Nanostructured Mg for hydrogen production by hydrolysis obtained by MgH2 milling and dehydriding

Abstract

The synthesis, characterization and hydrolysis properties of nanostructured MgH2 and Mg in a 0.6 M MgCl2 aqueous solution are reported. The microstructural properties of commercial MgH2 are modified by mechanical milling without additives under H2 atmosphere for 5 h. The nanostructured Mg is obtained by dehydriding the as-milled MgH2 under vacuum at 355 °C for 2.5 h. The as-milled MgH2 shows average hydrolysis properties with good hydrogen production capacity (1390 mL/g H2) and kinetics (50% of the total yield in 2.3 min). The nanostructured Mg exhibits excellent hydrolysis properties with a high yield (910 mL/g H2), fast kinetics (90% of the total yield in 2.6 min) and practically no effect of a MgO/Mg(OH)2 passivating layer. The hydrolysis properties of both materials are attributed to their morphology and microstructure. The activation energies of the reaction are estimated and the mechanisms are discussed.