In the Haber's process of the synthesis of ammonia, the use of catalyst helps

Nitrogen from the air is combined with hydrogen to create ammonia in the Haber process. Ammonia is produced exothermically and the reaction is reversible.
Iron is employed as a catalyst in this process.
The catalyst is used to speed up ammonia synthesis while keeping the amount produced constant.

${\mathrm{N}}_2+3{\mathrm{H}}_2\to 2{\mathrm{NH}}_3$