Boosting Electroreduction Kinetics of Nitrogen to Ammonia via Tuning Electron Distribution of Single-Atomic Iron Sites

Electrocatalytic nitrogen reduction reaction (NRR) plays a vital role for next-generation electrochemical energy conversion technologies. However, the NRR kinetics is still limited by the sluggish hydrogenation process on noble-metal-free electrocatalyst. Herein, we report the rational design and synthesis of a hybrid catalyst with atomic iron sites anchored on a N,O-doped porous carbon (Fe-SA-NO-C) matrix of an inverse opal structure, leading to a remarkably high NH3 yield rate of 31.9 mu gNH3 h(-1) mg(cat.)(-1) and Faradaic efficiency of 11.8 % at -0.4 V for NRR electrocatalysis, outperformed almost all previously reported atomically dispersed metal-nitrogen-carbon catalysts. Theoretical calculations revealed that the observed high NRR catalytic activity for the Fe-SA-NO-C catalyst stemmed mainly from the optimized charge-transfer between the adjacent O and Fe atoms homogenously distributed on the porous carbon support, which could not only significantly facilitate the transportation of N-2 and ions but also effectively decrease the binding energy between the isolated Fe atom and *N-2 intermediate and the thermodynamic Gibbs free energy of the rate-determining step (*N-2 -> *NNH).

Automated summary

This study presents a hybrid catalyst with atomic iron sites anchored on a N,O-doped porous carbon matrix, demonstrating enhanced efficiency and yield for nitrogen reduction reaction.