Scientists devise catalyst that uses light to turn carbon dioxide to fuel

Looking into the hard X-ray nanoprobe synchrotron chamber while measuring a response of an individual cuprous oxide particle to the exposure of carbon dioxide, water and light. (Image by Tijana Rajh / Argonne National Laboratory.)

 

Researchers find new way to convert carbon dioxide into a usable fuel source.

The concentration of carbon dioxide in our atmosphere is steadily increasing, and many scientists believe that it is causing impacts in our environment. Recently, scientists have sought ways to recapture some of the carbon in the atmosphere and potentially turn it into usable fuel — which would be a holy grail for sustainable energy production.

In a recent study from the U.S. Department of Energy’s (DOE) Argonne National Laboratory, scientists have used sunlight and a catalyst largely made of copper to transform carbon dioxide to methanol. A liquid fuel, methanol offers the potential for industry to find an additional source to meet America’s energy needs.

“Carbon dioxide is such a stable molecule and it results from the burning of basically everything, so the question is how do we fight nature and go from a really stable end product to something useful and energy rich.” — Argonne Distinguished Fellow Tijana Rajh

The study describes a photocatalyst made of cuprous oxide (Cu­₂O), a semiconductor that when exposed to light can produce electrons that become available to react with, or reduce, many compounds. After being excited, electrons leave a positive hole in the catalyst’s lower-energy valence band that, in turn, can oxidize water.

“This photocatalyst is particularly exciting because it has one of the most negative conduction bands that we’ve used, which means that the electrons have more potential energy available to do reactions,” said Argonne Distinguished Fellow Tijana Rajh, an author of the study.

Previous attempts to use photocatalysts, such as titanium dioxide, to reduce carbon dioxide tended to produce a whole mish-mash of various products, ranging from aldehydes to methane. The lack of selectivity of these reactions made it difficult to segregate a usable fuel stream, Rajh explained.

“Carbon dioxide is such a stable molecule and it results from the burning of basically everything, so the question is how do we fight nature and go from a really stable end product to something useful and energy rich,” Rajh said.

The idea for transforming carbon dioxide into useful energy comes from the one place in nature where this happens regularly. ​“We had this idea of copying photosynthesis, which uses carbon dioxide to make food, so why couldn’t we use it to make fuel?” Rajh said. ​“It turns out to be a complex problem, because to make methanol, you need not just one electron but six.”

By switching from titanium dioxide to cuprous oxide, scientists developed a catalyst that not only had a more negative conduction band but that would also be dramatically more selective in terms of its products. This selectivity results not only from the chemistry of cuprous oxide but from the geometry of the catalyst itself.

“With nanoscience, we start having the ability to meddle with the surfaces to induce certain hotspots or change the surface structure, cause strain or certain surface sites to expose differently than they are in the bulk,” Rajh said.

Because of this ​“meddling,” Rajh and Argonne postdoctoral researcher Yimin Wu, now an assistant professor at the University of Waterloo, managed to create a catalyst with a bit of a split personality. The cuprous oxide microparticles they developed have different facets, much like a diamond has different facets. Many of the facets of the microparticle are inert, but one is very active in driving the reduction of carbon dioxide to methanol.

According to Rajh, the reason that this facet is so active lies in two unique aspects.  First, the carbon dioxide molecule bonds to it in such a way that the structure of the molecule actually bends slightly, diminishing the amount of energy it takes to reduce. Second, water molecules are also absorbed very near to where the carbon dioxide molecules are absorbed.

“In order to make fuel, you not only need to have carbon dioxide to be reduced, you need to have water to be oxidized,” Rajh said. ​“Also, adsorption conformation in photocatalysis is extremely important — if you have one molecule of carbon dioxide absorbed in one way, it might be completely useless. But if it is in a bent structure, it lowers the energy to be reduced.”

Argonne scientists also used scanning fluorescence X-ray microscopy at Argonne’s Advanced Photon Source (APS) and transmission electron microscopy at the Center for Nanoscale Materials (CNM) to reveal the nature of the faceted cuprous oxide microparticles. The APS and CNM are both DOE Office of Science User Facilities.

A paper based on the study, ​“Facet-dependent active sites of a single Cu₂O particle photocatalyst for CO₂ reduction to methanol,” appeared in the November 4 online edition of Nature Energy. Other contributors to the study include Argonne’s Ian McNulty, Cong Liu, Kah Chun Lau, Paul Paulikas, Cheng-Jun Sun, Zhonghou Chai, Jeff Guest, Yang Ren, Vojislav Stamenkovic, Larry Curtiss and Yuzi Liu. Qi Liu of the City University of Hong Kong also contributed.

The work was funded by an Argonne Laboratory-Directed Research and Development grant and by the DOE’s Office of Science.

 

About Argonne’s Center for Nanoscale Materials
The Center for Nanoscale Materials is one of the five DOE Nanoscale Science Research Centers, premier national user facilities for interdisciplinary research at the nanoscale supported by the DOE Office of Science. Together the NSRCs comprise a suite of complementary facilities that provide researchers with state-of-the-art capabilities to fabricate, process, characterize and model nanoscale materials, and constitute the largest infrastructure investment of the National Nanotechnology Initiative. The NSRCs are located at DOE’s Argonne, Brookhaven, Lawrence Berkeley, Oak Ridge, Sandia and Los Alamos National Laboratories. For more information about the DOE NSRCs, please visit https://​sci​ence​.osti​.gov/​U​s​e​r​-​F​a​c​i​l​i​t​i​e​s​/​U​s​e​r​-​F​a​c​i​l​i​t​i​e​s​-​a​t​-​a​-​G​lance.

 

About the Advanced Photon Source
This research used resources of the Advanced Photon Source, a U.S. DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02–06CH11357.

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 https://​ener​gy​.gov/​s​c​ience.

Graphene takes a Step Toward Renewable Fuel – Converting water and carbon dioxide to the renewable energy of the future

Jianwu Sun at Linköping University inspecting the growth reactor for growth of cubic silicon carbide. Credit: Thor Balkhed/LiU

Using the energy from the sun and graphene applied to the surface of cubic silicon carbide, researchers at Linköping University, Sweden, are working to develop a method to convert water and carbon dioxide to the renewable energy of the future.

They have now taken an important step toward this goal, reporting a method that makes it possible to produce graphene with several layers in a tightly controlled process. The researchers have also shown that graphene acts as a superconductor in certain conditions. Their results have been published in the scientific journals Carbon and Nano Letters.

Carbon, oxygen and hydrogen are the three elements obtained by taking apart molecules of carbon dioxide and water. The same elements are the building blocks of chemical substances used for fuel, such as ethanol and methane. The conversion of carbon dioxide and water to renewable fuel could provide an alternative to fossil fuels and contribute to reducing carbon dioxide emissions into the atmosphere. Jianwu Sun, senior lecturer at Linköping University, is trying to find a way to do just that.

Researchers at Linköping University have previously developed a world-leading method to produce cubic silicon carbide, which consists of silicon and carbon. The cubic form has the ability to capture energy from the sun and create charge carriers. This is, however, not sufficient. Graphene, one of the thinnest materials ever produced, plays a key role in the project. The material comprises a single layer of carbon atoms bound to each other in a hexagonal lattice. Graphene has a high ability to conduct an electric current, a property that would be useful for solar energy conversion. It also has several unique properties, and possible uses of graphene are being extensively studied all over the world.

Read Original Post from Linkoping University

In recent years, the researchers have attempted to improve the process by which graphene grows on a surface in order to control the properties of the graphene. Their recent progress is described in an article in the scientific journal Carbon.

“It is relatively easy to grow one layer of graphene on silicon carbide. But it’s a greater challenge to grow large-area uniform graphene that consists of several layers on top of each other. We have now shown that it is possible to grow uniform graphene that consists of up to four layers in a controlled manner,” says Jianwu Sun of the Department of Physics, Chemistry and Biology at Linköping University.

One of the difficulties posed by multilayer graphene is that the surface becomes uneven when different numbers of layers grow at different locations. The edge when one layer ends has the form of a tiny, nanoscale staircase. Flat layers are desirable, so these steps are a problem, particularly when the steps accumulate in one location, like a wrongly built staircase in which several steps have been united to form one large step. The researchers have now found a way to remove these large, united steps by growing the graphene at a carefully controlled temperature. Furthermore, the researchers have shown that their method makes it possible to control how many layers the graphene will contain. This is the first key step in an ongoing research project whose goal is to make fuel from water and carbon dioxide.

In a closely related article in the journal Nano Letters, the researchers describe investigations into the electronic properties of multilayer graphene grown on cubic silicon carbide.

“We discovered that multilayer graphene has extremely promising electrical properties that enable the material to be used as a superconductor, a material that conducts electrical current with zero electrical resistance. This special property arises solely when the graphene layers are arranged in a special way relative to each other,” says Jianwu Sun.

Theoretical calculations had predicted that multilayer graphene would have superconductive properties, provided that the layers are arranged in a particular way. In the new study, the researchers demonstrate experimentally for the first time that this is the case. Superconducting magnets are extremely powerful magnets used in medical magnetic resonance cameras and in particle accelerators. There are many potential areas of application for superconductors, such as electrical supply lines with zero energy loss, and high-speed trains that float on a magnetic field. Their use is currently limited by the inability to produce superconductors that function at room temperature. Currently available superconductors function only at extremely low temperatures.

 Explore further: Atoms use tunnels to escape graphene cover

More information: Yuchen Shi et al, Elimination of step bunching in the growth of large-area monolayer and multilayer graphene on off-axis 3C SiC (111), Carbon (2018). DOI: 10.1016/j.carbon.2018.08.042

Weimin Wang et al. Flat-Band Electronic Structure and Interlayer Spacing Influence in Rhombohedral Four-Layer Graphene, Nano Letters (2018). DOI: 10.1021/acs.nanolett.8b02530

Journal reference: Carbon   Nano Letters  

Provided by: Linköping University

 

Researchers Develop Novel Two-Step CO2 Conversion Technology – Could aid in the production of valuable chemicals and fuels

UD Professor Feng Jiao’s team constructed an electrolyser, pictured here, to conduct their novel two-step conversion process.

 

A team of researchers at the University of Delaware’s Center for Catalytic Science and Technology (CCST) has discovered a novel two-step process to increase the efficiency of carbon dioxide (CO2) electrolysis, a chemical reaction driven by electrical currents that can aid in the production of valuable chemicals and fuels.

The results of the team’s study were published Monday, Aug. 20 in Nature Catalysis.

The research team, consisting of Feng Jiao, associate professor of chemical and biomolecular engineering, and graduate students Matthew Jouny and Wesley Luc, obtained their results by constructing a specialized three-chambered device called an electrolyser, which uses electricity to reduce CO2 into smaller molecules.

Compared to fossil fuels, electricity is a much more affordable and environmentally-friendly method for driving chemical processes to produce commercial chemicals and fuels. These can include ethylene, which is used in the production of plastics, and ethanol, a valuable fuel additive.

“This novel electrolysis technology provides a new route to achieve higher selectivities at incredible reaction rates, which is a major step towards commercial applications,” said Jiao, who also serves as associate director of CCST.

Whereas direct CO2 electrolysis is the standard method for reducing carbon dioxide, Jiao’s team broke the electrolysis process into two steps, reducing CO2 into carbon monoxide (CO) and then reducing the CO further into multi-carbon (C2+) products. This two-part approach, said Jiao, presents multiple advantages over the standard method.

“By breaking the process into two steps, we’ve obtained a much higher selectivity towards multi-carbon products than in direct electrolysis,” Jiao said. “The sequential reaction strategy could open up new ways to design more efficient processes for CO2 utilization.”

Electrolysis is also driving Jiao’s research with colleague Bingjun Xu, assistant professor of chemical and biomolecular engineering. In collaboration with researchers at Tianjin University in China, Jiao and Xu are designing a system that could reduce greenhouse gas emissions by using carbon-neutral solar electricity.

“We hope this work will bring more attention to this promising technology for further research and development,” Jiao said. “There are many technical challenges still be solved, but we are working on them!”

MIT: New battery technology gobbles up carbon dioxide – Ultimately may help reduce the emission of the greenhouse gas to the atmosphere + Could Carbon Dioxide Capture Batteries Replace Phone and EV Batteries?

This scanning electron microscope image shows the carbon cathode of a carbon-dioxide-based battery made by MIT researchers, after the battery was discharged. It shows the buildup of carbon compounds on the surface, composed of carbonate material that could be derived from power plant emissions, compared to the original pristine surface (inset) Courtesy of the researchers

Lithium-based battery could make use of greenhouse gas before it ever gets into the atmosphere.

A new type of battery developed by researchers at MIT could be made partly from carbon dioxide captured from power plants. Rather than attempting to convert carbon dioxide to specialized chemicals using metal catalysts, which is currently highly challenging, this battery could continuously convert carbon dioxide into a solid mineral carbonate as it discharges.

While still based on early-stage research and far from commercial deployment, the new battery formulation could open up new avenues for tailoring electrochemical carbon dioxide conversion reactions, which may ultimately help reduce the emission of the greenhouse gas to the atmosphere.

Read Also:  Scientists Have Created Batteries Using Carbon Dioxide From The Atmosphere Which Could Replace Phone And Electric Car Batteries

 

 

 

The battery is made from lithium metal, carbon, and an electrolyte that the researchers designed. The findings are described today in the journal Joule, in a paper by assistant professor of mechanical engineering Betar Gallant, doctoral student Aliza Khurram, and postdoc Mingfu He.

Currently, power plants equipped with carbon capture systems generally use up to 30 percent of the electricity they generate just to power the capture, release, and storage of carbon dioxide. Anything that can reduce the cost of that capture process, or that can result in an end product that has value, could significantly change the economics of such systems, the researchers say.

However, “carbon dioxide is not very reactive,” Gallant explains, so “trying to find new reaction pathways is important.” Generally, the only way to get carbon dioxide to exhibit significant activity under electrochemical conditions is with large energy inputs in the form of high voltages, which can be an expensive and inefficient process. Ideally, the gas would undergo reactions that produce something worthwhile, such as a useful chemical or a fuel. However, efforts at electrochemical conversion, usually conducted in water, remain hindered by high energy inputs and poor selectivity of the chemicals produced.

Gallant and her co-workers, whose expertise has to do with nonaqueous (not water-based) electrochemical reactions such as those that underlie lithium-based batteries, looked into whether carbon-dioxide-capture chemistry could be put to use to make carbon-dioxide-loaded electrolytes — one of the three essential parts of a battery — where the captured gas could then be used during the discharge of the battery to provide a power output.

This approach is different from releasing the carbon dioxide back to the gas phase for long-term storage, as is now used in carbon capture and sequestration, or CCS. That field generally looks at ways of capturing carbon dioxide from a power plant through a chemical absorption process and then either storing it in underground formations or chemically altering it into a fuel or a chemical feedstock.

Instead, this team developed a new approach that could potentially be used right in the power plant waste stream to make material for one of the main components of a battery.

While interest has grown recently in the development of lithium-carbon-dioxide batteries, which use the gas as a reactant during discharge, the low reactivity of carbon dioxide has typically required the use of metal catalysts. Not only are these expensive, but their function remains poorly understood, and reactions are difficult to control.

By incorporating the gas in a liquid state, however, Gallant and her co-workers found a way to achieve electrochemical carbon dioxide conversion using only a carbon electrode. The key is to pre-activate the carbon dioxide by incorporating it into an amine solution.

“What we’ve shown for the first time is that this technique activates the carbon dioxide for more facile electrochemistry,” Gallant says. “These two chemistries — aqueous amines and nonaqueous battery electrolytes — are not normally used together, but we found that their combination imparts new and interesting behaviors that can increase the discharge voltage and allow for sustained conversion of carbon dioxide.”

They showed through a series of experiments that this approach does work, and can produce a lithium-carbon dioxide battery with voltage and capacity that are competitive with that of state-of-the-art lithium-gas batteries. Moreover, the amine acts as a molecular promoter that is not consumed in the reaction.

The key was developing the right electrolyte system, Khurram explains. In this initial proof-of-concept study, they decided to use a nonaqueous electrolyte because it would limit the available reaction pathways and therefore make it easier to characterize the reaction and determine its viability. The amine material they chose is currently used for CCS applications, but had not previously been applied to batteries.

This early system has not yet been optimized and will require further development, the researchers say. For one thing, the cycle life of the battery is limited to 10 charge-discharge cycles, so more research is needed to improve rechargeability and prevent degradation of the cell components. “Lithium-carbon dioxide batteries are years away” as a viable product, Gallant says, as this research covers just one of several needed advances to make them practical.

But the concept offers great potential, according to Gallant. Carbon capture is widely considered essential to meeting worldwide goals for reducing greenhouse gas emissions, but there are not yet proven, long-term ways of disposing of or using all the resulting carbon dioxide. Underground geological disposal is still the leading contender, but this approach remains somewhat unproven and may be limited in how much it can accommodate. It also requires extra energy for drilling and pumping.

The researchers are also investigating the possibility of developing a continuous-operation version of the process, which would use a steady stream of carbon dioxide under pressure with the amine material, rather than a preloaded supply the material, thus allowing it to deliver a steady power output as long as the battery is supplied with carbon dioxide. Ultimately, they hope to make this into an integrated system that will carry out both the capture of carbon dioxide from a power plant’s emissions stream, and its conversion into an electrochemical material that could then be used in batteries. “It’s one way to sequester it as a useful product,” Gallant says.

“It was interesting that Gallant and co-workers cleverly combined the prior knowledge from two different areas, metal-gas battery electrochemistry and carbon-dioxide capture chemistry, and succeeded in increasing both the energy density of the battery and the efficiency of the carbon-dioxide capture,” says Kisuk Kang, a professor at Seoul National University in South Korea, who was not associated with this research.

“Even though more precise understanding of the product formation from carbon dioxide may be needed in the future, this kind of interdisciplinary approach is very exciting and often offers unexpected results, as the authors elegantly demonstrated here,” Kang adds.

MIT’s Department of Mechanical Engineering provided support for the project.

Harvesting Energy From Carbon Dioxide Emissions

Energy: Device generates electricity from the entropy created when the greenhouse gas mixes with fresh air

By Naomi Lubick

An electrochemical cell could someday generate electricity from carbon dioxide emitted by power plants as the gas wafts into the atmosphere. Researchers demonstrate that the cell harvests energy released by the entropy created when CO₂ mixes with fresh air (Environ. Sci. Technol. Lett. 2013, DOI: 10.1021/ez4000059). The device could help power plants increase electricity output without producing additional CO₂.

Electricity From CO₂            

 A new electrochemical cell generates electricity from carbon dioxide dissolved in water solutions. When dissolved, the gas forms carbonic acid (H₂CO₃), which then dissociates into H⁺ and HCO₃^– ions. These ions adsorb selectively onto one of the two electrodes (left and right), depending on the type of membrane on the electrode (yellow and red). This process generates a current between the electrodes.            Credit: Environ. Sci. Technol. Lett

Bert Hamelers of Wetsus, a research center focused on water treatment technology in Leeuwarden, the Netherlands, and his team developed the new device based on one they created to tap energy released when seawater and freshwater mix. The previous cell consisted of electrodes coated with ion-exchange membranes. As seawater and freshwater flowed through the cell, the membranes absorbed and released sodium and chloride ions, creating a current.

Hamelers realized that the same cell design could harvest the energy released when two gases mix. To do so with CO₂, the team first mixed it with a liquid, using either deionized water or a 0.25 M water solution of monoethanolamine (MEA), which is often used to remove CO₂ from exhaust gases. In water, the CO₂ forms carbonic acid, which then dissociates into H⁺ and HCO₃^– ions. These ions act like the sodium and chloride ions in the previous entropy-harvesting device. As the solution passes through the cell, ion-exchange membranes on the cell’s electrodes absorb the ions, H⁺ on one electrode and HCO₃^– on the other. This process produces current between the electrodes.

           

                       Mixing Gases            

To harvest energy from mixing CO₂ and fresh air, researchers first must dissolve the gases in water solutions (CO₂, right; air, left). The water then passes by membranes in an electrochemical cell (rectangular block in the middle) in alternating pulses. The cell generates electricity as ions in the solutions adsorb onto and desorb from the electrodes.    Credit: Bert Hamelers/Wetsus        

Then water with dissolved fresh air flushes through the cell. Since this water is mostly ion free, the membranes release the H⁺ and HCO₃^– ions into the water, producing current in the opposite direction as before. This now ion-laden water leaves the cell and gets flushed with air. The CO₂ gas reforms and is then released. The fluidics system continually repeats this cycle, sending alternating pulses of the dissolved CO₂ and dissolved air through the cell.

With the small-scale system the researchers built in their lab, they could harvest 24% of the energy released when they used deionized water and 32% when they used MEA. At its most efficient, the lab setup generates only milliwatts of power. But with a scaled-up system, the researchers calculate that power plants could produce megawatts of power using CO₂ emissions. They estimate that flue gases from power plants worldwide contain enough CO₂ to generate 850 TWh of energy every year.

But the system has a few obstacles to overcome before it can be used in such large-scale applications, the team and outside experts say. For example, impurities in a power plant’s flue gas, such as sulfur dioxide or nitrogen oxides, could foul the cell’s membranes. The immediate problem is getting CO₂ emissions dissolved into a liquid upon exiting the stacks. With current technology, dissolving that much gas in liquid would require more energy than the researchers’ system could generate. So it will take more research to find the optimal process to dissolve CO₂ using as little energy as possible, Hamelers says.

Still, the concept is “marvelous,” says Volker Presser of the Leibniz Institute for New Materials in Germany. Now the researchers “need to envision a system that can take up tonnes and tonnes of CO₂,” over multiple cycles, he says. With such a system generating extra electricity, Presser says, coal plants could produce energy more efficiently, without emitting more CO₂.

Chemical & Engineering News

ISSN 0009-2347

Copyright © 2013 American Chemical Society

Nanotechnology material could help reduce CO2 emissions from coal-fired power plants

(Nanowerk News) University of Adelaide researchers have  developed a new nanomaterial that could help reduce carbon dioxide emissions  from coal-fired power stations.

The new nanomaterial, described in the Journal of the  American Chemical Society (“Post-synthetic Structural Processing in a  Metal–Organic Framework Material as a Mechanism for Exceptional CO2/N2 Selectivity”), efficiently separates the  greenhouse gas carbon dioxide from nitrogen, the other significant component of  the waste gas released by coal-fired power stations. This would allow the carbon  dioxide to be separated before being stored, rather than released to the  atmosphere.

“A considerable amount of Australia‘s – and the world’s – carbon  dioxide emissions come from coal-fired power stations,” says Associate Professor  Christopher Sumby, project leader and ARC Future Fellow in the  University’s School of Chemistry and Physics.

“Removing CO2 from the flue gas  mixture is the focus of a lot of research. Most of Australia’s energy generation  still comes from coal. Changing to cleaner energies is not that straightforward  but, if we can clean up the emissions, we’ve got a great stop-gap technology.”

The researchers have produced a new absorbent material, called a  ‘metal-organic framework‘, which has “remarkable selectivity” for separating  CO2 from nitrogen.

“It is like a sponge but at a nanoscale,” says Associate  Professor Sumby. “The material has small pores that gas molecules can fit into –  a CO2 molecule fits but a nitrogen molecule is  slightly too big. That’s how we separate them.”

Other methods of separating CO2 from nitrogen are energy-intensive and expensive. This material has the  potential to be more energy efficient. It’s easy to regenerate (removing the  CO2) for reuse, with small changes in temperature  or pressure.

“This material could be used as it is but there are probably  smarter ways to implement the benefits,” says Associate Professor Sumby.

“One of the next steps we’re pursuing is taking the material in  powder form and dispersing it in a membrane. That may be more practical for  industrial use.”

The project is funded by the Science Industry Endowment Fund and  is a collaboration between researchers in the Centre of Advanced  Nanomaterials, in the School of Chemistry and Physics, and the CSIRO.

Source: University of Adeleide

Read more: http://www.nanowerk.com/news2/newsid=31235.php#ixzz2YdWOaqRt