Catalysts speed up chemical reactions and form the backbone of many industrial processes; for example, they are essential in transforming heavy oil into gasoline or jet fuel. Researchers have discovered a new electrocatalyst that converts carbon dioxide (CO2) and water into ethanol with very high energy efficiency, high selectivity for the desired final product, and low cost.
Ethanol is a particularly desirable commodity because it is an ingredient in nearly all U.S. gasoline and is widely used as an intermediate product in the chemical, pharmaceutical, and cosmetics industries. The process resulting from the catalyst would electrochemically convert the CO2 emitted from industrial processes, such as fossil fuel power plants or alcohol fermentation plants, into valuable commodities at reasonable cost.
The catalyst consists of atomically dispersed copper on a carbon-powder support. By an electrochemical reaction, this catalyst breaks down CO2 and water molecules and selectively reassembles the broken molecules into ethanol under an external electric field. The electrocatalytic selectivity, or “Faradaic efficiency,” of the process is over 90 percent. The catalyst also operates stably over extended operation at low voltage. The mechanism should also provide a foundation for development of highly efficient electro-catalysts for carbon dioxide conversion to a vast array of value-added chemicals.
Because CO2 is a stable molecule, transforming it into a different molecule is normally energy-intensive and costly. But the electrochemical process of CO2-to-ethanol conversion using the catalyst could be coupled to the electric grid to take advantage of the low-cost electricity available from renewable sources like solar and wind during off-peak hours. Because the process runs at low temperature and pressure, it can start and stop rapidly in response to the intermittent supply of the renewable electricity.
The team prepared several new catalysts using the approach and found that they are all highly efficient in converting CO2 to other hydrocarbons.