Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Lonely Atoms, Happily Reunited

26.07.2016

The remarkable behaviour of platinum atoms on magnetite surfaces could lead to better catalysts. Scientists at TU Wien (Vienna) can now explain how platinum atoms can form pairs with the help of carbon monoxide.

At first glance, magnetite appears to be a rather inconspicuous grey mineral. But on an atomic scale, it has remarkable properties: on magnetite, single metal atoms are held in place, or they can be made to move across the surface.


Two platinum atoms on the magnetite surface can bond, if they are attached to CO molecules.

TU Wien


Experiments in the vacuum chamber at TU Wien.

TU Wien

Sometimes several metal atoms on magnetite form small clusters. Such phenomena can dramatically change the chemical activity of the material. Atomic processes on the magnetite surface determine how well certain metal atoms can serve as catalysts for chemical reactions.

Scientists at TU Wien (Vienna), together with colleagues from Utrecht University, can now watch single platinum atoms form tiny clusters. Carbon monoxide plays a dual role in this process: It allows single platinum atoms to move and form pairs, and then it holds these pairs together for a long time. Only by increasing the temperature can the pair-bonds between platinum atoms can be broken.

Lonely Atoms

It sounds a bit like an unhappy love story: “Two platinum atoms would actually like to be together, but the magnetite surface keeps them apart”, says Roland Bliem (TU Wien). Together with Professor Gareth Parkinson, Professor Ulrike Diebold and their colleagues, he analysed the behaviour of platinum atoms using a scanning tunnelling microscope.

“When a platinum atom hits the magnetite surface, it is kept in place by the oxygen atoms in the magnetite. The atoms always end up alone. On other surfaces, pair formation would be favoured, but magnetite does not allow that”, says Roland Bliem. The platinum atoms sit on specific places on the magnetite crystal and cannot get away without outside help.

However, with the appearance of carbon monoxide, the situation changes completely: “A carbon monoxide molecule can attach to a platinum atom and lift it up”, says Gareth Parkinson. “We call that the skyhook effect.” The lifting process frees the atom from the tight grip of the magnetite, and together, the molecule and the platinum atom can start moving around randomly across the magnetite surface.

When one mobilized platinum atom finds another, they can form a bond – as long as both of them are being lifted up by carbon monoxide, diminishing the influence of the magnetite below.

When the temperature is increased to 250°C, the carbon monoxide separates from the platinum atom and the bond breaks up. The two platinum atoms must once again find separate places on the magnetite surface. This effect opens up a strategy to turn clusters into single atoms – an important process in so called “single-atom catalysts”. Sometimes clusters of several atoms are formed. These larger clusters, however, cannot be broken up, even at high temperatures.

Movies with Atomic Resolution

“In our scanning tunnelling microscope, we can image the same part of the surface again and again, so that we can create a movie, showing the dancing atoms”, says Roland Bliem. “This is crucial for understanding what really happens on the magnetite surface. We can watch single atoms as they wander across the magnetite surface or bond with each other.

If we only had a picture of the end result, we could not say with certainty, whether one specific structure consists of one, two or more atoms. Only by following the time evolution of the atomic motion, we know which interpretation is correct.” Bliem did not only conduct the experiments, he also performed complex theoretical calculations to explain the peculiar behaviour of the platinum atoms on a quantum mechanical level.

For chemical catalysis, such findings play an important role. “Metals such as platinum are frequently used as catalysts”, says Gareth Parkinson. “But a large cluster of many metal atoms may have completely different chemical properties than single metal atoms sitting separately on a surface. When we want to optimize catalysts, so we must be able to understand and control the behaviour of the atoms. This work is one step further towards that goal.”

Photo download: https://www.tuwien.ac.at/dle/pr/aktuelles/downloads/2016/magnetit

Roland Bliema, Jessi E. S. van der Hoevenb, Jan Hulvaa, Jiri Paveleca, Oscar Gambaa, Petra E. de Jonghb, Michael Schmida, Peter Blahac, Ulrike Diebolda, and Gareth S. Parkinson (2016). "Dual role of CO in the stability of subnano Pt clusters at the Fe3O4(001) surface". PNAS: http://www.pnas.org/content/early/2016/07/22/1605649113.abstract

Further information:

Dipl.-Ing. Roland Bliem
Institute of Applied Physics
TU Wien (Vienna)
Wiedner Hauptstraße 8-10, 1040 Vienna
T: +43-1-58801-13466
roland.bliem@tuwien.ac.at

Gareth Parkinson, PhD
Institute of Applied Physics
TU Wien (Vienna)
Wiedner Hauptstraße 8-10, 1040 Vienna
T: +43-1-58801-13473
gareth.parkinson@tuwien.ac.at

Weitere Informationen:

https://www.tuwien.ac.at/dle/pr/aktuelles/downloads/2016/magnetit
http://www.pnas.org/content/early/2016/07/22/1605649113.abstract

Dr. Florian Aigner | Technische Universität Wien

More articles from Physics and Astronomy:

nachricht Astronomers find unexpected, dust-obscured star formation in distant galaxy
24.03.2017 | University of Massachusetts at Amherst

nachricht Gravitational wave kicks monster black hole out of galactic core
24.03.2017 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Giant Magnetic Fields in the Universe

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), hot gas, and charged particles, they found magnetic fields that are exceptionally ordered over distances of many million light years. This makes them the most extended magnetic fields in the universe known so far.

The results will be published on March 22 in the journal „Astronomy & Astrophysics“.

Galaxy clusters are the largest gravitationally bound structures in the universe. With a typical extent of about 10 million light years, i.e. 100 times the...

Im Focus: Tracing down linear ubiquitination

Researchers at the Goethe University Frankfurt, together with partners from the University of Tübingen in Germany and Queen Mary University as well as Francis Crick Institute from London (UK) have developed a novel technology to decipher the secret ubiquitin code.

Ubiquitin is a small protein that can be linked to other cellular proteins, thereby controlling and modulating their functions. The attachment occurs in many...

Im Focus: Perovskite edges can be tuned for optoelectronic performance

Layered 2D material improves efficiency for solar cells and LEDs

In the eternal search for next generation high-efficiency solar cells and LEDs, scientists at Los Alamos National Laboratory and their partners are creating...

Im Focus: Polymer-coated silicon nanosheets as alternative to graphene: A perfect team for nanoelectronics

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are less stable. Now researchers at the Technical University of Munich (TUM) have, for the first time ever, produced a composite material combining silicon nanosheets and a polymer that is both UV-resistant and easy to process. This brings the scientists a significant step closer to industrial applications like flexible displays and photosensors.

Silicon nanosheets are thin, two-dimensional layers with exceptional optoelectronic properties very similar to those of graphene. Albeit, the nanosheets are...

Im Focus: Researchers Imitate Molecular Crowding in Cells

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to simulate these confined natural conditions in artificial vesicles for the first time. As reported in the academic journal Small, the results are offering better insight into the development of nanoreactors and artificial organelles.

Enzymes behave differently in a test tube compared with the molecular scrum of a living cell. Chemists from the University of Basel have now been able to...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

International Land Use Symposium ILUS 2017: Call for Abstracts and Registration open

20.03.2017 | Event News

CONNECT 2017: International congress on connective tissue

14.03.2017 | Event News

ICTM Conference: Turbine Construction between Big Data and Additive Manufacturing

07.03.2017 | Event News

 
Latest News

Northern oceans pumped CO2 into the atmosphere

27.03.2017 | Earth Sciences

Fingerprint' technique spots frog populations at risk from pollution

27.03.2017 | Life Sciences

Big data approach to predict protein structure

27.03.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>