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

Abstract

Electrochemical nitrate reduction to ammonia (NO3−RR) presents dual opportunities for sustainable ammonia synthesis and environmental nitrate remediation. However, the catalytic efficiency of the NO3−RR is hindered by the slow kinetics and substantial side reactions. Herein, a crystal‐amorphous (c‐a) heterostructure catalyst, c‐Co3O4/a‐CuO is reported, that delivers an NH3 yield rate of 412.5 µmol h−1 mg−1 and a Faradaic efficiency of 90% at−0.8 VRHE in neutral electrolyte. Specifically, the catalyst operates via a tandem catalysis pathway: a‐CuO facilitates the initial adsorption and deoxygenation of NO3− to promote *NO2 formation, while the resulting *NO2 species are subsequently converted to NH3 at the c‐Co3O4 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‐Co3O4/a‐CuO into a Zn‐NO3− battery demonstrates simultaneous environmental remediation, energy storage, and sustainable NH3 synthesis.