Production of multicarbon products (C₂₊) from CO₂ electroreduction reaction (CO₂RR) is highly desirable for storing renewable energy and reducing carbon emission. The electrochemical synthesis of CO₂RR catalysts that are highly selective for C₂₊ products via electrolyte‐driven nanostructuring is presented. Nanostructured Cu catalysts synthesized in the presence of specific anions selectively convert CO₂ into ethylene and multicarbon alcohols in aqueous 0.1 m KHCO₃ solution, with the iodine‐modified catalyst displaying the highest Faradaic efficiency of 80 % and a partial geometric current density of ca. 31.2 mA cm⁻² for C₂₊ products at −0.9 V vs. RHE. Operando X‐ray absorption spectroscopy and quasi in situ X‐ray photoelectron spectroscopy measurements revealed that the high C₂₊ selectivity of these nanostructured Cu catalysts can be attributed to the highly roughened surface morphology induced by the synthesis, presence of subsurface oxygen and Cu⁺ species, and the adsorbed halides.

Supported nanoparticles make the reaction faster: Several techniques now allow surface structures used as catalysts to be probed during exposure to reactive gases, as opposed to under vacuum conditions. Divins et al. used near-ambient-pressure x-ray photoelectron spectroscopy to compare the effect of reaction gases on unsupported palladium-rhodium nanoparticles versus ones on a reducible cerium oxide support. For the reaction of ethanol with steam to produce hydrogen, the supported nanoparticles were more reactive and less prone to reduction and surface rearrangement. Science , this issue p. 620