Bias-Driven Gauche-to-Trans Transformation of Surfactant Assembly as Permselective Gates for Efficient Ammonia Electrosynthesis from Nitrate

Electrochemical conversion of nitrate waste into ammonia represents a promising route for closing the anthropogenic nitrogen cycle, yet its efficiency is severely hampered by the sluggish supply of dilute nitrate and the parasitic hydrogen evolution derived from overwhelming interfacial water. Herein, we exploit the potential-driven structural transformation of amphiphilic surfactant assembly from disordered gauche conformations to ordered all-trans conformations to construct a dynamic permselective gate at the reaction interface. In situ spectroscopic investigations reveal that this field-induced reorientation enables the cationic headgroups adjoining the active surface to proactively enrich nitrate species via electrostatic attraction, while the distal long hydrophobic alkyl chains form a densely packed barrier that effectively shields the electrode surface from bulk water to suppress hydrogen evolution. With this tailored microenvironment, the enriched nitrate concentration and regulated proton supply work in synergy to match the reactant availability with the proton-electron transfer, significantly accelerating the reaction kinetics. As a result, the optimized system achieves a remarkable ammonia yield of 295.78 mg h^-1 mg^-1 and a near-unity Faradaic efficiency of 99.61%. Furthermore, an aqueous Zn-NO₃^- battery assembled with this cathode delivers a high power density of 37.42 mW cm^-2 and simultaneous ammonia production, providing a promising paradigm for energy-efficient nitrogen looping.