The Basic Property Solution Properties And Theoretical Mechanism Of Dehydrogenating Of LiNH₂

With large storage of hydrogen, lower price and lighter weight, LiNH2 is regarded as one of the most promising hydrogen-storing materials. But its application is limited for its high generated temperatures and low speeds in adsorbing and releasing hydrogen. Researches have made many fruitful to improve the thermodynamics of LiNH2 in absorbing and releasing hydrogen, but few on the mechanism. In order to develop LiNH2 into a practical hydrogen-storing material, we established the correspondence between micro physics, like formation heat, substitutional solution heat and dissociation energy of hydrogen with macro performances like Structural stability and dehydrogenation of alloys based on same experiments on the replaceable parts, acquired micro physical properties and electronic structure information of LiNH2 through first-principles calculations, then researched Alloying effect of Mg, Al, Ti and Nb on dehydrogenation by replacing the Li atom in LiNH2 with these atoms, and explored the catalytic mechanism of dehydrogenation of LiNH2 systems based on the analysis on electronic mechanism.The equilibrium lattice constant, formation heat, electronic density of states, electron density and H atom dissociation energy of LiNH2 phase are calculated in this paper. The fairly good agreement between theoretical and experimental results shone that the present calculations are highly reliable.When formation heat was a minus value, the negative alloy formations generate larger heats and dehydrogenation of LiNH2 was difficult. In a LiNH2 alloy system, the Li-NH bond existed in the form of ionic bonds while the N-H bond was covalent, the violent formation was one of the reason for difficult dehydrogenation of LiNH2. The mix of LiNH2 and LiH dehydrogenated more easily than the Li2NH and LiH mix.The equilibrium lattice constant, formation heat, electronic density of states, electron density and H atom dissociation energy of LiNH2 are also calculated. When substituting the Li atom with Mg, Al, Ti, or Nb showed that in minor substitution by alloying elements (like Mg, Ti, or Nb), Nb's energy consumption was maximum while Al minimum, and the difficulty sequence is Nb, Ti, Mg, Al; heat generated by the negative alloy was comparatively less after the alloying of LiNH2, which showed stability was decreasing and alloying enhanced dehydrogenation capacity of the system; absolute heat generated in alloying deceased in the Nb, Ti, Mg, Al order, which showed dehydrogenation performance of alloying elements decreases in the Al, Mg, Ti, Nb sequence. The reason that these alloying elements enhanced the dehydrogenation performance of LiNH2 systems is that alloying weakens the interaction between Li and NH.