Thermodynamics on Ammonia Absorption of Metal Halides and Borohydrides

Ammonia absorption properties of metal halides and borohydrides were systematically investigated by pressure–composition isothermal measurements. By systematical research, we clarified that the plateau pressure is strongly correlated with the electronegativity of cation or anion in the metal halides or borohydrides. The material with higher electronegativity of the cation showed lower plateau pressure on the ammonia absorption. For the anion, the opposite trend between the electronegativity and plateau pressure was found. With respect to sodium borohydride, the changes of standard enthalpy and entropy corresponding to the ammonia absorption were estimated to be −29 kJ/mol and −98 J/(mol K).