, Yakobson's research team has tracked the strength of each atomic bond in a buckyball and simulated what happened to the bonds as more hydrogen atoms were packed inside. Yakobson said the model promises to be particularly useful because it is scalable, that is it can calculate exactly how much hydrogen a buckyball of any given size can hold, and it can also tell scientists how overstuffed buckyballs burst open and release their cargo.

If a feasible way to produce hydrogen-filled buckyballs is developed, Yakobson said, it might be possible to store them as a powder.

"They will likely assemble into weak molecular crystals or form a thin powder," he said. "They might find use in their whole form or be punctured under certain conditions to release pure hydrogen for fuel cells or other types of engines."

The research was supported by the Office of Naval Research and the Department of Energy.

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