Abstract: Copper-based catalysts have garnered wide attention in the field of electrocatalytic nitrate reduction for ammonia production due to their low hydrogen precipitation activity and high ammonia selectivity. However, they still face challenges pertaining of poor stability and low activity, which hinder their further application. Herein, we present a Cu₂O/Cu heterojunction catalyst supported on nitrogen-doped porous carbon for nitrate reduction. High resolution transmission electron microscopy (HRTEM) and X-ray Diffraction (XRD) results confirm the presence of Cu₂O/Cu heterojunctions, which serve as an active phase in catalysis. The nitrogen-doped porous carbon as a carrier not only enhances the catalyst’s stability, but also facilitates the exposure and dispersion of active sites. At −1.29 V (vs. RHE), the maximum production rate of ammonia reaches 8.8 mg/(mg·h) with a Faradaic efficiency of 92.8%. This study also elucidates the effect of Cu₂O-to-Cu ratio in the heterojunction on catalytic performance, thereby providing valuable insights for designing efficient nitrate reduction catalysts for ammonia production.