Atomization energy approach to the quantitative evaluation of catalytic activities of metal oxides during dehydrogenation of MgH₂

The hydrogen desorption reaction of magnesium hydride (MgH₂), MgH₂ Mg + H₂, is accelerated by mixing catalytic metal oxides (e.g., Nb₂O₅). This catalytic effect is evaluated quantitatively using the atomization energy concept. The measured hydrogen desorption rate increases monotonously with increasing y × ΔE _O values of metal oxides, M_xO_y. Here, ΔE_O, is the atomization energy for the oxide ion in M _xO_y. This indicates that the oxide ion interacts mainly with hydrogen atom in MgH₂, in agreement with the observation of the O-H stretching mode in the FT-IR spectra during the dehydrogenation of the Nb₂O₅-catalyzed MgH₂. This approach is also proved to be useful for the catalytic analysis of metal chlorides (e.g., TiCl₃) on the decomposition reaction of NaAlH₄ expressed as, NaAlH₄ (1/3)Na₃AlH₆ + (2/3)Al + H ₂.