Selective C Electroproduction via Back Bonding in Asymmetric Copper-Copper Motifs.

CO reduction reaction (CORR) is considered a highly attractive approach to reduce carbon emissions and yet encounters challenges in further converting *C intermediates to valuable two-carbon (C) products. Although copper-based catalysts exhibit satisfactory adsorption energy for *C species, the symmetrical charge distribution at adjacent copper sites leads to a strong repulsive force between adsorbed *C. Herein, asymmetric copper-copper (Cu-Cu) motifs with distinct adsorption behaviors have been constructed on the F-CuN substrate using the in situ isostructural substitution method. Compared to the high hybridization of Cu 3d and N 2p orbitals, implanted F not only reduces the hybridization strength but also endows the Cu with delocalized unpaired electrons. Accordingly, Cu, beyond forming an isolated 3d -2p σ bond between Cu and the key *C intermediate (*CHO), offers additional 3d-2p π back bonding to the *CHO. With dipole interactions in the asymmetric Cu-Cu motifs, the electrostatic repulsion between adjacent *CHO is diminished, efficiently promoting the C-C coupling in CORR. Therefore, the Cu-Cu motifs achieve an exceptional C selectivity of 81.5% with a partial current density of -325.9 mA cm and a C/C selectivity ratio of 10.47. This nuanced manipulation of atomic interactions illuminates a path to potentially groundbreaking alterations in material characteristics.