A Sungkyunkwan catalyst splits the job between two metals, with zinc preparing the intermediates and copper joining the carbons, cutting the by-products that make CO2 conversion expensive.
Running carbon dioxide through an electrochemical cell to make something useful is an old idea with a persistent flaw. The reaction works. It simply makes too many things at once.
Copper catalysts, the only metals that reliably push CO2 past single-carbon products, yield a mixture: carbon monoxide, formate, methane, ethylene, ethanol, propanol, hydrogen from water splitting alongside everything else. Separating that mixture consumes energy, and separation energy is where the economics of CO2 conversion usually collapse.
A team led by Professor Hyoyoung Lee in the Department of Chemistry at Sungkyunkwan University reports a catalyst that reaches 69 per cent ethanol Faradaic efficiency in a membrane electrode assembly. The work appears in Applied Catalysis B: Environment and Energy.
What the number means
Faradaic efficiency is the measure that matters for a reaction with competing products. It asks what fraction of the electrons pushed through the cell ended up in the intended product rather than in something else.
Sixty-nine per cent to ethanol specifically is a strong figure. Ethanol is one of the harder targets, because it requires joining two carbon atoms and then keeping the product from going further or branching into the closely related alternatives. Much of the field reports high efficiency to ethylene or to carbon monoxide, which are easier.
The membrane electrode assembly matters too. An MEA is the configuration used in working electrolysers, with the catalyst pressed against an ion-conducting membrane rather than suspended in a beaker of electrolyte. Results from the laboratory cells often do not survive the move to an MEA, where mass transport, water management and local chemistry all change. Reporting the number in an MEA is a meaningfully harder test than reporting it in an H-cell.
Two metals, two jobs
The design places copper and zinc atoms directly next to each other on a carbon support, and the paper’s title describes the effect as an atomic-scale synergy directing asymmetric carbon–carbon coupling.
The division of labour is explicit: zinc helps prepare key reaction intermediates, while copper promotes the formation of carbon–carbon bonds. The release describes the cooperative structure as directing the reaction more efficiently toward ethanol while reducing the formation of competing products.
The chemistry behind that split is reasonably well understood in outline. Zinc is good at the first step, reducing CO2 to adsorbed carbon monoxide, and poor at anything beyond it — zinc catalysts on their own produce carbon monoxide and stop. Copper is the metal that can take adsorbed CO further and couple two carbons together, but it is also the metal that does everything else. Supplying copper with a steady local feed of the intermediate it needs, from a neighbour that cannot compete for the later steps, is a way of biasing a promiscuous catalyst.
The word asymmetric in the paper’s title points at the selectivity question. Ethanol and ethylene both come from coupling two carbons, and which one forms depends on how the coupled intermediate is oxygenated and when. A coupling between two chemically distinct adsorbed species, rather than two identical ones, is one route to favouring the oxygenated product.
The adjacency problem
Getting two different metals to sit next to each other at the atomic scale, and stay there, is the hard part of this kind of design.
Metals on a support tend to segregate. Atoms migrate, like aggregates with like, and a carefully mixed surface becomes copper islands beside zinc islands — at which point the cooperative effect disappears, because an intermediate formed on a zinc island has to cross a copper island’s worth of distance to reach a useful site. Keeping the two species interspersed on a carbon support is what makes the geometry work, and it is also the thing most likely to degrade in operation.
Which brings up the study’s weakest reported point. The release describes “promising operational stability” and gives no figures — no hours of operation, no efficiency retained, no current density. For a catalyst whose function depends on maintaining atomic-scale adjacency, stability is not a secondary specification.
What is still missing
The release is unusually candid about the gap to application, naming four things that need further improvement: current density, energy efficiency, product concentration and long-term operation. No values are given for any of them.
Those four are, between them, most of what separates a reported catalyst from an industrial process. Current density sets how much product a given area of electrode makes, and therefore how large a plant has to be. Energy efficiency determines whether the electricity consumed is worth the fuel produced. Product concentration decides how much water has to be distilled away, which for ethanol is expensive — a dilute aqueous ethanol stream can easily cost more energy to concentrate than the ethanol contains. Long-term operation is whether any of it lasts.
It is also worth being clear about what ethanol from CO2 is for. The release lists its uses as a renewable fuel, solvent, disinfectant and industrial raw material, and the case for making it electrochemically rests on having surplus low-carbon electricity and a concentrated CO2 stream in the same place. As a way of storing intermittent renewable power in a liquid that existing infrastructure can handle, it is appealing. As a climate measure it only counts if the electricity is clean and the carbon would otherwise have been emitted.
No one is quoted
The release carries no quotations attributed to any researcher. Everything above is drawn from its own descriptive text and from the paper’s title and abstract details, which is worth flagging: there is no scientist on the record here explaining what they think the result means or how far they would push it.
The authors listed in the credit are K. Talat, S. Perumal, U. Muhammad, E. Lee, T. Thi Thuy Nga, M. Ali, M. Kim, J. Choi, C.-L. Dong, H. Lee and H. Lee. Roles and affiliations beyond Hyoyoung Lee’s are not stated, and the release does not state the study’s funding sources. The paper was published online on 29 June 2026 in volume 399 of the journal.
Notes
- Talat, K., et al. “Atomic-scale Cu-Zn synergy directs asymmetric C-C coupling for ethanol-selective CO2 electroreduction.” Applied Catalysis B: Environment and Energy, 2026, 399: 127179. DOI: 10.1016/j.apcatb.2026.127179.
- Sungkyunkwan University. “SKKU researchers develop a new catalyst to convert carbon dioxide into ethanol using electricity.” EurekAlert!, 3 August 2026. https://www.eurekalert.org/news-releases/1138651.