TiSiO₄ as a Catalytic Dopant for Lowering the Decomposition Temperature and Improve Kinetics of AlH₃ for Solid-State Hydrogen Storage

Aluminium hydride (AlH₃) is a promising solid-state hydrogen storage material due to its high theoretical capacity of 10.1 wt.% H₂. However, its practical use is limited by a high decomposition onset temperature and slow desorption kinetics. This study introduces titanium silicate (TiSiO₄) as a novel catalytic dopant to address these challenges. A composite of 10 wt.% TiSiO₄–AlH₃ was prepared via planetary ball milling under an argon atmosphere. The dehydrogenation behavior was systematically investigated using temperature-programmed desorption (TPD), isothermal kinetics measurements, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The incorporation of TiSiO₄ profoundly enhanced the dehydrogenation performance. TPD revealed that the onset temperature for hydrogen release dropped from 127 °C for milled AlH₃ to below 50 °C—a reduction exceeding 77 °C. Isothermal desorption at 60 °C showed that the doped composite released about 2.1 wt.% H₂ within the first hour, while the undoped material was nearly inert. Kissinger analysis of DSC data indicated a substantial decrease in the apparent activation energy by 46.6 kJ/mol, confirming a lowered kinetic barrier. Mechanistic studies revealed a synergistic two-part effect of TiSiO₄. Although not directly detected by XRD due to its low content and possible amorphous nature, TiSiO₄ is proposed to electronically polarize and weaken Al–H bonds at the surface, facilitating initial bond cleavage. Simultaneously, SEM and XRD evidence indicates that TiSiO₄ acts as a nanostructuring agent, dispersing AlH₃ into finer particles during milling and heating. This creates a nanoconfinement effect that shortens hydrogen diffusion paths, suppresses agglomeration of AlH₃ and metallic Al during decomposition, and provides nucleation sites for Al formation—a critical step in the decomposition pathway. In summary, TiSiO₄ doping introduces a dual catalytic and nanoconfinement mechanism that destabilizes AlH₃, significantly lowers its decomposition temperature, and accelerates hydrogen release kinetics. This work not only identifies TiSiO₄ as an effective catalyst for AlH₃ but also provides a mechanistic framework that highlights the value of composite design in advancing metal hydrides for practical hydrogen storage.