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.

This paper reports the visual observations of the clathrate hydrate crystal growth and morphology at the interface of aqueous NaCl solutions and a guest-substance liquid. The hydrate crystal growth was visually characterized in the systems of a wide range of NaCl concentrations from 0.035 to 0.264 in mass fraction. The mass fraction 0.035 was corresponding to that of ordinary seawater, and the salt concentration tested was extended up to the saturation level, i.e., 0.264. Cyclopentane was used as the guest substance. Formation and growth of hydrate crystals at the cyclopentane-NaCl solution interface were observed. We visually analyzed the individual hydrate crystals and classified the morphology of the crystals according to ΔT sub at atmospheric pressure. It was found that the size of the individual hydrate crystals decreased with increasing ΔT sub . The results showed that the morphology of the individual hydrate crystals in any NaCl concentration is roughly similar at a given ΔT sub . We also measured the lateral growth rates of the hydrate-film propagation. The hydrate film growth rate decreased with decreasing ΔT sub in any of the systems and decreased with increasing concentration of NaCl at a given ΔT sub .

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