Steering the Site Distance of Atomic Cu-Cu Pairs by First-Shell Halogen Coordination Boosts CO₂-to-C₂ Selectivity

Electrocatalytic reduction of CO₂ into C₂ products of high economic value provides a promising strategy to realize resourceful CO₂ utilization. Rational design and construct dual sites to realize the CO protonation and C-C coupling to unravel their structure-performance correlation is of great significance in catalysing electrochemical CO₂ reduction reactions. Herein, Cu-Cu dual sites with different site distance coordinated by halogen at the first-shell are constructed and shows a higher intramolecular electron redispersion and coordination symmetry configurations. The long-range Cu-Cu (Cu-I-Cu) dual sites show an enhanced Faraday efficiency of C₂ products, up to 74.1 %, and excellent stability. In addition, the linear relationships that the long-range Cu-Cu dual sites are accelerated to C₂H₄ generation and short-range Cu-Cu (Cu-Cl-Cu) dual sites are beneficial for C₂H₅OH formation are disclosed. In situ electrochemical attenuated total reflection surface enhanced infrared absorption spectroscopy, in situ Raman and theoretical calculations manifest that long-range Cu-Cu dual sites can weaken reaction energy barriers of CO hydrogenation and C-C coupling, as well as accelerating deoxygenation of *CH₂CHO. This study uncovers the exploitation of site-distance-dependent electrochemical properties to steer the CO₂ reduction pathway, as well as a potential generic tactic to target C₂ synthesis by constructing the desired Cu-Cu dual sites.