An interdisciplinary research team at the Technical University of Munich (TUM) has built platinum nanoparticles for catalysis in fuel cells: The new size-optimized catalysts are twice as good as the best process commercially available today.

Fuel cells might well replace batteries as the power source for electric cars. They consume hydrogen, a gas which could be produced for example using surplus electricity from wind power plants. However, the platinum used in fuel cells is rare and extremely expensive, which has been a limiting factor in applications up to now.

A research team at the Technical University of Munich (TUM) led by Roland Fischer, Professor for Inorganic and Organometallic Chemistry, Aliaksandr Bandarenka, Physics of Energy Conversion and Storage and Alessio Gagliardi, Professor for Simulation of Nanosystems for Energy Conversion, has now optimized the size of the platinum particles to such a degree that the particles perform at levels twice as high as the best fuel cell processes commercially available today.

Platin-nanoparticles with 40 atoms.  Image Credit: B. Garlyyev / TUM. Click image for the largest view.

The team’s research paper has been published in Angewandte Chemie International Edition.

In fuel cells, hydrogen reacts with oxygen to produce water, generating electricity in the process. Sophisticated catalysts at the electrodes are required in order to optimize this conversion. Platinum plays a central role in the oxygen-reduction reaction.

Searching for an ideal solution, the team created a computer model of the complete system. The central question: How small can a cluster of platinum atoms be and still have a highly active catalytic effect? “It turns out that there are certain optimum sizes for platinum stacks,” explained Fischer.

Particles measuring about one nanometer and containing approximately 40 platinum atoms are ideal. “Platinum catalysts of this order of size have a small volume but a large number of highly active spots, resulting in high mass activity,” said Bandarenka.

Interdisciplinary collaboration at the Catalysis Research Center (CRC) was an important factor in the research team’s results. Combining theoretical capabilities in modeling, joint discussions and physical and chemical knowledge gained from experiments ultimately resulted in a model showing how catalysts can be designed with the ideal form, size and size distribution of the components involved.

In addition, the CRC also has the expertise needed to create and experimentally test the calculated platinum nano-catalysts. “This takes a lot in terms of the art of inorganic synthesis,” said Kathrin Kratzl, together with Batyr Garlyyev and Marlon Rück, one of the three lead authors of the study.

The experiment exactly confirmed the theoretical predictions. “Our catalyst is twice as effective as the best conventional catalyst on the market,” said Garlyyev, adding that this is still not adequate for commercial applications, since the current 50 percent reduction of the amount of platinum would have to increase to 80 percent.

In study beyond spherical nanoparticles, the researchers hope for even higher catalytic activity from significantly more complex shapes. And the computer models established in the partnership are ideal for this kind of modeling. “Nevertheless, more complex shapes require more complex synthesis methods,” said Bandarenka. This will make computational and experimental studies more and more important in the future.

Somehow your humble writer has a difficult time expecting platinum will have a catalytic role to play in mass market products. If the nirvana of platinum activity is reached, the market volumes in platinum use will rise pushing demand of a very small supply and the cost of devices and products will increase as well. One has to hope that this team’s superlative work will be applied to other potential catalysts and a mass market fuel cell catalyst will become a consumer item someday.

Ecole Polytechnique Fédérale de Lausanne (EPFL) researchers have developed a method that uses artificial intelligence to design next-generation heat-pump compressors. Their method can cut the pumps’ power requirement by around 25%.

In Switzerland, 50 to 60% of new homes are equipped with heat pumps. These systems draw in thermal energy from the surrounding environment – such as from the ground, air, or a nearby lake or river – and turn it into heat for buildings.

While today’s heat pumps generally work well and are environmentally friendly, they still have substantial room for improvement. For example, by using microturbocompressors instead of conventional compression systems, engineers can reduce heat pumps’ power requirement by 20-25% as well as their impact on the environment. That’s because turbocompressors are more efficient and ten times smaller than piston devices.

Image Credit: Ecole Polytechnique Fédérale de Lausanne. Click image for the largest view.

But incorporating these mini components into heat pumps’ designs is not easy. Complications arise from their tiny diameters (<20 mm) and fast rotation speeds (>200,000 rpm).

At EPFL’s Laboratory for Applied Mechanical Design on the Microcity campus, a team of researchers led by Jürg Schiffmann has developed a method that makes it easier and faster to add turbocompressors to heat pumps. Using a machine-learning process called symbolic regression, the researchers came up with simple equations for quickly calculating the optimal dimensions of a turbocompressor for a given heat pump.

Their research just won the Best Paper Award at the 2019 Turbo Expo Conference held by the American Society of Mechanical Engineers.  The paper has been published in Journal of Engineering for Gas Turbines and Power.

The researchers’ method drastically simplifies the first step in designing turbochargers. This step, which involves roughly calculating the ideal size and rotation speed for the desired heat pump, is extremely important because a good initial estimate can considerably shorten the overall design time. Until now, engineers have been using design charts to size their turbocompressors – but these charts become increasingly inaccurate the smaller the equipment. And the charts have not kept up to date with the latest technology.

That’s why two EPFL PhD students – Violette Mounier and Cyril Picard – worked on developing an alternative. They fed the results of 500,000 simulations into machine-learning algorithms and generated equations that replicate the charts but with several advantages: they are reliable even at small turbocompressor sizes; they are just as detailed as more complicated simulations; and they are 1,500 times faster. The researchers’ method also lets engineers skip some of the steps in conventional design processes. It paves the way to easier implementation and more widespread use of microturbochargers in heat pumps.

Conventional heat pumps use pistons to compress a gas called a refrigerant, and drive a vapor-compression cycle. The pistons need to be well-oiled to function properly, but the oil can stick to the heat exchanger walls and impairs the heat transfer process. However, microturbocompressors – which have diameters of just a few dozen millimeters – can run without oil; they rotate on gas bearings at speeds of hundreds of thousands of rpm. The rotating movement and gas layers between the components mean there is almost no friction. As a result, these miniature systems can boost heat pumps’ heat transfer coefficients by 20-30%.

This microturbocharger technology has been in development for several years and is now mature. “We have already been contacted by several companies that are interested in using our method,” said Schiffmann. Thanks to the researchers’ work, companies will have an easier time incorporating the microturbocharger technology into their heat pumps.

A 20 to 30% power demand reduction is a huge improvement. Heat pumps are a great way to provide heating if there is a source nearby that can provide the heat economically. Across much of the U.S. that is the case, particularly where geosources are used. Lets hope this technology is affordable and used by manufacturers to cut the homeowner’s costs for winter heating and industrial low temperature needs.

New research at The University of Texas at Austin (UT) shows that injecting air and carbon dioxide into methane ice deposits buried beneath the Gulf of Mexico could unlock vast natural gas energy resources while helping fight climate change by trapping the carbon dioxide underground.

Methane hydrate is sometimes called “the ice that burns” because the warming hydrates release enough methane to sustain a flame. Image Credit: US Geological Survey. Click image for the largest view.

The study, published in the journal Water Resources Research, used computer models to simulate what happens when mixtures of carbon dioxide and air are injected into deposits of methane hydrate, an ice-like, water-rich chemical compound that forms naturally in high-pressure, low-temperature environments, such as deep in the Gulf of Mexico and under Arctic permafrost.

Lead author Kris Darnell, a recent doctoral graduate from the UT Jackson School of Geosciences, said the research is the next step in solving two significant global challenges: energy security and carbon storage.

“Our study shows that you can store carbon dioxide in hydrates and produce energy at the same time,” said Darnell, whose research was funded by the University of Texas Institute for Geophysics (UTIG).

In the process, the nitrogen in the injected air sweeps the methane toward a production well and allows carbon dioxide to take its place, researchers said. The beauty of this approach is that it extracts natural gas from methane hydrate deposits and at the same time stores carbon dioxide in a deep environment where it is unlikely to be released into the atmosphere where it could contribute to climate change.

This is not the first time that hydrate deposits have been proposed for carbon dioxide storage. Earlier attempts either failed or produced lackluster results. The new study breaks down the physics behind the process to reveal why previous attempts failed and how to get it right.

The next step, said Darnell, is to test their findings in a lab. The Jackson School and the UT Hildebrand Department of Petroleum and Geosystems Engineering are currently testing the method in a specialized facility in the Jackson School, which is one of the few in the world that can store and test methane hydrate. This work is being led by Peter Flemings, a Jackson School professor and senior UTIG research scientist, and David DiCarlo, a professor in the Hildebrand Department. Both are co-authors on the paper.

“Two things are really cool. First, we can produce natural gas to generate energy and sequester CO2,” said Flemings. “Second, by swapping the methane hydrate with CO2 hydrate, we disturb the (geologic) formation less, lowering the environmental impact, and we make the process energetically more efficient.”

If the process can be shown to work in the field on an industrial scale, it has enormous potential.

Methane hydrate is one of a group of chemical compounds known as gas hydrates in which gas molecules become trapped inside cages of water ice molecules rather than chemically bonding with them. UT and the U.S. Department of Energy (DOE) are working together to study naturally forming methane hydrates with the aim of figuring out their potential as an energy resource. This is important because estimates suggest that methane harvested from hydrate deposits found beneath the Gulf of Mexico alone could power the country for hundreds of years.

In the paper, the authors showed that a process in which one type of molecule trapped in hydrate is exchanged for another (called guest molecule exchange) is a two-stage process and not a single, simultaneous process, as it was previously thought to be.

First, nitrogen breaks down the methane hydrate. Second, the carbon dioxide crystalizes into a slow-moving wave of carbon dioxide hydrate behind the escaping methane gas.

The computer simulations indicate that the process can be repeated with increasing concentrations of carbon dioxide until the reservoir becomes saturated. The authors said that unlike some methods of carbon storage, this provides a ready incentive for industry to begin storing carbon dioxide, a major driver of climate change.

“We’re now openly inviting the entire scientific community to go out and use what we’re learning to move the ball forward,” Flemings said.

At this writing date natural gas is pretty cheap. The vast reserves of methane hydrates are still waiting for the low low cost extraction method. For now hydraulic fracking has all the chips. But you can be sure the independent oil and gas companies are already looking into this technology.

A new discovery from the University of Virginia School of Medicine reveals how sugars could be used to make almost indestructible cloth and other materials. Nature figured it out long ago, but the answer has been hidden away in bubbling baths of acid. The secret to making clothing practically indestructible could be the same thing that energizes us to grow out of it: sugar. The natural ‘armor’ made of sugar shocked even scientists with its durability.  The team’s research paper has been published in Nature Microbiology.

In certain acidic hot springs, even volcanic hot springs, live ancient single-celled organisms that can exist in conditions far too extreme for most forms of life. They have tiny appendages called pili that are so tough that they resisted UVA scientists’ numerous efforts to break them apart to learn their secrets.

The natural sugar “armor” that lets a single-celled organism tolerate nearly boiling acid. Image Credit: University of Virginia School of Medicine. Click image for the largest view.

Researcher Edward H. Egelman, PhD, of UVA’s Department of Biochemistry and Molecular Genetics said, “We were unable to take these things apart in boiling detergent. They just remained absolutely intact. So we then tried much harsher treatments, including boiling them in lye, which is sodium hydroxide. Nope.”

The researchers tried several other approaches before throwing up their hands and turning to cryo-electron microscopy, which allows them to image submicroscopic things almost down to individual atoms. What they found was shocking.

Egelman explained, “There’s just a huge amount of sugar covering the entire surface of these filaments in a way that has never been seen before. These bugs have devised a way to just use massive amounts of sugar to cover these filaments and make them resistant to the incredible extremes of the environment in which they live.”

You might liken the sugar coating to a hard sugar shell on a candy apple. The outer sugar shell is much harder than what it surrounds. In this case, though, the sugars were arranged in such a stable fashion that even acid can’t dissolve them.

“These pili, which are protein filaments, normally would be very sensitive to heat, acid and enzymes, but coating it in sugars make it almost indestructible,” Egelman explained. “There’s a lot of evidence showing that adding small numbers of sugars can increase the stability of drugs and other protein structures, but no one, as far as we know, has ever seen this massive amount . . . to the point where something is almost indestructible.”

People can take a lesson from nature’s design to manufacture products that are similarly sturdy, Egelman said. Take a protein such as wool, say, and coat it in a special arrangement of sugars and you could make amazingly durable clothing, carpet or even building materials.

“Proteins are pretty sturdy and resilient, but with this type of covering of sugar, they would be much more stable, even more resilient,” Egelman said. “They could have lots of uses.”

The discovery is but the latest for Egelman, whose many contributions to his field recently earned him election to the National Academy of Sciences.

OK, OK, its not directly an energy and fuel topic. But this guy Egelman is someone to keep an eye out for because he does turn up really interesting things. On point though – everything that lasts longer will reduce the energy load in making new things.

University of Houston (UH) researchers have reported a major step forward in the search for new thermoelectric materials. The discovery offers a new explanation for asymmetrical thermoelectric performance. The promise of thermoelectric materials as a source of clean energy drives the search for materials that can efficiently produce substantial amounts of power from waste heat.

Physicist Zhifeng Ren leads a project to resolve the problem of asymmetrical thermoelectric performance. Image Credit: University of Houston. Click image for the largest view

The researchers reported the major step forward by publishing in Science Advances the discovery of a new explanation for asymmetrical thermoelectric performance. The phenomenon occurs when a material that is highly efficient in a form which carries a positive charge is far less efficient in the form which carries a negative charge, or vice versa.

Zhifeng Ren, M. D. Anderson Chair Professor of Physics at the University of Houston, director of the Texas Center for Superconductivity at UH and corresponding author on the paper, said they have developed a model to explain the previously unaddressed disparity in performance between the two types of formulations. They then applied the model to predict promising new materials to generate power using waste heat from power plants and other sources.

The researchers already knew thermoelectric efficiency depends on the performance of the material in both forms, known as “p-type” and “n-type” for carrying a positive and negative charge, respectively. But most materials either don’t exist in both formulations or one type is more efficient than the other.

It is possible to build effective thermoelectric devices using just a p-type or n-type compound, but it is easier to design a device that contains both types. Ren explained the best performance would come when both types exhibit similar properties.

The researchers synthesized one of the predicted materials, a zirconium-cobalt-bismuth compound, and reported a measured heat-to-electricity conversion efficiency of 10.6% at both the cold side, about 303 Kelvin, or about 86° Fahrenheit, and the hot side, about 983 Kelvin (1,310° Fahrenheit) for both the p-type and the n-type.

Jun Mao, a post-doctoral researcher at UH and a first author of the report, said they determined the asymmetrical performance of some materials is linked to the fact that the charge moves at different rates in the two types of formulation. “If the charge movement of both the positive charge, for p-type, and the negative charge, for n-type, is similar, the thermoelectric performance of both types is similar,” he said.

Knowing that, they were able to use the mobility ratio to predict performance of previously unstudied formulations.

“When the thermoelectric performance for one type of a material has been experimentally studied, while the other type has not yet been investigated, it is possible to predict the ZT by using the identified relationship between the asymmetry and weighted mobility ratio,” the researchers wrote. ZT, or the figure of merit, is a metric used to determine how efficiently a thermoelectric material converts heat to electricity.

Hangtian Zhu, a post-doctoral researcher at UH and the report’s other first author, said the next step is determining how to formulate the corresponding type of material, once a material with a high efficiency in either p-type or n-type is found.

That can require experimentation to determine the best dopant where researchers tweak performance by adding a tiny amount of an additional element to the compound, known as “doping” to improve performance, Zhu explained.

That’s where the new understanding of asymmetrical performance comes in. Zhu noted that by predicting which compounds will have high performance in both types, researchers are encouraged to continue looking for the best combination, even if early efforts did not succeed.

The other researchers involved in the project are: Qing Zhu and Zihang Liu, both of UH; Yumei Wang of the Beijing National Laboratory for Condensed Matter Physics; and Zhenzhen Feng, Jifeng Sun and David J. Singh of the University of Missouri.

It does look like this study will accelerate the thermoelectric hunt for optimal materials. So far its been mostly clues and experimentation on hunches with some impressive results. There has been progress, but this work could take the clues hunches and experiments to far improved results much faster.


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