Catalytic effect of niobium oxide on Hydrogen absorption and desorption process for magnesium

Abstract

Hydrogen absorption of magnesium (Mg) catalyzed by 1 mol% niobium oxide (Nb2O5) was demonstrated under the low temperature condition even at - 50°C. The kinetic and thermodynamic properties were examined for MgH2 with and without Nb2O5. By considering the remarkable absorption features at such low-temperature, the essential hydrogen absorption properties were investigated under accurate isothermal conditions. As a result, the activation energy of hydrogen absorption for the catalyzed Mg was evaluated to be 38 kJ-mol-1, which was significantly smaller than that of MgH2 without the catalyst. The kinetic improvement was also found on the hydrogen desorption process. On the other hand, thermodynamic properties were not chanced bv the catalyst. Therefore, the Nb2O5= addition mainly affects the reaction rates between Mg and hydrogen and shows the excellent catalytic effects. © 2013 The Japan Institute of Metals and Materials.