The study explores the development of highly selective copper catalysts for the electrochemical reduction of carbon dioxide (CO₂) to ethylene, a valuable hydrocarbon fuel. The researchers used plasma treatments to create oxidized copper catalysts with lower overpotentials and record selectivity towards ethylene (60%). Through a combination of electrochemical measurements and microscopic and spectroscopic techniques, they found that copper oxides are surprisingly resistant to reduction, and copper+ species remain on the surface during the reaction. This finding challenges the conventional assumption that only metallic copper is active in CO₂ reduction. The results demonstrate that the presence of copper+ is key for lowering the onset potential and enhancing ethylene selectivity, while the roughness of oxide-derived copper catalysts plays only a partial role in determining catalytic performance. The study provides insights into the mechanisms behind the improved activity and selectivity of these catalysts, which could aid in the design of more efficient CO₂-to-hydrocarbon conversion technologies.The study explores the development of highly selective copper catalysts for the electrochemical reduction of carbon dioxide (CO₂) to ethylene, a valuable hydrocarbon fuel. The researchers used plasma treatments to create oxidized copper catalysts with lower overpotentials and record selectivity towards ethylene (60%). Through a combination of electrochemical measurements and microscopic and spectroscopic techniques, they found that copper oxides are surprisingly resistant to reduction, and copper+ species remain on the surface during the reaction. This finding challenges the conventional assumption that only metallic copper is active in CO₂ reduction. The results demonstrate that the presence of copper+ is key for lowering the onset potential and enhancing ethylene selectivity, while the roughness of oxide-derived copper catalysts plays only a partial role in determining catalytic performance. The study provides insights into the mechanisms behind the improved activity and selectivity of these catalysts, which could aid in the design of more efficient CO₂-to-hydrocarbon conversion technologies.