Sodium anilinide–cyclohexylamide pair: synthesis, characterization, and hydrogen storage properties

Abstract

The lack of efficient hydrogen storage material is one of the bottlenecks for the large-scale implementation of hydrogen energy. Here, a series of new hydrogen storage materials, i.e., anilinide–cyclohexylamide pairs, are proposed via the metallation of an aniline–cyclohexylamine pair. DFT calculations show that the enthalpy change of hydrogen desorption (ΔH_d) can be significantly tuned from 60.0 kJ per mol-H₂ for the pristine aniline–cyclohexylamine pair to 42.2 kJ per mol-H₂ for sodium anilinide–cyclohexylamide and 38.7 kJ per mol-H₂ for potassium anilinide–cyclohexylamide, where an interesting correlation between the electronegativity of the metal and the ΔH_d was observed. Experimentally, the sodium anilinide–cyclohexylamide pair was successfully synthesised with a theoretical hydrogen capacity of 4.9 wt%, and the hydrogenation and dehydrogenation cycle can be achieved at a relatively low temperature of 150 °C in the presence of commercial catalysts, in clear contrast to the pristine aniline–cyclohexylamine pair which undergoes dehydrogenation at elevated temperatures.