The environmentally harmful greenhouse gas carbon dioxide, or CO₂ for short, can be converted into valuable chemical products such as carbon monoxide (CO) or ethanol by means of electrochemical reduction—electrolysis. These can be used as raw materials for industry or for the sustainable provision of energy. However, a key obstacle to the long-term stability of this technology is the water and salt management within the electrolytic cell in which the chemical reaction takes place.
The research team led by Dr. Joey Disch and PD Dr. Severin Vierrath from Hahn-Schickard and the University of Freiburg, in collaboration with the French Institut Laue-Langevin in Grenoble, has made significant progress in understanding the distribution of water during CO₂ electrolysis. Their study was first published in the ACS Energy Letters and has now been featured as a Research Highlight in the February issue of Nature Catalysis.
The study uses high-resolution neutron imaging—one of the most powerful methods for directly investigating water transport in electrolyzers—to visualize the transport mechanisms during the pulsed operation of a CO₂ electrolyzer.
With a spatial resolution of 6 μm, this method allows a highly precise investigation of water distribution and salt formation under realistic operating conditions (400 mA cm⁻² at a cell voltage of 3.1 V and a Faradaic efficiency for CO of 95%). In contrast to X-rays, neutrons easily penetrate even metallic components, while making hydrogen and thus water-containing structures highly visible.
The results show a significant stabilization of the electrolyzer during pulsed operation, in which the cell potential is periodically set to a potential below the onset of reduction for a short time. Neutron imaging provides an explanation for the stabilization and illustrates that during the brief interruptions in operation, the water content in the gas diffusion layer increases, which promotes the breakdown of obstructive salt deposits.
Electrochemical CO₂ reduction opens up promising prospects for a sustainable transformation of the chemical industry. In particular, CO₂ electrolysis for the production of carbon monoxide is on the threshold of industrial application: Electrolysis cells with anion exchange membranes are already impressing with remarkable efficiency thanks to optimized reactant management and minimized resistance losses.
These findings thus provide valuable information for optimizing the design and operation of CO₂ electrolyzers, enhancing their efficiency and long-term stability, and facilitating the removal of the harmful greenhouse gas CO₂ from the environment.
More information: Luca Bohn et al, High-Resolution Neutron Imaging of Water Transport in CO2 Electrolysis during Pulsed Operation, ACS Energy Letters (2025). DOI: 10.1021/acsenergylett.4c03003
Artistic rendering of the unusual behavior of azulene. Credit: Tomáš Belloň / IOCB Prague
Researchers at IOCB Prague are the first to describe the causes of the behavior of one of the fundamental aromatic molecules, which fascinates the scientific world not only with its blue color but also with other unusual properties—azulene. Their current undertaking will influence the foundations of organic chemistry in the years to come and in practice will help harness the maximum potential of captured light energy. Their article appears in the Journal of the American Chemical Society (JACS).
Azulene has piqued the curiosity of chemists for many years. The question of why it is blue, despite there being no obvious reason for this, was answered almost 50 years ago by a scientist of global importance, who, coincidentally, had close ties with IOCB Prague, Prof. Josef Michl.
Now, Dr. Tomáš Slanina is following in his footsteps in order to offer his colleagues in the field the solution to another puzzle. He and his colleagues have convincingly described why the tiny azulene molecule violates the universal Kasha’s rule.
This rule explains how molecules emit light upon transitioning to various excited states. If we use the analogy of an ascending staircase, then the first step (the first excited state of the molecule) is high, and each subsequent step is lower and therefore closer to the previous one. The smaller the distance between the steps, the faster the molecule tends to fall from the step to lower levels. It then waits the longest on the first step before returning to the base level, whereupon it can emit light. But azulene behaves differently.
To explain the behavior of azulene, researchers at IOCB Prague used the concept of (anti)aromaticity. Again, simply put, an aromatic substance is not characterized by an aromatic smell but by being stable, or satisfied, if you will. Some chemists even refer to it informally with the familiar smiley face emoticon.
An antiaromatic substance is unstable, and the molecule tries to escape from this state as quickly as possible. It leaves the higher energy state and falls downward. On the first step, azulene is unsatisfied, i.e. antiaromatic, and therefore falls downward in the order of picoseconds without having time to emit light.
On the second step, however, it behaves like a satisfied aromatic substance. And that is important. It can exist in this excited state for even a full nanosecond, and that is long enough to emit light. Therefore, the energy of this excited state is not lost anywhere and is completely converted into a high-energy photon.
With their research, Slanina’s team is responding to the needs of the present, which seeks a way to ensure that the energy from photons (e.g., from the sun) captured by a molecule is not lost and that it can be further used (e.g., to transfer energy between molecules or for charge separation in solar cells).
The goal is to create molecules that manage light energy as efficiently as possible. Additionally, in the current paper, the researchers show in many cases that the property of azulene is transferable; it can be simply attached to the structure of any aromatic molecule, thanks to which that molecule gets the key properties of azulene.
Tomáš Slanina adds, “I like theories that are so simple you can easily envision, remember, and then put them to use. And that’s exactly what we’ve succeeded in doing. We’ve answered the question of why molecules behave in a certain way, and we’ve done it using a very simple concept.”
In their research, the scientists at IOCB Prague used several unique programs that can calculate how electrons in a molecule behave in the aforesaid higher excited states. Little is known about these states in general, so the work is also groundbreaking because it opens the door to their further study. Moreover, the article published in JACS is not only computational but also experimental.
Researchers from Tomáš Slanina’s group supported their findings with an experiment that accurately confirmed the correctness of the calculated data. They also collaborated with one of the world’s most respected authorities in the field of (anti)aromatic molecules, Prof. Henrik Ottosson of Uppsala University in Sweden. And this is the second time JACS has taken an interest in their collaboration; the first time was in relation to research on another primary molecule—benzene.
Yet the story of azulene is even more layered. It concerns not only photochemistry but also medicine. Like the first area, the second also bears the seal of IOCB Prague—one of the first drugs developed in its laboratories was an ointment based on chamomile oil containing a derivative of azulene.
Over the decades, the little box labeled Dermazulen, which contains a preparation with healing and anti-inflammatory effects, has found its place in first-aid kits throughout the country.
More information: David Dunlop et al, Excited-State (Anti)Aromaticity Explains Why Azulene Disobeys Kasha’s Rule, Journal of the American Chemical Society (2023). DOI: 10.1021/jacs.3c07625
Credit: Frontiers of Chemical Science and Engineering (2023). DOI: 10.1007/s11705-023-2373-1
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.
Graphical abstract. Credit: Angewandte Chemie International Edition (2024). DOI: 10.1002/anie.202400161
Glass can be synthesized through a novel “crystal-liquid-glass” phase transformation. Crystalline materials can be fine-tuned for desired properties such as improved mass transfer and optical properties through coordination chemistry and grid chemistry design principles.
However, how to induce the local structural disorder of crystalline materials to achieve glass transition remains a challenge because most of them undergo decomposition before melting.
In the metal-organic framework system, the exploration of glassy states is limited to a few model compounds such as ZIF-4, ZIF-62 and ZIF-8. There is a need to break the limitation of metals and ligands in the “crystal-liquid-glass” process and to develop the glass synthesis pathway of universal crystalline materials.
In a study published in Angewandte Chemie International Edition, a research group led by Prof. Zhang Jian and Prof. Fang Weihui from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences reported the meltable aluminum molecular rings with fluorescence and nonlinear optical properties.
Inspired by the characteristics of deep eutectic solvent (DES) mixtures involving significant depressions in melting points compared to their neat constituent components, the researchers designed and synthesized the first examples of meltable aluminum oxo clusters via lattice doping with DESs at the molecular level.
This kind of molecular ring compound undergoes a crystal-liquid-glass process after heating. The abundant and strong hydrogen bonds between the aluminum molecular ring, DES components and the lattice solvent in the structure are considered to be the root cause of the lower melting point. This lattice doping bonding method provides a general preparation method for the development of cluster glass.
The researchers determined the composition changes of the compounds before and after melting and quenching by modern characterization methods and in situ temperature monitoring (TG-IR-MS). They tried to mix DES solvent with an empty Al8 ring by physical doping, and found no melting phenomenon in the mixture after heating, which proves the importance of doping the DES component in the lattice, that is, DES component forms a “supracluster” structure with aluminum molecular ring.
Owing to the plasticity of the cluster glass “soft material,” the researchers explored its machinability and optical properties. They prepared the bubble-free glass film by a simple “hot pressing” method under atmospheric pressure, and well maintained the luminescence and third-order nonlinear effect similar to that of the original crystal.
The forming of this cluster glass film does not require additional mixed media, which is different from the traditional substrate bonding method, revealing the advantages of cluster glass.
This study demonstrates the potential of aluminum-related glass prepared by the third most abundant metal in the Earth’s crust, for sustainable development. The strategy combining the aluminum molecular ring and ionic liquid component overcomes the limitation of metal and ligand type of crystal glass, and provides a better approach for the study of “crystal-liquid-glass.”
More information: San-Tai Wang et al, Meltable Aluminum Molecular Rings with Fluorescence and Nonlinear Optical Properties, Angewandte Chemie International Edition (2024). DOI: 10.1002/anie.202400161
by Nick William Smith, Andrew John Fletcher and Warren McNabb, The Conversation
Vitamin B12 trade by country income classification, 1986-2020: H = high-income countries, UM = upper middle-income , LM = lower middle-income, L = low-income, ODU = origin or destination not recorded. Credit: Nick William Smith, CC BY-SA
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.
New Zealand protein exports by country and food group. Credit: Nick William Smith, CC BY-SA
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.
The proposed mechanism for the H2O2 production by PEI-GCN/Au biomimetic-photo-coupled catalysis. Credit: Zhang Huiru
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
Phase evolution of red mud with hydrogen plasma processing and mechanism of iron recovery. Credit: Nature (2024). DOI: 10.1038/s41586-023-06901-z
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 generation, storage and hazards of red muds and solution with hydrogen plasma treatment. Credit: Nature (2024). DOI: 10.1038/s41586-023-06901-z
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.”
Strategies to enhance the performance of nickel single-atom catalysts for the electroreduction of CO2 to CO. Credit: Yuhang Li, Chunzhong Li, East China University of Science and Technology, China
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.
Peter Vekilov, University of Houston Frank Worley Professor of Chemical and Biomolecular Engineering, has published that incorporation of molecules into crystals occurs in two steps, divided by an intermediate state. Credit: 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
From smartphones to wind turbines, rare earth elements (REEs) are an essential part of the hardware in many advanced technologies. These elements, which include the lanthanides along with scandium and yttrium, are the backbone of industries that rely on unique properties such as luminescence, magnetism and catalytic ability. In fact, as our world moves toward more sustainable energy solutions and increasingly sophisticated technologies, the demand for REEs is projected to grow substantially.
There’s one catch, however: REEs are difficult to extract and even harder to separate. These elements, despite their name, aren’t actually rare in terms of abundance. What makes them “rare” is their dispersion throughout the Earth’s crust and their chemical similarities, which make them incredibly challenging to isolate from one another.
Current separation methods—largely reliant on toxic solvents like kerosene—are not only inefficient, but also harmful to people and the environment. Additionally, while the U.S. once dominated REE mining and production, environmental restrictions on current separation methods have limited domestic production.
Kathleen Stebe, Richer & Elizabeth Goodwin Professor in Chemical and Biomolecular Engineering (CBE), is tackling this challenge head-on with a collaborative group of researchers across five institutions under the support of a grant from the Department of Energy. Stebe is leading a groundbreaking research initiative that aims to create an eco-friendly, bioinspired process for separating REEs that would also avoid shipping semi-processed REEs to other countries for purification.
“Current separation methods use kerosene and extractants-molecules that bind the REE cations, a positively charged particle, that create issues, both environmentally and in terms of efficiency,” says Stebe. “The separation process is not selective enough to efficiently separate lanthanides, meaning that it has to be repeated many times to achieve REEs in sufficient purity. The whole method is cumbersome and creates unnecessary waste.”
Stebe, along with a team of researchers from Penn, the City College of New York, the University of Illinois Chicago, Northwestern University and the University of Chicago, look to human biology to find the molecule best suited for the job of separation: peptides.
Bioinspired interfaces: Drawing on nature’s expertise
In nature, organisms have evolved proteins that selectively bind to specific ions, despite their similar properties. A perfect example of this is calcium-binding proteins in the human body, which can distinguish between calcium and magnesium ions, even though both have the same charge.
“We are applying this concept to create a similar level of selectivity for rare earth elements,” says collaborator E. James Petersson, professor of chemistry, biochemistry and biophysics at Penn’s School of Arts & Sciences. “By using peptide-based molecules—specifically, a truncated version of the EF-hand motif, which is naturally found in calcium-binding proteins—we are designing molecules that can selectively bind to specific rare earth elements.”
This EF-hand motif refers to the structure and mechanism through which these naturally occurring proteins and peptides are able to differentiate between two very similar molecules.
“The structure resembles a hand,” says Stebe, “and each ‘finger’ of the hand is laden with a carboxyl or carbonyl group that binds to cations floating around in solution. It’s a beautiful and complex structure that can recognize the nuanced and subtle differences between two nearly indistinct cations, and then capture and hold onto whichever cation it is ‘looking’ for. This is extremely important for separating REEs, which differ in size by only one-tenth of an angstrom.”
In the team’s recent study published in the Proceedings of the National Academy of Sciences, they found that EF-hand-containing peptides could bind to the peptide-cation complex and capture it at the aqueous-air interface. The vision includes using bubbles to separate specific lanthanides from a mixture. Once bound to the peptides in an aqueous solution, the REEs will rise to the surface, where they are trapped in a foam at the water-air interface, a separation technique called ion foam flotation.
“My primary area of research is in interfacial science, studying the adsorption of surface-active molecules—surfactants and soap molecules—to the air-water interface,” says co-author Charles Maldarelli, professor of chemical engineering at The City College of New York. “This study gave me the opportunity to apply my expertise to the adsorption of peptides and peptide-metal complexes at the interface.”
Felipe Jimenez-Angeles, research associate professor at Northwestern University, performed many of the molecular dynamics simulations in this study. “I am fascinated that these peptides can separate ions that only differ by a few tenths of an Angstrom in diameter via the differences in the electrostatic forces at the atomic scale. The water-soluble peptide reconfigures when it captures the ion and becomes insoluble in water, resulting in its adsorption to the air-water interface.”
The team’s next steps in this research will be investigating how to scale this process, allowing them to isolate target REEs and collect them at usable quantities in a way that is much more efficient and environmentally friendly.
The collaborative effort behind the innovation
What makes this project truly innovative is the collaboration across multiple universities and disciplines. Each institution brings unique expertise to the project, from synthetic chemistry to surface material properties, and even X-ray experiments.
“This is really the first time my lab has used biology to solve chemistry problems,” says Petersson. “Normally, we focus on creating chemical probes to study biology, often looking at neurodegenerative disorders like Parkinson’s disease. But the experience of working on this project has inspired me to explore other biological approaches to chemistry, including adapting disease-related proteins for applications in other fields like energy and sustainability.”
“I have long been interested in molecular interface interactions,” adds Ivan Dmochowski, Professor of Chemistry in Penn’s School of Arts & Sciences. “As an undergraduate, I made molecules that react with the surface of glass and gold, and studied the resulting monolayers that formed. Later I started looking at proteins at the air-water interface.”
Other key senior faculty involved in the research include Monica Olvera de la Cruz from Northwestern University, Raymond Tu from CCNY, Mark Schlossman from the University of Illinois at Chicago, and Daeyeon Lee, Ravi Radhakrishnan and Cesar de la Fuente at the University of Pennsylvania.
“It has been rewarding to both contribute to and learn from this effort,” continues Dmochowski. “To solve really challenging, societally relevant problems in 2025, we will need a wide range of technical expertise, and I am excited to continue working with this team of collaborators to do that.”
Looking ahead: The future of rare earth element recovery
As Stebe’s team continues their work, they are focused on fine-tuning the selectivity of the peptides and optimizing the process for bulk production. Their next steps include using specialized peptides designed by Petersson to enhance the fluorescence of the system, allowing for more precise tracking of the binding events. They also plan to use physics data to inform additional opportunities for improved specificity and look into developing new, synthetic molecules to make this method even more cost-effective and environmentally friendly.
“This is just the beginning,” says Stebe. “We have a lot of exciting new directions to explore, from using synthetic molecules instead of peptides to creating even more selective binding structures. The potential impact of this work goes far beyond just rare earth elements—it could revolutionize the way we approach material separation across many industries.”
More information: Luis E. Ortuno Macias et al, Lanthanide binding peptide surfactants at air–aqueous interfaces for interfacial separation of rare earth elements, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2411763121
