Stanford University researchers have found a new way to convert carbon dioxide into the building block for sustainable liquid fuels. The new process was very efficient in tests and did not have the reaction that destroys a conventional device.

The Stanford researchers have discovered a practical starting point for converting carbon dioxide recycling it back into sustainable liquid fuels, including fuels for heavier modes of transportation that may prove very difficult to electrify, like airplanes, ships and freight trains.

From left: Christopher Graves, Michal Bajdich and Michael Machala in front of the pulsed laser deposition machine that Machala used to fabricate the electrodes. Image credit: Mark Golden, Stanford University. Click image for the largest view.

Carbon neutral re-use of CO2 has emerged as an alternative idea to sequestering the CO2 underground.

In a new study published in Nature Energy, researchers from Stanford University and the Technical University of Denmark (DTU) show how electricity and an Earth-abundant catalyst can convert CO2 into energy-rich carbon monoxide (CO) better than conventional methods.

The catalyst – cerium oxide – is much more resistant to breaking down. Stripping oxygen from CO2 to make CO gas is the first step in turning CO2 into nearly any liquid fuel and other products, like synthetic gas and plastics. The addition of hydrogen to CO can produce fuels like synthetic diesel and the equivalent of jet fuel. The team envisions using renewable power to make the CO and for subsequent conversions, which would result in carbon-neutral products.

William Chueh, an associate professor of materials science and engineering at Stanford, one of three senior authors of the paper said, “We showed we can use electricity to reduce CO2 into CO with 100 percent selectivity and without producing the undesired byproduct of solid carbon.”

Chueh, aware of DTU’s research in this area, invited Christopher Graves, associate professor in DTU’s Energy Conversion & Storage Department, and Theis Skafte, a DTU doctoral candidate at the time, to come to Stanford and work on the technology together.

Skafte, lead author of the study, who is now a postdoctoral researcher at DTU said, “We had been working on high-temperature CO2 electrolysis for years, but the collaboration with Stanford was the key to this breakthrough. We achieved something we couldn’t have separately – both fundamental understanding and practical demonstration of a more robust material.”

One advantage sustainable liquid fuels could have over the electrification of transportation is that they could use the existing gasoline and diesel infrastructure, like engines, pipelines and gas stations. Additionally, the barriers to electrifying airplanes and ships – long distance travel and the high weight of batteries – would not be problems for energy-dense, carbon-neutral fuels.

Although plants reduce CO2 to carbon-rich sugars naturally, an artificial electrochemical route to CO has yet to be widely commercialized. Among the problems: Devices use too much electricity, convert a low percentage of CO2 molecules, or produce pure carbon that destroys the device. Researchers in the new study first examined how different devices succeeded and failed in CO2 electrolysis.

With the insights gained, the researchers built two cells for CO2 conversion testing: one with cerium oxide and the other with conventional nickel-based catalysts. The ceria electrode remained stable, while carbon deposits damaged the nickel electrode, significantly shortening the catalyst’s lifetime.

DTU’s Graves, a senior author of the study and visiting scholar at Stanford at the time said, “This remarkable capability of ceria has major implications for the practical lifetime of CO2 electrolyzer devices. Replacing the current nickel electrode with our new ceria electrode in the next generation electrolyzer would improve device lifetime.”

Eliminating early cell death could significantly lower the cost of commercial CO production. The suppression of carbon buildup also allows the new type of device to convert more of the CO2 to CO, which is limited to well below 50 percent CO product concentration in today’s cells. This could also reduce production costs.

Michal Bajdich, a senior author of the paper and an associate staff scientist at the SUNCAT Center for Interface Science & Catalysis, a partnership between the SLAC National Accelerator Laboratory and Stanford’s School of Engineering explained, “The carbon-suppression mechanism on ceria is based on trapping the carbon in stable oxidized form. We were able to explain this behavior with computational models of CO2 reduction at elevated temperature, which was then confirmed with X-ray photoelectron spectroscopy of the cell in operation.”

The high cost of capturing CO2 has been a barrier to sequestering it underground on a large scale, and that high cost could be a barrier to using CO2 to make more sustainable fuels and chemicals. However, the market value of those products combined with payments for avoiding the carbon emissions could help technologies that use CO2 overcome the cost hurdle more quickly.

The researchers hope that their initial work on revealing the mechanisms in CO2 electrolysis devices by spectroscopy and modeling will help others in tuning the surface properties of ceria and other oxides to further improve CO2 electrolysis.

This is very good news indeed. It should be considered a breakthrough. The prospect of the energy economy entering into a fast carbon cycle is a true long term goal of immense importance. The adoption, production and marketing has a couple problems though. Research is pretty thin in carbon capture technologies. But carbon capture would seem to be an easier target than hydrogen storage. At least CO2 can be compressed, transported and stored long term, something hydrogen simply defies. The other problem is “payments for avoiding the carbon emissions” that seems to be an indirect way to say “carbon tax”. Tax equals bureaucrats, regulations and rules that would drive up all carbon fuel costs. The other result is once a support is obtained the motive for continued research ceases to exist. More fuel looks possible here, better and cheaper needs more work.

Other Stanford co-authors are PhD alumnus Zixuan Guan, postdoc Michael Machala, former postdocs Matteo Monti and Chirranjeevi B. Gopal, and SLAC postdoc Jose A. Garrido Torres. Other DTU co-authors are PhD candidate Lev Martinez, nanolab group leader Eugen Stamate and staff researcher Simone Sanna. The other co-authors are Ethan J. Crumlin, a research scientist at Lawrence Berkeley National Laboratory, and Max Garcia Melchor, an assistant professor at Trinity College, Dublin.

This project was supported by Haldor Topsoe A/S, Innovation Fund Denmark, the Danish Agency for Science, Technology & Innovation and Energinet.dk., the U.S. Department of Energy, the SUNCAT Center and a National Science Foundation CAREER award.

North Carolina State University researchers have found a new to convert a temperature difference into an electrical voltage.

This effect, which the researchers call ‘paramagnon drag thermopower,’ is a local thermal perturbations of spins in a solid that can convert heat to energy even in a paramagnetic material – where spins weren’t thought to correlate long enough to do so.

The discovery could lead to more efficient thermal energy harvesting. For example, by converting car exhaust heat into electric power to enhance fuel-efficiency, or powering smart clothing by body heat.

Magnon and paramagnon drag: Magnons, waves created by spins of individual atoms (grey cones) drag electrons (green dots) along a thermal gradient to create thermopower. In the paramagnetic state, local thermal fluctuations form small magnon packets that can similarly drag electrons. Classical paramagnets do not produce drag. Image Credit: Renee Ripley, Ohio State University. Click image for the largest view.

The research team includes scientists from North Carolina State University, the Department of Energy’s Oak Ridge National Laboratory (ORNL), the Chinese Academy of Sciences and Ohio State University. The working group’s research paper has been published in the journal Science Advances.

Now for some explanation.

In solids with magnetic ions (e.g., manganese), thermal perturbations of spins either can align with each other (ferromagnets or antiferromagnets), or not align (paramagnets). However, spins are not entirely random in paramagnets: they form short-lived, short-range, locally ordered structures – paramagnons – which exist for only a millionth of a billionth of a second and extend over only two to four atoms. In the new paper describing the work, the researchers show that despite these shortcomings, even paramagnons can move in a temperature difference and propel free electrons along with them, creating paramagnon drag thermopower.

In a proof-of-concept finding, the team observed that paramagnon drag in manganese telluride (MnTe) extends to very high temperatures and generates a thermopower that is much stronger than what electron charges alone can make.

The research team tested the concept of paramagnon drag thermopower by heating lithium-doped MnTe to approximately 250 degrees Celsius above its Néel temperature (34 degrees Celsius) – the temperature at which the spins in the material lose their long-range magnetic order and the material becomes paramagnetic.

Daryoosh Vashaee, professor of electrical and computer engineering and materials science at NC State and co-corresponding author of the paper describing the work said, “Above the Néel temperature, one would expect the thermopower being generated by the spin waves to drop off. However, we didn’t see the expected drop off, and we wanted to find out why.”

At ORNL the team used neutron spectroscopy at the Spallation Neutron Source to determine what was happening within the material.

Raphael Hermann, a materials scientist at ORNL and co-corresponding author of the paper said, “We observed that even though there were no sustained spin waves, localized clusters of ions would correlate their spins long enough to produce visible magnetic fluctuations.”

The team showed that the lifetime of these spin waves – around 30 femtoseconds – was long enough to enable the dragging of electron charges, which requires only about one femtosecond, or one quadrillionth of a second.

“The short-lived spin waves, therefore, could propel the charges and create enough thermopower to prevent the predicted drop off,” Hermann noted.

Joseph Heremans, professor of mechanical and aerospace engineering at the Ohio State University and co-corresponding author of the paper took the explanation further with, “Before this work, it was believed that magnon drag could exist only in magnetically ordered materials, not in paramagnets. Because the best thermoelectric materials are semiconductors, and because we know of no ferromagnetic semiconductor at room temperature or above, we never thought before that magnon drag could boost the thermoelectric efficiency in practical applications. This new finding changes that completely; we can now investigate paramagnetic semiconductors, of which there are a lot.”

Huaizhou Zhao, a professor at the Chinese Academy of Science in Beijing and co-corresponding author of the paper added, “When we observed the sudden rise of Seebeck coefficient below and near the Néel temperature, and this excess value extended to high temperatures, we suspected something fundamentally related to spins must be involved. So we formed a research team with complementary expertise which laid the groundwork for this discovery.”

Professor Vashaee summed up with, “Spins enable a new paradigm in thermoelectricity by alleviating the fundamental tradeoffs imposed by Pauli exclusion on electrons. Just as in the discovery of the spin-Seebeck effect, which led to the new area of spincaloritronics, where the spin angular momentum is transferred to the electrons, both the spin waves (i.e., magnons) and the local thermal fluctuations of magnetization in the paramagnetic state (i.e., paramagnons) can transfer their linear momentum to electrons and generate thermopower.”

Graduate students and co-first authors Yuanhua Zheng of the Ohio State University, Tianqi Lu of the Chinese Academy of Sciences and Mobarak H. Polash of NC State contributed equally to the work. The Spallation Neutron Source at ORNL is a DOE Office of Science User Facility. The research has been supported by the National Science Foundation, the Air Force Office of Scientific Research, and the U.S. Department of Energy Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

Humanity lets more than half of the energy and fuel used escape as heat. Harvesting that waste and using would effectively double the amount of work that could be done or cut the costs of energy and fuels.

This technology is so new that there isn’t any efficiency noted or even volt values let alone amps. But as one researcher noted, there is now the whole range of semiconductors in play for research. Something worthwhile will come of this for energy and fuel users. Your humble writers believes heat harvesting is the “holy grail” of energy and fuels in the short term or first step, making this is very good news, indeed.

Georgia Institute of Technology researchers have developed a promising new cathode and electrolyte system that replaces expensive metals and traditional liquid electrolyte with lower cost transition metal fluorides and a solid polymer electrolyte.

The growing popularity of lithium-ion batteries in recent years has put a strain on the world’s supply of cobalt and nickel, two metals integral to current battery designs, and sent prices surging.

A lithium-ion battery is shown using a promising new cathode and electrolyte system that replaces expensive metals and traditional liquid electrolyte with lower cost transition metal fluorides and a solid polymer electrolyte. Image Credit: Allison Carter, Georgia Institute of Technology. Click image for the largest view.

In an effort to develop alternative designs for lithium-based batteries with less reliance on those scarce metals, researchers at the Georgia Institute of Technology have developed a promising new cathode and electrolyte system that replaces expensive metals and traditional liquid electrolyte with lower cost transition metal fluorides and a solid polymer electrolyte.

Gleb Yushin, a professor in Georgia Tech’s School of Materials Science and Engineering explained, “Electrodes made from transition metal fluorides have long shown stability problems and rapid failure, leading to significant skepticism about their ability to be used in next generation batteries. But we’ve shown that when used with a solid polymer electrolyte, the metal fluorides show remarkable stability – even at higher temperatures – which could eventually lead to safer, lighter and cheaper lithium-ion batteries.”

In a typical lithium-ion battery, energy is released during the transfer of lithium ions between two electrodes, an anode and a cathode, with a cathode typically comprising lithium and transition metals such as cobalt, nickel and manganese. The ions flow between the electrodes through a liquid electrolyte.

For the study, published in the journal Nature Materials and sponsored by the Army Research Office, the research team fabricated a new type of cathode from iron fluoride active material and a solid polymer electrolyte nanocomposite. Iron fluorides have more than double the lithium capacity of traditional cobalt- or nickel-based cathodes. In addition, iron is 300 times cheaper than cobalt and 150 times cheaper than nickel.

To produce such a cathode, the researchers developed a process to infiltrate a solid polymer electrolyte into the prefabricated iron fluoride electrode. They then hot pressed the entire structure to increase density and reduce any voids.

Two central features of the polymer-based electrolyte are its ability to flex and accommodate the swelling of the iron fluoride while cycling and its ability to form a very stable and flexible interphase with iron fluoride. Traditionally, that swelling and massive side reactions have been key problems with using iron fluoride in previous battery designs.

Yushin said, “Cathodes made from iron fluoride have enormous potential because of their high capacity, low material costs and very broad availability of iron. But the volume changes during cycling as well as parasitic side reactions with liquid electrolytes and other degradation issues have limited their use previously. Using a solid electrolyte with elastic properties solves many of these problems.”

The researchers then tested several variations of the new solid-state batteries to analyze their performance over more than 300 cycles of charging and discharging at elevated temperature of 122° Fahrenheit, noting that they outperformed previous designs using metal fluoride even when these were kept cool at room temperatures.

The researchers found that the key to the enhanced battery performance was the solid polymer electrolyte. In previous attempts to use metal fluorides, it was believed that metallic ions migrated to the surface of the cathode and eventually dissolved into the liquid electrolyte, causing a capacity loss, particularly at elevated temperatures. In addition, metal fluorides catalyzed massive decomposition of liquid electrolytes when cells were operating above 100° Fahrenheit. However, at the connection between the solid electrolyte and the cathode, such dissolving doesn’t take place and the solid electrolyte remains remarkably stable, preventing such degradations, the researchers wrote.

Kostiantyn Turcheniuk, research scientist in Yushin’s lab and a co-author of the manuscript said, “The polymer electrolyte we used was very common, but many other solid electrolytes and other battery or electrode architectures – such as core-shell particle morphologies – should be able to similarly dramatically mitigate or even fully prevent parasitic side reactions and attain stable performance characteristics.”

In the future, the researchers aim to develop new and improved solid electrolytes to enable fast charging and also to combine solid and liquid electrolytes in new designs that are fully compatible with conventional cell manufacturing technologies employed in large battery factories.

This seems to be a major improvement to an expensive and battery life limiting situation. As the previous paragraph notes, the manufacturing base is invested in existing technology that needs worked through to get this kind of improvement to marketed products.

The press release suggests the Georgia folks have a firm grip on the handle of what needs done. The progress reported so far implies that they are going to offer manufacturers a much lower cost and better battery design for sale to consumers.

Georgia Institute of Technology researchers have developed a new platinum-based catalytic system that is far more durable than traditional commercial systems and has a potentially longer lifespan. The new system could, over the long term, reduce the cost of producing fuel cells.

Platinum has long been used as a catalyst to enable the oxidation reduction reaction at the center of fuel cell technology. But the metal’s high cost is one factor that has hindered fuel cells from competing with cheaper ways of powering automobiles and homes.

Now researchers at the Georgia Institute of Technology have developed a new platinum-based catalytic system that is far more durable than traditional commercial systems and has a potentially longer lifespan. The new system could, over the long term, reduce the cost of producing fuel cells.

In the study, which was published in the ACS journal Nano Letters, the researchers described a possible new way to solve one of the key causes of degradation of platinum catalysts, sintering, a process in which particles of platinum migrate and clump together, reducing the specific surface area of the platinum and causing the catalytic activity to drop.

To reduce such sintering, the researchers devised a method to anchor the platinum particles to their carbon support material using bits of the element selenium.

Zhengming Cao, a visiting graduate student at Georgia Tech said, “There are strategies out there to mitigate sintering, such as using platinum particles that are uniform in size to reduce chemical instability among them. This new method using selenium results in a strong metal-support interaction between platinum and the carbon support material and thus remarkably enhanced durability. At the same time, the platinum particles can be used and kept at a small to attain high catalytic activity from the increased specific surface area.”

The process starts by loading nanoscale spheres of selenium onto the surface of a commercial carbon support. The selenium is then melted under high temperatures so that it spreads and uniformly covers the surface of the carbon. Then, the selenium is reacted with a salt precursor to platinum to generate particles of platinum smaller than two nanometers in diameter and evenly distributed across the carbon surface.

The covalent interaction between the selenium and platinum provides a strong link to stably anchor the platinum particles to the carbon.

Younan Xia, professor and Brock Family Chair in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University added, “The resulting catalyst system was remarkable both for its high activity as a catalyst as well as its durability.”

Because of the increased specific surface area of the nanoscale platinum, the new catalytic system initially showed catalytic activity three and a half times higher than the pristine value of a state-of-the-art commercial platinum-carbon catalyst. Then, the research team tested the catalytic system using an accelerated durability test. Even after 20,000 cycles of electropotential sweeping, the new system still provided a catalytic activity more than three times that of the commercial system.

The researchers used transmission electron microscopy at different stages of the durability test to examine why catalytic activity remained so high. They found that the selenium anchors were effective in keeping most of the platinum particles in place.

“After 20,000 cycles, most of the particles remained on the carbon support without detachment or aggregation,” Cao said. “We believe this type of catalytic system holds great potential as a scalable way to increase the durability and activity of platinum catalysts and eventually improve the feasibility of using fuel cells for a wider range of applications.”

Without doubt the cost of platinum is a large and deep set anchor on fuel cell adoption. Most alternatives while cheaper are not commercial for a variety of reasons, some of which may make it to market someday.

But 20,000 cycles is a new and amazing change in perspective. 20,000 cycles over / 365 days = 54.8 years. That offers a very different amortization result. Still the initial capital investment is a major hurdle. Not something a family or small business is likely to entertain.

Rice University researchers have built a electrocatalysis reactor that recycles carbon dioxide to produce pure liquid fuel solutions using electricity. The scientists behind the invention hope it will become an efficient and profitable way to recycle and reuse CO2.

The CO2 could be repurposed in an efficient and environmentally friendly way with the new electrolyzer that uses renewable electricity to produce pure liquid fuels.

Schematic illustration of the CO2 reduction cell with solid electrolyte. Image Credit: Rice University. Click image for a larger view.

The catalytic reactor developed by the Rice University lab of chemical and biomolecular engineer Haotian Wang uses carbon dioxide as its feedstock and, in its latest prototype, produces highly purified and high concentrations of formic acid.

Formic acid produced by traditional carbon dioxide devices needs costly and energy-intensive purification steps Wang explained. The direct production of pure formic acid solutions will help to promote commercial carbon dioxide conversion technologies.

The Wang group’s study paper has been published in Nature Energy.

Wang, who joined Rice’s Brown School of Engineering in January, and his group pursue technologies that turn greenhouse gases into useful products. In tests, the new electrocatalyst reached an energy conversion efficiency of about 42%. That means nearly half of the electrical energy can be stored in formic acid as liquid fuel.

“Formic acid is an energy carrier,” Wang said. “It’s a fuel-cell fuel that can generate electricity and emit carbon dioxide – which you can grab and recycle again.”

“It’s also fundamental in the chemical engineering industry as a feedstock for other chemicals, and a storage material for hydrogen that can hold nearly 1,000 times the energy of the same volume of hydrogen gas, which is difficult to compress,” he said. “That’s currently a big challenge for hydrogen fuel-cell cars.”

Two advances made the new device possible, said lead author and Rice postdoctoral researcher Chuan Xia. The first was his development of a robust, two-dimensional bismuth catalyst and the second a solid-state electrolyte that eliminates the need for salt as part of the reaction.

“Bismuth is a very heavy atom, compared to transition metals like copper, iron or cobalt,” Wang said. “Its mobility is much lower, particularly under reaction conditions. So that stabilizes the catalyst.” He noted the reactor is structured to keep water from contacting the catalyst, which also helps preserve it.

Xia can make the nanomaterials in bulk. “Currently, people produce catalysts on the milligram or gram scales,” he said. “We developed a way to produce them at the kilogram scale. That will make our process easier to scale up for industry.”

The polymer-based solid electrolyte is coated with sulfonic acid ligands to conduct positive charge or amino functional groups to conduct negative ions.

“Usually people reduce carbon dioxide in a traditional liquid electrolyte like salty water,” Wang said. “You want the electricity to be conducted, but pure water electrolyte is too resistant. You need to add salts like sodium chloride or potassium bicarbonate so that ions can move freely in water.”

“But when you generate formic acid that way, it mixes with the salts,” he said. “For a majority of applications you have to remove the salts from the end product, which takes a lot of energy and cost. So we employed solid electrolytes that conduct protons and can be made of insoluble polymers or inorganic compounds, eliminating the need for salts.”

The rate at which water flows through the product chamber determines the concentration of the solution. Slow throughput with the current setup produces a solution that is nearly 30% formic acid by weight, while faster flows allow the concentration to be customized. The researchers expect to achieve higher concentrations from next-generation reactors that accept gas flow to bring out pure formic acid vapors.

The Rice lab worked with Brookhaven National Laboratory to view the process in progress. “X-ray absorption spectroscopy, a powerful technique available at the Inner Shell Spectroscopy (ISS) beamline at Brookhaven Lab’s National Synchrotron Light Source II, enables us to probe the electronic structure of electrocatalysts in operando – that is, during the actual chemical process,” said co-author Eli Stavitski, lead beamline scientist at ISS. “In this work, we followed bismuth’s oxidation states at different potentials and were able to identify the catalyst’s active state during carbon dioxide reduction.”

With its current reactor, the lab generated formic acid continuously for 100 hours with negligible degradation of the reactor’s components, including the nanoscale catalysts. Wang suggested the reactor could be easily retooled to produce such higher-value products as acetic acid, ethanol or propanol fuels.

“The big picture is that carbon dioxide reduction is very important for its effect on global warming as well as for green chemical synthesis,” Wang said. “If the electricity comes from renewable sources like the sun or wind, we can create a loop that turns carbon dioxide into something important without emitting more of it.”

Co-authors are Rice graduate student Peng Zhu; graduate student Qiu Jiang and Husam Alshareef, a professor of material science and engineering, at King Abdullah University of Science and Technology, Saudi Arabia (KAUST); postdoctoral researcher Ying Pan of Harvard University; and staff scientist Wentao Liang of Northeastern University. Wang is the William Marsh Rice Trustee Assistant Professor of Chemical and Biomolecular Engineering. Xia is a J. Evans Attwell-Welch Postdoctoral Fellow at Rice.

Rice and the U.S. Department of Energy Office of Science User Facilities supported the research.

This work is likely to have a major impact over time. Recycling CO2 back into a fuel source has immense potential and helps moderate the expectation of higher fuel prices out into the future. Like all possible disruptive technologies, the cost of the product is paramount, so driving to low cost efficiency is key.

The other takeaway is the potential to store hydrogen. The smallest atom as a fuel market has yet to find a practical and economical means of storage, This tech might well find its path into the market in this field instead.

Lets hope there is much more to come from this group. They’re bumped into two future fuel markets in need of their technology’s success.


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