Gold nanoparticles give an edge in recycling CO2

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Researchers from Brown University have shown gold nanoparticles can be tuned to selectively reduce CO2 into CO, an active carbon molecule that can be used to make alternative fuels and commodity chemicals. The key is maximizing the particles’ long edges, which are the active sites for the reaction, and minimizing sharp corners, which produce a byproduct. Credit: Sun Lab/Catalyst Design Lab/Brown University

—It’s a 21st-century alchemist’s dream: turning Earth’s superabundance of carbon dioxide—a greenhouse gas—into fuel or useful industrial chemicals. Researchers from Brown have shown that finely tuned gold nanoparticles can do the job. The key is maximizing the particles’ long edges, which are the active sites for the reaction.

By tuning  nanoparticles to just the right size, researchers from Brown University have developed a  that selectively converts  (CO2) to carbon monoxide (CO), an active carbon molecule that can be used to make  and commodity chemicals.

“Our study shows potential of carefully designed  to recycle CO2 into useful forms of ,” said Shouheng Sun, professor of chemistry and one of the study’s senior authors. “The work we’ve done here is preliminary, but we think there’s great potential for this technology to be scaled up for commercial applications.”

The findings are published in the Journal of the American Chemical Society.

The idea of recycling CO2—a greenhouse gas the planet current has in excess—is enticing, but there are obstacles. CO2 is an extremely stable molecule that must be reduced to an active form like CO to make it useful. CO is used to make synthetic natural gas, methanol, and other alternative fuels.

Converting CO2 to CO isn’t easy. Prior research has shown that catalysts made of gold foil are active for this conversion, but they don’t do the job efficiently. The gold tends to react both with the CO2 and with the water in which the CO2 is dissolved, creating hydrogen byproduct rather than the desired CO.

The Brown experimental group, led by Sun and Wenlei Zhu, a graduate student in Sun’s group, wanted to see if shrinking the gold down to nanoparticles might make it more selective for CO2. They found that the nanoparticles were indeed more selective, but that the exact size of those particles was important. Eight nanometer particles had the best selectivity, achieving a 90-percent rate of conversion from CO2 to CO. Other sizes the team tested—four, six, and 10 nanometers—didn’t perform nearly as well.

“At first, that result was confusing,” said Andrew Peterson, professor of engineering and also a senior author on the paper. “As we made the particles smaller we got more activity, but when we went smaller than eight nanometers, we got less activity.”

To understand what was happening, Peterson and postdoctoral researcher Ronald Michalsky used a modeling method called density functional theory. They were able to show that the shapes of the particles at different sizes influenced their catalytic properties.

“When you take a sphere and you reduce it to smaller and smaller sizes, you tend to get many more irregular features—flat surfaces, edges and corners,” Peterson said. “What we were able to figure out is that the most active sites for converting CO2 to CO are the edge sites, while the corner sites predominantly give the by-product, which is hydrogen. So as you shrink these particles down, you’ll hit a point where you start to optimize the activity because you have a high number of these edge sites but still a low number of these corner sites. But if you go too small, the edges start to shrink and you’re left with just corners.”

Now that they understand exactly what part of the catalyst is active, the researchers are working to further optimize the particles. “There’s still a lot of room for improvement,” Peterson said. “We’re working on new  that maximize these active sites.”

The researchers believe these findings could be an important new avenue for recycling CO2 on a commercial scale.

“Because we’re using nanoparticles, we’re using a lot less gold than in a bulk metal catalyst,” Sun said. “That lowers the cost for making such a catalyst and gives the potential to scale up.”

 

Explore further: Too green to be true? Researchers develop highly effective method for converting CO2 into methanol

More information: pubs.acs.org/doi/abs/10.1021/ja409445p

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what is an ATOM?

What is an atom? What are atoms made of?

Atoms are the basic building blocks of ordinary matter. Atoms can join together to form molecules, which in turn form most of the objects around you.

Atoms are composed of particles called protonselectrons and neutrons. Protons carry a positive electrical charge, electrons carry a negative electrical charge and neutrons carry no electrical charge at all. The protons and neutrons cluster together in the central part of the atom, called the nucleus, and the electrons ‘orbit’ the nucleus. A particular atom will have the same number of protons and electrons and most atoms have at least as many neutrons as protons.

Protons and neutrons are both composed of other particles called quarks and gluons. Protons contain two ‘up’ quarks and one ‘down’ quark while neutrons contain one ‘up’ quark and two ‘down’ quarks. The gluons are responsible for binding the quarks to one another.

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The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. Theatomic nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in the case of hydrogen-1, which is the only stable nuclide with no neutrons). The electrons of an atom are bound to the nucleus by the electromagnetic force. Likewise, a group of atoms can remain bound to each other by chemical bonds based on the same force, forming a molecule. An atom containing an equal number of protons and electrons is electrically neutral, otherwise it is positively or negatively charged and is known as an ion. An atom is classified according to the number of protons and neutrons in its nucleus: the number of protons determines the chemical element, and the number of neutrons determines the isotope of the element.[1]

Chemical atoms, which in science now carry the simple name of “atom,” are minuscule objects with diameters of a few tenths of ananometer and tiny masses proportional to the volume implied by these dimensions. Atoms can only be observed individually using special instruments such as the scanning tunneling microscope. Over 99.94% of an atom’s mass is concentrated in the nucleus,[note 1]with protons and neutrons having roughly equal mass. Each element has at least one isotope with an unstable nucleus that can undergoradioactive decay. This can result in a transmutation that changes the number of protons or neutrons in a nucleus.[2] Electrons that are bound to atoms possess a set of stable energy levels, or orbitals, and can undergo transitions between them by absorbing or emittingphotons that match the energy differences between the levels. The electrons determine the chemical properties of an element, and strongly influence an atom’s magnetic properties. The principles of quantum mechanics have been successfully used to model the observed properties of the atom.

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How to write a lab report

Lab reports are an essential part of all laboratory courses and usually a significant part of your grade. If your instructor gives you an outline for how to write a lab report, use that. Some instructors require the lab report be included in a lab notebook, while others will request a separate report. Here’s a format for a lab report you can use if you aren’t sure what to write or need an explanation of what to include in the different parts of the report. A lab report is how you explain what you did in experiment, what you learned, and what the results meant. Here is a standard format. If you prefer, you can print and fill in the science lab report template or download the pdf version of the template.

  1. Title Page
    Not all lab reports have title pages, but if your instructor wants one, it would be a single page that states:
    • The title of the experiment.
    • Your name and the names of any lab partners.
    • Your instructor’s name.
    • The date the lab was performed or the date the report was submitted.

     

  2. Title
    The title says what you did. It should be brief (aim for ten words or less) and describe the main point of the experiment or investigation. An example of a title would be: “Effects of Ultraviolet Light on Borax Crystal Growth Rate”. If you can, begin your title using a keyword rather than an article like ‘The’ or ‘A’.

     

  3. Introduction / Purpose
    Usually the Introduction is one paragraph that explains the objectives or purpose of the lab. In one sentence, state the hypothesis. Sometimes an introduction may contain background information, briefly summarize how the experiment was performed, state the findings of the experiment, and list the conclusions of the investigation. Even if you don’t write a whole introduction, you need to state the purpose of the experiment, or why you did it. This would be where you state your hypothesis.

     

  4. Materials
    List everything needed to complete your experiment.

     

  5. Methods
    Describe the steps you completed during your investigation. This is your procedure. Be sufficiently detailed that anyone could read this section and duplicate your experiment. Write it as if you were giving direction for someone else to do the lab. It may be helpful to provide a Figure to diagram your experimental setup.

     

  6. Data
    Numerical data obtained from your procedure usually is presented as a table. Data encompasses what you recorded when you conducted the experiment. It’s just the facts, not any interpretation of what they mean.

     

  7. Results
    Describe in words what the data means. Sometimes the Results section is combined with the Discussion (Results & Discussion).

     

  8. Discussion or Analysis
    The Data section contains numbers. The Analysis section contains any calculations you made based on those numbers. This is where you interpret the data and determine whether or not a hypothesis was accepted. This is also where you would discuss any mistakes you might have made while conducting the investigation. You may wish to describe ways the study might have been improved.

     

  9. Conclusions
    Most of the time the conclusion is a single paragraph that sums up what happened in the experiment, whether your hypothesis was accepted or rejected, and what this means.

     

  10. Figures & Graphs
    Graphs and figures must both be labeled with a descriptive title. Label the axes on a graph, being sure to include units of measurement. The independent variable is on the X-axis. The dependent variable (the one you are measuring) is on the Y-axis. Be sure to refer to figures and graphs in the text of your report. The first figure is Figure 1, the second figure is Figure 2, etc.

     

  11. References
    If your research was based on someone else’s work or if you cited facts that require documentation, then you should list these references.

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