Facile ammonia synthesis from electrocatalytic N2 reduction, which overcomes the high temperature and pressure required for industrial ammonia synthesis method, is highly desirable for many fields such as agriculture and carbon-free energy. However, electrochemical N2 fixation suffers from slow kinetics and low efficiency due to the difficulty of N2 adsorption and dissociation. Here, N-doped porous carbon (NPC) and Co single atoms embedded NPC (CSA/NPC) were reported as active electrocatalysts for electrochemical reduction of N2 to NH3 at room temperature and atmospheric pressure. The N content and species of NPC were tuned to enhance N2 chemical adsorption and N≡N cleavage. The resulting NPC rapidly converted N2 to NH3 with NH3 production rate of 1.40 mmol g−1 h−1 at −0.9 V vs RHE, which overcame the limitation of low NH3 yield for current electrocatalysts. Experiments combined with DFT calculations revealed pyridinic and pyrrolic N were active sites for NH3 synthesis, and the energy-favorable pathway for NH3 synthesis was *N≡N → *NH=NH → *NH2−NH2 → 2NH3. When Co single atoms were introduced to NPC, CSA/NPC exhibited much more positive potential (−0.2 V vs RHE) and higher Faradic efficiency for NH3 production, which could be attributed to that Co single atoms can provide active sites for N2 adsorption and dissociation.

Electrochemical reduction of N2 to ammonia under ambient conditions on N-doped porous carbon

256th National Meeting (2018)

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