US scientists discover way to convert CO2 to ethanol by accident

Scientists at the US Department of Energy’s (DOE) Oak Ridge National Laboratory(ORNL) have accidentally discovered a way to convert carbon dioxide (CO2), a greenhouse gas, into ethanol. They have developed an electrochemical process involving nanofabrication and catalysis science that uses tiny spikes of carbon and copper to convert the greenhouse gas to ethanol.

“We discovered somewhat by accident that this material worked,” said ORNL’s Adam Rondinone, lead author of the team’s study. “We were trying to study the first step of a proposed reaction when we realized that the catalyst was doing the entire reaction on its own.”

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 carbon dioxide dissolved in water was 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. “Ethanol was a surprise — it’s extremely difficult to go straight from carbon dioxide to ethanol with a single catalyst,” said Rondinone.

“We’re taking carbon dioxide, a waste product of combustion, and we’re pushing that combustion reaction backwards with very high selectivity to a useful fuel,” he added.

Described as “50-nanometer lightning rods”, the catalyst consists of copper nanoparticles embedded in carbon spikes which created a nanoscale structure. The spiky textured surface created helps facilitate the carbon dioxide-to-ethanol conversion.

The scientists were able to figure out how to limit the side reactions and end up with the one thing they want by using common materials and arranging them with nanotechnology, Rondinone said.

Since the technique relies on low-cost materials and has the 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 you to consume extra electricity when it’s available to make and store as ethanol,” Rondinone said. “This could help to 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 behavior.

ORNL’s Yang Song, Rui Peng, Dale Hensley, Peter Bonnesen, Liangbo Liang, Zili Wu, Harry Meyer III, Miaofang Chi, Cheng Ma, Bobby Sumpter and Adam Rondinone are coauthors on the study “High-Selectivity Electrochemical Conversion of CO2 to Ethanol using a Copper Nanoparticle/N-Doped Graphene Electrode.”

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