Site-resolved hydrogen adsorption on TiFe nanoparticle surfaces and slab models: sequential H2 loading, electronic structure, and thermodynamic screening

TiFe intermetallics are attractive solid-state hydrogen storage materials, but the atomistic role of nanoscale morphology in H 2 adsorption and release remains unclear. Here, self-consistent-charge density-functional tight-binding calculations were used to study H 2 adsorption on a 65-atom TiFe nanoparticle Ti 33 Fe 32 , benchmarked against TiFe(100) and TiFe(110) slabs. Screening of 134 nanoparticle adsorption minima shows that Fe-containing bridge, hollow-like, and top motifs form a moderate-binding molecular H 2 adsorption class, whereas Ti-top sites form a weaker-binding class. Sequential loading up to 48H 2 molecules gives a calculated surface-adsorption upper bound of 2.79 wt% H 2 for the isolated 65-atom nanoparticle model. Molecular H 2 is largely preserved on the nanoparticle, whereas TiFe(100) favors dissociation, with a dissociative preference (ΔE) as low as −2.25 eV. Electronic analysis links this contrast to reduced charge transfer and weaker metal–H hybridization on the nanoparticle. Langmuir–van't Hoff screening identifies Ti-top sites favorable for near-ambient release, providing design guidance for TiFe-based hydrogen storage materials.