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 degrees C has been a problem not only for the Haber-Bosch process, but also for ammonia production toward zero CO2 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 CaF2 and CaH2 formed at low temperatures. The catalyst produced ammonia from N-2 and H-2 gases at 50 degrees C with an extremely small activation energy of 20kJmol(-1), which is less than half that for conventional catalysts reported. The catalytic performance can be attributed to the weak ionic bonds between Ca2+ 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.