Achieving　green　ammonia　(NH3)　synthesis　requires　developing　effective　catalysts　under　mild　conditions.　However,　the　competitive　adsorption　of　N2　and　H2,　as　well　as　the　strong　binding　of　N-containing　intermediates　on　the　catalyst,　greatly　inhibits　the　active　sites　for　efficient　NH3　synthesis.　Here,　we　constructed　a　series　of　ZrH2-modified　Fe　catalysts　with　dual　active　sites　to　address　these　issues　and　realized　efficient　NH3　synthesis　under　mild　conditions.　Our　study　shows　that　ZrH2　can　not　only　provide　active　sites　for　H2　activation　but　also　transfer　electrons　to　Fe　sites　for　accelerating　N2　activation.　The　interaction　between　Fe　and　ZrH2　over　40ZrH2-Fe　leads　to　a　decrease　in　work　function　and　a　downward　shift　of　the　d-band　center,　which　is　conducive　to　N2　activation　and　NH3　desorption,　respectively.　The　utilization　of　distinct　sites　for　activating　different　reactants　can　avoid　the　competitive　adsorption　of　N2　and　H2,　leading　to　excellent　NH3　synthesis　activity　of　the　40　wt.%　ZrH2-mediated　Fe　catalyst.　As　a　result,　40ZrH2-Fe　exhibits　a　high　NH3　synthesis　rate　of　23.3　mmol　gcat−1　h−1　at　400　°C　and　1　MPa　and　robust　stability　during　100　h　time-on-stream.　©　Science　China　Press　2025.