Scientists use peroxide to peer into metal oxide reactions

Date:
April 7, 2023
Source:
DOE/Brookhaven National Laboratory
Summary:
Researchers to get a better look at how peroxides on the surface
of copper oxide promote the oxidation of hydrogen but inhibit the
oxidation of carbon monoxide, allowing them to steer oxidation
reactions.


Facebook Twitter Pinterest LinkedIN Email
FULL STORY ========================================================================== Researchers at Binghamton University led research partnering with the
Center for Functional Nanomaterials (CFN) -- a U.S. Department of Energy
(DOE) Office of Science User Facility at Brookhaven National Laboratory
-- to get a better look at how peroxides on the surface of copper oxide
promote the oxidation of hydrogen but inhibit the oxidation of carbon
monoxide, allowing them to steer oxidation reactions. They were able to
observe these quick changes with two complementary spectroscopy methods
that have not been used in this way. The results of this work have been published in the journal Proceedings of the National Academy of Sciences (PNAS).


========================================================================== "Copper is one of the most studied and relevant surfaces, both in
catalysis and in corrosion science," explained Anibal Boscoboinik,
materials scientist at CFN. "So many mechanical parts that are used
in industry are made of copper, so trying to understand this element
of the corrosion processes is very important." "I've always liked
looking at copper systems," said Ashley Head also a materials scientist
at CFN. "They have such interesting properties and reactions, some of
which are really striking." Gaining a better understanding of oxide
catalysts gives researchers more control of the chemical reactions they produce, including solutions for clean energy. Copper, for example, can catalytically form and convert methanol into valuable fuels, so being
able to control the amount of oxygen and number of electrons on copper
is a key step to efficient chemical reactions.

Peroxide as a Proxy Peroxides are chemical compounds that contain two
oxygen atoms linked by shared electrons. The bond in peroxides is fairly
weak, allowing other chemicals to alter its structure, which makes them
very reactive. In this experiment, scientists were able to alter the redox steps of catalytic oxidation reactions on an oxidized copper surface (CuO)
by identifying the makeup of peroxide species formed with different gases:
O2 (oxygen), H2 (hydrogen), and CO (carbon monoxide).

Redox is a combination of reduction and oxidation. In this process,
the oxidizing agent gains an electron and the reducing agent loses
an electron.

When comparing these different peroxide species and how these steps played
out, researchers found that a surface layer of peroxide significantly
enhanced CuO reducibility in favor of H2 oxidation. They also found that,
on the other hand, it acted as an inhibitor to suppress CuO reduction
against CO (carbon monoxide) oxidation. They found that this opposite
effect of the peroxide on the two oxidation reactions stems from the modification of the surface sites where the reaction takes place.

By finding these bonding sites and learning how they promote or inhibit oxidation, scientists can use these gases to gain more control of how
these reactions play out. In order to tune these reactions though,
scientists had to get a clear look at what was happening.

The Right Tools for the Job Studying this reaction in situ was important
to the team, since peroxides are very reactive and these changes happen
fast. Without the right tools or environment, it's hard to catch such
a limited moment on the surface.

Peroxide species on copper surfaces were never observed using
in-situinfrared (IR) spectroscopy in the past. With this technique,
researchers use infrared radiation to get a better understanding of a material's chemical properties by looking at the way the radiation is
absorbed or reflected under reaction conditions. In this experiment,
scientists were able to differentiate "species" of peroxide, with very
slight variations in the oxygen they were carrying, which would have
otherwise been very hard to identify on a metal oxide surface.

"I got really excited when I was looking up the infrared spectra of
these peroxide species on a surface and seeing that there weren't many publications.

It was exciting that we could see these differences using a technique
that's not widely applied to these kind of species," recalled Head.

IR spectroscopy on its own wasn't enough to be sure though, which is
why the team also used another spectroscopy technique called ambient
pressure X-ray Photoelectron Spectroscopy (XPS). XPS uses lower energy
x-rays to kick electrons out of the sample. The energy of these electrons
gives scientists clues about the chemical properties of atoms in the
sample. Having both techniques available through the CFN User Program
was key to making this research possible.

"One of the things that we pride ourselves in is the instruments that
we have and modified here," said Boscoboinik. "Our instruments are
connected, so users can move the sample in a controlled environment
between these two techniques and study them in situ to get complementary information. In most other circumstances, a user would have to take the
sample out to go to a different instrument, and that change of environment could alter its surface." "A nice feature of CFN lies not only in its state-of-the-art facilities for science, but also the opportunities it
provides to train young researchers," said Guangwen Zhou professor at the Thomas J. Watson College of Engineering and Applied Science's Department
of Mechanical Engineering and the Materials Science program at Binghamton University. "Each of the students involved have benefited from extensive, hands-on experience in the microscopy and spectroscopy tools available
at CFN." This work was accomplished with the contributions of four
PhD students in Zhou's group: Yaguang Zhu and Jianyu Wang, the first
co-authors of this paper, and Shyam Patel and Chaoran Li. All of these
students are early in their career, having just earned their PhDs in 2022.

Future Findings The results of this study may apply to other types of
reactions and other catalysts besides copper. These findings and the
processes and techniques that led scientists there could find their
ways into related research. Metal oxides are widely used as catalysts themselves or components in catalysts. Tuning peroxide formation on other oxides could be a way to block or enhance surface reactions during other catalytic processes.

"I'm involved in some other projects related to copper and copper oxides, including transforming carbon dioxide to methanol to use as a fuel for
clean energy," said Head. "Looking at these peroxides on the same surface
that I use has the potential to make an impact on other projects using
copper and other metal oxides."
* RELATED_TOPICS
o Matter_&_Energy
# Organic_Chemistry # Chemistry # Materials_Science
# Nature_of_Water # Energy_and_Resources #
Inorganic_Chemistry # Physics # Spintronics
* RELATED_TERMS
o Redox o Silicone o Stainless_steel o Oxidizing_agent
o Nitrous_oxide o Hydrocarbon o Carbon_monoxide o
Organic_chemistry

========================================================================== Story Source: Materials provided by
DOE/Brookhaven_National_Laboratory. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Yaguang Zhu, Jianyu Wang, Shyam Bharatkumar Patel, Chaoran Li,
Ashley R.

Head, Jorge Anibal Boscoboinik, Guangwen Zhou. Tuning the
surface reactivity of oxides by peroxide species. Proceedings
of the National Academy of Sciences, 2023; 120 (13) DOI:
10.1073/pnas.2215189120 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/04/230407110731.htm

--- up 1 year, 5 weeks, 4 days, 10 hours, 50 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)