The electrocatalytic nitrate reduction reaction (NO₃⁻RR) holds significant research value for sustainable ammonia synthesis and wastewater treatment. Despite the low cost of iron and its good ammonia synthesis performance, issues such as particle aggregation, slow kinetics, and poor stability limit the selectivity for ammonia and overall reaction efficiency, hindering large-scale application of catalysts. In this study, an amorphous/crystalline dual-phase (a-Fe/Cu) catalyst was synthesized via ultrasonic process, achieving a highly efficient electrocatalyst for ammonia synthesis. The a-Fe/Cu catalyst achieved high ammonia yield rate of 4.67 mol·g⁻¹·h⁻¹ with a Faraday efficiency (FE) of up to 93.48% at −0.5 V vs. reversible hydrogen electrode (RHE). In situ analyses demonstrated that the presence of amorphous Fe facilitates interfacial water activation, dissociation and dynamic equilibrium between the production of *H and its prompt consumption by nitrogen intermediates resulting in an enhanced ammonia yield with high Faradaic efficiency. The synergistic interaction between c-Cu and a-Fe optimizes the electronic structure of the catalyst, enhancing the adsorption of nitrate, reaction intermediates, and facilitates efficient electron transfer, thus improving overall electrocatalytic reaction performance. Furthermore, the integration of the catalyst into a Zn-based battery configuration demonstrates its potential applicability in the fields of energy conversion and storage technologies.