Hydrogen storage and cycling properties of a vanadium decorated Mg nanoblade array on a Ti coated Si substrate

A 2.25 at.% V decorated Mg nanoblade array has been fabricated by a dynamic shadowing growth technique. It can absorb and desorb hydrogen rapidly at temperatures T > 500 K after activation by one hydrogenation cycling, with low hydrogen absorption activation energy of 35.0 +/- 1.2 kJ/mol H-2 and desorption activation energy of 65.0 +/- 0.3 kJ/mol H-2. The saturated hydrogen content in Mg nanoblades decreases gradually with the number of cyclings, which is mainly caused by the formation and growth of Mg2Si hillock defects at the nanoblade/substrate interface even though a diffusion barrier layer consisting of a 500 nm Ti nanorod array and 500 nm Ti film was deposited between the Mg nanoblades and the Si substrate. The improved hydrogen sorption kinetics is attributed to both the catalytic effect of the V coating and the unique nanoblade morphology with large surface area and small hydrogen diffusion length.