Molecular dynamic simulation of LiH–H2O reactions using the ReaxFF reactive force field

Abstract

The hydrogen storage material Lithium hydride (LiH) has received wide attention due to its high hydrogen density. However, the reaction process of LiH with H2O is complex, and the microscopic mechanism has not been reported. This paper reveals the microscopic mechanism by the ReaxFF reaction force field module of the Amsterdam Modeling Suite (AMS). Combined with Gaussian09 software, the rate constants and energy changes are determined in the reaction course. As a result, LiH reacts with H2O preferentially, forming Li--O bonds and shedding H from Li--H, which collides randomly to generate H2 and H2LiO. As the reaction proceeds, there are by-products H4LiO2, HLiO, HLi2O, and H2Li2O generated. The reaction course of H4LiO2 is a spontaneous exothermic reaction, and the strong chemical bonding force of Li to H prompts the formation of HLiO, HLi2O, and H2Li2O. 100% of H2 comes from the H removed by LiH. Thus, LiH being fully involved in the reaction, the number of H2 produced remains the same.