Hydrogen generation via thermochemical decomposition of lithium hydride nano-particle in the presence of water: A temperature-accelerated reactive molecular dynamics and density functional theory based study

Abstract

Understanding the hydrogen generation mechanism at the atomic length scale is critical for evolving clean energy technologies. Lithium hydride (Li–H) is a promising hydrogen storage and generation material due to its high hydrogen content and strong reactivity with water. In this paper, we have studied the formation of Li–H, its thermal stability, and the hydrogen generation during its hydrolysis, using reactive molecular dynamics simulations. Further, we employed density functional theory to obtain energy of frontier molecular orbitals to reveal the mechanisms of hydrogen formation. During hydrolysis of LiH nano-particle, the dissociation of Li–H bonds and the formation of hydrogen is observed by the adsorption of water molecules onto the Li atom of Li–H nano-particle. Further, the effect of Li–H nanoparticle size is examined using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) model, and it is found that smaller nanoparticles show greater reactivity and faster hydrogen formation. Quantum chemical calculations show the reduction in HOMO-LUMO energy gap from 4.863 eV (LiH) to 4.309 eV (LiH + H₂O), indicating increase in the chemical reactivity upon addition of water. In the final step, we have extended our study and observed the evolution of core-shell morphology in Li–H nanoparticles placed in H₂O, CH₄, CH₃OH, NH₃, and H₂S environment at elevated temperature. Our integrated approach offers critical insight into the reaction mechanism and provides a theoretical basis for the design of efficient hydrogen-generating materials in sustainable energy systems.