Scientists at the Department of Energy’s Oak Ridge National Lab have developed a way to convert carbon dioxide directly into ethanol. The team is researching an electrochemical process that uses tiny spike of carbon and copper to convert CO2 into ethanol. Their discovery involves nanofabrication and catalysis science.
ORNL’s Yang Song (seated), Dale Hensley (standing left) and Adam Rondinone examine a carbon nanospike sample with a scanning electron microscope.
“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 realized that the catalyst was doing the entire reaction on its own.”
The scientists used a catalyst made of carbon, copper and nitrogen and then applied voltage to trigger a chemical reaction that, in essence, reverses the combustion process. Utilizing a nanotechnology-based catalyst that has several reaction sites, the solution of CO2 that was dissolved in water turned into ethanol with a yield of 63 percent. In most instances, say the researchers, this reaction results in small amounts of multiple products.
“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,” explained Rondinone. “Ethanol was a surprise — it’s extremely difficult to go straight from carbon dioxide to ethanol with a single catalyst.”
The catalyst’s novelty lies in its nanoscale structure, consisting of copper nanoparticles embedded in carbon spikes. This nano-texturing approach 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,” Rondinone said.
The researchers’ initial analysis suggests that the spiky textured surface of the catalysts provides ample reactive sites to facilitate the carbon dioxide-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 you to consume extra electricity when it’s available to make and store as ethanol,” Rondinone added. “This could help to balance a grid supplied by intermittent renewable sources.”