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Using in situ infrared (IR) spectroscopy and ambient pressure X-ray photoelectron spectroscopy (XPS), scientists were able to differentiate “species” of peroxide.
Researchers at Binghamton University, in partnership with the Center for Functional Nanomaterials (CFN), a U.S. Department of Energy Office of Science User Facility at Brookhaven National Laboratory, have used peroxides to gain more control over the chemical reactions on copper surfaces (1).
The researchers were able to alter the redox steps of catalytic oxidation reactions on an oxidized copper surface (CuO) to steer reactions by identifying the makeup of the peroxide species formed with different gases. By finding these bonding sites and learning how they promote or inhibit oxidation, scientists can then use these gases to gain more control of how these reactions play out.
The researchers observed these changes with two complementary spectroscopy methods that had not been used in this way before. Using in situ infrared (IR) spectroscopy and ambient pressure X-ray photoelectron spectroscopy (XPS), they 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,” said Ashley Head, a materials scientist at CFN (1).
The team found that a surface layer of peroxide significantly enhanced CuO reducibility in favor of H2 oxidation. 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.
“Copper is one of the most studied and relevant surfaces, both in catalysis and in corrosion science. 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,” explained Anibal Boscoboinik, materials scientist at CFN (1).
Gaining a better understanding of oxide catalysts gives researchers more control of the chemical reactions they produce. For example, copper 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.
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. 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 chemical properties” (1).
The results of this work have been published in the journal Proceedings of the National Academy of Sciences (1).
(1) Zhu, Y.; Wang, J.; Patel, S. B.; Zhou, G. Tuning the surface reactivity of oxides by peroxide species. Proceedings of the National Academy of Sciences. 2023, 120 (13), e2215189120. DOI: 10.1073/pnas.2215189120