High-entropy nanoparticles hold promise for …

High-entropy nanoparticles hold promise for catalytic applications

Alloying is a magic trick used to produce new materials by synergistically mixing at least two metallic elements to form a solid solution. Recent developments in science have found great applications of alloy materials in catalysis, for which nanometer scale bi- or tri-metallic particles are used to accelerate the rate of chemical reactions. But the application of alloys as catalysts is limited by so-called “miscibility,” as not any arbitrary combination of elements can form a homogeneous alloy, neither for robust tuning of the ratio between the two components.

Reported in Nature Communications this week, a research team led by Johns Hopkins University researcher Chao Wang, working with collaborators from the University of Maryland, University of Illinois at Chicago, and University of Pittsburgh, uncovered a new method to break through this limitation. In this work, they mix Co and Mo, two elements that are rarely miscible, but which combination is believed to be important for catalyzing energy-relevant chemical reactions, such as decomposition of ammonia. Instead of directly blending them together, Chao and his team added another three ingredients, Fe, Ni and Cu, all of which are earth-abundant transition metals. When the five elements come together in a particle of nanometer large, a single homogeneous solid solution forms that allows for the incorporation of Co and Mo atoms at various ratios. Scientists call this group of materials “high-entropy alloys.”

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How the catalytic converters in cars go bad …

How the catalytic converters in cars go bad and why it matters

Modern cars rely on catalytic converters to remove carbon monoxide, hydrocarbons and other harmful chemicals from exhaust emissions.

To do so they rely on costly metals that have special chemical properties that diminish in effectiveness over time. Assistant professor Matteo Cargnello and doctoral candidate Emmett Goodman recently led a team that has proposed a new way to reduce the cost and extend the lifespan of these materials, solving a problem that has vexed automotive engineers for years. In the process, Cargnello and colleagues have done something remarkable: made a breakthrough in a mature field where change comes slowly, if at all.

What about catalytic converters needs to be improved?

A new catalytic converter can cost $1,000 or more, making it among the most expensive individual parts on any car. They are costly because they use expensive metals such as palladium to promote the chemical reactions that cleanse the exhaust. Palladium costs about $50 a gram—more than gold—and each catalytic converter contains about 5 grams of it. Metals like palladium are catalysts—a special class of materials that speed up chemical reactions but don’t chemically change themselves. In theory, catalysts can be used over and over, indefinitely. In practice, however, the performance of catalysts degrades over time. To compensate, we are forced to use more of these expensive metals up front, adding to the cost. Our goal is to better understand the causes of this degradation and how to counteract it.

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High temperature thermal shocks increase sta…

High temperature thermal shocks increase stability of single-atom catalysts

Catalysts are essentially boosters that increase the rate of a chemical reaction, and are widely used in the fields of petroleum refining, coal and natural gas conversion, and ammonia production, to name a few. Catalysts also drive emerging battery and fuel cell technology, which is usually (thermally or electrically) energy-intensive, thus requiring catalysis to reduce the reaction temperature, pressure, or electrochemical over-potentials.

Single atom catalysts maximize the metal utilization efficiency of each atom and provide superior performance, representing the frontier of catalysis. Single atoms, however, are typically unstable when synthesized at low temperature (e.g., less than 1000K), and tend to re-aggregate into nanoparticles as a means of minimizing surface energy. To that end, a research team in the University of Maryland (UMD) Department of Materials Science and Engineering (MSE) developed a high temperature shockwave catalysis method—reaching up to 3000K, which is half the temperature of the sun—intended to “anchor” single atoms onto the substrate, offering superior thermal stability.

The research team led by MSE Professor Liangbing Hu, published their study in Nature Nanotechnology on August 12. Yonggang Yao, MSE Ph.D. Student and member of Dr. Hu’s research team, served as the lead author on the paper.

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Dyes and viruses create new composite materi…

Dyes and viruses create new composite material for photo-oxidation reactions

A recent study, published in Advanced Materials, shows that native viruses can be employed as a scaffold to immobilise photoactive molecules to potentially oxidise organic pollutants present in wastewater, under visible light irradiation

A research team from Aalto University has developed a novel strategy to create virus-based materials for catalysis. The project, which is framed within the Horizon 2020 Marie Skłodowska-Curie actions, aims to pave the way towards the application of optically active biohybrid materials—a combination of biomolecules and synthetic moieties—in topics ranging from nanomedicine to green organic synthesis or environmental sciences.

“Our first challenge was to select the right photosensitizer,” says Eduardo Anaya, postdoctoral researcher at Aalto University, “We decided to employ phthalocyanines, a synthetic derivative of hematoporphyrin (the dye responsible for the colour of blood), due to their outstanding properties as a reactive oxygen species generator. However, the use of this kind of dyes in aqueous media presents several challenges that affect their performance. Therefore, careful design was necessary to maintain their properties`.

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New synthesis method opens up possibilities …

New synthesis method opens up possibilities for organic electronics

Semiconducting polymers, large, chain-like molecules made from repeating subunits, are increasingly drawing the attention of researchers because of their potential applications in organic electronic devices. Like most semiconducting materials, semiconducting polymers can be classified as p-type or n-type according to their conducting properties. Although p-type semiconducting polymers have seen dramatic improvements thanks to recent advances, the same cannot be said about their n-type counterparts, whose electron conduction (or ‘electron mobility’) is still poor.

Unfortunately, high-performance n-type semiconducting polymers are necessary for many green applications, such as in types of solar cells. The main challenges holding back the development of n-type semiconducting polymers are the limited molecular design strategies and synthesis procedures available. Among the existing synthesis methods, DArP (which stands for ‘direct arylation polycondensation’) has shown promising results for producing n-type semiconducting polymers in an environmentally friendly and efficient way. However, until now, the building blocks (monomers) used in the DArP method were required to have an orienting group in order to produce polymers reliably, and this severely limited the applicability of DArP to make high-performance semiconducting polymers.

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A catalyst for sustainable methanol

The global economy still relies on the fossil carbon sources of petroleum, natural gas and coal, not just to produce fuel, but also as a raw material used by the chemical industry to manufacture plastics and countless other chemical compounds. Although efforts have been made for some time to find ways of manufacturing liquid fuels and chemical products from alternative, sustainable resources, these have not yet progressed beyond niche applications.

Scientists at ETH Zurich have now teamed up with the French oil and gas company Total to develop a new technology that efficiently converts CO2 and hydrogen directly into methanol. Methanol is regarded as a commodity or bulk chemical. It is possible to convert it into fuels and a wide variety of chemical products, including those that today are mainly based on fossil resources. Moreover, methanol itself has the potential to be utilised as a propellant, in methanol fuel cells, for example.

Nanotechnology

The core of the new approach is a chemical catalyst based on indium oxide, which was developed by Javier Pérez-Ramírez, Professor of Catalysis Engineering at ETH Zurich, and his team. Just a few years ago, the team successfully demonstrated in experiments that indium oxide was capable of catalysing the necessary chemical reaction. Even at the time, it was encouraging that doing so generated virtually only methanol and almost no by-products other than water. The catalyst also proved to be highly stable. However, indium oxide was not sufficiently active as a catalyst; the large quantities needed prevent it from being a commercially viable option.

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cenchempics: Bubbling catalyst These photos sh…

cenchempics:

Bubbling catalyst

These photos show a boron-dipyrromethene (BODIPY) derivative under white light (left) and ultraviolet light. Chris Thomson, a PhD candidate working in Filipe Vilela’s lab at Heriot-Watt University, took the photos after purifying the BODIPY-based photocatalyst. After most of the solvent had evaporated off, Thomson tried to get the concentrated, oily residue to solidify by reducing the pressure. The remaining solvent became trapped in bubbles in the viscous residue. As the bubbles expanded, they pushed the concentration of the product—which was still slightly dissolved—past a critical point, and it rapidly solidified as a thin, crystalline film around the bubbles. Thomson says the vaporized solvent escaped through little holes, but the film remained stable. “The product has many potential applications, but in the immediate future I’m intending to use it to generate a polymer-supported organic photocatalyst for generating reactive oxygen species, useful for organic synthesis,” Thomson explains. The Vilela lab is researching ways to make heterogeneous photocatalysts more efficient.

Submitted by Chris Thomson/@VilelaLAB

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Eco-friendly composite catalyst and ultrasound removes pollutants from water

The research team of Dr. Jae-woo Choi and Dr. Kyung-won Jung of the Korea Institute of Science and Technology’s (KIST, president: Byung-gwon Lee) Water Cycle Research Center announced that it has developed a wastewater treatment process that uses a common agricultural byproduct to effectively remove pollutants and environmental hormones, which are known to be endocrine disruptors.

The sewage and wastewater that are inevitably produced at any industrial worksite often contain large quantities of pollutants and environmental hormones (endocrine disruptors). Because environmental hormones do not break down easily, they can have a significant negative effect on not only the environment but also the human body. To prevent this, a means of removing environmental hormones is required.

The performance of the catalyst that is currently being used to process sewage and wastewater drops significantly with time. Because high efficiency is difficult to achieve given the conditions, the biggest disadvantage of the existing process is the high cost involved. Furthermore, the research done thus far has mostly focused on the development of single-substance catalysts and the enhancement of their performance. Little research has been done on the development of eco-friendly nanocomposite catalysts that are capable of removing environmental hormones from sewage and wastewater.

The KIST research team, led by Dr. Jae-woo Choi and Dr. Kyung-won Jung, utilized biochar, which is eco-friendly and made from agricultural byproducts, to develop a wastewater treatment process that effectively removes pollutants and environmental hormones. The team used rice hulls, which are discarded during rice harvesting, to create a biochar** that is both eco-friendly and economical. The surface of the biochar was coated with nano-sized manganese dioxide to create a nanocomposite. The high efficiency and low cost of the biochar-nanocomposite catalyst is based on the combination of the advantages of the biochar and manganese dioxide.

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High reaction rates even without precious me…

High reaction rates even without precious metals

Non-precious metal nanoparticles could one day replace expensive catalysts for hydrogen production. However, it is often difficult to determine what reaction rates they can achieve, especially when it comes to oxide particles. This is because the particles must be attached to the electrode using a binder and conductive additives, which distort the results. With the aid of electrochemical analyses of individual particles, researchers have now succeeded in determining the activity and substance conversion of nanocatalysts made from cobalt iron oxide—without any binders. The team led by Professor Kristina Tschulik from Ruhr-Universität Bochum reports together with colleagues from the University of Duisburg-Essen and from Dresden in the Journal of the American Chemical Society, published online on 30 May 2019.

“The development of non-precious metal catalysts plays a decisive role in realising the energy transition as only they are cheap and available in sufficient quantities to produce the required amounts of renewable fuels,” says Kristina Tschulik, a member of the Cluster of Excellence Ruhr Explores Solvation (Resolv). Hydrogen, a promising energy source, can thus be acquired by splitting water into hydrogen and oxygen. The limiting factor here has so far been the partial reaction in which oxygen is produced.

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Pantry ingredients can help grow carbon nano…

Pantry ingredients can help grow carbon nanotubes

Baking soda, table salt, and detergent are surprisingly effective ingredients for cooking up carbon nanotubes, researchers at MIT have found.

In a study published this week in the journal Angewandte Chemie, the team reports that sodium-containing compounds found in common household ingredients are able to catalyze the growth of carbon nanotubes, or CNTs, at much lower temperatures than traditional catalysts require.

The researchers say that sodium may make it possible for carbon nanotubes to be grown on a host of lower-temperature materials, such as polymers, which normally melt under the high temperaturesneeded for traditional CNT growth.

“In aerospace composites, there are a lot of polymers that hold carbon fibers together, and now we may be able to directly grow CNTs on polymer materials, to make stronger, tougher, stiffer composites,” says Richard Li, the study’s lead author and a graduate student in MIT’s Department of Aeronautics and Astronautics. “Using sodium as a catalyst really unlocks the kinds of surfaces you can grow nanotubes on.”

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