Interfacial water engineering via amorphous-crystalline hybrids for neutral nitrate electroreduction to ammonia

The electrocatalytic nitrate reduction reaction (NO 3 RR) represents a viable strategy for achieving neutral nitrate-to-ammonia conversion to satisfy the global nitrogen balance. However, the competitive hydrogen evolution reaction (HER) and the intrinsic sluggish nine protons/eight electrons transfer kinetics necessitate the high energy consumption, restricting the practical viability of electrochemical NO 3 RR technology. Here, we report an amorphous-crystalline heterophase catalyst (aCoO-cCu 2 O-PM) to spatially coordinate proton generation and consumption via interfacial water regulation, effectively decoupling HER and achieving admirable NO 3 RR performance. aCoO-cCu 2 O-PM achieves a high NH 3 Faradaic efficiency of 96.02 % with a yield of 14.16 mg·h −1 ·mg cat. −1 at −0.7 V. The ex situ/in situ technologies concurrently show that the crystalline Cu 2 O phase activates nitrate and promotes the dissociation of interfacial 2-coordinated hydrogen-bonded water to generate active *H, and the amorphous CoO phase establishes dynamic proton transfer channels. The computational results further show that the heterointerface of aCoO-cCu 2 O-PM spatially isolates *H production (Cu 2 O) and utilization (CoO), suppressing HER by optimizing *H flux matching and achieving rapid NO 3 RR kinetics. The constructed Zn-NO 3 ⁻ batteries based on aCoO-cCu 2 O-PM cathodes attain a power density of 23.36 mW·cm −2 while purifying nitrate-contaminated wastewater. Our results suggest that amorphous-crystalline hybrid structures are feasible to engineer interfacial water structures for efficient neutral NO 3 RR. The amorphous CoO/crystalline Cu 2 O heterointerface activates nitrate and dissociates interfacial 2-coordinated water into active *H on Cu 2 O, while CoO stabilizes intermediates via *H transfer, suppressing HER. This synergy enables efficient NH 3 production, and the Zn-NO 3 ⁻ battery facilitates nitrate-to-ammonia conversion in wastewater purification. • Amorphous-crystalline hybrid enables interfacial water dissociation for neutral NO 3 RR. • Achieves NH 3 FE of 96.02 % with a yield of 14.16 mg·h −1 ·mg cat. −1 at −0.7 V. • Crystalline Cu 2 O activates NO 3 ⁻/H 2 O while amorphous CoO creates active H channels. • Zn-NO 3 ⁻ delivers 23.36 mW·cm⁻ 2 with simultaneous water purification.