Hydrogen adsorption on alkali and alkaline earth functionalized silicene: A first-principles and kinetic modeling study

Abstract

This study explores hydrogen adsorption in silicene modified through substitutional doping with transition metals (M = Cu, Sn, Ti, V, and Zn) and decorated with alkali or alkaline-earth metals (A = K, Li, and Mg), using first principles within the framework of Density Functional Theory. Substitutions were found to be energetically unfavorable, indicating weak M-silicene interactions. However, the introduction of decorations significantly improved binding energy. K and Li atoms formed stable bonds with .for hydrogen storage under ambient conditions. Ti@K and V@K systems also met the energy criteria but required higher pressures (~100 bar). Moreover, the Ti@Li, V@Li, and Ti@K systems all satisfy the required gravimetric benchmark for hydrogen storage, each providing a maximum capacity of approximately 9 wt%.Density of states analysis revealed strong hybridization between Ti or V and silicene near the Fermi level, while Sn and Mg showed weak interaction. Charge density difference analysis showed localized interaction with hydrogen. Additionally, temperature-programmed desorption (TPD) simulations based on first-order kinetics accurately reproduced desorption peak temperatures and coverage behavior, revealing the strong influence of both dopants and adatoms on hydrogen binding strength. These results provide valuable insight into the thermal stability and adsorption properties of the modified silicene systems. These findings identify Ti@Li, V@Li and Ti@K as promising candidates for hydrogen storage in silicene.