(Press-News.org) Metals such as gold or platinum are often used as catalysts. In the catalytic converters of vehicles, for example, platinum nanoparticles convert poisonous carbon monoxide into non-toxic CO2. Because platinum and other catalytically active metals are expensive and rare, the nanoparticles involved have been made smaller and smaller over time.
"Single-atom" catalysts are the logical end point of this downsizing: The metal is no longer present as particles, but as individual atoms that are anchored on the surface of a cheaper support material. Individual atoms can no longer be described using the rules developed from larger pieces of metal, so the rules used to predict which metals will be good catalysts must be revamped - this has now been achieved at TU Wien. As it turns out, single atom catalysts based on much cheaper materials might be even more effective. These results have now been published in the journal Science.
Smaller is sometimes better
Only the outer atoms of the piece of metal can play a role in chemical processes - after all, the atoms inside never come into contact with the environment. In order to save material, it is therefore best to use tiny metal particles instead of large lumps, so that a greater proportion of the atoms reside at the surface. If we go to the ultimate limit and use individual atoms, every single atom is chemically active. Over the last decade the field of "single atom" catalysis has grown dramatically, achieving great success.
Wrong model, right solution
"The reasons why some precious metals are good catalysts was already researched in the 1970s," says Prof. Gareth Parkinson from the Institute for Applied Physics at TU Wien. "For example, Gerhard Ertl was awarded the Chemistry Nobel Prize in 2007 for providing atomic-scale insights into catalysis."
In a piece of metal, an electron can no longer be assigned to a specific atom; the electronic states result from the interaction of many atoms. "For individual atoms, the old models are no longer applicable" says Gareth Parkinson. "Individual atoms do not share electrons like a metal, so the electron bands, whose energy was key to explaining catalysis, simply do not exist in this case."
Gareth Parkinson and his team have therefore been intensively investigating the atomic mechanisms behind this single-atom catalysis in recent years. "In many cases the metals that we think of as good catalysts remain good catalysts in the form of individual atoms" says Gareth Parkinson. "In both cases it is the same electrons, the so-called d electrons, that are responsible for this."
Customized properties through tailored surfaces
Entirely new possibilities arise in single-atom catalysis that are not available when using ordinary metal particles: "Depending on the surface on which we place the metal atoms and which atomic bonds they form, we can change the reactivity of the atoms", explains Parkinson.
In some cases, particularly expensive metals like platinum are no longer necessarily the best choice. "Individual nickel atoms show great promise for carbon monoxide oxidation. If we understand the atomic mechanisms of single atom catalysis, we have a lot more leeway to influence the chemical processes," says Parkinson.
Eight different metals were precisely analyzed in this way at TU Wien - the results fit perfectly with the theoretical models that have now been developed in a collaboration with Prof. Cesare Franchini at the University of Vienna.
"Catalysts are very important in many areas, especially when it comes to chemical reactions that play a major role in attempts to develop a renewable energy economy," emphasizes Gareth Parkinson. "Our new approach shows that it doesn't always have to be platinum." The decisive factor is the local environment of the atoms - and if you choose it correctly, you can develop better catalysts and at the same time save resources and costs.
INFORMATION:
Contact
Prof. Gareth Parkinson
Institute for Applied Physicd
TU Wien
Wiedner Hauptstraße 8-10, 1040 Vienna
+43 1 58801 13473
gareth.parkinson@tuwien.ac.at
Normal ageing causes disruptions in the brain that can lead to cognitive decline. Resting-state functional magnetic resonance imaging studies have found significant age-related alterations in functional connectivity across various networks. However, most of the studies have focused primarily on static functional connectivity.
The authors of a recent study published in Cerebral Cortex based their research on the idea that studying the dynamics of resting-state brain activity across the whole-brain functional network can provide a better characterization of age-related changes.
The study was led by Gustavo Deco, director of the Center for Brain and Cognition (CBC) and ICREA research professor at the UPF Department of Information and Communication Technologies (DTIC), and Anira ...
Chimpanzees, one of the closest relatives of humans, cooperate on a group level - in combative disputes, they even cooperate with group members to whom they are not related. Those involved in fights with neighbouring groups put themselves at risk of serious injury or even death.
Within the context of the Tai Chimpanzee Project researchers observed three chimpanzee communities in Tai National Park in Cote d'Ivoire documenting social relationships, territory range and intergroup encounters amongst others. "We have been able to analyze almost 500 vocal and physical battles from the last 25 years with participation of at least one ...
Good news for the green transition: Flowery diets help predatory insects help farmers keep pests in check
Predatory insects have been shown to live longer when they have access to nectar and pollen, according to a new study by researchers at the University of Copenhagen. Thus, flowers don't just benefit insects, they help farmers farm sustainably. Predatory insects are skilled pest controllers whose hunting reduces the need for agricultural pesticides.
Until now, it was believed that predatory insects needed prey to survive. But in a systematic review conducted at the University ...
Researchers in WMG at the University of Warwick, in collaboration with Imperial College London, have found a way to enhance hybrid flow batteries and their commercial use. The new approach can store electricity in these batteries for very long durations for about a fifth the price of current technologies, with minimal location restraints and zero emissions.
The researchers enhanced three hybrid flow cells using nitrogen doped graphene (exposed to nitrogen plasma) in a binder-free electrophoresis technique (EPD).
Wind and solar power are increasingly popular sources for renewable energy. Unfortunately, intermittency issues keep them ...
GREEN TRANSITION Researchers at the University of Copenhagen have demonstrated that unique fungi strengthen the "immune systems" of wheat and bean plants against aphids. Fungi enter and influence the amount of a plant's own defences, resulting in fewer aphids. The results could serve to reduce agricultural insecticide use and bring Denmark a step further along the path towards its green transition.
Wheat field
Certain fungi are able to establish a close rapport with plants that results in fewer insect infestations and thereby less damage to crops. Until now, it was unclear how these fungi could be used to reduce insect infestations.
"In order for us to really use fungi ...
PHILADELPHIA, PA (January 22, 2021) - Advancements in diabetes technology have improved quality of life and glycemic control in children with type 1 diabetes. However, data show that a subset of children is being left behind. Those from low-income families and non-Hispanic Black (NHB) children are not experiencing benefits associated with technological advances, and are at higher risk for diabetes complications and adverse outcomes through ongoing poor glycemic control.
In an invited commentary to be published in the journal Diabetes Care, researchers describe how socioeconomic disparities ...
Researchers from Queen Mary University of London, have identified a protein that may represent a novel therapeutic target for the treatment of pancreatic cancer. Using this protein as a target, the team successfully created a CAR T cell therapy - a type of immunotherapy - that killed pancreatic cancer cells in a pre-clinical model.
CAR T cell therapy is an immunotherapy that has shown great promise for the treatment of some blood cancers; however, the treatment of solid tumours using this therapy has proved very difficult. One barrier to success is toxicity in tissues other than the cancer because most of the proteins currently used to target CAR T cells to pancreatic cancer cells and other solid tumours are present in low levels on other normal tissues, ...
Organic photodetectors (OPDs) have a huge potential for applications in low-cost imaging, health monitoring and near infrared sensing. Yet, before industrially realizing these applications, the performance of these devices still needs to be improved.
Recent research on organic photodetectors based on donor-acceptor systems has resulted in narrow-band, flexible and biocompatible devices, of which the best reach external photovoltaic quantum efficiencies of close to 100%. However, the high noise in the off state produced by these devices limits their specific detectivity, severely reducing the performance, for example ...
Popular in aquariums all over the world, the zebrafish is native to South Asia. But here in a Cincinnati Children's laboratory, the freshwater variant plays a vital role in scientific discovery.
The iconic stripes are eye-catching but it's the transparency of zebrafish embryonic tissue which are most prized by researchers like Oriana Zinani, a fifth-year doctoral student in molecular developmental biology in the University of Cincinnati College of Medicine. The patterning of the zebrafish's spine gives the appearance of stripes; it is controlled by ...
In science, sometimes a new perspective can turn our interpretation of the data upside-down, and necessitate a paradigm shift.
There has been, and continues to be, fierce disagreements in nutrition science as to what constitutes a healthy diet. A key controversy is the role of saturated fats in health and disease. Saturated fats are known to increase blood cholesterol levels, and increased blood cholesterol is often observed in people who develop cardiovascular disease.
It has been thought for more than half a century that saturated fats in the diet promote heart disease by increasing blood cholesterol. However, a new model explains why this so-called "diet-heart hypothesis", which ...
