Directing CO2 electroreduction pathways for selective C2 product formation using single-site doped copper catalysts

Manipulating the selectivity-determining step in post-C–C coupling is crucial for enhancing C2 product specificity during electrocatalytic CO2 reduction, complementing efforts to boost rate-determining step kinetics. Here we highlight the role of single-site noble metal dopants on Cu surfaces in influencing C–O bond dissociation in an oxygen-bound selectivity-determining intermediate, steering post-C–C coupling toward ethylene versus ethanol. Integrating theoretical and experimental analyses, we demonstrate that the oxygen binding strength of the Cu surface controls the favorability of C–O bond scission, thus tuning the selectivity ratio of ethylene-to-ethanol. The Rh-doped Cu catalyst with optimal oxygen binding energy achieves a Faradaic efficiency toward ethylene of 61.2% and an ethylene-to-ethanol Faradaic efficiency ratio of 4.51 at –0.66 V versus RHE (reversible hydrogen electrode). Integrating control of both rate-determining and selectivity-determining steps further raises ethylene Faradaic efficiency to 68.8% at 1.47 A cm−2 in a tandem electrode. Our insights guide the rational design of Cu-based catalysts for selective CO2 electroreduction to a single C2 product. Steering the selectivity-determining steps is as important as the C–C coupling steps in CO2 electroreduction. Here the authors highlight that single-site noble metal dopants on the Cu surface can influence C–O bond dissociation and direct the post-C–C coupling pathways to ethylene versus ethanol.