Catalysis by gold has received considerable attention in recent years. Particles of gold have been reported to be very active in various oxidation reactions. The particle size greatly influences the catalytic activity of gold particles and with decreasing particle size, the activity increases. Moreover, the type of support also affects the catalytic activity. One example of a reaction with gold catalysts is the CO oxidation in presence or absence of hydrogen, which is relevant for the use of hydrogen in fuel cells. Regarding the mechanism, one of the main questions is how oxygen is activated on the catalyst. Jeroen A. van Bokhoven of ETH Zurich's Institute for Chemical and Bio-Engineering and colleagues at the ESRF, Grenoble, and the University of Southampton have now identified a possible reaction mechanism for the oxidation of CO over the gold particles in supported gold catalysts. The research results have been published in "Angewandte Chemie".
How gold activates the oxygen
The researchers studied gold supported on the nonreducible support Al2O3 and observed a reaction channel that has partially oxidized gold as reaction intermediate. Charge transfer from a reduced gold particle to oxygen activates the oxygen molecule. The researchers propose that reduced gold in small particles has the unique ability to transfer electrons to oxygen. A small fraction of the surface atoms are oxidized and are essential for high catalytic activity for oxidation of CO. The thermodynamic redox behaviour of small gold particles is distinctly different from that of bulk gold, which is inert. The difference likely originates from the different electronic properties of the small gold particles, which contain a large fraction of coordinatively unsaturated atoms with corner and edge positions. The latter have more d-electrons, which are additionally shifted towards the Fermi-level, than atoms in bulk gold. The electronic changes in nano-particles lead to stronger metal-adsorbate bonding and higher reactivity. Exposure of the gold-activated oxygen to CO rapidly forms CO2 and with re-reduction to metallic gold completing the catalytic cycle. Kinetic analysis of the individual reaction steps indicates that reduction is much faster than the re-oxidation and the rate-limiting step is the activation of oxygen on the gold surface.
Valuable tool in determining the structures of catalysts
For their experiments Jeroen A. van Bokhoven and colleagues combined in-situ time-resolved and in-situ high energy-resolution fluorescence detected X-ray spectroscopy. This method is likely to become a valuable tool in determining the structures of catalysts under catalytically relevant conditions. Combining high energy-resolution data with time-resolution and the possibility of in-situ measurement in combination with mass spectrometry at synchrotrons make it a promising tool in determining the structures of catalytically active sites.Further information
Climate Impact Research in Hannover: Small Plants against Large Waves
17.08.2018 | Leibniz Universität Hannover
First transcription atlas of all wheat genes expands prospects for research and cultivation
17.08.2018 | Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung
New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference
Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...
Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.
Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...
17.08.2018 | Event News
08.08.2018 | Event News
27.07.2018 | Event News
17.08.2018 | Physics and Astronomy
17.08.2018 | Information Technology
17.08.2018 | Life Sciences