The amount of carbon dioxide emitted by industrial ammonia synthesis is equivalent to 1.4 % of total human emissions . In the Haber-Bosch process, a typical method for industrial ammonia synthesis, Fe-based catalysts have been used for more than 100 years, and the addition of alkali metals enhances their activity . In industrial processes, Fe-based catalysts synthesize ammonia at 400-600°C and 100-300 atm . These severe conditions are due to the very high binding energy of the N2 molecule (945 kJ mol -1 ). Synthesis plants become massive and centralized to produce ammonia more cheaply and in larger quantities for benefits of scale .