MSGID: 1:317/3 6430ede8   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    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.   
      
      
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   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   
      
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