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

Abstract

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 μg <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow></mml:mrow> <mml:mrow><mml:mi>NH</mml:mi> <mml:msub><mml:mrow></mml:mrow> <mml:mn>3</mml:mn></mml:msub> </mml:mrow> </mml:msub> </mml:math> h^-1 mg^-1 _cat. 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 N₂ and ions but also effectively decrease the binding energy between the isolated Fe atom and *N₂ intermediate and the thermodynamic Gibbs free energy of the rate-determining step (*N₂ → *NNH).