Synergetic effect of Ni and Nb2O5 on dehydrogenation properties of nanostructured MgH2 synthesized by high-energy mechanical alloying

Abstract

abstract Nanostructured MgH 2 -Ni/Nb 2 O 5 nanocomposite was synthesized by high-energymechanical alloying. The effect of MgH 2 structure, i.e. crystallite size and lattice strain, andthe presence of 0.5 mol% Ni and Nb 2 O 5 on the hydrogen-desorption kinetics was investi-gated. It is shown that the dehydrogenation temperature of MgH 2 decreases from 426 Cto327 C after 4 h mechanical alloying. Here, the average crystallite size and accumulatedlattice strain are 20 nm and 0.9%, respectively. Further improvement in the hydrogendesorption is attained in the presence of Ni and Nb 2 O 5 , i.e. the dehydrogenation temper-ature of MgH 2 /Ni and MgH 2 /Nb 2 O 5 is measured to be 230 C and 220 C, respectively.Meanwhile, the dehydrogenation starts at 200 C in MgH 2 –Ni/Nb 2 O 5 system, revealingsynergetic effect of Ni and Nb 2 O 5 . The mechanism of the catalytic effect is presented.a 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved. 1. Introduction Due to a series of special characteristics of hydrogen storagein metals such as high capacity, light weight, low environ-mental impact, low cost and high natural abundance, manymetal–hydrogen systems have been studied for mobilehydrogen storage application. Critical reviews on metalhydridesforsolidhydrogenstoragecanbe foundinreferences[1,2]. Among various metals, magnesium is considered as oneof the most promising candidate, mainly due to its highstorage capacity (7.6 wt% in MgH