Navigation Links
When water speaks
Date:2/21/2013

Why certain catalyst materials work more efficiently when they are surrounded by water instead of a gas phase is unclear. RUB chemists have now gleamed some initial answers from computer simulations. They showed that water stabilises specific charge states on the catalyst surface. "The catalyst and the water sort of speak with each other" says Professor Dominik Marx, depicting the underlying complex charge transfer processes. His research group from the Centre for Theoretical Chemistry also calculated how to increase the efficiency of catalytic systems without water by varying pressure and temperature. The researchers describe the results in the journals "Physical Review Letters" and "Journal of Physical Chemistry Letters."

Heterogeneous catalysis: water or gas as the second phase

In heterogeneous catalysis, researchers combine substances with two different phases - usually solid and gas. Chemical reactions work faster at the resulting interfaces than without a catalyst. Industry uses heterogeneous catalysis for many processes, for example to transform alcohols into certain aldehydes. Titanium dioxide with gold particles bonded to the surface, for example, is suitable as the solid phase. Water - instead of a gas - as the second phase has several advantages: environmentally harmful substances which are required in traditional procedures for the oxidation of alcohols can easily be replaced by atmospheric oxygen. Also, the whole reaction in water is very efficient, even at moderate temperatures.

Charge transfer between water and catalyst

The theoretical chemists have studied what happens in the catalysis at the molecular level by means of so-called ab initio molecular dynamics simulations. The result: a charge transfer takes place between the water and the catalyst. Electrons, or more specifically portions of electron densities, are moved between the solid and the liquid phase. The researchers speculate that in this way the liquid phase stabilises charge states on the gold surface. The sites where this occurs could be the active centres of the catalyst, where the chemical reactions work efficiently. Unlike water, a gas phase is not able to "talk" to the catalyst in this way, because no charge transfer is possible with the gas phase.

Increasing the efficiency through thermodynamics

In a further study, the team led by Dominik Marx examined a related metal/oxide catalyst of copper and zinc oxide, which is used for the large-scale industrial synthesis of methanol. As the computer simulations showed, especially the interplay between the solid phase and the gas phase is important here for the efficiency. Depending on the pressure and temperature conditions, hydrogen binds to the catalyst surface and thus indirectly stabilises catalytically active centres that occur in this case due to an electron transfer between the metal and the oxide. "Without the hydrogen, put bluntly the centres would not exist", says Marx. In this way, the thermodynamic conditions in the gas phase put the surface into a certain state which is particularly favourable for the work of the catalyst.

Added value through combination

The two studies thus show that the catalytic efficiency can be controlled both by a solvent and by thermodynamics namely through the pressure and temperature of the gas phase. However, completely different mechanisms are responsible for this, which the researchers were nevertheless able to elucidate using the same simulation methods. This makes the results directly comparable. In this way, the theorists aim to study in future whether they can improve the copper/zinc oxide system even further by replacing the gas phase with a suitable solvent.


'/>"/>

Contact: Dominik Marx
dominik.marx@rub.de
49-234-322-8083
Ruhr-University Bochum
Source:Eurekalert

Related biology news :

1. Ozone treated water v. lethal microbial material
2. Unexpected crustacean diversity discovered in northern freshwater ecosystems
3. New methods for better purification of wastewater
4. Costs for changing pollution criteria in Florida waters likely to exceed EPA estimates
5. Current water resources in Europe and Africa
6. UC research: Tracking Lake Erie water snake in fight against invasive fish
7. Study confirms oil from Deepwater Horizon disaster entered food chain in the Gulf of Mexico
8. Specialization for underwater hearing by the tympanic middle ear of the turtle
9. Study by Haverford College professor reveals unprecedented impact of Deepwater Horizon on deep ocean
10. Increasing water scarcity in Californias Bay-Delta will necessitate trade-offs; hard decisions needed to balance various environmental risks
11. Scientists study the catalytic reactions used by plants to split oxygen from water
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:6/22/2016)... 22, 2016   Acuant , the ... solutions, has partnered with RightCrowd ® ... Visitor Management, Self-Service Kiosks and Continuous Workforce ... add functional enhancements to existing physical access ... venues with an automated ID verification and ...
(Date:6/20/2016)... 20, 2016 Securus Technologies, a leading ... for public safety, investigation, corrections and monitoring announced ... it has secured the final acceptance by all ... Managed Access Systems (MAS) installed. Furthermore, Securus will ... be installed by October, 2016. MAS distinguishes between ...
(Date:6/9/2016)... June 9, 2016  Perkotek an innovation leader in attendance control systems is proud ... work hours, for employers to make sure the right employees are actually signing in, ... ... ... ...
Breaking Biology News(10 mins):
(Date:6/27/2016)... , June 27, 2016 /PRNewswire/ - BIOREM Inc. (TSX-V: BRM) ... advised by its major shareholders, Clean Technology Fund I, ... United States based venture capital funds which ... Biorem (on a fully diluted, as converted basis), that ... of their entire equity holdings in Biorem to TUS ...
(Date:6/27/2016)... ... June 27, 2016 , ... Cancer experts ... they believe could be a new and helpful biomarker for malignant pleural mesothelioma. ... here to read it now. , Biomarkers are components in the blood, ...
(Date:6/27/2016)... ... 2016 , ... Newly created 4Sight Medical Solutions ... healthcare market. The company's primary focus is on new product introductions, to include ... are necessary to help companies efficiently bring their products to market. , The ...
(Date:6/27/2016)... , June 27, 2016  Liquid Biotech ... the funding of a Sponsored Research Agreement with ... tumor cells (CTCs) from cancer patients.  The funding ... CTC levels correlate with clinical outcomes in cancer ... data will then be employed to support the ...
Breaking Biology Technology: