UC Berkeley

Promotion of C-C bonds is one of the key fundamental questions in the field of CO₂ electroreduction. Much progress has occurred in developing bulk-derived Cu-based electrodes for CO₂-to-multicarbons (CO₂-to-C₂₊), especially in the widely studied class of high-surface-area "oxide-derived" copper. However, fundamental understanding into the structural characteristics responsible for efficient C-C formation is restricted by the intrinsic activity of these catalysts often being comparable to polycrystalline copper foil. By closely probing a Cu nanoparticle (NP) ensemble catalyst active for CO₂-to-C₂₊, we show that bias-induced rapid fusion or "electrochemical scrambling" of Cu NPs creates disordered structures intrinsically active for low overpotential C₂₊ formation, exhibiting around sevenfold enhancement in C₂₊ turnover over crystalline Cu. Integrating ex situ, passivated ex situ, and in situ analyses reveals that the scrambled state exhibits several structural signatures: a distinct transition to single-crystal Cu₂O cubes upon air exposure, low crystallinity upon passivation, and high mobility under bias. These findings suggest that disordered copper structures facilitate C-C bond formation from CO₂ and that electrochemical nanocrystal scrambling is an avenue toward creating such catalysts.