The　industrial　synthesis　of　ammonia　(NH3)　using　Fe-based　derived　catalysts　requires　harsh　reaction　conditions　(400-600　degrees　C,　20-40　MPa).　It　is　desirable　to　develop　catalysts　that　perform　well　at　low　temperature　and　pressure　(＜400　degrees　C,　＜2　MPa).　The　main　challenge　of　low-temperature　NH3　synthesis　is　the　dissociation　of　the　extremely　stable　N　N　triple　bond　(945　kJ/mol).　Herein,　the　N-doped　C-supported　Co　catalyst　was　demonstrated　to　be　active　and　efficient　for　NH3　synthesis　under　mild　conditions,　resulting　from　the　hybridization　of　the　d　orbitals　of　Co　with　p　orbitals　of　nitrogen　for　Co-N　coordination.　The　doping　of　N　has　three　relevant　effects.　The　first　is　the　size　decrease　in　Co　nanoparticles.　It　is　proven　by　in　situ　X-ray　photoelectron　spectroscopy　and　synchrotron-based　X-ray　absorption　near-edge　structure　and　extended　X-ray　absorption　fine　structure　analyses　coupled　with　density　functional　theory　calculation　that　there　is　strong　electron　transfer　from　the　doped　N　to　Co.　Hence,　the　second　effect　of　N　doping　is　the　increase　in　electronic　state　of　Co　d　orbitals　which　promotes　the　donation　of　3d　electrons　from　Co　to　the　pi*　orbital　of　N-2,　leading　to　a　decrease　in　activation　energy　for　the　N-2　molecule.　The　third　is　the　involvement　of　nitrogen　vacancies.　The　pyridine　N　weakly　coordinated　with　highly　dispersed　Co　reacts　with　adsorbed　H-2　to　form　NH3,　simultaneously　generating　N　vacancies;　then,　the　consumed　N　species　can　be　replenished　via　N-2　adsorption　on　vacancy　sites.　These　factors　contribute　to　the　superiority　of　the　N-doped　carbon-supported　Co-based　catalyst,　which　achieves　an　NH3　production　rate　of　1.59　mmol(NH3).g(cat)(-1).h(-1)　at　even　250　degrees　C　and　1　MPa.