Engineers at the American university of Georgia Tech have devised a process that converts carbon dioxide removed from the atmosphere into a raw material that could be used to give life to new plastics, chemicals or fuels.
Their study drastically reduces the costs and energy required for these direct air capture systems (the so-called DACs), helping to improve the economics of a process that will be fundamental to tackling climate change and mitigating its effects.
the keys: catalyst and reactor
The key to this revolutionary discovery lies in a new type of catalyst and in a electrochemical reactor which can be easily integrated into existing DAC systems.
“All my team’s research projects – explains the manager, Marta Hatzell – focus on decarbonisation, but this one in particular has the opportunity to move more quickly towards commercialization, bringing concrete and immediate benefits”.
The traditional DAC process involves extracting carbon dioxide from the air using some type of chemical or material that captures CO2 molecules. To release that captured carbon (for example to store it underground or process it for productive reuse) is necessary significant energywhich powers complicated and expensive systems.
And along the way it loses some of the CO2 removed from the atmosphere.
less energy and little CO2 dispersion
Hatzell’s team focused on using a liquid alkaline solution called Koh to capture carbon: Koh turns CO2 into bicarbonates, which ultimately have to be separated again. But the Georgia Tech researchers managed to completely avoid this last, energy-costly step.
Working with Jihun Oh’s lab at the Korea Advanced Institute of Science and Technology, the researchers created a new nickel-based catalyst and paired it with bipolar membrane electrodes. This system uses electricity to extract CO2 from bicarbonates right next to the catalyst, which then converts it into carbon monoxide gas.
This is the secret: combines two steps into one. “We are capturing CO2 in carbonates, which is a spontaneous process and doesn’t require a lot of energy. And we get rid of the desorption process and all that energy expense, saving around 90% of energy in the capture process and approximately 50% of the capital cost.”
Their setup is also extremely efficient in using all the CO2 that passes through the reactor: “We are twice as efficient. Our efficiency in using CO2 is almost 70%, while in the gas phase system it is 35%. The maximum CO2 usage in gas-based systems is theoretically 50%. But in our case, our maximum efficiency is 100%,” the researchers conclude.
The study revealed how well the catalyst works in a acidic environment. When the reactor layer with the catalyst becomes acidic, another chemical process occurs, called a hydrogen evolution reaction, which reduces CO2 to CO. The new nickel-based catalyst suppresses this interference.
Producing carbon monoxide from CO2 taken from the atmosphere is a complicated and intensive process. But if done in an economically sustainable way, the resulting raw material could be linked to existing chemical processes and transformed into useful new products. Connecting these processes is the team’s next goal.
CO can become the basis for plastics, important industrial chemicals such as ethylene, and maybe even jet fuel in the future.
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