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)