Interface Reconstruction Induced by Rare-Earth Incorporation Stabilizes High-Coordination Cu ⁺ Sites for Efficient Electrochemical Nitrate Reduction to Ammonia

The electrochemical nitrate reduction reaction (eNO 3 – RR) represents a promising route for simultaneous wastewater treatment and sustainable ammonia synthesis. While Cu 2 O catalysts featuring electron-deficient Cu + sites have been widely studied for eNO 3 – RR, their practical implementation is hindered by self-reduction and structural instability. Constructing Cu–O–M interfacial sites, which enhance charge transfer and stabilize catalytic sites, presents an effective strategy for addressing these challenges. Here, we report a La incorporation strategy to create Cu 2 O–La y O heterointerfaces (Cu 1 La 4 ) for highly efficient conversion of NH 3 . Experimental and theoretical studies indicate that the high-coordinated Cu + active sites at the Cu 2 O/La 2 O 2 (CO 3 ) interface, together with the steric hindrance introduced by La incorporation, optimize the adsorption energy of key intermediates, thereby circumventing the high energy barrier associated with the *NH 3 →NH 3 transition on traditional low-coordination Cu + sites. Furthermore, the covalent Cu–O–La interfacial bonding inhibits Cu + reduction and stabilizes the catalytic system. The optimized Cu 1 La 4 catalyst demonstrates outstanding eNO 3 – RR performance, achieving a Faradaic efficiency (FE) of 94% at –0.6 V and an NH 3 yield rate of 234 μmol h –1 cm –2 . Significantly, the Cu 1 La 4 catalyst exhibited exceptional stability in a membrane electrode assembly (MEA), sustaining ∼7.8 mg h –1 cm –2 NH 3 production and high FE of ∼85% over 150 h at 400 mA.