Synergy of Dual-Atomic Sites and Interfacial Dynamics for 83.7% Selective Hydroxylamine Electrosynthesis

The sustainable synthesis of high-value hydroxylamine (HA) from nitrate waste through the electrocatalytic nitrate reduction reaction (NO₃RR) offers a transformative pathway for upcycling nitrogenous waste and resource recovery. However, achieving high selectivity remains a formidable challenge as the polar *NH₂OH intermediate is prone to strong adsorption on catalytic sites, leading to over-reduction and lowered selectivity. Here, we report an ambidextrous design strategy that synchronizes the atomic configuration of a dual-atomic copper catalyst (DA Cu₂NC) with the interfacial microenvironment of the electrical double layer (EDL). We demonstrate that the DA Cu₂NC architecture fundamentally alters the reaction pathway, imposing a significant energetic barrier to *NH₂OH over-reduction while facilitating its desorption, which is unattainable by its single atom counterpart (SA Cu₁NC). By systematically modulating the EDL dynamics through cation-specific hydration, we identify the rigidity and homogeneity of the interface, quantitatively described by dielectric relaxation descriptors, as a decisive noncovalent factor for NH₂OH selectivity. Under optimized conditions (H₂SO₄/HNO₃ mixed electrolyte), DA Cu₂NC achieves an exceptional Faradaic efficiency of 83.7 ± 1.6% for HA with a yield rate of 7.5 ± 0.11 mg h^-1 mg_cat^-1 at -0.4 V vs RHE. The DA Cu₂NC catalyst demonstrates excellent stability and repeatability, highlighting the promise of dual-atomic site catalysts for selective and efficient HA production through NO₃RR. These findings establish a robust framework for designing highly selective electrocatalytic systems by mastering the interplay between atomic-scale active sites and mesoscale interfacial dynamics.