The Haber process, also called the Haber–Bosch process, is the main industrial procedure for the production of ammonia.  The German chemists Fritz Haber and Carl Bosch developed it in the first decade of the 20th century. The process converts atmospheric nitrogen (N) to ammonia (NH) by a reaction with hydrogen (H) using an iron metal catalyst under high temperatures and pressures. This reaction is slightly exothermic (i.e. it releases energy), meaning that the reaction is favoured at lower temperatures and higher pressures. It decreases entropy, complicating the process. Hydrogen is produced via steam reforming, followed by an iterative closed cycle to react hydrogen with nitrogen to produce ammonia.
The primary reaction is:
Before the development of the Haber process, it had been difficult to produce ammonia on an industrial scale, because earlier methods, such as the Birkeland–Eyde process and the Frank–Caro process, were too inefficient.