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 -NO-C) matrix of an inverse opal structure, leading to a remarkably high NH yield rate of 31.9 μg  h  mg 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 -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 and ions but also effectively decrease the binding energy between the isolated Fe atom and *N intermediate and the thermodynamic Gibbs free energy of the rate-determining step (*N → *NNH).