Comparison of Hydrogen Yield from Ball-Milled and Unmilled Magnesium Hydride in a Batch System Hydrogen Reactor

Abstract

Energy plays a crucial role in the economic development of a nation and its sustenance. In view of the important role of energy to man; energy demand has been on the increase as the human population increases. Interests in solid-state hydrogen generation especially from lightweight metals have increased lately due to high gravimetric and volumetric hydrogen storage/reserve. In this study, effect of ball milling on hydrogen yield was examined by comparing hydrogen generation from unmilled MgH2 and ball-milled MgH2 in a hydrolysis reaction carried out in a batch system hydrogen reactor. Furthermore, the effects of acetic acid concentration and MgH2 weight on hydrogen generation was investigated. The reaction was carried out at 30 °C with three substrates weights 0.2 g, 0.4 g and 0.6 g respectively. Ball-milled MgH2 performed better than unmilled MgH2 by recording higher hydrogen yield when compared to unmilled MgH2 components with a hydrogen yield of about 0.0194 L relative to 0.0131 L using 0.6 g MgH2 obtained in unmilled MgH2. The results from the XRD spectra validates the reduction of crystallite size of ball-milled MgH2 compared to the unmilled MgH2. The crystallite size reduces from an average of 52.4 µm to about 92.25 nm after one-hour ball milling. This development enhances reaction kinetics by increasing the reaction surface area. Similarly, the fracturing of the substrate crystals during ball milling increases the nucleation reaction in the particles thereby increasing the hydrogen release phenomenon.