Electrostatic Focusing Enables Directed Active Hydrogen Delivery for pH-Universal Nitrate Electroreduction

Achieving pH-universal electroreduction of nitrate to ammonia remains a fundamental obstacle for practical nitrate remediation in aqueous environments. The central challenge is to achieve efficient utilization of the scarce reactive hydrogen (*H) under alkaline conditions while preventing *H recombination that promotes hydrogen evolution in acidic media. Herein, electrostatic focusing is introduced to regulate the directional delivery of *H toward nitrate-bound sites through the electrostatic potential (ESP) landscape established upon nitrate coordination. A copper-halide cluster catalyst achieves selective nitrate electroreduction across pH 1-13, delivering NH₃ Faradaic efficiencies (FE) of 92.9%-100%. Electrochemical, spectroscopic, and density functional theory (DFT) analyses reveal that nitrate binding generates a single, localized ESP minimum at the nitrate oxygen, which biases *H delivery toward productive hydrogenation. Moreover, quantitative correlations between ESP extrema and pH-dependent onset potentials indicate that an appropriately moderated ESP magnitude promotes proton-sensitive hydrogenation kinetics. This work establishes electrostatic focusing as a viable strategy for achieving pH-universal and selective nitrate electroreduction.