New understanding of complex catalysis advances catalyst design

Date:
February 24, 2022
Source:
Harvard John A. Paulson School of Engineering and Applied Sciences
Summary:
Understanding the reaction pathways and kinetics of catalytic
reactions at the atomic scale is critical to designing catalysts
for more energy- efficient and sustainable chemical production,
especially multimaterial catalysts that have ever-changing surface
structures. Researchers have now peered into the black box to
understand the evolving structures in a multimaterial catalyst at
the atomic scale.



FULL STORY ==========================================================================
Many of the catalytic reactions that drive our modern world happen in
an atomic black box. Scientists know all the components that go into a reaction, but not how they interact at an atomic level.


========================================================================== Understanding the reaction pathways and kinetics of catalytic
reactions at the atomic scale is critical to designing catalysts for
more energy-efficient and sustainable chemical production, especially multimaterial catalysts that have ever-changing surface structures.

In a recent paper, researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS), in collaboration with researchers
from Stony Brook University, University of Pennsylvania, University of California, Los Angeles, Columbia University, and University of Florida,
have peered into the black box to understand, for the first time, the
evolving structures in a multimaterial catalyst at the atomic scale.

The research was done as part of the Integrated Mesoscale Architectures
for Sustainable Catalysis (IMASC), an Energy Frontier Research Center
funded by the Department of Energy, headquartered at Harvard. It was
published in Nature Communications.

"Our multipronged strategy combines reactivity measurements, machine
learning- enabled spectroscopic analysis, and kinetic modeling to
resolve a long-standing challenge in the field of catalysis -- how do we understand the reactive structures in complex and dynamic alloy catalysts
at the atomic level," said Boris Kozinsky, the Thomas D. Cabot Associate Professor of Computational Materials Science at SEAS and co-corresponding author of the paper. "This research allows us to advance catalyst design
beyond the trial-and-error approach." The team used a multimaterial
catalyst containing small clusters of palladium atoms mixed with larger concentrations of gold atoms in particles approximately five nanometers
in diameter. In these catalysts, the chemical reaction takes place on the surface of tiny islands of palladium. This class of catalyst is promising because it is highly active and selective for many chemical reactions
but it's difficult to observe because the clusters of palladium consist
of only a few atoms.

"Three-dimensional structure and composition of the active palladium
clusters cannot be determined directly by imaging because the experimental tools available to us do not provide sufficient resolution," said Anatoly Frenkel, professor of Materials Science and Chemical Engineering at Stony
Brook and co- corresponding author of the paper. "Instead, we trained an artificial neural network to find the attributes of such a structure,
such as the number of bonds and their types, from the x-ray spectrum
that is sensitive to them." The researchers used x-ray spectroscopy and machine learning analysis to narrow down potential atomic structures,
then used first principles calculations to model reactions based on
those structures, finding the atomic structures that would result in
the observed catalytic reaction.

"We found a way to co-refine a structure model with input from
experimental characterization and theoretical reaction modeling, where
both riff off each other in a feedback loop," said Nicholas Marcella,
a recent PhD from Stony Brook's Department of Materials Science and
Chemical Engineering, a postdoc at University of Illinois, and the first
author of the paper.

"Our multidisciplinary approach considerably narrows down the large configurational space to enable precise identification of the active site
and can be applied to more complex reactions," said Kozinsky. "It brings
us one step closer to achieving more energy-efficient and sustainable
catalytic processes for a range of applications, from manufacturing of materials to environmental protection to the pharmaceutical industry."
The research was co-authored by Jin Soo Lim, Anna M. P?onka, George
Yan, Cameron J. Owen, Jessi E. S. van der Hoeven, Alexandre C. Foucher,
Hio Tong Ngan, Steven B. Torrisi, Nebojsa S. Marinkovic, Eric A. Stach,
Jason F. Weaver, Joanna Aizenberg and Philippe Sautet. It was supported
in part by the US Department of Energy, Office of Science, Office of
Basic Energy Sciences under Award No. DE-SC0012573.

========================================================================== Story Source: Materials provided
by Harvard_John_A._Paulson_School_of_Engineering_and_Applied
Sciences. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Nicholas Marcella, Jin Soo Lim, Anna M. Płonka, George Yan,
Cameron
J. Owen, Jessi E. S. van der Hoeven, Alexandre C. Foucher, Hio
Tong Ngan, Steven B. Torrisi, Nebojsa S. Marinkovic, Eric A. Stach,
Jason F. Weaver, Joanna Aizenberg, Philippe Sautet, Boris Kozinsky,
Anatoly I. Frenkel.

Decoding reactive structures in dilute alloy catalysts. Nature
Communications, 2022; 13 (1) DOI: 10.1038/s41467-022-28366-w ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220224180335.htm

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