Investigation of hydrolysis properties of MgH2 in different anionic/cationic salt solutions

Abstract

MgH2 is a promising metal hydride for high-density hydrogen storage, offering advantages such as operational safety, high hydrogen yield, and cost-effectiveness in hydrolysis-based hydrogen generation. However, challenges persist in this field, including reaction interruption caused by the formation of passivating layers and sluggish kinetics. In this study, MgH2 hydrolysis experiments were conducted, utilizing various solutions including 1 M AlCl3, Al2(SO4)3, Al(NO3)3, NiCl2, NiSO4, Ni(NO3)2, FeCl3, Fe2(SO4)3, and Fe(NO3)3 at different temperatures. The resulting hydrolysis products were analyzed using X-ray diffraction and scanning electron microscopy to examine their phases and morphology. Through comprehensive analysis of the hydrolysis mechanism and kinetics, chloride ion solutions were identified as highly efficient, demonstrating excellent rates and yields. Notably, AlCl3, NiCl2, and FeCl3 outperformed other solutions, exhibiting kinetic performance with hydrolysis activation energies of 17.3 ± 1.7, 24.2 ± 1.3, and 14.7 ± 1.7 kJ/mol, respectively. Furthermore, we extended our investigation to compare the hydrolysis effects of different cations, incorporating MnCl2, CoCl2, and CuCl2. Mechanistic analysis pinpointed Al3+ and Fe3+ as catalysts with exceptional hydrolysis performance and remarkable kinetic properties. The aforementioned remarkable MgH2 hydrolysis properties are of significant interest for investigating the corresponding Mg-based alloy hydrides, which are worthwhile to consider.