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

Nitrate ( NO 3 − ) pollution poses significant threats to water quality and the global nitrogen cycle. The electrochemical NO 3 − reduction reaction (NO 3 RR) emerges as a promising solution for NO 3 − removal and sustainable ammonia (NH 3 ) production. However, it suffers from an insufficient atomic hydrogen (*H) supply and poor nitrite ( NO 2 − ) adsorption at low potentials, which results in restrained NO 3 − -to-NH 3 conversion and notorious 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 (Pd 1 Cu) 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 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% NO 3 − removal, 100% NH 3 selectivity, near-zero NO 2 − accumulation, 94.4% NH 3 Faradaic efficiency, and an NH 3 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.