Scientists Turned Carbon Dioxide into Oxygen by Zapping It with a Laser

The finding would explain early oxygen in Earth's atmosphere—and it's some fodder for sci-fi space breathing apparatuses.

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Oct 3 2014, 4:35pm

Image: NASA

Photosynthesis sure is a miracle, isn't it? It allows plants, bacteria, and algae to take carbon dioxide and, with the help of a little sunlight, turn it into the oxygen we all breathe. But now scientists have taken photosynthesis out of the equation and have managed to make oxygen (O2) by zapping carbon dioxide (CO2) with a laser.

In chemistry, the general wisdom is that molecules, if we were to anthropomorphize them, are lazy. Carbon dioxide, when its bonds are broken into its component parts, takes the "minimum energy path," meaning it will break into one oxygen atom and a carbon monoxide molecule (CO), because, as chemists Arthur Suits and David Parker explain in a new analysis in Science, CO "possesses a much more stable diatomic bond than O2."

If I were to do an ASCII art version of what the chemical bonds in carbon dioxide look like, it would be something like this:

O=C=O

Carbon is double bonded to the oxygen atoms, and it's way easier, chemically speaking, to simply lop off one of those bonds and create a CO molecule and an oxygen atom.

So, the conventional wisdom has been that under almost all circumstances, it'd be impossible to take carbon dioxide—say, from a human's exhalation, for instance—and turn it back into gaseous oxygen, which would require two oxygen atoms. But then, researchers at the University of California, Davis decided to try doing just that by exciting carbon dioxide using what's known as a "high energy vacuum ultraviolet laser." 

It turns out that, in a highly excited (and still anthropomorphized) state, carbon dioxide and other molecules have a bit more energy to skip that minimum energy path and, like any agitated person/molecule, feel like "roaming," which is a chemical phenomenon in which chemical bonds will break in other ways.

The UC Davis researchers found that the chemical bonds did indeed break in other ways, and were able to turn carbon dioxide back into oxygen and a single carbon atom (they also describe the discovery in Science).

Suits and Parker explain it in their analysis like this:

These CO2 results may be an example of roaming, a particularly striking class of reactions that has emerged in recent years, in which an excited molecule begins to dissociate by simple bond fission, but instead, an intramolecular reaction takes place that leads to unexpected products.

It's a great discovery that could tell us something about how Earth's atmosphere formed. In fact, vacuum ultraviolet light may commonly interact with carbon dioxide in the upper atmosphere, where the Sun's light hits molecules in the vacuum of space.

Most of the oxygen on Earth came from the "Great Oxygenation Event," which scientists think was a photosynthetic-led occurrence occurring roughly 2.4 billion years ago. But more recently, scientists have argued that there had to at least be small amounts of oxygen somewhere in the Earth's atmosphere for that event to originally occur, and this finding would evidently be one explanation for how that oxygen could have existed.

And, because it's a Friday and because we like to look at the far future here at Motherboard, think of what the finding could potentially mean: This experiment proves that we have the means, here on Earth, to take a waste product of human respiration and turn it back into the input.

I reached out to the authors of this study about whether they thought the finding had any implications for far-future devices where you could create, say, a closed-system respiratory apparatus where people in space could breathe out carbon dioxide and some small vacuum ultraviolet laser could blast it back into into oxygen that could be breathed again.

None of the researchers I emailed responded to me, unfortunately, but, in their analysis, Suits and Parker note that new avenues and alternatives to high energy vacuum ultraviolet lasers are being researched to induce roaming. High energy vacuum ultraviolet lasers do, after all, seem like they would require a lot of power to operate—which could potentially negate any climate benefit, if your mind has gone there—but hey, you never know.

At the very least, it should give sci-fi writers some new material to work with.