New atomic-scale understanding of catalysis could unlock massive energy savings

Date:
April 6, 2023
Source:
University of Wisconsin-Madison
Summary:
In an advance they consider a breakthrough in computational
chemistry research, chemical engineers have developed model of how
catalytic reactions work at the atomic scale. This understanding
could allow engineers and chemists to develop more efficient
catalysts and tune industrial processes -- potentially with enormous
energy savings, given that 90% of the products we encounter in
our lives are produced, at least partially, via catalysis.


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FULL STORY ==========================================================================
In an advance they consider a breakthrough in computational chemistry
research, University of Wisconsin-Madison chemical engineers have
developed model of how catalytic reactions work at the atomic scale. This understanding could allow engineers and chemists to develop more efficient catalysts and tune industrial processes -- potentially with enormous
energy savings, given that 90% of the products we encounter in our lives
are produced, at least partially, via catalysis.


========================================================================== Catalyst materials accelerate chemical reactions without undergoing
changes themselves. They are critical for refining petroleum products and
for manufacturing pharmaceuticals, plastics, food additives, fertilizers,
green fuels, industrial chemicals and much more.

Scientists and engineers have spent decades fine-tuning catalytic
reactions - - yet because it's currently impossible to directly observe
those reactions at the extreme temperatures and pressures often involved
in industrial-scale catalysis, they haven't known exactly what is taking
place on the nano and atomic scales. This new research helps unravel
that mystery with potentially major ramifications for industry.

In fact, just three catalytic reactions -- steam-methane reforming to
produce hydrogen, ammonia synthesis to produce fertilizer, and methanol synthesis - - use close to 10% of the world's energy.

"If you decrease the temperatures at which you have to run these
reactions by only a few degrees, there will be an enormous decrease in
the energy demand that we face as humanity today," says Manos Mavrikakis,
a professor of chemical and biological engineering at UW-Madison who led
the research. "By decreasing the energy needs to run all these processes,
you are also decreasing their environmental footprint." Mavrikakis and postdoctoral researchers Lang Xu and Konstantinos G.

Papanikolaou along with graduate student Lisa Je published news of their advance in the April 7, 2023 issue of the journal Science.

In their research, the UW-Madison engineers develop and use powerful
modeling techniques to simulate catalytic reactions at the atomic
scale. For this study, they looked at reactions involving transition metal catalysts in nanoparticle form, which include elements like platinum, palladium, rhodium, copper, nickel, and others important in industry
and green energy.

According to the current rigid-surface model of catalysis, the tightly
packed atoms of transition metal catalysts provide a 2D surface that
chemical reactants adhere to and participate in reactions. When enough
pressure and heat or electricity is applied, the bonds between atoms in
the chemical reactants break, allowing the fragments to recombine into
new chemical products.

"The prevailing assumption is that these metal atoms are strongly bonded
to each other and simply provide 'landing spots' for reactants. What
everybody has assumed is that metal-metal bonds remain intact during the reactions they catalyze," says Mavrikakis. "So here, for the first time,
we asked the question, 'Could the energy to break bonds in reactants
be of similar amounts to the energy needed to disrupt bonds within
the catalyst?'" According to Mavrikakis's modeling, the answer is
yes. The energy provided for many catalytic processes to take place is
enough to break bonds and allow single metal atoms (known as adatoms)
to pop loose and start traveling on the surface of the catalyst. These
adatoms combine into clusters, which serve as sites on the catalyst
where chemical reactions can take place much easier than the original
rigid surface of the catalyst.

Using a set of special calculations, the team looked at industrially
important interactions of eight transition metal catalysts and 18
reactants, identifying energy levels and temperatures likely to form such
small metal clusters, as well as the number of atoms in each cluster,
which can also dramatically affect reaction rates.

Their experimental collaborators at the University of California,
Berkeley, used atomically-resolved scanning tunneling microscopy to look
at carbon monoxide adsorption on nickel (111), a stable, crystalline form
of nickel useful in catalysis. Their experiments confirmed models that
showed various defects in the structure of the catalyst can also influence
how single metal atoms pop loose, as well as how reaction sites form.

Mavrikakis says the new framework is challenging the foundation of how researchers understand catalysis and how it takes place. It may apply to
other non-metal catalysts as well, which he will investigate in future
work. It is also relevant to understanding other important phenomena,
including corrosion and tribology, or the interaction of surfaces
in motion.

"We're revisiting some very well-established assumptions in understanding
how catalysts work and, more generally, how molecules interact with
solids," Mavrikakis says.

Manos Mavrikakis is Ernest Micek Distinguished Chair, James A. Dumesic Professor, and Vilas Distinguished Achievement Professor in Chemical
and Biological Engineering at the University of Wisconsin-Madison.

Other authors include Barbara A.J. Lechner of the Technical University
of Munich, and Gabor A. Somorjai and Miquel Salmeron of Lawrence Berkeley National Laboratory and the University of California, Berkeley.

The authors acknowledge support from the U.S. Department of Energy,
Basic Energy Sciences, Division of Chemical Sciences, Catalysis Science Program, Grant DE-FG02-05ER15731; the Office of Basic Energy Sciences,
Division of Materials Sciences and Engineering, of the U.S. Department
of Energy under contract no. DE-AC02-05CH11231, through the Structure
and Dynamics of Materials Interfaces program (FWP KC31SM).

Mavrikakis acknowledges financial support from the Miller Institute at
UC Berkeley through a Visiting Miller Professorship with the Department
of Chemistry.

The team also used the National Energy Research Scientific Computing
Center, a DOE Office of Science User Facility supported by the
Office of Science of the U.S. Department of Energy under Contract
No. DE-AC02-05CH11231 using NERSC award BES- ERCAP0022773.

Part of the computational work was carried out using supercomputing
resources at the Center for Nanoscale Materials, a DOE Office of Science
User Facility located at Argonne National Laboratory, supported by DOE
contract DE-AC02- 06CH11357.

* RELATED_TOPICS
o Matter_&_Energy
# Chemistry # Physics # Materials_Science #
Organic_Chemistry # Inorganic_Chemistry #
Energy_Technology # Energy_and_Resources #
Engineering_and_Construction
* RELATED_TERMS
o Catalysis o Autocatalysis o Engineering o Physics o Technology
o Radical_(chemistry) o Machine o Catalytic_converter

========================================================================== Story Source: Materials provided by
University_of_Wisconsin-Madison. Original written by Jason Daley. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Lang Xu, Konstantinos G. Papanikolaou, Barbara A. J. Lechner,
Lisa Je,
Gabor A. Somorjai, Miquel Salmeron, Manos Mavrikakis. Formation
of active sites on transition metals through reaction-driven
migration of surface atoms. Science, 2023; 380 (6640): 70 DOI:
10.1126/science.add0089 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/04/230406152650.htm

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