First-principles investigation of transition metal doping effects on H2 dissociative adsorption in TiFe-based alloys

Abstract

TiFe alloys are important hydrogen storage materials. This study uses density-functional theory (DFT) to systematically investigate the effects of 3d and 4d transition metals (TMs) (except Tc) on the dissociative adsorption behavior of H₂ on the TiFe (110) surface. Calculations indicate that the optimal adsorption sites for H₂ on the pristine surface are adjacent Fe–Fe bridge sites. Calculations of adsorption energies for pristine and doped surfaces reveal that most transition metal dopants (particularly 4d elements) fail to significantly reduce the adsorption energy of H₂ on the TiFe (110) surface, whereas Co (substituting Fe or Ti sites) and Sc (substituting Ti sites) significantly reduce adsorption energies. Considering both substitution propensity and adsorption performance, the Co substituted Fe and Sc substituted Ti systems demonstrate the greatest application potential. Electronic structure analysis shows that doping with different elements causes different degrees of orbital hybridization and charge redistribution. This is the main reason for the changes in the adsorption capacity of the doped surfaces.