How Carbon Dioxide Becomes Ethanol

01/01/2018 |

Researchers accidentally discover new waste-to-fuel technology


ORNL's Yang Song (seated), Dale Hensley (standing left) and Adam Rondinone examine a carbon nanospike sample with a scanning electron microscope. Credit: ORNL

A new electrochemical process that turns carbon dioxide into usable ethanol with tiny spikes of carbon and copper was discovered almost by accident, says Adam Rondinone, a researcher at the Oak Ridge National Laboratory and lead author of the study describing the process.

The research team used a catalyst made of carbon, copper and nitrogen and applied voltage to it, setting off a chemical reaction that essentially reverses the combustion process. The carbon dioxide dissolved in water turned into ethanol with a yield of 63%, a noteworthy result given that this kind of reaction usually yields smaller amounts of several different byproducts.

“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,” Rondinone explains. “We’re taking carbon dioxide, a waste product of combustion, and pushing that reaction backwards with very high selectivity to a useful fuel. Ethanol was a surprise – it’s extremely difficult to go straight from carbon dioxide to ethanol with a single catalyst.”

The catalyst’s nanoscale structure consists of copper nanoparticles embedded in carbon spikes. Using common materials like these and arranging them with nanotechnology limits side reactions and avoids the use of rare or expensive metals, which have previously limited the economic viability of other catalysts. The spiky surface is likely what made the difference in this case, according to the researchers’ initial analysis, since it provided a large number of reactive sites to facilitate the chemical conversion.

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