Effect of boron and nitrogen modulation in metal atoms anchoring on flower-like carbon superstructure for efficient ammonia electrosynthesis

Electrocatalytic nitrogen reduction reaction (NRR) is regarded as an ideal alternative technology to the conventional ammonia synthesis. The best way to improve the yield and Faraday efficiency (FE) of the electrocatalytic NRR is the development of low-cost, stable, and efficient catalysts. Herein, a boron-based Zn-metal–organic framework is used to prepare metal atoms (Fe) anchored on B/N co-doped carbon (Fe-B/N-C) as efficient NRR catalysts. Fe-B/N-C shows an excellent NRR performance (with the maximum ammonia yield of 100.1 μg·h−1·mgcat-1 and the maximum FE of 23.0%), which are superior to most of the reported NRR catalysts. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray absorption fine structure spectroscopy (XAFS) demonstrate that Fe atoms can achieve an atomic-level dispersion on the flower cluster-like superstructure and coordinate with N atoms to form Fe-N sites. Theoretical calculations show that in the Fe-N4-B, the boron atom in the substrate can reduce the energy barrier of both the nitrogen activation and the rate-determining step (RDS) of NRR, and the distal pathway of association mechanism is more favorable. This work provides a new insight into the effect of dual-atom doping on the NRR process and kinetics, which is important to the development of high-performance NRR catalysts.