Materials For Energy

Computation, Experiment, and Data Combine to Accelerate the Rate of Developing New, Energy Efficient Materials

By Dr. Russell Chianelli, The University of Texas at El Paso, Materials Research and Technology Institute

In the December issue of MRS Bulletin “Energy Quarterly,” an article by Prachi Patel, “Materials Genome Initiative and Energy,” describes a new approach designed to accelerate the discovery of new energy efficient materials. The Materials Genome Initiative (MGI), a federal program instituted in 2011, is based on a concept called Integrated Computational Materials Engineering (ICME), which combines computational tools, experimental tools, and digital data to accelerate the discovery and design of new energy efficient materials. In this respect, it is similar to the combinatorial chemistry techniques used in the pharmaceuticals industry to accelerate the pace of drug discovery.

Ford Motor Company used a similar process to accelerate the development of materials for more energy efficient automobile engines. This system, virtual aluminum casting, saved Ford a large portion of development costs (25%) for new engine castings. The MGI encourages the development of ICME systems in other areas of materials for energy. This approach is generally applicable and is becoming crucial in the field of research and development for materials for energy.

Materials Needed to Make Wind Work!

By Dr. Russell Chianelli, The University of Texas at El Paso, Materials Research and Technology Institute

In the December issue of “Energy Quarterly” in MRS Bulletin, an article by Phillip Ball entitled “Wind on the Lakes” describes materials challenges for Great Lakes wind energy projects. Wind on the Great Lakes of the United States and Canada has a high potential for producing energy, but so far it has been ignored. One of the advantages of the freshwater Great Lakes is the absence of salt corrosion, which complicates ocean installations. Environmental issues concerning fisheries, birds, and natural habitats are also barriers to be addressed.

Better materials are also needed. This includes better rotor blades, as current plastic materials have problems with stability in the environment and poor mechanical properties. Rare earths are used in many of the energy generating and transmitting processes; finding replacement materials for these increasingly critical elements raises increasing economic and environmental issues. Finally, energy storage of produced electricity is a major sticking point for commercialization of wind energy. These are intriguing challenges for those of us working in materials for energy research.

A Global Energy Perspective

By Dr. Russell Chianelli, University of Texas at El Paso, Materials Research & Technology Institute

The “Energy Quarterly” section in the December issue of MRS Bulletin features an interview with Dr. Raymond Orbach, the founder of the Energy Institute at the University of Texas at Austin, and formerly the director of the Office of Science of the U.S. Department of Energy. Dr. Orbach discusses the global energy perspective in a way that few others can. He focuses on his institute’s initiatives in addressing the multiple problems that the United States faces in the future of energy, including economics, energy security, and environmental issues.

There are two issues that he believes are crucial: shale gas, which has transformed energy security concerns and has raised environmental challenges, and energy storage, which is needed to store base-load levels of electricity produced from wind power. He emphasizes that research at universities is crucial, and energy materials research is an area where students can make a difference through their career choices.

Carbon nanotube composites as potential hydrogen storage materials

By Ashvin Kumar Narayana Swamy, The University of Texas at El Paso, Center for Space Exploration and Technology Research (CSETR)

The problem of hydrogen storage has been plaguing scientists for many years now owing to its low energy content by volume.¹ Researchers from Stanford university and SLAC National Accelerator Laboratory have demonstrated that the addition of platinum nanoparticles to single-walled carbon nanotubes influences the uptake of hydrogen.² They observed a spillover effect of hydrogen from the platinum nanoparticles. X-ray photoelectron spectroscopy measurements were performed using the synchrotron beam radiation to understand this effect. Significant changes in the peak shape of carbon spectra were observed. The measurements indicate that hydrogen storage occurs by the process of dissociation of hydrogen from platinum nanoparticles, breaking of C–C bonds, and the formation of C–H covalent bonds. Thus, it was concluded that for increased hydrogen storage, a higher catalyst particle density and larger carbon nanotube surface area is desirable.

Schematic of spillover mechanism [2]

1. DOE H2 program, Hydrogen Storage, Page 1.
2. R. Bhowmick, S. Rajasekaran, D. Friebel, C. Beasley, L. Jiao, H. Ogasawara, H. Dai, B. Clemens, A. Nilsson, Journal of the American Chemical Society, 133 (14), 5580 (2011).

Gold/Palladium Catalysts Create Useful Materials for Aromatic Hydrocarbons

By Dr. Chianelli, The University of Texas at El Paso, Materials Research & Technology Institute

Researchers at Cardiff University in Wales reported that gold/palladium nano-particles are effective catalysts for selectively activating C–H bonds, allowing insertion of oxygen to create useful chemicals.¹ The particular reaction reported was the reaction of oxygen with toluene to form benzyl benzoate.² The Cardiff group, led by Graham Hutchings, has surprisingly demonstrated the important catalytic activity exhibited by normally inert noble metals such as gold.³ For example, they showed that gold/palladium nanoparticles would combine oxygen and hydrogen to form H₂O₂. This reaction has many potential useful applications in energy for fuels.⁴ One such hoped for reaction is the activation of the terminal C–H bonds of straight chain hydrocarbons, allowing the production of more useful products.

1. C&EN, “A New Feat for Gold Catalysts” 1/10/2011, page 9.
2. Science, DOI: 10.1126/science.1198458.
3. C&EN, 5/10/2010, page 42.
4. C&EN, 2/23/2009, page 8.

Plant Engineers Friction Reducing Material

By Dr. Russell Chianelli, Materials Research and Technology Institute, The University of Texas at El Paso

Many of us have wondered over the amazing Pitcher Plant, a plant that causes insects to slide in to a trap where they are digested.¹ Joanna Aizenberg and her colleagues at Harvard University have synthesized a material that mimics the properties of the Pitcher Plant trap. The material is a Teflon sponge impregnated with a water-repellant and oil-repellant lubricating liquid. The materials, called SLIPS, are self-cleaning, self-healing and have the ability to be made transparent. SLIPS have many potential applications, many of which involve energy savings. For example, ship coatings could reduce friction and thus reduce fuel consumption. Defrosting refrigerators that are clogged with icy walls wastes energy and time. SLIP-coated refrigerator walls could eliminate this problem.

Slip-sliding away to make SLIPS. Aizenberg’s team impregnates a porous network of Teflon nanofibers (gray) with a water- and oil-repellent lubricating liquid (blue).  

 

1. C&E, “Pitcher Inspires Super Slippery Surface,” 9/26/2011, page 5.

Researchers Pioneer Quick Way to Develop Faster Organic Semiconductors for Flexible Displays

 By the Stanford News Service and SLAC Communications

Organic semiconductors hold immense promise for use in thin film and flexible displays – picture an iPad you can roll up – but they haven’t yet reached the speeds needed to drive high definition displays. Inorganic materials such as silicon are fast and durable, but don’t bend, so the search for a fast, durable organic semiconductor continues.

Now a team led by researchers at Stanford and Harvard universities, including a scientist from SLAC's Stanford Synchrotron Radiation Lightsource, has developed a new organic semiconductor material that is among the speediest yet. The scientists also accelerated the development process by using a predictive approach that lopped many months – and could lop years – off the typical timeline.

For the most part, developing a new organic electronic material has been a time-intensive, somewhat hit-or-miss process, requiring researchers to synthesize large numbers of candidate materials and then test them.

The Stanford and Harvard-led group decided to try a computational predictive approach to substantially narrow the field of candidates before expending the time and energy to make any of them.

“Synthesizing some of these compounds can take years,” said Anatoliy Sokolov, a postdoctoral researcher in chemical engineering at Stanford, who worked on synthesizing the material the team eventually settled on.  “It is not a simple thing to do.”

Sokolov works in the laboratory of Zhenan Bao, an associate professor of chemical engineering at Stanford.  They are among the authors of a paper describing the work, published in the Aug. 16 issue of Nature Communications. Alán Aspuru-Guzik, an associate professor of chemistry and chemical biology at Harvard, led the research group there and directed the theory and computation efforts.

The researchers used a material known as DNTT, which had already been shown to be a good organic semiconductor, as their starting point, then considered various compounds possessing chemical and electrical properties that seemed likely to enhance the parent material’s performance if they were attached.

They came up with seven promising candidates.

Semiconductors are all about moving an electrical charge from one place to another as fast as possible. How well a material performs that task is determined by how easy is it for a charge to hop onto the material and how easily that charge can move from one molecule to another within the material.

Using the expected chemical and structural properties of the modified materials, the Harvard team predicted that two of the seven candidates would most readily accept a charge.  They calculated that one of those two was markedly faster in passing that charge from molecule to molecule, so that became their choice. From their analysis, they expected the new material to be about twice as fast as its parent.

Sokolov, the Stanford researcher, said it took about a year and a half to perfect the synthesis of the new compound and make enough of it to test. “Our final yield from what we produced was something like 3 percent usable material and then we still had to purify it.”

When the team members tested the final product, their predictions were borne out. The modified material doubled the speed of the parent material. For comparison, the new material is more than 30 times faster than the amorphous silicon currently used for liquid crystal displays in products such as flat panel televisions and computer monitors.

“It would have taken several years to both synthesize and characterize all the seven candidate compounds. With this approach, we were able to focus on the most promising candidate with the best performance, as predicted by theory,” Bao said. "This is a rare example of truly 'rational' design of new high performance materials.”

Stefan Mannsfeld, staff scientist at Stanford Synchrotron Radiation Lightsource at SLAC National Accelerator Laboratory, helped the team perform X-ray diffraction studies on crystals of the new compound at S.SRL’s beamline 11.3. Then he “crunched the spectrum” of data to determine the dimensions and angles of the compound’s basic arrangement, called a unit cell.

“Our analysis confirmed that the new compound’s arrangement within the unit cell was very close to the prediction,” said Mannsfeld. “This helped the team understand that the new material’s excellent properties arose from the tight packing of its molecules within its unit cell.”

The researchers hope their predictive approach can serve as a blueprint for other research groups working to find a better material for organic semiconductors.

And they’re eager to apply their method to the development of new, high-efficiency material for organic solar cells.

"In the case of renewable energy, we have no time for synthesizing all the possible candidates, we need theory to complement synthetic approaches to accelerate materials discovery,” said Aspuru-Guzik.

Other Stanford researchers contributing to the research include Rajib Mondal and Hylke Akkerman, postdoctoral fellows in the department of chemical engineering when the research was done; Stefan Mannsfeld, a staff scientist at the Stanford Synchrotron Radiation Lightsource; and Arjan Zoombelt, a postdoctoral fellow in chemical engineering.

The research was supported financially by the Stanford Global Climate and Energy Project, Netherlands Organization for Scientific Research, National Science Foundation, King Abdullah University of Science and Technology, Air Force Office of Scientific Research, Harvard Materials Research Science and Engineering Center, the Camille & Henry Dreyfus Foundation and the Sloan Foundation.

A single crystal of the new organic semiconductor material shown in polarized light. It is approximately twice as fast as the parent organic material from which it was derived. The white scale bar at... (Image by Anatoliy Sokolov.)

Scientists Get First Detailed Look at Nitrogen Doping in Single-layer Graphene

by Glennda Chui

The strength, flexibility, transparency and high electrical conductivity of single-layer graphene make it a potentially unique and valuable material for the next generation of electronic devices. Made of carbon atoms arranged in a honeycomb pattern – think of a chicken-wire fence – it is 97 percent transparent and 1,000 times stronger than steel.

Researchers are working on ways to tune the properties of graphene for specific electronic applications. One way to do that is by doping – introducing small amounts of other elements, such as nitrogen or phosphorus, that either add or subtract electrons from the system. Widely used in silicon technology, doping has been carried out experimentally in single-layer graphene sheets; but until now, the details of how the dopant atoms fit into the sheet and bond with their carbon neighbors remained elusive.

In a study reported Aug. 9 in Science, researchers from Columbia University, Sejong University in Korea and SLAC and Brookhaven national laboratories used a combination of four techniques to make the first detailed images of nitrogen-doped graphene film [2]. They showed that individual nitrogen atoms had taken the places of carbon atoms in the two-dimensional sheet; that about half of the extra electron contributed by each nitrogen atom was distributed throughout the graphene lattice; and that this changed the electronic structure of the graphene sheet only within a short distance – about the width of two carbon atoms – from the dopant atoms. The ability to control the electronic structure at the atomic level has important implications for tuning the unique electronic properties of graphene for particular device applications.

“We’re not trying to work on existing systems and make them better. We’re looking for new directions that can potentially enable much higher efficiencies,” said paper co-author Theanne Schiros, a surface scientist at the Department of Energy’s Energy Frontier Research Center at Columbia, who is investigating graphene as a possible electrode for novel photovoltaic devices.

“Now we see that doping is a strategy that can be applied to graphene cleanly and robustly,” she said, providing a potential way to create high-quality graphene films for use in electronic applications, including solar cells.

Schiros is no stranger to SLAC, having done her Ph.D. work [3] here under Anders Nilsson. Her current work at Columbia focuses on using X-rays from synchrotron light sources to probe novel materials for use in renewable energy technologies.

For this study, she returned to SLAC to work with Dennis Nordlund, a staff scientist at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), where recent upgrades allowed them to automatically scan many samples of the nitrogen-doped graphene films at once.

The research team grew the films by depositing chemical vapor on a thin sheet of copper foil.

They analyzed some samples of film while it was on the copper foil, and transferred others to silicon dioxide, the standard substrate for device measurements, for testing. Each sample was examined with Raman spectroscopy and scanning tunneling microscopy (STM) at Columbia, and with X-ray beams at SLAC’s SSRL, and Brookhaven’s National Synchrotron Light Source (NSLS).

The Raman spectra showed that the nitrogen dopant had changed the electronic properties of the graphene sheet without disturbing its basic structure. X-ray measurements at SSRL beamlines 10-1 and 13-2 and NSLS beamline U7A indicated that the nitrogen atoms lay within the plane of the graphene sheet and had each bonded with three carbon neighbors; in other words, each nitrogen atom had replaced a carbon in the sheet.

Finally, the STM images showed the nitrogen atoms as bright spots on the graphene surface. By counting those spots, the researchers determined that the concentration of nitrogen dopant per carbon atom varied from .23 to .35 percent. The images also revealed that the nitrogen atoms stuck out from the graphene layer by about .6 Ångstrom, as they would if they had substituted for carbon in the lattice. These results were consistent with STM image simulations based on theory.

The lead author of the paper was Columbia physics graduate student Liuyan Zhao, working in the laboratory of Abhay N. Pasupathy, and the work was carried out in cooperation with the Energy Frontier Research Center at Columbia, which counts SLAC and Stanford among its collaborators.

While most of the research was performed at Columbia, the advanced materials characterization capabilities at SLAC and Brookhaven played an important role, Schiros said. The results demonstrate the value of the synergy between universities, DOE national labs and the DOE’s 46 Energy Frontier Research Centers [4], which conduct basic and advanced research needed to establish the scientific foundation for a fundamentally new energy economy in the United States.

MRS Bulletin September 2011

By Dr. Russell Chianelli, The University of Texas at El Paso, M.R.T.I

Opening the grid across continents: Desert visions.

The September issue of Energy Quarterly in MRS Bulletin reports on the Desertec initiative that promises to distribute solar power from the Middle East and North Africa (MENA) for distribution in to Europe. Corinna Wu describes Desertec as a centerpiece of Europe’s plans to dramatically increase renewable sources in its energy supply mix. There are many obstacles to developing the system, some political and some technical. However, one issue that arises in centralized solar with power transmission is the transmission grids that must be constructed and the materials used. In some areas, for example in the Southwestern United States, distributed energy systems involving individual people, businesses, and institutions installing solar power devices on local buildings eliminates the need for long transmission systems. However, in this case, energy storage is the issue. We look forward with interest to the competition between these two approaches.

Solid-state lighting: The future looks bright.

Also, in the September issue is an article by Prachi Patel in which she describes the progress in making LED (light-emitting diodes) for practical solid-state lighting devices. LEDs promise to reduce energy use by 75% and increase lifetime by a factor of ten. But technical challenges remain. LEDs are made using semiconductor materials (e.g., InGaN or GaN). However, cost and spectral properties need improvement. These issues are covered in detail in this article.

Batteries for energy: generation and storage

An interview with Yet-Ming Chiang of MIT covers a crucial issue for efficient use of energy in electrical vehicles and solar installations: batteries. Chiang is an entrepreneurial leader in next-generation nano-phosphate lithium batteries, having formed companies such as A123 Systems, which now supplies these batteries to industry, and 24M Systems, which produces flow batteries. Flow batteries are preferred for solar-produced-energy storage. The interview also discusses Chiang’s experience as an entrepreneur and the process that he followed from laboratory research to marketable products.

‘Fracking’ of Shale Holds Huge Potential for Natural Gas and Oil Production

UT Austin’s Energy Institute to Study Claims of Groundwater Contamination

By Raymond L. Orbach, Director, Energy Institute The University of Texas at Austin

Hydraulic fracturing of shale (also known as “fracking”) could unleash vast deposits of natural gas and liquids. In fact, current estimates indicate the practice could provide the United States with up to 200 years of natural gas reserves.

Projections indicate vast reserves of natural gas in several areas, including the Barnett play in north Texas and Eagle Ford in south Texas. Fracking extracts natural gas and oil from these formations, respectively, that otherwise would be unattainable.

While hydraulic fracturing has been in use for decades, it has come under intense scrutiny recently from environmental groups and others who fear it poses health risks from groundwater and air quality contamination. Oil and gas regulators and other experts have found little evidence of a direct link between fracking and groundwater contamination, but remarkably no comprehensive scientific study has been conducted to date.

In response, the Energy Institute at The University of Texas at Austin is conducting a comprehensive review of the impact of fracking on groundwater. The study combines an independent assessment of groundwater contamination claims, with an analysis of the effectiveness of existing laws and policies related to fracking.

Researchers also will investigate seismic events, fugitive air emissions, and other concerns associated with fracking in areas within the Barnett, Marcellus, and Haynesville shale plays.

The goal of the study, which the UT Energy Institute is funding directly, is to promote a fact-based approach to shale gas development so that policymakers can have a sound foundation for developing appropriate rules and regulations. The Environmental Defense Fund has been involved in the design of the study, and will provide comments to researchers before a final report is made public.

Stay tuned for preliminary findings from the Energy Institute study, which we expect will be released sometime this fall.