Crystalline‐Amorphous Heterostructures with Built‐In Electric Fields Enhance the Tandem Electroreduction of Nitrate to Ammonia

Abstract Electrochemical nitrate reduction to ammonia (NO ₃ ⁻ RR) presents dual opportunities for sustainable ammonia synthesis and environmental nitrate remediation. However, the catalytic efficiency of the NO ₃ ⁻ RR is hindered by the slow kinetics and substantial side reactions. Herein, a crystal‐amorphous (c‐a) heterostructure catalyst, c‐Co ₃ O ₄ /a‐CuO is reported, that delivers an NH ₃ yield rate of 412.5 µmol h ⁻¹ mg ⁻¹ and a Faradaic efficiency of 90% at−0.8 V _RHE in neutral electrolyte. Specifically, the catalyst operates via a tandem catalysis pathway: a‐CuO facilitates the initial adsorption and deoxygenation of NO ₃ ⁻ to promote ^* NO ₂ formation, while the resulting ^* NO ₂ species are subsequently converted to NH ₃ at the c‐Co ₃ O ₄ sites. Structural and spectroscopic analyses further reveal that the c‐a interface induces charge redistribution and built‐in electric fields, accelerating electron transfer and lowering the energy barrier of the rate‐determining step. Moreover, integration of the c‐Co ₃ O ₄ /a‐CuO into a Zn‐NO ₃ ⁻ battery demonstrates simultaneous environmental remediation, energy storage, and sustainable NH ₃ synthesis.