Bioinspired Interfacial Hydration Engineering via Metal–Organic Frameworks for Efficient Nitrate‐To‐Ammonia Conversion in Neutral Media

ABSTRACT Electrocatalytic nitrate reduction to ammonia (eNO ₃ RR) offers a promising pathway for sustainable ammonia synthesis but is severely impeded by sluggish proton‐coupled electron transfer kinetics and competitive hydrogen evolution, particularly at industrially relevant current densities in neutral media. Herein, we report a bioinspired interfacial hydration engineering strategy by constructing a UiO‐66‐NH ₂ metal–organic framework overlayers on copper electrodes to boost eNO ₃ RR activity and selectivity. The optimized UiO‐66‐NH ₂ @Cu electrode exhibits exceptional performance, achieving a Faradaic efficiency of 98.6% and an ammonia yield rate of 5.02 mmol cm ⁻² h ⁻¹ , and sustaining an ammonia partial current density exceeding 1 A cm ⁻² . Combining in situ spectroscopy and molecular dynamics simulations, we elucidate that the UiO‐66‐NH ₂ overlayer reconstructs the interfacial hydration structure and promotes the accumulation of hydrated potassium ions (K ⁺ ·H ₂ O) within the electrical double layer. Density functional theory calculations reveal that UiO‐66‐NH ₂ effectively adsorbs K ⁺ ·H ₂ O complexes, leading to preferential interfacial accumulation of this hydrated cation. Crucially, these hydrated cations function as superior proton donors compared to bulk water, significantly lowering the activation barrier for the rate‐determining ^* NO ₃ to ^* NHO ₃ step. This work highlights the interfacial hydration microenvironment in modulating proton‐coupled electron transfer, and provides a generalizable design paradigm for efficient electrosynthesis through microenvironment engineering.