The effect of various cations/anions for MgH2 hydrolysis reaction

Abstract

MgH2 is regarded as a potential hydrolysis material for the hydrogen generation due to its high theoretical hydrogen yield, abundant source on earth and environmentally friendly hydrolysates. However, the quickly formed passive magnesium hydroxide layer on the surface of MgH2 will hinder its further hydrolysis reaction, leading to sluggish reaction kinetics and low H2 yield. In this paper, we explore the improvement of different anions and cations in solutions for the hydrolysis of MgH2. It is found that the cations in the solution promote the reaction rate of MgH2 hydrolysis through the hydrolysate-induced growth effect, among which the fastest hydrogen yield can get 1664 mL/g within a few minutes in the Fe2(SO4)3 solution. As for the anions, it enables different microstructures of the Mg(OH)2 hydrolysate which give rise to enhanced water utilization. Specially, for the mixed 0.5 M MgCl2 + 0.05 M MgSO4 solution, the water utilization rate attains the optimum value of 51.3 %, much higher than that of the single MgCl2 or MgSO4 solutions. These findings are of great significance for the application of MgH2 hydrolysis as hydrogen generation.