A First-Principles Study of Regulating Spin States of MoSi 2 N 4 Supported Single-Atom Catalysts Via Doping Strategy for Enhancing Electrochemical Nitrogen Fixation Activity.

Regulating the spin states of catalysts to enhance activity is fascinating but challenging. Herein, by using first-principles calculations, single transition-metal (TM) atoms Mo, Re, and Os embedded in nitrogen vacancy of the MoSi 2 N 4 monolayer (TM 1 /V N -MoSi 2 N 4 ) were screened out as potential catalysts for electrochemical nitrogen reduction reaction to ammonia. Our findings suggest that the spin states of these active centers can be precisely and gradually tuned through a simple doping strategy. Additionally, doping one O atom into the Mo 1 /V N -MoSi 2 N 4 system as an example significantly improves catalytic activity. The spin state of Mo 1 transitions from high to intermediate while simultaneously breaking the C 3 v symmetry of the supported atom. These factors synergistically lead to better orbital overlap between the catalyst and intermediates, facilitating subsequent protonation processes and overall catalytic activity. This work provides novel insight into designing, precisely controlling, and revisiting the spin-related catalytic performance in heterogeneous catalysis.