Interfacial Tandem Catalysis Over a CuSn(OH) 6 /Co Heterostructure Enables Efficient Electroreduction of Nitrate to Ammonia

ABSTRACT Electrochemical nitrate reduction reaction (NO 3 − RR) enables sustainable ammonia (NH 3 ) production but is constrained by sluggish kinetics due to the high stability of NO 3 − and insufficient hydrogenation of nitrogenous intermediates, where the initial NO 3 − → NO 2 − conversion is the rate‐determining step (RDS). Herein, we report a CuSn(OH) 6 /Co heterostructure designed via an interfacial tandem‐catalysis strategy to address both the kinetic bottleneck and downstream hydrogenation steps in a coordinated manner. In this architecture, CuSn(OH) 6 activates NO 3 − and then selectively catalyzes its conversion into *NO 2 , thereby overcoming the RDS limitation. Meanwhile, Co nanoparticles promote rapid H 2 O dissociation to generate abundant *H for subsequent hydrogenation reactions. Further investigations reveal that the heterointerface enables efficient directional transfer of *NO 2 intermediate from CuSn(OH) 6 to the Co component, promoting its complete reduction to NH 3 . Benefiting from this spatially and functionally integrated division of catalytic roles, the CuSn(OH) 6 /Co heterostructure exhibits a high NH 3 yield of 64.51 µmol h − 1 mg Cat − 1 and a selectivity of 92.28% at −0.7 V in 0.1 M NaSO 4 containing 10 mM NaNO 3 , outperforming most reported catalysts. This work highlights a tandem‐catalysis strategy that synchronously regulates RDS and hydrogenation pathways for sustainable NH 3 production via NO 3 − RR.