Hydrogen Storage in TiFe-Based Alloys Doped with Cr and S: Thermodynamic and Structural Peculiarities

For the first time, Tian-Calvet differential heat-conducting microcalorimetry has been applied to the thermochemical analysis of hydrogen absorption and desorption processes in TiFe0.92Cr0.08-H2 and TiFe0.9Cr0.08S0.02-H2 systems. The study revealed a leveling effect in the enthalpy values associated with the α ↔ β and β ↔ γ phase transitions for both alloys. The alloying of TiFe with chromium and sulfur can eliminate the stage of high-temperature activation due to the presence of the catalytically active Ti(Fe,Cr)2 phase and S-enriched precipitations at grain boundaries. Compared to chromium substitution alone, the concurrent substitution of Fe with Cr and S leads to a decrease in the second plateau pressure. This compositional modification method presents a promising avenue for enhancing the hydrogen storage performance of TiFe-based alloys. © 2025 American Chemical Society