Steering Ethylene Electrosynthesis by Controlling Interfacial Water Orientation

Controlling reaction pathway via solvent polarization dynamics remains a grand challenge in catalysis due to elusive interfacial kinetic regulation mechanisms. Here, we resolve this dilemma by establishing interfacial water orientation that directly couples H₂O polarization with reaction pathway bifurcation. Using electrocatalytic CO₂ reduction as a typical platform, we demonstrate that precisely engineered H-down water alignment, achieved via adaptive subsurface tuning (AST) strategy of Ga-doped Cu catalysts, dynamically regulates proton transfer directionality and intermediate stabilization. The optimized Ga/Cu catalyst achieved a Faradaic efficiency (FE) of 68.8% for ethylene at 800 mA cm^-2, surpassing ethanol production by 8.2-fold, and the current density was among the highest reported for catalysts with high ethylene FE. Detailed experimental studies and theoretical calculations corroborate that H-down alignment enhanced *H availability, directing protons to selectively cleave the C─O bond of *CHCOH intermediates over hydrogenation pathways, yielding high ethylene FE and current density. These findings establish interfacial water orientation as a pivotal descriptor for steering C─C coupling selectivity in electrocatalysis, offering a rational design principle for efficient electroreduction systems.