Electrochemical Modulation of Precatalysts Tailors the Cu Coordination Environment to Shift CO ₂ RR Products from C ₁ to C ₂₊

Copper-based catalysts show outstanding performance in electrochemical CO2 reduction reaction (CO2RR) toward hydrocarbons, yet controlling product selectivity remains challenging. While the coordination number of Cu sites dictates the reaction pathways and product distributions, structural reconstruction under cathodic operating potentials hampers precise regulation of their atomic coordination environment during catalysis. Herein, we investigate the in situ transformation of Cu-based precatalysts with well-defined initial coordination environments under CO2RR conditions, thereby establishing a direct correlation between the evolving Cu coordination number and product selectivity. The coordination environment evolves significantly from Cu2CN-c, featuring a Cu–N coordination number of 3.0, to Cu10CN-c with Cu–Cu coordination number of 6.3, leading to a shift in product distribution. The Faradaic efficiency (FE) ratio of C2H4/CH4 increases from 0.37 to 42, reflecting an enhancement in C–C coupling efficiency by 2 orders of magnitude. Through comprehensive in situ attenuated total reflection–Fourier transform infrared spectroscopy (in situ ATR-FTIR), electrochemical quartz crystal microbalance with dissipation (EQCM-D), and electrochemical characterizations, we demonstrate that precise modulation of Cu–N and Cu–Cu coordination ratios, achieved by controlled electroreduction and rational precatalyst design, can effectively balance proton-coupled electron transfer and C–C coupling kinetics. This work provides insights into the design principles for efficient Cu-based electrocatalysts enabling selective CO2 conversion to value-added hydrocarbon products.