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Oak Ridge National Laboratory transforms CO2 to ethanol with help from nanotechnology

In a new twist to waste-to-fuel technology, scientists at the US Department of Energy’s Oak Ridge National Laboratory (ORNL) have developed a new way to turn CO2 into ethanol.

The finding involves nanofabrication and catalysis science, using an electrochemical process that produces tiny spikes of carbon and copper to transform greenhouse gas into biofuel.

 “We discovered somewhat by accident that this material worked,” said ORNL’s Adam Rondinone, lead author of the team’s study published in ChemistrySelect.

“We were trying to study the first step of a proposed reaction when we realised that the catalyst was doing the entire reaction on its own,” he added.

The team used a catalyst made of carbon, copper, and nitrogen and applied voltage to trigger a complicated chemical reaction that essentially reverses the combustion process.

With the help of the nanotechnology-based catalyst, which contains multiple reaction sites, the solution of CO2 dissolved in water turned into ethanol with a yield of 63%.

Typically, this type of electrochemical reaction results in a mix of several different products in small amounts.

“We’re taking CO2, a waste product of combustion, and we’re pushing that combustion reaction backwards with very high selectivity to a useful fuel,” Rondinone said.

“Ethanol was a surprise – it’s extremely difficult to go straight from CO2 to ethanol with a single catalyst.”

The catalyst’s novelty lies in its nanoscale structure, consisting of copper nanoparticles embedded in carbon spikes, which avoids the use of expensive or rare metals such as platinum that limit the economic viability of many catalysts. 

“By using common materials, but arranging them with nanotechnology, we figured out how to limit the side reactions and end up with the one thing that we want,” said Rondidone.

The researchers’ initial analysis suggests that the spiky textured surface of the catalysts provides ample reactive sites to facilitate the CO2-to-ethanol conversion.

Given the technique’s reliance on low-cost materials and an ability to operate at room temperature in water, the researchers believe the approach could be scaled up for industrially relevant applications.

For instance, the process could be used to store excess electricity generated from variable power sources such as wind and solar.

“A process like this would allow us to consume extra electricity when it’s available to make and store as ethanol,” Rondinone speculated. “This could help balance a grid supplied by intermittent renewable sources.” 

The researchers plan to refine their approach to improve the overall production rate and further study the catalyst’s properties and behaviour.