Combined Structural and Interfacial Engineering to Tailor Water‐Gas Equilibrium for Electrochemical Ethanol Synthesis

The electrochemical reduction of CO 2 (eCO 2 R) to value‐added fuels, particularly ethanol, offers a sustainable route to close the carbon cycle and store energy. However, achieving high selectivity and stability toward ethanol remains challenging due to hydrogen evolution and the interplay of CO 2 transport, proton supply, and intermediate dynamics at the catalyst–electrolyte interface. Herein, we report a combined structural and interfacial engineering strategy to tailor the catalytic microenvironment for efficient ethanol production. Hollow silica spheres grafted with fluorinated siloxanes are employed as structural supports to load Cu nanoparticles, constructing a triphasic interface with balanced water‐gas transport, lending improved CO 2 accessibility, favored interfacial water structure, and enhanced local alkalinity. These effects collectively promote C–C coupling pathways while suppressing hydrogen evolution. Consequently, the optimal catalyst achieves an ethanol Faradaic efficiency of 47.6% at 400 mA cm −2 and maintains stable operation over 150 h. In situ spectroscopic studies reveal that ethanol selectivity follows a volcano‐type dependence on the * CHO/ * CO intermediate ratio, with an optimal range of 3.4–3.9 favoring asymmetric *CO–*CHO coupling. This work establishes a design paradigm wherein cooperative structural and interfacial engineering steers reaction pathways, offering an applicable strategy for developing advanced electrocatalysts toward targeted reduction products.