Category: Chemistry

A research team has published their method to create a comprehensive database of polymer properties, as well as experimental validation, in npj Computational Materials.

“Materials informatics (MI), a new branch of materials research that combines materials data with data science, is gaining traction,” said co-corresponding author Yoshihiro Hayashi, assistant professor, Institute of Statistical Mathematics in the Research Organization of Information and Science (ROIS). Hayashi is also affiliated with the University of Tokyo’s Department of Mechanical Engineering. “MI applies machine learning to predict new materials with innovative properties and their fabrication methods from a vast design space. As such, data is the most important resource in MI.”

Despite the need, Hayashi said, efforts to create a comprehensive database of polymer properties to enable data-driven research have fallen short.

“To construct a database of polymer properties by molecular simulations, we developed RadonPy,” Hayashi said. “It’s the first open-source software that successfully automates polymer physical property calculations using simulations of classical molecular dynamics based on atomistic models—which account for the behaviors and characteristics of individual constituents.”

The program takes an assigned polymer and runs calculations to equilibrate it in prescribed system parameters. Once it does, it can then calculate the polymer’s density, radius of gyration, refractive index, thermal conductivity, specific heat capacities at constant pressure and at constant volume, among other information. RadonPy produces and stores the data, which can then be accessed later. The researchers also implemented a machine learning technique called transfer learning to correct biases and variations between the simulated property values and experimental data.

“In this study, more than 1,000 unique amorphous polymers were computed in about two months, mainly using the supercomputer Fugaku,” said co-corresponding author Ryo Yoshida, professor, Institute of Statistical Mathematics in ROIS, the National Institute for Materials Science’s Research and Services Division of Materials Data and Integrated System and The Graduate University of Advance Studies’ Department of Statistical Science.

“The program implements a set of automatic computation functions for 15 different properties, which were systematically compared with experimental data to validate the calculation conditions. We also comprehensively verified the agreement between six properties obtained from high-throughput molecular dynamics calculations and experimental values.”

The research team also identified eight amorphous polymers with high conductivity, according to Yoshida. Now, the group is using RadonPy to create the world’s largest open database of polymer physics, with more than 100,000 different polymer species. In addition to ROIS, three universities and 19 companies are partnering to jointly develop other databases with RadonPy for a variety of applications in academia and industry.

“This project will create a world map of polymer material properties,” Hayashi said. “Such exhaustive observations cannot be achieved solely via experimental approaches requiring considerable costs, such as in material synthesis. This research is the first step toward a new horizon of polymer science.”

More information: Yoshihiro Hayashi et al, RadonPy: automated physical property calculation using all-atom classical molecular dynamics simulations for polymer informatics, npj Computational Materials (2022). DOI: 10.1038/s41524-022-00906-4

Provided by Research Organization of Information and Systems

A team from the Universitat Politècnica de València (UPV), the Universitat de València (UV), and the Centro de Investigación Biomédica en Red sobre Enfermedades Raras (CIBERER) has developed a lateral flow test that identifies and quantifies the level of allergens reliably in food with the help of a smartphone. The work has been published in the journal Biosensors.

“Food allergy or hypersensitivity is estimated to affect about 520 million people worldwide. These reactions occur mainly through the consumption of foods containing trace allergens. Therefore, identifying and quantifying them before the food is consumed is essential, and this is what the test we have developed allows,” says Sergi Morais, professor in the Department of Chemistry at the Universitat Politècnica de València and researcher at the Inter-University Institute of Molecular Recognition and Technological Development (IDM).

The prototype has been developed as a proof of concept for simultaneously detecting almond and peanut allergens and has been validated with everyday commercial foods such as biscuits and energy bars.

Among its advantages, the researchers highlight the reliability of the test, which contains multiple internal controls and calibrators integrated into a miniaturized 36-point array.

“With microarray technology, we perform 36 assays in a single step. The derived information allows us to identify whether the result is a true positive or negative. In addition, with the internal calibrators and the smartphone, we can quantify with high precision traces of allergen in the food,” says Ángel Maquieira, full professor in the Department of Chemistry at the Universitat Politècnica de València.

Regarding the extraction method, the UPV, UV, and CIBERER team stresses its simplicity, which means anyone can carry it out at any time.

“Current extraction methods consist of multiple steps and require sophisticated equipment for grinding, degreasing, extraction, and purification of allergens. Therefore, the analysis is carried out in qualified laboratories. The aim is to decentralize the analysis, as has been done with the COVID-19 test. We want anyone to be able to analyze a food just before consuming it,” adds Sergi Morais.

The extraction method developed is based on the use of a portable grinder, which is used to grind and filter the sample in a single step; 5 mL of a solution is then added to extract the allergen, and, once the sample is prepared, the test strip is immersed in the solution. And in just 5 minutes, the result is obtained, which can be read with a mobile phone.

“At an estimated cost of €1 per strip, the developed test has great commercial potential, for example, in the food sector for rapid identification of allergens in situ and in the pharmaceutical sector to quantify the potency of allergenic extracts used in allergy testing,” says Amadeo Sena, a postdoctoral researcher at the Inter-University Institute for Molecular Recognition and Technological Development (IDM).

Future development

Looking to the future, the UPV, UV, and CIBERER team points out that, given the characteristics of the test strip, it could easily be adapted for other allergens, as the group has specific antibodies for a wide range of allergens and biomarkers.

“Our challenge is to develop a test for the simultaneous quantification of the 14 allergens that must be declared according to Royal Decree 126/2015,” concludes Patricia Casino, a researcher at Instituto Universitario de Biotecnología i Biomedicina (BIOTECMED)—Universitat de València and the CIBERER.

More information: Amadeo Sena-Torralba et al, Lateral Flow Microimmunoassay (LFµIA) for the Reliable Quantification of Allergen Traces in Food Consumables, Biosensors (2022). DOI: 10.3390/bios12110980

Provided by Universitat Politècnica de València

A major impediment to industrial urea synthesis is the lack of catalysts with high selectivity and activity. Prof. Yuliang Li (Institute of Chemistry, Chinese Academy of Sciences) and coworkers reported a new catalyst system suitable for the highly selective synthesis of industrial urea by in-situ growth of graphdiyne on the surface of cobalt-nickel mixed oxides.

The researchers found that such a catalyst is a multi-heterojunction interfacial structure resulting in the obvious incomplete charge transfer phenomenon between graphdiyne and metal oxide interface and multiple intermolecular interactions. These intrinsic characteristics are the origin of the high performance of the catalyst.

The team also demonstrated that the catalyst could effectively optimize the adsorption/desorption capacities of the intermediate and promote the direct C-N coupling by significantly suppressing by-product reactions toward the formation of H₂, CO, N₂, NH₃.

The catalyst can selectively synthesize urea directly from nitrite and carbon dioxide in water at room temperature and pressure and exhibits record-high Faradaic Efficiency (FE) of 64.3%, nitrogen selectivity (N_urea-selectivity) of 86.0%, carbon selectivity (C_urea-selectivity) of ~100%, as well as the urea yield rates of 913.2 μg h^–1 mg_cat^–1 and remarkable long-term stability.

The work is published in the journal National Science Review.

More information: Danyan Zhang et al, Multi-heterointerfaces for selective and efficient urea production, National Science Review (2022). DOI: 10.1093/nsr/nwac209

Provided by Science China Press 

Around 500 million years ago, early vertebrates in the seas became fish, adopting an inner skeleton and a flexible spine based on a nanocomposite of fibers and mineral, known as bone material. This “invention” of evolution was so successful that the basic structure was also adopted for later vertebrates that lived on land.

However, while the bones of all terrestrial vertebrates are basically equipped with bone cells (osteocytes), certain fish species continued to evolve and finally managed to create a more energy efficient material: bone lacking bone cells, found today for example in fish such as salmon, medaka or tilapia.

Samples with and without bone cells

“We asked ourselves how bone samples with and without bone cells actually differ in their microstructures and properties,” says Prof. Paul Zaslansky, who heads a research group at Charité Berlin and specializes in mineralized biomaterials including teeth and bones.

Together with Ph.D. student Andreia Silvera and international partners, they have now compared bone samples from zebrafish and medaka. Both fish species are of similar size and live in similar conditions, so their skeletons must withstand similar stresses. However, while zebrafish have bone cells, the skeleton of medaka do not.

“The background to the question is that the function of bone cells in bone and how they change with age is of great interest to the aging population,” Silvera explains. Bone cells can respond to physical stress by sending biochemical signals that lead to the formation or resorption of bone tissue, adapting to load. But with age or in diseases such as osteoporosis, this mechanism no longer seems to work.

“With our basic research, we want to find out how bones with and without bone cells differ and cope with the challenges of external stress,” Zaslansky says.

Strength and elasticity

Bones have a complex structure: they comprise nanofibers of collagen and nanoparticles of mineral but also other minor ingredients. Certain protein compounds, so called Proteoglycans (PGs), are embedded in a tissue of collagen fibers and nanocrystals and play important roles in tissue formation and maintenance.

“PGs may be compared to salt in the soup. Too little or too much of it is not good,” Zaslansky says. The PGs can retain water, and there are plenty of PGs in healthy cartilage, making it as elastic as a sponge. Together, these components form an extracellular matrix (ECM), a 3D structure that provides strength and elasticity, ensuring function for many years.

In bones, an open network (Lacunar Channel Network or LCN) of channels and pores with diameters ranging from a few hundred nanometers to micrometers is created in this 3D structure. This LCN hosts the bone osteocytes, cells that sense load and orchestrate bone remodeling. In the LCN and within the nanocomposite, bone contains up to 20% of its volume in water, with many functions including toughening and adaptation to mechanical stress.

Neutron tomography at BER II

To determine the amount of incorporated water, the researchers first immersed bone samples in water and transilluminated them with neutrons, provided by the Berlin experimental reactor BER II at HZB—followed by saturation in deuterated heavy water (D₂O). 3D data was collected again and the difference between the two bone states allowed the team to determine for each spine vertebrae the precise amount of water displaced by diffusion of the D₂O.

“In addition, we examined sections of the bone samples, analyzed them by electron microscopy and micro CT and we also determined the PG concentration with Raman spectroscopy,” Silvera explains.

Surprising results: PGs make the difference

Until now, it was assumed that both bone types contain similar amounts of water and had very similar composition and properties. In fact however, the neutron examination showed that the bone material of zebrafish releases half as much water as that of medaka. This is all the more surprising because these bones have a very similar microstructure of mineralized collagen fibers, but zebrafish also contain large cell spaces within the LCN.

“My first reaction was, ‘This must be wrong!’ So we checked everything thoroughly and realized it’s really revolutionary,” recalls Zaslansky. The only explanation for the difference is that the bone matrices of the two species differ in a fundamental compositional component that affects water permeability. And here, both histological studies and Raman spectroscopy show: it’s the small but important contribution of PGs. The medaka samples contain far less PG than the zebrafish samples.

“This is a new finding: although both fish cope with similar stresses, their bone materials do not have the same water permeability properties,” says Silveira.

The study is published in the journal Materials & Design.

“We hope these results will help us better understand bone diseases as well,” Zaslansky says. Why are some bones better at responding to stress than others? What happens when bones age? Could it be that they lose PGs, and become less watertight? Perhaps aging or pathology such as osteoporosis changes the bone that surrounds bone cells, which makes it difficult to remodel and form bone tissue that works correctly?

More information: Andreia Silveira et al, Water flow through bone: Neutron tomography reveals differences in water permeability between osteocytic and anosteocytic bone material, Materials & Design (2022). DOI: 10.1016/j.matdes.2022.111275

Provided by Helmholtz Association of German Research Centres 

Chemical reactions occur on the scale of atomic vibrations—one million times smaller than the thickness of a human hair. These tiny movements are difficult to control.

Established methods include the control of temperature or providing surfaces and complexes in solution made from rare materials. They tackle the problem on a larger scale and cannot target specific parts of the molecule. Ideally, researchers would like to provide only a small amount of energy to some atoms at the right time, just like a billiard player wants to nudge just one ball on the table.

In recent years, it became clear that molecules undergo fundamental changes when they are placed in optical cavities with opposing mirrors. Inside those confines, the system is forced to interact with virtual light, or photons. Crucially, this interaction changes the rate of chemical reactions—an effect that was observed in experiments but whose underlying mechanism remained a mystery.

Now a team of theoretical physicists from Germany, Sweden, Italy and the U.S.A. has come up with a possible explanation, which qualitatively agrees with the experimental results.

The team involved researchers from the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) in Hamburg, Germany, Chalmers University of Technology in Sweden, the Center for Computational Quantum Physics at the Flatiron Institute, Harvard University (both in the U.S.A.), and the Istituto per i Processi Chimico Fisici at the CNR (National Research Council) in Italy.

Using an advanced theoretical method, called Quantum-Electrodynamical Density-Functional Theory (QEDFT), the authors have unveiled the microscopic mechanism which reduces the chemical reaction rate, for the specific case of the deprotection reaction of 1-phenyl-2-trimethylsilylacetylene. Their findings are in agreement with the observations by the group of Thomas Ebbesen in Strasbourg.

The team discovered that the conditions inside the optical cavity affect the energy which makes the atoms vibrate around the molecule’s single bonds, which are critical for the chemical reaction.

Outside the cavity, that energy is usually deposited in a single bond during the reaction, which can ultimately break the bond—a key step in a chemical reaction. “However, we find that the cavity introduces a new pathway, so that the energy is less likely to be funneled only into a single bond,” says lead author Christian Schäfer. “This is the key process which inhibits the chemical reaction, because the probability to break a specific bond is diminished.”

Manipulating materials through the use of cavities (“polaritonic chemistry”) is a powerful tool with many potential applications, according to the paper’s author Enrico Ronca, who works at CNR: “For instance, it was observed that coupling to specific vibrational excitations can inhibit, steer, and even catalyze a chemical process at room temperature. Our theoretical work enhances the understanding of the underlying microscopic mechanisms for the specific case of a reaction inhibited by the field.”

While the authors point out that important aspects remain to be understood and further experimental validation is required, they also highlight the special role of this new direction.

“This works puts the controversial field of polaritonic chemistry onto a different level,” adds Angel Rubio, the Director of the MPSD’s Theory Department. “It provides fundamental insights into the microscopic mechanisms that enable the control of chemical reactions. We expect the present findings to be applicable to a larger set of relevant reactions (including click chemical reactions linked to this year’s Nobel Prize in chemistry) under strong light-matter coupling conditions.”

The paper is published in the journal Nature Communications.

More information: Christian Schäfer et al, Shining light on the microscopic resonant mechanism responsible for cavity-mediated chemical reactivity, Nature Communications (2022). DOI: 10.1038/s41467-022-35363-6

Journal information: Nature Communications 

Provided by Max Planck Society 

When it comes to kitchen spills, paper towels and rags do the job. But using a hydrogel—a gelatin-like material in the form of a dry sheet—researchers have crafted a better picker-upper that absorbs and holds about three times more water-based liquid. The method, presented on December 21 in the journal Matter, produces an absorbent, foldable, and cuttable “gel sheet” that may one day find use in our kitchens or operating rooms to soak up liquids.

There are generally two types of materials that absorb liquids—porous materials and hydrogels. Porous materials like cloth and paper are flexible, foldable, and easy to use, but not very absorbent. On the other hand, superabsorbent hydrogels that are made of polymer, a web of large molecules, can soak up more than 100 times their weight in water. However, when dried, these hydrogels become brittle solids that crumble.

“We reimagined what a hydrogel can look like,” says corresponding author Srinivasa Raghavan of the University of Maryland. “What we’ve done is combine the desired properties of a paper towel and a hydrogel.”

To craft the gel sheets, the research team first mixed in acid, base, and other ingredients for the hydrogel in a zip-top bag. Like vinegar meeting baking soda, the mixture released carbon dioxide bubbles within the gel, creating a porous and foam-like material. Next, the zip-top bag was sandwiched between glass slabs to form a sheet and then exposed to UV light, which sets the liquid around the bubbles, leaving pores behind. Lastly, the team dipped the set sheet in alcohol and glycerol and air-dried it. This enabled the dried gel sheet to remain soft and flexible, similar to a fabric’s texture.

“To our knowledge, this is the first hydrogel that has been reported to have such tactile and mechanical properties,” says Raghavan. The gel sheets also stayed soft and flexible in ambient conditions for a year, indicating stability. “We are trying to achieve some unique properties with simple starting materials.”

Compared to a commercial cloth pad and a paper towel, a gel sheet the same size can absorb more than three times the amount of liquid than others. When researchers placed the gel sheet over 25 mL (0.8 oz) of spilled water, the sheet swelled and soaked it up within 20 seconds, holding the water without dripping. However, the cloth pad only absorbed about 60% of the water, leaving drips behind.

The gel sheet also performed well with thick liquids, such as syrup, blood, and even fluids that are a million times thicker than water. The researchers found that the gel sheet could absorb nearly 40 mL (1.4 oz) of blood within 60 seconds, while gauze dressing soaked up only 55% of the blood. The gel sheet also holds its liquid well, whereas the blood-soaked gauze trickles. Compared to sanitary pads, sponges, and gauze, the gel sheet absorbed over two times more blood than the others.

“To our knowledge, this is the first hydrogel that has been reported to have such tactile and mechanical properties,” says Raghavan. The gel sheets also stayed soft and flexible in ambient conditions for a year, indicating stability. “We are trying to achieve some unique properties with simple starting materials.”

Compared to a commercial cloth pad and a paper towel, a gel sheet the same size can absorb more than three times the amount of liquid than others. When researchers placed the gel sheet over 25 mL (0.8 oz) of spilled water, the sheet swelled and soaked it up within 20 seconds, holding the water without dripping. However, the cloth pad only absorbed about 60% of the water, leaving drips behind.

The gel sheet also performed well with thick liquids, such as syrup, blood, and even fluids that are a million times thicker than water. The researchers found that the gel sheet could absorb nearly 40 mL (1.4 oz) of blood within 60 seconds, while gauze dressing soaked up only 55% of the blood. The gel sheet also holds its liquid well, whereas the blood-soaked gauze trickles. Compared to sanitary pads, sponges, and gauze, the gel sheet absorbed over two times more blood than the others.

Next, the team plans to optimize their gel sheets by increasing absorbency, strengthening the material, lowering the cost, and making the sheets reusable. The researchers are also looking to develop gel sheets for absorbing oil.

“In principle, the gel sheets could be a superior form of paper towels,” says Raghavan. He envisions the gel sheets picking up spills in kitchens and laboratories, as well as cleaning up blood from surgeries and menstrual bleeding. Because of their flexible and absorbent nature, gel sheets also have the potential to stop bleeding from severe wounds as dressing. “I’m always interested in taking our inventions further than just publishing a paper. It would be wonderful to take it to actual practical use.”

More information: Srinivasa R. Raghavan, A Better Picker-Upper: Superabsorbent Gel Sheets with Fabric-Like Flexibility, Matter (2022). DOI: 10.1016/j.matt.2022.11.021. www.cell.com/matter/fulltext/S2590-2385(22)00652-X

Journal information: Matter 

Provided by Cell Press 

In nature, enzymes termed hydrogenases are capable of producing molecular hydrogen (H₂). Special types of these biocatalysts, so-called [FeFe]-hydrogenases, are extremely efficient and therefore of interest for biobased hydrogen production. Although scientists have learned a lot about how these enzymes work, many details remain to be completely understood.

A research team of the Photobiotechnology group at Ruhr University Bochum, Germany, headed by Dr. Jifu Duan and Professor Thomas Happe succeeded in filling a scientific gap. The researchers showed that external cyanide binds to the [FeFe] hydrogenases and inhibits hydrogen formation. In the process, they detected a structural change in the proton transport pathway, which helps to understand the coupling of electron and proton transport. They reported their findings in the journal Angewandte Chemie of December 4, 2022.

A sophisticated internal catalyst

To generate H₂, these biocatalysts transfer electrons to protons, employing a sophisticated structure as internal catalyst. This so-called H-cluster contains electronically active iron ions that are bound to what most people know as toxins: carbon monoxide and cyanide.

However, although internal carbon monoxide and cyanide are crucial for the high activity of hydrogenases, additional external carbon monoxide binds to the H-cluster and prevents its H₂ production. “Interestingly, cyanide is also a well-known inhibitor of iron-containing biocatalysts,” says Jifu Duan. “And yet, its effect on [FeFe]-hydrogenases has hardly been analyzed before.”

The Bochum-based research team closed this scientific gap. The researchers showed that external cyanide binds to and inhibits [FeFe]-hydrogenases. In collaboration with Professor Eckhard Hofmann, head of the protein crystallography group at RUB, the team obtained the structure of H₂-producing biocatalysts to which external cyanide was bound.

“The high-resolution structure in combination with spectroscopic analyses tells us that the external cyanide directly binds to the H-cluster, similar to other inhibitors studied so far,” says Jifu Duan. “This explains why the hydrogenase is inactive after cyanide treatment.”

Coincidental capture of a transient state

When the researchers took a detailed look into the structure of the cyanide-poisoned hydrogenase, they found a surprise. They observed structural changes in the proton transport pathway that is required to guide the protons that will become H₂ to the H-cluster.

“This conformation has been suggested to be vital for efficient proton shuttling, but it had never been observed structurally. Coincidently, the cyanide binding helped us to capture such a transient state,” says Jifu Duan.

“These findings are important for researchers to understand the coupling of electron and proton transport which is not only relevant for H₂-generating enzymes, but many additional biocatalysts,” concludes Thomas Happe.

More information: Jifu Duan et al, Cyanide Binding to [FeFe]‐Hydrogenase Stabilizes the Alternative Configuration of the Proton Transfer Pathway, Angewandte Chemie International Edition (2022). DOI: 10.1002/anie.202216903

Journal information: Angewandte Chemie International Edition  , Angewandte Chemie 

Provided by Ruhr-Universitaet-Bochum 

Lipstick can be a confidence booster, enhance a costume and keep lips from chapping. But sharing a tube with a friend or family member can also spread infections. To develop a version with antimicrobial properties, researchers reporting in ACS Applied Materials & Interfaces have added cranberry extract to the formulation. Their deep red cream quickly inactivates disease-causing viruses, bacteria and a fungus that come in contact with it.

According to historians, people in ancient Egypt were the first to use make-up, applying pastes made from minerals and other substances in their environment. The formulations have evolved over the centuries, but now researchers have come full circle, looking again toward natural ingredients.

For example, recent studies have reported that lipstick formulas incorporating natural colorants, such as red dragon fruit, can result in products with both vibrant colors and antimicrobial activity. And previously, cranberry extract has been shown to inactivate viruses, bacteria and fungi. So, Ángel Serrano-Aroca and colleagues wanted to use cranberry extract to create a deep red lip tint with antimicrobial properties.

The research team mixed cranberry extract into a lipstick cream base, which contained shea butter, vitamin E, provitamin B5, babassu oil and avocado oil. In experiments, the reddened cream was added to cultures containing different viruses, bacteria and one fungal species. Both enveloped and non-enveloped virus types were completely inactivated within a minute of contact with the cranberry-containing cream.

And the multidrug-resistant bacteria, mycobacteria and fungus were substantially inactivated within five hours of applying the cream. The researchers suggest that their novel lipstick formula could offer protection against a variety of disease-causing microorganisms.

More information: Alberto Tuñón-Molina et al, Antimicrobial Lipstick: Bio-Based Composition against Viruses, Bacteria, and Fungi, ACS Applied Materials & Interfaces (2022). DOI: 10.1021/acsami.2c19460

Journal information: ACS Applied Materials and Interfaces 

Provided by American Chemical Society 

Researchers from the University of Toronto’s Faculty of Applied Science & Engineering and Fujitsu have developed a new way of searching through ‘chemical space’ for materials with desirable properties.

The technique has resulted in a promising new catalyst material that could help lower the cost of producing clean hydrogen.

The discovery represents an important step toward more sustainable ways of storing energy, including from renewable but intermittent sources, such as solar and wind power.

“Scaling up the production of what we call green hydrogen is a priority for researchers around the world because it offers a carbon-free way to store electricity from any source,” says Ted Sargent, a professor in the Edward S. Rogers Sr. department of electrical and computer engineering and senior author on a new paper published in Matter.

“This work provides proof-of-concept for a new approach to overcoming one of the key remaining challenges, which is the lack of highly active catalyst materials to speed up the critical reactions.”

Today, nearly all commercial hydrogen is produced from natural gas. The process produces carbon dioxide as a byproduct: if the CO₂ is vented to the atmosphere, the product is known as ‘grey hydrogen,’ but if the CO₂ is captured and stored, it is called ‘blue hydrogen.’

By contrast, ‘green hydrogen’ is a carbon-free method that uses a device known as an electrolyzer to split water into hydrogen and oxygen gas. The hydrogen can later be burned or reacted in a fuel cell to regenerate the electricity. However, the low efficiency of available electrolyzers means that most of the energy in the water-splitting step is wasted as heat, rather than being captured in the hydrogen.

Researchers around the world are racing to find better catalyst materials that can improve this efficiency. But because each potential catalyst material can be made of several different chemical elements, combined in a variety of ways, the number of possible permutations quickly becomes overwhelming.

“One way to do it is by human intuition, by researching what materials other groups have made and trying something similar, but that’s pretty slow,” says department of materials science and engineering Ph.D. candidate Jehad Abed, one of two co-lead authors on the new paper.

“Another way is to use a computer model to simulate the chemical properties of all the potential materials we might try, starting from first principles. But in this case, the calculations get really complex, and the computational power needed to run the model becomes enormous.”

To find a way through, the team turned to the emerging field of quantum-inspired computing. They made use of the Digital Annealer, a tool that was created as the result of a long-standing collaboration between U of T Engineering and Fujitsu Research. This collaboration has also resulted in the creation of the Fujitsu Co-Creation Research Laboratory at the University of Toronto.

“The Digital Annealer is a hybrid of unique hardware and software designed to be highly efficient at solving combinatorial optimization problems,” says Hidetoshi Matsumura, senior researcher at Fujitsu Consulting (Canada) Inc.

“These problems include finding the most efficient route between multiple locations across a transportation network, or selecting a set of stocks to make up a balanced portfolio. Searching through different combinations of chemical elements to a find a catalyst with desired properties is another example, and it was a perfect challenge for our Digital Annealer to address.”

In the paper, the researchers used a technique called cluster expansion to analyze a truly enormous number of potential catalyst material designs—they estimate the total as a number on the order of hundreds of quadrillions. For perspective, one quadrillion is approximately the number of seconds that would pass by in 32 million years.

The results pointed toward a promising family of materials composed of ruthenium, chromium, manganese, antimony and oxygen, which had not been previously explored by other research groups.

The team synthesized several of these compounds and found that the best of them demonstrated a mass activity— a measure of the number of reactions that can be catalyzed per mass of the catalyst—that was approximately eight times higher than some of the best catalysts currently available.

The new catalyst has other advantages too: it operates well in acidic conditions, which is a requirement of state-of-the-art electrolyzer designs. Currently, these electrolyzers depend on catalysts made largely of iridium, which is a rare element that is costly to obtain. In comparison, ruthenium, the main component of the new catalyst, is more abundant and has a lower market price.

There is more work ahead for the team: for example, they aim to further optimize the stability of the new catalyst before it can be tested in an electrolyzer. Still, the latest work serves as a demonstration of the effectiveness of the new approach to searching chemical space.

“I think what’s exciting about this project is that it shows how you can solve really complex and important problems by combining expertise from different fields,” says electrical and computer engineering Ph.D. candidate Hitarth Choubisa, the other co-lead author of the paper.

“For a long time, materials scientists have been looking for these more efficient catalysts, and computational scientists have been designing more efficient algorithms, but the two efforts have been disconnected. When we brought them together, we were able to find a promising solution very quickly. I think there are a lot more useful discoveries to be made this way.”

More information: Hitarth Choubisa et al, Accelerated chemical space search using a quantum-inspired cluster expansion approach, Matter (2022). DOI: 10.1016/j.matt.2022.11.031

Journal information: Matter 

Provided by University of Toronto