Researchers at CalTech and Berkeley Lab Discover New materials that could turn “water into the fuel of the future”


Water for Fuel 170306151722_1_900x600New materials are created through deposition onto disks, which are then tested to determine their properties. Credit: Caltech

 

California Institute of Technology Summary: Combining computational with experimental approaches, researchers identify 12 new materials with potential use in solar fuels generators.

Researchers at Caltech and Lawrence Berkeley National Laboratory (Berkeley Lab) have — in just two years — nearly doubled the number of materials known to have potential for use in solar fuels.

They did so by developing a process that promises to speed the discovery of commercially viable solar fuels that could replace coal, oil, and other fossil fuels.

Solar fuels, a dream of clean-energy research, are created using only sunlight, water, and carbon dioxide (CO2). Researchers are exploring a range of target fuels, from hydrogen gas to liquid hydrocarbons, and producing any of these fuels involves splitting water.

Each water molecule is comprised of an oxygen atom and two hydrogen atoms. The hydrogen atoms are extracted, and then can be reunited to create highly flammable hydrogen gas or combined with CO2 to create hydrocarbon fuels, creating a plentiful and renewable energy source. The problem, however, is that water molecules do not simply break down when sunlight shines on them — if they did, the oceans would not cover most of the planet. They need a little help from a solar-powered catalyst.

To create practical solar fuels, scientists have been trying to develop low-cost and efficient materials, known as photoanodes, that are capable of splitting water using visible light as an energy source. Over the past four decades, researchers identified only 16 of these photoanode materials. Now, using a new high-throughput method of identifying new materials, a team of researchers led by Caltech’s John Gregoire and Berkeley Lab’s Jeffrey Neaton and Qimin Yan have found 12 promising new photoanodes.

A paper about the method and the new photoanodes appears the week of March 6 in the online edition of the Proceedings of the National Academy of Sciences. The new method was developed through a partnership between the Joint Center for Artificial Photosynthesis (JCAP) at Caltech, and Berkeley Lab’s Materials Project, using resources at the Molecular Foundry and the National Energy Research Scientific Computing Center (NERSC).

“This integration of theory and experiment is a blueprint for conducting research in an increasingly interdisciplinary world,” says Gregoire, JCAP thrust coordinator for Photoelectrocatalysis and leader of the High Throughput Experimentation group. “It’s exciting to find 12 new potential photoanodes for making solar fuels, but even more so to have a new materials discovery pipeline going forward.”

“What is particularly significant about this study, which combines experiment and theory, is that in addition to identifying several new compounds for solar fuel applications, we were also able to learn something new about the underlying electronic structure of the materials themselves,” says Neaton, the director of the Molecular Foundry.

Previous materials discovery processes relied on cumbersome testing of individual compounds to assess their potential for use in specific applications. In the new process, Gregoire and his colleagues combined computational and experimental approaches by first mining a materials database for potentially useful compounds, screening it based on the properties of the materials, and then rapidly testing the most promising candidates using high-throughput experimentation.

In the work described in the PNAS paper, they explored 174 metal vanadates — compounds containing the elements vanadium and oxygen along with one other element from the periodic table.

The research, Gregoire says, reveals how different choices for this third element can produce materials with different properties, and reveals how to “tune” those properties to make a better photoanode.

“The key advance made by the team was to combine the best capabilities enabled by theory and supercomputers with novel high throughput experiments to generate scientific knowledge at an unprecedented rate,” Gregoire says.


Story Source:

Materials provided by California Institute of Technology. Original written by Robert Perkins. Note: Content may be edited for style and length.


Journal Reference:

  1. Qimin Yan, Jie Yu, Santosh K. Suram, Lan Zhou, Aniketa Shinde, Paul F. Newhouse, Wei Chen, Guo Li, Kristin A. Persson, John M. Gregoire, and Jeffrey B. Neaton. Solar fuels photoanode materials discovery by integrating high-throughput theory and experiment. PNAS, March 2017 DOI: 10.1073/pnas.1619940114
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Scientists Determine Precise 3-D Location and Identity of All 23,000 Atoms in a Nanoparticle ~ Cool Video!





The atomic composition of an iron-platinum nanoparticle revealed. This is an overview of the 3-D positions of individual atoms, with iron atoms in red and platinum atoms in blue. It then splits apart into the large and small grains that compose the nanoparticle. (Credit: Colin Ophus and Florian Niekiel, Berkeley Lab) Niekiel, Berkeley Lab)

Berkeley Lab researchers help to map iron-platinum particle in unprecedented detail

Scientists used one of the world’s most powerful electron microscopes to map the precise location and chemical type of 23,000 atoms in an extremely small particle made of iron and platinum.

The 3-D reconstruction reveals the arrangement of atoms in unprecedented detail, enabling the scientists to measure chemical order and disorder in individual grains, which sheds light on the material’s properties at the single-atom level. Insights gained from the particle’s structure could lead to new ways to improve its magnetic performance for use in high-density, next-generation hard drives.

Watch Video

What’s more, the technique used to create the reconstruction, atomic electron tomography (which is like an incredibly high-resolution CT scan), lays the foundation for precisely mapping the atomic composition of other useful nanoparticles. This could reveal how to optimize the particles for more efficient catalysts, stronger materials, and disease-detecting fluorescent tags.

Microscopy data was obtained and analyzed by scientists from the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) at the Molecular Foundry, in collaboration with Foundry users from UCLA, Oak Ridge National Laboratory, and the United Kingdom’s University of Birmingham. The research is reported Feb. 2 in the journal Nature.

Atoms are the building blocks of matter, and the patterns in which they’re arranged dictate a material’s properties. These patterns can also be exploited to greatly improve a material’s function, which is why scientists are eager to determine the 3-D structure of nanoparticles at the smallest scale possible.

“Our research is a big step in this direction. We can now take a snapshot that shows the positions of all the atoms in a nanoparticle at a specific point in its growth. This will help us learn how nanoparticles grow atom by atom, and it sets the stage for a materials-design approach starting from the smallest building blocks,” says Mary Scott, who conducted the research while she was a Foundry user, and who is now a staff scientist. Scott and fellow Foundry scientists Peter Ercius and Colin Ophus developed the method in close collaboration with Jianwei Miao, a UCLA professor of physics and astronomy.

Their nanoparticle reconstruction builds on an achievement they reported last year in which they measured the coordinates of more than 3,000 atoms in a tungsten needle to a precision of 19 trillionths of a meter (19 picometers), which is many times smaller than a hydrogen atom. Now, they’ve taken the same precision, added the ability to distinguish different elements, and scaled up the reconstruction to include tens of thousands of atoms.

Importantly, their method maps the position of each atom in a single, unique nanoparticle. In contrast, X-ray crystallography and cryo-electron microscopy plot the average position of atoms from many identical samples. These methods make assumptions about the arrangement of atoms, which isn’t a good fit for nanoparticles because no two are alike.

“We need to determine the location and type of each atom to truly understand how a nanoparticle functions at the atomic scale,” says Ercius.

A TEAM approach

TEAM

The scientists’ latest accomplishment hinged on the use of one of the highest-resolution transmission electron microscopes in the world, called TEAM I. It’s located at the National Center for Electron Microscopy, which is a Molecular Foundry facility. The microscope scans a sample with a focused beam of electrons, and then measures how the electrons interact with the atoms in the sample. It also has a piezo-controlled stage that positions samples with unmatched stability and position-control accuracy.

The researchers began growing an iron-platinum nanoparticle from its constituent elements, and then stopped the particle’s growth before it was fully formed. They placed the “partially baked” particle in the TEAM I stage, obtained a 2-D projection of its atomic structure, rotated it a few degrees, obtained another projection, and so on. Each 2-D projection provides a little more information about the full 3-D structure of the nanoparticle.

They sent the projections to Miao at UCLA, who used a sophisticated computer algorithm to convert the 2-D projections into a 3-D reconstruction of the particle. The individual atomic coordinates and chemical types were then traced from the 3-D density based on the knowledge that iron atoms are lighter than platinum atoms. The resulting atomic structure contains 6,569 iron atoms and 16,627 platinum atoms, with each atom’s coordinates precisely plotted to less than the width of a hydrogen atom.

Translating the data into scientific insights

Computer algorithms developed by Colin Ophus enabled the scientists to decipher the atomic structure of the nanoparticle, which shed light on how the atoms arrange themselves into an ordered structure with optimal magnetic properties. (Credit: Marilyn Chung)

Interesting features emerged at this extreme scale after Molecular Foundry scientists used code they developed to analyze the atomic structure. For example, the analysis revealed chemical order and disorder in interlocking grains, in which the iron and platinum atoms are arranged in different patterns. This has large implications for how the particle grew and its real-world magnetic properties. The analysis also revealed single-atom defects and the width of disordered boundaries between grains, which was not previously possible in complex 3-D boundaries.

“The important materials science problem we are tackling is how this material transforms from a highly randomized structure, what we call a chemically-disordered structure, into a regular highly-ordered structure with the desired magnetic properties,” says Ophus.

To explore how the various arrangements of atoms affect the nanoparticle’s magnetic properties, scientists from DOE’s Oak Ridge National Laboratory ran computer calculations on the Titan supercomputer at ORNL—using the coordinates and chemical type of each atom—to simulate the nanoparticle’s behavior in a magnetic field. This allowed the scientists to see patterns of atoms that are very magnetic, which is ideal for hard drives. They also saw patterns with poor magnetic properties that could sap a hard drive’s performance.

“This could help scientists learn how to steer the growth of iron-platinum nanoparticles so they develop more highly magnetic patterns of atoms,” says Ercius.

Adds Scott, “More broadly, the imaging technique will shed light on the nucleation and growth of ordered phases within nanoparticles, which isn’t fully theoretically understood but is critically important to several scientific disciplines and technologies.”

The Molecular Foundry is a DOE Office of Science User Facility. The research was primarily supported by the Department of Energy’s Office of Science.

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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 http://www.lbl.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.

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The Future of Batteries with Venkat Srinivasan: Lawrence Berkeley National Laboratory: Video


 

Lawrence Berkeley National Laboratory battery scientist Venkat Srinivasan chats with Sabin Russell, former San Francisco Chronicle reporter turned Berkeley Lab science writer. They explore the problems that prevent lithium-ion batteries from being widely used in electric, hybrid-electric, and plug-in-hybrid-electric vehicles. Series: “Lawrence Berkeley National Laboratory Summer Lecture Series” [Science] [Show]

Argonne National Laboratory-led projects among $39.8 million in first-round “Exascale” Computing Project awards -Enabled Precision Medicine for Cancer


doe-iii-doeThe U.S. Department of Energy’s (DOE’s) Exascale Computing Project (ECP) today announced its first round of funding with the selection of 15 application development proposals for full funding and seven proposals for seed funding, representing teams from 45 research and academic organizations.

Exascale refers to high-performance computing systems capable of at least a billion billion calculations per second, or a factor of 50 to 100 times faster than the nation’s most powerful supercomputers in use today.

The 15 awards being announced total $39.8 million, targeting advanced modeling and simulation solutions to specific challenges supporting key DOE missions in science, clean energy and national security, as well as collaborations such as the Precision Medicine Initiative with the National Institutes of Health’s National Cancer Institute.

Of the proposals announced that are receiving full funding, two are being led by principal investigators at the DOE’s Argonne National Laboratory:

  1. Computing the Sky at Extreme Scales equips cosmologists with the ability to design foundational simulations to create “virtual universes” on demand at the extreme fidelities demanded by future multi-wavelength sky surveys. The new discoveries that will emerge from the combination of sky surveys and advanced simulation provided by the ECP will shed more light on three key ingredients of our universe: dark energy, dark matter and inflation. All three of these concepts reach beyond the known boundaries of the Standard Model of particle physics.Salman Habib, Principal Investigator, Argonne National Laboratory, with Los Alamos National Laboratory and Lawrence Berkeley National Laboratory.argone-ii-nl-mira_-_blue_gene_q_at_argonne_national_laboratory
  1. Exascale Deep Learning and Simulation Enabled Precision Medicine for Cancer focuses on building a scalable deep neural network code called the CANcer Distributed Learning Environment (CANDLE) that addresses three top challenges of the National Cancer Institute: understanding the molecular basis of key protein interactions, developing predictive models for drug response and automating the analysis and extraction of information from millions of cancer patient records to determine optimal cancer treatment strategies.Rick Stevens, Principal Investigator, Argonne National Laboratory, with Los Alamos National Laboratory, Lawrence Livermore National Laboratory, Oak Ridge National Laboratory and the National Cancer Institute.

Additionally, a third project led by Argonne will be receiving seed funding:

  1. Multiscale Coupled Urban Systems will create an integrated modeling framework comprising data curation, analytics, modeling and simulation components that will equip city designers, planners and managers to scientifically develop and evaluate solutions to issues that affect cities now and in the future. The framework will focus first on integrating urban atmosphere and infrastructure heat exchange and air flow; building energy demand at district or city-scale, generation and use; urban dynamics and socioeconomic models; population mobility and transportation; and hooks to expand to include energy systems (biofuels, electricity and natural gas) and water resources.Charlie Catlett, Principal Investigator, Argonne National Laboratory, with Lawrence Berkeley National Laboratory, National Renewable Energy Laboratory, Oak Ridge National Laboratory and Pacific Northwest National Laboratory.

The application efforts will help guide DOE’s development of a U.S. exascale ecosystem as part of President Obama’s National Strategic Computing Initiative. DOE, the U.S. Department of Defense and the National Science Foundation have been designated as lead agencies, and ECP is the primary DOE contribution to the initiative.

The ECP’s multiyear mission is to maximize the benefits of high-performance computing for U.S. economic competitiveness, national security and scientific discovery. In addition to applications, the DOE project addresses hardware, software, platforms and workforce development needs critical to the effective development and deployment of future exascale systems.

argone-nl-090115-114727Leadership of the ECP comes from six DOE national laboratories: the Office of Science’s Oak Ridge, Argonne and Lawrence Berkeley national labs and the National Nuclear Security Administration’s (NNSA’s) Lawrence Livermore, Los Alamos and Sandia national labs.

The Exascale Computing Project is a collaborative effort of two DOE organizations — the Office of Science and the NNSA. As part of President Obama’s National Strategic Computing initiative, ECP was established to develop a capable exascale ecosystem, encompassing applications, system software, hardware technologies and architectures, and workforce development to meet the scientific and national security mission needs of DOE in the mid-2020s timeframe.

Established by Congress in 2000, NNSA is a semi-autonomous agency within DOE responsible for enhancing national security through the military application of nuclear science. NNSA maintains and enhances the safety, security, and effectiveness of the U.S. nuclear weapons stockpile without nuclear explosive testing; works to reduce the global danger from weapons of mass destruction; provides the U.S. Navy with safe and effective nuclear propulsion; and responds to nuclear and radiological emergencies in the United States and abroad.

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science.

The U.S. Department of Energy’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, visit the Office of Science website.

Berkeley Lab Researchers: 5 Nanoscience Research Projects That Could Deliver Big Results


south-africa-ii-nanotechnology-india-brazil_261.jpgFrom energy efficiency to carbon capture, Berkeley Lab scientists are on it.

Berkeley Lab researchers are using the science of the very small to help solve big challenges. That’s because, at the nanoscale—the scale of molecules and proteins—new and exciting properties emerge that can possibly be put to use.

Here are five projects, now underway and recently highlighted in the News Center, which promise big results from the smallest of building blocks:

1. A DIY paint-on coating for energy efficient windows

This “cool” DIY retrofit tech could improve the energy efficiency of windows and save money. Researchers are developing a polymer-based heat-reflective coating that makes use of the unusual molecular architecture of a polymer.

It has the potential to be painted on windows at one-tenth the cost of current retrofit approaches. Window films on the market today reflect infrared solar energy back to the sky while allowing visible light to pass through, but a professional contractor is needed to install them. A low-cost option could significantly expand adoption and result in potential annual energy savings equivalent to taking 5 million cars off the road.

 

2. Nanowires that move data at light speed

Researchers have found a new way to produce nanoscale wires that can serve as tiny, tunable lasers. The excellent performance of these tiny lasers is promising for the field of optoelectronics, which is focused on combining electronics and light to transmit data, among other applications. Miniaturizing lasers to the nanoscale could further revolutionize computing, bringing light-speed data transmission to desktop, and ultimately, handheld computing devices.

 

3. Nano sponges that fight climate change

MOF

Scientists are developing nano sponges that could capture carbon from power plants before it enters the atmosphere. Initial tests show the hybrid membrane, composed of nano-sized cages (called metal-organic frameworks) and a polymer, is eight times more carbon dioxide permeable than membranes composed only of the polymer.

Boosting carbon dioxide permeability is a big goal in efforts to develop carbon capture materials that are energy efficient and cost competitive. Watch this video for more on this technology.

 

 

4. Custom-made chemical factories

4-JACS-Press-release_ca

Scientists have recently reengineered a building block of a nanocompartment that occurs naturally in bacteria, greatly expanding the potential of nanocompartments to serve as custom-made chemical factories. Researchers hope to tailor this new use to produce high-value chemical products, such as medicines, on demand.

The sturdy nanocompartments are formed by hundreds of copies of just three different types of proteins. Their natural counterparts, known as bacterial microcompartments, encase a wide variety of enzymes that carry out highly specialized chemistry in bacteria.

 

5. Nanotubes that assemble themselves

5-peptoid-nanotube-cropped

Researchers have discovered a family of nature-inspired polymers that, when placed in water, spontaneously assemble into hollow crystalline nanotubes. What’s more, the nanotubes can be tuned to all have the same diameter of between five and ten nanometers. Controlling the diameter of nanotubes, and the chemical groups exposed in their interior, enables scientists to control what goes through. Nanotubes have the potential to be incredibly useful, from delivering cancer-fighting drugs inside cells to desalinating seawater.

 

The Science of Small Revealed Using a Penny

Just how small can nanoscience get? Here’s a great example using an American penny from the Molecular Foundry.

In this video, the letters that spell Molecular Foundry were written with a beam of electrons fired at the surface. The smallest feature is 20 nanometers, or roughly 100 atoms. As the video zooms out, you lose sight of Molecular Foundry and see the Berkeley Lab logo, which was written with a beam of charged gallium atoms. As you continue to zoom out, you see an 18 hour timelapse of Abraham Lincoln’s face, again written with gallium atoms. Finally, all of this is done within the Lincoln Memorial side of the penny as it is removed from the focused ion beam.

Photolithography, which literally means writing with light, is the foundation for most top-down fabrication of things like microprocessors. However, because of something called the diffraction limit, photolithography is limited to devices that have features no smaller than the wavelength of the light used, often in the 100s of nanometers. As a result, things smaller than light like atoms and electrons must be used.

 

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U.S. Department of Energy’s Lawrence Berkeley National Laboratory: Scientists grow atomically thin transistors and circuits


auto thin trans 072016 berkeleylabsThis schematic shows the chemical assembly of two-dimensional crystals. Graphene is first etched into channels and the TMDC molybdenum disulfide (MoS2) begins to nucleate around the edges and within the channel. On the edges, MoS2 slightly …more

In an advance that helps pave the way for next-generation electronics and computing technologies—and possibly paper-thin gadgets —scientists with the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) developed a way to chemically assemble transistors and circuits that are only a few atoms thick.

What’s more, their method yields functional structures at a scale large enough to begin thinking about real-world applications and commercial scalability.

They report their research online July 11 in the journal Nature Nanotechnology.

The scientists controlled the synthesis of a transistor in which narrow channels were etched onto conducting graphene, and a semiconducting material called a transition-metal dichalcogenide, or TMDC, was seeded in the blank channels. Both of these materials are single-layered crystals and atomically thin, so the two-part assembly yielded electronic structures that are essentially two-dimensional. In addition, the synthesis is able to cover an area a few centimeters long and a few millimeters wide.

“This is a big step toward a scalable and repeatable way to build atomically thin electronics or pack more computing power in a smaller area,” says Xiang Zhang, a senior scientist in Berkeley Lab’s Materials Sciences Division who led the study.

Zhang also holds the Ernest S. Kuh Endowed Chair at the University of California (UC) Berkeley and is a member of the Kavli Energy NanoSciences Institute at Berkeley. Other scientists who contributed to the research include Mervin Zhao, Yu Ye, Yang Xia, Hanyu Zhu, Siqi Wang, and Yuan Wang from UC Berkeley as well as Yimo Han and David Muller from Cornell University.

Their work is part of a new wave of research aimed at keeping pace with Moore’s Law, which holds that the number of transistors in an integrated circuit doubles approximately every two years. In order to keep this pace, scientists predict that integrated electronics will soon require transistors that measure less than ten nanometers in length.

Transistors are electronic switches, so they need to be able to turn on and off, which is a characteristic of semiconductors. However, at the nanometer scale, likely won’t be a good option. That’s because silicon is a bulk material, and as electronics made from silicon become smaller and smaller, their performance as switches dramatically decreases, which is a major roadblock for future electronics.

Researchers have looked to two-dimensional crystals that are only one molecule thick as alternative materials to keep up with Moore’s Law. These crystals aren’t subject to the constraints of silicon.

In this vein, the Berkeley Lab scientists developed a way to seed a single-layered semiconductor, in this case the TMDC molybdenum disulfide (MoS2), into channels lithographically etched within a sheet of conducting graphene. The two atomic sheets meet to form nanometer-scale junctions that enable graphene to efficiently inject current into the MoS2. These junctions make atomically thin transistors.

“This approach allows for the chemical assembly of electronic circuits, using two-dimensional materials, which show improved performance compared to using traditional metals to inject current into TMDCs,” says Mervin Zhao, a lead author and Ph.D. student in Zhang’s group at Berkeley Lab and UC Berkeley.

Optical and electron microscopy images, and spectroscopic mapping, confirmed various aspects related to the successful formation and functionality of the two-dimensional transistors.

In addition, the scientists demonstrated the applicability of the structure by assembling it into the logic circuitry of an inverter. This further underscores the technology’s ability to lay the foundation for a chemically assembled atomic computer, the scientists say.

“Both of these two-dimensional crystals have been synthesized in the wafer scale in a way that is compatible with current semiconductor manufacturing. By integrating our technique with other growth systems, it’s possible that future computing can be done completely with atomically thin crystals,” says Zhao.

Explore further: Excitonic dark states shed light on TMDC atomic layers

More information: Large-scale chemical assembly of atomically thin transistors and circuits, Nature Nanotechnology, DOI: 10.1038/nnano.2016.115

Read more at: http://phys.org/news/2016-07-scientists-atomically-thin-transistors-circuits.html#jCp

Read more at: http://phys.org/news/2016-07-scientists-atomically-thin-transistors-circuits.html#jCp

Graphene-Wapped Nanocrystals Power A New Fuel Cell Design


newfuelcelld 031516
A powdery mixture of graphene-wrapped magnesium nanocrystals, produced at Berkeley Lab, is stable in air. The mixture’s energy properties show promise for use in hydrogen fuel cells. Credit: Eun Seon Cho/Berkeley Lab

Hydrogen is the lightest and most plentiful element on Earth and in our universe. So it shouldn’t be a big surprise that scientists are pursuing hydrogen as a clean, carbon-free, virtually limitless energy source for cars and for a range of other uses, from portable generators to telecommunications towers—with water as the only byproduct of combustion.

While there remain scientific challenges to making -based energy sources more competitive with current automotive propulsion systems and other energy technologies, researchers at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have developed a new materials recipe for a battery-like cell—which surrounds hydrogen-absorbing magnesium nanocrystals with atomically thin graphene sheets—to push its performance forward in key areas.

The graphene shields the nanocrystals from oxygen and moisture and contaminants, while tiny, natural holes allow the smaller hydrogen molecules to pass through. This filtering process overcomes common problems degrading the performance of metal hydrides for .

These graphene-encapsulated magnesium crystals act as “sponges” for hydrogen, offering a very compact and safe way to take in and store hydrogen. The nanocrystals also permit faster fueling, and reduce the overall “tank” size.

“Among metal hydride-based materials for hydrogen storage for vehicle applications, our materials have good performance in terms of capacity, reversibility, kinetics and stability,” said Eun Seon Cho, a postdoctoral researcher at Berkeley Lab and lead author of a study related to the new fuel cell formula, published recently in Nature Communications.

New fuel cell design powered by graphene-wrapped nanocrystals
Thin sheets of graphene oxide (red sheets) have natural, atomic-scale defects that allow hydrogen gas molecules to pass through while blocking larger molecules such as oxygen (O2) and water (H2O). Berkeley Lab researchers encapsulated …more

In a hydrogen fuel cell-powered vehicle using these materials, known as a “metal hydride” (hydrogen bound with a metal) fuel cell, hydrogen gas pumped into a vehicle would be chemically absorbed by the magnesium nanocrystaline powder and rendered safe at low pressures.

Jeff Urban, a Berkeley Lab staff scientist and co-author, said, “This work suggests the possibility of practical hydrogen storage and use in the future. I believe that these materials represent a generally applicable approach to stabilizing reactive materials while still harnessing their unique activity—concepts that could have wide-ranging applications for batteries, catalysis, and energetic materials.”

The research, conducted at Berkeley Lab’s Molecular Foundry and Advanced Light Source, is part of a National Lab Consortium, dubbed HyMARC (Hydrogen Materials—Advanced Research Consortium) that seeks safer and more cost-effective hydrogen storage, and Urban is Berkeley Lab’s lead scientist for that effort.

The U.S. market share for all electric-drive vehicles in 2015, including full-electric, hybrids and plug-in hybrid vehicles, was 2.87 percent, which amounts to about 500,000 electric-drive vehicles out of total vehicle sales of about 17.4 million, according to statistics reported by the Electric Drive Transportation Association, a trade association promoting electric-drive vehicles.

Hydrogen-fuel-cell vehicles haven’t yet made major in-roads in vehicle sales, though several major auto manufacturers including Toyota, Honda, and General Motors, have invested in developing hydrogen fuel-cell vehicles. Indeed, Toyota released a small-production model called the Mirai, which uses compressed-hydrogen tanks, last year in the U.S.

A potential advantage for hydrogen-fuel-cell vehicles, in addition to their reduced environmental impact over standard-fuel vehicles, is the high specific energy of hydrogen, which means that can potentially take up less weight than other battery systems and fuel sources while yielding more electrical energy.

A measure of the energy storage capacity per weight of hydrogen fuel cells, known as the “gravimetric energy density,” is roughly three times that of gasoline. Urban noted that this important property, if effectively used, could extend the total vehicle range of hydrogen-based transportation, and extend the time between refueling for many other applications, too.

More R&D is needed to realize higher-capacity hydrogen storage for long-range vehicle applications that exceed the performance of existing electric-vehicle batteries, Cho said, and other applications may be better suited for hydrogen fuel cells in the short term, such as stationary power sources, forklifts and airport vehicles, portable power sources like laptop battery chargers, portable lighting, water and sewage pumps and emergency services equipment.

Cho said that a roadblock to metal hydride storage has been a relatively slow rate in taking in (absorption) and giving out (desorption) hydrogen during the cycling of the units. In fuel cells, separate chemical reactions involving hydrogen and oxygen produce a flow of electrons that are channeled as electric current, creating water as a byproduct.

The tiny size of the graphene-encapsulated nanocrystals created at Berkeley Lab, which measure only about 3-4 nanometers, or billionths of a meter across, is a key in the new fuel cell materials’ fast capture and release of hydrogen, Cho said, as they have more surface area available for reactions than the same material would at larger sizes.

Another key is protecting the magnesium from exposure to air, which would render it unusable for the fuel cell, she added.

Working at The Molecular Foundry, researchers found a simple, scalable and cost-effective “one pan” technique to mix up the graphene sheets and magnesium oxide nanocrystals in the same batch. They later studied the coated nanocrystals’ structure using X-rays at Berkeley Lab’s Advanced Light Source. The X-ray studies showed how pumped into the fuel cell mixture reacted with the magnesium nanocrystals to form a more stable molecule called magnesium hydride while locking out oxygen from reaching the magnesium.

“It is stable in air, which is important,” Cho said.

Next steps in the research will focus on using different types of catalysts—which can improve the speed and efficiency of chemical reactions—to further improve the fuel cell’s conversion of electrical current, and in studying whether different types of material can also improve the fuel cell’s overall capacity, Cho said.

Explore further: Hydrogen released to fuel cell more quickly when stored in metal nanoparticles

More information: Eun Seon Cho et al. Graphene oxide/metal nanocrystal multilaminates as the atomic limit for safe and selective hydrogen storage, Nature Communications (2016). DOI: 10.1038/ncomms10804

New Kind of Nanowires Designed For Efficient Water Splitting and Solar Energy Storage


Nanowires 020316 bf8802f7297fd2bfea985c26d0b9a636_w1440.jpg

California is committed to 33 percent energy from renewable resources by 2020. With that deadline fast approaching, researchers across the state are busy exploring options.

Solar energy is attractive but for widespread adoption, it requires transformation into a storable form. This week in ACS Central Science, researchers report that nanowires made from multiple metal oxides could put solar ahead in this race.

One way to harness solar power for broader use is through photoelectrochemical (PEC) water splitting that provides hydrogen for fuel cells. Many materials that can perform the reaction exist, but most of these candidates suffer from issues, ranging from efficiency to stability and cost.

Peidong Yang and colleagues designed a system where nanowires from one of the most commonly used materials (TiO2) acts as a “host” for “guest” nanoparticles from another oxide called BiVO4. BiVO4 is a newly introduced material that is among the best ones for absorbing light and performing the water splitting reaction, but does not carry charge well while TiO2 is stable, cheap and an efficient charge carrier but does not absorb light well.

Together with a unique studded nanowire architecture, the new system works better than either material alone.

The authors state their approach can be used to improve the efficiencies of other photoconversion materials.

Synopsis

We report the use of Ta:TiO2|BiVO4 as a photoanode for use in solar water splitting cells. This host−guest system makes use of the favorable band alignment between the two semiconductors. The nanowire architecture allows for simultaneously high light absorption and carrier collection for efficient solar water oxidation.

nanowires II 020316 oc-2015-004025_0008.gif

Metal oxides that absorb visible light are attractive for use as photoanodes in photoelectrosynthetic cells. However, their performance is often limited by poor charge carrier transport. We show that this problem can be addressed by using separate materials for light absorption and carrier transport. Here, we report a Ta:TiO2|BiVO4 nanowire photoanode, in which BiVO4 acts as a visible light-absorber and Ta:TiO2 acts as a high surface area electron conductor. Electrochemical and spectroscopic measurements provide experimental evidence for the type II band alignment necessary for favorable electron transfer from BiVO4 to TiO2. The host–guest nanowire architecture presented here allows for simultaneously high light absorption and carrier collection efficiency, with an onset of anodic photocurrent near 0.2 V vs RHE, and a photocurrent density of 2.1 mA/cm2 at 1.23 V vs RHE.

Introduction


Harnessing energy from sunlight is a means of meeting the large global energy demand in a cost-effective and environmentally benign manner. However, to provide constant and stable power on demand, it is necessary to convert sunlight into an energy storage medium.(1) An example of such a method is the production of hydrogen by photoelectrochemical (PEC) water splitting. The direct splitting of water can be achieved using a single semiconductor; however, due to the voltage requirement of the water splitting reaction and the associated kinetic overpotentials, only wide-band-gap materials can perform overall water splitting, limiting the efficiency due to insufficient light absorption.(2) To address this issue, a dual-band-gap z-scheme system can be utilized, with a semiconductor photoanode and photocathode to perform the respective oxidation and reduction reactions.(3) This approach allows for the use of lower-band-gap materials that can absorb complementary portions of the solar spectrum and yield higher solar-to-fuel efficiencies.(4, 5) In this integrated system, the charge flux is matched in both light absorbers of the photoelectrochemical cell. Therefore, the overall performance is determined by the limiting component. In most photoelectrosynthetic cells, this limiting component is the semiconductor photoanode.(6)
Metal oxides have been heavily researched as photoanode materials since few conventional light absorber materials are stable at the highly oxidizing conditions required for water oxidation.(7) However, the most commonly studied binary oxide, TiO2, has a band gap that is too large to absorb sunlight efficiently (∼3.0 eV), consequently limiting its achievable photocurrent.(8) While promising work has recently been done on stabilizing conventional light absorbers such as Si,(9) GaAs,(10) and InP,(11) the photovoltage obtained by these materials thus far has been insufficient to match with smaller-band-gap photocathode materials such as Si and InP in a dual absorber photoelectrosynthetic cell.(12, 13) Additionally, these materials have high production and processing costs. Small-band-gap metal oxides that absorb visible light and can be inexpensively synthesized, such as WO3, Fe2O3, and BiVO4, are alternative materials that hold promise to overcome these limitations.(14-16) Among these metal oxides, BiVO4 has emerged as one of the most promising materials due to its relatively small optical band gap of ∼2.5 eV and its negative conduction band edge (∼0 V versus RHE).(17, 18) Under air mass 1.5 global (AM1.5G) solar illumination, the maximum achievable photocurrent for water oxidation using BiVO4 is ∼7 mA/cm2.(16) However, the water oxidation photocurrent obtained in practice for BiVO4 is substantially lower than this value, mainly due to poor carrier transport properties, with electron diffusion lengths shorter than the film thickness necessary to absorb a substantial fraction of light.(17)
One approach for addressing this problem is to use two separate materials for the tasks of light absorption and carrier transport. To maximize performance, a conductive and high surface area support material (“host”) is used, which is coated with a highly dispersed visible light absorber (“guest”). This architecture allows for efficient use of absorbed photons due to the proximity of the semiconductor liquid junction (SCLJ). This strategy has been employed in dye sensitized (DSSC) and quantum dot sensitized solar cells (QDSSC).(19, 20) Using a host–guest scheme can improve the performance of photoabsorbing materials with poor carrier transport but relies upon appropriate band alignment between the host and guest. Namely, the electron affinity of the host should be larger, to favor electron transfer from guest to host without causing a significant loss in open-circuit voltage.(21) Nanowire arrays provide several advantages for use as the host material as they allow high surface area loading of the guest material, enhanced light scattering for improved absorption, and one-dimensional electron transport to the back electrode.(22) Therefore, nanowire arrays have been used as host materials in DSSCs, QDSSCs, and hybrid perovskite solar cells.(23-25) In photoelectrosynthetic cells, host–guest architectures have been utilized for oxide photoanodes such as Fe2O3|TiSi2,(26) Fe2O3|WO3,(27) Fe2O3|SnO2,(28) and Fe2TiO5|TiO2.(29) For BiVO4, it has been studied primarily with WO3|BiVO4,(30-32) ZnO|BiVO4,(33) and anatase TiO2|BiVO4.(34) While attractive for its electronic transport properties, ZnO is unstable in aqueous environments, and WO3 has the disadvantage of having a relatively positive flatband potential (∼0.4 V vs RHE)(14) resulting in potential energy losses for electrons as they are transferred from BiVO4 to WO3, thereby limiting the photovoltage of the combined system. Performance in the low potential region is critical for obtaining high efficiency in photoelectrosynthetic cells when coupled to typical p-type photocathode materials such as Si or InP.(12, 13) TiO2 is stable in a wide range of pH and has a relatively negative flat band potential (∼0.2 V vs RHE)(7) which does not significantly limit the photovoltage obtainable from BiVO4, while still providing a driving force for electron transfer. While TiO2 has intrinsically low mobility, doping TiO2 with donor type defects could increase the carrier concentration and thus the conductivity. Indeed, niobium and tantalum doped TiO2 have recently been investigated as potential transparent conductive oxide (TCO) materials.(35, 36) A host material with high carrier concentration could also ensure low contact resistance with the guest material.(37)
Using a solid state diffusion approach based on atomic layer deposition (ALD), we have previously demonstrated the ability to controllably and uniformly dope TiO2.(38) In this study we demonstrate a host–guest approach using Ta-doped TiO2 (Ta:TiO2) nanowires as a host and BiVO4 as a guest material. This host–guest nanowire architecture allows for simultaneously high light absorption and carrier collection efficiency, with an onset of anodic photocurrent near 0.2 V vs RHE, and a photocurrent of 2.1 mA/cm2 at 1.23 V vs RHE. We show that the synergistic effect of the host–guest structure results in higher performance than either pure TiO2 or BiVO4. We also experimentally demonstrate thermodynamically favorable band alignment between TiO2 and BiVO4 using spectroscopic and electrochemical methods, and study the band edge electronic structure of the TiO2 and BiVO4 using X-ray absorption and emission spectroscopies.

 

Article adapted from a American Chemical Society news release. To Read the FULL release, please click on the link provided below.

Publication: TiO2/BiVO4 Nanowire Heterostructure Photoanodes Based on Type II Band Alignment. Resasco, J et al. ACS Central Science (3 February, 2016): Click here to view.

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Must see TV: take a peek inside Nanosys’ Silicon Valley Quantum Dot fab with NBC Learn & Dr. Paul Alivisatos (Berkeley)


QD Images Scale and Size quantum_dots_c

 

Readers’ Note: Dr. Alivisatos (Berkeley) has been a pioneer of ‘nano-cystals’ and their potential applications. Most recently these ‘crystals’ or Quantum Dots have found their way into commercial application for Display Screens. However the much larger vision for QD’s has significant (“game changing”) implications for: Solar Energy, Bio-Medicine, Drug Theranostics & Delivery, Lighting and Hybrid-Materials (Coatings, Paints, Security Inks as examples).  Enjoy the Video ~ Team GNT

Nanosys scientific co-founder and Director of the Lawerence Berkeley National Lab, Dr. Paul Alivisatos, takes NBC Learn on a tour of Nanosys’ Silicon Valley Quantum Dot manufacturing facility.

The section on Nanosys begins at 2:16 – enjoy!

Watch: NanoSys: Quantum Dot Video

Dr Alivisatos, who recently received the 2016 National Medal of Science, talks with NBC reporter Kate Snow about how this amazing nanotechnology that he helped pioneer is changing the way our TVs work today:

SNOW: When quantum dots of different sizes are grouped together by the billions, they produce vivid colors that have changed the way we look at display screens. The initial research, funded by the NSF, has found its way into many applications, including a nanotechnology company called Nanosys, which produces 25 tons of quantum dot materials every year, enough for approximately 6 million 60 inch TVs.

ALIVISATOS: What we have here is a plastic film that contains inside of it quantum dots, very tiny, tiny crystals made out of semiconductors. It actually contains two sizes of nanoparticle – a very small size that emits a green color and a slightly larger size that emits a red color of light.

SNOW: This film is embedded into tablets, televisions, and laptops to enhance their displays with brilliant color.

ALIVISATOS: One of the things that we’ve learned about vision is that we have receptors in our eyes for green, red and blue colors. And if we want a really high quality display, we need to match the light emission from our display to the receptors in our eyes.

Berkeley National Laboratory: Weaving a new story for Nanomaterials (COFS and MOFs)


Nano Weaving RD_COF

There are many different ways to make nano-materials but weaving, the oldest and most enduring method of making fabrics, has not been one of them – until now. An international collaboration led by scientists at the U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) Berkeley, has woven the first three-dimensional covalent organic frameworks (COFs) from helical organic threads. The woven COFs display significant advantages in structural flexibility, resiliency and reversibility over previous COFs – materials that are highly prized for their potential to capture and store carbon dioxide then convert it into valuable chemical products.

“We have taken the art of weaving into the atomic and molecular level, giving us a powerful new way of manipulating matter with incredible precision in order to achieve unique and valuable mechanical properties,” says Omar Yaghi, a chemist who holds joint appointments with Berkeley Lab’s Materials Sciences Division and UC Berkeley’s Chemistry Department, and is the co-director of the Kavli Energy NanoScience Institute (Kavli-ENSI).

“Weaving in chemistry has been long sought after and is unknown in biology,” Yaghi says. “However, we have found a way of weaving organic threads that enables us to design and make complex two- and three-dimensional organic extended structures.”

Yaghi is the corresponding author of a paper in Science reporting this new technique. The paper is titled “Weaving of organic threads into a crystalline covalent organic framework.” The lead authors are Yuzhong Liu, Yanhang Ma and Yingbo Zhao. Other co-authors are Xixi Sun, Felipe Gándara, Hiroyasu Furukawa, Zheng Liu, Hanyu Zhu, Chenhui Zhu, Kazutomo Suenaga, Peter Oleynikov, Ahmad Alshammari, Xiang Zhang and Osamu Terasaki.

COFs and their cousin materials, metal organic frameworks (MOFs), are porous three-dimensional crystals with extraordinarily large internal surface areas that can absorb and store enormous quantities of targeted molecules. Invented by Yaghi, COFs and MOFs consist of molecules (organics for COFs and metal-organics for MOFs) that are stitched into large and extended netlike frameworks whose structures are held together by strong chemical bonds. Such frameworks show great promise for, among other applications, carbon sequestration.

Through another technique developed by Yaghi, called “reticular chemistry,” these frameworks can also be embedded with catalysts to carry out desired functions: for example, reducing carbon dioxide into carbon monoxide, which serves as a primary building block for a wide range of chemical products including fuels, pharmaceuticals and plastics.

In this latest study, Yaghi and his collaborators used a copper(I) complex as a template for bringing threads of the organic compound “phenanthroline” into a woven pattern to produce an immine-based framework they dubbed COF-505. Through X-ray and electron diffraction characterizations, the researchers discovered that the copper(I) ions can be reversibly removed or restored to COF-505 without changing its woven structure. Demetalation of the COF resulted in a tenfold increase in its elasticity and remetalation restored the COF to its original stiffness.

“That our system can switch between two states of elasticity reversibly by a simple operation, the first such demonstration in an extended chemical structure, means that cycling between these states can be done repeatedly without degrading or altering the structure,” Yaghi says. “Based on these results, it is easy to imagine the creation of molecular cloths that combine unusual resiliency, strength, flexibility and chemical variability in one material.”

Yaghi says that MOFs can also be woven as can all structures based on netlike frameworks. In addition, these woven structures can also be made as nanoparticles or polymers, which means they can be fabricated into thin films and electronic devices.

“Our weaving technique allows long threads of covalently linked molecules to cross at regular intervals,” Yaghi says. “These crossings serve as points of registry, so that the threads have many degrees of freedom to move away from and back to such points without collapsing the overall structure, a boon to making materials with exceptional mechanical properties and dynamics.”

Source: Lawrence Berkeley National Laboratory