Development　of　the　cost-effective　catalysts　with　excellent　catalytic　performance　is　highly　demanded　for　ammonia　synthesis,　and　the　strong　adsorption　of　ammonia　greatly　hinders　the　design　of　cost-effective　and　high-performance　ammonia　synthesis　catalysts.　Herein,　we　report　that　the　addition　of　a　small　amount　of　Co　species　(0.1　wt%)　into　Mo2C　catalyst,　which　can　provide　electrons　to　Mo2C,　not　only　leads　to　improvement　of　the　adsorption　and　migration　of　hydrogen,　but　also　facilitates　the　adsorption　and　desorption　of　ammonia.　Consequently,　Mo2C　catalyst　with　0.1　wt%Co　offers　a　40%　higher　ammonia　synthesis　activity　and　a　lower　negative　reaction　order　with　respect　to　NH3　in　comparison　to　Mo2C.　This　work　stresses　the　importance　of　the　minor　components　in　improving　the　ammonia　synthesis　activity　by　accelerating　the　migration　of　reactants　over　the　catalyst　surface　and　the　escape　of　products　from　the　catalyst.