<p>The escalating levels of nitrate (NO₃⁻) from industrial and agricultural activities have caused significant water pollution and eutrophication, threatening ecosystems and human health. Copper-based catalysts are preferred for converting NO₃⁻ to ammonia (NH₃) because of their cost-effectiveness and high NO₃⁻ reduction activity. However, the NO₃⁻ reduction reaction faces the challenge of competing with the hydrogen evolution reaction (HER) and is prone to by-products such as nitrites (NO₂⁻), resulting in low NH₃ yield and poor selectivity. To further convert NO₂⁻ to NH₃ with high Faradaic efficiency (FE), high yield, and high selectivity, we present Zn-doped Cu₂O (Zn/Cu₂O), offering an environmentally friendly substitute for the Haber–Bosch process. The Zn/Cu₂O catalyst, synthesized through electrodeposition and high-temperature calcination, achieves a high FE of NH₃ (90.74%) at -1.2&#xa0;V vs. RHE. The by-product NO₂⁻ production is inhibited with a very low FE of 5.40%. The further incorporation of Au and Pd on the catalyst surface significantly boosts NH₃ yield (1.12&#xa0;mmol&#xa0;h⁻¹&#xa0;cm⁻²), demonstrating the potential for efficient and sustainable electrocatalytic NO₃⁻ reduction.</p>