First-Principles Investigation of Hydrogen Adsorption and Exploratory Dissociation Pathways on Transition-Metal-Doped TiFe(111) Surfaces

TiFe-based alloys offer reversible hydrogen storage, but adsorption strength alone does not determine surface activation. Spin-polarized density functional theory was used to examine Sc, V, Cr, Mn, Co, and Ni substitution in the third atomic plane of Ti- and Fe-terminated TiFe(111) slabs. Adsorption and hydrogen-free electronic-structure calculations used PBE without a dispersion correction; separately prepared dissociation profiles used ordinary PBE nudged elastic band (NEB) calculations. The substituted Ti-face configurations retain molecular hydrogen at −0.023 to −0.161 eV. On the Fe face, Mn yields two separate H atoms at −1.838 eV per incident H2, Cr and Sc elongate the molecule (0.863 and 0.831 Å), and Co, Ni, and V change it by less than 0.03 Å; several Fe-face energies include a change in the slab’s magnetic state. Only the Ti/Cr band met the force criterion, under additional lateral hydrogen constraints; the other eleven bands remained unconverged. Their sampled heights therefore do not establish a quantitative dissociation-barrier ranking. Metal-projected spectra and Bader charges provide electronic context without establishing a hydrogen-orbital mechanism. The results distinguish configuration-specific binding, molecular distortion, and exploratory pathway information; they do not identify a universal optimum additive for practical hydrogen uptake or release.