Herein, we demonstrate the construction of a 1D/2D heterostructure of cobalt phthalocyanine (CoPc)–carbon nitride (C3N4) for electrochemical N2 reduction to NH3. Improved performance originates from the higher exposure of active surface sites. The electrochemical NRR performance showed an NH3 formation rate of 423.8 μg h−1 mgcat−1, a high faradaic efficiency (FE) of 33%, and stability for 20 h. This study provides a new strategy for designing a highly efficient 1D/2D electrocatalytic system for ammonia synthesis. [ABSTRACT FROM AUTHOR]