Synergistic Effects of Transition Metal (Mn, Ni) Doping and Activated Carbon on Hydrogen Storage in TiFe ‐Based Alloys

ABSTRACT TiFe‐based alloys are attractive solid‐state hydrogen storage materials but their practical application is restricted by the formation of a stable surface oxide layer, which necessitates high‐temperature activation before the first hydrogenation. In this study, the synergistic effects of Mn and Ni substitution with activated carbon (AC) on the activation behavior and hydrogen storage performance of TiFe‐based alloys are systematically investigated. The mechanically milled TiFe‐based alloys are further characterized using X‐ray diffraction (XRD), scanning electron microscopy coupled with energy‐dispersive spectroscopy (SEM/EDS), and differential scanning calorimetry (DSC). First‐cycle hydrogen absorption behavior of metal alloys is evaluated by Volumetric pressure–composition–temperature (PCT) measurements at 25°C and 5 MPa using Isorb HP‐1. Results showed that TiFe‐based alloys exhibited direct first‐cycle hydrogen absorption without the conventional high‐temperature activation treatment, revealing the effectiveness of mechanical activation in overcoming the surface oxide barrier. DSC analysis showed that Mn‐, Ni‐, and AC‐modified alloys reduced the hydride decomposition temperature from ≈400°C to 320°C. Among the investigated compositions, TiFe 0.8 Ni 0.2 + AC 0.4 exhibited the highest first‐cycle hydrogen uptake of 1.7 wt.% at 25°C and 5 MPa. These findings demonstrate that the combined effects of mechanical activation, transition‐metal substitution, and AC effectively eliminate the need for conventional activation while enhancing the first‐cycle hydrogen storage performance of TiFe‐based alloys, providing a practical strategy for room‐temperature solid‐state hydrogen storage.