Reversible hydrogen sorption and kinetics of hydrogen storage tank based on MgH2 modified by TiF4 and activated carbon

By doping with 5 wt % TiF₄ and activated carbon (AC), onset and main dehydrogenation temperatures of MgH₂ significantly reduce (ΔT = 138 and 109 °C, respectively) with hydrogen capacity of 4.4 wt % H₂. Up-scaling to storage tank begins with packing volume and sample weight of 28.8 mL and ～14.5 g, respectively, and continues to 92.6 mL and ～60.5–67 g, respectively. Detailed hydrogen sorption mechanisms and kinetics of the tank tightly packed with four beds of MgH₂TiF₄-AC (～60.5 g) are investigated. De/rehydrogenation mechanisms are detected by three temperature sensors located at different positions along the tank radius, while hydrogen permeability is benefited by stainless steel mesh sheets and tube inserted in the hydride beds. Fast desorption kinetics of MgH₂TiF₄-AC tank at ～275–283 °C, approaching to onset dehydrogenation temperature of the powder sample (272 °C) suggests comparable performances of laboratory and tank scales. Hydrogen desorption (T = 300 °C and P(H₂) = 1 bar) and absorption (T = 250 °C and P(H₂) = 10–15 bar) of MgH₂TiF₄-AC tank provide gravimetric and volumetric capacities during the 1^st-2nd cycles of 4.46 wt % H₂ and 28 gH₂/L, respectively, while those during the 3^rd-15th cycles are up to 3.62 wt % H₂ and 23 gH₂/L, respectively. Due to homogeneous heat transfer along the tank radius, de/rehydrogenation kinetics superior at the tank center and degrading forward the tank wall can be due to poor hydrogen permeability. Particle sintering and/or agglomeration upon cycling yield deficient hydrogen content reproduced.     

Kinetic performance of hydrogen generation enhanced by AlCl3 via hydrolysis of MgH2 prepared by hydriding combustion synthesis

Magnesium hydride (MgH₂) is a very promising hydrogen storage material and it has been paid more and more attention on the application of supplying hydrogen on-board because the theoretical hydrogen yield is up to 1703 mL/g when it reacts with water. However, the hydrolysis reaction is inhibited rapidly by the passivation layer of Mg(OH)₂ formed on the surface of MgH₂. This paper reports that high purity MgH₂ (～98.7 wt%) can be readily obtained by the process of hydriding combustion synthesis (HCS) and the hydrogen generation via hydrolysis of the as-prepared HCSed MgH₂ can be dramatically enhanced by the addition of AlCl₃ in hydrolysis solutions. An excellent kinetics of hydrogen generation of 1487 mL/g in 10 min and 1683 mL/g in 17 min at 303 K was achieved for the MgH₂-0.5 M AlCl₃ system, in which the theoretical hydrogen yield (1685 mL/g) of the HCSed product was nearly reached. The mechanism of the hydrolysis kinetics enhancement was demonstrated by the generation of a large amounts of H⁺ from the Al³⁺ hydrolysis and the pitting corrosion (Cl^?) of the Mg(OH)₂ layer wrapped on the surface of MgH₂ even at a low temperature. In addition, the apparent activation energies for the MgH₂ hydrolysis in the 0.1 M AlCl₃ and 0.5 M AlCl₃ solutions are decreased to 34.68 kJ/mol and 21.64 kJ/mol, respectively, being far superior to that of reported in deionized water (58.06 kJ/mol). The results suggest that MgH₂ + AlCl₃ system may be used as a promising hydrogen generation system in practical application of supplying hydrogen on-board.     

Enhanced reversibility of the electrochemical Li conversion reaction with MgH2–TiH2 nanocomposites

Nanostructured metallic hydrides are promising anode active materials for the next generations of Li-ion batteries due to their high capacities, adapted working potential and low polarisation. In the present study, nanocomposites made of yMgH₂ and (1 ? y)TiH₂ with molar composition y = 0.2, 0.5 and 0.8 were prepared by mechanical milling of elemental metal powders under hydrogen pressure. Microstructural analysis by X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM) shows the co-existence of the two hydrides at the nanoscale with average crystallite sizes comprised between 4 and 11 nm. Galvanostatic and cyclic voltammetry experiments have been performed to investigate the reversibility of the conversion reaction between both hydrides and lithium. All nanocomposites can be fully lithiated for the first discharge, but the reversibility of the reaction strongly depends on the composition. No reformation of any hydride occurs for the TiH₂-rich composite (y = 0.2), TiH₂ is only partially reformed for the equimolar composite (y = 0.5) and both MgH₂ and TiH₂ hydrides are recovered at different extents for the Mg-rich one (y = 0.8). A high reversibility (almost 80%) of TiH₂ is attained in the latter composite with a promising capacity retention (70% over ten cycles) by cycling within a restricted potential window.     

Influence of K2TiF6 additive on the hydrogen sorption properties of MgH2

In this study, the hydrogen storage properties of MgH₂ with the addition of K₂TiF₆ were investigated for the first time. The temperature-programmed desorption results showed that the addition of 10 wt% K₂TiF₆ to the MgH₂ exhibited a lower onset desorption temperature of 245 °C, which was a decrease of about 105 °C and 205 °C compared with the as-milled and as-received MgH₂, respectively. The dehydrogenation and rehydrogenation kinetics of 10 wt% K₂TiF₆-doped MgH₂ were also significantly improved compared to the un-doped MgH₂. The results of the Arrhenius plot showed that the activation energy for the hydrogen desorption of MgH₂ was reduced from 164 kJ/mol to 132 kJ/mol after the addition of 10 wt% K₂TiF₆. Meanwhile, the X-ray diffraction analysis showed the formation of a new phase of potassium hydride and titanium hydride together with magnesium fluoride and titanium in the doped MgH₂ after the dehydrogenation and rehydrogenation process. It is reasonable to conclude that the K₂TiF₆ additive doped with MgH₂ played a catalytic role through the formation of active species of KH, TiH₂, MgF₂ and Ti during the ball milling or heating process. It is therefore proposed that this newly developed product works as a real catalyst for improving the hydrogen sorption properties of MgH₂.     

Synthesis of BaFe12O19 by solid state method and its effect on hydrogen storage properties of MgH2

Previous studies have shown that ferrites give a positive effect in improving the hydrogen sorption properties of magnesium hydride (MgH₂). In this study, another ferrite, i.e., BaFe₁₂O₁₉, has been successfully synthesised via the solid state method, and it was milled with MgH₂ to enhance the sorption kinetics. The result showed that the MgH₂ + 10 wt% BaFe₁₂O₁₉ sample started to release hydrogen at about 270 °C which is about 70 °C lower than the as-milled MgH₂. The doped sample was able to absorb hydrogen for 4.3 wt% in 10 min at 150 °C, while as-milled MgH₂ only absorbed 3.5 wt% of hydrogen under similar conditions. The desorption kinetic results showed that the doped sample released about 3.5 wt% of hydrogen in 15 min at 320 °C, while the as-milled MgH₂ only released about 1.5 wt% of hydrogen. From the Kissinger plot, the apparent activation energy of the BaFe₁₂O₁₉-doped MgH₂ sample was 115 kJ/mol which was lower than the milled MgH₂ (141 kJ/mol)_. Further analyses demonstrated that MgO, Fe and Ba or Ba-containing contribute to the improvement by serving as active species, thus enhancing the MgH₂ for hydrogen storage.     

Effect of additive distribution in H2 absorption and desorption kinetics in MgH2 milled with NbH0.9 or NbF5

This paper presents a comparative study of H₂ absorption and desorption in MgH₂ milled with NbF₅ or NbH_0.9. The addition of NbF₅ or NbH_0.9 greatly improves hydriding and dehydriding kinetics. After 80 h of milling the mixture of MgH₂ with 7 mol.% of NbF₅ absorbs 60% of its hydrogen capacity at 250 °C in 30 s, whereas the mixture with 7 mol.% of NbH_0.9 takes up 48%, and MgH₂ milled without additive only absorbs 2%. At the same temperature, hydrogen desorption in the mixture with NbF₅ finishes in 10 min, whereas the mixture with NbH_0.9 only desorbs 50% of its hydrogen content, and MgH₂ without additive practically does not releases hydrogen. The kinetic improvement is attributed to NbH_0.9, a phase observed in the hydrogen cycled MgH₂ + NbF₅ and MgH₂ + NbH_0.9 materials, either hydrided or dehydrided. The better kinetic performance of the NbF₅-added material is attributed to the combination of smaller size and enhanced distribution of NbH_0.9 with more favorable microstructural characteristics. The addition of NbF₅ also produces the formation of Mg(H_xF_1-x)₂ solid solutions that limit the practically achievable hydrogen storage capacity of the material. These undesired effects are discussed.     

Destabilization of LiAlH4 by nanocrystalline MgH2

In this work, we report the synthesis, characterization and destabilization of lithium aluminum hydride by ad-mixing nanocrystalline magnesium hydride (e.g. LiAlH₄ + nanoMgH₂). A new nanoparticulate complex hydride mixture (Li–nMg–Al–H) was obtained by solid-state mechano-chemical milling of the parent compounds at ambient temperature. Nanosized MgH₂ is shown to have greater and improved hydrogen performance in terms of storage capacity, kinetics, and initial temperature of decomposition, over the commercial MgH₂. The pressure–composition isotherms (PCI) reveal that the destabilized LiAlH₄ + nanoMgH₂ possess ∼5.0 wt.% H₂ reversible capacity at T ≤ 350 °C. Van't Hoff calculations demonstrate that the destabilized (LiAlH₄ + nanoMgH₂) complex materials have comparable enthalpy of hydrogen release (∼85 kJ/mole H₂) to their pristine counterparts, LiAlH₄ and MgH₂. However, these new destabilized complex hydrides exhibit reversible hydrogen sorption behavior with fast kinetics.     

A novel complex oxide TiVO3.5 as a highly active catalytic precursor for improving the hydrogen storage properties of MgH2

Herein, we demonstrate the successful preparation of a novel complex transition metal oxide (TiVO_3.5) by oxidizing a solid-solution MXene (Ti_0.5V_0.5)₃C₂ at 300 °C and its high activity as a catalyst precursor in the hydrogen storage reaction of MgH₂. The prepared TiVO_3.5 inherits the layered morphology of its MXene precursor, but the layer surface becomes very coarse because of the presence of numerous nanoparticles. Adding a minor amount of TiVO_3.5 remarkably reduces the dehydrogenation and hydrogenation temperatures of MgH₂ and enhances the reaction kinetics. The 10 wt% TiVO_3.5-containing sample exhibits optimal hydrogen storage properties, as it desorbs approximately 5.0 wt% H₂ in 10 min at 250 °C and re-absorbs 3.9 wt% H₂ in 5 s at 100 °C and under 50 bar of hydrogen pressure. The apparent activation energy is calculated to be approximately 62.4 kJ/mol for the MgH₂-10 wt% TiVO_3.5 sample, representing a 59% reduction in comparison with pristine MgH₂ (153.8 kJ/mol), which reasonably explains the remarkably reduced dehydrogenation operating temperature. Metallic Ti and V are detected after ball milling with MgH₂; they are uniformly dispersed on the MgH₂ matrix and act as actual catalytic species for the improvement of the hydrogen storage properties of MgH₂.     

Improvement of hydrogen storage properties in MgH2 catalysed by K2NbF7

The catalytic effects of K₂NbF₇ on the hydrogen storage properties of MgH₂ have been studied for the first time. MgH₂ + 5 wt% K₂NbF₇ has reduced the onset dehydrogenation temperature to 255 °C, which is 75 °C lower than the as-milled MgH₂. For the rehydrogenation kinetic, at 150 °C, MgH₂ + 5 wt% K₂NbF₇ absorbs 4.7 wt% of hydrogen in 30 min whereas the as-milled MgH₂ only absorbs 0.7 wt% of hydrogen under similar condition. For the dehydrogenation kinetic, at 320 °C, the MgH₂ + 5 wt% K₂NbF₇ is able to release 5.2 wt% of hydrogen in 5.6 min as compared to 0.3 wt% by the as-milled MgH₂ under similar condition. Comparatively, the E_a value of MgH₂ + 5 wt% K₂NbF₇ is 96.3 kJ/mol, which is 39 kJ/mol lower compared to the as-milled MgH₂. The MgF₂, the KH and the Nb that are found after the heating process are believed to be the active species that have improved the system properties. It is concluded that the K₂NbF₇ is a good catalyst to improve the hydrogen storage properties of MgH₂.     

Enhanced electrochemical lithium storage performance of Mg2FeH6 anode with TiO2 coating

Light-weight metal hydrides are potential high-capacity conversion anode materials for lithium-ion batteries, but the poor reaction reversibility and cyclic stability of hydride anodes need to be improved. In this work, the ternary hydride Mg₂FeH₆ was composited with the graphite (G) by ball-milling, and the Mg₂FeH₆-G composite electrode was further coated with amorphous TiO₂ film by magnetron sputtering. The resultant Mg₂FeH₆-G/TiO₂ electrode exhibited a stable charge capacity of 412 mAh g^?1 over 100 cycles, which is much higher than 46 mAh g^?1 at 20th cycle for the pure Mg₂FeH₆ electrode, or 185 mAh g^?1 at 100th cycle for the Mg₂FeH₆-G electrode. There is only little capacity degradation after 20 cycles for the Mg₂FeH₆-G/TiO₂ electrode and the charge capacity retention is 84.7% after 100 cycles. The remarkable improvement in the cyclic stability of Mg₂FeH₆-G/TiO₂ electrode is mainly attributed to the dense TiO₂ coating that maintains the structural integrity of electrode during cycling. The TiO₂ coating also prevents the direct contact of high active LiH/MgH₂ with the liquid electrolyte, and thus ensures the high reversibility of conversion reaction of MgH₂ during cycling.     

Hydrogen storage properties of nano-structured 0.65MgH2/0.35ScH2

The intermetallic compound Mg_0.65Sc_0.35 was found to form a nano-structured metal hydride composite system after a (de)hydrogenation cycle at temperatures up to 350 °C. Upon dehydrogenation phase separation occurred forming Mg-rich and Sc-rich hydride phases that were clearly observed by SEM and TEM with the Sc-rich hydride phase distributed within Mg/MgH₂-rich phase as nano-clusters ranging in size from 40 to 100 nm. The intermetallic compound Mg_0.65Sc_0.35 showed good hydrogen uptake, ca. 6.4 wt.%, in the first charging cycle at 150 °C and in the following (de)hydrogenation cycles, a reversible hydrogen capacity (up to 4.3 wt.%) was achieved. Compared to the as-received MgH₂, the composite had faster cycling kinetics with a significant reduction in activation energy E_a from 159 ± 1 kJ mol⁻¹ to 82 ± 1 kJ mol⁻¹ (as determined from a Kissinger plot). Two-dehydrogenation events were observed by DSC and pressure–composition-isotherm (PCI) measurements, with the main dehydrogenation event being attributed to the Mg-rich hydride phase. Furthermore, after the initial two cycles the hydrogen storage capacity remained unchanged over the next 55 (de)hydrogenation cycles.     

Synergistic catalytic effect of SrTiO3 and Ni on the hydrogen storage properties of MgH2

Study on the synergistic catalytic effect of the SrTiO₃ and Ni on the improvement of the hydrogen storage properties of the MgH₂ system has been carried out. The composites have been prepared using ball milling method and comparisons on the hydrogen storage properties of the MgH₂ – Ni and MgH₂ – SrTiO₃ composites have been presented. The MgH₂ – 10 wt% SrTiO₃ – 5 wt% Ni composite is found to has a decomposition temperature of 260 °C with a total decomposition capacity of 6 wt% of hydrogen. The composite is able to absorb 6.1 wt% of hydrogen in 1.3 min (320 °C, 27 atm of hydrogen). At 150 °C, the composite is able to absorb 2.9 wt% of hydrogen in 10 min under the pressure of 27 atm of hydrogen. The composite has successfully released 6.1 wt% of hydrogen in 13.1 min with a total dehydrogenation of 6.6 wt% of hydrogen (320 °C). The apparent activation energy, E_a, for decomposition of SrTiO₃-doped MgH₂ reduced from 109.0 kJ/mol to 98.6 kJ/mol after the addition of 5 wt% Ni. The formation of Mg₂Ni and Mg₂NiH₄ as the active species help to boost the performance of the hydrogen storage properties of the MgH₂ system. Observation of the scanning electron microscopy images suggested the catalytic role of the SrTiO₃ additive is based on the modification of composite microstructure.     

A comparative study of the role of additive in the MgH2 vs. the LiBH4-MgH2 hydrogen storage system

The objective of the present work is the comparative study of the behaviour of the Nb- and Ti-based additives in the MgH₂ single hydride and the MgH₂ + 2LiBH₄ reactive hydride composite. The selected additives have been previously demonstrated to significantly improve the sorption reaction kinetics in the corresponding materials. X-Ray Diffraction (XRD), X-Ray Absorption Spectroscopy (XAS), X-Ray Photoelectron Spectroscopy (XPS) and Electron Microscopy (TEM) analysis were carried out for the milled and cycled samples in absence or presence of the additives. It has been shown that although the evolution of the oxidation state for both Nb- and Ti-species are similar in both systems, the Nb additive is performing its activity at the surface while the Ti active species migrate to the bulk. The Nb-based additive is forming pathways that facilitate the diffusion of hydrogen through the diffusion barriers both in desorption and absorption. For the Ti-based additive in the reactive hydride composite, the active species are working in the bulk, enhancing the heterogeneous nucleation of MgB₂ phases during desorption and producing a distinct grain refinement that favours both sorption kinetics. The results are discussed in regards to possible kinetic models for both systems.     

Activation effects during hydrogen release and uptake of MgH2

Scandium(II)hydride, ScH₂, and scandium(III)chloride, ScCl₃, are explored as additives to facilitate hydrogen release and uptake for magnesium hydride. These additives are expected to form more homogeneous composites with Mg/MgH₂ as compared to metallic scandium. However, scandium(III)chloride, reacts with MgH₂ during mechano-chemical treatment and form ScH₂ and MgCl₂ (that later crystallise during heat treatment). The composite MgH₂−ScH₂ was investigated using in-situ synchrotron radiation powder X-ray diffraction during up to five cycles of continuous release and uptake of hydrogen at isothermal conditions at 320, 400 and 450 °C and p(H₂) = 100–150 or 10⁻² bar. The data were analysed by Rietveld refinement and no reaction is observed between either MgH₂/ScH₂ or Mg/ScH₂ during cycling. The extracted sigmoidal shaped curves for formation or decomposition of Mg/MgH₂ suggest that a nucleation process is preceding the crystal growth. The reaction rate increases with increasing number of cycles of hydrogen release and uptake at isothermal conditions possibly due to activation effects. This kinetic enhancement is strongest between the first cycles and may be denoted an activation effect.     

Influence of multiple oxide (Cr2O3/Nb2O5) addition on the sorption kinetics of MgH2

The influence of multiple additions of two oxides, Cr₂O₃ and Nb₂O₅, as additives on the hydrogen sorption kinetics of MgH₂ after milling was investigated. We found that the desorption kinetics of MgH₂ were improved more by multiple oxide addition than by single addition. Even for the milled MgH₂ micrometric size powders, the high hydrogen capacity with fast kinetics were achieved for the powders after addition of 0.2 mol% Cr₂O₃ + 1 mol% Nb₂O₅. For this composition, the hydride desorbed about 5 wt.% hydrogen within 20 min and absorbed about 6 wt.% in 5 min at 300 °C. Furthermore, the desorption temperature was decreased by 100 °C, compared to MgH₂ without any oxide addition, and the activation energy for the hydrogen desorption was estimated to be about 185 kJ mol⁻¹, while that for MgH₂ without oxide was about 206 kJ mol⁻¹.     

Improvement of hydrogen-storage properties of MgH2 by Ni,LiBH4, and Ti addition

In this work, differently from our previous work, MgH₂ instead of Mg was used as a starting material. Ni, Ti, and LiBH₄ with a high hydrogen-storage capacity of 18.4 wt% were added. A sample with a composition of MgH₂–10Ni–2LiBH₄–2Ti was prepared by reactive mechanical grinding. MgH₂–10Ni–2LiBH₄–2Ti after reactive mechanical grinding contained MgH₂, Mg, Ni, TiH_1.924, and MgO phases. The activation of MgH₂–10Ni–2LiBH₄–2Ti for hydriding and dehydriding reactions was not required. At the number of cycles, n = 2, MgH₂–10Ni–2LiBH₄–2Ti absorbed 4.09 wt% H for 5 min, 4.25 wt% H for 10 min, and 4.44 wt% H for 60 min at 573 K under 12 bar H₂. At n = 1, MgH₂–10Ni–2LiBH₄–2Ti desorbed 0.13 wt% H for 10 min, 0.54 wt% H for 20 min, 1.07 wt% H for 30 min, and 1.97 wt% H for 60 min at 573 K under 1.0 bar H₂. The PCT (Pressure–Composition–Temperature) curve at 593 K for MgH₂–10Ni–2LiBH₄–2Ti showed that its hydrogen-storage capacity was 5.10 wt%. The inverse dependence of the hydriding rate on temperature is partly due to a decrease in the pressure differential between the applied hydrogen pressure and the equilibrium plateau pressure with the increase in temperature. The rate-controlling step for the dehydriding reaction of the MgH₂–10Ni–2LiBH₄–2Ti at n = 1 was analyzed.     

Hydrogen sorption,kinetics, reversibility,and reaction mechanisms of MgH2-xLiBH4 doped with activated carbon nanofibers for reversible hydrogen storage based laboratory powder and tank scales

De/rehydrogenation kinetics and reversibility of MgH₂ are improved by doping with activated carbon nanofibers (ACNF) and compositing with LiBH₄. Via doping with 5 wt % ACNF, hydrogen absorption of Mg to MgH₂ (T = 320 °C and p(H₂) = 50 bar) increases from 0.3 to 4.5 wt % H₂. Significant reduction of onset dehydrogenation temperature of MgH₂ to 340 °C (ΔT = 70 °C as compared with pristine MgH₂) together with 6.8–8.2 wt % H₂ can be obtained by compositing Mg-5 wt. % ACNF with LiBH₄ (LiBH₄:Mg mole ratios of 0.5:1, 1:1, and 2:1). During dehydrogenation of Mg-rich composites (0.5:1 and 1:1 mol ratios), the formation of MgB₂ and Mg_0.816Li_0.184 implying the reaction between LiBH₄ and MgH₂ favors kinetic properties and reversibility, while the composite with 2:1 mol ratio shows individual dehydrogenation of LiBH₄ and MgH₂. For up-scaling to hydrogen storage tank (～120 times greater sample weight than laboratory scale) of the most suitable composite (1:1 mol ratio), de/rehydrogenation kinetics and hydrogen content released at all positions of the tank are comparable and approach to those from laboratory scale. Due to high purity (100%) and temperature of hydrogen gas from hydride tank, the performance of single proton exchange membrane fuel cell enhances up to 30% with respect to the results from compressed gas tank.     

Effect of Nb2O5 on MgH2 properties during mechanical milling

Recently, it was shown that hydrogen absorption–desorption kinetics in magnesium were improved by milling magnesium hydride (MgH₂) with transition metal oxides. Herein, we investigate the role of the most effective of these oxides, Nb₂O₅ when added in larger volume fraction. The effect of Nb₂O₅ on magnesium crystalline structure, particle size and (ab)desorption properties has been characterised. Moreover, we report that pure MgH₂ can also show fast hydrogen sorption kinetics after a long milling time. The effects of Nb₂O₅ on MgH₂ sorption properties are rationalised in a new approach considering Nb₂O₅ as a dispersing agent, which helps reduce MgH₂ particle size during milling.     

Sorption properties of NaBH4/MH2 (M = Mg,Ti) powder systems

The sorption properties of NaBH₄/MH₂ (M = Mg, Ti) powder systems prepared by high-energy ball milling have been thoroughly investigated. Concerning the systems containing MgH₂, the 2:1 and 1:2 molar compositions have been studied and both lead to a multi-step desorption pathway, where the formation of MgB₂ confirms the destabilization of NaBH₄ induced by the presence of MgH₂. A noticeable kinetic enhancement is achieved for the MgH₂-rich system (composition 1:2) if compared with the NaBH₄-rich system (composition 2:1). Even though full re-absorption is obtained for neither of the two compositions, fast kinetics is achieved. During absorption, the unsuspected formation of the perovskite-type hydride NaMgH₃ is detected and it is showed that this ternary phase contributes to reduce the gravimetric capacity of the systems. Conversely, in the 2NaBH₄/TiH₂ system, there is no formation of the intermetallic compound TiB₂. Furthermore, a decrease in the sorption kinetics is found in comparison with the systems based on MgH₂.     

Hydrogen storage performance of LiBH4+1/2MgH2 composites improved by Ce-based additives

LiBH₄+1/2MgH₂ is a promising reactive hydride composite for hydrogen storage. In the present study, three Ce-based additives were used as catalysts to enhance the hydrogen storage performance of LiBH₄+1/2MgH₂ composites. The composites with Ce additives demonstrated significantly improved dehydrogenation kinetics and cyclic stability compared with the pure composite. X-ray diffraction and scanning electron microscopy analyses clearly revealed the phase transitions and morphological evolution during the hydriding-dehydriding cycling. The composites with Ce-based additives displayed stable nanostructures, in contrast to the rapid microstructural deterioration in the uncatalyzed composite. The CeB₆ formed in the composites had a particle size of 10 nm after five cycles. It may act as the nucleus for MgB₂ formation during dehydrogenation and thus account for the structural and performance stability of the composites upon cycling.