Mar
15
Seeing a Catalytic Chemical Reaction in Real Time
March 15, 2013 | Leave a Comment
The SLAC used LCLS, together with computerized simulations, to reveal surprising details of a short-lived early state in a chemical reaction occurring at the surface of a catalyst sample. The study offers important clues about how catalysts work and launches a new era in probing surface chemistry as it happens.
This news is a breakthrough even though it will take years for the effect to be felt. Understanding catalytic processes at the atomic level will open many doors and solve a wide array of problems.
SLAC Surface Chemical Reaction Diagram. How LCLS views surface chemistry Image Credit: Hirohito Ogasawara at SLAC National Accelerator Laboratory. Click image for the largest view.
Anders Nilsson, deputy director for the Stanford and SLAC SUNCAT Center for Interface Science and Catalysis and a leading author in the research, published March 15th in Science said, “To study a reaction like this in real time is a chemist’s dream. We are really jumping into the unknown.”
Catalysts can speed up chemical reactions and make them more efficient and effective. They are essential to most industrial processes and to the production of many chemicals and compounds. The familiar catalytic converter in cars, for example, reduces emissions by converting exhaust chemicals to less toxic compounds.
Nilsson explains that understanding how catalysts work at ultrafast time scales and with molecular precision is essential to producing new, lower-cost synthetic fuels and alternative energy sources that reduce pollution.
In the LCLS experiment researchers looked at a catalyst that has been extensively studied, the simple reaction in a crystal composed of ruthenium in reaction with carbon monoxide gas. The scientists zapped the crystal’s surface with a conventional laser that caused carbon monoxide molecules to begin to break away. They then probed this state of the reaction using X-ray laser pulses, and observed that the molecules were temporarily trapped in a near-gas state and still interacting with the catalyst.
“We never expected to see this state. It was a surprise,” Nilsson said.
Not only was the experiment the first to confirm the details of this early stage of the reaction, it also found an unexpectedly high share of molecules trapped in this state for far longer than what was anticipated, raising new questions about the atomic-scale interplay of chemicals that will be explored in future research.
Understanding the time involved in catalyst reactions is critical to process engineering. Jens Nørskov, director of SUNCAT pointed out some of the early stages of a chemical reaction are so rapid that they could not be observed until the creation of free-electron lasers such as LCLS. Future experiments at LCLS will examine more complex reactions and materials, Nilsson said: “There is potential to probe a number of catalytic-relevant processes – you can imagine there are tons of things we could do from here,” he said.
On background Hirohito Ogasawara, a staff scientist at SSRL explained important preliminary research was conducted at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), and this direct coupling of research at SLAC’s synchrotron and X-ray laser proved essential.
Credit for the collaborators participating in the research goes to SLAC; Stanford University; University of Hamburg, Center for Free-Electron Laser Science, Helmholtz-Zentrum Berlin for Materials and Energy, University of Potsdam and Fritz-Haber Institute of the Max Planck Society in Germany; Stockholm University in Sweden; and the Technical University of Denmark.
The work was supported by DOE’s Office of Science, the Swedish National Research Council, and the Danish Center for Scientific Computing, the Volkswagen Foundation and the Lundbeck Foundation.
The importance of understanding catalytic processes at the atomic level cannot be overstated. Much of the chemistry that modern life relies on has been serendipitous or discovered in the Edison experimentation method of wide ranging tests.
Without knowing what is taking place chemistry would be forever stuck into developing from the known reactions. Knowing will provide the basis for designing reactions.
That will be the revolution.
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