Hydrogen generation via alcoholysis reaction using ball-milled Mg-based materials

Abstract

An investigation on the hydrogen generation by reacting ball-milled Mg-based materials in different alcoholic solutions (methanol, ethanol, 2-propanol) was performed. The MgH 2 reactivity in methanol is very low (maximum conversion yield < 10 % ) and no improvement is induced by the ball milling treatment. In contrast, the ball milling affects greatly the Mg reactivity in methanol. The Mg powder milled for 30 min displays a maximum conversion yield of 47% compared to 3% for unmilled Mg powder. Its high reactivity is ascribed to the creation of numerous defects and fresh surfaces during the initial stage of the milling process, favoring the corrosion of Mg in methanol. In addition, the presence of water in the methanol solution inhibits drastically the alcoholysis reaction despite its low amount (0.3 vol%). The higher hydrogen production is obtained with the composite Mg-10 at% Ni milled for 30 min leading to a conversion yield of 70% after 45 min of reaction in methanol, which corresponds to a hydrogen gravimetric yield of 4.5 wt% (including Ni mass and excluding methanol mass). The positive effect of Ni addition on the yield and kinetics of the alcoholysis reaction is explained by the creation of micro-galvanic cells between Mg and Ni components. No hydrogen is released from the decomposition of milled Mg powder in ethanol and 2-propanol solutions.