The important role of N2H formation energy for low-temperature ammonia synthesis in an electric field

•Low temperature catalytic ammonia synthesis at 373 K with an electric field has been investigated.•Fe- and Ni-supported catalysts show higher TOF than Ru-supported catalyst in an electric field.•N2 dissociation through the “associative mechanism” plays a key role in the electric field.•The ammonia synthesis activity in the electric field is determined by the N2H formation energy.