Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Mysterious catalyst explained: how tiny gold particles aid the production of plastic components

30.04.2013
RUB researchers report in “Angewandte Chemie”

From methanol to formaldehyde - this reaction is the starting point for the synthesis of many everyday plastics. Using catalysts made of gold particles, formaldehyde could be produced without the environmentally hazardous waste generated in conventional methods.


Gold/titanium dioxide catalyst in action: At the interface between a gold particle (Au, gold) and the titanium dioxide surface (TiO2, red and light blue), an oxygen molecule (O2, dark blue spheres) is activated by a charge transfer and becomes catalytically active. Thus, methanol (CH3OH) can be efficiently and selectively oxidized to formaldehyde (CH2O); water (H2O) is produced as well. The researchers made the charge transfer visible using vibrational spectroscopy of adsorbed carbon monoxide (CO; middle of the figure): In the presence of oxygen, a new band (CO@Au(delta+)O2(delta-) appears in the spectrum.
Image: M. Farnesi Camellone, D. Marx

Just how the mysterious gold catalyst works has been found out by theoretical and experimental researchers at the Ruhr-Universität Bochum in a cooperation project. In the international edition of the journal “Angewandte Chemie” they report in detail on what happens on the gold surface during the chemical reaction.

“Gold should not really be suitable as a catalyst.”

“That nanoparticles of gold actually selectively transform methanol into formaldehyde is remarkable”, says Prof. Dr. Martin Muhler of the Laboratory of Industrial Chemistry at the RUB. “As a stable precious metal, gold should not really be suitable as a catalyst.” However, gold particles of a few nanometres in size, anchored to a titanium dioxide surface, fulfil their purpose. You only need oxygen to set the reaction in motion, and the only waste product is water. How this is achieved is examined by Muhler’s team together with the groups of Prof. Dr. Dominik Marx of the Chair of Theoretical Chemistry and Dr. Yuemin Wang of the Department of Physical Chemistry I.

Oxygen binds at the interface between gold and titanium dioxide

The chemists identified the active site of the catalyst, i.e. the point at which the oxygen and methanol bind and are converted to water and formaldehyde. Elaborate calculations by Dr. Matteo Farnesi Camellone showed that oxygen binds at the interface between titanium dioxide and gold particles. Since titanium dioxide is a semiconductor, and thus electrically conductive, a charge exchange between oxygen, gold particles and titanium dioxide is possible here. Oxygen vacancies in the titanium dioxide further favour this charge transfer. Electrons transitionally transfer from the catalyst to the oxygen molecule. This allows the methanol to bind to the gold particles. In several further reaction steps, formaldehyde and water form. The solid, which consists of gold and titanium dioxide, is in the same state at the end of the reaction cycle as at the beginning, and is thus not consumed.

Experiment and theory: only the combination makes it possible

The RUB team clarified the individual reaction steps in detail. The researchers used computer simulations, so-called density functional calculations, and various spectroscopic techniques, namely, vibrational spectroscopy (HREELS method) and thermal desorption spectroscopy. In his model calculations, Dr. Farnesi quantified the charge exchange taking place during catalysis. Extremely sensitive vibrational spectroscopic measurements by Dr. Wang’s group confirmed the consequences of the charge transfer in the real system. “Through an intensive cooperation between theory and experiment, we have been able to qualitatively and quantitatively explore the active site and the entire reaction mechanism of this complex catalyst”, stresses Prof. Marx.

Funding

The study originates from the Collaborative Research Centre 558 “Metal-substrate interactions in heterogeneous catalysis”, which ended mid-2012. “The results are, so to speak, the crowning glory of the SFB works on alcohol oxidation”, Muhler sums up. The project was further actively funded by the Cluster of Excellence “Ruhr Explores Solvation” RESOLV (EXC 1069), approved by the German Research Foundation (DFG) in 2012, in which researchers investigate the selective oxidation of alcohols in the liquid phase.

Bibliographic record

M. Farnesi Camellone, J. Zhao, L. Jin, Y. Wang, M. Muhler, D. Marx (2013): Molecular understanding of reactivity and selectivity for methanol oxidation at the Au/TiO2 interface, Angewandte Chemie International Edition, DOI: 10.1002/anie.201301868

Further information

Prof. Dr. Martin Muhler, Laboratory of Industrial Chemistry, Faculty of Chemistry and Biochemistry at the Ruhr-Universität, 44780 Bochum, Germany, Tel. +49/234/32-28754, E-mail: muhler@techem.rub.de

Prof. Dr. Dominik Marx, Chair of Theoretical Chemistry, Faculty of Chemistry and Biochemistry at the Ruhr-Universität, 44780 Bochum, Germany, Tel. +49/234/32-28083, E-mail: dominik.marx@theochem.rub.de

Further press releases on this topic
http://aktuell.ruhr-uni-bochum.de/pm2013/pm00053.html.en

Editor: Dr. Julia Weiler

Dr. Josef König | idw
Further information:
http://aktuell.ruhr-uni-bochum.de/pm2013/pm00053.html.en

More articles from Life Sciences:

nachricht Transport of molecular motors into cilia
28.03.2017 | Aarhus University

nachricht Asian dust providing key nutrients for California's giant sequoias
28.03.2017 | University of California - Riverside

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: A Challenging European Research Project to Develop New Tiny Microscopes

The Institute of Semiconductor Technology and the Institute of Physical and Theoretical Chemistry, both members of the Laboratory for Emerging Nanometrology (LENA), at Technische Universität Braunschweig are partners in a new European research project entitled ChipScope, which aims to develop a completely new and extremely small optical microscope capable of observing the interior of living cells in real time. A consortium of 7 partners from 5 countries will tackle this issue with very ambitious objectives during a four-year research program.

To demonstrate the usefulness of this new scientific tool, at the end of the project the developed chip-sized microscope will be used to observe in real-time...

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...

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

Periodic ventilation keeps more pollen out than tilted-open windows

29.03.2017 | Health and Medicine

Researchers discover dust plays prominent role in nutrients of mountain forest ecoystems

29.03.2017 | Earth Sciences

OLED production facility from a single source

29.03.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>