Tuning TiFe doped with Mn and V for enhanced hydrogen storage: Experiments and DFT insights

Hydrogen storage in TiFe-based alloys has attracted renewed interest owing to their elemental abundance, reversible hydrogenation behavior, and tunable thermodynamics. Although transition metal doping has been widely explored to improve hydrogen uptake and release, the atomic-scale diffusion mechanisms governing these processes remain insufficiently explored. In this work, experimental hydrogenation and dehydrogenation measurements have been combined with density functional theory calculations to elucidate hydrogen sorption behavior in Mn and V-doped TiFe. Differential Scanning Calorimetry coupled with Kissinger analysis revealed the impact of doping on the activation energy of hydrogen desorption, yielding value 1.35 eV for Mn doping and 1.72 eV and 1.60 eV for V doping, indicating modified reaction kinetics. Complementary, DFT-NEB calculations provided hydrogen migration pathways within the β and γ-phases, showing competitive diffusion barriers with a directional dependence, influenced by local chemical environment. The rate-limiting diffusion barriers are found to be 0.71 eV (β) and 0.75 eV (γ) for Mn-doped TiFe, and 0.86 eV (β) and 0.19 eV (γ) for V-doped TiFe. By relating the measured hydrogen desorption activation energy to the calculated hydrogen migration barriers, this integrated approach provides a deep understanding of hydrogen transport in TiFe-based hydrides and provides insights useful for optimizing dopant selection.