TiS-derived multiphase catalytic interfaces unlock fast hydrogen desorption in the MgH–Si hydrogen storage system

Abstract

Among various strategies for improving the thermodynamic properties of MgH2, the MgH2–Si hydrogen storage system has attracted considerable attention due to its ability to reconstruct the dehydrogenation pathway. The introduction of Si effectively reduces the reaction enthalpy to 36.4 kJ mol−1 H2, enabling theoretical hydrogen desorption under ambient conditions. Despite these favorable thermodynamic characteristics, hydrogen desorption is still severely limited by sluggish kinetics. In this study, TiS2 was introduced into the MgH2–Si system via high-energy ball milling to optimize dehydrogenation kinetics. As a result, the onset desorption temperature of MgH2–Si–TiS2 is significantly reduced to 140.0 °C, which is 92.2 °C lower than that of the ball-milled MgH2–Si. At 250 °C, the composite can release approximately 4.00 wt% H2 within only 10 min, whereas only 3.90 wt% H2 was released for pristine MgH2–Si for 150 min. The dehydrogenation activation energy of MgH2–Si–TiS2 was 89.28 kJ mol−1, indicating markedly enhanced dehydrogenation kinetics. Experimental characterization reveals that the in situ generated MgS, TiH2 and Ti5Si3 construct a multiphase synergistic catalytic system, providing abundant heterogeneous phase interfaces for the nucleation of Mg2Si. TiH2 works as a hydrogen pump, while MgS weakens the Mg–H bonds and, together with Ti5Si3, increases the interfacial density. Their synergistic effect greatly accelerates the dehydrogenation process. The DFT calculations further reveal that TiS2, in cooperation with Si, modulates the electronic environment at the interface and enhances electron transfer. The superior catalytic mechanism of TiS2 offers a clear and facile strategy for various composite hydrogen storage systems.