The development of new catalysts with high selectivity and efficiency for the electrocatalytic nitrate reduction reaction (NtRR) to produce ammonia (NH ) at room temperature and ambient pressure is still a challenge. Herein, we report a simple growth method for the controlled synthesis of a GDY-MnO heterointerface by selectively anchoring and growing MnO on GDY surfaces. Experimental results show that the incomplete charge-transfer between GDY and Mn atoms at the interface structures largely increases the number of active sites, improves the electrical conductivity, and therefore results in excellent electrocatalytic performance for NH synthesis with a maximum FE of 95.4%, an NH yield rate of 463.4 μmol h cm and high long-term stability in 0.1 M KOH + 0.1 M NO aqueous electrolytes at room temperature and ambient pressure.