© 2020, Science China Press and Springer-Verlag GmbH Germany, part of Springer Nature. Ammonia is a key feedstock of fertilizers for farming and convenient hydrogen carrier as an emerging clean fuel, but industrial ammonium production process, Haber-Bosch reaction, is an energy-intensive process, consuming 1%–2% of global energy and producing 3% global CO2. Electrochemical nitrogen reduction reaction (NRR) is one of the most promising routes to realize highly efficient NH3 production under ambient conditions. However, up to now, few precious-metal-free electrocatalysts with desirable catalytic performance have been explored. In this work, Mo2C nanodots anchored on three-dimensional ultrathin macroporous carbon (Mo2C@3DUM-C) framework is developed toward significantly enhanced nitrogen reduction reaction. Thanks to the special structural design of 3D ultrathin macroporous carbon and highly active and stable Mo2C toward N2 electrochemical reduction, the Mo2C@3DUM-C framework exhibits a high Faradaic efficiency of 9.5% for NH3 production at −0.20 V and the yield rate reaches 30.4 µg h−1mgM02C−1. Further electrochemical characterizations reveal the enhanced electron transfer and increased electrochemical surface area in the 3D macroporous carbon framework. Moreover, the Mo2C@3DUM-C electrocatalysts hold high catalytic stability after long-term NRR test. The temperature-dependent yield rate of NH3 demonstrates that the activation energy of nitrogen reduction on the employed catalyst was calculated to be 28.1 kJ mol−1. Our proposed earth-abundant Mo2C@3DUM-C demonstrates an alternative insight into developing efficient and stable nitrogen fixation catalysts in acids as alternatives to noble metal catalysts.