Solid solution for catalytic ammonia synthesis from nitrogen and hydrogen gases at 50 °C

The lack of efficient catalysts for ammonia synthesis from N 2 and H 2 gases at the lower temperature of ca. 50 °C has been a problem not only for the Haber–Bosch process, but also for ammonia production toward zero CO 2 emissions. Here, we report a new approach for low temperature ammonia synthesis that uses a stable electron-donating heterogeneous catalyst, cubic CaFH, a solid solution of CaF 2 and CaH 2 formed at low temperatures. The catalyst produced ammonia from N 2 and H 2 gases at 50 °C with an extremely small activation energy of 20 kJ mol −1 , which is less than half that for conventional catalysts reported. The catalytic performance can be attributed to the weak ionic bonds between Ca 2+ and H − ions in the solid solution and the facile release of hydrogen atoms from H − sites. Ammonia synthesis via the Haber–Bosch process typically takes place at an elevated temperature in order to achieve a reasonable rate. Here the authors report on a CaFH solid solution with low activation energy for catalytic ammonia synthesis at lower temperatures.