Solar-to-Fuel System Recycles CO2 to Make Ethanol and Ethylene: Berkeley National Lab



Schematic of a solar-powered electrolysis cell which converts carbon dioxide into hydrocarbon and oxygenate products with an efficiency far higher than natural photosynthesis. Power-matching electronics allow the system to operate over a range of sun conditions. (Credit: Clarissa Towle/Berkeley Lab)

Berkeley Lab advance is first demonstration of efficient, light-powered production of fuel via artificial photosynthesis

Scientists at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) have harnessed the power of photosynthesis to convert carbon dioxide into fuels and alcohols at efficiencies far greater than plants. The achievement marks a significant milestone in the effort to move toward sustainable sources of fuel.

Many systems have successfully reduced carbon dioxide to chemical and fuel precursors, such as carbon monoxide or a mix of carbon monoxide and hydrogen known as syngas. This new work, described in a study published in the journal Energy and Environmental Science, is the first to successfully demonstrate the approach of going from carbon dioxide directly to target products, namely ethanol and ethylene, at energy conversion efficiencies rivaling natural counterparts.

The researchers did this by optimizing each component of a photovoltaic-electrochemical system to reduce voltage loss, and creating new materials when existing ones did not suffice.

“This is an exciting development,” said study principal investigator Joel Ager, a Berkeley Lab scientist with joint appointments in the Materials Sciences and the Chemical Sciences divisions. “As rising atmospheric CO2 levels change Earth’s climate, the need to develop sustainable sources of power has become increasingly urgent. Our work here shows that we have a plausible path to making fuels directly from sunlight.”

That sun-to-fuel path is among the key goals of the Joint Center for Artificial Photosynthesis (JCAP), a DOE Energy Innovation Hub established in 2010 to advance solar fuel research. The study was conducted at JCAP’s Berkeley Lab campus.

The initial focus of JCAP research was tackling the efficient splitting of water in the photosynthesis process. Having largely achieved that task using several types of devices, JCAP scientists doing solar-driven carbon dioxide reduction began setting their sights on achieving efficiencies similar to those demonstrated for water splitting, considered by many to be the next big challenge in artificial photosynthesis.

Another research group at Berkeley Lab is tackling this challenge by focusing on a specific component in a photovoltaic-electrochemical system. In a study published today, they describe a new catalyst that can achieve carbon dioxide to multicarbon conversion using record-low inputs of energy.

Not just for noon


For this JCAP study, researchers engineered a complete system to work at different times of day, not just at a light energy level of 1-sun illumination, which is equivalent to the peak of brightness at high noon on a sunny day. They varied the brightness of the light source to show that the system remained efficient even in low light conditions.

When the researchers coupled the electrodes to silicon photovoltaic cells, they achieved solar conversion efficiencies of 3 to 4 percent for 0.35 to 1-sun illumination. Changing the configuration to a high-performance, tandem solar cell connected in tandem yielded a conversion efficiency to hydrocarbons and oxygenates exceeding 5 percent at 1-sun illumination.

Copper-Silver Cathode

At left is a surface view of a bimetallic copper-silver nanocoral cathode taken from a scanning electron micrograph. To the right is an energy-dispersive X-ray image of the cathode with the copper (in pink/red) and silver (in green) highlighted. (Credit: Gurudayal/Berkeley Lab)

“We did a little dance in the lab when we reached 5 percent,” said Ager, who also holds an appointment as an adjunct professor at UC Berkeley’s Materials Science and Engineering Department.

Among the new components developed by the researchers are a copper-silver nanocoral cathode, which reduces the carbon dioxide to hydrocarbons and oxygenates, and an iridium oxide nanotube anode, which oxidizes the water and creates oxygen.

“The nice feature of the nanocoral is that, like plants, it can make the target products over a wide range of conditions, and it is very stable,” said Ager.

The researchers characterized the materials at the National Center for Electron Microscopy at the Molecular Foundry, a DOE Office of Science User Facility at Berkeley Lab. The results helped them understand how the metals functioned in the bimetallic cathode. Specifically, they learned that silver aids in the reduction of carbon dioxide to carbon monoxide, while the copper picks up from there to reduce carbon monoxide further to hydrocarbons and alcohols.

Seeking better, low-energy breakups



Because carbon dioxide is a stubbornly stable molecule, breaking it up typically involves a significant input of energy.
“Reducing CO2 to a hydrocarbon end product like ethanol or ethylene can take up to 5 volts, start to finish,” said study lead author Gurudayal, postdoctoral fellow at Berkeley Lab. “Our system reduced that by half while maintaining the selectivity of products.”

Notably, the electrodes operated well in water, a neutral pH environment.

“Research groups working on anodes mostly do so using alkaline conditions since anodes typically require a high pH environment, which is not ideal for the solubility of CO2,” said Gurudayal. “It is very difficult to find an anode that works in neutral conditions.”

The researchers customized the anode by growing the iridium oxide nanotubes on a zinc oxide surface to create a more uniform surface area to better support chemical reactions.

“By working through each step so carefully, these researchers demonstrated a level of performance and efficiency that people did not think was possible at this point,” said Berkeley Lab chemist Frances Houle, JCAP deputy director for Science and Research Integration, who was not part of the study. “This is a big step forward in the design of devices for efficient CO2 reduction and testing of new materials, and it provides a clear framework for the future advancement of fully integrated solar-driven CO2-reduction devices.”

Other co-authors on the study include James Bullock, a Berkeley Lab postdoctoral researcher in materials sciences, who was instrumental in engineering the system’s photovoltaic and electrolysis cell pairing. Bullock works in the lab of study co-author Ali Javey, Berkeley Lab senior faculty scientist and a UC Berkeley professor of electrical engineering and computer sciences.

This work is supported by the DOE Office of Science.

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.

Graphene-wrapped nanocrystals may open door toward next-gen fuel cells



Ultra-Thin  oxide layer (oxygen atoms shown in red) coating graphene-wrapped magnesium nanoparticles (orange) still allows in hydrogen atoms (blue) for hydrogen storage applications

Researchers at the Department of Energy’s Lawrence Berkeley National Laboratory have developed a mix of metal nanocrystals wrapped in graphene that may open the door to the creation of a new type of fuel cell by enabling enhanced hydrogen storage properties.

Graphene-Wrapped Nanocrystals Make Inroads Toward Next-Gen Fuel Cells



Ultra-thin oxide layer (oxygen atoms shown in red) coating graphene-wrapped magnesium nanoparticles (orange) still allows in hydrogen atoms (blue) for hydrogen storage applications

The team studied how graphene can be used as both selective shielding, as well as a performance increasing factor in terms of hydrogen storage. 

The study drew upon a range of Lab expertise and capabilities to synthesize and coat the magnesium crystals, which measure only 3-4 nanometers (billionths of a meter) across; study their nanoscale chemical composition with X-rays; and develop computer simulations and supporting theories to better understand how the crystals and their carbon coating function together.

Reduced graphene oxide (or rGO) has nanoscale holes that permit hydrogen to pass through while keeping larger molecules away. This carbon wrapping was intended to prevent the magnesium – which is used as a hydrogen storage material – from reacting with its environment, including oxygen, water vapor and carbon dioxide. 

Such exposures could produce a thick coating of oxidation that would prevent the incoming hydrogen from accessing the magnesium surfaces. 

The study, however, suggests that an atomically thin layer of oxidation did form on the crystals during their preparation. Surprisingly, this oxide layer doesn’t seem to degrade the material’s performance.

The study’s lead author stated “Most people would suspect that the oxide layer is bad news for hydrogen storage, which it turns out may not be true in this case. Without this oxide layer, the reduced graphene oxide would have a fairly weak interaction with the magnesium, but with the oxide layer the carbon-magnesium binding seems to be stronger. 

That’s a benefit that ultimately enhances the protection provided by the carbon coating. There doesn’t seem to be any downside”.

The researchers noted that the current generation of hydrogen-fueled vehicles power their fuel cell engines using compressed hydrogen gas. “This requires bulky, heavy cylindrical tanks that limit the driving efficiency of such cars”, and the nanocrystals offer one possibility for eliminating these bulky tanks by storing hydrogen within other materials.

Ionic Industries announces a process for economically mass-producing graphene micro supercapacitors



Ionic Industries recently announced a process for economically mass-producing graphene micro supercapacitors and added that its directors and key personnel have taken direct stakes in the company.

Ionic Industries’ graphene supercapacitors patent image




Ionic stated that since it published the positive results on its graphene micro planar supercapacitors 2 years before, the company has been working toward developing a device that not only demonstrates similar performance but can be produced at scale to deliver an economically viable device.

The last 2 years of work reportedly culminated in the filing of a new patent titled: Capacitive energy storage device and method of producing same (Australian Provisional Patent Application 2017903619). 

The new patent covers: the design of new energy storage device, being a planar micro supercapacitor printed on a porous film; Ionic’s technique of stacking multiple layers of planar supercapacitors to create a 3D device that has ground-breaking energy and power density characteristics; and, most importantly, the company’s method for printing these devices so that they can be mass produced at low cost.

The critical element in this new technology is the ability to print the supercapacitors in the 1000s per minute, rather than individually creating each device with an expensive, direct-write approaches using lasers or ion beams. The technology builds on Ionic’s existing patent relating to graphene oxide membranes and it means the company could create these devices as easily as factories today produce food packaging and labels using gravure printers.

The team is now working on assembling the prototype device which is scheduled for completion in the next 6 weeks before it go into trials for a period of several months. 
The expected end result is a supercapacitor energy storage device comprised of printed graphene micro planar supercapacitors that can be produced economically at scale.

Ionic stated that it is extremely excited about this development as it brings it well within sight of a commercial product. The next steps involve identifying appropriate, world leading partners with whom Ionic can introduce this technology into products such as medical devices, wearable technologies, IoT devices or remote sensing applications.

More Durable – Less Expensive Fuel Cells Speeds the Commercialization of FC Vehicles – U. of Delaware


vehicles-cars-hydrogen-fuel-cellResearchers have developed a new technology that could speed up the commercialization of fuel cell vehicles

Summary: A new technology has been created that could make fuel cells cheaper and more durable. Hydrogen-powered fuel cells are a green alternative to internal combustion engines because they produce power through electro-chemical reactions, leaving no pollution behind. Platinum is the most common catalyst in the type of fuel cells used in vehicles, but it’s expensive. The UD team used a novel method to come up with a less expensive catalyst.

A team of engineers at the University of Delaware has developed a technology that could make fuel cells cheaper and more durable, a breakthrough that could speed up the commercialization of fuel cell vehicles.

They describe their results in a paper published in Nature Communications.

Hydrogen-powered fuel cells are a green alternative to internal combustion engines because they produce power through electrochemical reactions, leaving no pollution behind.

Materials called catalysts spur these electro-chemical reactions. Platinum is the most common catalyst in the type of fuel cells used in vehicles.F Cell Car images

However, platinum is expensive — as anyone who’s shopped for jewelry knows. The metal costs around $30,000 per kilogram.

Instead, the UD team made a catalyst of tungsten carbide, which goes for around $150 per kilogram. They produced tungsten carbide nanoparticles in a novel way, much smaller and more scalable than previous methods.

“The material is typically made at very high temperatures, about 1,500 Celsius, and at these temperatures, it grows big and has little surface area for chemistry to take place on,” said Dionisios Vlachos, director of UD’s Catalysis Center for Energy Innovation.. “Our approach is one of the first to make nanoscale material of high surface area that can be commercially relevant for catalysis.”

The researchers made tungsten carbide nanoparticles using a series of steps including hydrothermal treatment, separation, reduction, carburization and more.

“We can isolate the individual tungsten carbide nanoparticles during the process and make a very uniform distribution of particle size,” said Weiqing Zheng, a research associate at the Catalysis Center for Energy Innovation.

Next, the researchers incorporated the tungsten carbide nanoparticles into the membrane of a fuel cell. Automotive fuel cells, known as proton exchange membrane fuel cells (PEMFCs), contain a polymeric membrane. This membrane separates the cathode from the anode, which splits hydrogen (H2) into ions (protons) and delivers them to the cathode, which puts out current.

The plastic-like membrane wears down over time, especially if it undergoes too many wet/dry cycles, which can happen easily as water and heat are produced during the electrochemical reactions in fuel cells.

When tungsten carbide is incorporated into the fuel cell membrane, it humidifies the membrane at a level that optimizes performance.

“The tungsten carbide catalyst improves the water management of fuel cells and reduces the burden of the humidification system,” said Liang Wang, an associate scientist in the Department of Mechanical Engineering.

The team also found that tungsten carbide captures damaging free radicals before they can degrade the fuel cell membrane. As a result, membranes with tungsten carbide nanoparticles last longer than traditional ones.

“The low-cost catalyst we have developed can be incorporated within the membrane to improve performance and power density,” said . “As a result, the physical size of the fuel cell stack can be reduced for the same power, making it lighter and cheaper. Furthermore, our catalyst is able to deliver higher performance without sacrificing durability, which is a big improvement over similar efforts by other groups.”

The UD research team used innovative methods to test the durability of a fuel cell made with tungsten carbide. They used a scanning electron microscope and focused ion beam to obtain thin-slice images of the membrane, which they analyzed with software, rebuilding the three-dimensional structure of the membranes to determine fuel cell longevity.

The group has applied for a patent and hopes to commercialize their technology.

“This is a very good example of how different groups across departments can collaborate,” Zheng said.

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provided by University of DelawareNote: Content may be edited for style and length.


Journal Reference:

  1. Weiqing Zheng, Liang Wang, Fei Deng, Stephen A. Giles, Ajay K. Prasad, Suresh G. Advani, Yushan Yan, Dionisios G. Vlachos. Durable and self-hydrating tungsten carbide-based composite polymer electrolyte membrane fuel cellsNature Communications, 2017; 8 (1) DOI: 10.1038/s41467-017-00507-6

Supercharging Silicon Batteries – Powering Up LI Batteries


super silicon LI batt anode 170906103638_1_540x360
The porosity of the nano-structured Tantalum (in black) enables the formation of silicon channels (in blue) allowing lithium ions to travel faster within the battery. The rigidity of the tantalum scaffold also limits the expansion of the silicon and preserve structural integrity. Credit: Okinawa Institute of Science and Technology Graduate University Nanoparticles by Design Unit

Scientists have designed a novel silicon-based anode to provide lithium batteries with increased power and better stability.

 

As the world shifts towards renewable energy, moving on from fossil fuels, but at the same time relying on ever more energy-gobbling devices, there is a fast-growing need for larger high-performance batteries. Lithium-ion batteries (LIBs) power most of our portable electronics, but they are flammable and can even explode, as it happened to a recent model of smartphone. To prevent such accidents, the current solution is to encapsulate the anode — which is the negative (-) electrode of the battery, opposite to the cathode (+) — into a graphite frame, thus insulating the lithium ions. However, such casing is limited to a small scale to avoid physical collapse, therefore restraining the capacity — the amount of energy you can store — of the battery.

Looking for better materials, silicon offers great advantages over carbon graphite for lithium batteries in terms of capacity. Six atoms of carbon are required to bind a single atom of lithium, but an atom of silicon can bind four atoms of lithium at the same time, multiplying the battery capacity by more than 10-fold. However, being able to capture that many lithium ions means that the volume of the anode swells by 300% to 400%, leading to fracturing and loss of structural integrity. To overcome this issue, OIST researchers have now reported in Advanced Science the design of an anode built on nanostructured layers of silicon — not unlike a multi-layered cake — to preserve the advantages of silicon while preventing physical collapse.

This new battery is also aiming to improve power, which is the ability to charge and deliver energy over time.

“The goal in battery technology right now is to increase charging speed and power output,” explained Dr. Marta Haro Remon, first author of the study. “While it is fine to charge your phone or your laptop over a long period of time, you would not wait by your electric car for three hours at the charging station.”

And when it comes to providing energy, you would want your car to start off quickly at a traffic light or a stop sign, requiring a high spike in power, rather than slowly creeping forward. A well-thought design of a silicone-based anode might be a solution and answer these expectations.img_0132-3

The idea behind the new anode in the Nanoparticles by Design Unit at the Okinawa Institute of Science and Technology Graduate University is the ability to precisely control the synthesis and the corresponding physical structure of the nanoparticles. Layers of unstructured silicon films are deposited alternatively with tantalum metal nanoparticle scaffolds, resulting in the silicon being sandwiched in a tantalum frame.

“We used a technique called Cluster Beam Deposition,” continued Dr. Haro. “The required materials are directly deposited on the surface with great control. This is a purely physical method, there are no need for chemicals, catalysts or other binders.”

“We used a technique called Cluster Beam Deposition,” continued Dr. Haro. “The required materials are directly deposited on the surface with great control. This is a purely physical method, there are no need for chemicals, catalysts or other binders.”

The outcome of this research, led by Prof. Sowwan at OIST, is an anode with higher power but restrained swelling, and excellent cyclability — the amount of cycles in which a battery can be charged and discharged before losing efficiency. By looking closer into the nanostructured layers of silicon, the scientists realized the silicon shows important porosity with a grain-like structure in which lithium ions could travel at higher speeds compared to unstructured, amorphous silicon, explaining the increase in power. At the same time the presence of silicon channels along the Ta nanoparticle scaffolds allows the lithium ions to diffuse in the entire structure. On the other hand, the tantalum metal casing, while restraining swelling and improving structural integrity, also limited the overall capacity — for now.

However, this design is currently only at the stage of proof-of-concept, opening the door to numerous opportunities to improve capacity along with the increased power.

“It is a very open synthesis approach, there are many parameters you can play around,” commented Dr. Haro. “For example, we want to optimize the numbers of layers, their thickness, and replace tantalum metal with other materials.”

With this technique paving the way, it might very well be that the solution for future batteries, forecast to be omnipresent in our lives, will be found in nanoparticles.

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Material provided by Okinawa Institute of Science and Technology (OIST) Graduate UniversityNote: Content may be edited for style and length.

Journal Reference:

  1. Marta Haro, Vidyadhar Singh, Stephan Steinhauer, Evropi Toulkeridou, Panagiotis Grammatikopoulos, Mukhles Sowwan. Nanoscale Heterogeneity of Multilayered Si Anodes with Embedded Nanoparticle Scaffolds for Li-Ion BatteriesAdvanced Science, 2017; 1700180 DOI: 10.1002/advs.201700180

DNA and Nanotechnology: Protein ‘Rebar’ could help make Error-Free Nanostructures: NIST


DNA proteinrebarThe protein RecA (purple units), wraps around and fortifies double-stranded DNA, enabling scientists to build large structures with the genetic material. Credit: NIST

DNA is the stuff of life, but it is also the stuff of nanotechnology. Because molecules of DNA with complementary chemical structures recognize and bind to one another, strands of DNA can fit together like Lego blocks to make nanoscale objects of complex shape and structure.

But researchers need to work with much larger assemblages of DNA to realize a key goal: building durable miniature devices such as biosensors and drug-delivery containers. That’s been difficult because long chains of DNA are floppy and the standard method of assembling long chains is prone to error.

Using a DNA-binding protein called RecA as a kind of nanoscale rebar, or reinforcing bar, to support the floppy DNA scaffolding, researchers at the National Institute of Standards and Technology (NIST) have constructed several of the largest rectangular, linear and other shapes ever assembled from DNA. The structures can be two to three times larger than those built using standard DNA self-assembly techniques.

In addition, because the new method requires fewer chemically distinct pieces to build organized structures than the standard technique, known as DNA origami, it is likely to reduce the number of errors in constructing the shapes. That’s a big plus for the effort to produce reliable DNA-based devices in large quantities, said NIST researcher Alex Liddle.

Although RecA’s ability to bind to double-stranded DNA has been known for years, the NIST team is the first to integrate filaments of this protein into the assembly of DNA structures. The addition of RecA offers a particular advantage: Once one unit of the protein binds to a small segment of double-stranded DNA, it automatically attracts other units to line up alongside it, in the same way that bar magnets will join end-to-end. Like bricks filling out a foundation, RecA lines the entire length of the DNA strand, stretching, widening and strengthening it. A floppy, 2-nanometer-wide strand of DNA can transform into a rigid structure more than four times as wide.

“The RecA method greatly extends the ability of DNA self-assembly methods to build larger and more sophisticated structures,” said NIST’s Daniel Schiffels.

Schiffels, Liddle and their colleague Veronika Szalai describe their work in a recent article in ACS Nano.

The new method incorporates the DNA origami technique and goes beyond it, according to Liddle. In DNA origami, short strands of DNA that have a specific sequence of four base pairs are used as staples to tie together long sections of DNA. To make the skinny DNA skeleton stronger and thicker, the strand may loop back on itself, quickly using up the long string.

If DNA origami is all about the folding, Liddle likened his team’s new method to building a room, starting with a floor plan. The location of the short, single-stranded pieces of DNA that act as staples mark the corners of the room. Between the corners lies a long, skinny piece of single-stranded DNA. The enzyme DNA polymerase transforms a section of the long piece of single-stranded DNA into the double-stranded version of the molecule, a necessary step because RecA only binds strongly to double-stranded DNA. Then RecA assembles all along the double strand, reinforcing the DNA  and limiting the need for extra staples to maintain its shape.

With fewer staples required, the RecA  is likely able to build organized structures with fewer errors than DNA origami, Liddle said.

 Explore further: The promise of nanomanufacturing using DNA origami

More information: Daniel Schiffels et al. Molecular Precision at Micrometer Length Scales: Hierarchical Assembly of DNA–Protein Nanostructures, ACS Nano (2017). DOI: 10.1021/acsnano.7b00320

 

Toward a smart graphene membrane to desalinate water: Penn State University


Graphene H2O towardasmartA scalable graphene-based membrane for producing clean water Credit: Aaron Morelos-Gomez. Credit: Pennsylvania State University

An international team of researchers, including scientists from Shinshu University (Japan) and the director of Penn State’s ATOMIC Center, has developed a graphene-based coating for desalination membranes that is more robust and scalable than current nanofiltration membrane technologies. The result could be a sturdy and practical membrane for clean water solutions as well as protein separation, wastewater treatment and pharmaceutical and food industry applications.

“Our dream is to create a smart  that combines high flow rates, high efficiency, long lifetime, self-healing and eliminates bio and inorganic fouling in order to provide clean water solutions for the many parts of the world where clean water is scarce,” says Mauricio Terrones, professor of physics, chemistry and materials science and engineering, Penn State. “This work is taking us in that direction.”

The hybrid membrane the team developed uses a simple spray-on technology to coat a mixture of graphene oxide and few-layered graphene in solution onto a backbone support membrane of polysulfone modified with polyvinyl alcohol. The support membrane increased the robustness of the hybrid membrane, which was able to stand up to intense cross-flow, high pressure and chlorine exposure. Even in early stages of development, the membrane rejects 85 percent of salt, adequate for agricultural purposes though not for drinking, and 96 percent of dye molecules. Highly polluting dyes from textile manufacturing is commonly discharged into rivers in some areas of the world.

Chlorine is generally used to mitigate biofouling in membranes, but chlorine rapidly degrades the performance of current polymer membranes. The addition of few-layer graphene makes the new membrane highly resistant to chlorine.

Graphene is known to have high mechanical strength, and porous graphene is predicted to have 100 percent salt rejection, making it a potentially ideal material for desalination membranes. However, there are many challenges with scaling up graphene to industrial quantities including controlling defects and the need for complex transfer techniques required to handle the two-dimensional material. The current work attempts to overcome the scalability issues and provide an inexpensive, high quality membrane at manufacturing scale.

The work was performed in the Global Aqua Innovation Center and the Institute of Carbon Science and Technology at Shinshu University, Nagano, Japan, where Terrones is also a Distinguished Invited Professor. The team includes researchers Aaron Morelos-Gomez, Josue Ortiz-Medina and Rodolfo Cruz-Silva, former Ph.D. students of Terrones. Morelos-Gomez is lead author on a paper published online on August 28 in Nature Nanotechnology describing their work titled “Effective NaCL and dye rejection of hybrid graphene oxide/graphene layered membranes.” The Japanese researchers, Hiroyuki Muramatsu, Takumi Araki, Tomoyuki Fukuyo, Syogo Tejima, Kenji Takeuchi, and Takuya Hayashi, were also led by Professor Morinobu Endo.

First author Aaron Morelos-Gomez says, “Our membrane overcomes the water solubility of graphene oxide by using polyvinyl alcohol as an adhesive making it resistant against strong water flow and high pressures. By mixing  with  we could also improve significantly its chemical resistance.”

Professor Morinobu Endo concludes that “this is the first step towards more effective and smart membranes that could self-adapt depending on their environment.”

 Explore further: Graphene sieve turns seawater into drinking water

More information: Aaron Morelos-Gomez et al. Effective NaCl and dye rejection of hybrid graphene oxide/graphene layered membranes, Nature Nanotechnology (2017). DOI: 10.1038/nnano.2017.160

Read more at: https://phys.org/news/2017-09-smart-graphene-membrane-desalinate.html#jCp

Read more at: https://phys.org/news/2017-09-smart-graphene-membrane-desalinate.html#jCp

Silicon Solves Problems for next-Generation Battery Technology: University of Eastern Finland


Silicon in New LI Batts 170830114817_1_540x360

Silicon — the second most abundant element in the earth’s crust — shows great promise in Li-ion batteries, according to new research from the University of Eastern Finland. By replacing graphite anodes with silicon, it is possible to quadruple anode capacity.

In a climate-neutral society, renewable and emission-free sources of energy, such as wind and solar power, will become increasingly widespread. The supply of energy from these sources, however, is intermittent, and technological solutions are needed to safeguard the availability of energy also when it’s not sunny or windy. Furthermore, the transition to emission-free energy forms in transportation requires specific solutions for energy storage, and lithium-ion batteries are considered to have the best potential.

Researchers from the University of Eastern Finland introduced new technology to Li-ion batteries by replacing graphite used in anodes by silicon. The study analysed the suitability of electrochemically produced nanoporous silicon for Li-ion batteries. It is generally understood that in order for silicon to work in batteries, nanoparticles are required, and this brings its own challenges to the production, price and safety of the material.

However, one of the main findings of the study was that particles sized between 10 and 20 micrometres and with the right porosity were in fact the most suitable ones to be used in batteries. The discovery is significant, as micrometre-sized particles are easier and safer to process than nanoparticles. This is also important from the viewpoint of battery material recyclability, among other things. The findings were published in Scientific Reports.

“In our research, we were able to combine the best of nano- and micro-technologies: nano-level functionality combined with micro-level processability, and all this without compromising performance,” Researcher Timo Ikonen from the University of Eastern Finland says. “Small amounts of silicon are already used in Tesla’s batteries to increase their energy density, but it’s very challenging to further increase the amount,” he continues.

Next, researchers will combine silicon with small amounts of carbon nanotubes in order to further enhance the electrical conductivity and mechanical durability of the material.

“We now have a good understanding of the material properties required in large-scale use of silicon in Li-ion batteries. However, the silicon we’ve been using is too expensive for commercial use, and that’s why we are now looking into the possibility of manufacturing a similar material from agricultural waste, for example from barley husk ash,” Professor Vesa-Pekka Lehto explains.

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