The　desire　of　green　ammonia　(NH3)　production　requires　efficient　catalysts　that　could　operate　at　mild　conditions.　However,　the　activity　of　catalysts　is　restricted　by　scaling　relation　that　low　activation　energy　of　N-2　is　in　conjunction　with　the　over-strong　affinity　of　intermediates,　which　blocks　adsorption　sites　of　catalyst　and　hinders　NH3　production.　Single　atom　alloy　(SAA)　is　an　efficient　approach　to　circumvent　this　relation.　In　the　present　work,　we　offer　a　feasible　strategy　of　preparing　M1Ru　(M　=　Fe,　Co,　Ni)　SAA.　Our　studies　show　that　Co1Ru　SAA　has　the　highest　NH3　synthesis　rate　and　the　largest　TOFRu　value　among　M1Ru　SAA.　Compared　with　CoRu　nanoparticle　alloy　(NPA),　Co1Ru　SAA　has　stronger　electronic　interaction　between　Co　and　Ru,　which　induces　lower　work　function　and　up-shift　d　band　center　toward　Fermi　level　for　Co1Ru　SAA,　thus　promoting　N-2　activation.　Meanwhile,　the　unique　SAA　structure　could　effectively　tune　N-2　activation　pathway.　Those　findings　make　a　contribution　to　the　development　of　advanced　catalysts　for　efficient　NH3　synthesis　at　mild　conditions.　(C)　2021　Elsevier　Inc.　All　rights　reserved.