Graphene can now convert CO2 into liquid fuels using quantum dots

19 Dec 2016

Illustration of a graphene tube. Image: Rost9/Shutterstock

Not content with it being able to make futuristic sensors, researchers have now found a way to harness graphene to make it convert CO2 into liquid fuels.

Just a few days ago (16 December), we were told that researchers at the University of Exeter had cracked a new production method that could accelerate global supply. Now we are being told there might be a way to use it to make liquid fuels.

The breakthrough was made by a team from Rice University in the US, who harnessed the power of nitrogen-doped graphene quantum dots (N-GQDs) to use it as a catalyst in electrochemical reactions.

Potentially aiding in the continued effort to remove vast amounts of CO2 in the planet’s atmosphere, the resulting reaction created ethylene and ethanol.

A number of different methods of carbon capture have been devised, ranging from more natural solutions, like enormous forests, to more scientifically altered building materials.

Now using a single one-atom-thick sheet of graphene, the Rice researchers split it into small dots just a few nanometres in width. On their own, they do nothing to alter the surrounding air, but when nitrogen is introduced, the resulting chemical reaction turns it into an electrocatalyst.

However, why exactly the chemical reaction of the nitrogen and carbon is able to turn CO2 into liquid fuels remains something of a mystery.

While copper has been used as the main element within similar electrocatalyst reactions when making liquid fuels, this new N-GQD method was almost identical to the efficiency of the bulkier copper material.

Graphene dots

A single N-GQD with zig-zag edges. Image: Ajayan Group/Rice University

Not ready for large-scale production

The team’s findings showed that it reduced the amount of CO2 in the contained space by as much as 90pc, while converting 45pc of this into relatively small quantities of ethylene and ethanol.

As lead author of the study published in Nature Communications, Pulickel Ajayan said: “One of our questions is why this doping is so effective. When nitrogen is inserted into the hexagonal graphitic lattice, there are multiple positions it can take. Each of these positions, depending on where nitrogen sits, should have different catalytic activity.

“So it’s been a puzzle, and though people have written a lot of papers in the last five to 10 years on doped and defective carbon being catalytic, the puzzle is not really solved.”

Ajayan and his team admit, however, that this process is far from being ready for any large-scale use, but further research will increase the size of the project to see whether more nitrogen will yield more liquid fuels.

Colm Gorey was a senior journalist with Silicon Republic