Common ion effect in the hydrolysis reaction of Mg[sbnd]Ca alloy hydride-salt composites

Abstract

In this paper, the MgCa alloy hydride (MCH)-salt composites were prepared by ball milling and characterized by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The objective of this work was to investigate the effects of the synthesis parameters, including salt amounts and compositions, on the hydrogen generation performances in terms of conversion rate and kinetics, and thus to improve the hydrolysis property of MCH. It was found that the xMCH-MgCl2 (x = 5, 10, 15 and 20) composites generate less hydrogen than MCH. This abnormal phenomenon may be due to the common ion effect of Mg2+ in the hydrolysis processes. The 10MCH-MgCl2 composite milled for 0.5 h displays the lowest hydrogen yield of 962 mL per gram of the composite at 25 °C, and has slower hydrogen generation rate (692 mL g−1 in 10 min) than MCH (722 mL g−1 in 10 min). At the same conditions, compared with MCH, the xMCH-CaCl2 (x = 5, 10, 15 and 20) composites exhibit better hydrogen generation performances. Especially, 15MCH-CaCl2 has a hydrogen yield of 1141 mL g−1(composite).