Porous material converts CO2 into carbon monoxide and oxygen

August 21, 2015 by Bob Yirka report
SEM image of COF-366-Co. Credit: Science DOI: 10.1126/science.aac8343

(Phys.org)—A team of researchers with Lawrence Berkeley National Laboratory and the University of California has developed a porous material that is able to split carbon dioxide molecules into carbon monoxide and oxygen. In their paper published in the journal Science, the team describes how they developed their material and how it might be used to help remove some of the carbon dioxide in the atmosphere.

Most scientists now agree that global warming is occurring at least partly due to , the most notorious being carbon dioxide. And since we can't seem to stop pumping CO2 into the air, researchers are looking into ways to pull it back out. Plants, as we all know, remove CO2, but the process is slow and there aren't enough of them to offset the amount of CO2 currently emitted. As one approach to removing CO2, scientists have been studying what are known as porphyrins—ring-shaped molecules with a cobalt atom at their core. When they are added to a solution containing two electrodes, an electrolyte, and some dissolved CO2, they are attracted to the negatively charged electrolyte, carrying electrons to the CO2, causing it to split into CO and O. But there are problems—the solution is dirty and the effectiveness of the porphyrins lessens over times. In this new effort, the team found a way around these problems by creating a covalent organic framework (COF)—a material made by linking porphyrins together into a mesh—one that is also able to conduct electricity. As CO2 percolates through the mesh, it is split into and oxygen by a bit of current.

The team found that the COF they developed worked much better than when using porphyrins alone, and then discovered that making the holes in the mesh bigger and adding copper improved the performance even more. The end results was a material that proved to be 60 times better at splitting CO2 than using porphyrins alone, and it was also more efficient—approximately 90 percent of the electrons were used in the process. Another plus was that the team was able to split 240,000 CO2 molecules per hour—putting it among the best at the job of any type of process.

The researchers also note that it might be possible to use their material to produce an energy source by combining the produced with hydrogen.

Explore further: Researchers discover a way to tease oxygen molecules from carbon dioxide

More information: Covalent organic frameworks comprising cobalt porphyrins for catalytic CO2 reduction in water, Science DOI: 10.1126/science.aac8343

ABSTRACT
Conversion of carbon dioxide to carbon monoxide and other value-added carbon products is an important challenge for clean energy research. Here, we report modular optimization of covalent organic frameworks (COFs), in which the building units are cobalt porphyrin catalysts linked by organic struts through imine bonds, to prepare a catalytic material for aqueous electrochemical reduction of CO2 to CO. The catalysts exhibit high Faradaic efficiency (90%) and turnover numbers (up to 290,000 with initial turnover frequency 9400 hours−1) at pH 7 with an overpotential of –0.55 V, equivalent to a 60-fold improvement in activity compared to the molecular cobalt complex, with no degradation over 24 hours. X-ray absorption data reveal the influence of the COF environment on the electronic structure of the catalytic cobalt centers.

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19 comments

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plaasjaapie
5 / 5 (1) Aug 21, 2015
And doing this gets you what, exactly? :-)
docile
Aug 21, 2015
This comment has been removed by a moderator.
atomsk
4 / 5 (4) Aug 21, 2015
And doing this gets you what, exactly? :-)

- less CO2
- more O2
- more CO
docile
Aug 21, 2015
This comment has been removed by a moderator.
ekim
5 / 5 (3) Aug 21, 2015
CO + H2 => CH3OH = (Fischer-Tropsch) => gasoline
antigoracle
1 / 5 (4) Aug 21, 2015
And doing this gets you what, exactly? :-)

Well, if the Chicken Littles rather breathe CO, then we'll get a much better world.
italba
1 / 5 (2) Aug 21, 2015
@ docile: Not if the energy comes from solar panels, specially on a spaceship...
PeakSpecies
5 / 5 (1) Aug 21, 2015
There must have been some special interest in not mentioning that this process is endothermic. In other words it requires electrical power to drive the process.

One much wonder if this is another sidetrack from the reality of what's coming down.
fay
5 / 5 (1) Aug 21, 2015
everyone, yes, this requires energy, which is of course logical since c+o2 "creates" energy BUT some sorts of energy we have are not equal to each other so it still makes sense to apply this thing. What i mean: transportation is arguably the hardest thing in economy to decarbon and electrify so, instead of elecrifying the cars, why dont we just continue to burn oil in them and offset it with this process which would draw energy from otherwise intermittent and problematic renewables?
Instead of changing the whole infrastructure to electrocars - which are horribly terrible replacement for the current ones - and feeding these electrocars with renewable power, we would simply retain current cars and infrastructure and just offset it with renewables which wouldnt even feed their intermittent unreliable electricity into grid but would just and only power this thing to remove co2.
baudrunner
not rated yet Aug 21, 2015
No mention of the scale of the experiment.

Before we jump to conclusions about possible applications
The average pair of human lungs can hold about 6 liters of air, but during normal respiration, only about 500 mL (one half of a liter) is inspired. Oxygen makes up 21% of air. There are 2.7 x 1019 (2,751.3) molecules in every cubic centimeter of air. 0.5 liter (500 cubic centimeter) contains 1,375,650 molecules, 21% of which are 288,886.5 oxygen molecules.
I asked MIStupid.com.. http://ask.mistup...ath.html
MR166
not rated yet Aug 21, 2015
" As CO2 percolates through the mesh, it is split into carbon dioxide and oxygen by a bit of current."

Hummm, how many "Bits" in a KWH?
Da Schneib
5 / 5 (1) Aug 21, 2015
The CO itself is a valuable chemical resource. This is actually a pretty interesting puzzle piece for yet another technology that can remove carbon from the atmosphere and make something useful out of it.
NoTennisNow
not rated yet Aug 21, 2015
One bit of chemistry: one gram mole of CO2 or O2 or any other molecule contains 6.022 times 10 raised 23 power number of molecules. The molar volume of a gas at STP is 22.4 liters (corrections are most welcome), or 22,400 cubic centimeters. In one cubic centimeter there are approximately 2.69 times 10 raised to the 19th power.

Chemistry and thermodynamics, energy generation and conversion are always interesting topics. Plant design, economics are life cycle analysis also rank way up there.
adam_russell_9615
not rated yet Aug 21, 2015
"the effectiveness of the porphyrins lessons"

lessens
docile
Aug 22, 2015
This comment has been removed by a moderator.
tear88
5 / 5 (1) Aug 22, 2015
One bit of chemistry: one gram mole of CO2 or O2 or any other molecule contains 6.022 times 10 raised 23 power number of molecules. The molar volume of a gas at STP is 22.4 liters (corrections are most welcome), or 22,400 cubic centimeters. In one cubic centimeter there are approximately 2.69 times 10 raised to the 19th power.


I had just looked up Avogadro's Constant, and the weight of one mole. At 240,000 CO2 molecules per hour, they're splitting

(2.4 x 10 to the 5th / 6.22 x 10 to the 23rd) * 12 grams = .0000000000000000185 grams,

give or take a decimal point.

A dandelion probably does it faster.

Edit: My calculation didn't take into account the atomic weights involved, but increasing it by a factor of 20 still leaves it a very small amount.
NoTennisNow
not rated yet Aug 22, 2015
Tear88, thank you for your comment. This helps to educate people that exponents (and units as well).

My calculations were aimed at correcting baudnner' example.
NoTennisNow
not rated yet Aug 22, 2015
My wife said that she overheard two undergraduates discussing applying to nursing school, and one of them asked the other whether units mattered.
NoTennisNow
not rated yet Aug 22, 2015
Also, 22.4 liters of air roughly weighs 29 grams or about one ounce.

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