Ambient electrochemical nitrogen fixation is a promising and environmentally benign route for producing sustainable ammonia, but has been limited by the poor performance of existing catalysts that promote the balanced chemisorption of N and subsequent electrochemical activation and hydrogenation. Herein, we describe the highly selective and efficient electrohydrogenation of nitrogen to ammonia using a hollow nanorod-based hierarchically graphitic carbon electrocatalyst with abundant atomically dispersed Mn sites. We discovered that the electron interactions strengthen the interfacial binding between nitrogen and active Mn Lewis acidic hotspots. The Lewis acid–base interactions promote the chemisorption and lock up nitrogen on the active sites and suppress proton adsorption. The proton-coupled electron transfer cleavage of the nitrogen triple bond through an associative mechanism was confirmed under lower overpotential, which delivered high ammonia yield of 67.5 μg h mg and Faradaic efficiency of 13.7% at −0.25 V versus the reversible hydrogen electrode, along with ∼100% selectivity and significantly enhanced electrochemical stability (about 88.8% current retention over 50 h potentiostatic test) under mild conditions. Our strategy is versatile to tailor the nitrogen fixation performance of single-atom catalysts with atomic accuracy.