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 How brains surrender to sleep
23.06.2017 | IMP - Forschungsinstitut für Molekulare Pathologie GmbH

nachricht A new technique isolates neuronal activity during memory consolidation
22.06.2017 | Spanish National Research Council (CSIC)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>