Chemistry Department Colloquium

""Taking Snapshots of Reaction Intermediates in Metalloenzymes and Catalysts with X-ray Techniques""

Presented by Junko Tano, Ph.D., Joint Center for Artificial Photosynthesis, Lawrence Berkeley National Laboratory

Monday, September 11, 2017, 11:00 am — Hamilton Seminar Room, Bldg. 555

Our group is interested in the mechanisms of the catalytic reactions in both natural and inorganic systems. Using various X-ray techniques as tools, we are studying how the catalysts modulate and control multielectron reactions by following the reaction under functional conditions.
We have developed spectroscopy and diffraction techniques necessary to fully utilize the capability of the XFELs for a wide variety of metalloenzymes, and to study their chemistry under functional conditions. One of such methods is simultaneous data collection for X-ray crystallography and X-ray spectroscopy, to determine the overall structural changes of proteins and the chemical changes at metal catalytic sites. In parallel to the detection techniques, we have developed an efficient sample delivery method that involves deposition of droplets on a conveyor belt. This 'Droplet on Tape' (DOT) method, delivers a single drop of the crystal suspension or solution sample onto a tape, which then can be transported to the X ray intersection point with a variable delay in time. In the process, the sample is photochemically or chemically activated at various time delays to capture reaction intermediates with crystallography and spectroscopy.
In the field of inorganic catalysts, improved catalysts for electroreduction of carbon dioxide are highly important for promoting the generation of carbon-based reduction products. To gain a fundamental understanding needed to tailor novel catalysts, in particular for the selectivity of the products, the information of the early steps of the electroreduction process on catalyst surfaces is important. We have optimized and utilized surface-sensitive soft and hard X-ray techniques, including grazing incident X-ray absorption spectroscopy, X-ray diffraction, and ambient pressure X-ray photoemission spectroscopy to investigate the interaction of metal catalytic surfaces with electrolytes and/or gases (CO2 and/or H2O) under in situ/operando conditions.

Hosted by: Javier Concepcion

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