Unprecedented view of a single catalyst nanoparticle at work
X-rays reveal compositional changes on active surface under reaction conditions
Science Communication Lab für DESY
Science Communication Lab für DESY
Catalysts are materials that promote chemical reactions without being consumed themselves. Today, catalysts are used in numerous industrial processes, from fertiliser production to manufacturing plastics. Because of this, catalysts are of huge economic importance. A very well-known example is the catalytic converter installed in the exhaust systems of cars. These contain precious metals such as platinum, rhodium and palladium, which allow highly toxic carbon monoxide (CO) to be converted into carbon dioxide (CO2) and reduce the amount of harmful nitrogen oxides (NOx).
“In spite of their widespread use and great importance, we are still ignorant of many important details of just how the various catalysts work,” explains Stierle, head of the DESY NanoLab. “That’s why we have long wanted to study real catalysts while in operation.” This is not easy, because in order to make the active surface as large as possible, catalysts are typically used in the form of tiny nanoparticles, and the changes that affect their activity occur on their surface.
Surface strain relates to chemical composition
In the framework of the EU project Nanoscience Foundries and Fine Analysis (NFFA), the team from DESY NanoLab has developed a technique for labelling individual nanoparticles and thereby identifying them in a sample. “For the study, we grew nanoparticles of a platinum-rhodium alloy on a substrate in the lab and labelled one specific particle,” says co-author Thomas Keller from DESY NanoLab and in charge of the project at DESY. “The diameter of the labelled particle is around 100 nanometres, and it is similar to the particles used in a car’s catalytic converter.” A nanometre is a millionth of a millimetre.
Using X-rays from the European Synchrotron Radiation Facility ESRF in Grenoble, France, the team was not only able to create a detailed image of the nanoparticle; it also measured the mechanical strain within its surface. “The surface strain is related to the surface composition, in particular the ratio of platinum to rhodium atoms,” explains co-author Philipp Pleßow from the Karlsruhe Institute of Technology (KIT), whose group computed strain as a function of surface composition. By comparing the observed and computed facet-dependent strain, conclusions can be drawn concerning the chemical composition at the particle surface. The different surfaces of a nanoparticle are called facets, just like the facets of a cut gemstone.
When the nanoparticle is grown, its surface consists mainly of platinum atoms, as this configuration is energetically favoured. However, the scientists studied the shape of the particle and its surface strain under different conditions, including the operating conditions of an automotive catalytic converter. To do this, they heated the particle to around 430 degrees Celsius and allowed carbon monoxide and oxygen molecules to pass over it. “Under these reaction conditions, the rhodium inside the particle becomes mobile and migrates to the surface because it interacts more strongly with oxygen than the platinum,” explains Pleßow. This is also predicted by theory.
“As a result, the surface strain and the shape of the particle change,” reports co-author Ivan Vartaniants, from DESY, whose team converted the X-ray diffraction data into three-dimensional spatial images. “A facet-dependent rhodium enrichment takes place, whereby additional corners and edges are formed.” The chemical composition of the surface, and the shape and size of the particles have a significant effect on their function and efficiency. However, scientists are only just beginning to understand exactly how these are connected and how to control the structure and composition of the nanoparticles. The X-rays allow researchers to detect changes of as little as 0.1 in a thousand in the strain, which in this experiment corresponds to a precision of about 0.0003 nanometres (0.3 picometres).
Crucial step towards analysing industrial catalyst materials
“We can now, for the first time, observe the details of the structural changes in such catalyst nanoparticles while in operation,” says Stierle, Lead Scientist at DESY and professor for nanoscience at the University of Hamburg. “This is a major step forward and is helping us to understand an entire class of reactions that make use of alloy nanoparticles.” Scientists at KIT and DESY now want to explore this systematically at the new Collaborative Research Centre 1441, funded by the German Research Foundation (DFG) and entitled “Tracking the Active Sites in Heterogeneous Catalysis for Emission Control (TrackAct)”.
“Our investigation is an important step towards analysing industrial catalytic materials,” Stierle points out. Until now, scientists have had to grow model systems in the laboratory in order to conduct such investigations. “In this study, we have gone to the limit of what can be done. With DESY’s planned X-ray microscope PETRA IV, we will be able to look at ten times smaller individual particles in real catalysts, and under reaction conditions.”
Other news from the department science
Leibniz Prize for chemist Prof. Dr. Peter R. Schreiner
Germany's most important research funding prize goes to scientist at the University of Giessen
Non-toxic plasticisers for use in elastomers and thermoplastics
Bio-based plasticizers from Central Germany
Wood materials make for reliable organic solar cells
Kraft lignin improves the stability in organic solar cells thanks to its ability to form hydrogen bonds that acts as a sort of glue
Argonne and Idaho National Laboratories partner with CMBlu Energy for innovative long-duration energy storage project
The project aims to improve microgrids in cold climates and make fast charging of electric vehicles more affordable in underserved communities
Blue-green algae sugar instead of glyphosate
Cooperation project develops environmentally friendly glyphosate alternative
Using clay to combat eternal toxins
TU Freiberg clarifies basis for innovative PFAS filter made of clay
Unveiling a new era of imaging: Boston University engineers lead breakthrough microscopy techniques
Researchers made significant advancements in the field of vibrational imaging
Phasing out fossil fuels could save millions of lives
The mortality burden attributable to air pollution from fossil fuel use is considerably higher than most previous estimates - a phaseout of fossil fuels would have tremendous, positive health outcomes
Replicating the structure of bird feathers
The new material could be used in batteries or filtration
Quantum tool opens door to uncharted phenomena
Method can contribute to a better understanding of quantum materials
Recovering instead of shredding: recycling batteries more efficiently
KIT researchers are working with industry to develop a more sustainable recycling process to recycle materials from lithium-ion batteries more effectively
Industry 4.0: No impact on energy consumption?
To what extent does the digitalisation of industrial and manufacturing processes (Industry 4.0) improve energy efficiency and thus reduce energy intensity?
New approach to the sensible utilisation of carbon dioxide from car exhaust gases
"A method has been discovered that uses impure CO2 streams and enables a breakthrough in the synthesis of valuable chemicals and pharmaceuticals"
Most read news
Microbes could help reduce the need for chemical fertilizers
A coating protects nitrogen-fixing bacteria: Start-up to commercialise coated bacteria for large-scale use in regenerative agriculture
Inauguration of the world’s first pilot plant for the cost-efficient production of green methanol
Start-up C1 Green Chemicals AG and research partners develop fundamentally new production process
This is a battery
Two colored liquids bubbling through tubes: Is this what the battery of the future looks like?
Not so silver lining: Microplastics found in clouds could affect the weather
Low-altitude and denser clouds contained greater amounts of microplastics
New designs for solid-state electrolytes may soon revolutionize the battery industry
Scientists achieve monumental improvements in lithium-metal-chloride solid-state electrolytes
Converting PFAS “forever chemicals” into valuable compounds
Scientists develop a new method to incorporate harmful perfluoroalkenes into N-heterocyclic carbene ligands
Graphene's proton permeability: A switch for future energy technologies
This discovery could lead to the development of more efficient hydrogen fuel cells and solar water-splitting devices
Lithium-ion batteries are no longer the gold standard in battery tech
On the way to safer and more powerful energy sources
Vulcan officially opened its Lithium Extraction Optimisation Plant
Europe’s first plant for fully domestic lithium chemicals production, to secure Europe’s lithium supply chain for Battery Electric Vehicle manufacturers
CO2-free hydrogen: BASF receives funding approval for 54-megawatt water electrolysis plant
Proton exchange membrane (PEM) electrolyzer expected to produce up to 8,000 metric tons of hydrogen per year
More news from our other portals
New drug delivery system could reduce daily diabetes shots to just three a year
Dietary management drugs have transformed Type 2 diabetes care, but daily injection routines are challenging for some patients
Dunning-Kruger effect with muesli bars
Those who know the least consider themselves highly competent
Aston University technology to combat the not-so sweet practice of honey fraud
Light technology to be used to detect if honey is blended with cheap additions
Naked Clams: The New Superfood Sensation Emerging from the Depths
Researchers found Naked Clams contain almost twice the amount of Vitamin B12 as blue mussels and have developed an efficient way to farm them
Scientists use quantum biology, AI to sharpen genome editing tool
"This study represents an exciting advancement toward, understanding how we can avoid making costly ‘typos’ in an organism’s genetic code"
How stem cells and immune cells communicate
Lisec Artz Award for Simon Haas: Groundbreaking discovery of an unknown protective mechanism against blood cancer from stem cells
Fatty acid factory filmed at work
High-resolution images provide new insights into cellular fatty acid production: Potential for medicine and biotechnology
Pushers, overcrowded trains and phone zombies
Sprite presents the world's first vending machine that responds to the things that bother Generation Z the most
‘Hot’ new form of microscopy examines materials using evanescent waves
“This microscope technology is completely new, so we’re still learning specifically how and where it can be applied”
Tönnies Group launches first nationwide "Meat Climate Platform"
100 guests at the Future Forum for Agriculture
Award for innovation in the detection of PFAS compounds
Thuringian startup and Fraunhofer Institute receive Lothar Späth Award
From the trough to the plate - digitally calculated
Computer program "ConTrans" estimates how much of an undesirable substance is transferred from animal feed to food
analytica 2024: Food analysis for sustainable nutrition
From PFAS to microplastics: focus on new harmful substances
The Largest Biotech City in Europe Will Soon Be Built
The entire BIO CITY complex will span an area equivalent to 10 football fields, total investment expected to reach around 7 billion euros
Could eating turkey ease colitis?
According to data in mice, extra tryptophan could reduce the risk of future colitis flares
Breakthrough in the synthesis of artificial cells
Researchers develop artificial cells from synthetic materials
Are healthy foods automatically sustainable, too?
Perceptions about sustainability and healthy food choices are closely linked
The weight of pollution: exposure linked to obesity
Chronic exposure to environmental pollutants found to increase risk of cardiovascular disease