Researchers observed T-shaped clusters that drive lanthanide separation during liquid-liquid extraction. Credit: Alex Ivanov/ORNL, U.S. Dept. of Energy
Researchers at Oak Ridge National Laboratory have zoomed in on molecules designed to recover critical materials via liquid-liquid extraction, or LLE—a method used by industry to separate chemically similar elements.
Lanthanides are rare-earth metals critical to energy and national security technologies for magnets, electronics and catalysts. They occur together naturally in mineral ore deposits, but their chemical similarities make separating individual elements difficult. LLE methods leverage self-separating liquids such as oil and water to isolate a target material. One example is dividing light and heavy lanthanides. The new study describes how the process unfolds, finding that an unexpected T-shaped cluster forms around target metals, acting like a magnet to create larger aggregates.
“These atomic-scale details are difficult to observe and could help us improve future rare-earth separation strategies,” said ORNL’s Alex Ivanov.
The research is published in The Journal of Physical Chemistry Letters.
More information: Darren M. Driscoll et al, Noncoordinating Secondary Sphere Ion Modulates Supramolecular Clustering of Lanthanides, The Journal of Physical Chemistry Letters (2022). DOI: 10.1021/acs.jpclett.2c03423
Effect of monovalent and divalent Cu–PS complexes on the swarming motility of P. aeruginosa PA14. Top row: Motility of P. aeruginosa PA14 in the presence of Cu–PS complexes. Bottom row: Controls. The bacteria were inoculated into the center of each plate consisting of M9 solidified with 0.5% (w/v) Difco agar and containing 0.1% of the relevant Cu–PS complex. Surface coverage was assessed after 24 h of growth at 37 °C. All of the Cu–PS complexes contained 0.7% polysaccharide (w/v) and 500 ppm copper. For the control treatments, the copper concentration in the copper-containing plates was 500 ppm, and the PS plate contained 0.7% Porphyridium sp. polysaccharide (w/v). Credit: Marine Drugs (2022). DOI: 10.3390/md20120787
Antibiotic resistant bacteria are becoming more and more of a concern as traditional sources of anti-microbial treatments become less effective. Therefore, researchers at Ben-Gurion University of the Negev are looking farther afield for promising compounds to treat wounds and infections.
Prof. Shoshana (Mails) Arad and Prof. Ariel Kushmaro, Prof. Levi A. Gheber and Ph.D. student Nofar Yehuda joined a metal and a polysaccharide together and discovered the new compound worked well against bacteria and fungus (Candida albicans) because of the longer and denser spikes on its surface that poked holes in the membrane and killed off the bacteria and the fungus.
“A polysaccharide is a carbohydrate with linked sugar molecules and by adding a metal (Cu), we were able to create an effective new material,” according to the researchers.
Their findings were published recently in Marine Drugs as the new compound is derived from marine red microalga Porphyridium sp.
Commercialization of these new compounds could come sooner rather than later.
“In light of the increased resistance to antibiotic and antifungal agents, there is a growing need for the development of new and improved treatments. BGN Technologies holds a patent application ready for licensing in the field,” say BGN’s Galit Mazooz-Perlmuter and Anat Shperberg Avni. BGN Technologies is Ben-Gurion University’s technology transfer company.
More information: Nofar Yehuda et al, Complexes of Cu–Polysaccharide of a Marine Red Microalga Produce Spikes with Antimicrobial Activity, Marine Drugs (2022). DOI: 10.3390/md20120787
Researchers captured atomic-level insights on the rare-earth mineral monazite to inform future design of flotation collector molecules, illustrated above, that can aid in the recovery of critical materials. Credit: Chad Malone/ORNL, U.S. Dept. of Energy
Critical Materials Institute researchers at Oak Ridge National Laboratory and Arizona State University have studied the mineral monazite, an important source of rare-earth elements, to enhance methods of recovering critical materials for energy, defense and manufacturing applications.
Rare-earth elements occur together naturally in mineral ores such as monazite but are economically challenging to recover. New approaches to separate the valuable ore from unwanted materials are needed.
The research team combined theory and experiment to gain atom-level insights on monazite, providing a first look at surface features important to the design of flotation collector molecules—materials that work like life jackets to buoy up monazite particles on air bubbles from mixed mineral slurries.
“Our efforts address materials needed for froth flotation techniques used to separate high-grade ore from low-value materials during processing. Fundamental research can help us tailor future collectors to make monazite recovery more efficient and cost-effective,” said ORNL’s Vyacheslav Bryantsev.
The work is published in The Journal of Physical Chemistry C.
More information: Luke D. Gibson et al, Characterization of Lanthanum Monazite Surface Chemistry and Crystal Morphology through Density Functional Theory and Experimental Approaches, The Journal of Physical Chemistry C (2022). DOI: 10.1021/acs.jpcc.2c06308
Where does all of this copper come from? How was it produced, distributed, controlled, and sold on an ever-increasing scale? These are some of the questions addressed in a recenty published book, Born with a Copper Spoon: A Global History of Copper.
The book is a global study of a metal that has transformed the globe. Contributors to the book cover North America, Latin America, Europe, Central Africa, the Middle East, East Asia and Oceania and stretch from the early nineteenth to the early twenty-first centuries.
Why are these important questions? Because of the ubiquity of copper and the fact that the world’s collective rehab from fossil fuels may cause a renewed addiction to a new mineral-based economy. Electrification, the pillar of the green transition, requires huge amounts of copper. Projections expect a doubling of copper consumption by 2035 in order to reach zero-emission energy goals. Faced with the enormous task of electrification, the share of the global energy sector will increase to 40 % of total copper consumption in the next two decades
They are also important questions because countries that have an abundance of copper have failed to benefit from it. Zambia is a case in point. It produces 6% of the world’s copper but is still one of the poorest countries in the world.
Born with a Copper Spoon requires us to think differently about our material lives and energies we use, by looking at the places where our minerals are actually produced and the way in which the production and distribution of these minerals are organized.
Will the next world of copper finally evolve as the long-anticipated resource blessing, or is a new global scramble, in which states and companies seek to secure access to the precious metal, going to determine otherwise? Copper became associated with the idea of a resource curse for many people. Zambia’s first President Kenneth Kaunda once remarkedthat his country is “paying the price for having been born with a copper spoon in our mouths.”
He knew too well that the abundance of copper had caused Zambia a host of problems.
Worlds of copper
Our book looks at different ‘worlds of copper’ that have arisen over the last century and a half. The term ‘world of copper’ was first coined by British historians Chris Evans and Olivia Saunders to describe a globally integrated production system that connected the smelters of South Wales to copper mines across the globe between 1830 and 1870.
We see this as the first world of copper. This world was then supplanted by a second world of copper centered on the US. This involved the rise and dominance of American mining companies as huge integrated enterprises controlling the production, processing and distribution of the commodity. “From mine to consumer” was the slogan of the notorious American copper mining company Anaconda, active in Montana and Chile. Underpinning the American world of copper was control over the production chain through the use of new business organizations and technologies.
Technological changes in mining and processing that were quite literally ground-breaking allowed for ever-greater quantities of copper to be mined and processed. Open pit extraction was first developed in North America and soon spread to Latin America and Central Africa, with often comprehensively destructive environmental consequences. Many of these pits are still being mined today.
The American world of copper denotes both the power of American companies, as well as the model of controlling copper chains that is eagerly copied by non-American copper companies. This patterns becomes global: it is applied in Japan, the European empires that control the Copperbelt as well as in Latin America.
In the mid-twentieth century, the American world of copper disintegrated during decolonisation in the face of resource nationalism and a shifting geography of production. A wave of nationalizations by new states brought about a postcolonial world of copper, built around state power, economic sovereignty and state-level international co-operation. Developing states saw copper as their ticket to economic development and modernity. The dream of the red metal was however short-lived.
This postcolonial world of copper collapsed in the 1990s after a long slump in the industry. Multinational private companies reasserted themselves over the industry, but the US and European companies never regained their once dominant position.
Each copper world was marked by several defining features: underlying institutions, organizations, labor practices and produced by global connections and interactions. Identifying and understanding consecutive worlds of copper is crucial to how we understand the development of the global copper industry.
Our current energy transition could herald a new copper world. Renewed demand for copper will likely intensify mining activity in DR Congo, Zambia and other parts of the African continent and could place states in a stronger bargaining position.
The need to think differently
Copper’s status as a global industry has waxed and waned. The history of the metal is not a story of steadily increasing and depending global connections as we move towards the present. It is also a history of disconnections and efforts to de-couple regions from the global economy.
Our book is a contribution to global history and the story of copper is necessarily a global one as extracting, refining, buying, shipping and consuming the metal takes place around the world. Global history is about more than connections, however.
Our book is also about periods of deglobalisation and attempts to sever connections, especially in the mid-twentieth century when a bitter contest over ownership of mineral resources briefly threatened a major realignment of the world economy. In 1967, several of the world’s largest copper producers (Congo, Chile, Peru and Zambia) met in Lusaka to establish a copper cartel that would control the industry and turn an abundance of natural resources into national economic growth.
That’s an ambition that still needs to be fulfilled.
On average, we open seven packaged items per day, most of them food items. All of this together makes for a mountain of plastic. But more and more often our tomatoes, apples and cookies are packaged in cardboard. To help speed up the transition of plastic to paper, TU/e chemist Sterre Bakker researched what coatings can be used to make cardboard a more suitable food packaging material.
About 20% of waste consists of packaging, but packaging food is not all bad. Good packaging protects the item during transport, which means less food needs to be thrown out. Packaging also keeps out moisture, bacteria and fungi. This gives our food a longer shelf life, also resulting in less food going to waste. Keeping a bag of mixed vegetables or a pack of beef in the fridge for a week without it going off? Impossible without the packaging.
More alternatives are being used to reduce plastic packaging waste. Over the past few years, paper and cardboard have become more common packaging materials. But transitioning from plastic to paper is not as easy as it seems, TU/e researcher Sterre Bakker explains. “Plastic has a number of highly practical characteristics. You can use it for airtight packaging and it is an excellent barrier for water and grease. It’s strong but also light, which works well for the transport sector. It requires a lot of effort to find a suitable alternative that meets the same requirements and can be used at a large scale.”
Freedom to publish
For her Ph.D., Bakker investigated how cardboard can be used to make food packaging more sustainable. This Friday (Jan. 27, 2023) she will defend her thesis at the department of Chemical Engineering and Chemistry. To bridge the gap between the laboratory and the packaging sector, she collaborated with chemicals company BASF.
When asked if this collaboration caused any confidentiality issues, Bakker shakes her head. “I consciously sought collaboration with industry; I wanted to get a PHD, but in applied research. This allowed me to make a contribution to society. As I wanted to have the freedom to talk and publish about my findings, we used a model coating. It’s not exactly the same as the manufacturer’s, but it’s very similar. So that was a good compromise.”
Water-based coating
For dry food items, such as rice and oatmeal, cardboard packaging works fine. But putting milk or a hamburger in a cardboard box is more complex, Bakker explains. “A suitable coating is crucial. Water and grease have very different ways of getting through a coating. For a good water barrier, the chemical reaction that occurs while the coating is drying up is very important, but for grease you need a coating that’s intact. This explains why the inner lining of a milk carton is so thick: it consists of several layers of hydrophilic and hydrophobic coatings. In addition to the relatively large amount of plastic used, the mixture of coatings makes it hard to recycle. This is what we would like to improve.”
Bakker set out in search of a single coating impermeant to water, oxygen and grease. To this end, she studied an innovative, water-based coating, with the special addition of a water-soluble, synthetic resin to stabilize polymer particles. This resin makes it possible to transform a water-soluble surface into a water-resistant one. “When the coating dries up, it’s not only the water that evaporates but also a base. The resin undergoes a chemical reaction and this means the coating no longer dissolves in water.”
Multifunctional coating
Bakker used a scanning electron microscope and infrared spectroscopy to carry out in-depth research into the different barrier characteristics of the coating, as well as to optimize the production process. This is all very relevant to industry, she emphasizes, as synthesizing the coating is easy to scale and not overly complex. What’s more, at a certain temperature the color of the coating can be changed by adding a specific molecule. This quasi-alternative expiration date makes the coating multifunctional.
Bakker shows her final result: a shiny piece of thick carton that actually resists both water and grease. “This coating already has a lot of advantages in comparison to current coatings. Although it does require raw fossil materials, the layer can be made much thinner now. We’ve also demonstrated through several experiments that the coating can be peeled off the cardboard more easily, which means it’s very suitable for recycling. We’ve taken the first steps, obviously in the hope of eventually creating a biobased coating that eliminates all plastic from food packaging.”
Tea lover
The above should serve as a reminder, Bakker reiterates, of cardboard being much stronger than we give it credit for. Like women, she says with a smile. Bakker is quite comfortable in the space she created for herself in the male-dominated coating and packaging industry. And as a tea lover she will obviously bring her tea box—cardboard of course—to her new place of work, Allnex in Bergen op Zoom. Before we leave she’s keen to show us the quote adorning her thesis: “A woman is like a teabag; you never know how strong it is until it is in hot water.”
Sterre Bakker defends her thesis at the department of Chemical Engineering and Chemistry on January 27, 2023.
The dairy industry strives to preserve the quality and safety of milk products while maintaining the freshest possible taste for consumers. To date, the industry has largely focused on packaging milk in light-blocking containers to preserve freshness, but little has been understood about how the packaging itself influences milk flavor. However, a new study in the Journal of Dairy Science confirms that packaging affects taste—and paperboard cartons do not preserve milk freshness as well as glass and plastic containers.
Lead investigator MaryAnne Drake, Ph.D., of the North Carolina State University Department of Food, Bioprocessing and Nutrition Sciences, Raleigh, NC, U.S., explained that “milk is more susceptible to packaging-related off-flavors than many other beverages because of its mild, delicate taste.” Besides light oxidation, “milk’s taste can be impacted by the exchange of the packaging’s compounds into the milk and by the packaging absorbing food flavors and aromas from the surrounding refrigeration environment.”
To quantify the flavor impacts of packaging, the researchers examined pasteurized whole and skim milk stored in six half pint containers: paperboard cartons, three plastic jugs (made from different plastics), a plastic bag, and glass as a control. The milk was stored in total darkness to control for light oxidation and kept cold at 4°C (39°F).
The samples were tested on the day of first processing, then again at 5, 10, and 15 days after. A trained panel examined the sensory properties of each sample, and the research team conducted a volatile compound analysis to understand how the packaging was intermingling with the milk. Finally, the samples underwent a blind consumer taste test on day 10 to see whether tasters could tell any difference between milk stored in the paperboard carton or the plastic jug compared with milk packaged in glass.
The results showed that package type does influence milk flavor, and skim milk is more susceptible to flavor impacts than whole milk. Of the different packaging types, paperboard cartons and the plastic bag preserved milk freshness the least due to the paperboard’s absorption of milk flavor and the transfer of paperboard flavor into the milk. Milk packaged in paperboard cartons, in fact, showed distinct off-flavors as well as the presence of compounds from the paperboard. The final results show that while glass remains an ideal container for preserving milk flavor, plastic containers provide additional benefits while also maintaining freshness in the absence of light exposure.
Paperboard cartons are the most widely used packaging type for school meal programs in the United States, so these findings are especially relevant for the consideration of how young children consume and enjoy milk.
“These findings suggest that industry and policymakers might want to consider seeking new package alternatives for milk served during school meals,” said Drake. Over time, the consequences of using milk packaging that contributes significant off-flavors may affect how young children perceive milk in both childhood and adulthood.
More information: D.C. Cadwallader et al, The role of packaging on the flavor of fluid milk, Journal of Dairy Science (2022). DOI: 10.3168/jds.2022-22060
Credit: Skolkovo Institute of Science and Technology
Researchers from Skoltech and Tomsk Polytechnic University have tuned the synthesis of a five-element carbide—a strong, hard-melting compound of carbon and five transition metals—which holds much promise for industrial ceramics and catalysis.
The team relied on fundamental theoretical principles, simulations, and machine learning to identify conditions for the synthesis of single-phase carbide, in which all metal atoms are evenly distributed throughout the crystal. The predictions were confirmed by an experiment using the advanced energy-efficient vacuumless electric arc synthesis method. The study is published in npj Computational Materials.
High-entropy carbides (HECs) are multicomponent equimolar single-phase solid solutions of five or more metals from groups four and five of the periodic table with a cubic NaCl-type crystal structure. One of the key factors of HEC stabilization is configurational, or mixing, entropy, which should be higher than 1.5 times the universal gas constant. This means that the compound should contain at least five basic elements.
The most common HEC synthesis method is reactive spark plasma sintering (SPS) of pre-homogenized raw materials based on individual metal carbides, pure metals, or metal oxides. Typically, HECs are synthesized at high temperatures of about 2,200-2,300 degrees Celsius, and SPS is applied at pressures of about 10–60 MPa with a dwell of 10–15 minutes, whereas homogenization of raw materials can take more than one day.
“The vacuumless electric arc synthesis method helps to produce powdered HECs without using complex, expensive and energy-consuming equipment, such as vacuum pumps for high vacuum or compressors for external pressure. Our set-up is unique in that it does not need pressure or vacuum to produce HECs,” Alexander Pak, the head of the Advanced Energy Materials Laboratory and manager of the Energy of the Future strategic project at TPU, explains.
“Moreover, we can obtain both multi-phase and single-phase carbides by flexibly varying synthesis parameters. HECs are a fairly new class of materials, so we have yet to identify their actual properties and potential uses, which will likely include refractory ceramics and various types of catalysts.”
The team used the Canonical Monte Carlo (CMC) simulation with machine learning interatomic potentials and performed first-principles calculations to determine synthesis temperatures for single- and multiphase carbides. According to the calculations, low-temperature synthesis will produce mostly multiphase HECs with two or more coexisting phases of multicomponent carbides, while synthesis at above 1,500 C will result in single-phase HECs.
“By applying the CMC method, we have succeeded in predicting the HEC’s thermodynamically stable crystal structure at different synthesis temperatures and, as a result, finding the multi-to-single phase transition temperature. Our experiments at temperatures below and above the transition point confirmed the simulation results. Thus, we were able to implement a complete research sequence, going all the way from a computer model to a physical sample,” Skoltech Ph.D. student Vadim Sotskov from the AI for materials science group notes.
More information: Alexander Ya. Pak et al, Machine learning-driven synthesis of TiZrNbHfTaC5 high-entropy carbide, npj Computational Materials (2023). DOI: 10.1038/s41524-022-00955-9
The John Innes Centre research team used genomic tools to map the genome of Chinaberry (Melia azedarach), a mahogany species. Credit: John Innes Centre
New research has uncovered the secret of how plants make limonoids, a family of valuable organic chemicals that include bee-friendly insecticides and have potential as anti-cancer drugs.
The research team, a collaboration between the John Innes Centre and Stanford University, used groundbreaking methods to reveal the biosynthetic pathway of these useful molecules, which are made by certain plant families, including mahogany and citrus.
In the study, which appears in Science, the John Innes Centre research team used genomic tools to map the genome of Chinaberry (Melia azedarach), a mahogany species, and combined this with molecular analysis to reveal the enzymes in the biosynthetic pathway.
“By finding the enzymes required to make limonoids, we have opened the door to an alternate production source of these valuable chemicals,” explained Dr. Hannah Hodgson, co-first author of the paper and a postdoctoral scientist at the John Innes Centre.
Until now, limonoids, a type of triterpene, could only be produced by extraction from plant material.
Dr. Hodgson explained, “Their structures are too complicated to efficiently make by chemical synthesis. With the knowledge of the biosynthetic pathway, it is now possible to use a host organism to produce these compounds.” she added.
Armed with the complete biosynthetic pathway researchers can now produce the chemicals in commonly used host plants such as Nicotiana benthamiana. This method can produce larger quantities of limonoids in a more sustainable way.
Increasing the supply of limonoids could enable the more widespread use of azadirachtin, the anti-insect limonoid obtained from the neem tree and used in commercial and traditional crop protection. Azadirachtin is an effective, fast degrading, bee-friendly option for crop protection but is not widely used due to limited supply.
The team made two relatively simple limonoids, azadirone from Chinaberry, and kihadalactone A from citrus, and believe that the methods used here can now be applied as a template for making more complicated triterpenes.
The team at John Innes used genomic tools to assemble a chromosome level genome for Chinaberry (Melia azedarach), within which they found the genes encoding 10 additional enzymes required to produce the azadirachtin precursor, azadirone. In parallel, the team working at Stanford were able to find the 12 additional enzymes required to make khidalactone A.
Expressing these enzymes in N. benthamiana enabled their characterization, with the help of both Liquid chromatography–mass spectrometry (LC-MS) and Nuclear Magnetic Resonance (NMR) Spectroscopy, technologies that allow molecular level analysis of samples.
Professor Anne Osbourn, group leader at the John Innes Centre and co-corresponding author of the study, said, “Plants make a wide variety of specialized metabolites that can be useful to humans. We are only just starting to understand how plants make complex chemicals like limonoids. Prior to this project, their biosynthesis and the enzymes involved were completely unknown; now the door is open for future research to build on this knowledge, which could benefit people in many ways.”
Another example of a high value limonoid that the team hopes to produce is the anti-cancer drug candidate nimbolide; this work could enable easier access to limonoids like nimbolide to enable further study. As well as producing known products like nimbolide, the research team says the door may open to understanding new activities for limonoids that have not yet been investigated.
Microstructure of the FMHE and two applications based on it.(A) 3D schematic of the composition and optical microscope image showing the surface structure of the FMHE. (B) SEM and EDS images of the cross section of the FMHE3 sample. The distribution of Ni and FM particles; PDMS are represented by their characteristic elements of Ni, In, and Si. The inset shows a close-up SEM image of a spiked Ni particle. (C) An FMHE variable stiffness compensation unit (highlighted in green) mounted on a robot manipulator. (D) Schematic diagram of the FMHE resettable current-liming fuse and its current-time curve during cyclic operation. Credit: Science Advances (2023). DOI: 10.1126/sciadv.adf1141
Smart materials are materials that have the ability to change their properties in response to specific external stimuli, such as temperature, humidity, light, or applied stress. One of the most well-known examples of smart materials is shape memory alloy (SMA), which is a type of metallic material that can change its shape in response to changes in temperature.
Another example of smart materials includes piezoelectric materials, which generate an electric charge in response to applied mechanical stress. Smart materials have a wide range of potential applications, including in aerospace, automotive, robotics, manufacturing, and biomedical engineering.
Variable stiffness materials are a type of smart materials that have the ability to tune their stiffness, or resistance to deformation, in response to external stimuli. This property allows for the material to adapt to changing conditions and improve performance in a wide range of environments.
One of the main advantages of variable stiffness materials is that they can increase the efficiency, safety, and reliability of mechanical systems. For example, variable stiffness materials can be used to create robotic arms and grippers that can adapt to different objects and environments. This allows for the robotic arm or gripper to handle a range of different objects with different shapes, sizes, and weights, which can reduce the complexity and increase the overall efficiency of the robotic system.
Innovative smart materials with tuneable electromechanical properties are revolutionizing the fields of manufacturing, wearable devices, and robotics. However, to date, a material that can intelligently self-tune its electrical and mechanical properties in response to environmental changes, and harness the altered properties synergistically without external control, has yet to be achieved.
To fill this gap, a collaborative research team led by Dr. Shiyang Tang at the University of Birmingham, along with collaborators from the University of Science and Technology of China, the University of Cambridge, and the University of Wollongong, developed a smart material called the Field’s metal hybrid filler elastomer (FMHE). The FMHE comprises hybrid fillers of Field’s metal (a non-toxic low-melting-point alloy) and spiked nickel microparticles embedded in an elastomer matrix.
This research was reported in their recent paper published in Science Advances.
The FMHE created by the researchers can respond to both mechanical strain and electrical currents, exhibiting variable and tuneable electrical conductivity and stiffness without external control. The melting and solidification of the Field’s metal enable the change in stiffness. The FMHE also exhibits unconventional negative piezoresistivity and high strain sensitivity, with resistivity decreasing millions of times upon both compression and stretching.
By harnessing these properties in a synergistic manner, the researchers demonstrated two applications in intelligent and resilient systems, with over an order of magnitude performance improvement compared to the state-of-the-art. The first application is a self-triggered multi-axis compliance compensator that can protect robotic manipulators from excessive compressive, bending, and torsional movements.
The second application is a resettable current-limiting fuse that offers adjustable fusing currents and significantly outperforms commercial products in terms of compactness, range of operating current, and response speed.
“I am thrilled that our experiments and simulations have uncovered the mechanism behind the negative piezoresistive effect and the tuneable conductivity, strain sensitivity, and stiffness of this smart material. I hope this research is the beginning of the further study on this new material family, which has the potential to revolutionize the development of intelligent and resilient robotics and electronics,” said Dr. Guolin Yun, the first author of the study.
“These self-responsive smart materials not only offer cost-saving opportunities but also increase reliability by reducing the need for complex control systems,” said Dr. Shiyang Tang.
This study provides significant value to the fields of manufacturing, robotics, and electronics, potentially leading to the development of electromechanical systems with enhanced performance and functionality.
More information: Guolin Yun et al, Electro-mechano responsive elastomers with self-tunable conductivity and stiffness, Science Advances (2023). DOI: 10.1126/sciadv.adf1141
A study published in ACS Applied Materials & Interfaces describes a novel method of producing hydrogen peroxide (H2O2) without emitting carbon dioxide (CO2), one of the main greenhouse gases and one of the world’s most widely produced chemicals.
Hydrogen peroxide is used to bleach fabric, pulp and paper, and to whiten teeth. It is also used as a thruster fuel for satellite attitude control, and as a disinfectant or sterilizing agent by hospitals. Some 2 million metric tons of the compound are produced annually.
“To understand the impact of our findings, it’s important first and foremost to bear in mind the significance of H2O2 in the chemical industry and the way it’s currently produced,” said Ivo Freitas Teixeira, a professor of chemistry at the Federal University of São Carlos (UFSCar) in São Paulo State, Brazil. He has a Ph.D. in inorganic chemistry from the University of São Paulo (USP) and was a Humboldt Fellow at the Max Planck Institute of Colloids and Interfaces in Potsdam, Germany, between 2019 and 2021.
“All this peroxide is produced by a process that involves anthraquinone [a compound derived from hydrolysis of anthracene, a toxic substance]. In this process, anthraquinone is reduced and then oxidized to make H2O2. The drawbacks of the method are the high cost of anthraquinone and the use of precious metals such as Pd [palladium], and H2 [hydrogen] as reducing agents. This hydrogen is produced by steam-methane reforming, which involves high temperatures and releases CO2, contributing to global warming,” he said.
In the study, the researchers produced peroxide from oxygen (O2) using photocatalysis to guide the process. In photocatalysis, the catalysts (substances that accelerate the chemical reaction) are activated by visible light instead of high temperature or pressure. Another advantage of their method was the use of carbon nitride as a photocatalyst.
This material consists only of carbon and nitrogen, both of which are abundant in Earth’s crust, and can be activated in the visible region, which corresponds to about 45% of the solar spectrum. It is therefore probable that sunlight can be used instead of artificial lighting, making the process more cost-effective.
After testing different reaction conditions, the researchers arrived at a system with an excellent rate of H2O2 production. “We achieved O2 reduction via a photocatalytic route in which the hydrogen source was the water in the reaction medium or the sacrificial reagent, typically glycerol, a byproduct of biodiesel production,” Teixeira explained.
In this system, carbon nitride is used as a semiconductor to separate charges when bathed in light, promoting reduction and oxidation reactions. The O2 is reduced to H2O2 and the sacrificial reagent (glycerol) is oxidized. The H2O2 is obtained without the need to use H2 and hence without CO2 emissions.
“The road we had to travel in our investigation until we arrived at the results described in the published article was a long one because we discovered that at the same time as H2O2 was produced on the surface of the photocatalyst, it could also be degraded,” Teixeira said.
“We had to perform several tests and keep modifying the photocatalyst in order to promote the formation of H2O2 and avoid its decomposition. Understanding the mechanism whereby H2O 2 decomposes on the surface of carbon nitride was extremely important to enable us to develop the ideal photocatalyst for this reaction.”
More information: Andrea Rogolino et al, Modified Poly(Heptazine Imides): Minimizing H2O2 Decomposition to Maximize Oxygen Reduction, ACS Applied Materials & Interfaces (2022). DOI: 10.1021/acsami.2c14872
