The role of differently distributed vanadium nanocatalyst in the hydrogen storage of magnesium nanostructures

Using a glancing angle (co)deposition technique, similar to 4.6 at.% V has been coated on the surface of individual Mg nanoblades and doped into Mg nanostructures fabricated at different deposition angles. The hydrogen storage properties of the formed V-decorated and V-doped Mg nanostructures depend strongly on how the nanocatalyst V is surrounded by the host Mg. The V-doped Mg sample has lower activation energies for hydrogen absorption (E-a(a) =35.3 +/- 0.9 kJ/molH(2)) and hydrogen desorption (E-a(d) = 38.9 +/- 0.3 kJ/mol H-2) than the V-decorated Mg sample when deposited at the same deposition angle of theta = 70 degrees. The activation energies of the doped samples increase gradually with the decrease of the theta angle. We also find that the porosity of the Mg nanostructures plays a secondary role. A phenomenological model based on a heterogeneous reaction is proposed to explain the different hydrogen desorption activation energies obtained for different V-Mg nanostructured samples. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.