Despite　encouraging　progress　in　electrocatalytic　nitrogen　reduction　reaction　(NRR)　catalyst　development,　efficient　NRR　has　proven　extremely　challenging　to　achieve　in　practice,　underscoring　the　fact　that　N2is　a　highly　stable,　non-polar　molecule.　Hence,　discovering　electrocatalysts　with　considerable　yields　for　NRR　is　highly　desired.　In　this　work,　combining　the　state-of-the-art　ab　initio　molecular　dynamics　and　the　computational　standard　hydrogen　electrode　method,　we　studied　the　thermodynamics　and　kinetics　of　NRR　on　Fex@MoS2(x　=　1-3)　electrocatalysts　under　an　applied　electrochemical　environment.　NH2-NH2was　determined　to　be　an　important　intermediate,　and　its　N-N　bond　breaking　was　proposed　as　the　rate-determining　step.　On　Fe1@MoS2,　we　demonstrated　that　the　NRR　activity　of　Fe1@MoS2can　be　attributed　to　the　electric　field　effect,　which　triggers　the　dynamical　orientation　of　NH2-NH2from　side-on　adsorption　mode　to　end-on　one.　The　induced　interaction　between　the　dipole　moment　of　the　titled　N-N　bond　with　the　local　electric　field　facilitates　the　N-N　bond　cleavage.　On　the　contrary,　such　an　electric　field　effect　on　Fe2@MoS2and　Fe3@MoS2is　minor.　Two　Fe　sites　synergistically　interacting　with　NH2-NH2leads　to　more　efficient　N-N　bond　activation　than　Fe1@MoS2.　This　work　not　only　illuminates　the　NRR　activity　origin　of　single,　double,　and　triple　Fe　sites　supported　by　MoS2but　also　proposes　two　valuable　strategies　from　the　perspective　of　kinetics　to　accelerate　the　catalysis　of　NRR:　one　is　by　the　electric　field　effect,　the　other　is　to　use　the　synergistic　effect.　©　2022　American　Chemical　Society.　All　rights　reserved.