Iron to catalyze ammonia synthesis at low temperature

Abstract Haber-Bosch process produces ammonia to provide food for over 5 billion people; however, it is currently required to reduce the large global CO 2 emissions. It is indispensable to devise heterogeneous catalysts for the synthesis of ammonia below 100‒150 °C to minimize the energy consumption of the process. Here we report metallic iron as a catalyst for ammonia synthesis at 100 °C in combination with an electron-donating material. The iron catalyst revealed that iron can exhibit a few hundred to several thousand times higher efficiency (turnover frequency) for ammonia synthesis than other transition metals used in highly active catalysts. Thermodynamic and vibrational spectroscopic analyses implied that the rate-determining step of ammonia synthesis on the iron catalyst is not N 2 cleavage, but the formation of subsequent N-Hn species such as NH, NH 2 and NH 3 , because of the facile cleavage of N 2 .