Scientists can now locate oxygen in the structure of catalysts with a precision of one-trillionth of a meter
A major new application of Dynamic
Nuclear Polarization NMR technology at the U.S. Department of Energy’s Ames
Laboratory has led to the ability to examine the chemical structure of
catalysts with a spatial resolution of less than a picometer, or one-trillionth
of a meter. That capability enables scientists to better understand, and design
more effective catalysts for the production of fuels and high value chemicals. In
this study, researchers were able to measure the length of O-H bonds on
catalytic surfaces structures, and correlate these bond lengths to the relative
acidity of the material.
In conventional Nuclear Magnetic
Resonance (NMR) technology, researchers can acquire physical and chemical
information about materials they are investigating based on the way atomic
nuclei in the sample interact with a strong magnetic field. With Ames
Laboratory’s Dynamic Nuclear Polarization NMR (DNP-NMR) spectrometer, which is
uniquely suited to materials chemistry research, microwaves are used to
polarize the electrons, which subsequently excite the nuclei of the sample
being analyzed. Paired with innovative experimental techniques, what results is
a highly sensitive reading of the sample, orders of magnitude faster than
traditional NMR methods.
“Conventional solid-state NMR can, in
principle, elucidate the structure of materials with atomic scale precision.
However, NMR’s fundamental lack of sensitivity often challenges its
applications to surfaces and interfaces, and that’s where catalysis actually
happens,” said Marek Pruski, Ames Laboratory senior scientist and the principal
investigator of the research team. “This is where DNP-NMR comes in. With its
enhanced signal, it provides a unique analytical tool to determine the
seemingly minute differences in materials’ structure which often determine
their performance.”
The discovery is part of a larger scope
of research, using a difficult-to-measure isotope of oxygen, 17O, to
analyze materials with DNP-NMR. “It’s the only isotope of oxygen that is measurable
by NMR, but unfortunately its natural abundance is prohibitively low,” said
Frederic Perras, postdoctoral fellow. “That meant enriching your samples with
expensive 17O isotopes--which is sometimes very difficult-- was mandatory.
DNP-NMR provides a new avenue for doing 17O NMR, without isotope enrichment.”
Read more at: https://www.ameslab.gov/news/news-releases/scientists-can-now-locate-oxygen-in-the-structure-catalysts-precision-one
Source: Ameslab