Scientists create 'nano-reactor' for the production of hydrogen biofuel

Combining bacterial genes and virus shell creates a highly efficient, renewable material used in generating power from water

Scientists at Indiana University have created a highly efficient biomaterial that catalyzes the formation of hydrogen -- one half of the "holy grail" of splitting H2O to make hydrogen and oxygen for fueling cheap and efficient cars that run on water.

A modified enzyme that gains strength from being protected within the protein shell -- or "capsid" -- of a bacterial virus, this new material is 150 times more efficient than the unaltered form of the enzyme.

The process of creating the material was recently reported in "Self-assembling biomolecular catalysts for hydrogen production" in the journal Nature Chemistry.

"Essentially, we've taken a virus's ability to self-assemble myriad genetic building blocks and incorporated a very fragile and sensitive enzyme with the remarkable property of taking in protons and spitting out hydrogen gas," said Trevor Douglas, the Earl Blough Professor of Chemistry in the IU Bloomington College of Arts and Sciences' Department of Chemistry, who led the study. "The end result is a virus-like particle that behaves the same as a highly sophisticated material that catalyzes the production of hydrogen."

Other IU scientists who contributed to the research were Megan C. Thielges, an assistant professor of chemistry; Ethan J. Edwards, a Ph.D. student; and Paul C. Jordan, a postdoctoral researcher at Alios BioPharma, who was an IU Ph.D. student at the time of the study.

The genetic material used to create the enzyme, hydrogenase, is produced by two genes from the common bacteria Escherichia coli, inserted inside the protective capsid using methods previously developed by these IU scientists. The genes, hyaA and hyaB, are two genes in E. coli that encode key subunits of the hydrogenase enzyme. The capsid comes from the bacterial virus known as bacteriophage P22. 

The resulting biomaterial, called "P22-Hyd," is not only more efficient than the unaltered enzyme but also is produced through a simple fermentation process at room temperature.

The material is potentially far less expensive and more environmentally friendly to produce than other materials currently used to create fuel cells. The costly and rare metal platinum, for example, is commonly used to catalyze hydrogen as fuel in products such as high-end concept cars.

"This material is comparable to platinum, except it's truly renewable," Douglas said. "You don't need to mine it; you can create it at room temperature on a massive scale using fermentation technology; it's biodegradable. It's a very green process to make a very high-end sustainable material."

In addition, P22-Hyd both breaks the chemical bonds of water to create hydrogen and also works in reverse to recombine hydrogen and oxygen to generate power. "The reaction runs both ways -- it can be used either as a hydrogen production catalyst or as a fuel cell catalyst," Douglas said.

The form of hydrogenase is one of three occurring in nature: di-iron (FeFe)-, iron-only (Fe-only)- and nitrogen-iron (NiFe)-hydrogenase. The third form was selected for the new material due to its ability to easily integrate into biomaterials and tolerate exposure to oxygen.

NiFe-hydrogenase also gains significantly greater resistance upon encapsulation to breakdown from chemicals in the environment, and it retains the ability to catalyze at room temperature.

Unaltered NiFe-hydrogenase, by contrast, is highly susceptible to destruction from chemicals in the environment and breaks down at temperatures above room temperature -- both of which make the unprotected enzyme a poor choice for use in manufacturing and commercial products such as cars.

These sensitivities are "some of the key reasons enzymes haven't previously lived up to their promise in technology," Douglas said. Another is their difficulty to produce.

"No one's ever had a way to create a large enough amount of this hydrogenase despite its incredible potential for biofuel production. But now we've got a method to stabilize and produce high quantities of the material -- and enormous increases in efficiency," he said.

The development is highly significant according to Seung-Wuk Lee, professor of bioengineering at the University of California-Berkeley, who was not a part of the study.

"Douglas' group has been leading protein- or virus-based nanomaterial development for the last two decades. This is a new pioneering work to produce green and clean fuels to tackle the real-world energy problem that we face today and make an immediate impact in our life in the near future,” said Lee, whose work has been cited in a U.S. Congressional report on the use of viruses in manufacturing.

Beyond the new study, Douglas and his colleagues continue to craft P22-Hyd into an ideal ingredient for hydrogen power by investigating ways to activate a catalytic reaction with sunlight, as opposed to introducing elections using laboratory methods.

"Incorporating this material into a solar-powered system is the next step," Douglas said.

Indiana University

Nanotechnology World Association

Tiny octopods catalyze bright ideas

Rice-led study shows plasmonic sensors and catalysts need not be mutually exclusive  

Nanoscale octopods that do double duty as catalysts and plasmonic sensors are lighting a path toward more efficient industrial processes, according to a Rice University scientist. 

Catalysts are substances that speed up chemical reactions and are essential to many industries, including petroleum, food processing and pharmaceuticals. Common catalysts include palladium and platinum, both found in cars’ catalytic converters. Plasmons are waves of electrons that oscillate in particles, usually metallic, when excited by light. Plasmonic metals like gold and silver can be used as sensors in biological applications and for chemical detection, among others.

Plasmonic materials are not the best catalysts, and catalysts are typically very poor for plasmonics. But combining them in the right way shows promise for industrial and scientific applications, said Emilie Ringe, a Rice assistant professor of materials science and nanoengineering and of chemistry who led the study that appears in Scientific Reports.

“Plasmonic particles are magnets for light,” said Ringe, who worked on the project with colleagues in the U.S., the United Kingdom and Germany. “They couple with light and create big electric fields that can drive chemical processes. By combining these electric fields with a catalytic surface, we could further push chemical reactions. That’s why we’re studying how palladium and gold can be incorporated together.”

The researchers created eight-armed specks of gold and coated them with a gold-palladium alloy. The octopods proved to be efficient catalysts and sensors.

“If you simply mix gold and palladium, you may end up with a bad plasmonic material and a pretty bad catalyst, because palladium does not attract light like gold does,” Ringe said. “But our particles have gold cores with palladium at the tips, so they retain their plasmonic properties and the surfaces are catalytic.”

Just as important, Ringe said, the team established characterization techniques that will allow scientists to tune application-specific alloys that report on their catalytic activity in real time.

The researchers analyzed octopods with a variety of instruments, including Rice’s new Titan Themis microscope, one of the most powerful electron microscopes in the nation. “We confirmed that even though we put palladium on a particle, it’s still capable of doing everything that a similar gold shape would do. That’s really a big deal,” she said.

“If you shine a light on these nanoparticles, it creates strong electric fields. Those fields enhance the catalysis, but they also report on the catalysis and the molecules present at the surface of the particles,” Ringe said.

The researchers used electron energy loss spectroscopy, cathodoluminescence and energy dispersive X-ray spectroscopy to make 3-D maps of the electric fields produced by exciting the plasmons. They found that strong fields were produced at the palladium-rich tips, where plasmons were the least likely to be excited.

Ringe expects further research will produce multifunctional nanoparticles in a variety of shapes that can be greatly refined for applications. Her own Rice lab is working on a metal catalyst to turn inert petroleum derivatives into backbone molecules for novel drugs.

Co-authors of the paper are Christopher DeSantis and Sara Skrabalak of Indiana University; Sean Collins and Paul Midgley of the University of Cambridge, United Kingdom; and Martial Duchamp and Rafal Dunin-Borkowski of the Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and the Peter Grünberg Institute, Jülich, Germany.

The research was supported by the European Union under the Seventh Framework Program, the European Research Council, the Royal Society, Trinity Hall Cambridge, a University of Cambridge Gates Fellowship and the National Science Foundation.

Rice University

A catalyst with a million uses

A hybrid nanowire–nanoparticle palladium catalyst achieves unprecedented catalytic lifetimes for chemical synthesis

Scanning electron microscopy image of the nanowire–nanoparticle catalyst.© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Solid catalysts based on precious metals, such as palladium, are widely used in industry to promote a range of chemical reactions. Finding ways to minimize the consumption of expensive catalytic materials, however, remains a critical challenge. Yoichi Yamada from the RIKEN Center for Sustainable Resource Science and colleagues have now developed a nanostructured catalyst that makes extremely efficient use of trace amounts of catalytic palladium. 

Recent advances in surface studies of metals and computational modeling have given chemists new insights into how to promote more efficient catalytic transformations. One approach involves drastically reducing the volume in which the chemical reaction takes place, such as by using microscale reactors, so that reagents are better directed to the catalyst’s active sites. Another, parallel strategy involves attaching catalysts to materials containing numerous tiny pores, such as mesoporous silica. 

Despite the promise shown by catalysts exhibiting such ‘nanospace’ reaction zones, Yamada and his team realized that existing designs are not suitable for passing large volumes of reagents. To remedy this, the researchers turned to silicon nanowire arrays, which are commonly used in optoelectronics and solar cells. Using a controlled chemical etching procedure, they constructed a dense forest of nanowires projecting upward from a silicon wafer and then immobilized catalytic palladium nanoparticles on the upper part of the array (Fig. 1). These hybrid catalysts contain abundant confined nanospaces, and a wafer just one square centimeter in size can provide plentiful reaction capacity.

The researchers found the nanowire–nanoparticle catalyst to have high activity in Mizoroki-Heck coupling—a chemical reaction that involves linking aromatic molecules to unsaturated hydrocarbons, which finds wide use in the synthesis of pharmaceuticals and agricultural chemicals. Their experiments showed that many coupling reactions proceeded with perfect efficiency, even at tiny concentrations of palladium. The team found similar success with other palladium-catalyzed reactions, such as carbon–hydrogen bond modifications.

The new catalyst also displayed remarkable resilience. Larger-scale Mizoroki-Heck reaction experiments revealed that the nanoscale device catalyzed over two million coupling reactions, at a rate of 40,000 per hour, without losing catalytic activity—the highest turnover ever recorded for this reaction with immobilized catalysts. Yamada notes that this reusability may stem from two synergistic factors: nanospaces on the silicon array that efficiently trap palladium nanoparticles and favorable chemical interactions between silicon and palladium that stabilize nanoparticle immobilization.

The researchers now plan to investigate industrial applications of the catalyst, as well as light-mediated chemical transformations that take advantage of the silicon nanowire’s optical activity.

Source: http://www.rikenresearch.riken.jp/eng/research/7609

Nanocrystal Catalyst Transforms Impure Hydrogen into Electricity

Brookhaven Lab scientists use simple, 'green' process to create novel core-shell catalyst that tolerates carbon monoxide in fuel cells and opens new, inexpensive pathways for zero-emission vehicles

The quest to harness hydrogen as the clean-burning fuel of the future demands the perfect catalysts—nanoscale machines that enhance chemical reactions. Scientists must tweak atomic structures to achieve an optimum balance of reactivity, durability, and industrial-scale synthesis. In an emerging catalysis frontier, scientists also seek nanoparticles tolerant to carbon monoxide, a poisoning impurity in hydrogen derived from natural gas. This impure fuel—40 percent less expensive than the pure hydrogen produced from water—remains largely untapped.

Now, scientists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory—in research published online September 18, 2013 in the journal Nature Communications—have created a high-performing nanocatalyst that meets all these demands. The novel core-shell structure—ruthenium coated with platinum—resists damage from carbon monoxide as it drives the energetic reactions central to electric vehicle fuel cells and similar technologies.

"These nanoparticles exhibit perfect atomic ordering in both the ruthenium and platinum, overcoming structural defects that previously crippled carbon monoxide-tolerant catalysts," said study coauthor and Brookhaven Lab chemist Jia Wang. "Our highly scalable, 'green' synthesis method, as revealed by atomic-scale imaging techniques, opens new and exciting possibilities for catalysis and sustainability."

Fabricating Crystals with Atomic Perfection

Catalysts inside fuel cells pry free the intrinsic energy of hydrogen molecules and convert it into electricity. Platinum performs exceptionally well with pure hydrogen fuel, but the high cost and rarity of the metal impedes its widespread deployment. By coating less expensive metals with thin layers of platinum atoms, however, scientists can retain reactivity while driving down costs and creating core-shell structures with superior performance parameters.

Computational model optimized with Density Functional Theory superimposed over a high-resolution scanning transmission electron microscopy (STEM) image (white dots). Ruthenium retains its structure with ABAB stacking sequence (blue dots) in the core, and the platinum shell switches to the distinct ABCABC stacking sequence.

The carbon monoxide impurities in hydrogen formed from natural gas present another challenge to scientists because they deactivate most platinum catalysts. Ruthenium—less expensive than platinum—promotes carbon monoxide tolerance, but is more prone to dissolution during fuel cells' startup/shutdowns, causing gradual performance decay. 

"We set out to protect ruthenium cores from dissolution with complete platinum shells just one or two atoms thick," Wang said. "Previous surface science studies revealed remarkable variation of surface properties in this core-shell configuration, suggesting the need and the opportunity to perfect the recipe with precise control." 

Doubts existed about whether or not a highly ordered ruthenium core was even possible with a platinum shell—previously synthesized nanoparticles exhibited a weakened crystal structure in the ruthenium.

"Luckily, we found that the loss of ruthenium structure was due to defect-mediated interlayer diffusion, which is avoidable," Wang said. "By eliminating any lattice defects in ruthenium nanoparticles before adding platinum, we preserved the crucial, discrete atomic structure of each element."

The scalable and inexpensive synthesis method uses ethanol—a common and inexpensive solvent—as the reductant to fabricate the nanoparticle core and shell. The sophisticated process requires no other organic agents or metal templates. 

"Simply adjusting temperature, water, and acidity of the solutions gave us complete control over the process and yielded remarkably consistent ruthenium nanoparticle size and uniform platinum coating," said Brookhaven Lab chemist Radoslav Adzic, another coauthor on the study. "This simplicity offers high reproducibility and scalability, and it demonstrates the clear commercial potential of our method."

Core-Shell Characterization

"We took the completed catalysts to other facilities here at the Lab to reveal the exact details of the atomic structure," Wang said. "This kind of rapid collaboration is only possible when you work right next door to world-class experts and instruments."

Scientists at Brookhaven Lab's National Synchrotron Light Source (NSLS) revealed the atomic density, distribution, and uniformity of the metals in the nanocatalysts using a technique called x-ray diffraction, where high-frequency light scatters and bends after interacting with individual atoms. The collaboration also used a scanning transmission electron microscope (STEM) at Brookhaven's Center for Functional Nanomaterials (CFN) to pinpoint the different sub-nanometer atomic patterns. With this instrument, a focused beam of electrons bombarded the particles, creating a map of both the core and shell structures.

"We found that the elements did not mix at the core-shell boundary, which is a critical stride," said CFN physicist Dong Su, coauthor and STEM specialist. "The atomic ordering in each element, coupled with the right theoretical models, tells us about how and why the new nanocatalyst works its magic."

Determining the ideal functional configuration for the core and shell also required the use of the CFN's expertise in computational science. With density functional theory (DFT) calculations, the computer helps identify the most energetically stable platinum-ruthenium structure.

"The DFT analysis connects the dots between performance and configuration, and it corroborates our direct observations from x-ray diffraction and electron microscopy," Adzic said.

Discovery to Deployment

Ballard Power Systems, a company dedicated to fuel cells production, independently evaluated the performance of the new core-shell nanocatalysts. Beyond testing the low-platinum catalysts' high activity in pure hydrogen, Ballard looked specifically at the resistance to carbon monoxide present in impure hydrogen gas and the dissolution resistance during startup/shutdown cycles. The bilayer nanocatalyst exhibited high durability and enhanced carbon monoxide tolerance—the combination enables the use of impure hydrogen without much loss in efficiency or increase in catalyst cost.

The nanocatalyst also performed well in producing hydrogen gas through the hydrogen evolution reaction, leading to another industrial partnership. Proton Onsite, a company specializing in splitting hydrogen from water and other similar processes, has completed feasibility tests for deploying the technology in their production of water electrolyzers, which will now require about 98 percent less platinum.

"Water electrolyzers are already on the market, so this nanocatalyst can deploy quickly," Wang said. "When hydrogen fuel cell vehicles roll out in the coming years, this new structure may accelerate development by driving down costs for both metal catalysts and fuel."

The Center for Functional Nanomaterials at Brookhaven National Laboratory is one of the five DOE Nanoscale Science Research Centers (NSRCs), premier national user facilities for interdisciplinary research at the nanoscale. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE's Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge and Sandia and Los Alamos national laboratories. For more information about the DOE NSRCs, please visit http://nano.energy.gov.

The National Synchrotron Light Source (NSLS) provides intense beams of infrared, ultraviolet, and x-ray light for basic and applied research in physics, chemistry, medicine, geophysics, and environmental and materials sciences.  Supported by the Office of Basic Energy Sciences within the U.S. Department of Energy, the NSLS is one of the world's most widely used scientific facilities. For more information, visit www.nsls.bnl.gov.

DOE's Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

Souce: http://www.bnl.gov/newsroom/news.php?a=11575

Size Matters as Nanocrystals Go Through Phases

Berkeley Lab Researchers at the Molecular Foundry Reveal Fundamental Size-Dependence of Metal Nanocrystals Undergoing Phase Transitions

Understanding what happens to a material as it undergoes phase transformations – changes from a solid to a liquid to a gas or a plasma – is of fundamental scientific interest and critical for optimizing commercial applications. For metal nanocrystals, assumptions about the size-dependence of phase transformations were made that now need to be re-evaluated. A team of researchers at the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) has demonstrated that as metal nanocrystals go through phase transformations, size can make a much bigger difference than previously believed.

Working at Berkeley Lab’s Molecular Foundry, a DOE Nanoscale Science Research Center, the team led by Jeffrey Urban and Stephen Whitelam developed a unique optical probe based on luminescence that provided the first direct observations of metal nanocrystals undergoing phase transformations during reactions with hydrogen gas. Analysis of their observations revealed a surprising degree of size-dependence when it comes to such critical properties as thermodynamics and kinetics. These results hold important implications for the future design of hydrogen storage systems, catalysts, fuel cells and batteries.

“No one has ever directly observed phase transformations in metal nanocrystal systems before so no one saw the size dependence factor, which was obscured by other complicating effects, hidden in plain sight if you will,” Urban says. “The assumption had been that for nanocrystals beyond 15 nanometers, the thermodynamic and kinetic behavior would be essentially bulk-like. However, our results show that pure size effects can be understood and productively employed over a much broader range of nanocrystal sizes than previously thought.”

Stephen Whitelam (left) and Jeffrey Urban at Berkeley Lab’s Molecular Foundry led the first direct observations of metal nanocrystals undergoing phase transformations during reactions with hydrogen gas. (Photo by Roy Kaltschmidt)

Urban and Whitelam, both of whom hold appointments with Berkeley Lab’s Materials Sciences Division, are the corresponding authors of a paper describing this study in the journal Nature Materials. The paper is titled “Uncovering the intrinsic size dependence of hydriding phase transformations in nanocrystals.” Co-authors are Rizia Bardhan, Lester Hedges, Cary Pint and Ali Javey.

While it is well established that materials on the nanoscale can offer physical, chemical and mechanical properties not displayed at the microscale, knowledge as to how these properties can be altered as nanocrystals undergo phase transformations has been lacking.

“Quantitative understanding of nanocrystal phase transformations has been hindered by difficulties in directly monitoring well-characterized nanoscale systems in reactive environments,” Urban says.

Urban and his colleagues addressed this problem with a custom-built stainless steel gas-tight cell with optical windows and heating elements and connected to a high vacuum pump. They used this experimental setup to collect in situ luminescence spectra with a confocal Raman microscope as palladium nanocubes interacted with hydrogen gas. The nanocubes were synthesized by wet-chemistry and were all clear-faceted single-crystalline objects with a narrow range in size distribution.

“Our experimental setup allowed for rapid, direct monitoring of minuscule alterations in luminescence during hydrogen sorption,” Urban says. “This allowed us to uncover the size-dependence of the intrinsic thermodynamics and kinetics of hydriding and dehydriding phase transformations. We observed a dramatic decrease in luminescence as the palladium nanocubes formed hydrides. This lost luminescence was regained during dehydriding.”

This scanning electron micrograph shows palladium nanocubes with a side length of approximately 32 nanometers.

A statistical mechanical model whose development was led by Whitelam and co-author Hedges was then used to quantify the observational data for palladium nanocubes of all sizes. Because of the narrow size distribution of the nanocubes, Whitelam, Urban and their colleagues were able to show a direct correlation between luminescence and phase transitions that can be applied to other metal nanocrystal systems as well.

“Simple geometric arguments tell us that under certain conditions, thermally driven solid-state phase transformations are governed by nanocrystal dimensions,” Whitelam says. “These arguments further suggest ways of optimizing hydrogen storage kinetics in a variety of metal nanocrystal systems.”

The next step in this research will be to examine the effects of dopants on phase transformations in metal nanosystems.

“Our luminescence-probe and statistical mechanical model are a versatile combination,” Urban says, “that allow us to look at a number of gas-nanocrystal interactions in which controlling the thermodynamics of the interactions is paramount.”

This research was supported by DOE’s Office of Science through the Molecular Foundry and through the Center for Nanoscale Control of Geologic Carbon Dioxide, a DOE Energy Frontier Research Center. Additional support was provided by DOE’s Office of Energy Efficiency and Renewable Energy and by Mohr Davidow Ventures, a venture capital firm.

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Lawrence Berkeley National Laboratory addresses the world’s most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab’s scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy’s Office of Science. For more, visit www.lbl.gov.

The Molecular Foundry is one of five DOE Nanoscale Science Research Centers (NSRCs), national user facilities for interdisciplinary research at the nanoscale, supported by the DOE Office of Science.  Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative.  The NSRCs are located at DOE’s Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge and Sandia and Los Alamos National Laboratories.  For more information about the DOE NSRCs, please visit http://science.energy.gov.

The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

http://newscenter.lbl.gov/feature-stories/2013/08/26/size-matters-as-nanocrystals-go-through-phases/