Abstract: The disclosure relates to a liquefied ammonia-ammonium composition, also referenced herein as a eurefstic composition. The composition includes ammonia, an ammonium cation, and a halogenated anion, and the composition remains in liquid form at ambient temperatures and pressures. The composition can be formed by contacting gaseous ammonia with a solid halogenated ammonium salt, such as ammonium triflate or ammonium hexafluorophosphate, which absorbs the ammonia to form the liquid eurefstic composition. The eurefstic composition provides a convenient, safe, and ammonia-dense liquid that is easily transportable and safely storable until later use, for example to release and generate ammonia, to be electrolyzed to generate hydrogen gas, etc. The ammonia or hydrogen gas can then be used as a combustion fuel or other energy source.