Density functional theory study on thermodynamic oxidative behaviour of the TiFe hydrogen storage alloy

Abstract

TiFe hydrogen storage alloy, composed of Ti and Fe, shows strong potential for hydrogen storage applications. This study uses density functional theory to investigate hydrogen adsorption and surface oxidation behaviors under service conditions. Results reveal that Ti-terminated surfaces, particularly at bridge and hcp sites, exhibit higher hydrogen adsorption energies than Fe-terminated surfaces. Population and electronic structure analyses show that adsorption energy is primarily influenced by the symmetry of the hydrogen position, bonding configuration, and charge transfer, with symmetry and bonding playing dominant roles. For oxidation behavior, simulations at various adsorption sites indicate that the Ti-Ti-Fe triple vacancy offers the highest oxygen adsorption capacity, followed by the Ti-Ti bridge site, while the Fe-Fe bridge site shows the weakest adsorption. These findings enhance understanding of hydrogen adsorption mechanisms and offer guidance for designing improved TiFe-based hydrogen storage materials with enhanced environmental durability.