Details of a crucial reaction: Physicists uncover oxidation process of carbon monoxide on a ruthenium surface
This illustrates a moment captured for the first time in experiments at SLAC National Accelerator Laboratory. The CO-molecule and oxygen-atoms are attached to the surface of a ruthenium catalyst. When hit with an optical laser pulse, the reactants vibrate and bump into each other and the carbon atom forms a transitional bond with the lone oxygen center. The resulting CO2 detaches and floats away. © SLAC National Accelerator Laboratory
An international team has observed the elusive intermediates that form when carbon monoxide is oxidized on a hot ruthenium metal surface. They used ultrafast X-ray and optical laser pulses at the SLAC National Accelerator Laboratory, Menlo Park, California. The reaction between carbon monoxide and adsorbed oxygen atoms was initiated by heating the ruthenium surface with optical laser pulses. Directly afterwards, changes in the electronic structure of oxygen atoms were probed via X-ray absorption spectroscopy as they formed bonds with the carbon atoms.The observed transition states are consistent with density functional theory and quantum oscillator models.
The researchers were surprised to see so many of the reactants enter the transition state - and equally surprised to discover that only a small fraction of them go on to form stable carbon dioxide. The rest break apart again. "It's as if you are rolling marbles up a hill, and most of the marbles that make it to the top roll back down again," says Anders Nilsson, professor at the SLAC/Stanford SUNCAT Center for Interface Science and Catalysis and at Stockholm University, who led the research.
A team from the Institute of Methods and Instrumentation in Synchrotron Radiation Research from HZB has contributed in this research activities at SLAC sponsored by the Volkswagen-Foundation and the Helmholtz Virtual Institute “Dynamic Pathways in Multidimensional Landscapes” in which HZB and SLAC collaborate.
“These results help us to understand a really crucial reaction with high relevance for instance for environmental issues and to see which role catalysts may play”, Martin Beye of the HZB Team explains.
See full press release at SLAC-Website
Citation: H. Öström et al., Science, 12 February 2015 (10.1126/science.1261747)
- Stability of perovskite solar cells reaches next milestonePerovskite semiconductors promise highly efficient and low-cost solar cells. However, the semi-organic material is very sensitive to temperature differences, which can quickly lead to fatigue damage in normal outdoor use. Adding a dipolar polymer compound to the precursor perovskite solution helps to counteract this. This has now been shown in a study published in the journal Science by an international team led by Antonio Abate, HZB. The solar cells produced in this way achieve efficiencies of well above 24 %, which hardly drop under rapid temperature fluctuations between -60 and +80 Celsius over one hundred cycles. That corresponds to about one year of outdoor use.
- HZB physicist appointed to Gangneung-Wonju National University, South KoreaSince 2016, accelerator physicist Ji-Gwang Hwang has been working at HZB in the department of storage rings and beam physics. He has made important contributions to beam diagnostics in several projects at HZB. He is now returning to his home country, South Korea, having accepted a professorship in physics at Gangneung-Wonju National University.
- Scientists Develop New Technique to Image Fluctuations in MaterialsA team of scientists, led by researchers from the Max Born Institute in Berlin and Helmholtz-Zentrum Berlin in Germany and from Brookhaven National Laboratory and the Massachusetts Institute of Technology in the United States has developed a revolutionary new method for capturing high-resolution images of fluctuations in materials at the nanoscale using powerful X-ray sources. The technique, which they call Coherent Correlation Imaging (CCI), allows for the creation of sharp, detailed movies without damaging the sample by excessive radiation. By using an algorithm to detect patterns in underexposed images, CCI opens paths to previously inaccessible information. The team demonstrated CCI on samples made of thin magnetic layers, and their results have been published in Nature.