Carbon dioxide electroreduction to ethylene based on cyano-containing organocatalysts

The electrochemical CO₂ reduction reaction (eCO₂RR), producing gaseous C₂₊ products such as ethylene (C₂H₄), represents a sustainable strategy to mitigate the greenhouse effect. Inspired by the promotion effect of the cyano group (–C≡N) for C–C coupling in organic chemistry, several cyano-containing organocatalysts have been found to be capable of directly converting CO₂ into C₂H₄ with –C≡N as the active center during the eCO₂RR. The selectivity of C₂H₄ for the representative catalyst, metal-free dicyandiamide (DCD), reached 27.6 % after partial hydrogenation in KHCO₃ solution. In addition, its selectivity can be further improved to 57.7 % when coupled with oriented Cu crystals. The experimental and computational results collectively reveal that charge redistribution between Cu{100} and DCD promotes the partial hydrogenation of the cyano group and lays the foundation for the reduced energy barrier for the CO₂ reduction on –C≡N. This study breaks the limitations of traditional metal/metal oxide-based catalysts by using cyano-containing organocatalysts for direct C₂₊ product generation, expanding the eCO₂RR catalyst library. In addition, this research elucidates the role of charge redistribution and cyano group hydrogenation in lowering reaction barriers, providing fundamental guidance for the design of new organocatalysts.