Non-isothermal synergetic catalytic effect of TiF3 and Nb2O5 on dehydrogenation high-energy ball milled MgH2

Abstract

MgH2-M (M = TiF3 or Nb2O5 or both of them) composites prepared by high-energy ball milling are used in this work to illustrate the dehydrogenation behavior of MgH2 with the addition of catalysts. The phase compositions, microstructures, particle morphologies and distributions of MgH2 with catalysts have been evaluated. The non-isothermal synergetic catalytic-dehydrogenation effect of TiF3 and Nb2O5 evaluated by differential scanning calorimetry gives the evidences that the addition of catalysts is an effective strategy to destabilize MgH2 and reduce hydrogen desorption temperatures and activation energies. Depending on additives, the desorption peak temperatures of catalyzed MgH2 reduce from 417 °C to 341 °C for TiF3 and from 417 °C to 336 °C for Nb2O5, respectively. The desorption peak temperature reaches as low as 310 °C for MgH2 catalyzed by TiF3 coupling with Nb2O5. The non-isothermal synergetic catalytic effect of TiF3 and Nb2O5 is mainly attributed to electronic exchange reactions with hydrogen molecules, which improve the recombination of hydrogen atoms during dehydrogenation process of MgH2.