ORNL team devises electrocatalyst for direct conversion of CO2 into ethanol with high selectivity; pushing the combustion reaction in reverse
Researchers at the Department of Energy’s Oak Ridge National Laboratory (ORNL) have developed an electrocatalyst which operates at room temperature and in water for the electroreduction of dissolved CO2 with high selectivity for ethanol. Their finding was serendipitous. An open-access paper on their work appears in the journal ChemistrySelect.
The team used a catalyst made of carbon, copper and nitrogen and applied voltage to trigger a 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 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 discovered somewhat by accident that this material worked. 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.
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. Ethanol was a surprise—it’s extremely difficult to go straight from carbon dioxide to ethanol with a single catalyst.—Adam Rondinone, lead author
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.
|ORNL researchers developed a catalyst made of copper nanoparticles (seen as spheres) embedded in carbon nanospikes that can convert carbon dioxide into ethanol. Click to enlarge.|
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. This could help to balance a grid supplied by intermittent renewable sources.—Adam Rondinone
The researchers plan to refine their approach to improve the overall production rate and further study the catalyst’s properties and behavior.
The work was supported by DOE’s Office of Science and used resources at the ORNL’s Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.
Song, Y., Peng, R., Hensley, D. K., Bonnesen, P. V., Liang, L., Wu, Z., Meyer, H. M., Chi, M., Ma, C., Sumpter, B. G. and Rondinone, A. J. (2016) “High-Selectivity Electrochemical Conversion of CO2 to Ethanol using a Copper Nanoparticle/N-Doped Graphene Electrode”, ChemistrySelect doi: 10.1002/slct.201601169