Reversible hydrogen storage behavior of LiBH4–Mg(OH)2 composites

The dehydrogenation/hydrogenation properties of LiBH₄-xMg(OH)₂ were systematically investigated. The results show that the LiBH₄-0.3Mg(OH)₂ composite possesses optimal dehydrogenation properties: approximately 9.6 wt% of hydrogen is released via a stepwise reaction with an onset temperature of 100 °C. In the range of 100–250 °C, a chemical reaction between LiBH₄ and Mg(OH)₂ first occurs to give rise to the generation of LiMgBO₃, MgO and H₂. From 250 to 390 °C, the newly developed LiMgBO₃ reacts with LiBH₄ to form MgO, Li₃BO₃, LiH, B₂O₃ and Li₂B₁₂H₁₂ with hydrogen release. From 390 to 450 °C, the decomposition of LiBH₄ and Li₂B₁₂H₁₂ proceeds to release additional hydrogen and to form LiH and B. A further hydrogenation experiment indicates that the dehydrogenated LiBH₄-0.3Mg(OH)₂ sample can take up 4.7 wt% of hydrogen at 450 °C and 100 bar of hydrogen with good cycling stability, which is superior to the pristine LiBH₄.     

A synergistic effect between nanoconfinement of carbon aerogels and catalysis of CoNiB nanoparticles on dehydrogenation of LiBH4

A synergistic effect of nanoconfinement and catalyzing is a new strategy to enhance the dehydrogenation properties of complex hydrides. Herein, LiBH₄ has been infiltrated into a CoNiB-loaded carbon aerogels system (donated as LiBH₄@CA@CoNiB). It is found that the desorption performances of LiBH₄ are significantly strengthened. The onset desorption temperature of LiBH₄@CA@CoNiB is decreased to 192 °C, and majority of the liberation occurs at about 320 °C, much lower than that of pure LiBH₄. Also, about 15.9 wt% H₂ could be released below 600 °C. Furthermore, LiBH₄ doped with CA@CoNiB exhibits an excellent desorption kinetics, with a capacity of 9.33 wt% H₂ released in 30 min at 350 °C, while only 2.13 wt% H₂ is gained for bulk LiBH₄. In addition, the apparent activation energy (Ea) is reduced sharply from 59.00 kJ/mol (pure LiBH₄) to 46.39 kJ/mol.     

Enhanced hydrogen storage properties of LiBH4 modified by NbF5

In this work, the hydriding–dehydriding properties of the LiBH₄–NbF₅ mixtures were investigated. It was found that the dehydrogenation and reversibility properties of LiBH₄ were significantly improved by NbF₅. Temperature-programed dehydrogenation (TPD) showed that 5LiBH₄–NbF₅ sample started releasing hydrogen from as low as 60 °C, and 4 wt.% hydrogen could be obtained below 255 °C. Meanwhile, ∼7 wt.% H₂ could be reached at 400 °C in 20LiBH₄–NbF₅ sample, whereas pristine LiBH₄ only released ∼0.7 wt.% H₂. In addition, reversibility measurement demonstrated that over 4.4 wt.% H₂ could still be released even during the fifth dehydrogenation in 20LiBH₄–NbF₅ sample. The experimental results suggested that a new borohydride possibly formed during ball milling the LiBH₄–NbF₅ mixtures might be the source of the active effect of NbF₅ on LiBH₄.     

Enhanced dehydrogenation and rehydrogenation properties of LiBH4 catalyzed by graphene

The investigation of thermally induced dehydrogenation of LiBH₄ reveals that LiBH₄ doped with the graphene catalysts shows superior dehydrogenation and rehydrogenation performance to that of Vulcan XC-72, carbon nanotube and BP2000 doped LiBH₄. For doping with 20 wt.% graphene, thermal dehydrogenation of LiBH₄ is found to start at ca. 230 °C and a total weight loss of 11.4 wt.% can be obtained below 700 °C. With increased loading of graphene within a LiBH₄ sample, the onset dehydrogenation temperature and the two main desorption peaks from LiBH₄ are found to decrease while the hydrogen release amount is found to increase. Moreover, variation of the equilibrium pressure obtained from isotherms measured at 350–450 °C indicate the dehydrogenation enthalpy is reduced from 74 kJ mol⁻¹ H₂ for pure LiBH₄ to ca. 40 kJ mol⁻¹ H₂ for 20 wt.% graphene doped LiBH₄. Importantly, the reversible dehydrogenation/rehydrogenation process was achieved under 3 MPa H₂ at 400 °C for 10 h, with a capacity of ca. 4.0 wt.% in the tenth cycle. Especially, LiBH₄ is reformed and new species, Li₂B₁₀H₁₀, is detected after the rehydrogenation process.     

Effective nanoconfinement of 2LiBH4–MgH2 via simply MgH2 premilling for reversible hydrogen storages

To improve nanoconfinement of LiBH₄ and MgH₂ in carbon aerogel scaffold (CAS), particle size reduction of MgH₂ by premilling technique before melt infiltration is proposed. MgH₂ is premilled for 5 h prior to milling with LiBH₄ and nanoconfinement in CAS to obtained nanoconfined 2LiBH₄–premilled MgH₂. Significant confinement of both LiBH₄ and MgH₂ in CAS, confirmed by SEM–EDS–mapping results, is achieved due to MgH₂ premilling. Due to effective nanoconfinement, enhancement of CAS:hydride composite weight ratio to 1:1, resulting in increase of hydrogen storage capacity, is possible. Nanoconfined 2LiBH₄–premilled MgH₂ reveals a single–step dehydrogenation at 345 °C with no B₂H₆ release, while dehydrogenation of nanoconfined sample without MgH₂ premilling performs in multiple steps at elevated temperatures (up to 430 °C) together with considerable amount of B₂H₆ release. Activation energy (E_A) for the main dehydrogenation of nanoconfined 2LiBH₄–premilled MgH₂ is considerably lower than those of LiBH₄ and MgH₂ of bulk 2LiBH₄–MgH₂ (ΔE_A = 31.9 and 55.8 kJ/mol with respect to LiBH₄ and MgH₂, respectively). Approximately twice faster dehydrogenation rate are accomplished after MgH₂ premilling. Three hydrogen release (T = 320 °C, P(H₂) = 3–4 bar) and uptake (T = 320–325 °C, P(H₂) = 84 bar) cycles of nanoconfined 2LiBH₄–premilled MgH₂ reveal up to 4.96 wt. % H₂ (10 wt. % H₂ with respect to hydride composite content), while the 1st desorption of nanoconfined sample without MgH₂ premilling gives 4.30 wt. % of combined B₂H₆ and H₂ gases. It should be remarked that not only kinetic improvement and B₂H₆ suppression are obtained by MgH₂ premilling, but also the lowest dehydrogenation temperature (T = 320 °C) among other modified 2LiBH₄–MgH₂ systems is acquired.     

Reversible dehydrogenation of Mg(BH4)2–LiH composite under moderate conditions

The Mg(BH₄)₂-xLiH (0.1 ≤ x ≤ 0.8) composites which exhibit favorable dehydrogenation and encouraging reversibility are experimentally investigated. LiH additive reduces the onset temperature for dehydrogenation to 150 °C. And hydrogen release exceeds 10 wt.% from the new binary material below 250 °C. Furthermore, rehydrogenation results show that 3.6 wt.% hydrogen can still be recharged after twenty cycles at 180 °C. It should be emphasized that the long-term reversibility of borohydride under 200 °C is long overdue. TPD, PCT, and high-pressure DSC measurements are used to characterize the improvements in thermodynamic and kinetic ways. In addition, FT-IR and NMR studies indicate that the composite has a significant synergistic effect during (de)hydrogenation processes. This work suggests that controlled cation stoichiometry combined with doping by metal Li⁺ subvalent to Mg²⁺ facilitate the formation of polyborane intermediates [B₃H₈]⁻ and [B₂H₆]²⁻. They improve the dehydrogenation properties and make the material reversible under mild conditions.     

Superior dehydrogenation performance of nanoscale lithium borohydride modified with fluorographite

A significant enhancement in the dehydrogenation performance of LiBH₄ is achieved by modifying with fluorographite (FGi). In-depth investigations show that the dehydrogenation thermodynamics and kinetics of LiBH₄ are strongly improved by ball milling LiBH₄ with FGi. The ball-milled LiBH₄–FGi (mass ratio of 1:1) composite starts to release hydrogen without impurity gas at around 180 °C, and obtains a hydrogen desorption capacity of 7.2 wt% below 200 °C in seconds, which is improved dramatically compared with pristine ball-milled LiBH₄. Microscopic morphology indicates that numerous ∼90 nm spots formed on the surface of FGi. Based on the microstructure analyses combined with hydrogen storage performances, the prominent effect of FGi is largely attributed to the nano-modifying effect and the exothermic reaction between LiBH₄ and FGi during the dehydrogenation process. Furthermore, partial reversibility of the LiBH₄–FGi composite has been demonstrated and the mechanism underlying the cycling capacity loss is discussed. The use of FGi may shed light on future study on searching for new strategies to improve both the thermodynamics and kinetics of light-metal complex hydrides.     

Enhanced dehydrogenation properties of LiBH4 compositing with hydrogenated magnesium-rare earth compounds

LiBH₄ is regarded as a promising hydrogen storage material due to its high hydrogen density. In this study, the dehydrogenation properties of LiBH₄ were remarkably enhanced by doping hydrogenated Mg₃RE compounds (RE denotes La, Ce, Nd rare earth metals), which are composed of nanostructured MgH₂ and REH_2+x (denoted as H − Mg₃RE). For the LiBH₄ + H − Mg₃La mixture, the component LiBH₄ desorbed 6 wt.% hydrogen even at a relatively low temperature of 340 °C, far lower than the desorption temperature of pure LiBH₄ or the 2LiBH₄ + MgH₂ system. This kinetic improvement is attributed to the hydrogen exchange mechanism between the H − Mg₃La and LiBH₄, in the sense that the decomposition of MgH₂ and LaH_2+x catalyzed the dehydrogenation of LiBH₄ through hydrogen exchange effect rather than mutual chemical reaction requiring higher temperature and hydrogen pressure. However, prior to fast hydrogen release, the hydrogen exchange effect suppressed the dehydriding of MgH₂ and elevated its desorption temperature. It is expected to strengthen the hydrogen exchange effect by compositing the LiBH₄ with other nanosized metal hydrides and to obtain better dehydrogenation properties.     

Reversibility aspect of lithium borohydrides

Reversibility is one of the key features for any hydrogen storage material. Borohydrides such as LiBH₄ have been studied or proposed as candidates for hydrogen storage because of their high hydrogen contents (18.4 wt% for LiBH₄). Limited success has been made in reducing the dehydrogenation temperature. However, full reversibility has not been realized. It is found that the dehydrogenation mechanism of metal borohydrides differs signicantly from the well-known metal hydrides such as LaNi₅H₆ and MgH₂ that release hydrogen in a single decomposition step through a solid state transformation of crystalline structure. The dehydrogenation of lithium borohydrides involves solid–liquid–gas reactions. Some of the steps in the multiple step decomposition processes of metal borohydrides are not reversible. Furthermore, the decomposition also produces stable intermediate compounds that cannot be rehydrided easily. Lastly, the volatile gases, such as BH₃ and B₂H₆, evolved in decomposition of the transition metal borohydrides cause unrecoverable boron loss. Although our experiments show the partial reversibility of the doped LiBH₄, it was not sustainable during dehydriding–rehydriding cycles because of the accumulation of hydrogen inert species and boron loss. Doping with additives reduces the stability of LiBH₄, but it also makes LiBH₄ less reversible. It raises reasonable doubt on the feasibility of making metal borohydrides suitable for reversible hydrogen storage.     

Effects of MoS2 addition on the hydrogen storage properties of 2LiBH4–MgH2 systems

A 2LiBH₄–MgH₂–MoS₂ composite was prepared by solid-state ball milling, and the effects of MoS₂ as an additive on the hydrogen storage properties of 2LiBH₄–MgH₂ system together with the corresponding mechanism were investigated. As shown in the TG–DSC and MS results, with the addition of 20 wt.% of MoS₂, the onset dehydrogenation temperature is reduced to 206 °C, which is 113 °C lower than that of the pristine 2LiBH₄–MgH₂ system. Meanwhile, the total dehydrogenation amount can be increased from 9.26 wt.% to 10.47 wt.%, and no gas impurities such as B₂H₆ and H₂S are released. Furthermore, MoS₂ improves the dehydrogenation kinetics, and lowers the activation energy (E_a) 34.49 kJ mol⁻¹ of the dehydrogenation reaction between Mg and LiBH₄ to a value lower than that of the pristine 2LiBH₄–MgH₂ sample. According to the XRD test, Li₂S and MoB₂ are formed by the reaction between LiBH₄ and MoS₂, which act as catalysts and are responsible for the improved hydrogen storage properties of the 2LiBH₄–MgH₂ system.     

Improved hydrogen storage properties of LiBH4 doped Li–N–H system

Remarkable improvement of hydrogen sorption properties of Li–N–H system has been obtained by doping with a small amount of LiBH₄. The starting and ending temperatures of hydrogen desorption shift to lower temperatures and the release of NH₃ is obviously restrained by 10 mol% LiBH₄ doping. The kinetics of hydrogen desorption and absorption of Li–N–H system became faster by the addition of LiBH₄. About 4 wt.% H₂ can be released within 30 min and ∼4.8 wt.% H₂ can be reabsorbed within 2 min by LiBH₄ doped sample at 250 °C, while only 1.44 wt.% H₂ is released and 2.1 wt.% is reabsorbed for pure Li–N–H system. The quaternary hydride (LiNH₂)_x(LiBH₄)_(1−x) formed by the reaction between LiBH₄ and LiNH₂ may contribute to the enhancement of the hydrogen sorption performances by yielding a ionic liquid phase and transferring LiNH₂ from solid state to molten state with a weakened N–H bond.     

Improved hydrogen storage performance of the LiNH2–MgH2–LiBH4 system by addition of ZrCo hydride

Significant improvements in the hydrogen absorption/desorption properties of the 2LiNH₂–1.1MgH₂–0.1LiBH₄ composite have been achieved by adding 3wt% ZrCo hydride. The composite can absorb 5.3wt% hydrogen under 7.0 MPa hydrogen pressure in 10 min and desorb 3.75wt% hydrogen under 0.1 MPa H₂ pressure in 60 min at 150 °C, compared with 2.75wt% and 1.67wt% hydrogen under the same hydrogenation/dehydrogenation conditions without the ZrCo hydride addition, respectively. TPD measurements showed that the dehydrogenation temperature of the ZrCo hydride-doped sample was decreased about 10 °C compared to that of the pristine sample. It is concluded that both the homogeneous distribution of ZrCo particles in the matrix observed by SEM and EDS and the destabilized N–H bonds detected by IR spectrum are the main reasons for the improvement of H-cycling kinetics of the 2LiNH₂–1.1MgH₂–0.1LiBH₄ system.     

Destabilization of LiBH4 by nanoconfinement in PMMA–co–BM polymer matrix for reversible hydrogen storage

Destabilization of LiBH₄ by nanoconfinement in poly (methyl methacrylate)–co–butyl methacrylate (PMMA–co–BM), denoted as nano LiBH₄–PMMA–co–BM, is proposed for reversible hydrogen storage. The onset dehydrogenation temperature of nano LiBH₄–PMMA–co–BM is reduced to ∼80 °C (ΔT = 340 and 170 °C as compared with milled LiBH₄ and nanoconfined LiBH₄ in carbon aerogel, respectively). At 120 °C under vacuum, nano LiBH₄–PMMA–co–BM releases 8.8 wt.% H₂ with respect to LiBH₄ content within 4 h during the 1st dehydrogenation, while milled LiBH₄ performs no dehydrogenation at the same temperature and pressure condition. Moreover, nano LiBH₄–PMMA–co–BM can be rehydrogenated at the mildest condition (140 °C under 50 bar H₂ for 12 h) among other modified LiBH₄ reported in the previous literature. Due to the hydrophobicity of PMMA–co–BM host, deterioration of LiBH₄ by oxygen and humidity in ambient condition is avoided after nanoconfinement. Although the interaction between LiBH₄ and the pendant group of PMMA–co–BM leads to a reduced hydrogen storage capacity, significant destabilization of LiBH₄ is accomplished.     

Improved hydrogen storage reversibility of LiBH4 destabilized by Y(BH4)3 and YH3

In the present study, the synthesis of two different LiBH₄–Y(BH₄)₃ and LiBH₄–YH₃ composites was performed by mechanochemical processing of the 4LiBH₄–YCl₃ mixture and as-milled 4LiBH₄–YCl₃ plus 3LiH. It was found that Y(BH₄)₃ and YH₃ formed in situ during milling are effective to promote LiBH₄ destabilization but differ substantially from each other in terms of the dehydrogenation pathway. During LiBH₄–Y(BH₄)₃ dehydriding, Y(BH₄)₃ decomposes first generating in situ freshly YH₃ and subsequently, it destabilizes LiBH₄ with the formation of minor amounts of YB₄. About 20% of the theoretical hydrogen storage was obtained via the rehydriding of YB₄–4LiH–3LiCl at 400 °C and 6.5 MPa. As a novel result, a compound containing (B₁₂H₁₂)²⁻ group was identified during dehydriding of Y(BH₄)₃. In the case of 4LiBH₄–YH₃ dehydrogenation, the increase of the hydrogen back pressure favors the formation of crystalline YB_4, whereas a reduction to ≤0.1 MPa induces the formation of minor amounts of Li₂B₁₂H₁₂. Although for hydrogen pressures ≤0.1 MPa direct LiBH₄ decomposition can occur, the main dehydriding pathway of 4LiBH₄–YH₃ composite yields YB₄ and LiH. The nanostructured composite obtained by mechanochemical processing gives good hydrogen storage reversibility (about 80%) regardless of the hydrogen back pressure.     

Hydrogen storage behavior of 2LiBH4/MgH2 composites improved by the catalysis of CoNiB nanoparticles

2LiBH₄/MgH₂ system is a representative and promising reactive hydride composite for hydrogen storage. However, the high desorption temperature and sluggish desorption kinetics hamper its practical application. In our present report, we successfully introduce CoNiB nanoparticles as catalysts to improve the dehydrogenation performances of the 2LiBH₄/MgH₂ composite. The sample with CoNiB additives shows a significant desorption property. Temperature programmed desorption (TPD) measurement demonstrates that the peak decomposition temperatures of MgH₂ and LiBH₄ are lowered to be 315 °C and 417 °C for the CoNiB-doped 2LiBH₄/MgH₂. Isothermal dehydrogenation analysis demonstrates that approximately 10.2 wt% hydrogen can be released within 360 min at 400 °C. In addition, this study gives a preliminary evidence for understanding the CoNiB catalytic mechanism of 2LiBH₄/MgH₂     

Enhanced desorption properties of LiBH4 incorporated into mesoporous TiO2

LiBH₄ nano-particles are incorporated into mesoporous TiO₂ scaffolds via a chemical impregnation method. And the enhanced desorption properties of the composite have been investigated. The LiBH₄/TiO₂ sample starts to release hydrogen at 220 °C and the maximal desorption peak occurs at about 330 °C, much lower compared to the bulk LiBH₄. Furthermore, the composite exhibits excellent dehydrogenation kinetics, with 11 wt% of hydrogen liberated from LiBH₄ at 300 °C within 3 h. X-ray diffraction and Fourier transform infrared spectroscopy are used to confirm the nanostructure of LiBH₄ in the TiO₂ scaffold. This work demonstrates that confinement within active porous scaffold host is a promising approach for enhancing hydrogen decomposition properties of light-metal complex hydrides.     

Thermal dehydrogenation behaviors and mechanisms of Mg(BH4)2∙6NH3-xLiH combination systems

A reactive composite of Mg(BH₄)₂⋅6NH₃-xLiH is prepared, and the effects of the LiH content on the dehydrogenation/hydrogenation properties of the material are investigated. The results show that the presence of LiH with x = 3 reduces the onset dehydrogenation temperature of Mg(BH₄)₂⋅6NH₃ from 130 °C to 80 °C in TPD mode. Approximately 14.3 wt% hydrogen is released from the Mg(BH₄)₂⋅6NH₃-6LiH composite with distinctly reduced ammonia evolution while heating to 340 °C. Upon heating, Mg(BH₄)₂⋅6NH₃ first reacts with LiH to form Mg(NH₂)₂, Li₃BN₂H₈ and LiBH₄ with the release of H₂ and the evolution of a minor amount of NH₃. The newly formed Mg(NH₂)₂ then reacts with LiH to produce H₂ and Li₂Mg(NH)₂. Further elevating the operating temperature induces chemical reactions between Li₂Mg(NH)₂, LiBH₄ and Li₃BN₂H₈, causing the release of additional H₂ and production of Li₃BN₂, LiMgBN₂ and LiH. The dehydrogenated sample at 210 °C absorbs 2.2 wt% of hydrogen, exhibiting partial reversibility for hydrogen storage.     

Comprehensive hydrogen storage properties and catalytic mechanism studies of 2LiBH4–MgH2 system with NbF5 in various addition amounts

In the present work, the role of NbF₅ addition amount in affecting the comprehensive hydrogen storage properties (dehydrogenation, rehydrogenation, cycling performance, hydrogen capacity) of 2LiBH₄–MgH₂ system as well as the catalytic mechanism of NbF₅ have been systematically studied. It is found that increasing the addition amount of NbF₅ to the 2LiBH₄–MgH₂ system not only results in dehydrogenation temperature reduction and hydriding–dehydriding kinetics enhancement but also leads to the de/rehydrogenation capacity loss. Compared with other samples, 2LiBH₄–MgH₂ doping with NbF₅ in weight ratios of 40:4 exhibits superior comprehensive hydrogen storage properties, which can stably release ∼8.31 wt.% hydrogen within 2.5 h under 4 bar H₂ and absorb ∼8.79 wt.% hydrogen within 10 min under 65 bar H₂ at 400 °C even up to 20 cycling. As far as we know, this is the first time that excellent reversibility as high as 20 cycles without obvious degradation tendency in both of hydrogen capacity and reaction rate has been achieved in the 2LiBH₄–MgH₂ system. The further experimental study reveals that the highly catalytic effects of NbF₅ on the 2LiBH₄–MgH₂ system are derived from the reaction between NbF₅ and LiBH₄, which provides a fundamental insight into the catalytic mechanism of NbF₅.     

Enhanced reversible hydrogen storage performance of NbCl5 doped 2LiH–MgB2 composite

2LiBH₄ + MgH₂ system is considered as an attractive candidate for reversible hydrogen storage with high capacity and favorable thermodynamics. However, its reaction kinetics has to be further improved for the practical application. In this work, we investigated the effect of NbCl₅ additive on the de/hydrogenation kinetics and microstructure refinement in 2LiH–MgB₂ composite systematically. The hydrogenation and dehydrogenation kinetics of 2LiH–MgB₂ composite can be significantly enhanced with the increase of NbCl₅ content. The 3 mol% NbCl₅ doped 2LiH–MgB₂ composite exhibits the superior reversible hydrogen storage performance, which requires 50 min to uptake 9.0 wt% H₂ at 350 °C and release 8.5 wt% H₂ at 400 °C, respectively. In contrast, the undoped 2LiH–MgB₂ sample uptakes 6.2 wt% H₂ and releases 3.1 wt% H₂ under identical measurement conditions. Moreover, the 3 mol% NbCl₅ doped 2LiH–MgB₂ composite can release more than 9.0 wt% H₂ within 300 min at 400 °C without obvious degradation of capacity over the first 10 cycles. Microstructure analyses clearly indicate that NbCl₅ additive first reacts with LiH to form Nb and LiCl during ball-milling process, and then NbH is formed after the first hydrogenation and stabilized upon further de/hydrogenation cycling. The well-distributed NbH active species play an important role in the improvement of de/hydrogenation kinetics for Li–Mg–B–H system through facilitating hydrogen diffusion rapidly as well as prevent the particles from further growth in the subsequent hydrogenation and dehydrogenation processes.     

Remarkable decrease in dehydrogenation temperature of Li–B–N–H hydrogen storage system with CoO additive

Cobalt monoxide (CoO) was introduced into the Li–B–N–H system as a catalyst precursor, and the hydrogen desorption behavior of the LiBH₄–2LiNH₂–xCoO (x = 0–0.20) composites was investigated. It was observed that the majority of hydrogen desorption from the CoO-added sample occurred simultaneously with the melting of α-Li₄BN₃H₁₀. Moreover, the 0.05CoO-added sample exhibited optimized dehydrogenation properties, desorbing 9.9 wt% hydrogen completely with an onset temperature of 100 °C and exhibiting a decrease of more than 120 °C in the onset dehydrogenation temperature with respect to that of the additive-free sample. The activation energy of hydrogen desorption for the 0.05CoO-added sample was reduced by 30%. XAFS measurements showed that the CoO additive was first reduced chemically to metallic Co during the initial stage of thermal dehydrogenation, and the newly produced metallic Co acted as the catalytic active species in favor of the creation of B–N bonding. More importantly, approximately 1.1 wt% of hydrogen could be recharged into the fully dehydrogenated 0.05CoO-added sample at 350 °C and a hydrogen pressure of 110 atm, which represents much better performance than that exhibited by the pristine sample.