ORNL researchers have developed a catalyst made of copper nanoparticles (seen as spheres) embedded in carbon nanospikes that can convert carbon dioxide into ethanol. Image: ORNL.In a new twist on waste-to-fuel technology, scientists at the US Department of Energy's Oak Ridge National Laboratory (ORNL) have developed an electrochemical process that uses tiny spikes of carbon and copper to turn carbon dioxide, a greenhouse gas, into ethanol. Their finding, which involves nanofabrication and catalysis science, was highly serendipitous.
"We discovered somewhat by accident that this material worked," admitted ORNL's Adam Rondinone, lead author of a paper on this work 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."
By applying a voltage in the presence of a catalyst made of carbon, copper and nitrogen, the scientists were able to trigger a complicated chemical reaction that essentially reverses the combustion process. They found that the nanotechnology-based catalyst, which contains multiple reaction sites, could convert a solution of carbon dioxide 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 carbon dioxide, a waste product of combustion, and we're pushing that combustion reaction backwards with very high selectivity to a useful fuel," Rondinone explained. "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. "They are like 50nm lightning rods that concentrate electrochemical reactivity at the tip of the spike," Rondinone said.
Given the technique's reliance on low-cost materials and ability to operate at room temperature in water, the researchers believe their 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 now plan to refine their approach by improving the overall production rate and studying the catalyst's properties and behavior in more detail.
This story is adapted from material from Oak Ridge National Laboratory, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.