Category: Chemistry

by Hillary Sanctuary, Ecole Polytechnique Federale de Lausanne

Motivated to turn greenhouse gases like carbon dioxide into high value chemicals like methanol, EPFL chemical engineers have developed a new method to make catalysts. Catalysts are major tools in the chemical industry and are largely made to make petrochemicals.

In this method, they have developed a way to build—with near atomic precision—metal clusters on solid supports that have the potential to improve catalytic activity. The results are published in Nature Catalysis.

“You want to produce as much product per time per catalyst as possible, and we’ve found that when a catalyst is prepared with near atomic precision, you get a more active material,” says Jeremy Luterbacher, professor at EPFL’s Laboratory of Sustainable and Catalytic Processing. “This technique is particularly interesting for difficult reactions like that of carbon dioxide with hydrogen gas for producing renewable methanol.”

A bit about catalysts

Though they are ubiquitous in industry, we most commonly interact with solid catalysts in the tailpipe of our car. There, a catalytic converter takes the exhaust from fuel combustion and helps to reduce the amount of toxic pollutants released into the air.

The engine of a car notably produces carbon monoxide (CO), an odorless and colorless toxic gas that, in high concentrations, can cause illness and death if inhaled. Inside the chamber is a catalyst, usually made of small platinum or palladium particles on a cheaper solid. This metal binds air and pollutants like carbon monoxide, and helps them react to produce the less toxic carbon dioxide (CO₂) gas into the air.

“A reaction can happen without a catalyst at high temperature. For instance, burning carbon monoxide in a flame makes it possible for the carbon monoxide and oxygen to crash together to form carbon dioxide because they’re hot enough for the collision to be sufficiently powerful,” explains Luterbacher.

“With a catalyst, the carbon monoxide and the oxygen are bound to a metal surface and they can react despite colliding at a lower temperature. It’s like they’re ice-skating on the surface of the catalyzer and the surface helps the transformation between the pollutant and the reactant along.”

The catalysts of the future need to be able to turn carbon dioxide, a greenhouse gas that’s the largest source of renewable carbon on our planet, into high value gases like methanol. This process takes place in a chemical reaction referred to as a hydrogenation, a difficult reaction since it can produce many things other than methanol. Making a catalyst that is active enough to transform carbon dioxide fast enough to methanol without making other products is a significant challenge.

Precision layering of the catalyst

To make a solid catalyst, a metal particle is deposited on top of a material with high surface area like a porous powder, to maximize contact with the reactant.

Luterbacher and his team wondered if they could control and speed up reactions by precisely controlling the catalyst composition, notably by choosing just the right amount of material to tune how tightly reactants would bind to the catalyst.

They had discovered in previous research that they could deposit islands of metals with near atomic precision on solid supports, a method called liquid-phase atomic layer deposition (ALD), perfect for creating precise catalyst active sites for enabling a reaction.

Indeed, depositing these small islands or clusters of several metals with near atomic precision allowed the EPFL team to hydrogenate carbon dioxide at rates that were more than 10 times higher than with a catalyst of the same composition but built without this control.

They used magnesium oxide as the support, which usually binds carbon dioxide too tightly to be reactive, and they deposited small zirconia islands, which is a material that usually binds carbon dioxide too lightly. Then, they added copper to bind the hydrogen. When placed together in just the right proportions, they seemed to have the right mix to make a lot of methanol quickly and little of anything else.

“Magnesium oxide is widely recognized as a stable material for CO₂ capture, but its strong affinity for CO₂ has limited its use as a catalyst support. We turned this limitation into an opportunity by teaming it up with zirconia.

“Finding the optimal balance for CO₂ affinity by combining MgO and ZrO₂ with differing properties was only achievable through the powerful tool of liquid-phase atomic layer deposition,” says Seongmin Jin, former postdoctoral researcher at LPDC and lead author of the study.

“If we compare the amount of catalyst material to its copper content, then our catalyzer is more active than even commercial catalysts. Our activity per active site is also superior. It’s worth noting that our activity per weight of catalyst material is still inferior to commercial equivalents because we need to figure out how to make many more of these clusters on the surface.

“But we’ve shown that it’s possible to achieve very high control even at the atomic level, and this control appears to be very important. This opens the avenues to explore many combinations of metals or possibilities,” concludes Luterbacher.

More information: Seongmin Jin et al, Atom-by-atom design of Cu/ZrOx clusters on MgO for CO2 hydrogenation using liquid-phase atomic layer deposition, Nature Catalysis (2024). DOI: 10.1038/s41929-024-01236-y

Journal information: Nature Catalysis 

Provided by Ecole Polytechnique Federale de Lausanne 

by Pacific Northwest National Laboratory

A recent collaboration among researchers from HUN-REN Wigner Research Center for Physics in Hungary and the Department of Energy’s Pacific Northwest National Laboratory, along with industry collaborators SandboxAQ and NVIDIA, has achieved unprecedented speed and performance in efforts to model complex metal-containing molecules.

The collaboration resulted in 2.5 times the performance improvement over previous NVIDIA graphics processing unit (GPU) calculations and 80 times the acceleration compared to similar calculations using central processing unit (CPU) methods. The research study, recently published in the Journal of Chemical Theory and Computation, sets a new benchmark for electronic structure calculations.

Accelerating molecular modeling

The research team’s efforts have enabled unprecedented calculations for complex biochemical systems, which include transition metal metalloenzymes. Such metal-containing catalysts are crucial in numerous industrial and biological processes, playing an essential role in facilitating chemical reactions.

These powerhouses of energy conversion are vital for many industries, including medicine, energy and consumer products. They accelerate chemical reactions, lowering the energy required and making processes more efficient and sustainable. Understanding and optimizing these catalysts is essential for addressing global challenges, such as clean energy production and environmental sustainability.

“When you have one or more metals in your system, then you have a lot of electronic states that are very close in energy, but behave differently, and that’s why it’s really important to make sure that you describe them accurately,” said Sotiris Xantheas, a PNNL Lab Fellow, a co-author of the research study, and a chemical physicist who leads the Center for Scalable and Predictive methods for Excitation and Correlated phenomena (SPEC), as well as the Computational and Theoretical Chemistry Institute at PNNL.

Highly correlated quantum chemistry calculations

The recent advances have been made possible by bringing together academic and industry experts with expertise in the development of tensor network state algorithms and high performance computing, led by Örs Legeza, a co-PI of the SPEC project, and his group at the HUN-REN Wigner Research Center for Physics, in Hungary, working with SandboxAQ’s team of scientists, led by co-author Martin Ganahl, to perform quantum chemistry calculations on NVIDIA GPUs.

The diverse team contributions underscore the importance of collaboration and point to an exciting future for the field powered by GPUs. For instance, this work implemented the ab initio Density Matrix Renormalization Group method, which describes physical properties of large, complex electronic structures on all GPUs within a single node for the first time.

The goal of the research was to achieve efficient and accurate solutions to the many-body Schrödinger equation. These algorithms are crucial for understanding the electronic structures of molecules and materials and require computational power only available on a few computing systems worldwide.

The group’s collective expertise and shared resources have helped push the boundaries of quantum chemistry, allowing for rapid iteration and refinement in the study of highly correlated complex chemical systems. The project illustrates the potential of large-scale calculations to revolutionize how scientists approach challenging quantum chemistry problems.

“With advancing computational hardware and the extension to multi-GPU, multi-node architectures are expected to enable even more comprehensive calculations beyond the current capabilities,” said Legeza, who also holds an appointment as a research fellow at the Institute for Advanced Study at the Technical University of Munich.

“The ongoing collaboration aims to adopt large-scale GPU-accelerated calculations, further enhancing the efficiency and accuracy of quantum chemistry computations, utilizing even more recent hardware developments.”

As noted in the published study, chemists today largely rely on their intuition because rapid, highly accurate calculations are often unattainable. The ability to quickly iterate on different choices of large active spaces enables a more systematic search. Today’s GPU computing frameworks, combined with AI-guided physics and new methods for generating training data for large quantitative machine learning models, are expected to contribute to applications in energy, sustainability and health.

“The combination of NVIDIA’s state-of-the-art hardware with cutting-edge simulation techniques like tensor network algorithms for quantum chemistry has the potential to unlock an entirely new field of discovery,” said Ganahl.

More information: Andor Menczer et al, Parallel Implementation of the Density Matrix Renormalization Group Method Achieving a Quarter petaFLOPS Performance on a Single DGX-H100 GPU Node, Journal of Chemical Theory and Computation (2024). DOI: 10.1021/acs.jctc.4c00903

Provided by Pacific Northwest National Laboratory 

by Chiba University

There have been many attempts to create monochromatic metallic materials, but few materials change luster color in response to external stimuli. In a recent breakthrough, researchers from Chiba University have prepared a diacetylene derivative-based metallic luster material that changes from silver to gold under UV irradiation.

These findings are expected to find applications in decorative items, printing inks, photomask patterning, UV laser lithography, and cosmetics.

Societies of the past and present have given high regard to precious metals like gold and silver. Both metals remind us of nobility and luxury. However, they are quite expensive, which restricts their applications. Therefore, materials with attractive but artificial gold- and silver-like metallic lusters are popular, finding use in jewelry, reflective materials, inks, and cosmetics.

Unfortunately, typical metallic luster materials cause environmental harm, rendering them unsustainable. Thus, scientists are actively searching for metal-free alternatives, examining organics such as thiophene, pyrrole, porphyrin, azobenzene, and stilbene derivatives. They have found some success in creating materials whose colors can be tuned by external stimuli while maintaining the metallic luster. However, the task still remains challenging.

Recently, a group of researchers from Chiba University, led by Professor Michinari Kohri and Kyoka Tachibana from the Graduate School of Engineering, in collaboration with scientists from Mitsubishi Pencil Co., Ltd., Tokyo University of Science, Keio University, and Yamagata University, has demonstrated the preparation of a metallic luster material that changes color from silver to gold under UV irradiation.

Their findings were published in ACS Applied Materials & Interfaces on September 14, 2024.

Highlighting the motivation behind this study, Prof. Kohri says, “Expanding on our earlier findings on biomimetic metallic luster materials, we conducted a targeted search for molecular structures capable of transitioning between silver and gold. This effort resulted in the identification of a novel material with desirable properties.”

In this study, researchers developed diacetylene (DA) derivative-based luster materials incorporating stilbenes via linkers at both ends, denoted as DS-DAn (where n represents the linker carbon number, ranging from 1 to 6). Varying n yielded diverse metallic luster and color change behaviors.

After several innovative experimental trials, the researchers observed that the stacked structure of platelet crystals comprising DS-DA1, the derivative with the shortest linker carbon chain, had a silver look. Its luster notably turned to gold upon UV irradiation, a remarkable external stimulus-based behavior.

The team attributed this to the unique crystal structure of DS-DA1 with two coexisting assembled states, revealing that partial topochemical polymerization (a polymerization method performed by monomers that are aligned in the crystal state) of DA within the structure modified its color tone from silver to gold.

The silver luster material developed in this study can express a golden luster selectively in specific areas using only light irradiation. It is also possible to add gradation colors of gold and silver. Thus, it has the potential to be useful in a variety of applications, such as decorative items, printing inks, and cosmetics.

“By eliminating metal components, our innovative material minimizes environmental footprint and weight. Moreover, its suitability for UV laser-based drawing techniques opens up new possibilities for high-end decorative printing. Further exploration of molecular structures may make it possible to express a wider variety of glossy colors,” concludes Prof. Kohri.

This work advances the fundamental science of DA polymerization and unlocks new opportunities for metallic luster materials with desirable properties in photomask patterning and UV laser lithography.

More information: Kyoka Tachibana et al, Silver to Gold Metallic Luster Changes in Stimuli-Responsive Diacetylene Derivatives Uniquely Arranged within Crystals, ACS Applied Materials & Interfaces (2024). DOI: 10.1021/acsami.4c14218

Journal information: ACS Applied Materials and Interfaces 

by Public Library of Science

A new study of human skeletal remains from the wreck of the 16th century English warship “Mary Rose” suggests that whether a person is right- versus left-handed may influence how their clavicle bone chemistry changes as they age. Dr. Sheona Shankland of Lancaster University, U.K., and colleagues present these findings in the open-access journal PLOS ONE on October 30, 2024.

The Mary Rose was part of the Tudor navy during Henry VIII’s reign. On July 19, 1545, it sank while engaging French ships in the Battle of the Solent. Excavated in the late 20th century, the ship’s artifacts and the crew’s skeletal remains were notably well preserved, allowing for extensive research into the belongings, appearance, and health of the crew members.

Now, Dr. Shankland and colleagues contribute new insights into the biology of 12 men aged 13 to 40 who sank with the ship. This work explored how the chemistry of bone might adjust in response to physical activity and aging, so a person’s bone chemistry may hold clues about their lifestyle.

In this case, the researchers analyzed human clavicles (collarbones) from the wreck using a non-destructive laser technique called Raman spectroscopy to reveal bone chemistry.

The analysis focused on organic proteins and inorganic minerals, as they are the two main components of bone. It revealed that, among the 12 men, mineral content increased with age, while protein content decreased, albeit to a lesser degree.

These age-related changes were more pronounced in right clavicles than in left clavicles. A higher proportion of people are naturally right- than left-handed, and at the time when the Mary Rose sank, left-handedness was associated with witchcraft and therefore strongly discouraged.

So, assuming right-handed preference among the crew, this finding suggests that handedness may have affected their clavicle chemistry, perhaps through putting more stress on their right side during repeated ship-related activities.

The authors note that more research on the Mary Rose clavicles will be needed to better understand these findings. Nonetheless, this study could contribute to ongoing understanding of handedness and age-related changes in bone chemistry, with potential implications for risk of fracture, osteoarthritis, and other bone conditions.

Dr. Sheona Shankland adds, “Having grown up fascinated by the Mary Rose, it has been amazing to have the opportunity to work with these remains. The preservation of the bones and the non-destructive nature of the technique allows us to learn more about the lives of these sailors, but also furthers our understanding of the human skeleton, relevant to the modern world.”

Dr. Jemma Kerns adds, “It has been a privilege to work with these unique and precious human remains to learn more about life for sailors in the 16th century while finding out more about changes to bone composition as we age, which is relevant to today’s health, has been fascinating.”

Prof. Adam Taylor adds, “This study sheds new light on what we know about the clavicle and its mineralization. The bone plays a critical role in attaching your upper limb to the body and is one of the most commonly fractured bones.”

Dr. Alex Hildred adds, “Our museum is dedicated to the men who lost their lives defending their country. The hull is surrounded on three sides by galleries containing their possessions, and we continue to explore their lives through active research. The non-destructive nature of Raman spectroscopy makes it an ideal research tool for investigating human remains.

“We are delighted that the current research undertaken by Lancaster Medical School not only provides us with more information about the lives of our crew, but also demonstrates the versatility of Raman. The fact that this research has tangible benefits today, nearly 500 years after the ship sank, is both remarkable and humbling.”

More information: Shining light on the Mary Rose: Identifying chemical differences in human aging and handedness in the clavicles of sailors using Raman spectroscopy, PLOS ONE (2024). DOI: 10.1371/journal.pone.0311717

Journal information: PLoS ONE 

Provided by Public Library of Science 

by Nick William Smith, Andrew John Fletcher and Warren McNabb, The Conversation

Have you ever looked down at your breakfast, lunch or dinner and considered where the ingredients traveled from to reach your plate?

A basic sandwich in New Zealand can easily represent five countries: an Australian wheat and Indian sesame seed roll, Danish salami, local lettuce and cheese, seasoned with Vietnamese pepper.

And because your food travels a long way to reach you, so does your nutrition.

Research on global food trade—particularly trade in cereals—has a long history. More recently, researchers have begun considering the nutrients—energy, protein, vitamins, minerals—that move around the world within traded food.

As we learn more about the global trade in nutrients we can build a better picture of how these key dietary ingredients are distributed, and how they affect global population health.

Mapping global nutrient trade

The Sustainable Nutrition Initiative undertakes modeling research on the links between global food production and the nutrition of the global population.

Working with researchers at the University of São Paulo and State University of Campinas in Brazil, we have now published a broader analysis of global nutrient trade over time and its impact on health.

It shows the variation in nutrient trade between countries with differing wealth, and some positive links between nutrient trade and health.

Our team built a large data set of all flows of food for human consumption between 254 countries from 1986 to 2020. From this, we worked out the flows of 48 essential nutrients over that period.

As this is too much information for a single scientific paper, the team built an interactive app to let anyone explore the data.

The paper itself focused on a few key nutrients: protein, calcium, iron and vitamins A and B12. These are often used in analyses of food security (having reliable access to enough affordable, nutritious food) because of their importance to human health.

Some of these nutrients are under-supplied in many parts of the world, particularly low-income countries. At the same time, nutrient trade over the 35 years we analyzed has grown rapidly, as shown in the chart below for vitamin B12.

The wealth and nutrient gap

High-income countries were the biggest importers of vitamin B12, but also the other nutrients analyzed, largely from trade with other high-income countries. This is despite those countries having only around 15% of the global population.

In contrast, low-income countries have little involvement in global trade of any nutrients. This limits their ability to improve dietary diversity and quality through food from outside their borders.

Most of New Zealand’s trading partners are in the higher-income brackets. Milk and meat dominate New Zealand protein exports, with China the major partner (see chart below).

The quantity of protein exported would meet the needs of nearly seven times New Zealand’s own population. In a country like China, of course, this is only a small fraction of the population.

In contrast, nearly 60% of New Zealand’s protein imports comes from Australia, largely in wheat and wheat products. And New Zealand imports enough protein to meet around half its population’s need.

We also analyzed the socioeconomic, demographic and health outcome data potentially associated with food consumption patterns and nutrient trade.

The findings suggest higher involvement in nutrient trade networks was significantly associated with improvements in infant mortality rates, lower prevalence of anemia in women of reproductive age, and greater life expectancy.

Food security and nutrition

It is concerning to see the low involvement of low-income countries in nutrient trade, particularly given the benefits it can bring for population health.

Our research provides context for how important traded nutrients are in meeting national population requirements. This knowledge can be used to identify weaknesses in the global food system, and which shocks (climatic, political or biological) might have the greatest consequences for nutrition.

These data can then be combined with other knowledge and modeling of food production, distribution and consumption at national levels to give a more complete view of food systems.

Food trade plays a key role in fostering food security and good nutrition. The trade has grown rapidly in both quantity and economic value over the past 35 years. Understanding its importance for healthy nutrition is essential.

by Liu Jia, Chinese Academy of Sciences

A research group led by Prof. Wan Yinhua from the Institute of Process Engineering of the Chinese Academy of Sciences has developed a catalyst with dual photocatalytic and biomimetic catalytic activity for the production of hydrogen peroxide (H₂O₂).

The strategy involves loading gold nanoparticles (AuNPs) onto graphite carbon nitride (GCN) nanosheets using polyethyleneimine (PEI) as a “bridge.” The study was published in the Chemical Engineering Journal.

H₂O₂, recognized as an environmentally friendly oxidant, is extensively used in various fields such as medical treatment, environmental restoration, fine chemicals, and electronics industries. However, the conventional method of H₂O₂ production relies on the anthraquinone process, which has several drawbacks including high energy consumption, the use of organic solvents, and safety hazards. Therefore, there is a pressing need to develop a sustainable and eco-friendly manufacturing process for H₂O₂.

Solar-driven photocatalysis is a promising alternative strategy for H₂O₂ production, and GCN is a popular choice in the field of photocatalysis due to its straightforward synthesis, cost-effectiveness, stable physical and chemical properties, and broad light absorption spectrum. However, GCN nanosheets alone have limited performance in photocatalytic H₂O₂ production in pure water due to the high energy barrier of water dissociation and low separation efficiency of charge carriers.

Hole sacrificial agents (acting as electron donors) such as ethanol, isopropanol, and benzyl alcohol are commonly used to improve the selectivity of oxygen reduction. However, the addition of organic agents has adverse environmental impacts, which is not conducive to the sustainability of H₂O₂ production. Therefore, it is crucial to engineer a GCN material with enhanced electron-hole pair separation efficiency to facilitate water oxidation and oxygen reduction.

“Inspired by photo-enzyme-coupled catalytic system in chloroplasts, we developed a composite catalyst by loading AuNPs (enzyme mimics) on GCN (photocatalyst) nanosheets using PEI as the ‘bridge’ (PEI-GCN/Au),” Prof. Wan said.

The introduction of PEI and AuNPs helps adjust the electronic structure of GCN, facilitating the rapid separation of photogenerated carriers. The surface plasmon resonance of AuNPs, when excited by incident light, promotes the activation of glucose molecules, elevating their reactivity with O₂ and improving the glucose oxidase-mimicking catalytic production of H₂O₂. The grafting of PEI and the addition of glucose enhance the O₂ adsorption on the catalyst surface.

The PEI-GCN/Au composite demonstrates exceptional H₂O₂ production efficiency (270 μmol g^-1 h^-1) under visible light irradiation, using only glucose, H₂O and O₂ as reactants. As a result, both the biomimetic catalytic and photocatalytic reduction of O₂ to H₂O₂ are enhanced, achieving a significant synergistic enhancement effect of 175%.

“This work establishes a paradigm of coupling biomimetic catalysis and photocatalysis for co-production of chemicals. It not only provides insights into the development of materials for efficient H₂O₂ production, but also introduces an innovative concept for integrating biocatalysis and photocatalysis,” said Prof. Luo Jianquan, the corresponding author of this study.

More information: Huiru Zhang et al, Biomimetic-photo-coupled catalysis for boosting H2O2 production, Chemical Engineering Journal (2024). DOI: 10.1016/j.cej.2024.149183

Provided by Chinese Academy of Sciences 

by Max Planck Society

The production of aluminum generates around 180 million tons of toxic red mud every year. Scientists at the Max-Planck-Institut für Eisenforschung, a center for iron research, have now shown how green steel can be produced from aluminum production waste in a relatively simple way. In an electric arc furnace similar to those used in the steel industry for decades, they convert the iron oxide contained in the red mud into iron using hydrogen plasma.

With this process, almost 700 million tons of CO₂-free steel could be produced from the 4 billion tons of red mud that have accumulated worldwide to date—which corresponds to a good third of annual steel production worldwide. As the Max Planck team shows, the process would also be economically viable.

According to forecasts, demand for steel and aluminum will increase by up to 60% by 2050. Yet the conventional production of these metals has a considerable impact on the environment. Eight percent of global CO₂ emissions come from the steel industry, making it the sector with the highest greenhouse gas emissions. Meanwhile, aluminum industry produces around 180 million tons of red mud every year, which is highly alkaline and contains traces of heavy metals such as chromium.

In Australia, Brazil and China, among others, this waste is at best dried and disposed of in gigantic landfill sites, resulting in high processing costs. When it rains heavily, the red mud is often washed out of the landfill, and when it dries, the wind can blow it into the environment as dust.

In addition, the highly alkaline red mud corrodes the concrete walls of the landfills, resulting in red mud leaks that have already triggered environmental disasters on several occasions, for example in China in 2012 and in Hungary in 2010. In addition, large quantities of red mud are also simply disposed of in nature.

Potential to save 1.5 billion tons of CO₂ in the steel industry

“Our process could simultaneously solve the waste problem of aluminum production and improve the steel industry’s carbon footprint,” says Matic Jovičevič-Klug, who played a key role in the work as a scientist at the Max-Planck-Institut für Eisenforschung. In a study published in the journal Nature, the team shows how red mud can be utilized as a raw material in the steel industry. This is because the waste from aluminum production consists of up to 60% iron oxide.

The Max Planck scientists melt the red mud in an electric arc furnace and simultaneously reduce the contained iron oxide to iron using a plasma that contains 10% hydrogen. The transformation, known in technical jargon as plasma reduction, takes just ten minutes, during which the liquid iron separates from the liquid oxides and can then be extracted easily. The iron is so pure that it can be processed directly into steel.

The remaining metal oxides are no longer corrosive and solidify on cooling to form a glass-like material that can be used as a filling material in the construction industry, for example. Other research groups have produced iron from red mud using a similar approach with coke, but this produces highly contaminated iron and large quantities of CO₂. Using green hydrogen as a reducing agent avoids these greenhouse gas emissions.

“If green hydrogen would be used to produce iron from the 4 billion tons of red mud that have been generated in global aluminum production to date, the steel industry could save almost 1.5 billion tons of CO₂,” says Isnaldi Souza Filho, Research Group Leader at the Max-Planck-Institut für Eisenforschung.

An economical process, including with green hydrogen and electricity

The heavy metals in the red mud can also be virtually neutralized using the process. “After reduction, we detected chromium in the iron,” says Jovičevič-Klug. “Other heavy and precious metals are also likely to go into the iron or into a separate area. That’s something we’ll investigate in further studies. Valuable metals could then be separated and reused.”

Additionally, heavy metals that remain in the metal oxides are firmly bound within them and can no longer be washed out with water, as can happen with red mud.

However, producing iron from red mud directly using hydrogen not only benefits the environment twice over; it pays off economically too, as the research team demonstrated in a cost analysis. With hydrogen and an electricity mix for the electric arc furnace from only partially renewable sources, the process is worthwhile, if the red mud contains 50% iron oxide or more.

If the costs for the disposal of the red mud are also considered, only 35% iron oxide is sufficient to make the process economical. With green hydrogen and electricity, at today’s costs—also taking into account the cost of landfilling the red mud—a proportion of 30 to 40% iron oxide is required for the resulting iron to be competitive on the market.

“These are conservative estimates because the costs for the disposal of the red mud are probably calculated rather low,” says Isnaldi Souza Filho. And there’s another advantage from a practical point of view: electric arc furnaces are widely used in the metal industry—including in aluminum smelters—as they are used to melt down scrap metal. In many cases, the industry would therefore need to invest only a little to become more sustainable.

“It was important for us to also consider economic aspects in our study,” says Dierk Raabe, Director at the Max-Planck-Institut für Eisenforschung. “Now it’s up to the industry to decide whether it will utilize the plasma reduction of red mud to iron.”

by Ziyan Yang

Electrocatalytic reduction of carbon dioxide (CO₂) is considered as an effective strategy for mitigating the energy crisis and the greenhouse effect. Among the multiple reduction products, CO is regarded as having the highest market value as it is a crucial feedstock for Fischer-Tropsch process which can synthesize high-value long-chain hydrocarbons.

Since the carbon dioxide reduction reaction (CO₂RR) has complex intermediates and multiple proton-coupled electron transfer processes, improving the reaction activity and products selectivity remain two great challenges.

Single-atom catalysts (SACs) have the advantages of high atom utilization, tunable coordination structure and excellent catalytic performance. In addition, due to the special electronic structure of nickel metal, it is more likely to lose electrons to form empty outermost d-orbitals and exhibit high activity and selectivity for CO₂RR to generate CO.

A team of scientists have summarized the considerable progress of Ni SACs in recent years. Their work is published in Industrial Chemistry & Materials.

“Designing novel catalysts to improve the activity and selectivity of CO₂RR is crucial for conquering the problem of energy crisis and environmental pollution,” said Yuhang Li, a Professor at East China University of Science and Technology, China,

“In this mini-review, we introduced three strategies used to improve the catalytic performance of Ni SACs, including different structures of supports, coordination structure regulation, and surface modification. In the end, we also summarized the existing challenges of Ni SACs and provided an outlook on future development in this field.”

SACs downsize the active sites to atomic scale and therefore get extraordinary electronic structure, powerful metal-support interactions, low-coordinated metal atoms, and maximum atom utilization at the same time. Hence, the application of SACs in CO₂RR could effectively control the distribution of products and alleviate the cost of products separation.

“Some research based on crystal-field theory has indicated that the d-orbital electronic configurations of central metals are significant to the selectivity and activity of CO₂RR,” Li said.

“In the case of nickel as the central metal atom, it is more likely to form the vacant outermost d-orbital to facilitate the electron transfer between the C atom of CO₂ and the Ni atom. Therefore, the absorbed CO₂ molecules can be efficiently activated. Ni SACs can also minimize the reaction potential of CO₂-CO conversion, which is of great importance to enhance the selectivity towards CO.”

“Ni SACs have achieved continuous progress in recent years. From a microscopic point of view, the design strategies include choosing different substrates, regulating the coordination structure and modifying the catalyst surface. The electronic structure of the active center is the most crucial factor affecting catalytic performance,” Li said.

There is still tremendous potential for Ni SACs in future designs and applications. Precise modulation of the microstructure provides more active sites and therefore further enhances the performance of Ni SACs. Optimization of the electrolytic cells and development of more types of electrolytes can expand the range of Ni SACs applications and enable large-scale commercialization in the future.

In addition, researchers think that developing more in-situ techniques to gain deeper insights into the relationship between material structure and properties can provide valuable guidance for designing higher-value Ni SACs.

“In this mini-review, our main goal is to provide readers with the current research progress in Ni SACs in CO₂RR and to show our insights into the design and application of single-atom catalysts,” Li said.

The research team includes Ziyan Yang, Rongzhen Chen, Ling Zhang, Yuhang Li, and Chunzhong Li from East China University of Science and Technology.

by Laurie Fickman, University of Houston

A million years ago, the oldest known species to walk upright like a human, the Homo erectus, had a human-like fascination with crystals. Historians can even pin down the possible reasons—crystals didn’t look like anything around at the time—trees, valleys, mountains. Crystals were a material to ponder, a fascinating diversion for the mind.

To this day, the human preoccupation with the magic of crystals continues to fill the mind’s eye of scientists who have developed ways to use crystals for everything from malaria cures to solar cells and semiconductors, catalysts and optical elements. Over the years crystals have become crucial constituents of the technologies that enable modern civilization.

University of Houston researcher Peter Vekilov and Frank Worley Professor of Chemical and Biomolecular Engineering, have published in PNAS an answer to how crystals are formed and how molecules become a part of them.

“For decades crystal growth researchers have dreamt of elucidating the chemical reaction between incoming molecules and the unique sites on a crystal surface that accept them, the kinks,” said Vekilov. “The mechanism of that reaction, i.e., the characteristic time scale and length scale, possible intermediates and their stabilities, has remained elusive and subject to speculation for over 60 years.”

The main obstacle to deeper understanding has been the lack of data on how molecules join in, connected to the complicated process of moving from the solution to where they grow.

To unravel the chemical reaction between a molecule that dissolves in liquid (solute) and a kink, Vekilov mobilized two transformational strategies, one using full organic pairs and the second, using four solvents with distinct structures and functions. Working with the molecules, he combined state-of-the-art experimental techniques including time-resolved in situ atomic-force microscopy at near-molecular resolution, X-ray diffraction, absorption spectroscopy and scanning electron microcopy.

That’s when Vekilov made a revolutionary discovery: Incorporation into kinks may occur in two steps divided by an intermediate state and the stability of this middle state is key in how crystals grow. It basically decides how fast or slow the crystals form because it affects how easily things can join in during the process

Though the new discoveries don’t date back to Homo sapien times, they do solve a 40-year-old riddle for Vekilov.

“The notions of an intermediate state and its decisive role in crystal growth refute and replace the dominant idea in the field, brought up by A.A. Chernov, my Ph.D. advisor, that the activation barrier for growth is determined by the solute-solvent interactions in the solution bulk,” he said.

The new paradigm of two step incorporation, mediated by an intermediate state, could help in understanding how small parts in a liquid can influence the detailed shapes of crystals found in nature.

“Equally important, this paradigm will guide the search for solvents and additives that stabilize the intermediate state to slow down the growth of, for instance, undesired polymorphs,” Vekilov said.

Vekilov’s team includes Jeremy Palmer, Ernest J and Barbara M Henley Associate Professor of chemical and biomolecular engineering; former graduate students Rajshree Chakrabarti and Lakshmanji Verma; and Viktor G. Hadjiev, Texas Center for Superconductivity at UH.

More information: Rajshree Chakrabarti et al, The elementary reactions for incorporation into crystals, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2320201121

Provided by University of Houston 

by Yongji Qin 

Hydrogen is widely recognized as a promising clean energy source, primarily due to its high energy density and the absence of carbon emissions during its utilization. This characteristic makes hydrogen an ideal candidate for addressing the growing energy demand and mitigating the environmental impact associated with the excessive use of non-renewable fossil fuels over the past decades.

To harness renewable energy from sources like solar, wind, and tidal power, a compelling strategy involves the conversion of this volatile energy into hydrogen. This approach not only aids in meeting the energy demand gap but also contributes to the overall sustainability of human society.

Presently, overall water splitting (OWS) is considered a viable method for hydrogen production. OWS, powered by renewable energy, facilitates the generation of hydrogen through the hydrogen evolution reaction (HER) on the cathode.

However, the Faradic efficiency of hydrogen production is impeded by the anodic oxygen evolution reaction (OER), which is characterized by sluggish kinetics and high thermodynamic potential.

Consequently, there is a pressing need for the development of advanced electrocatalysts for OER or other oxidation reactions with swift kinetics and low thermodynamic potentials.

An alternative approach gaining traction is overall hydrazine splitting (OHzS) for hydrogen production, leveraging the anodic hydrazine oxidation reaction (HzOR). HzOR exhibits fewer electrons and faster kinetics compared to OER, making it a promising avenue. Nevertheless, a significant challenge remains in the synthesis of bifunctional electrocatalysts for both HER and HzOR with low overpotentials.

Recently, a research team in China introduced a novel solution in the form of a two-dimensional multifunctional layered double hydroxide derived from a metal-organic framework sheet precursor. This material is supported by nanoporous gold, providing high porosity. The study is published in the journal Frontiers of Chemical Science and Engineering.

Remarkably, this electrocatalyst demonstrates dual appealing activities for both HER and HzOR. In practical terms, the OHzS cell exhibits superior performance, requiring only a cell voltage of 0.984 V to deliver 10 mA∙cm^-2, a notable improvement compared to the OWS system (1.849 V).

In addition, the electrolysis cell exhibits remarkable stability, operating continuously for more than 130 hours. This innovative approach not only enhances the efficiency of hydrogen production but also holds promise for a more sustainable and cleaner energy future.