Magnesium-based hydrogen storage materials are promising candidates for hydrogen storage due to their high storage density and environmentally friendly properties. However, the high dehydrogenation enthalpy change (approximately 75 kJ/mol H₂) and high dehydrogenation temperature (573 K at 0.1 MPa) of MgH₂, limits the engineering application of Mg/MgH₂ as a hydrogen storage material. This work reviews the prediction models and methods of enthalpy changes for hydriding/dehydriding (H/D) reactions in order to find out the ideas and ways to reduce them. The mechanism behind the improvement methods mainly includes two aspects, weakening Mg-H bond and compensating heat of reaction. Proceed from this, the experimental methods and enthalpy data as well as calculated values of enthalpy changes were compared systematically. Elements such as Ti, Nb, V, etc., with a small electronegativity difference compared to Mg, can reduce the hydrogenation and dehydrogenation enthalpy changes by forming strong Metal-H or Metal-Mg bonds. In addition, this review concludes with an outlook on the remaining challenge issues and prospects.

Catalytic doping is one of the economic and efficient strategies to optimize the operating temperature and kinetic behavior of magnesium hydride (MgH₂). Herein, efficient regulation of electronic and structural rearrangements in niobium-rich nickel oxides was achieved through precise compositional design and niobium cation functionalized doping, thereby greatly enhancing its intrinsic catalytic activity in hydrogen storage systems. As the niobium concentration increased, the Ni-Nb catalysts transformed into a mixed state of multi-phase nanoparticles (composed of nickel and niobium-rich nickel oxides) with smaller particle size and uniform distribution, thus exposing more nucleation sites and diffusion channels at the MgH₂/Mg interface. In addition, the additional generation of active Ni-Nb-O mixed phase induced numerous highly topical disordered and distorted crystalline, promoting the transfer and reorganization of H atoms. As a result, a stable and continuous multi-phase/component synergistic catalytic microenvironment could be constructed, exerting remarkable enhancement on MgH₂’s hydrogen storage performance. After comparative tests, Ni_0.7Nb_0.3-doped MgH₂ presented the optimal low-temperature kinetics with a dehydrogenation activation energy of 78.8 kJ·mol⁻¹. The onset dehydrogenation temperature of MgH₂+10 wt% Ni_0.7Nb_0.3 was reduced to 198 ℃ and 6.18 wt% H₂ could be released at 250 ℃ within 10 min. In addition, the dehydrogenated MgH₂NiNb composites absorbed 4.87 wt% H₂ in 10 min at 125 ℃ and a capacity retention rate was maintained at 6.18 wt% even after 50 reaction cycles. In a word, our work supplies fresh insights for designing novel defective-state multiphase catalysts for hydrogen storage and other energy related field.

Magnesium-based energy materials, which combine promising energy-related functional properties with low cost, environmental compatibility and high availability, have been regarded as fascinating candidates for sustainable energy conversion and storage. In this review, we provide a timely summary on the recent progress in three types of important Mg-based energy materials, based on the fundamental strategies of composition and structure engineering. With regard to Mg-based materials for batteries, we systematically review and analyze different material systems, structure regulation strategies as well as the relevant performance in Mg-ion batteries (MIBs) and Mg-air batteries (MABs), covering cathodes, electrolytes, anodes for MIBs, and anodes for MABs; as to Mg-based hydrogen storage materials, we discuss how catalyst adding, composite, alloying and nanostructuring improve the kinetic and thermodynamic properties of de/hydrogenation reactions, and in particular, the impacts of composition and structure modification on hydrogen absorption/dissociation processes and free energy modification mechanism are focused; regarding Mg-based thermoelectric materials, the relations between composition/structure and electrical/thermal transport properties of Mg₃X₂ (X = Sb, Bi), Mg₂X (X = Si, Ge, Sn) and MgAgSb-based materials, together with the representative research progress of each material system, are summarized and discussed. Finally, by pointing out remaining challenges and providing possible solutions, this review aims to shed light on the directions and perspectives for practical applications of magnesium-based energy materials in the future.

In this work, we synthesized MoS₂ catalyst via one-step hydrothermal method, and systematically investigated the catalytic effect of MoS₂ on the hydrogen storage properties of MgH₂. The MgH₂-5MoS₂ composite milled for 5 h starts to release hydrogen at 259 ℃. Furthermore, it can desorb 4.0 wt.% hydrogen within 20 min at 280 ℃, and absorb 4.5 wt.% hydrogen within 5 min at 200 ℃. Mo and MoS₂ coexisted in the ball milled sample, whereas only Mo was kept in the sample after dehydrogenation and rehydrogenation, which greatly weakens the Mg-H bonds and facilitates the dissociation of MgH₂ on the surface of Mo (110). The comparative study show that the formed MgS has no catalytic effect for MgH₂. We believed that the evolution and the catalytic mechanism of MoS₂ will provide the theoretical guidance for the application of metal sulfide in hydrogen storage materials.