Coupled Pd^δ--Cu^δ+ Dipole for Enhanced Aqueous Nitrate Valorization at Ultralow Potentials

Nitrate $\left({\mathrm{NO}}_3^{-}\right)$ pollution poses significant threats to water quality and the global nitrogen cycle. The electrochemical ${\mathrm{NO}}_3^{-}$ reduction reaction (NO₃RR) emerges as a promising solution for ${\mathrm{NO}}_3^{-}$ removal and sustainable ammonia (NH₃) production. However, it suffers from an insufficient atomic hydrogen (*H) supply and poor nitrite $\left({\mathrm{NO}}_2^{-}\right)$ adsorption at low potentials, which results in restrained ${\mathrm{NO}}_3^{-}$-to-NH₃ conversion and notorious ${\mathrm{NO}}_2^{-}$ accumulation. Herein, we propose a dipole strategy that utilizes coupled divergent dual centers (Pd^δ--Cu^δ+) in binder-free monolithic single-atom alloy electrodes (Pd₁Cu) to overcome these challenges at ultralow potentials. In-situ experiments and theoretical simulations reveal that the polarized atomic Pd^δ- dramatically enhances *H supply by facilitating water dissociation into *H, which then readily spills over to the adsorption-strengthened ${\mathrm{NO}}_2^{-}$ on adjacent Cu^δ+, thus promoting rapid deep hydrodeoxygenation at ultralow potentials. Furthermore, the upshifted d-band center inhibits *H self-coupling and reduces the thermodynamic energy barrier for the *NO intermediate hydrogenation. Leveraging these advantages, the coupled Pd^δ--Cu^δ+ dipole achieved 100% ${\mathrm{NO}}_3^{-}$ removal, 100% NH₃ selectivity, near-zero ${\mathrm{NO}}_2^{-}$ accumulation, 94.4% NH₃ Faradaic efficiency, and an NH₃ yield rate of 1.98 mM h^-1 cm^-2 at just -0.2 V vs RHE, outperforming the monometallic counterparts and reported advanced catalysts. The proposed metal-dipole strategy can provide a universal principle for the rational design of electrocatalysts to valorize pollutants into valuable ammonia products.