Electrochemical nitric oxide reduction reaction (NORR) to produce ammonia (NH₃) under ambient conditions is a promising alternative to the energy and carbon-intensive Haber–Bosch approach, but its performance is still improved. Herein, molybdenum carbides (MoC) nanocrystals confined by nitrogen-doped carbon nanosheets are first designed as an efficient and durable electrocatalyst for catalyzing the reduction of NO to NH₃ with maximal Faradaic efficiency of 89% ± 2% and a yield rate of 1,350 ± 15 μg·h⁻¹·cm⁻² at the applied potential of −0.8 V vs. reversible hydrogen electrode (RHE) as well as high stable activity with negligible current density and NH₃ yield rate decays over a 30 h continue the test. Moreover, as a proof-of-concept of Zn–NO battery, it achieves a peak power density of 1.8 mW·cm⁻² and a large NH₃ yield rate of 782 ± 10 μg·h⁻¹·cm⁻², which are comparable to the best-reported results. Theoretical calculations reveal that the MoC(111) has a strong electronic interaction with NO molecules and thus lowering the energy barrier of the potential-determining step and suppressing hydrogen evolution kinetics. This work suggests that Mo-based materials are a powerful platform providing great opportunities to explore highly selective and active catalysts for NH₃ production.