화학공학소재연구정보센터
International Journal of Hydrogen Energy, Vol.44, No.41, 23216-23224, 2019
Stabilization of Ca7Ge-type magnesium compounds by alloying of non-metal elements: A new family material for reversible hydrogen storage applications
A new family material of MgnTMX2 consisted by alloying non-metal element X into the Ca7Ge-type MgnTM (TM = V, Ti, or Nb; X = C, N, O, F, P, S, or Cl; n = 6 for TM = Nb and V or 7 for TM = Ti) to keep its structural stability during the de/hydrogenations was proposed. Formation energy of MgnTMX2 alloys was calculated using density functional theory to clarify the possibility of synthesizing these compounds. Calculations illustrated that compounds with X = F, O, and S satisfy both the thermal stability with negative formation energies and mechanical stability at zero pressure. The hydrogen absorption is proceed in a manner of stepwise, and finally all tetrahedron interstices were filled by 56 hydrogen atoms in the unit cell forming formula hydrides as MgnTMX2H14. It is obvious that the interstice composition plays an important role in hydrogen adsorption performance. The tetrahedral interstices composed by three Mg atoms and one transition metal own more strong ability to capture H atoms than those constituted by four Mg atoms in the initial hydrogenation process Results indicate that new family compound Mg6VO2 could be possibly ideal hydrogen storage materials in terms of dehydrogenation temperature (170 -246 K) and hydrogen storage capacity (similar to 5.81 mass %). (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.