Inspired　by　nitrogenase　which　can　covert　nitrogen　(N2)　to　ammonia　in　mild　condition,　we　designed　a　series　nitrogen　reduction　reaction　(NRR)　catalysts　which　Mo　embedded　on　double　vacancies　graphene　(GR)　with　non-metal　atoms　X　(X　=　C,　N,　B,　P,　S)　doped　(MoX4/GR)　were　used　to　imitate　the　active　center　of　nitrogenase.　By　means　of　density　functional　theory　(DFT)　computations,　it　is　found　that　MoS4/GR　catalyze　NRR　through　alternating　mechanism　possesses　low　limiting　potential　of　−0.29　V　among　designed　systems.　The　high　NRR　activity　of　MoS4/GR　is　attributed　to　its　inherent　properties,　i.e.　the　dz2　orbital　features　which　indicate　stronger　overlap　with　the　empty　p　orbitals　of　N2.　Back-donation　phenomenon　between　Mo　and　N2,　small　work　function　and　excellent　electrical　conductivity　are　beneficial　to　the　electron　transfer.　Our　work　provides　a　model　to　explain　why　Mo　atom　is　coordinated　with　S　atoms　in　the　nitrogenase　rather　than　C,　N,　P,　and　B　which　also　exist　in　the　organism　of　the　nitrogenase.　©　2020　Elsevier　B.V.