Interfacial Water Frustration for Nitrate Semireduction to Hydroxylamine at Industrial-Relevant Currents

Hydroxylamine (NH₂OH) has a broad range of applications. Electrocatalytic semireduction of nitrate (NO₃^-) to NH₂OH is a promising pathway for its sustainable production. However, the reported route typically led to either insufficient or excessive hydrogenation because the mismatch between supply and demand of active species during electrocatalysis remains a critical challenge, resulting in poor selectivity to NH₂OH. Herein, we demonstrate an interfacial water (H₂O) frustration strategy to achieve highly selective electrocatalytic semireduction of nitrate (NO₃^-) to hydroxylamine (NH₂OH). By engineering the electric double layer (EDL) through alkali metal cation modulation, we precisely regulated the activation of interfacial H₂O to inhibit excessive active hydrogen (*H) generation, thereby controlling the *H supply. In addition, tensile-strained bibased catalysts promoted *NO intermediate formation, enhancing *H demand and suppressing over-reduction to NH₃. It achieved a Faradaic efficiency (FE) of 93.9% for NH₂OH at 120 mA cm^-2 under acidic conditions, which enabled the gram-scale synthesis of industrially relevant oximes with high nitrogen selectivity. Remarkably, this work achieved the highest NH₂OH FE under industrial-level current densities (>100 mA cm^-2). This work provided a generalizable approach for steering semireduction pathways through interfacial H₂O frustration, which constructs the supply-demand balance of essential active species involved in electrocatalytic reactions.