Tagged: Catalyst technology Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 7:20 pm on March 24, 2016 Permalink | Reply
    Tags: , Catalyst technology,   

    From SLAC: “New Catalyst is Three Times Better at Splitting Water” 


    SLAC Lab

    March 24, 2016

    With a combination of theory and clever, meticulous gel-making, scientists from the Department of Energy’s SLAC National Accelerator Laboratory and the University of Toronto have developed a new type of catalyst that’s three times better than the previous record-holder at splitting water into hydrogen and oxygen – the vital first step in making fuels from renewable solar and wind power.

    The research, published today in the journal Science, outlines a potential way to make a future generation of water-splitting catalysts from three abundant metals – iron, cobalt and tungsten – rather than the rare, costly metals that many of today’s catalysts rely on.

    1
    One way to store intermittent sun and wind energy is to use it to split water into oxygen and hydrogen, and then use the hydrogen as fuel. Now scientists at SLAC and the University of Toronto have invented a new type of catalyst that makes this process three times more efficient. In this water-splitting device on the Toronto campus, hydrogen is bubbling up from the left electrode and oxygen is bubbling up from the right one. (Marit Mitchell/University of Toronto)

    “The good things about this catalyst are that it’s easy to make, its production can be very easily scaled up without any super-advanced tools, it’s consistent, and it’s very robust,” said Aleksandra Vojvodic, a SLAC staff scientist with the SUNCAT Center for Interface Science and Catalysis who led the theoretical side of the work.
    Storing Sun and Wind Power

    Scientists have been searching for an efficient way to store electricity generated by solar and wind power so it can be used any time – not just when the sun shines and breezes blow. One way to do that is to use the electrical current to split water molecules into hydrogen and oxygen, and store the hydrogen to use later as fuel.

    This reaction takes place in several steps, each requiring a catalyst – a substance that promotes chemical reactions without being consumed itself – to move it briskly along. In this case the scientists focused on a step where oxygen atoms pair up to form a gas that bubbles away, which has been a bottleneck in the process.

    In previous work, Vojvodic and her SUNCAT colleagues had used theory and computation to look at water-splitting oxide catalysts that contain one or two metals and predict ways to make them more active. For this study, Edward H. Sargent, a professor of electrical and computer engineering at the University of Toronto, asked them to look at the effect of adding tungsten – a heavy, dense metal used in light bulb filaments and radiation shielding – to an iron-cobalt catalyst that worked, but not very efficiently.

    With the aid of powerful computers at SLAC and elsewhere and state-of-the-art computational tools, the SUNCAT team determined that adding tungsten should dramatically increase the catalyst’s activity – especially if the three metals could be mixed so thoroughly that their atoms were uniformly distributed near the active site of the catalyst, where the reaction takes place, rather than separating into individual clusters as they normally tend to do.

    “Tungsten is quite a large atom compared to the other two, and when you add a little bit of it, it expands the atomic lattice, and this affects the reaction not only geometrically but also electronically,” Vojvodic said. “We were able to understand, on the atomic scale, why it works, and then that was verified experimentally.”

    2
    Images of the tiny catalyst particles, made with electron energy loss spectroscopy, show how evenly metal atoms are distributed within the oxide material (Fe=iron, Co=cobalt, W=tungsten and O=oxygen). This extremely uniform distribution helps make the catalyst three times more efficient at splitting water than any previous one. Each frame here is about 4 nanometers wide, which is roughly the width of 40 hydrogen atoms. (B. Zhang et al./Science)

    Add Metal Atoms, Mix and Gel

    Based on that information, Sargent’s team developed a novel way to distribute the three metals uniformly within the catalyst: They dissolved the metals and other ingredients in a solution and then slowly turned the solution into a gel at room temperature, tweaking the process so the metal atoms did not clump together. The gel was then dried into a white powder whose particles were riddled with tiny pores, increasing the surface area where chemicals can attach and react with each other.

    In tests, the catalyst was able to generate oxygen gas three times faster, per unit weight, than the previous record-holder, Sargent said, and it also proved to be stable through hundreds of reaction cycles.

    “It’s a big advance, although there’s still more room to improve,” he said. “”And we will need to make catalysts and electrolysis systems even more efficient, cost effective and high intensity in their operation in order to drive down the cost of producing renewable hydrogen fuels to an even more competitive level.”

    Sargent said the researchers hope to use the same method to develop other three-metal catalysts for splitting water and also for splitting carbon dioxide, a greenhouse gas released by burning fossil fuels, to make renewable fuels and chemical feed stocks. He and five other members of the University of Toronto team have filed for a provisional patent on the technique for preparing the catalyst.

    Future Directions

    “There are a lot of things we further need to understand,” Vojvodic said. “Are there other abundant metals we can test as mixtures in oxides? What are the optimal mixtures of the components? How stable is the catalyst, and how can we scale up its production? It needs to be tested at the device level, really.”

    Jeffrey C. Grossman, a professor of materials science and engineering at MIT who was not involved in the study, said, “The work impressively highlights the power of tightly coupled computational materials science with advanced experimental techniques, and sets a high bar for such a combined approach. It opens new avenues to speed progress in efficient materials for energy conversion and storage.”

    SLAC research associate Michal Bajdich and Stanford postdoctoral researcher Max García-Melchor also contributed to this work, along with researchers from the DOE’s Brookhaven National Laboratory; East China University of Science & Technology, Tianjin University and the Beijing Synchrotron Radiation Facility in China; and the Canadian Light Source. The research was funded by a number of sources, including the Ontario Research Fund – Research Excellence Program, Natural Sciences and Engineering Research Council of Canada and the CIFAR Bio-Inspired Solar Energy Program, as well as the DOE Office of Science, which funds SUNCAT, and the SLAC Laboratory Directed Research and Development program.

    Citation: B. Zhang et al., Homogeneously dispersed, multimetal oxygen-evolving catalysts,Science, 24 March 2016 (10.1126/science.aaf1525)

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
    i1

     
  • richardmitnick 1:08 pm on November 30, 2015 Permalink | Reply
    Tags: , Catalyst technology,   

    From EMSL: “Scarcity Drives Efficiency” 

    EMSL

    EMSL

    September 28, 2015 [This just became available.]
    Tim Scheibe tim.scheibe@pnnl.gov at EMSL
    Younan Xia younan.xia@bme.gatech.edu

    Platinum can be an efficient fuel cell catalyst

    1
    Researchers developed a new class of catalysts by putting essentially all of the platinum atoms on the surface material and minimized the use of atoms in the core, thereby increasing the utilization efficiency of precious metals for fuel cells.

    The Science

    Platinum is an excellent catalyst for reactions in fuel cells, but its scarcity and cost have driven scientists to look for more efficient ways to use the precious metal. In a recent study, researchers developed a new class of catalysts by putting essentially all of the platinum atoms on the surface and minimizing the use of atoms in the core, thereby increasing efficient utilization of platinum for fuel cells.

    The Impact

    The novel nanocage catalyst will help promote the sustainable use of platinum and other precious metals for energy and other industrial applications. The reduced costs associated with the novel nanostructures will encourage commercialization of this technology for the development of zero-emission energy sources.

    Summary

    Researchers from Georgia Institute of Technology and Emory University, Xiamen University, University of Wisconsin–Madison, Oak Ridge National Laboratory and Arizona State University fabricated cubic and octahedral nanocages by depositing a few atomic layers of platinum on palladium nanocrystals, and then completely etching away the palladium core. Density functional theory (DFT) calculations suggested the etching process was initiated by the formation of vacancies through the removal of palladium atoms incorporated into the outermost layer during the deposition of platinum. Some of the computational work was performed using computer resources at EMSL, the Environmental Molecular Sciences Laboratory, a Department of Energy Office of Biological and Environmental Research user facility. DFT calculations were performed at supercomputing centers at EMSL, Argonne National Laboratory and the National Energy Research Scientific Computing Center.

    Based on the findings, researchers propose that during platinum deposition, some palladium atoms are incorporated into the outermost platinum layers. Upon contact with the etchant—an acid or corrosive chemical—the palladium atoms in the outermost layer of the platinum shell are oxidized to generate vacancies in the surface of the nanostructure. The underlying palladium atoms then diffuse to these vacancies and are continuously etched away, leaving behind atom-wide channels. Over time, the channels grow in size to allow direct corrosion of palladium from the core. This process leads to a nanocage with a few layers of platinum atoms in the shell and a hollow interior.

    Compared to a commercial platinum/carbon catalyst, the nanocages showed enhanced catalytic activity and durability. The findings demonstrate it is possible to design fuel cell catalysts with efficient use of precious metals without sacrificing performance. Moreover, it is possible to tailor the arrangement of atoms or the surface structure of catalytic particles to optimize their catalytic performance for a specific type of chemical reaction. The researchers are testing these catalysts in fuel cell devices to determine how to further improve their design for clean energy applications.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    EMSL campus

    Welcome to EMSL. EMSL is a national scientific user facility that is funded and sponsored by DOE’s Office of Biological & Environmental Research. As a user facility, our scientific capabilities – people, instruments and facilities – are available for use by the global research community. We support BER’s mission to provide innovative solutions to the nation’s environmental and energy production challenges in areas such as atmospheric aerosols, feedstocks, global carbon cycling, biogeochemistry, subsurface science and energy materials.

    A deep understanding of molecular-level processes is critical to gaining a predictive, systems-level understanding of the impacts of aerosols and terrestrial systems on climate change; making clean, affordable, abundant energy; and cleaning up our legacy wastes. Visit our Science page to learn how EMSL leads in these areas, through our Science Themes.

    Team’s in Our DNA. We approach science differently than many institutions. We believe in – and have proven – the value of drawing together members of the scientific community and assembling the people, resources and facilities to solve problems. It’s in our DNA, since our founder Dr. Wiley’s initial call to create a user facility that would facilitate “synergism between the physical, mathematical, and life sciences.” We integrate experts across disciplines; experiment with theory; and our user program proposal calls with other user facilities.

    We proudly provide an enriched, customized experience that allows users to connect with our people and capabilities in an environment where we focus on solving problems. We collaborate with researchers from academia, government labs and industry, and from nearly all 50 states and from other countries.

     
  • richardmitnick 1:35 am on November 24, 2015 Permalink | Reply
    Tags: , Catalyst technology, ,   

    From SLAC: “Atom-sized Craters Make a Catalyst Much More Active” 


    SLAC Lab

    November 23, 2015

    SLAC, Stanford Discovery Could Speed Important Chemical Reactions, Such As Making Hydrogen Fuel

    1
    Illustration of a catalyst being bombarded with argon atoms to create holes where chemical reactions can take place. The catalyst is molybdenum disulfide, or MoS2. The bombardment removed about one-tenth of the sulfur atoms (yellow) on its surface. Researchers then draped the holey catalyst over microscopic bumps to change the spacing of the atoms in a way that made the catalyst even more active. (Charlie Tsai/ Stanford University)

    2
    This electron microscope image of a molybdenum sulfide catalyst shows “holes” left by removing sulfur atoms. Creating these holes and stretching the catalyst to change the spacing of its atoms made the catalyst much more active in promoting chemical reactions. The bright dots are molybdenum atoms; the lighter ones are sulfur. The image measures 4 nanometers on a side. (Hong Li/Stanford Nanocharacterizaton Laboratory)

    Bombarding and stretching an important industrial catalyst opens up tiny holes on its surface where atoms can attach and react, greatly increasing its activity as a promoter of chemical reactions, according to a study by scientists at Stanford University and the Department of Energy’s SLAC National Accelerator Laboratory.

    The method could offer a much cheaper way to rev up the production of clean hydrogen fuel from water, the researchers said, and should also apply to other catalysts that promote useful chemical reactions. The study was published Nov. 9 in Nature Materials.

    “This is just the first indication of a new effect, very much in the research stage,” said Xiaolin Zheng, an associate professor of mechanical engineering at Stanford who led the study. “But it opens up totally new possibilities yet to be explored.”

    Finding a Cheap, Abundant Substitute

    Catalysts are substances that promote chemical reactions without being consumed themselves, so they can be used over and over again. Natural catalysts are endlessly at work in plants, animals and our bodies. Industrial catalysts are used to make fuel, fertilizer and consumer products; they’re a multi-billion-dollar industry in their own right.

    The catalyst studied here, molybdenum disulfide or MoS2, helps remove sulfur from petroleum in refineries. But scientists think it might also be a good alternative to platinum as a catalyst for a reaction that joins hydrogen atoms together to make hydrogen gas for fuel.

    “We know platinum is very good at catalyzing this reaction,” said study co-author Jens Nørskov, director of the SUNCAT Center for Interface Science and Catalysis, a joint Stanford/SLAC institute. “But it’s a non-starter because of its rarity. There isn’t enough of it on Earth for large-scale hydrogen fuel production.”

    MoS2 is much cheaper and made of abundant ingredients, and it comes in flexible sheets just one molecule thick, which are stacked together to make catalyst particles, Zheng said. All the catalytic action takes place on the edges of those sheets, where dangling chemical bonds can grab passing atoms and hold them together until they react.

    Researchers have tried all sorts of schemes to increase the active area where this atomic matchmaking goes on. Most of them involve engineering the catalyst sheets to expose more edges, or adding chemicals to make the edges more active.

    A Holey, Stretchy Solution

    In the new approach, Stanford postdoctoral researcher Hong Li used an instrument in the Stanford Nanocharacterization Laboratory to bombard a sheet of MoS2 with argon atoms. This knocked about 1 out of 10 sulfur atoms out of the surface of the sheet, leaving holes surrounded by dangling bonds.

    Then he stretched the holey sheet over microscopic bumps made of silicon dioxide coated with gold. He wet the sheet with a solvent, and when it dried the sheet was permanently deformed: The spacing of the atoms had changed in a way that made the holes much more chemically reactive.

    “Before, the top surface of the sheet was not reactive. It was inert – zero, almost,” Zheng said. “Now the surface is more catalytically active than the edges. And we can tune this activity so the bonds that form on the catalyst are just right – strong enough to hold the reacting atoms in place, but weak enough so they’ll let go of the finished product once the atoms have joined together.”

    SUNCAT theorists, including graduate student Charlie Tsai, played an important role in predicting which combinations of bombarding and stretching would produce the best results, using calculations made with SLAC supercomputers. The researchers said a combination of computation and experiment will be important in finding completely new kinds of active catalytic sites in the future.

    Going forward, Zheng said, “We need to figure out how to do this in the layered catalytic particles that are used in industry, and whether we can apply the same idea to other catalytic materials.”

    They’ll also need to find a better way to make the atom-sized holes, Tsai said. “Bombarding with argon is not practical,” he said. “The procedure is expensive, and it can’t really be scaled up for things like fuel production. So we’ve been working on a follow-up study where we try to replicate the results using a simpler process.”

    Scientists from the Stanford Institute for Materials and Energy Research (SIMES) also played a key role in these experiments. The research was supported by the Samsung Advanced Institute of Technology (SAIT) and Samsung R&D Center America, Silicon Valley, and by SUNCAT and the Center on Nanostructuring for Efficient Energy Conversion at Stanford, both funded by the DOE Office of Science.

    Citation: H. Li et al., Nature Materials, 9 November 2015 (10.1038/nmat4465)

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
    i1

     
  • richardmitnick 11:06 am on October 9, 2015 Permalink | Reply
    Tags: , Catalyst technology,   

    From TUM: “Faster design – better catalysts” 

    Techniche Universitat Munchen

    Techniche Universitat Munchen

    08.10.2015
    Prof. Dr. Aliaksandr S. Bandarenka
    Technical University of Munich
    Physics of Energy Conversion and Storage
    James-Franck-Str. 1, 85748 Garching, Germany
    Tel.: +49 89 289 12531
    bandarenka@ph.tum.de

    New method facilitates research on fuel cell catalysts

    1
    The different number of similar neighbors has an important influence on the catalytic activity of surface atoms of a nanoparticle – Image: David Loffreda, CNRS, Lyon

    While the cleaning of car exhausts is among the best known applications of catalytic processes, it is only the tip of the iceberg. Practically the entire chemical industry relies on catalytic reactions. Catalyst design plays a key role in improving these processes. An international team of scientists has now developed a concept that elegantly correlates geometric and adsorption properties. They validated their approach by designing a new platinum-based catalyst for fuel cell applications.

    Hydrogen would be an ideal energy carrier: Surplus wind power could split water into its elements. The hydrogen could power fuel cell-driven electric cars with great efficiency. While the only exhaust would be water, the range could be as usual. But fuel cell vehicles are still a rare exception. The required platinum (Pt) is extremely expensive and the world’s annual output would not suffice for all cars.

    A key component of the fuel cell is the platinum catalyst that is used to reduce oxygen. It is well known that not the entire surface but only a few particularly exposed areas of the platinum, the so-called active centers, are catalytically active.

    A team of scientists from Technical University of Munich and Ruhr University Bochum (Germany), the Ecole normale superieure (ENS) de Lyon, Centre national de la recherche scientifique (CNRS), Universite Claude Bernard Lyon 1 (France) and Leiden University (Netherlands) have set out to determine what constitutes an active center.

    Studying the model

    A common method used in developing catalysts and in modeling the processes that take place on their surfaces is computer simulation. But as the number of atoms increases, quantum chemical calculations quickly become extremely complex.

    With their new methodology called “coordination-activity plots” the research team presents an alternative solution that elegantly correlates geometric and adsorption properties. It is based on the generalized coordination number (GCN) , which counts the immediate neighbors of an atom and the coordination numbers of its neighbors.

    Calculated with the new approach, a typical Pt (111) surface has a GCN value of 7.5. According to the coordination-activity plot, the optimal catalyst should, however, achieve a value of 8.3. The required larger number of neighbors can be obtained by inducing atomic-size cavities into the platinum surface, for example.

    Successful practical test

    In order to validate the accuracy of their new methodology, the researchers computationally designed a new type of platinum catalyst for fuel cell applications. The model catalysts were prepared experimentally using three different synthesis methods. In all three cases, the catalysts showed up to three and a half times greater catalytic activity.

    “This work opens up an entirely new way for catalyst development: the design of materials based on geometric rationales which are more insightful than their energetic equivalents,” says Federico Calle-Vallejo. “Another advantage of the method is that it is based clearly on one of the basic principles of chemistry: coordination numbers. This significantly facilitates the experimental implementation of computational designs.”

    “With this knowledge, we might be able to develop nanoparticles that contain significantly less platinum or even include other catalytically active metals,” says Professor Aliaksandr S. Bandarenka, tenure track professor at Technical University of Munich. “And in future we might be able to extend our method to other catalysts and processes, as well.”

    Publication

    Finding optimal surface sites on heterogeneous catalysts by counting nearest neighbors, Federico Calle-Vallejo, Jakub Tymoczko, Viktor Colic, Quang Huy Vu, Marcus D. Pohl, Karina Morgenstern, David Loffreda, Philippe Sautet, Wolfgang Schuhmann, Aliaksandr S. Bandarenka. Science, october 9., 2015; DOI : 10.1126/science.aab3501

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Techniche Universitat Munchin Campus

    Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

     
  • richardmitnick 8:25 am on September 15, 2015 Permalink | Reply
    Tags: , Catalyst technology,   

    From Wisconsin: “Discovery of a highly efficient catalyst eases way to hydrogen economy” 

    U Wisconsin

    University of Wisconsin

    Sept. 14, 2015
    David Tenenbaum

    1
    Bathed in simulated sunlight, this photoelectrolysis cell in the lab of Song Jin splits water into hydrogen and oxygen using a catalyst made of the abundant elements cobalt, phosphorus and sulfur. Photos: David Tenenbaum

    Hydrogen could be the ideal fuel: Whether used to make electricity in a fuel cell or burned to make heat, the only byproduct is water; there is no climate-altering carbon dioxide.

    Like gasoline, hydrogen could also be used to store energy.

    Hydrogen is usually produced by separating water with electrical power. And although the water supply is essentially limitless, a major roadblock to a future “hydrogen economy” is the need for platinum or other expensive noble metals in the water-splitting devices.

    Noble metals resist oxidation and include many of the precious metals, such as platinum, palladium, iridium and gold.

    2
    Song Jin

    “In the hydrogen evolution reaction, the whole game is coming up with inexpensive alternatives to platinum and the other noble metals,” says Song Jin, a professor of chemistry at the University of Wisconsin-Madison.

    In the online edition of Nature Materials that appears today, Jin’s research team reports a hydrogen-making catalyst containing phosphorus and sulfur — both common elements — and cobalt, a metal that is 1,000 times cheaper than platinum.

    Catalysts reduce the energy needed to start a chemical reaction. The new catalyst is almost as efficient as platinum and likely shows the highest catalytic performance among the non-noble metal catalysts reported so far, Jin reports.

    The advance emerges from a long line of research in Jin’s lab that has focused on the use of iron pyrite (fool’s gold) and other inexpensive, abundant materials for energy transformation. Jin and his students Miguel Cabán-Acevedo and Michael Stone discovered the new high-performance catalyst by replacing iron to make cobalt pyrite, and then added phosphorus.

    Although electricity is the usual energy source for splitting water into hydrogen and oxygen, “there is a lot of interest in using sunlight to split water directly,” Jin says.

    The new catalyst can also work with the energy from sunlight, Jin says. “We have demonstrated a proof-of-concept device for using this cobalt catalyst and solar energy to drive hydrogen generation, which also has the best reported efficiency for systems that rely only on inexpensive catalysts and materials to convert directly from sunlight to hydrogen.”

    Many researchers are looking to find a cheaper replacement for platinum, Jin says. “Because this new catalyst is so much better and so close to the performance of platinum, we immediately asked WARF (the Wisconsin Alumni Research Foundation) to file a provisional patent, which they did in just two weeks.”

    Many questions remain about a catalyst that has only been tested in the lab, Jin says. “One needs to consider the cost of the catalyst compared to the whole system. There’s always a tradeoff: If you want to build the best electrolyzer, you still want to use platinum. If you are able to sacrifice a bit of performance and are more concerned about the cost and scalability, you may use this new cobalt catalyst.”

    Strategies to replace a significant portion of fossil fuels with renewable solar energy must be carried out on a huge scale if they are to affect the climate crisis, Jin says. “If you want to make a dent in the global warming problem, you have to think big. Whether we imagine making hydrogen from electricity, or directly from sunlight, we need square miles of devices to evolve that much hydrogen. And there might not be enough platinum to do that.”

    The collaborative team included Professor J.R. Schmidt, a theoretical chemist at UW-Madison, and electrical engineering Professor Jr-Hau He and his students from King Abdullah University of Science and Technology in Saudi Arabia. The U.S. Department of Energy provided major funding for the study.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    In achievement and prestige, the University of Wisconsin–Madison has long been recognized as one of America’s great universities. A public, land-grant institution, UW–Madison offers a complete spectrum of liberal arts studies, professional programs and student activities. Spanning 936 acres along the southern shore of Lake Mendota, the campus is located in the city of Madison.

     
  • richardmitnick 10:08 pm on September 14, 2015 Permalink | Reply
    Tags: , Catalyst technology,   

    From ORNL: “New ORNL catalyst addresses engine efficiency, emissions quandary” 

    i1

    Oak Ridge National Laboratory

    September 14, 2015
    Ron Walli, Communications
    wallira@ornl.gov, 865.576.0226

    1
    Researcher Andrew Binder and colleagues discovered that by mixing three components they could create an innovative catalyst that performs well at low temperatures without the use of precious metals.

    A catalyst being developed by researchers at the Department of Energy’s Oak Ridge National Laboratory could overcome one of the key obstacles still preventing automobile engines from running more cleanly and efficiently.

    The mixed oxide catalyst could solve the longstanding problem of inhibition, in which nitrogen oxides, carbon monoxide and hydrocarbons effectively clog the catalyst designed to cleanse a vehicle’s exhaust stream. This happens as these three pollutants compete for active surface sites on the catalyst. Now, however, ORNL’s low-cost catalyst composed of copper oxide, cobalt oxide and cerium oxide shows considerable promise when tested in simulated exhaust streams.

    “Our catalyst potentially fixes the inhibition problem without precious metals and could help more efficient engines meet upcoming stricter emission regulations,” said Todd Toops of ORNL’s Energy and Transportation Science Division. Toops noted that the unique formulation builds on previous work by colleagues Andrew Binder and Sheng Dai, who varied the composition of the three catalyst components in search of improved oxidation activity under simple conditions.

    Researchers also emphasized that the lower exhaust temperatures associated with efficiency gains pose additional challenges because conventional catalysts perform more efficiently at high temperatures. Hydrocarbons – and there are hundreds of species – pose perhaps the biggest challenge.

    “As we make engines more efficient, less wasted heat exits the engine into the exhaust system where catalysts clean up the pollutant emissions,” said Jim Parks, a member of the Energy and Transportation Science Division. “The lower temperatures in the exhaust from the more efficient engines are lower than the typical operating range of catalysts, so we need innovations like this catalyst to lower the operating range and control the engine pollutants.”

    This finding, published in the journal Angewandte Chemie, is encouraging, the authors note, as “vehicles with internal combustion engines will likely remain a dominant fraction of the light-duty fleet in both hybrid and conventional drivetrains.”

    Binder, Toops, Parks and Dai performed extensive tests using different ratios of copper oxide, cobalt oxide and ceria to determine the optimum ratio, which was initially evaluated at an atomic ratio of 1:5:5, respectively. Next, researchers will determine scalability of this approach and perform cost-benefit analyses. The paper, titled “Low Temperature CO Oxidation over Ternary Oxide with High Resistance to Hydrocarbon Inhibition,” is available at http://onlinelibrary.wiley.com/doi/10.1002/ange.201506093/abstract.

    DOE’s Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program, funded this research.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    ORNL is managed by UT-Battelle for the Department of Energy’s Office of Science. 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.

    i2

     
  • richardmitnick 4:11 pm on September 10, 2015 Permalink | Reply
    Tags: , , Catalyst technology, , SLAC UED   

    From SLAC: “SLAC’s Ultrafast ‘Electron Camera’ Visualizes Ripples in 2-D Material” 


    SLAC Lab

    September 10, 2015

    1
    Researchers have used SLAC’s experiment for ultrafast electron diffraction (UED), one of the world’s fastest “electron cameras,” to take snapshots of a three-atom-thick layer of a promising material as it wrinkles in response to a laser pulse. Understanding these dynamic ripples could provide crucial clues for the development of next-generation solar cells, electronics and catalysts. (SLAC National Accelerator Laboratory)

    2
    Illustrations (each showing a top and two side views) of a single layer of molybdenum disulfide (atoms shown as spheres). Top left: In a hypothetical world without motions, the “ideal” monolayer would be flat. Top right: In reality, the monolayer is wrinkled as shown in this room-temperature simulation. Bottom: If a laser pulse heats the monolayer up, it sends ripples through the layer. These wrinkles, which researchers have now observed for the first time, have large amplitudes and develop on ultrafast timescales. (SLAC National Accelerator Laboratory)

    SLAC Electron Camera UED
    SLAC’s electron Camera

    SLAC electron camera schematic
    SLAC’s electron Camera schematic

    New research led by scientists from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University shows how individual atoms move in trillionths of a second to form wrinkles on a three-atom-thick material. Revealed by a brand new “electron camera,” one of the world’s speediest, this unprecedented level of detail could guide researchers in the development of efficient solar cells, fast and flexible electronics and high-performance chemical catalysts.

    The breakthrough, accepted for publication Aug. 31 in Nano Letters, could take materials science to a whole new level. It was made possible with SLAC’s instrument for ultrafast electron diffraction (UED), which uses energetic electrons to take snapshots of atoms and molecules on timescales as fast as 100 quadrillionths of a second.

    “This is the first published scientific result with our new instrument,” said scientist Xijie Wang, SLAC’s UED team lead. “It showcases the method’s outstanding combination of atomic resolution, speed and sensitivity.”

    SLAC Director Chi-Chang Kao said, “Together with complementary data from SLAC’s X-ray laser Linac Coherent Light Source, UED creates unprecedented opportunities for ultrafast science in a broad range of disciplines, from materials science to chemistry to the biosciences.” LCLS is a DOE Office of Science User Facility.

    SLAC LCLS Inside
    LCLS


    download mp4 here.

    Extraordinary Material Properties in Two Dimensions

    Monolayers, or 2-D materials, contain just a single layer of molecules. In this form they can take on new and exciting properties such as superior mechanical strength and an extraordinary ability to conduct electricity and heat. But how do these monolayers acquire their unique characteristics? Until now, researchers only had a limited view of the underlying mechanisms.

    “The functionality of 2-D materials critically depends on how their atoms move,” said SLAC and Stanford researcher Aaron Lindenberg, who led the research team. “However, no one has ever been able to study these motions on the atomic level and in real time before. Our results are an important step toward engineering next-generation devices from single-layer materials.” The research team looked at molybdenum disulfide, or MoS2, which is widely used as a lubricant but takes on a number of interesting behaviors when in single-layer form – more than 150,000 times thinner than a human hair.

    For example, the monolayer form is normally an insulator, but when stretched, it can become electrically conductive. This switching behavior could be used in thin, flexible electronics and to encode information in data storage devices. Thin films of MoS2 are also under study as possible catalysts that facilitate chemical reactions. In addition, they capture light very efficiently and could be used in future solar cells.

    Because of this strong interaction with light, researchers also think they may be able to manipulate the material’s properties with light pulses.

    “To engineer future devices, control them with light and create new properties through systematic modifications, we first need to understand the structural transformations of monolayers on the atomic level,” said Stanford researcher Ehren Mannebach, the study’s lead author.

    3
    Visualization of laser-induced motions of atoms (black and yellow spheres) in a molybdenum disulfide monolayer: The laser pulse creates wrinkles with large amplitudes – more than 15 percent of the layer’s thickness – that develop in a trillionth of a second. (K.-A. Duerloo/Stanford)

    Electron Camera Reveals Ultrafast Motions

    Previous analyses showed that single layers of molybdenum disulfide have a wrinkled surface. However, these studies only provided a static picture. The new study reveals for the first time how surface ripples form and evolve in response to laser light.

    Researchers at SLAC placed their monolayer samples, which were prepared by Linyou Cao’s group at North Carolina State University, into a beam of very energetic electrons. The electrons, which come bundled in ultrashort pulses, scatter off the sample’s atoms and produce a signal on a detector that scientists use to determine where atoms are located in the monolayer. This technique is called ultrafast electron diffraction.

    The team then used ultrashort laser pulses to excite motions in the material, which cause the scattering pattern to change over time.

    “Combined with theoretical calculations, these data show how the light pulses generate wrinkles that have large amplitudes – more than 15 percent of the layer’s thickness – and develop extremely quickly, in about a trillionth of a second. This is the first time someone has visualized these ultrafast atomic motions,” Lindenberg said.

    Once scientists better understand monolayers of different materials, they could begin putting them together and engineer mixed materials with completely new optical, mechanical, electronic and chemical properties.

    The research was supported by DOE’s Office of Science, the SLAC UED/UEM program development fund, the German National Academy of Sciences, and the U.S. National Science Foundation.

    4

    To study ultrafast atomic motions in a single layer of molybdenum disulfide, researchers followed a pump-probe approach: They excited motions with a laser pulse (pump pulse, red) and probed the laser-induced structural changes with a subsequent electron pulse (probe pulse, blue). The electrons of the probe pulse scatter off the monolayer’s atoms (blue and yellow spheres) and form a scattering pattern on the detector – a signal the team used to determine the monolayer structure. By recording patterns at different time delays between the pump and probe pulses, the scientists were able to determine how the atomic structure of the molybdenum disulfide film changed over time. (SLAC National Accelerator Laboratory)

    Citation: E. M. Mannebach et al., Nano Letters, 31 August 2015 (10.1021/acs.nanolett.5b02805)

    Press Office Contact: Andrew Gordon, agordon@slac.stanford.edu, (650) 926-2282

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
    i1

     
  • richardmitnick 2:30 pm on August 26, 2015 Permalink | Reply
    Tags: , Catalyst technology,   

    From PNNL: “Scientists Discover Precise Location of Active Sites on Popular Catalyst” 

    PNNL BLOC
    PNNL Lab

    August 2015
    No Writer Credit

    1
    Experimental work with vanadium oxide catalysts relied on sophisticated spectroscopy and chemical structure calculations to establish a relationship between specific sites on the catalysts and the degree of activity they bring out in a reaction. The work was published in the July 2, 2015, issue of ACS Catalysis and featured on the cover. Posted with permission from ACS Catalysis, July 2, 2015, 5(7). Copyright 2015 American Chemical Society.

    Results: If you want to change a situation, it’s often best to get to the heart of the matter. For chemists, this often means delving into the active sites of catalysts, which speed the reactions behind billions of dollars worth of chemicals and other products. Active sites are where the reaction actually happens. If active sites work slowly or fail quickly, the result is higher costs and lower production rates. To make better active sites, scientists need to see the sites. For the first time, a team led by researchers at Pacific Northwest National Laboratory saw the active sites on a well-known vanadium-based catalyst.

    In addition to the PNNL staff, the team included experts from Washington State University, the University of Alabama, and the Dalian Institute of Chemical Physics, Chinese Academy of Sciences.

    Why It Matters: Fast. Stable. Efficient. These are the hallmarks of a good catalyst, one that can produce needed products without excessive costs or wastes. The results from this study could help researchers design such catalysts. How? By finding ways to create more active sites or protect existing sites from degrading during such reactions — or both.

    Methods: In the experiments, the researchers dispersed or spread the vanadium oxide catalyst on a support of titanium dioxide to create a relatively large surface area with more reactive sites. They used a magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy technology at EMSL, the Department of Energy’s Environmental Molecular Sciences Laboratory, to obtain detailed information about the structures of active species as they exist on the titanium dioxide support.

    “Using an ultra-high magnetic field with fast spinning enabled the team to observe five types of surface vanadium oxide structures that exist when supported on the surfaces of titanium dioxide,” said Dr. Jian Zhi Hu, a PNNL scientist and the team’s lead.

    The scientists correlated the various peaks observed in the NMR spectra with the catalysts’ reactivity for an oxidation reaction that removes a hydrogen atom from methanol. Next, using computational methods, they predicted which peaks in the NMR spectra corresponded with the specific vanadium oxide geometries. In this way, the scientists determined which structures on the vanadium oxide surface do the best job of initiating and sustaining reactions.

    See the full article here.

    Please help promote STEM in your local schools.
    STEM Icon

    Stem Education Coalition

    Pacific Northwest National Laboratory (PNNL) is one of the United States Department of Energy National Laboratories, managed by the Department of Energy’s Office of Science. The main campus of the laboratory is in Richland, Washington.

    PNNL scientists conduct basic and applied research and development to strengthen U.S. scientific foundations for fundamental research and innovation; prevent and counter acts of terrorism through applied research in information analysis, cyber security, and the nonproliferation of weapons of mass destruction; increase the U.S. energy capacity and reduce dependence on imported oil; and reduce the effects of human activity on the environment. PNNL has been operated by Battelle Memorial Institute since 1965.

    i1

     
  • richardmitnick 10:40 am on July 30, 2015 Permalink | Reply
    Tags: , Catalyst technology, , ,   

    From MIT: “How to look for a few good catalysts” 


    MIT News

    July 30, 2015
    David L. Chandler

    New research shows non-wetting surfaces promote chemical reaction rates.

    1
    Materials that have good wetting properties, as illustrated on the left, where droplets spread out flat, tend to have hydroxyl groups attached to the surface, which inhibits catalytic activity. Materials that repel water, as shown at right, where droplets form sharp, steep boundaries, are more conducive to catalytic activity, as shown by the reactions among small orange molecules. Illustration: Xiao Renshaw Wang

    Two key physical phenomena take place at the surfaces of materials: catalysis and wetting. A catalyst enhances the rate of chemical reactions; wetting refers to how liquids spread across a surface.

    Now researchers at MIT and other institutions have found that these two processes, which had been considered unrelated, are in fact closely linked. The discovery could make it easier to find new catalysts for particular applications, among other potential benefits.

    “What’s really exciting is that we’ve been able to connect atomic-level interactions of water and oxides on the surface to macroscopic measurements of wetting, whether a surface is hydrophobic or hydrophilic, and connect that directly with catalytic properties,” says Yang Shao-Horn, the W.M. Keck Professor of Energy at MIT and a senior author of a paper describing the findings in the Journal of Physical Chemistry C. The research focused on a class of oxides called perovskites that are of interest for applications such as gas sensing, water purification, batteries, and fuel cells.

    Since determining a surface’s wettability is “trivially easy,” says senior author Kripa Varanasi, an associate professor of mechanical engineering, that determination can now be used to predict a material’s suitability as a catalyst. Since researchers tend to specialize in either wettability or catalysis, this produces a framework for researchers in both fields to work together to advance understanding, says Varanasi, whose research focuses primarily on wettability; Shao-Horn is an expert on catalytic reactions.

    “We show how wetting and catalysis, which are both surface phenomena, are related,” Varanasi says, “and how electronic structure forms a link between both.”

    While both effects are important in a variety of industrial processes and have been the subject of much empirical research, “at the molecular level, we understand very little about what’s happening at the interface,” Shao-Horn says. “This is a step forward, providing a molecular-level understanding.”

    “It’s primarily an experimental technique” that made the new understanding possible, explains Kelsey Stoerzinger, an MIT graduate student and the paper’s lead author. While most attempts to study such surface science use instruments requiring a vacuum, this team used a device that could study the reactions in humid air, at room temperature, and with varying degrees of water vapor present. Experiments using this system, called ambient pressure X-ray photoelectron spectroscopy, revealed that the reactivity with water is key to the whole process, she says.

    The water molecules break apart to form hydroxyl groups — an atom of oxygen bound to an atom of hydrogen — bonded to the material’s surface. These reactive compounds, in turn, are responsible for increasing the wetting properties of the surface, while simultaneously inhibiting its ability to catalyze chemical reactions. Therefore, for applications requiring high catalytic activity, the team found, a key requirement is that the surface be hydrophobic, or non-wetting.

    “Ideally, this understanding helps us design new catalysts,” Stoerzinger says. If a given material “has a lower affinity for water, it has a higher affinity for catalytic activity.”

    Shao-Horn notes that this is an initial finding, and that “extension of these trends to broader classes of materials and ranges of hydroxyl affinity requires further investigation.” The team has already begun further exploration of these areas. This research, she says, “opens up the space of materials and surfaces we might think about” for both catalysis and wetting.

    The research team also included graduate student Wesley Hong, visiting scientist Livia Giordano, and postdocs Yueh-Lin Lee and Gisele Azimi at MIT; Ethan Crumlin and Hendrik Bluhm at Lawrence Berkeley National Laboratory; and Michael Biegalski at Oak Ridge National Laboratory. The work was supported by the National Science Foundation and the U.S. Department of Energy.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

     
  • richardmitnick 8:49 am on April 2, 2015 Permalink | Reply
    Tags: , Catalyst technology, ,   

    From SLAC: “Scientists Track Ultrafast Creation of a Catalyst with X-ray Laser” 


    SLAC Lab

    April 1, 2015

    Chemical Transformations Driven by Light Provide Key Insight to Steps in Solar-energy Conversion

    1
    This artistic rendering shows an iron-centered molecule that is severed by laser light (upper left). Within hundreds of femtoseconds, or quadrillionths of a second, a molecule of ethanol from a solvent rushes in (bottom right) to bond with the iron-centered molecule. (SLAC National Accelerator Laboratory)

    An international team has for the first time precisely tracked the surprisingly rapid process by which light rearranges the outermost electrons of a metal compound and turns it into an active catalyst – a substance that promotes chemical reactions.

    The results, published April 1 in Nature, could help in the effort to develop novel catalysts to efficiently produce fuel using sunlight. The research was performed with an X-ray laser at the Department of Energy’s SLAC National Accelerator Laboratory.

    “We were able to determine how light rearranges the outermost electrons of the compound on timescales down to a few hundred femtoseconds, or quadrillionths of a second,” said Philippe Wernet, a scientist at Helmholtz-Zentrum Berlin for Materials and Energy who led the experiment.

    Researchers hope that learning these details will allow them to develop rules for predicting and controlling the short-lived early steps in important reactions, including the ones plants use to turn sunlight and water into fuel during photosynthesis. Scientists are seeking to replicate these natural processes to produce hydrogen fuel from sunlight and water, for example, and to master the chemistry required to produce other renewable fuels.

    “The eventual goal is to design chemical reactions that behave exactly the way you want them to,” Wernet said.

    In the experiment at SLAC’s Linac Coherent Light Source, a DOE Office of Science User Facility, the scientists studied a yellowish fluid called iron pentacarbonyl, which consists of carbon monoxide “spurs” surrounding a central iron atom. It is a basic building block for more complex compounds and also provides a simple model for studying light-induced chemical reactions.

    SLAC LCLS Inside
    LCLS

    Researchers had known that exposing this iron compound to light can cleave off one of the five carbon monoxide spurs, causing the molecule’s remaining electrons to rearrange. The arrangement of the outermost electrons determines the molecule’s reactivity – including whether it might make a good catalyst – and also informs how reactions unfold.

    What wasn’t well understood was just how quickly this light-triggered transformation occurs and which short-lived intermediate states the molecule goes through on its way to becoming a stable product.

    At LCLS, the scientists struck a thin stream of the iron compound, which was mixed into an ethanol solvent, with pulses of optical laser light to break up the iron-centered molecules. Just hundreds of femtoseconds later, an ultrabright X-ray pulse probed the molecules’ transformation, which was recorded with sensitive detectors.

    By varying the arrival time of the X-ray pulses, they tracked the rearrangements of the outermost electrons during the molecular transformations.

    Roughly half of the severed molecules enter a chemically reactive state in which their outermost electrons are prone to binding other molecules. As a consequence, they either reconnect with the severed part or bond with an ethanol molecule to form a new compound. In other cases the outermost electrons in the molecule stabilize themselves in a configuration that makes the molecule non-reactive. All of these changes were observed within the time it takes light to travel a few thousandths of an inch.

    “To see this happen so quickly was extremely surprising,” Wernet said.

    Several years’ worth of data analysis and theoretical work were integral to the study, he said. The next step is to move on from model compounds to LCLS studies of the actual molecules used to make solar fuels.

    “This was a really exciting experiment, as it was the first time we used the LCLS to study chemistry in a liquid compound,” said Josh Turner, a SLAC staff scientist who participated in the experiment. “The LCLS is unique in the world in its ability to resolve these types of ultrafast processes in the right energy range for this compound.”

    SLAC’s Kelly Gaffney, a chemist who contributed expertise in how the changing arrangement of electrons steered the chemical reactions, said, “This work helps set the stage for future studies at LCLS and shows how cooperation across different research areas at SLAC enables broader and better science.”

    In addition to researchers from Helmholtz-Zentrum Berlin for Materials and Energy and LCLS, other scientists who assisted in the study were from: SLAC’s Stanford Synchrotron Radiation Lightsource; the SLAC and Stanford PULSE Institute; University of Potsdam, Max Planck Institute for Biophysical Chemistry, Goettingen University and DESY lab in Germany; Stockholm University and MAX-lab in in Sweden; Utrecht University in the Netherlands; Paul Scherrer Institute in Switzerland; and the University of Pennsylvania.

    This work was supported by the Volkswagen Foundation, the Swedish Research Council, the Carl Tryggers Foundation, the Magnus Bergvall Foundation, Collaborative Research Centers of the German Science Foundation and the Helmholtz Virtual Institute “Dynamic Pathways in Multidimensional Landscapes,” and the U.S. Department of Energy Office of Science.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.
    i1

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
Follow

Get every new post delivered to your Inbox.

Join 549 other followers

%d bloggers like this: