AbstractWith ever‐increasing energy consumption and continuous rise in atmospheric CO₂ concentration, electrochemical reduction of CO₂ into chemicals/fuels is becoming a promising yet challenging solution. Sn‐based materials are identified as attractive electrocatalysts for the CO₂ reduction reaction (CO₂RR) to formate but suffer from insufficient selectivity and activity, especially at large cathodic current densities. Herein, we demonstrate that Cu‐doped SnS₂ nanoflowers can undergo in situ dynamic restructuring to generate catalytically active S‐doped Cu/Sn alloy for highly selective electrochemical CO₂RR to formate over a wide potential window. Theoretical thermodynamic analysis of reaction energetics indicates that the optimal electronic structure of the Sn active site can be regulated by both S‐doping and Cu‐alloying to favor formate formation, while the CO and H₂ pathways will be suppressed. Our findings provide a rational strategy for electronic modulation of metal active site(s) for the design of active and selective electrocatalysts towards CO₂RR.