Tailored Selectivity for CO and C2+ in CO2 Reduction: Insights into the Dynamic Evolution of Electrocatalysts

Abstract Controlling product selectivity in electrochemical CO 2 reduction (eCO 2 R) is critical for efficient CO 2 conversion. However, the dynamic structural changes of Cu‐based catalysts during operation complicate mechanistic understanding. Here, we investigate fluorine‐modified copper pre‐catalysts with varying doping levels and reveal how their structural evolution governs eCO 2 R activity and selectivity. Through operando spectroscopy characterizations and theoretical simulations, we show that fluorine leaches rapidly during electrolysis, transforming Cu 2 ⁺ precursors into metallic Cu⁰ with distinct local structures. Cu‐F‐4, with the lowest coordination number, exhibits high eCO 2 R activity and favors CO formation with a Faradaic efficiency (FE CO ) of 81% at −0.45 V. In contrast, Cu‐F‐1, enriched in grain boundaries and Cu(100) facets, achieves a high FE C2+ of 80% at −0.65 V. Differences in local pH, *OH coverage, and *CO binding energies further modulate catalytic pathways. Our findings highlight the importance of dynamic catalyst reconstruction in steering product selectivity and offer design principles for advancing CO 2 ‐to‐chemicals conversion.