Ammonia is an essential chemical substance with important applications in industrial productions to fabricate fertilizers or serve as a vital energy storage medium [1].The large scale synthesis of ammonia mainly relies on the Haber-Bosch process, where N2 is reduced into NH3 by H2 under 300-500 ℃ and 200-300 atm, over iron or ruthenium-based catalysts.Such extreme conditions require a huge input of energy.About 1.4％ of the energy consumed by mankind every year was invested in this process [2].Moreover, the generation of H2 from steam reforming of natural gas is accompanied by a large emission of greenhouse gas CO2 [1],which will exacerbate global warming.In recent years,electrocatalytic nitrogen reduction reaction (NRR) has been proposed to produce ammonia at ambient conditions, which simulates the biological nitrogen fixation [3].However, it is still far from the practical application due to the low yield rate and Faradaic efficiency (FE) of ammonia, which can be attributed to the in～nsic inertness of N=-N triple bonds.Thus, developing a sustainable and eco-friendly electrocatalytic way to produce ammonia from nitrogen compounds with a relatively low bonding energy is highly desirable [4].