Performance Of MgH2 Research Articles

Effect of MOF-derived nanoparticle-cumulated flower-like CoFe@C coated composites on hydrogenation/dehydrogenation performance of MgH2

Magnesium hydride (MgH2) has garnered substantial consideration mainly due to its high gravimetric density and reliable resource, whereas its poor thermodynamics and kinetics for absorbing/releasing hydrogen restricts the largescale application. Certain catalysts have demonstrated remarkable activity in enhancing the hydrogen storage capabilities of MgH2. In this work, the nanoparticle-cumulated flower-like CoFe@C coated catalysts (denoted as CoFe@C) are controllably synthesized as expected by the MOF (Metal-Organic Farmwork) in-suit decomposition method at 800 °C, which exhibits an average pore size of 18.63 nm. Meanwhile, the particle size for the as-prepared CoFe alloy coated in carbon layer are approximately 10–20 nm, and the as-prepared samples are introduced to promote the de/rehydrogenation properties of MgH2 at relatively lower temperatures. Due to the synergistic interaction of CoFe alloy nanoparticles serving as active sites and agglomeration resistance of carbon layers, the MgH2 composites doped with CoFe@C-800 could initialize its decomposition process at 175.9 °C, and may desorb 6.0 wt% H2 at 300 °C in 400 s. Additionally, the peak temperature and apparent activation energy during dehydrogenation decline significantly (with 35 % and 38 %, respectively). Furthermore, theoretical analysis results indicate a higher catalytic activity for the carbon-coated CoFe alloy owing to the synergetic effect between CoFe nanocomposite & carbon layer, which can facilitate the bond extension and strength decrease of Mg-H bonding. In brief, using MOF may derive transition metal and carbon layer, which could be a promising approach to stimulating the hydrogen storage properties of MgH2.

Synergistic effect of Pd single atoms and clusters on the de/re-hydrogenation performance of MgH2

Hydrogen storage plays a pivotal role in the hydrogen industry, yet its current status presents a bottleneck. Diverse strategies have emerged in recent years to address this challenge. MgH2 has stood out as a promising solid-state hydrogen storage material due to its impressive gravimetric and volumetric hydrogen density, but its practical application is hampered by elevated thermal stability and sluggish kinetics. In this study, we introduce a solution by synthesizing Pd metallene through a one-pot solvothermal method, revealing a distinctive highly curved lamellar structure with a thickness of around 1.6 nm. Incorporating this Pd metallene into MgH2 results in a composite system wherein the starting dehydrogenation temperature is significantly lowered to 439 K and complete dehydrogenation occurs at 583 K, releasing 6.14 wt.% hydrogen. The activation energy of dehydrogenation for MgH2 was reduced from 170.4 kJ mol–1 to 79.85 kJ mol–1 after Pd metallene decoration. The enthalpy of dehydrogenation of the MgH2–10 wt.% Pd sample was calculated to be 73 kJ mol–1 H2–1 and decreased by 4.4 kJ mol–1 H2–1 from that of dehydrogenation of pure MgH2 (77.4 kJ mol–1 H2–1). Theoretical calculations show that the average formation energy and average adsorption energy of hydrogen vacancies can be significantly reduced in the presence of both Pd clusters and Pd single atoms on the surface of MgH2/Mg, respectively. It suggests that the synergistic effect of in situ formed Pd single atoms and clusters significantly improves the hydrogenation and dehydrogenation kinetics. The identified active sites in this study hold potential as references for forthcoming multi-sized active site catalysts, underscoring a significant advancement toward resolving hydrogen storage limitations.

Boosting Hydrogen Storage Performance of Mgh2 by In-Situ Formed Pt Nano-Clusters as Destabilization-Catalysis Bi-Functional Additive

Boosting Hydrogen Storage Performance of Mgh2 by In-Situ Formed Pt Nano-Clusters as Destabilization-Catalysis Bi-Functional Additive

Enhancing Hydrogen Storage Properties of MgH2 by Transition Metals and Carbon Materials: A Brief Review.

Magnesium hydride (MgH2) has attracted intense attention worldwide as solid state hydrogen storage materials due to its advantages of high hydrogen capacity, good reversibility, and low cost. However, high thermodynamic stability and slow kinetics of MgH2 has limited its practical application. We reviewed the recent development in improving the sorption kinetics of MgH2 and discovered that transition metals and their alloys have been extensively researched to enhance the de/hydrogenation performance of MgH2. In addition, to maintain the cycling property during the de/hydrogenation process, carbon materials (graphene, carbon nanotubes, and other materials) have been proved to possess excellent effect. In this work, we introduce various categories of transition metals and their alloys to MgH2, focusing on their catalytic effect on improving the hydrogen de/absorption performance of MgH2. Besides, carbon materials together with transition metals and their alloys are also summarized in this study, which show better hydrogen storage performance. Finally, the existing problems and challenges of MgH2 as practical hydrogen storage materials are analyzed and possible solutions are also proposed.

Chemically transformed additive phases in Mg2TiO4 and MgTiO3 loaded hydrogen storage system MgH2

The present work deals with a comparative study of Mg2TiO4, MgTiO3 and titania additives incorporated MgH2. Hydrogen storage measurements suggest that all these additives improve the hydrogen desorption/absorption performance of MgH2. X-ray diffraction (XRD) and X ray photoelectron spectroscopy (XPS) studies highlight that rock salt phases consisting of highly reduced Ti exist in the samples. These results reiterate that in-situ formation of chemically reduced Ti containing active species is a critical step in the catalysis of TiO2/Mg2TiO4/MgTiO3 additives loaded MgH2.

The enhanced de/re-hydrogenation performance of MgH2 with TiH2 additive

The enhanced de/re-hydrogenation performance of MgH₂ with TiH₂ additive

Hydrogen storage properties of MgH2 co-catalyzed by LaH3 and NbH

To improve the hydrogen storage properties of Mg-based alloys, a composite material of MgH2 + 10wt%LaH3 + 10wt%NbH was prepared by a mechanical milling method. The composite exhibited favorable hydrogen desorption properties, releasing 0.67wt% H2 within 20 min at 548 K, which was ascribed to the co-catalytic effect of LaH3 and NbH upon dehydriding of MgH2. By contrast, pure MgH2, an MgH2 + 20wt%LaH3 composite, and an MgH2 + 20wt%NbH composite only released 0.1wt%, 0.28wt%, and 0.57wt% H2, respectively, under the same conditions. Analyses by X-ray diffraction and scanning electron microscopy showed that the composite particle size was small. Energy-dispersive X-ray spectroscopic mapping demonstrated that La and Nb were distributed homogeneously in the matrix. Differential thermal analysis revealed that the dehydriding peak temperature of the MgH2 + 10wt%LaH3 + 10wt%NbH composite was 595.03 K, which was 94.26 K lower than that of pure MgH2. The introduction of LaH3 and NbH was beneficial to the hydrogen storage performance of MgH2.

Understanding the Role of Few-Layer Graphene Nanosheets in Enhancing the Hydrogen Sorption Kinetics of Magnesium Hydride

The catalytic effects of few-layer, highly wrinkled graphene nanosheet (GNS) addition on the dehydrogenation/rehydrogenation performance of MgH2 were investigated. It was found that MgH2-5 wt %GNSs nanocomposites prepared by ball milling exhibit relatively lower sorption temperature, faster sorption kinetics, and more stable cycling performance than that of pure-milled MgH2. The dehydrogenation step confirms that the Avrami exponent n increases from 1.22 to 2.20 by the Johnson-Mehl-Avrami (JMA) formalism when the desorption temperature is reduced from 350 °C to 320 °C and 300 °C, implying that a change in the decomposition temperature can alter the mechanism during the dehydrogenation process. For rehydrogenation, the Avrami value n is close to 1; further study by several models coincident with n = 1 reveals that the absorption process of the MgH2-5 wt %GNSs sample conforms to the Mampel equation formulated through the random nucleation approach and that the nature of the absorption mechanism does not change within the temperature range studied. Furthermore, microstructure analysis demonstrated that the defective GNSs are distributed uniformly among the MgH2 particles and that the grain size of the MgH2-5 wt %GNSs nanocomposite is approximately 5-9 nm. The efficient metal-free catalytic dehydrogenation/rehydrogenation of MgH2 can be attributed to the coupling of the nanosize effect and defective GNSs.