Optimizing the kinetics and lowering the ab/dehydrogenation temperature of magnesium hydride (MgH₂) are crucial for hydrogen storage applications. The synergy among multi-metals (such as Ni, Cr, Fe, Cu, etc.) can reduce the ab/dehydrogenation activation energy of magnesium hydride by leveraging the characteristics of transition metals. Herein, Crystal-amorphous interfaces were regulated via changing the reducing atmosphere through precise design to form the semi-crystalline Ni/CrV-MMO catalysts. After the tests, the 10 wt%Ni/CrV-MMO-doped MgH₂ initial hydrogen release at 190 ℃ and desorbed 5.6 wt% H₂ at a relatively low temperature of 275 ℃ within 10 min. Moreover, this composite material absorbed 5.7 wt% H₂ within 2 min at 150 ℃, achieving a remarkably low hydrogen absorption activation energy of only 28.35 kJ·mol⁻¹, which is far below pure MgH₂ (68.42 kJ·mol⁻¹). Mechanistic studies and density functional theory (DFT) reveal that the amorphous CrV-MMO elevates the D-band center of Ni by contacting with the Ni interface, which weakens the Mg–H bond strength and consequently lowers the dehydrogenation barrier. The existence of crystal-amorphous interfaces effectively optimizes the transport of interfacial charges. This crystal-amorphous interface synergy strategy offers a general blueprint for low-temperature, high-rate MgH₂ storage systems.

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.

Catalytic doping of magnesium hydride (MgH₂) to improve its hydrogen ab/desorption kinetic properties is considered to be an effective and feasible method. In solid-phase catalysis, the extent of contact between the catalyst and the substrate determines the catalytic reaction in a great sense. With large specific surface area and abundant active sites, two-dimensional (2D) nanomaterials are promising catalysts for MgH₂ via providing numerous pathways for the diffusion and dissociation of hydrogen. In this regard, 2D NiMn-based layered double hydroxide and layered metallic oxide (LMO) are designed and introduced into MgH₂ to improve its hydrogen storage properties. Simultaneous enhancement in interfacial contact, desorption temperature and kinetics are achieved. The MgH₂+9wt% Ni₃Mn-LMO composites begin to discharge hydrogen at only 190 ℃ and 6.10wt% H₂ could be charged in 600 s at 150 ℃. The activation energy for de/hydrogenation is reduced by 42.43% and 46.56%, respectively, compared to pure MgH₂. Even at a low operating temperature of 235 ℃, the modified system was still able to release 4.44wt% H₂ in an hour, which has rarely been reported in previous studies. Microstructure observations and density functional theory calculations revealed that first, the hydrogen pumping effect of Mg₂Ni/Mg₂NiH₄ promotes the adsorption and desorption of hydrogen molecules on the surface of MgH₂, second, MnO_x drew electrons from Mg₂Ni, producing a new Density of State structure with a lower d-bond center. This unique change further strengthens the Mg₂Ni/Mg₂NiH₄ pump effect on MgH₂. Our work indicates that the application of 2D metal-based catalysts is a feasible and promising approach towards MgH₂ for solid-state hydrogen storage to meet technical and scientific requirements.

The lattice distortion effect and cocktail effect of high-entropy oxides (HEOs) will dominate the catalytic effect of the materials, in order to study the influence of the constituent elements of HEOs on the lattice distortion effect and cocktail effect, through elemental manipulation of Cr, Cu, and La, high entropy oxides (HEOs) catalyst CrMnFeCoNiO (Cr_1:1), CuMnFeCoNiO (Cu_1:1), and LaMnFeCoNiO (La_1:1) were effectively synthesized by the facile co-precipitation approach. With a size of about 10 nm, Cr_1:1 presented significant modification impacts on enhancing the hydrogen storage capability of MgH₂. Specifically, MgH₂ was able to release hydrogen at 200 ℃ with the addition of Cr_1:1, MgH₂+10wt% Cr_1:1 showed prompt rate of dehydrogenation which could release 5.56 wt% H₂ in 20 min at 250 ℃, and the activation energy of MgH₂ was lowered to 69.77± 3.75 kJ·mol⁻¹ by adding Cr_1:1. According to the Chou model fitting, the exceptional kinetic performance of the composite was attributable to a rate-controlling step changed from low-speed surface penetration to high-speed diffusion. Furthermore, MgH₂+10wt% Cr_1:1 was capable of absorbing hydrogen at ambient temperature and the composite could uptake 6 wt% H₂ within 8 min at the temperature of 150 ℃. Due to the high entropy effects of HEOs, Cr_1:1 possessed superior stability, which guarantees the robust cycling qualities of MgH₂+10wt% Cr_1:1. Meanwhile, microstructure analysis revealed that the active sites with numerous heterogeneous structures were uniformly dispersed on surfaces, exhibiting superior catalytic effects on improving the hydrogen storage performance of MgH₂.

As a promising hydrogen storage material, the practical application of magnesium is obstructed by the stable thermodynamics and sluggish kinetics. In this paper, three kinds of NiTiO₃ catalysts with different mole ratio of Ni to Ti were successfully synthesized and doped into nanocrystalline Mg to improve its hydrogen storage properties. Experimental results indicated that all the Mg-NiTiO₃ composites showed prominent hydrogen storage performance. Especially, the Mg-NiTiO₃/TiO₂ composite could take up hydrogen at room temperature and the apparent activation energy for hydrogen absorption was dramatically decreased from 69.8 ± 1.2 (nanocrystalline Mg) kJ/mol to 34.2 ± 0.2 kJ/mol. In addition, the hydrogenated sample began to release hydrogen at about 193.2 ℃ and eventually desorbed 6.6 wt% H₂. The desorption enthalpy of the hydrogenated Mg-NiTiO₃-C was estimated to be 78.6 ± 0.8 kJ/mol, 5.3 kJ/mol lower compared to 83.9 ± 0.7 kJ/mol of nanocrystalline Mg. Besides, the sample revealed splendid cyclic stability during 20 cycles. No obvious recession occurred in the absorption and desorption kinetics and only 0.3 wt% hydrogen capacity degradation was observed. Further structural analysis demonstrates that nanosizing and catalyst doping led to a synergistic effect on the enhanced hydrogen storage performance of Mg-NiTiO₃-C composite, which might serve as a reference for future design of highly effective hydrogen storage materials.