Abstract
The lack of efficient catalysts for ammonia synthesis from N2 and H2 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 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 N2 and H2 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 Ca2+ and H− ions in the solid solution and the facile release of hydrogen atoms from H− sites.
Highlights
Introduction ofN2-D2Time pure NH3 was ca. 100:80:8, so that each fragment intensity did not exceed the parent intensity
The strong electron donation from Ca2+H–(2–x)e–x to the transition metals (TMs) nanoparticles enhances the cleavage of N2 molecules, which leads to high catalytic performance for ammonia synthesis[14]
A H2-temperature-programmed desorption (TPD) profile for Ru-deposited CaH2 (Ru/CaH2) (Fig. 2a) revealed that the H2 desorption-onset temperature was almost identical to the temperature where the catalytic activity of Ru/CaH2 is lost
Summary
Introduction ofN2-D2Time (min) pure NH3 was ca. 100:80:8, so that each fragment intensity did not exceed the parent intensity. 50 °C would largely enhance the catalytic activity for ammonia synthesis at low-temperature range below 300 °C.
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