University of Toronto Faculty of Applied Science & Engineering’s engineering team has adapted technology from fuel cells to do the reverse: harness electricity to make valuable chemicals from waste carbon (CO2). Usual fuel cells turn chemicals into electricity, now the technology has been reversed.

Professor Ted Sargent, one of the senior authors of the paper published in Science said, “For decades, talented researchers have been developing systems that convert electricity into hydrogen and back again. Our innovation builds on that legacy, but by using carbon-based molecules, we can plug directly into existing hydrocarbon infrastructure.”

In the improved electrolyzer, the reaction happens in a thin layer that combines a copper-based catalyst with Nafion, an ion-conducting polymer. The unique arrangement of these materials provides a reaction rate 10 times higher than previous designs. Image Credit: Daria Perevezentsev, University of Toronto. Click image for the largest view.

In a hydrogen fuel cell, hydrogen and oxygen come together on the surface of a catalyst. The chemical reaction releases electrons, which are captured by specialized materials within the fuel cell and fed into a circuit.

The opposite of a fuel cell is an electolyzer, which uses electricity to drive a chemical reaction. The paper’s authors are experts in designing electrolyzers that convert CO2 into other carbon-based molecules, such as ethylene. The team includes PhD candidate Adnan Ozden, who is supervised by Professor David Sinton, as well as several members of Sargent’s team, including PhD candidate Joshua Wicks, postdoctoral fellow F. Pelayo García de Arquer and former postdoctoral fellow Cao-Thang Dinh.

“Ethylene is one of the most widely produced chemicals in the world,” said Wicks. “It’s used to make everything from antifreeze to lawn furniture. Today it is derived from fossil fuels, but if we could instead make it by upgrading waste CO2, it would provide a new economic incentive for capturing carbon.”

Today’s electrolyzers do not yet produce ethylene on a scale large enough to compete with what is derived from fossil fuels. Part of the challenge lies in the unique nature of the chemical reaction that transforms CO2 into ethylene and other carbon-based molecules.

Ozden explained, “The reaction requires three things: CO2, which is a gas; hydrogen ions, which come from liquid water; and electrons, which are transmitted through a metal catalyst. Bringing those three different phases – especially the CO2 – together quickly is challenging, and that is what has limited the rate of the reaction.”

In their latest electrolyzer design, the team used a unique arrangement of materials to overcome the challenges of bringing the reactants together. Electrons are delivered using a copper-based catalyst that the team had previously developed. But instead of a flat sheet of metal, the catalyst in the new electrolyzer is in the form of small particles embedded within a layer of a material known as Nafion.

Nafion is an ionomer – a polymer that can conduct charged particles known as ions. Today, it is commonly used in fuel cells, where its role is to transport positively charged hydrogen (H+) ions around within the reactor.

García de Arquer said, “In our experiments, we discovered that a certain arrangement of Nafion can facilitate the transport of gases such as CO2. Our design enables gas reactants to reach the catalyst surface fast enough and in a sufficiently distributed manner to significantly increase the rate of reaction.”

With the reaction no longer limited by how quickly the three reactants can come together, the team was able to transform CO2 into ethylene and other products 10 times faster than before. They accomplished this without reducing the overall efficiency of the reactor, meaning more product for roughly the same capital cost.

Despite the advance, the device remains a long way from commercial viability. One of the major remaining challenges has to do with the stability of the catalyst under the new higher-current densities.

“We can pump in electrons 10 times faster, which is great, but we can only operate the system for about ten hours before the catalyst layer breaks down,” said Dinh. “This is still far from the target of thousands of hours that would be needed for industrial application.”

Dinh, who is now a professor of chemical engineering at Queen’s University, is continuing the work by looking into new strategies for stabilizing the catalyst layer, such as further modifying the chemical structure of the Nafion or adding additional layers to protect it.

The other team members plan to work on different challenges, such as optimizing the catalyst to produce other commercially valuable products beyond ethylene.

“We picked ethylene as an example, but the principles here can be applied to the synthesis of other valuable chemicals, including ethanol” said Wicks. “In addition to its many industrial uses, ethanol is also widely used as a fuel.”

The ability to produce fuels, building materials and other products in a carbon-neutral way is an important step towards reducing our dependence on fossil fuels.

“Even if we stop using oil for energy, we are still going to need all of these molecules,” says García de Arquer. “If we can produce them using waste CO2 and renewable energy, we can have a major impact in terms of decarbonizing our economy.”

This team is definitely on to something. But like others who are working on recycling CO2 the costs have to get down, way down. The low cost of fossil fuels helps to incentivize the progress. The goal could be recycle the effluent gases at a power plant and reuse the fuel a second time. That would cut the need for fossil fuels.

The problem runs a bit deeper than the life span of the catalyst kit. The team reports that they are using 1.3 amps per square centimeter, but not mentioning the volts, leaving us without the watts involved, a critical metric to understand the input costs.

This is a worthwhile pursuit, perhaps the solution is on this path. Someday, some idea is going to get us there.

University of California – San Diego researchers have developed an ultrasound-emitting device that brings lithium metal batteries, or LMBs, one step closer to commercial viability. Although the research team focused on LMBs, the device can be used in any battery, regardless of the chemistry.

Ultrasound emitting device designed at University of California – San Diego Jacobs School of Engineering. Image Credit: UCSD. Click image for the largest view.

The device that the researchers developed is an integral part of the battery and works by emitting ultrasound waves to create a circulating current in the electrolyte liquid found between the anode and cathode. This prevents the formation of lithium metal growths, called dendrites, during charging that lead to decreased performance and short circuits in LMBs.

The device is made from off-the-shelf smartphone components, which generate sound waves at extremely high frequencies – ranging from 100 million to 10 billion hertz. In phones, these devices are used mainly to filter the wireless cellular signal and identify and filter voice calls and data. The researchers used them instead to generate a flow within the battery’s electrolyte.

James Friend, a professor of mechanical and aerospace engineering at the Jacobs School of Engineering at UC San Diego and the study’s corresponding author said, “Advances in smartphone technology are truly what allowed us to use ultrasound to improve battery technology.”

Currently, LMBs have not been considered a viable option to power everything from electric vehicles to electronics because their lifespan is too short. But these batteries also have twice the capacity of today’s best lithium ion batteries. For example, lithium metal-powered electric vehicles would have twice the range of lithium ion powered vehicles, for the same battery weight.

The researchers showed that a lithium metal battery equipped with the device could be charged and discharged for 250 cycles and a lithium ion battery for more than 2000 cycles. The batteries were charged from zero to 100 percent in 10 minutes for each cycle.

Ping Liu, professor of nanoengineering at the Jacobs School and the paper’s other senior author said, “This work allows for fast-charging and high energy batteries all in one. It is exciting and effective.”

The team detailed their work in the journal Advanced Materials.

Most battery research efforts focus on finding the perfect chemistry to develop batteries that last longer and charge faster, Liu said. By contrast, the UC San Diego team sought to solve a fundamental issue: the fact that in traditional metal batteries, the electrolyte liquid between the cathode and anode is static. As a result, when the battery charges, the lithium ion in the electrolyte is depleted, making it more likely that lithium will deposit unevenly on the anode. This in turn causes the development of needle-like structures called dendrites that can grow unchecked from the anode towards the cathode, causing the battery to short circuit and even catch fire. Rapid charging speeds this phenomenon up.

By propagating ultrasound waves through the battery, the device causes the electrolyte to flow, replenishing the lithium in the electrolyte and making it more likely that the lithium will form uniform, dense deposits on the anode during charging.

The most difficult part of the process was designing the device, said An Huang, the paper’s first author and a Ph.D. student in materials science at UC San Diego. The challenge was working at extremely small scales, understanding the physical phenomena involved and finding an effective way to integrate the device inside the battery.

Haodong Liu, the paper’s co-author and a nanoengineering postdoctoral researcher at the Jacobs School said, “Our next step will be to integrate this technology into commercial lithium ion batteries.”

The technology has been licensed from UC San Diego by Matter Labs, a technology development firm based in Ventura, Calif. The license is not exclusive.

The work was funded by the U.S. Department of Energy and the Accelerating Innovation to Market team at UC San Diego. It is protected by patents: US#16/331,741 — “Acoustic wave based dendrite prevention for rechargeable batteries” and provisional# 2019-415 — “Chemistry-agnostic prevention of ion depletion and dendrite prevention in liquid electrolyte.”

Your humble writer would like to suggest this is a breakthrough at zero to 100% charging in 10 minutes. Should that be scaleable to commercial batteries the electric vehicle market will be very disrupted, indeed.

Perhaps even more interesting will be the application of this technology to other battery chemistries.

My heavens . . . 2000 charge cycles?

University of Washington researchers are at work on a simpler fuel efficient rocket engine that could be cheaper and enable lighter spacecraft. The researchers have developed a mathematical model that describes how rotating detonation engines work.

It takes a lot of fuel to launch something into space. Sending NASA’s Space Shuttle into orbit required more than 3.5 million pounds of fuel.

But a new type of engine – called a rotating detonation engine – promises to make rockets not only more fuel-efficient but also more lightweight and less complicated to construct. There’s just one problem: Right now this engine is too unpredictable to be used in an actual rocket.

Section view of the rotating detonation engine (RDE) used for this study. The engine geometry is such that gaseous methane and oxygen are directed into a narrow annular gap through a set of propellant injectors. A spark plug ignites the mixture, which rapidly transitions to a number of circumferentially traveling detonation waves. Image Credit: Credit: Koch et al./Physical Review E. Click image for the largest view.

Researchers at the University of Washington have developed a mathematical model that describes how these engines work. With this information, engineers can, for the first time, develop tests to improve these engines and make them more stable. The team published these findings in Physical Review E.

Lead author James Koch, a UW doctoral student in aeronautics and astronautics starts us with, “The rotating detonation engine field is still in its infancy. We have tons of data about these engines, but we don’t understand what is going on. I tried to recast our results by looking at pattern formations instead of asking an engineering question – such as how to get the highest performing engine – and then boom, it turned out that it works.”

A conventional rocket engine works by burning propellant and then pushing it out of the back of the engine to create thrust.

“A rotating detonation engine takes a different approach to how it combusts propellant,” Koch explained. “Its made of concentric cylinders. Propellant flows in the gap between the cylinders, and, after ignition, the rapid heat release forms a shock wave, a strong pulse of gas with significantly higher pressure and temperature that is moving faster than the speed of sound.”

“This combustion process is literally a detonation – an explosion – but behind this initial start-up phase, we see a number of stable combustion pulses form that continue to consume available propellant. This produces high pressure and temperature that drives exhaust out the back of the engine at high speeds, which can generate thrust.”

Conventional rocket engines use a lot of machinery to direct and control the combustion reaction so that it generates the work needed to propel the engine. But in a rotating detonation engine, the shock wave naturally does everything without needing additional help from engine parts.

Koch noted the situation with, “The combustion-driven shocks naturally compress the flow as they travel around the combustion chamber. The downside of that is that these detonations have a mind of their own. Once you detonate something, it just goes. It’s so violent.”

To try to be able to describe how these engines work, the researchers first developed an experimental rotating detonation engine where they could control different parameters, such as the size of the gap between the cylinders. Then they recorded the combustion processes with a high-speed camera. Each experiment took only a 0.5 second to complete, but the researchers recorded these experiments at 240,000 frames per second so they could see what was happening in slow motion.

The researchers developed an experimental rotating detonation engine (shown here) where they could control different parameters, such as the size of the gap between the cylinders. The feed lines (right) direct the propellant flow into the engine. On the inside, there is another cylinder concentric to the outside piece. Sensors sticking out of the top of the engine (left) measure pressure along the length of the cylinder. The camera would be on the left-hand side, looking from the back end of the engine. Image Credit: James Koch/University of Washington. Click image for the largest view.

From there, the researchers developed a mathematical model to mimic what they saw in the videos.

“This is the only model in the literature currently capable of describing the diverse and complex dynamics of these rotating detonation engines that we observe in experiments,” said co-author J. Nathan Kutz, a UW professor of applied mathematics.

The model allowed the researchers to determine for the first time whether an engine of this type would be stable or unstable. It also allowed them to assess how well a specific engine was performing.

Co-author Carl Knowlen, a UW research associate professor in aeronautics and astronautics offers this view, “This new approach is different from conventional wisdom in the field, and its broad applications and new insights were a complete surprise to me.”

Right now the model is not quite ready for engineers to use.

Koch said, “My goal here was solely to reproduce the behavior of the pulses we saw – to make sure that the model output is similar to our experimental results,” Koch said. “I have identified the dominant physics and how they interplay. Now I can take what I’ve done here and make it quantitative. From there we can talk about how to make a better engine.”

Mitsuru Kurosaka, a UW professor of aeronautics and astronautics, is also a co-author on this paper. This research was funded by the U.S. Air Force Office of Scientific Research and the Office of Naval Research.

This promises to be quite an improvement in rocket engines, the vehicles and the payloads. One could expect some reduction in costs as well to lift materials into orbit. There will likely be some other applications and the limit might not apply to rocket engine combustion as well. This is going to be very interesting indeed.

Of other interest is the serendipity of the research team having the brain storm to have a different look instead of conventional thinking. For that, the Congratulations are more than earned, they are deserved.

Université de Genève researchers have studied the seismic activity linked to a geothermal drilling in search of supercritical fluids. The concern is destabilizing the precarious equilibrium at depth with geothermal wells may reactivate the geological layers causing earthquakes. They discovered that the drilling did not cause uncontrolled seismic activity. This drilling under such critical conditions suggests that the technology is on the verge of mastering geothermal energy, paving the way for new sources of non-polluting heat and electricity.

View of the Venelle-2 well. The well was designed to sample supercritical fluids. Image Credit: Université de Genève © Riccardo Minetto. Click image for the largest view.

How can we meet the growing energy demand while reducing our use of polluting fossil fuels? Geothermal energy is an efficient, non-polluting solution but in certain cases geothermal operations must be handled with care. Reaching the most powerful sources of available energy means drilling deep into the layers of the earth’s crust to find geothermal fluids with high energy content (hot water and gas released by magma). Yet, the deeper we drill the greater are the subsurface unknowns controlling the stability of the Earth’s crust. Destabilizing the precarious equilibrium at depth with geothermal wells may reactivate the geological layers causing earthquakes.

Researchers at the University of Geneva (UNIGE), Switzerland, working in collaboration with the University of Florence and the National Research Council (CNR) in Italy, have studied the seismic activity linked to a geothermal drilling in search of supercritical fluids.  Their study report has been published in Journal of Geophysical Research: Solid Earth.

A number of countries, including Switzerland, are already exploiting geothermal energy to produce heat from shallow wells. Down to 1,500 meters such technology normally presents little risk. “To generate electricity, however, we have to drill deeper, which is both a technological and a scientific challenge,” pointed out Matteo Lupi, a professor in the Department of Earth Sciences in UNIGE’s Faculty of Science. In fact, drilling deeper than 1,500 meters requires special care because the unknown factors relating to the subsurface increase. “Below these depths, the stability of the drilling site is more and more difficult and poor decisions could trigger an earthquake,” he said.

The Larderello geothermal field in Tuscany – the world’s oldest – currently produces 10% of the world’s total geothermal electricity supply. We know that at about 3,000 meters depth, we reach a geological layer marked by a seismic reflector, where it is thought that supercritical fluids may be found. Supercritical fluids yield an enormous amount of renewable energy. The term supercritical implies an undefined phase state – neither fluids nor gaseous – and boast a very powerful energy content.

Riccardo Minetto, a researcher in UNIGE’s Department of Earth Sciences explained, “Engineers have been trying since the 1970s to drill down to this famous level at 3,000 meters in Larderello but they still haven’t succeeded. What’s more, we still don’t know exactly what this bed is made up of: is it a transition between molten and solid rocks? Or does it consist of cooled granites releasing fluids trapped at this level?”

The technology is becoming ever more sophisticated. Because of this geothermal drilling in search of supercritical conditions has been attempted once more at Larderello-Tavale.

The aim? Deepening a wellbore few centimeters wide to a depth of 3,000 meters to tap these supercritical fluids. “This drilling, which formed part of the European DESCRAMBLE project, was unique because it targeted the suggested transition between rocks in a solid and molten state,” noted professor Lupi.

The Geneva team set up eight seismic stations around the well within a radius of eight kilometers to measure the impact of the drilling on seismic activity. As the drilling progressed, the geophysicists collected the data and analyzed each difficulty that was encountered.

“The good news is that for the very first time, drilling in search of supercritical fluids caused only minimal seismic disturbance, which was a feat in such conditions and a strong sign of the technological progress that has been made,” explained professor Lupi.

His team used the eight seismic stations to distinguish between the natural seismic activity and the very weak events caused by the drilling. The threshold of 3,000 meters, however, was not reached. “The engineers had to stop about 250 meters from this level as a result of the extremely high temperature increase – over 500 degrees. There’s still room for technical progress on this point,” said Minetto.

This study indicates that the supercritical drilling went well and that the technology is close to being mastered. “Until now, anyone who had tried to sink a well in supercritical conditions did not succeed because of the high temperatures but the results here are extremely encouraging,” said professor Lupi.

Switzerland is itself very active in promoting geothermal energy. This renewable source of energy if developed further would share some of the burden of the country’s hydropower, solar and windpower. “Geothermal energy could be one of the main sources of energy of our future, so it’s only right to promote future investments to develop it further and safely,” concluded the Geneva-based researcher.

One has to admire this group. Drilling that deep into hard rock is quite a feat in itself, not to mention how hot it got. The pressures in the well bore couldn’t be known nor how deep they would get before the temperatures and pressures would bring them to a stop.

The got close, real close. Congratulations to this team! Next up, very high temperature rock drilling technology.

Research leader Dorthe Bomholdt Ravnsbæk of the Department of Physics, Chemistry and Pharmacy at University of Southern Denmark pointed out, “The Na-ion battery is still under development, and researchers are working on increasing its service life, lowering its charging time and making batteries that can deliver many watts.”

Now the race is on to develop even more efficient and rechargeable batteries for the future. One promising option is to make batteries based on sodium, which is found in abundance in seawater. We all know the rechargeable and efficient lithium ion (Li-ion) batteries sitting in our smartphones, laptops and also in electric cars.

Unfortunately, lithium is a limited resource, so it will be a challenge to satisfy the worlds’ growing demand for relatively cheap batteries. Therefore, researchers are now looking for alternatives to the Li-ion battery.

A promising alternative is to replace lithium with the metal sodium – to make Na-ion batteries. Sodium is found in large quantities in seawater and can be easily extracted from it.

Substitution of 10–20% of the Fe by Mn enhances the capacity by >15%. The size of the discontinuous volume change can be effectively reduced by substitution of Mn onto the Fe sites. Image Credit: University of Southern Denmark. Click image for the largest view.

Ravnsbæk and her team are preoccupied with developing new and better rechargeable batteries that can replace today’s’ widely used Li-ion batteries.

For the Na-ion batteries to become an alternative, better electrode materials must be developed, something she and colleagues from the University of Technology and the Massachusetts Institute of Technology, USA, have looked at in a new study published in the journal ACS Applied Energy Materials.

But before looking at the details of this study, let’s take a look at why the Na-ion battery has the potential to become the next big battery success.

“An obvious advantage is that sodium is a very readily available resource, which is found in very large quantities in seawater. Lithium, on the other hand, is a limited resource that is mined only in a few places in the world,” explained Ravnsbæk.

Another advantage is that Na-ion batteries do not need cobalt, which is still needed in Li-ion batteries. The majority of the cobalt used today to make Li-ion batteries, is mined in the Democratic Republic of Congo, where rebellion, disorganized mining and child labor create uncertainty and moral qualms regarding the country’s cobalt trade.

It also counts on the plus side that Na-ion batteries can be produced at the same factories that make Li-ion batteries today.

In their new study, Ravnsbæk and her colleagues have investigated a new electrode material based on iron, manganese and phosphorus.

The new thing about the material is the addition of the element manganese, which not only gives the battery a higher voltage, but also increases the capacity of the battery and is likely to deliver more watts. This is because the transformations that occur at the atomic level during the discharge and charge are significantly changed by the presence of manganese.

“Similar effects have been seen in Li-ion batteries, but it is very surprising that the effect is retained in a Na-ion battery, since the interaction between the electrode and Na-ions is very different from that of Li-ions,” said Ravnsbæk.

She will not try and predict when we can expect to find seawater-based Na-ion batteries in our phones and electric cars, because there are still some challenges to be solved.

One challenge is that it can be difficult to make small Na-ion batteries. But large batteries also have value. One example is when it comes to storing wind or solar energy.

Thus, in 2019, such a gigantic 100 kWh Na-ion battery was inaugurated to be tested by Chinese scientists at the Yangtze River Delta Physics Research Center. The giant battery consists of more than 600 connected Na-ion battery cells, and it supplies power to the building that houses the center. The current stored in the battery is surplus current from the main grid.

It will be a boon to consumers when lithium gets capable competition as well as taking the pressure off materials producers. The cobalt mining issue is rife with horror stories involving children in a country of intense corruption and lack of care for human life.

It will be interesting to see how a well developed sodium battery compares to lithium-ion. There is room for both chemistries in the market and each will have its own leading features. With low cost materials and production possible in existing facilities sodium could launch pretty quickly when scale up is completely understood.


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