An effective route based on space-confined chemical reaction to synthesize uniform Li2Mg(NH)2 nanoparticles is reported. The hierarchical pores inside the one-dimensional carbon nanofibers (CNFs), induced by the creation of well-dispersed Li3N, serve as intelligent nanoreactors for the reaction of Li3N with Mg-containing precursors, resulting in the formation of uniformly discrete Li2Mg(NH)2 nanoparticles. The nanostructured Li2Mg(NH)2 particles inside the CNFs are capable of complete hydrogenation and dehydrogenation at a temperature as low as 105 °C with the suppression of ammonia release. Furthermore, by virtue of the nanosize effects and space-confinement by the porous carbon scaffold, no degradation was observed after 50 de/rehydrogenation cycles at a temperature as low as 130 °C for the as-prepared Li2Mg(NH)2 nanoparticles, indicating excellent reversibility. Moreover, the theoretical calculations demonstrate that the reduction in particle size could significantly enhance the H2 sorption of Li2Mg(NH)2 by decreasing the relative activation energy barrier, which agrees well with our experimental results. This method could represent an effective, general strategy for synthesizing nanoparticles of complex hydrides with stable reversibility and excellent hydrogen storage performance.Keywords: amide; carbon nanofibers; cycle; hydrogen storage; nanoparticles;
Co-reporter:X. B. Yu;Y. H. Guo;D. L. Sun;Z. X. Yang;A. Ranjbar;Z. P. Guo;H. K. Liu;S. X. Dou
The Journal of Physical Chemistry C March 18, 2010 Volume 114(Issue 10) pp:4733-4737
Publication Date(Web):2017-2-22
DOI:10.1021/jp910547s
The decomposition properties of Mg(BH4)2−LiNH2 mixtures were investigated. Apparent NH3 release appeared from 50 to 300 °C for the Mg(BH4)2−LiNH2 mixtures with mole ratios of 1:1.5, 1:2, and 1:3, while only hydrogen release was detected for the mixture with a mole ratio of 1:1. In the case of the Mg(BH4)2−LiNH2 (1:1) sample, the onset of the first-step dehydrogenation starts at 160 °C, with a weight loss of 7.2 wt % at ∼300 °C, which is improved significantly compared to the pure Mg(BH4)2 alone. From Kissinger’s method, the activation energy, Ea, for the first and second step dehydrogenation in Mg(BH4)2−LiNH2 (1:1) was estimated to be about 121.7 and 236.6 kJ mol−1, respectively. The improved dehydrogenation in the combined system may be ascribed to a combination reaction between [BH4] and [NH2], resulting in the formation of Li−Mg alloy and amorphous B−N compound.
CoS and NiS nanomaterials anchored on reduced graphene oxide (rGO) sheets, synthesized via combination of hydrothermal with sulfidation process, are studied as high-capacity anode materials for the reversible lithium storage. The obtained CoS nanofibers and NiS nanoparticles are uniformly dispersed on rGO sheets without aggregation, forming the sheet-on-sheet composite structure. Such nanoarchitecture can not only facilitate ion/electron transport along the interfaces, but also effectively prevent metal-sulfide nanomaterials aggregation during the lithium reactions. Both the rGO-supported CoS nanofibers (NFs) and NiS nanoparticles (NPs) show superior lithium storage performance. In particular, the CoS NFs-rGO electrodes deliver the discharge capacity as high as 939 mA h g–1 after the 100th cycle at 100 mA g–1 with Coulombic efficiency above 98%. This strategy for construction of such composite structure can also synthesize other metal-sulfide-rGO nanomaterials for high-capacity lithium-ion batteries.Keywords: anode materials; lithium-ion batteries; metal-sulfide nanomaterials; nanofibers; reduced graphene oxide;
Co-reporter:Xuebin Yu, Ziwei Tang, Dalin Sun, Liuzhang Ouyang, Min Zhu
Progress in Materials Science 2017 Volume 88(Volume 88) pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.pmatsci.2017.03.001
The rapid and extensive development of advanced nanostructures and nanotechnologies has driven a correspondingly rapid growth of research that presents enormous potential for fulfilling the practical requirements of solid state hydrogen storage applications. This article reviews the most recent progress in the development of nanostructured materials for hydrogen storage technology, demonstrating that nanostructures provide a pronounced benefit to applications involving molecular hydrogen storage, chemical hydrogen storage, and as supports for the nanoconfinement of various hydrides. To further optimize hydrogen storage performance, we emphasize the desirability of exploring and developing nanoporous materials with ultrahigh surface areas and the advantageous incorporation of metals and functionalities, nanostructured hydrides with excellent mechanic stabilities and rigid main construction, and nanostructured supports comprised of lightweight components and enhanced hydride loading capacities. In addition to highlighting the conspicuous advantages of nanostructured materials in the field of hydrogen storage, we also discuss the remaining challenges and the directions of emerging research for these materials.
International Journal of Hydrogen Energy 2017 Volume 42, Issue 39(Volume 42, Issue 39) pp:
Publication Date(Web):28 September 2017
DOI:10.1016/j.ijhydene.2017.08.100
•LiBH4·NH3 shows low NH3 vacancy formation energy and diffusion barrier.•[Al(NH3)6][BH4]3 and [Li2Al(NH3)6][BH4]5 show high NH3 diffusion barrier.•The H2 formation energy barriers agree with tendency of H2 release temperature.The decomposition mechanisms of [Li(NH3)][BH4], [Al(NH3)6][BH4]3 and [Al(NH3)6][Li2(BH4)5] were investigated using Density functional theory (DFT) calculation. The calculated results show that [Li(NH3)][BH4] has low NH3 vacancy formation energy and diffusion barrier, therefore ammonia would easily release at relatively low temperature. Both [Al(NH3)6][BH4]3 and [Al(NH3)6][Li2(BH4)5] show relatively high NH3 vacancy formation energies and diffusion barriers, which avoid ammonia release at low temperature. In addition, the calculated H2 formation energy barriers, i.e., [Al(NH3)6][Li2(BH4)5] < [Al(NH3)6][BH4]3 < [Li(NH3)][BH4], are in agreement with the tendency of dehydrogenation temperatures determined experimentally. The incorporation of [BH4]− into [Al(NH3)6][BH4]3 play an important role in decreasing the dehydrogenation temperature and improving the hydrogen purity of [Al(NH3)6][Li2(BH4)5].Download high-res image (146KB)Download full-size image
Progress in Natural Science: Materials International 2017 Volume 27, Issue 1(Volume 27, Issue 1) pp:
Publication Date(Web):1 February 2017
DOI:10.1016/j.pnsc.2016.12.015
A simple solvent-free method to synthesize MgH2 nanoparticles (MgH2 NPs) uniformly grown on graphene nanosheets (GNs) has been reported in this paper. Based on the formation of MgH2 by di-n-butylmagnesium ((C4H9)2Mg) thermal decomposition under hydrogen pressure, the GNs were added as matrix to hinder the agglomeration and growing of MgH2 NPs. The fabricated MgH2/GNs nanocomposites, in which MgH2 NPs were homogenously growing in the graphene matrix, have been synthesized by the favorable adsorption energy between (C4H9)2Mg and GNs. Resulting from the one-step solvent-free route, the generated MgH2 NPs shows high hydrogen capacity and steady hydriding and dehydriding properties, without the interference of the synthetic medium. At the same time, the size of the fabricated MgH2 NPs can be controlled by adjusting the mass ratio of MgH2 to graphene, the various hydrogen pressure and temperature. Attributed to smaller size effect, well uniform distribution of high density MgH2 NPs, and the agglomeration blocking ability of graphene, the MgH2/GNs-40 wt% exhibits the favorite hydrogen storage performance.
The decomposition mechanisms of Mg(BH4)2·2NH3 and LiMg(BH4)3·2NH3 were studied by using density functional theory calculations. Compared to that of Mg(BH4)2·2NH3, the incorporation of LiBH4 with the formation of LiMg(BH4)3·2NH3 slightly increased Bader charges of B atoms, meanwhile it decreased Bader charges of N atoms. Mg(BH4)2·2NH3 shows a low ammonia vacancy diffusion barrier, but relatively high ammonia vacancy formation energy, which lead to a low concentration of NH3 vacancies and limit NH3 transportation. In contrast to that of Mg(BH4)2·2NH3, LiMg(BH4)3·2NH3 has a relatively high ammonia vacancy formation energy and diffusion barrier, which suppresses ammonia release. The incorporation of LiBH4 and Mg(BH4)2·2NH3 does not decrease but increases the hydrogen formation barrier of LiMg(BH4)3·2NH3, resulting in a slight increase in the dehydrogenation peak temperature, consistent with experimental results.
NaAlH4 has been widely regarded as a potential hydrogen storage material due to its favorable thermodynamics and high energy density. The high activation energy barrier and high dehydrogenation temperature, however, significantly hinder its practical application. In this paper, CeO2 hollow nanotubes (HNTs) prepared by a simple electrospinning technique are adopted as functional scaffolds to support NaAlH4 nanoparticles (NPs) towards advanced hydrogen storage performance. The nanoconfined NaAlH4 inside CeO2 HNTs, synthesized via the infiltration of molten NaAlH4 into the CeO2 HNTs under high hydrogen pressure, exhibited significantly improved dehydrogenation properties compared with both bulk and ball-milled CeO2 HNTs-catalyzed NaAlH4. The onset dehydrogenation temperature of the NaAlH4@CeO2 composite was reduced to below 100 °C, with only one main dehydrogenation peak appearing at 130 °C, which is 120 °C and 50 °C lower than for its bulk counterpart and for the ball-milled CeO2 HNTs-catalyzed NaAlH4, respectively. Moreover, ∼5.09 wt% hydrogen could be released within 30 min at 180 °C, while only 1.6 wt% hydrogen was desorbed from the ball-milled NaAlH4 under the same conditions. This significant improvement is mainly attributed to the synergistic effects contributed by the CeO2 HNTs, which could act as not only a structural scaffold to fabricate and confine the NaAlH4 NPs, but also as an effective catalyst to enhance the hydrogen storage performance of NaAlH4.
Journal of Power Sources 2016 Volume 324() pp:294-301
Publication Date(Web):30 August 2016
DOI:10.1016/j.jpowsour.2016.05.057
•Porous carbon nanofibers with high level of N, B co-doping have been constructed.•Ammonia borane functions as a porogen reagent to generate porous structures.•Ammonia borane functions as the heteroatoms source to induce N and B co-doping.•NB-PCNFs exhibit excellent electrochemical performance.This paper reports the fabrication of three-dimensional porous carbon nanofibers network with high doping level of nitrogen (N, 5.17 at.%) and boron (B, 6.87 at.%) through a general electrospinning strategy followed by a calcination process. The employed ammonia borane (NH3BH3, denote as AB) not only functions as a porogen reagent to generate porous structures but also as the heteroatoms source to induce N and B co-doping. Such highly unique nanoarchitectures offer remarkably improved Li storage performance including high reversible capacity (∼910 mAh g−1 at a current density of 100 mA g−1) with good cycling and rate performances.Three-dimensional porous carbon nanofibers networks with high level of N, B co-doping, constructed by electrospinning, exhibit a high reversible capacity as an anode material for rechargeable Li-ion batteries.
International Journal of Hydrogen Energy 2016 Volume 41(Issue 2) pp:733-739
Publication Date(Web):12 January 2016
DOI:10.1016/j.ijhydene.2015.11.025
•A new hydrogen storage system of CrCl3·nNH3/3LiBH4 (n = 3–5) was synthesized.•>0.5 mol ZnCl2 added CrCl3·3NH3/3LiBH4 showed the highest hydrogen purity of 98.8 mol%.•The high hydrogen purity is due to the added ZnCl2 that played a role in capturing NH3.Three new chromium-based ammine borohydrides were synthesized by ball milling CrCl3·nNH3 (n = 3–5) and LiBH4 in a molar ratio of 1:3. Thermogravimetric analysis–mass spectrometry (TG–MS) measurements showed that the chromium-based ammine borohydrides release H2 in the temperature range of 100–170 °C, concurrent with the evolution of a small amount of NH3 evolution. The dehydrogenation purity increases with decreasing coordination number of ammonia, with the highest dehydrogenation purity (91.8 mol%) achieved for CrCl3·3NH3/3LiBH4. Further improvement on the dehydrogenation of CrCl3·3NH3/3LiBH4 is conducted by the addition of ZnCl2. The 0.5 mol ZnCl2 assisted sample is able to release 7.4 wt.% of hydrogen with a purity of 98.8 mol%.Three new chromium-based ammine borohydrides were synthesized by ball milling CrCl3·nNH3 (n = 3–5) and LiBH4 in a molar ratio of 1:3. The chromium-based ammine borohydrides release H2 in the temperature range of 100–170 °C. With the assistance of 0.5 mol ZnCl2, the sample is able to release 7.4 wt.% of hydrogen with a purity of 98.8 mol%.
International Journal of Hydrogen Energy 2016 Volume 41(Issue 1) pp:407-412
Publication Date(Web):5 January 2016
DOI:10.1016/j.ijhydene.2015.10.136
•MNH2BH3 (M = Li, K) are reproduced in an unprecedentedly high purity of 98%.•A self-sufficient recycling system has been established.•Scission of dehydrogenated polymeric MNBH residues into small molecule B species is achievable.In this manuscript, we report a facile and safe process for highly efficient regeneration of dehydrogenated alkaline metal amidoboranes (MNH2BH3, MAB, M = Li, K), in which CH3OH is employed as a digestion reagent; then LiAlH4 is used as a reduction reagent in the presence of NH4Cl giving ammonia borane (NH3BH3, AB) as the intermediate; finally the generated AB reacts with corresponding metal hydride to complete the whole self-contained cycle. Using this chemical process, MABs are reproduced in a high purity of 98%. The byproducts of regeneration procedure can be converted to mass commodity chemicals as recyclable auxiliary reagents utilizing the recycling pathways. More importantly, our finding of successful scission of dehydrogenated polymeric MAB residues into small molecule B species that guarantees to facilitate the following regeneration process, provides a general strategy for the efficient regeneration for other MAB compounds and a potentially viable route for the chemical recycling of metal-B-N containing hydrogen storage materials.A high-efficient and self-sufficient recyclable regeneration strategy for the thermal dehydrogenation products of alkaline metal amidoboranes has been established successfully, achieving a high purity of 98%.
International Journal of Hydrogen Energy 2016 Volume 41(Issue 32) pp:14252-14260
Publication Date(Web):24 August 2016
DOI:10.1016/j.ijhydene.2016.06.016
•Porous carbon nanotubes webs with high level of boron and nitrogen co-doping has been synthesized.•Ammonia boranea was employed as an effective heteroatoms source to induce B and N co-doping in mild conditions.•BN-PCNTs exhibit high reversible capacity with good cycling and rate performances as anode materials in lithium ion batteries.This paper reports the fabrication of porous carbon nanotubes webs with high level of boron (15.05 at.%) and nitrogen (6.71 at.%) co-doping (denote as BN-PCNTs) by using polypyrrole (PPy) nanotubes as the precursor. Instead of using virulent boron hydride, ammonia borane (NH3BH3, denote as AB), a versatile and non-toxic agent, was employed as an effective heteroatoms sources to induce B and N co-doping in mild conditions. Benefiting from the porous nanotube structure and high-level B, N co-doping, the BN-PCNTs exhibit high reversible capacity (∼900 mAh g−1 at a current density of 200 mA g−1) with good cycling and rate performances as anode materials in lithium ion batteries.Porous carbon nanotubes with high level of N, B co-doping have been fabricated and exhibit a high reversible capacity as an anode material for rechargeable Li-ion batteries.
•Graphene-supported nanostructured 2LiBH4-MgH2 composite was synthesized.•Graphene-supported 2LiBH4-MgH2 nanocomposite exhibits well-defined structural features.•A reversible storage capacity of up to 8.9 wt% without degradation after 25 cycles was achieved at 350 °C.Here, we report the fabrication of a graphene-wrapped nanostructured reactive hydride composite, i.e., 2LiBH4-MgH2, made by adopting graphene-supported MgH2 nanoparticles (NPs) as the nanoreactor and heterogeneous nucleation sites. The porous structure, uniform distribution of MgH2 NPs, and the steric confinement by flexible graphene induced a homogeneous distribution of 2LiBH4-MgH2 nanocomposite on graphene with extremely high loading capacity (80 wt%) and energy density. The well-defined structural features, including even distribution, uniform particle size, excellent thermal stability, and robust architecture endow this composite with significant improvements in its hydrogen storage performance. For instance, at a temperature as low as 350 °C, a reversible storage capacity of up to 8.9 wt% H2, without degradation after 25 complete cycles, was achieved for the 2LiBH4-MgH2 anchored on graphene. The design of this three-dimensional architecture can offer a new concept for obtaining high performance materials in the energy storage field.
Co-reporter:Guanglin Xia, Xiaowei Chen, Cuifeng Zhou, Chaofeng Zhang, Dan Li, Qinfen Gu, Zaiping Guo, Huakun Liu, Zongwen Liu and Xuebin Yu
Journal of Materials Chemistry A 2015 vol. 3(Issue 24) pp:12646-12652
Publication Date(Web):14 May 2015
DOI:10.1039/C5TA00259A
A Li–Mg–N–H system is a highly promising source of hydrogen storage materials due to its favorable thermodynamics and potential reversibility. Its application has been greatly hindered, however, by its rather high activation energy barriers. Herein, we report a novel multi-reaction methodology for the synthesis of nanosized Li2Mg(NH)2 space-confined into thin-film hollow carbon spheres (THCSs) with a uniform dispersion. It shows that a completely depressed release of ammonia and reversible hydrogen sorption at a temperature of 105 °C, the lowest temperature reported so far, were achieved for the nano-confined Li2Mg(NH)2. Furthermore, a stable cycling capacity close to the theoretical value was also successfully realized, even through up to 20 cycles of de-/re-hydrogenation.
Co-reporter:Jianmei Huang, Yingbin Tan, Qinfen Gu, Liuzhang Ouyang, Xuebin Yu and Min Zhu
Journal of Materials Chemistry A 2015 vol. 3(Issue 10) pp:5299-5304
Publication Date(Web):18 Dec 2014
DOI:10.1039/C4TA05328A
A new complex system, Zr(BH4)4·8NH3–nNH3BH3 (n = 2, 3, 4, 5), was prepared via ball milling of Zr(BH4)4·8NH3 and NH3BH3 (AB). The combination strategy effectively suppressed ammonia release and reduced the dehydrogenation temperature when compared to the individual compounds. In the optimized composition, Zr(BH4)4·8NH3–4AB, the hydrogen purity was improved to 96.1 mol% and 7.0 wt% of hydrogen was released at 100 °C. These remarkable improvements are attributed to the interaction between AB and the NH3 group in Zr(BH4)4·8NH3, which enables a more active interaction of Hδ+⋯−δH. These advanced dehydrogenation properties suggest that Zr(BH4)4·8NH3–4AB is a promising candidate for potential hydrogen storage applications.
Co-reporter:Jie Chen, Guanglin Xia, Zaiping Guo, Zhenguo Huang, Huakun Liu and Xuebin Yu
Journal of Materials Chemistry A 2015 vol. 3(Issue 31) pp:15843-15848
Publication Date(Web):03 Jul 2015
DOI:10.1039/C5TA03721B
Porous Ni nanofibers (NFs) were synthesized via a single-nozzle electrospinning technique with subsequent calcination and reduction. The as-prepared continuous Ni NFs, with a uniform diameter of ∼50 nm and porous structure composed of a myriad of Ni nanocrystallites, were adopted to catalyze MgH2. The homogeneous distribution of Ni nanoparticles (NPs), obtained by ball milling Ni NFs with MgH2, on the surface of MgH2 offered effective catalytic sites to significantly enhance the hydrogen storage properties of MgH2. In particular, 4% Ni NF catalyzed MgH2 (MgH2–4% Ni NFs) starts to release hydrogen at only 143 °C, with a peak temperature of 244 °C, 157 °C and 96 °C lower than for MgH2 catalyzed with as-milled 4% Ni powders (MgH2–4% Ni powders), and it dehydrogenates completely within only 11 min at 325 °C (7.02 wt%). Compared with plain MgH2 and MgH2–4% Ni powders, the activation energy of the as-milled MgH2–4% Ni NF composite is significantly decreased to 81.5 kJ mol−1.
Co-reporter:Lijun Zhang, Guanglin Xia, Yu Ge, Caiyun Wang, Zaiping Guo, Xingguo Li and Xuebin Yu
Journal of Materials Chemistry A 2015 vol. 3(Issue 41) pp:20494-20499
Publication Date(Web):31 Aug 2015
DOI:10.1039/C5TA05540G
Borane–amine adducts (H3N·BH3, AB) in tetrahydrofuran solution were infiltrated into polypyrrole (PPy) nanotubes by a capillary effect, forming an ammonia borane (AB)@PPy combined system. This composite system combines the synergetic catalysis of nitrogen atoms with nanoconfinement in nanotubes, resulting in a significant improvement in the dehydrogenation properties. Dehydrogenation results showed that the AB loaded on PPy can release 15.3% hydrogen below 150 °C with an onset decomposition temperature as low as 48 °C. More importantly, the evolution of harmful ammonia, diborane, and borazine was entirely suppressed.
Co-reporter:Jianmei Huang, Yingbin Tan, Jiahao Su, Qinfen Gu, Radovan Černý, Liuzhang Ouyang, Dalin Sun, Xuebin Yu and Min Zhu
Chemical Communications 2015 vol. 51(Issue 14) pp:2794-2797
Publication Date(Web):11 Dec 2014
DOI:10.1039/C4CC09317H
A new metal borohydride ammoniate (MBA), Zr(BH4)4·8NH3, was synthesized via ammoniation of the Zr(BH4)4 crystal. Zr(BH4)4·8NH3 has a distinctive structure and the highest coordination number of NH3 groups among all the known MBAs. This compound could quickly dehydrogenate at 130 °C, enabling it a potential hydrogen storage material.
This paper reports a complete ammonia borane (AB) regeneration process in which Bu3SnH was utilized as a reductant for the reductive dechlorination of BCl3, and Et2PhN was selected as a ‘helper ligand’ to generate Et2PhN·BH3, which gives rise to a high yield of AB by a base-exchange reaction at ambient temperature.
Co-reporter:Lei Wan, Jie Chen, Yingbin Tan, Qinfen Gu, Xuebin Yu
International Journal of Hydrogen Energy 2015 Volume 40(Issue 2) pp:1047-1053
Publication Date(Web):12 January 2015
DOI:10.1016/j.ijhydene.2014.11.065
•Aluminum hydride was applied to improve dehydrogenation of ammonia borane.•A mutual dehydrogenation enhancement for both AB and AlH3 in the 3AB/AlH3 sample.•Over 12 wt% of high-pure hydrogen (>99 wt%) can be released from 3AB/AlH3 below 250 °C.Destabilized by aluminum hydride, the dehydrogenation properties of ammonia borane (AB) can be improved significantly, including enhanced dehydrogenation kinetics, reduced induction period and suppressed formation of volatile byproducts. Furthermore, a lowered dehydrogenation temperature was also achieved for AlH3, indicating a mutual dehydrogenation enhancement for both AB and AlH3 in this mixture. The destabilized sample, 3AB/AlH3,can totally release more than 12 wt% of high-pure hydrogen (>99 wt%) without any detectable by-products below 250 °C. Mechanism investigations indicated that the mutual dehydrogenation enhancement in the mixture is attributed to the Coulombic attraction between the hydridic Hδ− in AlH3 and the protonic Hδ+ in the NH3 group of AB.A novel modification strategy that destabilize AB with AlH3is employed to achieve a mutual enhancement for hydrogen release--> 12 wt. % pure H2 released below 250 °C for the 3AB/AlH3 sample.
Journal of Materials Chemistry A 2014 vol. 2(Issue 27) pp:10682-10687
Publication Date(Web):08 May 2014
DOI:10.1039/C4TA01631A
Three organic amine-boranes—diethylenetriamine-borane (C4H13N3·3BH3, DETAB), triethylenetetramine-borane (C6H18N4·4BH3, TETAB) and tetraethylenepentamine-borane (C8H23N5·5BH3, TEPAB)—are synthesized via the liquid-phase reaction of diethylenetriamine (C4H13N3, DETA), triethylenetetramine (C6H18N4, TETA) and tetraethylenepentamine (C8H23N5, TEPA), respectively, with BH3–THF solution. By using high-resolution synchrotron powder X-ray diffraction (HR-XRD), Fourier transform infrared (FTIR), elemental analysis and solid-state 11B nuclear magnetic resonance (NMR) measurements, the structural properties of the three compounds are characterized. Hydrogen desorption properties of these compounds are measured by temperature-programmed desorption (TPD) and thermogravimetry (TG) over a temperature range from 50 to 250 °C, in which 5.5, 6.6 and 6.9 equivalents hydrogen are released in two steps based on the combination of protic (N–H) and hydridic (B–H) hydrogens. It is confirmed by mass spectrometry (MS) results that only H2 is liberated during the thermal decomposition of the three compounds. The dynamics are investigated by isothermal dehydrogenation at various temperatures. Compared with ammonia borane (NH3BH3, AB), these compounds show a faster dehydrogenation rate. A regeneration study shows that DETAB can be regenerated by treating its dehydrogenated products with lithium aluminium hydride (LiAlH4) and ammonium chloride (NH4Cl) at room temperature.
Co-reporter:Yingbin Tan, Xiaowei Chen, Jie Chen, Qinfen Gu and Xuebin Yu
Journal of Materials Chemistry A 2014 vol. 2(Issue 37) pp:15627-15632
Publication Date(Web):16 Jul 2014
DOI:10.1039/C4TA02842B
The intermolecular interactions of N–H⋯B–H (proton–hydride) have been considered to mediate the release of hydrogen from B–N-based complexes. Mass spectroscopy studies on the thermal decomposition of isotopomer α-LiN2H3BD3, however, indicate that the initial dehydrogenation occurs through a homopolar N–H⋯H–N (proton–proton) pathway, followed by the N–H⋯B–H (proton–hydride) and B–H⋯B–H (hydride–hydride) pathways. The unexpected scission of the N–H bonds prior to B–H bonds can be attributed to the molecular structure of Li[NH2–NH–BH3], in which the detachment of the (N)H atoms results in a significant reduction of the N–N and N–B bond length, hence reducing the (N)H detachment energy. The scission of N–H bonds further facilitates the detachment of the (B)H atom, therefore, promoting the following proton–hydride and hydride–hydride dehydrogenation pathways.
Co-reporter:Guanglin Xia, Jie Chen, Weiwei Sun, Yingbin Tan, Zaiping Guo, Huakun Liu and Xuebin Yu
Nanoscale 2014 vol. 6(Issue 21) pp:12333-12339
Publication Date(Web):15 Aug 2014
DOI:10.1039/C4NR03257H
Well-distributed lithium amidoborane (LiAB) nanoparticles were successfully fabricated via adopting carbon nanofibers (CNFs) with homogenous pores uniformly containing Li3N as the nanoreactor and reactant, simply prepared by a single-nozzle electrospinning technique, for the subsequent interaction with AB. The hierarchical porous structure consists of various macropores, mesopores and micropores in situ produced during the formation of Li3N simultaneously serving as the reaction initiator, which not only controllably realizes the well-distribution of LiAB nanoparticles but also provides favorable channels for hydrogen release. Because of the hierarchical porous architecture and nanoscale size effects, the LiAB nanoparticles start to release hydrogen at only 40 °C, which is 30 °C lower than that of pure LiAB, and dehydrogenate completely within only 15 min at 100 °C (10.6 wt%). This work provides a new perspective to the controllable fabrication of nanosized hydrogen storage materials.
Co-reporter:Xiaowei Chen, Lei Wan, Jianmei Huang, Liuzhang Ouyang, Min Zhu, Zaiping Guo, Xuebin Yu
Carbon 2014 Volume 68() pp:462-472
Publication Date(Web):March 2014
DOI:10.1016/j.carbon.2013.11.022
The first-principles calculations demonstrate that nitrogen-containing carbon nanostructures (NCCN), such as nitrogen-doped graphene, nitrogen-doped carbon nanotubes, and covalent triazine-based framework (CTF) are promising metal-free catalysts for the first step dehydrogenation of ammonia borane (AB). It reveals that nitrogen lone pairs in NCCN function as hydrogen acceptors to allow metal-free hydrogen transfer from AB to NCCN, resulting in facile release of pure H2 from AB. The dehydrogenation of AB–NCCN combined systems involves two key steps: First, there is a net transfer of hydrogen atoms from AB to NCCN that results in simultaneous dehydrogenation of AB and hydrogenation of the NCCN, and then, the hydrogenated NCCN further react with AB to release H2 with relatively low reaction barriers. The experimental results further confirm that the CTF can act as effective catalysts for AB dehydrogenation at relatively low temperature. Our study leads to a promising scheme that can be readily tailored for application to many nitrogen-containing nanostructure systems that may favorably catalyze the dehydrogenation of ammonia borane and other related boron–nitrogen species.
International Journal of Hydrogen Energy 2014 Volume 39(Issue 22) pp:11668-11674
Publication Date(Web):24 July 2014
DOI:10.1016/j.ijhydene.2014.05.143
•A combined systems of NaZn(BH4)3·2NH3-nAB (n = 1–5) was synthesized.•NaZn(BH4)3·2NH3-4AB showed the best dehydrogenation property.•NH3 group plays a vital role in decreasing the dehydrogenation temperature.A new hydrogen storage system NaZn(BH4)3∙2NH3-nNH3BH3 (n = 1–5) was synthesized via a simple ball milling of NaZn(BH4)3∙2NH3 and NH3BH3 (AB) with a molar ratio from 1 to 5. Dehydrogenation results revealed that NaZn(BH4)3∙2NH3-nAB (n = 1–5) showed a mutual dehydrogenation improvement in terms of significant decrease in the dehydrogenation temperature and preferable suppression of the simultaneous evolution of by-products (i.e. NH3, B2H6 and borazine) compared to the unitary compounds (NaZn(BH4)3∙2NH3 and AB). Specially, the NaZn(BH4)3∙2NH3-4AB sample is shown to reach the maximum hydrogen purity (99.1 mol %) and favorable dehydrogenation properties rapidly releasing 11.6 wt. % of hydrogen with a peak maximum temperature of 85 °C upon heating to 250 °C. Isothermal dehydrogenation results revealed that 9.6 wt. % hydrogen was liberated from NaZn(BH4)3∙2NH3-4AB within 80 min at 90 °C. High-resolution in-situ XRD and Fourier transform infrared (FT-IR) measurements indicated that the significant improvements on the dehydrogenation properties in NaZn(BH4)3∙2NH3-4AB can be attributed to the interaction between the NH3 group from NaZn(BH4)3∙2NH3 and AB in the mixture, resulting a more activated Hδ+···−δH combination. The research on the reversibility of the spent fuels of NaZn(BH4)3∙2NH3-4AB showed that regeneration could be partly achieved by reacting them with hydrazine in liquid ammonia. These aforementioned favorable dehydrogenation properties demonstrate the potential of the combined systems to be used as solid hydrogen storage material.The combined systems of NaZn(BH4)3·2NH3-nAB (n=1–5) showed favorable dehydrogenation properties, with 9.6 wt. % of hydrogen liberated below 100 °C.
Materials Chemistry and Physics 2014 Volume 143(Issue 3) pp:1055-1060
Publication Date(Web):14 February 2014
DOI:10.1016/j.matchemphys.2013.11.004
•NiCl2 enhanced dehydrogenation of hydrazine bisborane (HBB) was reported.•By adding NiCl2, the desorption rate and the hydrogen purity were improved.•A possible explanation was proposed to understand NiCl2 enhanced desorption of HBB.NiCl2 and CoCl2 were adopted to enhance the dehydrogenation of hydrazine bisborane (HBB), respectively, of which NiCl2 showed better performance. By adding 2.0 mol. % NiCl2, the dehydrogenation property of HBB was significantly improved, for example, the impurity of NH3 during the dehydrogenation of HBB was totally suppressed with more than 13.0 wt. % of pure hydrogen evolved. By Kissinger method, the apparent activation energies of the first step for HBB and Ni-doped HBB were calculated to be 143.2 and 60.7 kJ mol−1, respectively. DSC result showed that the addition of NiCl2 did not change the enthalpy change of HBB dehydrogenation. Based on theoretical analysis and literature review, the improved dehydrogenation property of HBB was potentially ascribed to the solid state interaction of Ni2+ with the electronegative N in the NH2 group of HBB.
Co-reporter:Yingbin Tan, Qinfen Gu, Justin A. Kimpton, Qian Li, Xiaowei Chen, Liuzhang Ouyang, Min Zhu, Dalin Sun and Xuebin Yu
Journal of Materials Chemistry A 2013 vol. 1(Issue 35) pp:10155-10165
Publication Date(Web):10 Jun 2013
DOI:10.1039/C3TA11599B
A strategy for establishing Hδ+⋯−δH interactions by the combination of two kinds of H-enriched B–N based hydrides, ammine metal borohydrides (AMBs) and ammonia borane (AB), to achieve superior dehydrogenation properties is reported. Two novel combined complexes: Al(BH4)3·6NH3–4AB and Li2Al(BH4)5(NH3BH3)3·6NH3 were successfully synthesized. Structural analysis revealed that a partial NH3 unit transferred from Al(BH4)3·6NH3 to AB, resulting in the formation of two new phases of Al(BH4)3·5.4NH3 and NH3BH3·0.15NH3 in the Al(BH4)3·6NH3–4AB composite. In contrast, Li2Al(BH4)5(NH3BH3)3·6NH3 formed with a single-phase that was indexed to a cubic unit cell with a refined lattice parameter, a = 23.1220(3) Å. The structure of Li2Al(BH4)5(NH3BH3)3·6NH3 is composed of alternate Li+, [Al(NH3)6]3+ and AB layers stacked along the b-axis as a 3D framework. Compared to the unitary compound, the H-enriched complex system presented a mutual dehydrogenation improvement in terms of a considerable decrease in the dehydrogenation temperature and the preferable suppression of the simultaneous release of by-products; for example, over 11 wt% of hydrogen, with a purity of >98 mol%, can be released from both Al(BH4)3·6NH3–4AB and Li2Al(BH4)5(NH3BH3)3·6NH3 below 120 °C. The significantly improved dehydrogenation in the H-enriched complex system can be attributed to the initial interaction between the AB and an NH3 group (from the AMBs), which results in the balanced B–H and N–H units in the AMBs, thereby leading to a more activated and thorough Hδ+⋯−δH interaction in the composite. Moreover, an ammonia-liquification technique was employed to impregnate the complex system into a hypercrosslinked nano-porous polymer (PSDB) template, resulting in the average particle size of the Al(BH4)3·6NH3–4AB composite to be <5 nm, which enables it to release more than 10 wt% high-pure hydrogen (>99.8 mol%) below 110 °C. These advanced dehydrogenation properties affirm Al(BH4)3·6NH3–4AB and Li2Al(BH4)5(NH3BH3)3·6NH3 as strong candidates for potential hydrogen storage materials.
Co-reporter:Leigang Li, Qinfen Gu, Ziwei Tang, Xiaowei Chen, Yingbin Tan, Qian Li and Xuebin Yu
Journal of Materials Chemistry A 2013 vol. 1(Issue 39) pp:12263-12269
Publication Date(Web):07 Aug 2013
DOI:10.1039/C3TA11988B
Two new derivatives of ammonia borane (AB), 1,2/1,3-di-aminopropane borane (1,2/1,3-TMDAB), were prepared through the coordination reaction between 1,2/1,3-di-aminopropane and BH3–THF, which were then characterized by HR-XRD, FT-IR, 13C and 11B NMR. The crystal structure of 1,3-TMDAB was obtained with a combined technique of HR-XRD data and DFT calculations. 1,3-TMDAB crystallizes in the space group of P212121 (no. 19) with an orthorhombic crystal system and lattice constants of a = 12.6439(8) Å, b = 8.6289(3) Å, c = 7.2322(2) Å, and V = 789.05(3) Å3. Both samples, with a theoretical hydrogen content of 9.8 wt%, were shown to release pure H2 during thermal dehydrogenation, presenting great advantages over AB which releases large amounts of impurities (such as NH3, B2H6 or borazine). Moreover, 1,2/1,3-TMDAB did not foam and showed a faster dehydrogenation rate compared with AB. Our newly synthesized 1,2/1,3-TMDAB may serve as a superior alternative to AB for hydrogen storage and enrich the research field of B–N–H hydrogen storage materials.
Co-reporter:Xiaowei Chen, Feng Yuan, Qinfen Gu and Xuebin Yu
Journal of Materials Chemistry A 2013 vol. 1(Issue 38) pp:11705-11710
Publication Date(Web):31 Jul 2013
DOI:10.1039/C3TA11940H
The structural stability and hydrogen adsorption capacity of an alkali (Li, Na and K) and alkali earth (Mg and Ca) metal atom decorated covalent triazine-based framework (CTF-1) are studied using ab initio density functional calculations. The calculation results revealed that Li, Na, K and Ca atoms can be adsorbed on the CTF-1 with the formation of a uniform and stable coverage due to the charge transfer between the metal atoms and the CTF-1 substrate, thus avoiding the clustering problem that occurs for the decoration of metal atoms on other substrates. The metal decorated CTF-1 could adsorb up to 30 hydrogen molecules with an average binding energy of ∼0.16–0.26 eV/H2, corresponding to a gravimetric density of 12.3, 10.3 and 8.8 wt% for the CTF–Li6, CTF–Na6 and CTF–Ca6 complexes, respectively, thereby enabling the Li, Na and Ca decorated covalent triazine-based frameworks to be very promising materials for effective reversible hydrogen storage at near ambient conditions.
Co-reporter:Guanglin Xia, Li Li, Zaiping Guo, Qinfen Gu, Yanhui Guo, Xuebin Yu, Huakun Liu and Zongwen Liu
Journal of Materials Chemistry A 2013 vol. 1(Issue 2) pp:250-257
Publication Date(Web):27 Sep 2012
DOI:10.1039/C2TA00195K
In the present work, the decomposition behaviour of NaZn(BH4)3 nanoconfined in mesoporous SBA-15 has been investigated in detail and compared to bulk NaZn(BH4)3 that was ball milled with SBA-15, but not nanoconfined. The successful incorporation of nanoconfined NaZn(BH4)3 into mesopores of SBA-15 was confirmed by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, 11B nuclear magnetic resonance, nitrogen absorption/desorption isotherms, and Fourier transform infrared spectroscopy measurements. It is demonstrated that the dehydrogenation of the space-confined NaZn(BH4)3 is free of emission of boric by-products, and significantly improved hydrogen release kinetics is also achieved, with pure hydrogen release at temperatures ranging from 50 to 150 °C. By the Arrhenius method, the activation energy for the modified NaZn(BH4)3 was calculated to be only 38.9 kJ mol−1, a reduction of 5.3 kJ mol−1 compared to that of bulk NaZn(BH4)3. This work indicates that nanoconfinement within a mesoporous scaffold is a promising approach towards stabilizing unstable metal borohydrides to achieve hydrogen release with high purity.
Co-reporter:Guanglin Xia, Yingbin Tan, Xiaowei Chen, Zaiping Guo, Huakun Liu and Xuebin Yu
Journal of Materials Chemistry A 2013 vol. 1(Issue 5) pp:1810-1820
Publication Date(Web):30 Nov 2012
DOI:10.1039/C2TA00697A
Mixed-metal (Li, Al) amidoborane has been synthesized via mechanical ball milling of ammonia borane with lithium hexahydridoaluminate in different molar ratios. The reversible dehydrogenation properties of the thus-synthesized metallic amidoborane and its mixtures with ammonia borane in different ratios were systematically investigated in comparison with neat ammonia borane (AB). On the basis of thermogravimetric analysis and mass spectrometry results, the thus-synthesized mixed-metal amidoborane was shown to release around 10 wt% hydrogen below 200 °C, with an effective suppression of volatile side products. Furthermore, a synergistic effect between metallic amidoborane and ammonia borane has been identified, which leads to the release of 9 wt% hydrogen with high purity at 120 °C. Additionally, upon treatment with hydrazine in liquid ammonia, the regenerated products from the decomposed Li3AlH6–nAB (n = 4, 5, and 6) composites can release 3.5 wt% hydrogen with high purity, corresponding to an approximate 35%, 30%, and 26% regeneration yield for the post-milled Li3AlH6–nAB (n = 4, 5, and 6) composites, respectively.
Co-reporter:Zunxian Yang, Qing Meng, Zaiping Guo, Xuebin Yu, Tailiang Guo and Rong Zeng
Journal of Materials Chemistry A 2013 vol. 1(Issue 35) pp:10395-10402
Publication Date(Web):25 Jun 2013
DOI:10.1039/C3TA11751K
Highly uniform, relatively large area TiO2/SnO2/carbon hybrid nanofibers were synthesized by a simple method based on thermal pyrolysis and oxidation of an as-spun titanium–tin/polyacrylonitrile nanoweb composite in an argon atmosphere. This novel composite features the uniform dispersion and encapsulation of highly uniform nanoscale TiO2/SnO2 crystals in a porous carbon matrix. The high porosity of the nanofiber composite material, together with the conductive carbon matrix, enhanced the electrochemical performance of the TiO2/SnO2/carbon nanofiber electrode. The TiO2/SnO2/carbon nanofiber electrode displays a reversible capacity of 442.8 mA h g−1 for up to 100 cycles, and exhibits excellent rate capability. The results indicate that the composite could be a promising anode candidate for lithium ion batteries.
The crystal structure of an aluminum-based borohydride ammoniate – Al(BH4)3·6NH3 – is reported for the first time. The molecular structure of Al(BH4)3·6NH3 is resolved by high-resolution X-ray diffraction. The compound crystallized in the space group Pbcn (No. 60), with lattice parameters of a = 13.2824(5) Å, b = 15.2698(7) Å and c = 13.1848(6) Å. Structure analysis shows that this compound contains complex hexamminealuminum (III) [Al(NH3)6]3+ cations, which are surrounded by anions. The interatomic distances between the Hδ+s from the NH3 units and the Hδ−s from the BH4 units are in the range of 1.91–2.19 Å, suggesting the presence of significant Hδ+⋯−δH interactions. Mass spectrometry, thermogravimetry and temperature-programmed desorption studies of metal cation-modified aluminum-based borohydride ammoniates using the reactions of various metal borohydrides M(BH4)n (M = Na, Li, Ca, Mg) and chlorides MCln (M = Sc, Ni, Cu, Zn, Mg, Ca, Li) reveal that their dehydrogenation properties are strongly dependent on the polarizing power of the added metal cations. It is hypothesized that the added metal cations may activate the borohydride ion to such an extent that its Hδ− can easily react with the Hδ+ of the [Al(NH3)6]3+ cation, resulting in an enhanced interaction between the Hδ+ and Hδ−, thus enhancing their dehydrogenation kinetics. Subsequent deuterium isotope and X-ray measurements support the hypothesis that the Hδ+⋯−δH interactions play a role in the dehydrogenation of the metal borohydride ammoniates. Of the systems investigated, 0.5Mg(BH4)2/Li2Al(BH4)5·6NH3 is notable as it releases more than 10 wt.% high-purity H2 within 30 min below 120 °C. This ranks among the highest values currently reported for potential solid-state hydrogen storage materials. These findings provide a feasible and simple route for modifying B–N-based, lightweight materials for highly efficient dehydrogenation.
LiSc(BH4)4·4NH3 and V(BH4)3·3NH3, two novel metal borohydride ammoniates (MBAs), have been successfully synthesized via ball-milling the mixtures of MCl3·xNH3 (M = Sc, V and x = 3, 4) with LiBH4. Structure analysis reveals that LiSc(BH4)4·4NH3 crystallizes in an orthorhombic structure with lattice parameters of a = 7.4376(3) Å, b = 11.1538(5) Å and c = 14.5132(7) Å and space group of Pc21n, in which the base octahedral units are composed of central metal and an equivalent number of BH4 and NH3 units, distinct from other reported MBAs. Base units with the above constitution are also observed in the crystal structure of V(BH4)3·3NH3, which is identified as a cubic structure with lattice parameters of a = 10.78060(25) Å and space group of F23. These two compounds exhibit a favorable dehydrogenation capability, releasing 15.1 and 14.3 wt.% high-purity hydrogen, respectively, below 300 °C. Isothermal measurements reveal that, at a constant temperature of 110 °C, which meets the operation requirement of fuel cells, >8 and >10 wt.% pure hydrogen is released from the two compounds with favorable kinetics, respectively. Moreover, by reacting with N2H4 in liquid ammonia, the decomposed LiSc(BH4)4·4NH3 can be partly hydrogenated and can possibly establish a system that will undergo reversible dehydrogenation. These favorable properties point to potential on-board application. The dehydrogenation capacity, purity and temperature of the two systems can be adjusted, by tuning the ratios of the starting reagents LiBH4 and MCl3·xNH3, to achieve expected stoichiometric proportions of BH4 and NH3 units, which provides a facile and viable strategy for the synthesis of modified, mono-, di- or polymetal borohydride ammoniate systems and thus tunable hydrogen storage performances.
A uniformly distributed composite of 2LiBH4–LiAlH4 was successfully nanoconfined in mesoporous carbon scaffolds by using the solvent-mediated infiltration technique. The onset dehydrogenation temperatures of LiAlH4 and LiBH4 in the infiltrated 2LiBH4–LiAlH4 composite are decreased to ∼80 and ∼230 °C, respectively, and are 40 and 145 °C lower for their post-milled counterparts. Isothermal measurements reveal that ∼10 wt.% H2 could be released from the nanoconfined 2LiBH4–LiAlH4 composite at 300 °C within 300 min, while less than 4 wt.% H2 was released with respect to the post-milled mixture, even at 350 °C. Moreover, by taking advantage of both nanoconfinement and thermodynamic destabilization, the release of toxic diborane from LiBH4 was successfully suppressed. The dehydrogenation mechanism reveals that, under the structure-directing effects of carbon supports, the decomposition of the well-distributed 2LiBH4–LiAlH4 composite favors the formation of AlB2 instead of the thermodynamically stable Li2B12H12, which has been verified to play a crucial role in enhancing the hydrogenation of the 2LiBH4–LiAlH4 composite. In combination with the extra LiH supplied by the in situ decomposition of nanoconfined LiAlH4, the thus-tailored thermodynamics and kinetics of the 2LiBH4–LiAlH4 composite endow it with significantly advanced reversible hydrogen storage properties, with a stable reversibility without apparent degradation after seven dehydrogenation/rehydrogenation cycles.
Co-reporter:Xiaowei Chen, Yu-Jun Zhao and Xuebin Yu
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 3) pp:893-900
Publication Date(Web):19 Nov 2012
DOI:10.1039/C2CP43016A
First-principles calculations based on density functional theory were carried out to investigate the formation and migration of native defects in LiNH2BH3. The structural properties and formation energies of H, Li, N and B related defects in various charge states were examined. Our analysis showed that the dominant atomic H defects are positively and negatively charged H interstitial (IH+ and IH−). The Li related defects are dominated by positively charged Li interstitial (ILi+) and negatively charged Li vacancy (VLi−). For N related defects, the energetically favorable defects are positively and negatively charged NH2 interstitial (INH2+ and INH2−), while B related defect is dominated by neutral BH3 interstitial (IBH30). Further results indicated that the neutral H2 interstitial (IH2) has the lowest formation energy (0.31 eV), suggesting that the major defect in LiNH2BH3 is IH2. Investigation of migration processes of the defects showed that the migration barriers for V(B)H+ (positively charged H vacancy on a B–H site), IH+ and IH− are relatively high (0.50–0.68 eV), whereas moderate diffusion barriers are presented for V(N)H− (negatively charged H vacancy on a N–H site) and ILi+ (0.29 and 0.32 eV, respectively). The VLi− and IH2 defects can migrate with low energy barriers of 0.13 and 0.16 eV, respectively. With a low activation energy of 0.47 eV, IH2 is the major diffusive species in LiNH2BH3. Our calculation results further suggest that the creation of the V(N)H−, ILi+ and VLi− defects is the rate-limiting step for their transportation in LiNH2BH3.
The synthesis, crystal structure and dehydrogenation performances of two new H-enriched compounds, Mg(BH4)2(NH3BH3)2 and Mg(BH4)2·(NH3)2(NH3BH3), are reported. Due to the introduction of ammonia ligands, the Mg(BH4)2·(NH3)2(NH3BH3) exhibits dramatically improved dehydrogenation properties over its parent compound.
Several chemical hydrides, such as NaBH4, LiAlH4, AlH3 and B–N–H compounds, containing high hydrogen capacity (>10 wt%) have attracted increasing attention as promising hydrogen storage candidates recently. However, to realize a wide use of these hydrides in the future “hydrogen economy”, a serious challenge that we have to face is how to regenerate the spent fuels of these hydrides efficiently. In recent years, some potentially cost- and energy-efficient chemical methods to regenerate these hydrides from their spent fuels have been experimentally and theoretically demonstrated. These remarkable advances in regeneration techniques are considerably promoting the practical application of these materials as available hydrogen storage media. In this review, we highlight the details of chemical regeneration of these hydrides and briefly discuss the advances, challenges and feasible solutions towards each regeneration scheme in their hydrogen storage chemistry.
International Journal of Hydrogen Energy 2013 Volume 38(Issue 36) pp:16199-16207
Publication Date(Web):13 December 2013
DOI:10.1016/j.ijhydene.2013.09.123
•Mg(BH4)2·6NH3–nAB showed a mutual dehydrogenation improvement.•Introduction of ZnCl2 further improved dehydrogenation of Mg(BH4)2·6NH3–6AB.•Over 7 wt.% pure H2 was released from the composite at 95 °C within 10 min.A combined strategy via mixing Mg(BH4)2·6NH3 with ammonia borane (AB) is employed to improve the dehydrogenation properties of Mg(BH4)2·6NH3. The combined system shows a mutual dehydrogenation improvement in terms of dehydrogenation temperature and hydrogen purity compared to the individual components. A further improved hydrogen liberation from the Mg(BH4)2·6NH3–6AB is achieved with the assistance of ZnCl2, which plays a crucial role in stabilizing the NH3 groups and promoting the recombination of NHδ+⋯HBδ−. Specifically, the Mg(BH4)2·6NH3–6AB/ZnCl2 (with a mole ratio of 1:0.5) composite is shown to release over 7 wt.% high-pure hydrogen (>99 mol%) at 95 °C within 10 min, thereby making the combined system a promising candidate for solid hydrogen storage.
International Journal of Hydrogen Energy 2013 Volume 38(Issue 36) pp:16208-16214
Publication Date(Web):13 December 2013
DOI:10.1016/j.ijhydene.2013.09.154
•Cobalt-based ammine borohydrides were synthesized via a simple ball milling process.•5.2 wt.% pure hydrogen can be evolved within 45 min at 80 °C from CoCl3·3NH3/3LiBH4.•CoCl2·3NH3/2LiBH4 shows certain advantage over CoCl2/2LiBH4 as hydrogen storage material.Two new cobalt-based ammine borohydrides were prepared via ball milling of LiBH4 and CoCln·3NH3 (n = 3, 2) with molar ratios of 3:1 and 2:1, respectively. X-ray diffraction (XRD) results revealed the as-prepared composites having amorphous state. Thermogravimetric analysis-mass spectrometry (TG-MS) measurements showed that the two composites mainly release H2, concurrent with the evolution of a small amount of NH3. Further results showed that the excessive addition of LiBH4 can suppress the liberation of NH3, resulting in the release of H2 with a high purity (>99 mol.%). By combination with the temperature-programmed-desorption (TPD) results, the CoCl3·3NH3/4LiBH4 and CoCl2·3NH3/3LiBH4composites can release 7.3 wt.% (4.2 wt.% including LiCl) and 4.2 wt.% (2.0 wt.% including LiCl) pure hydrogen, respectively, in the temperature range of 25–300 °C. Isothermal dehydrogenation results reveal that CoCl3·3NH3/3LiBH4 shows favorable dehydrogenation rate at low temperatures, releasing about 5.2 wt.% (2.9 wt.% including LiCl) of hydrogen within 45 min at 80 °C.
Co-reporter:Jianfeng Mao, Zaiping Guo, Xuebin Yu, Huakun Liu
International Journal of Hydrogen Energy 2013 Volume 38(Issue 9) pp:3650-3660
Publication Date(Web):27 March 2013
DOI:10.1016/j.ijhydene.2012.12.106
It is well known that the dehydrogenation pathway of the LiBH4–MgH2 composite system is highly reliant on whether decomposition is performed under vacuum or a hydrogen back-pressure. In this work, the effects of hydrogen back-pressure and NbF5 addition on the dehydrogenation kinetics of the LiBH4–MgH2 system are studied under either vacuum or hydrogen back-pressure, as well as the subsequent rehydrogenation and cycling. For the pristine sample, faster desorption kinetics was obtained under vacuum, but the performance is compromised by slow absorption kinetics. In contrast, hydrogen back-pressure remarkably promotes the absorption kinetics and increases the reversible hydrogen storage capacity, but with the penalty of much slower desorption kinetics. These drawbacks were overcome after doping with NbF5, with which the dehydrogenation and rehydrogenation kinetics was significantly improved. In particular, the enhanced kinetics was observed to persist well, even after 9 cycles, in the case of the NbF5 doped sample under hydrogen back-pressure, as well as the suppression of forming Li2B12H12. Furthermore, the mechanism that is behind these effects of NbF5 additive on the reversible dehydrogenation reaction of the LiBH4–MgH2 system is discussed.Highlights► NbF5 as catalyst precursors. ► Catalyzing LiBH4–MgH2 with improved de/rehydrogenation kinetics and good cycling. ► Combining hydrogen back-pressure with NbF5 additive suppresses Li2B12H12 formation. ► Reduced Nb species probably act as active species.
International Journal of Hydrogen Energy 2013 Volume 38(Issue 22) pp:9236-9242
Publication Date(Web):26 July 2013
DOI:10.1016/j.ijhydene.2013.05.044
•Niobium-based ammine borohydride was synthesized via a ball-milling process.•11.2 wt.% pure hydrogen can be released from the as-prepared sample.•BH–HB and NH–HN homo-polar interactions contribute to the hydrogen evolution.In this paper, niobium-based ammine borohydride has been synthesized via a simple ball milling of NbCl5·5NH3 and MBH4 (M = Li, Na) with a molar ratio of 1:5. Thermogravimetric analysis–mass spectrometry (TGA–MS) and temperature-programmed-desorption (TPD) results revealed that the dehydrogenation of NbCl5·5NH3/5LiBH4 and NbCl5·5NH3/5NaBH4 mixtures showed a two-step decomposition process with a total of 8.1 wt.% and 11.2 wt.% pure hydrogen evolution upon heating to 250 °C, respectively. Isothermal TPD results showed that over 6 wt.% and 10.4 wt.% pure hydrogen were liberated from NbCl5·5NH3/5NaBH4 within 60 min at 150 °C and 220 °C, respectively. Fourier transform infrared spectroscopy (FTIR) and isotope tagging measurements demonstrated that the dehydrogenation mechanism of niobium-based ammine borohydride is not only based on the combination reaction of BH and NH groups, but the BH⋯HB and NH⋯HN homo-polar interactions also contribute to the H2 formation.
International Journal of Hydrogen Energy 2013 Volume 38(Issue 13) pp:5322-5329
Publication Date(Web):1 May 2013
DOI:10.1016/j.ijhydene.2013.02.039
The penta-ammine vanadium (III) borohydride, i.e. V(BH4)3·5NH3, was successfully synthesized via ball-milling of VCl3·5NH3 and LiBH4 in a molar ratio of 1:3. This compound was shown to release 11.5 wt% hydrogen with a H2-purity of 85 mol% by 350 °C. To improve the dehydrogenation purity of V(BH4)3·5NH3, Mg(BH4)2 with various molar ratios was mixed with V(BH4)3·5NH3 to synthesize expected ammine metal-mixed borohydrides, among which the formed VMg(BH4)5·5NH3 was indexed to be a monoclinic unit cell with lattice parameters of a = 19.611 Å, b = 14.468 Å, c = 6.261 Å, β = 93.678° and V = 1772.75 Å3. Dehydrogenation results revealed that the Mg(BH4)2 modified V(BH4)3·5NH3 system presents significantly enhanced dehydrogenation purity. For example, in the case of V(BH4)3·5NH3/2Mg(BH4)2 sample, 12.4 wt% pure hydrogen can be released upon heating to 300 °C. Further investigation on the dehydrogenation mechanism of the VMg(BH4)5·5NH3 system by isotope tagging revealed that the interactions of homo-polar BH units also participated throughout the dehydrogenation process (onset at 75 °C) as complementary to the prime combination of BH···HN.Highlights► V(BH4)3·5NH3 was synthesized via the reaction of VCl3·5NH3 with LiBH4. ► VMg(BH4)5·5NH3 was indexed to be a monoclinic unit cell. ► For V(BH4)3·5NH3/2Mg(BH4)2, 12.4 wt% pure H2 can be released.
Co-reporter:Qinfen Gu, Liang Gao, Yanhui Guo, Yingbin Tan, Ziwei Tang, Kia S. Wallwork, Feiwu Zhang and Xuebin Yu
Energy & Environmental Science 2012 vol. 5(Issue 6) pp:7590-7600
Publication Date(Web):20 Apr 2012
DOI:10.1039/C2EE02485C
Zn(BH4)2·2NH3, a new ammine metal borohydride, has been synthesized via simply ball-milling a mixture of ZnCl2·2NH3/2LiBH4. Structure analysis shows that the subsequent complex has a monoclinic structure with unit-cell parameters of a = 6.392(4) Å, b = 8.417(6) Å, c = 6.388(4) Å and β = 92.407(4)° and space group P21, in which Zn atoms coordinate with two BH4 groups and two NH3 groups. The interatomic distances reported herein show that Zn–H bonding in Zn(BH4)2·2NH3 is shorter than Ca–H bonds in Ca(BH4)2·2NH3 and Mg–H in Mg(BH4)2·2NH3. This reduced bond contact leads to an increase in the ionic character of H. This study is able to show a good correlation between the reduced M–H distance and enhanced dehydrogenation behavior of the hydride material. Dehydrogenation results showed that Zn(BH4)2·2NH3/LiCl is able to release 5.36 wt% hydrogen (corresponding to 8.9 wt% for pure Zn(BH4)2·2NH3) below 115 °C within 15 min without concomitant release of undesirable gases such as ammonia and/or boranes, thereby demonstrating the potential of Zn(BH4)2·2NH3 to be used as a solid hydrogen storage material.
Journal of the American Chemical Society 2012 Volume 134(Issue 12) pp:5464-5467
Publication Date(Web):March 14, 2012
DOI:10.1021/ja300003t
The recyclable dehydrogenation of ammonia borane (AB) is achievable within a graphene oxide (GO)-based hybrid nanostructure, in which a combined modification strategy of acid activation and nanoconfinement by GO allows AB to release more than 2 equiv of pure H2 at temperatures below 100 °C. This process yields polyborazylene (PB) as a single product and, thus, promotes the chemical regeneration of AB via reaction of PB with hydrazine in liquid ammonia.
Chemistry of Materials 2012 Volume 24(Issue 17) pp:3370
Publication Date(Web):August 2, 2012
DOI:10.1021/cm301387d
Ammine metal borohydrides (AMBs), with high hydrogen contents and favorable dehydrogenation properties, are receiving intensive research efforts for their potential as hydrogen storage materials. In this work, we report the successful synthesis of three ammine titanium borohydrides (denoted as ATBs), Ti(BH4)3·5NH3, Li2Ti(BH4)5·5NH3, and Ti(BH4)3·3NH3 via metathesis reaction of metal chloride ammoniates (TiCl3·5NH3 and TiCl3·3NH3) and lithium borohydride. These ATBs present favorable stability, owing to the coordination with NH3 groups, compared to the unstable Ti(BH4)3 at room temperature. Dehydrogenation results revealed that Ti(BH4)3·5NH3, which theoretically contains 15.1 wt % hydrogen, is able to release ∼13.4 wt % H2 plus a small amount of ammonia. This occurred via a single-stage decomposition process with a dehydrogenation peak at 130 °C upon heating to 200 °C. For Li2Ti(BH4)5·5NH3, a three-step decomposition process with a total of 15.8 wt % pure hydrogen evolution peaked at 105, 120, and 215 °C was observed until 300 °C. In the case of Ti(BH4)3·3NH3, a release of 14 wt % pure hydrogen via a two-step decomposition process with peaks at 109 and 152 °C can be achieved in the temperature range of 60–300 °C. Isothermal TPD results showed that over 9 wt % pure hydrogen was liberated from Ti(BH4)3·3NH3 and Li2Ti(BH4)5·5NH3 within 400 min at 100 °C. Preliminary research on the reversibility of this process showed that dehydrogenated ATBs could be partly recharged by reacting with N2H4 in liquid ammonia. These aforementioned preeminent dehydrogenation performances make ATBs very promising candidates as solid hydrogen storage materials. Finally, analysis of the decomposition mechanism demonstrated that the hydrogen emission from ATBs is based on the combination reaction of B–H and N–H groups as in other reported AMBs.Keywords: ammine metal borohydrides; ammine titanium borohydrides; hydrogen storage; metathesis reaction;
Co-reporter:Ziwei Tang, Yingbin Tan, Qinfen Gu and Xuebin Yu
Journal of Materials Chemistry A 2012 vol. 22(Issue 12) pp:5312-5318
Publication Date(Web):05 Jan 2012
DOI:10.1039/C2JM14990G
The crystal structure of a promising hydrogen storage material, calcium borohydride monoammoniate (Ca(BH4)2·NH3), is reported. Structural analysis revealed that this compound crystallizes in an orthorhombic structure (space group Pna21) with unit-cell parameters of a = 8.4270 Å, b = 12.0103 Å, c = 5.6922 Å and V = 576.1121 Å3, in which the Ca atom centrally resides in a slightly distorted octahedral environment furnished by five B atoms from BH4 units and one N atom from the NH3 unit. As Ca(BH4)2·NH3 tends to release ammonia rather than hydrogen when heated in argon, a novel aided-cation strategy via combining this compound with LiBH4 was employed to advance its dehydrogenation. It shows that the interaction of the two potential hydrogen storage substances upon heating, based on a promoted recombination reaction of BH and NH groups, enables a significant mutual dehydrogenation improvement beyond them alone, resulting in more than 12 wt% high-pure H2 (>99%) released below 250 °C. The synergetic effect of associating the dihydrogen reaction with mutually aided-metal cations on optimizing the dehydrogenation of this kind of composites may serve as an alternative strategy for developing and expanding the future B–N–H systems with superior and tuneable dehydrogenation properties.
Co-reporter:Ziwei Tang, Shaofeng Li, Weina Yang and Xuebin Yu
Journal of Materials Chemistry A 2012 vol. 22(Issue 25) pp:12752-12758
Publication Date(Web):01 May 2012
DOI:10.1039/C2JM30382E
A novel strategy of adopting the reversible swelling effect of a promising scaffold—hypercrosslinked porous poly(styrene-co-divinylbenzene) resin (PSDB) to nanoconfine hydrogen storage materials is reported, in which nanoconfined ammonia–borane (AB) is endowed with high loading ratio and significantly improved hydrogen storage capabilities. To verify the importance of swelling behavior displayed by this polymeric scaffold in dehydrogenation, an ammonia-dissolving route (PSDB–AB (NH3)) that does not involve swelling, was performed to enable direct comparison with the methanol-dissolving route (PSDB–AB (CH3OH)). Moreover, solid-state 11B NMR measurements were employed to illustrate the different reaction mechanisms in these two PSDB-confined AB samples, where decomposition involving both the diammoniate of diborane (DADB) and linear dimer are observed for PSDB–AB (NH3) but only the latter route is seen for PSDB–AB (CH3OH), deeply demonstrating the difference of dehydrogenation properties in these two samples. Our findings establish a prospective approach via utilizing this class of polymers for promoting the design and construction of advanced energy materials with high performances.
Co-reporter:Guanglin Xia, Qinfen Gu, Yanhui Guo and Xuebin Yu
Journal of Materials Chemistry A 2012 vol. 22(Issue 15) pp:7300-7307
Publication Date(Web):06 Mar 2012
DOI:10.1039/C2JM16370E
The synthesis and dehydrogenation performance of purified NaZn(BH4)3 with a new phase and its novel ammine metal borohydride, NaZn(BH4)3·2NH3, were first reported. Structure analysis shows that NaZn(BH4)3·2NH3 crystallizes in an orthorhombic structure with lattice parameters of a = 7.2965(2) Å, b = 10.1444(2) Å and c = 12.9714(3) Å and space group P21nb, in which the Zn atoms are located in a tetrahedral coordination environment with two NH3 molecules and two BH4− units, presenting a novel 3D framework comprised of isolated BH4−1 units and [NaZn(BH4)2(NH3)2]+ complexes. Dehydrogenation results showed that the ZnCl2 assisted NaZn(BH4)3·2NH3 is able to release 7.9 wt% hydrogen at 110 °C without the concomitant release of undesirable gases such as ammonia and/or boranes, thereby demonstrating the potential of the ammoniated Zn-based borohydrides to be used as solid hydrogen storage materials.
Co-reporter:Shaofeng Li, Ziwei Tang, Qiaolong Gong, Xuebin Yu, Paul R. Beaumont and Craig M. Jensen
Journal of Materials Chemistry A 2012 vol. 22(Issue 39) pp:21017-21023
Publication Date(Web):21 Aug 2012
DOI:10.1039/C2JM34766K
Novel borohydrides of para- and meta-bis-(ammonium)-benzene (m/p-BABB), possessing theoretical hydrogen storage capacities of 10.1 wt%, have been synthesized upon metathesis of p/m-benzenediamine dihydrochloride (p/m-BDADC) and lithium borohydride through simple ball-milling. It was found that the dehydrogenation of the BABBs proceeds in the temperature range of 50–200 °C via a multistep mechanism similar to that of NH3BH3 and [NH4]+[BH4]−, releasing 8.35 and 6.52 wt% hydrogen from p- and m-BABB, respectively. Solid state 11B MAS NMR studies indicate that the dehydrogenation process of p-BABB and m-BABB follows a pathway similar to that of [NH4]+[BH4]−via [BH2(NH3)2]+[BH4]− (DADB). The residues obtained after releasing ∼6 equiv. H2 are mainly N,N′-phenyl substituted polyborazylenes. The dehydrogenated products can be converted back to N,N′-phenyl substituted ammonia-boranes by treatment with hydrazine sulfate [(N2H4)2·H2SO4] in liquid ammonia (NH3) for one week at 45 °C, demonstrating the potential of this class of material for regenerable chemical hydrogen storage.
Co-reporter:Zunxian Yang, Guodong Du, Qing Meng, Zaiping Guo, Xuebin Yu, Zhixin Chen, Tailiang Guo and Rong Zeng
Journal of Materials Chemistry A 2012 vol. 22(Issue 12) pp:5848-5854
Publication Date(Web):15 Feb 2012
DOI:10.1039/C2JM14852H
Very large area, uniform TiO2@carbon composite nanofibers were easily prepared by thermal pyrolysis and oxidization of electrospun titanium(IV) isopropoxide/polyacrylonitrile (PAN) nanofibers in argon. The composite nanostructures exhibit the unique feature of having TiO2 nanocrystals encapsulated inside a porous carbon matrix. The unique orderly-bonded nanostructure, porous characteristics, and highly conductive carbon matrix favour excellent electrochemical performance of the TiO2@carbon nanofiber electrode. The TiO2@carbon hybrid nanofibers exhibited highly reversible capacity of 206 mAh g−1 up to 100 cycles at current density of 30 mA g−1 and excellent cycling stability, indicating that the composite is a promising anode candidate for Li-ion batteries.
Journal of Materials Chemistry A 2012 vol. 22(Issue 3) pp:1061-1068
Publication Date(Web):15 Nov 2011
DOI:10.1039/C1JM13002A
The ammine complex of yttrium borohydride Y(BH4)3·4NH3, which contains a theoretical hydrogen capacity of 11.9 wt.%, has been successfully synthesized via a simple ball milling of YCl3·4NH3 and LiBH4. The structure of Y(BH4)3·4NH3, determined by high resolution powder X-ray diffraction, crystallizes in the orthorhombic space group Pc21n with lattice parameters a = 7.1151(1) Å, b = 11.4192(2) Å, c = 12.2710(2) Å and V = 997.02(2) Å3, in which the dihydrogen bonds with distances in the range of 2.043 to 2.349 Å occurred between the NH3 and BH4− units contribute to the hydrogen liberation via the combination reaction of N–H⋯H–B. Thermal gravimetric analysis combined with mass spectrometer results revealed that the decomposition of Y(BH4)3·4NH3 consists of three steps with peaks at 86 °C, 179 °C and 279 °C, respectively, in which the first and second steps mainly release hydrogen accompanied by a fair amount of ammonia emission, while the third one accounts for a pure hydrogen release. Isothermal dehydrogenation results revealed that over 8.7 wt.% hydrogen was released for Y(BH4)3·4NH3 at 200 °C, which are improved significantly in terms of both capacity and kinetics comparing to Y(BH4)3, in which the hydrogen capacity is only 3.2 wt.% at the same temperature. The favorable dehydrogenation properties presented by the Y(BH4)3·4NH3, i.e., lower dehydrogenation temperature and higher nominal hydrogen contents than that of Y(BH4)3, enable it to be a promising candidate for hydrogen storage. In addition, in situ high resolution X-ray diffraction, differential scanning calorimetry, solid-state 11B nuclear magnetic resonance and Fourier transform infrared spectroscopy measurements were employed to understand the dehydrogenation pathway of Y(BH4)3·4NH3.
Co-reporter:Yanhui Guo, Yixiao Jiang, Guanglin Xia and Xuebin Yu
Chemical Communications 2012 vol. 48(Issue 37) pp:4408-4410
Publication Date(Web):29 Feb 2012
DOI:10.1039/C2CC30751K
Ammine aluminium borohydride system is found to release >12 wt% pure H2 below 120 °C via a combined strategy of changing the coordination number and adopting mixed cations.
Co-reporter:Ziwei Tang, Yingbin Tan, Xiaowei Chen and Xuebin Yu
Chemical Communications 2012 vol. 48(Issue 74) pp:9296-9298
Publication Date(Web):25 Jul 2012
DOI:10.1039/C2CC34932A
Regenerable hydrogen storage of lithium amidoborane is firstly achieved through the routes of direct thermal dehydrogenation and subsequent chemical hydrogenation of its dehydrogenated products by treatment with hydrazine in liquid ammonia.
International Journal of Hydrogen Energy 2012 Volume 37(Issue 23) pp:18101-18107
Publication Date(Web):December 2012
DOI:10.1016/j.ijhydene.2012.09.069
The significantly enhanced dehydrogenation performance of binary complex system, NH3BH3/LiBH4·NH3, were achieved through a chemical modification of LiH to form ternary composites of x (LiH–NH3BH3)/LiBH4·NH3. Among the studied composites, 3LiH–3NH3BH3/LiBH4·NH3 released ca. 10 wt. % high-pure hydrogen (>99.9 mol%) below 100 °C with fast kinetics, while less than 8 wt. % hydrogen, accompanied with a fair number of volatile byproducts, were released from 3NH3BH3/LiBH4·NH3 at the same conditions. Further investigations revealed that the hydrogen emission from x (LiH–NH3BH3)/LiBH4·NH3 composites is based on the combination mechanism of Hδ+ and Hδ− through the interaction between LiH–NH3BH3 and NH3 group in LiBH4·NH3, in which the controllable protic hydrogen source from the stabilized NH3 group played a crucial role in providing optimal stoichiometric ratio of Hδ+ and Hδ−, and thus leading to the significant improvement of dehydrogenation capacity and purity.Highlights► LiH was introduced to enhance the dehydrogenation of the NH3BH3/LiBH4·NH3 composites. ► The 3LiH–3AB/3LiBH4·NH3 composite can release 10 wt. % pure hydrogen below 100 °C ► The hydrogen release in x (LiH–AB)/LiBH4·NH3 started with the formation of LiAB.
International Journal of Hydrogen Energy 2012 Volume 37(Issue 7) pp:5817-5824
Publication Date(Web):April 2012
DOI:10.1016/j.ijhydene.2011.12.162
Enhanced dehydrogenation properties for ammine lithium borohydride (LiBH4·NH3) melt-infiltrated into Al2O3 nanoscaffolds are reported. X-ray diffraction measurements verified the formation of intermediate phase of amorphous state during heating the composites at 65 °C. Subsequently, it was revealed by combination of gravimetric and volumetric measurements that a hydrogen desorption capacity of 12.8 wt.%, accounting for 91 mol% of the total amount of the released gas at 230 °C, was achieved for the LiBH4·NH3/Al2O3 composite with a mass ratio of 1:4, while in the pristine LiBH4·NH3 merely trace amount of H2 was detected at this temperature. Moreover, Fourier transform infrared spectra and 11B nuclear magnetic resonance spectra were combined to clarify the facilitated recombination of NH3 groups and BH4−1 anions in the composites. As a consequence, the mechanisms for the promoted dehydrogenation in the composites were reasonably deduced as twofold, firstly, the nanosize effects of the loaded LiBH4·NH3 on the dehydrogenation properties in the presence of the oxide nanoscaffolds, which serve as the highly dispersing support for the loaded materials, and assist the formation of the amorphous phase during heating; secondly, the impact of Al2O3 nanoscaffolds on the dehydrogenation of the loaded materials, via promotion of the recombination between BH and NH groups.Highlights► Nanostructured LiBH4·NH3/Al2O3 composites were prepared via a melting technique. ► Onset dehydrogenation occurs below 100 °C with the formation of B–N bond. ► A prominent dehydrogenation appears at 230 °C with a hydrogen capacity of 12.8 wt.%.
International Journal of Hydrogen Energy 2012 Volume 37(Issue 4) pp:3328-3337
Publication Date(Web):February 2012
DOI:10.1016/j.ijhydene.2011.11.036
Successful synthesis of LiBH4·NH3 confined in nanoporous silicon dioxide (LiBH4·NH3@SiO2) was achieved via a new “ammonia-deliquescence” method, which avoids the involvement of any solvents during the process of synthesis. Compared to the pure LiBH4·NH3, the confined LiBH4·NH3@SiO2 exhibited significantly improved dehydrogenation properties, which not only suppressed the emission of NH3, but also decreased the onset dehydrogenation temperature to 60 °C, thus leading to an enhanced conversion of NH3 to H2. In the temperature range of 60–300 °C, the mole ratio of H2 release for the confined LiBH4·NH3@SiO2 is 85 mol % of the total gas evolved, compared to 2.66 mol % for the pristine LiBH4·NH3. Isothermal dehydrogenation results showed that the LiBH4·NH3@SiO2 is able to release about 1.26, 2.09, and 2.35 equiv. of hydrogen, at 150 °C, 200 °C, and 250 °C, respectively. From analysis of the Fourier transform infrared, Raman, and nuclear magnetic resonance spectra of the confined LiBH4·NH3@SiO2 sample heated to various temperatures, as well as its dehydrogenation product under NH3 atmosphere, it is proposed that the improved dehydrogenation of LiBH4·NH3@SiO2 is mainly attributable to two crucial factors resulting from the nanoconfinement: (1) stabilization of the NH3 in the nanopores of SiO2, and (2) enhanced combination of LiBH4 and NH3 groups, leading to fast dehydrogenation at low temperature.Highlights► Successful synthesis of LiBH4·NH3 confined in nanoporous silicon dioxide. ► Confined LiBH4·NH3 exhibited significantly improved dehydrogenation properties in contrast to the bulk one. ► Nanoconfinement stabilized the NH3 in the nanopores and enhanced combination of LiBH4 and NH3 groups.
Co-reporter:S. F. Li ; Z. W. Tang ; Y. B. Tan ;X. B. Yu
The Journal of Physical Chemistry C 2012 Volume 116(Issue 1) pp:1544-1549
Publication Date(Web):December 14, 2011
DOI:10.1021/jp209234f
A new polymer hydrogen storage composite, polyacrylamide blending with ammonia borane (AB@PAM), was prepared through a simple sol-mixing method. The dehydrogenation kinetics and the possible H2-release pathway of the polymeric composites were investigated. Isothermal gas release and thermogravimetry/mass spectroscopy results demonstrated that the dehydrogenation properties of the AB@PAM have been promoted significantly in contrast to pure ammonia borane (AB), justified by its low onset H2-release temperature of 75 °C without induction period and complete depression of the emission of the boracic impurities. To determine the possible H2-release pathway, X-ray diffraction, Fourier transform infrared, and nuclear magnetic resonance measurements were carried out. It was demonstrated that the enhanced kinetics may owe to the refinement of crystal particles and disruption of the dihydrogen-bonding network of AB after blending, while the entire suppress of boracic impurities and the evolution of ammonia may be due to the interaction between O in the carbonyl groups (C═O) of PAM and B in the AB molecules, which weakens the B–N bonds to release NH3 and subsequently forms B–O bonds to inhibit the emission of boracic impurities. Finally, metal chlorides (CaCl2, MgCl2, and ZnCl2) were introduced to the AB@PAM, which leads to a significant depression of NH3 evolution, thereby enabling the dehydrogenation of the polymeric composite to occur at low temperature with enhanced hydrogen purity.
The Journal of Physical Chemistry C 2012 Volume 116(Issue 40) pp:21162-21168
Publication Date(Web):September 17, 2012
DOI:10.1021/jp302866w
As Ca(BH4)2·nNH3 (n = 1, 2, and 4) tends to release ammonia rather than hydrogen when heated in argon, an aided-cation strategy via combining these compounds with Mg(BH4)2 is employed to advance their dehydrogenation. It shows that the interaction between the two hydrogen storage systems, based on a promoted recombination reaction of BH and NH groups, enables a significant mutual dehydrogenation improvement beyond them alone. Dehydrogenation results show that the Ca(BH4)2·4NH3/Mg(BH4)2 composite starts to release hydrogen at around 62 °C and presents a hydrogen desorption capacity of >9 wt % below 300 °C with a H-purity of 92.3 wt %. Furthermore, in the cases of Ca(BH4)2·4NH3/2Mg(BH4)2, Ca(BH4)2·2NH3/Mg(BH4)2, and Ca(BH4)2·NH3/Mg(BH4)2, fairly pure hydrogen (>99 wt %) is released upon heating from RT to 500 °C. Further investigation via introduction of isotope deuterium in the combined system reveals that the dehydrogenation reactions are mainly mediated by the combination of Hδ+···Hδ- interactions, whereas Hδ-···Hδ- interactions also contribute in a complementary way.
Chemistry - A European Journal 2012 Volume 18( Issue 22) pp:6825-6834
Publication Date(Web):
DOI:10.1002/chem.201102651
Abstract
A new ammine dual-cation borohydride, LiMg(BH4)3(NH3)2, has been successfully synthesized simply by ball-milling of Mg(BH4)2 and LiBH4⋅NH3. Structure analysis of the synthesized LiMg(BH4)3(NH3)2 revealed that it crystallized in the space group P63 (no. 173) with lattice parameters of a=b=8.0002(1) Å, c=8.4276(1) Å, α=β=90°, and γ=120° at 50 °C. A three-dimensional architecture is built up through corner-connecting BH4 units. Strong NH⋅⋅⋅HB dihydrogen bonds exist between the NH3 and BH4 units, enabling LiMg(BH4)3(NH3)2 to undergo dehydrogenation at a much lower temperature. Dehydrogenation studies have revealed that the LiMg(BH4)3(NH3)2/LiBH4 composite is able to release over 8 wt % hydrogen below 200 °C, which is comparable to that released by Mg(BH4)3(NH3)2. More importantly, it was found that release of the byproduct NH3 in this system can be completely suppressed by adjusting the ratio of Mg(BH4)2 and LiBH4⋅NH3. This chemical control route highlights a potential method for modifying the dehydrogenation properties of other ammine borohydride systems.
The Journal of Physical Chemistry C 2012 Volume 116(Issue 27) pp:14218-14223
Publication Date(Web):June 13, 2012
DOI:10.1021/jp3032989
Metal-catalyzed hydrolysis and methanolysis of guanidinium borohydride (C(NH2)3BH4 or GBH) for hydrogen generation are reported. GBH is comparatively stable in water with only 0.3 equiv of H2 liberated in 24 h at 25 °C while it reacts vigorously with methanol, releasing more than 3.2 equiv of H2 within only 17 min. Even at 0 °C, there was still nearly 2.0 equiv of H2 released after 2 h, but no H2 liberation was observed for hydrolysis under the same conditions. Various metal chlorides were adopted to enhance the reaction kinetics of the hydrolysis and methanolysis, of which CoCl2 exhibits the highest activity in both cases. With the addition of 2.0 mol % CoCl2 at 25 °C, the methanolysis of GBH could generate 4 equiv of H2 within 10 min with a maximum hydrogen generation rate of 9961.5 mL·min–1·g–1 while only 1.8 equiv of H2 was obtained under the same conditions at a maximum hydrogen generation rate of 692.3 mL·min–1·g–1 for hydrolysis. Compared with hydrolysis, methanolysis of GBH possesses much faster reaction kinetics, rendering it an advantage for hydrogen generation, especially at subzero areas. It was proposed that the faster reaction kinetics of methanolysis of BH4– containing compounds is ascribed to the more electron donating methoxy group than that of hydroxyl group. Moreover, a comparison between hydrolysis and methanolysis of GBH indicates that the loss of the first H from BH4– controls the hydrolysis kinetics instead of the cleavage of the O–H bond.
The Journal of Physical Chemistry C 2012 Volume 116(Issue 22) pp:11900-11906
Publication Date(Web):May 15, 2012
DOI:10.1021/jp301986k
The electronic structure and initial dehydrogenation mechanism of M(BH4)2·2NH3 (M = Mg, Ca, and Zn) have been systematically studied using first-principles calculations. A detailed study of the electronic structure reveals that the metal cations in M(BH4)2·2NH3 play a crucial role in both suppressing ammonia emission and destabilizing the N–H/B–H bonds. The calculation results of hydrogen removal energies are in agreement with the tendency of dehydrogenation temperatures of these ammoniates, i.e., Zn(BH4)2·2NH3 < Mg(BH4)2·2NH3 < Ca(BH4)2·2NH3. The initial dehydrogenation of M(BH4)2·2NH3 is achieved by the dissociation of (N)Hδ+ from NH3 and (B)Hδ− atoms from BH4 groups, resulting in the formation of N–B dative bonds and the reduction of the neighboring (N)Hδ+···(B)Hδ− dihydrogen bonds, which accelerate the subsequent dehydrogenation.
Journal of the American Chemical Society 2011 Volume 133(Issue 13) pp:4690-4693
Publication Date(Web):March 10, 2011
DOI:10.1021/ja1105893
The strategy of using double-cations to tune the temperature and purity of dehydrogenation of ammine borohydrides is reported. The first double-cation ammine borohydride, Li2Al(BH4)5·6NH3, which forms a novel structure with ordered arrangement of Al(NH3)63+ ammine complexes and Li2(BH4)53− complex anions, is found to release over 10.0 wt % hydrogen below 120 °C with favorable kinetics and high H-purity (>99%).
Co-reporter:Zunxian Yang, Guodong Du, Zaiping Guo, Xuebin Yu, Zhixin Chen, Tailiang Guo and Huakun Liu
Journal of Materials Chemistry A 2011 vol. 21(Issue 24) pp:8591-8596
Publication Date(Web):09 May 2011
DOI:10.1039/C0JM03873C
Novel TiO2(B)@carbon composite nanowires were simply prepared by a two-step hydrothermal process with subsequent heat treatment in argon. The nanostructures exhibit the unique feature of having TiO2(B) encapsulated inside and an amorphous carbon layer coating the outside. The unique core/shell structure and chemical composition is likely to lead to perfect performance in many applications. In this paper, the results of Li-ion battery testing are presented to demonstrate the superior cyclic performance and rate capability of the TiO2(B)@carbon nanowires. The composite nanowires exhibit a high reversible capacity of 560 mAh g−1 after 100 cycles at the current density of 30 mA g−1, and excellent cycling stability and rate capability (200 mAh g−1 when cycled at the current density of 750 mA g−1), indicating that the composite is a promising anode candidate for Li-ion batteries.
Journal of Materials Chemistry A 2011 vol. 21(Issue 20) pp:7138-7144
Publication Date(Web):04 Apr 2011
DOI:10.1039/C0JM04485G
A novel combined hydrogen storage system LiBH4/[C(NH2)3]+[BH4]− (GBH) complexes were reported. By a short time ball milling of LiBH4 and guanidinium chloride, a series of new LiBH4/GBH complexes were produced. It was found that the two potential hydrogen storage materials exhibited a mutual dehydrogenation improvement, releasing >10.0 wt.% of fairly pure H2 from LiBH4/GBH below 250 °C. Further investigations revealed that balancing the protic and hydridic hydrogens, and the complexation between LiBH4 and GBH, are two important roles in the improvement of the dehydrogenation of this system, which may serve as an alternative strategy for developing a new metal borohydride/B–N–H system with favourable dehydrogenation.
Co-reporter:Ziwei Tang, Shaofeng Li, Zunxian Yang and Xuebin Yu
Journal of Materials Chemistry A 2011 vol. 21(Issue 38) pp:14616-14621
Publication Date(Web):15 Aug 2011
DOI:10.1039/C1JM12190A
An effective strategy of utilizing electrospinning techniques to fabricate MgCl2 catalyzed ammonia borane (AB) nanofibers with a tunable fiber diameter is reported. The synergistic effect obtained by combining nanofibers and metallic catalyst plays a crucial role in the decomposition of MgCl2-doped AB nanofibers, which leads to significant improvements in dehydrogenation kinetics and complete suppression of unwanted byproducts. The results of dehydrogenation show that MgCl2-doped AB nanofibers were able to release over 10.0 wt % pure H2 below 100 °C with favorable kinetics, a significant advance over releases from bulk AB. Furthermore, the dehydrogenation of MgCl2-doped AB nanofibers gives a weak exothermic reaction, −3.84 kJ mol−1 H2, which is dramatically lower than that of neat AB (−21 kJ mol−1 H2), which suggests that the electrospun sample is potentially more feasible to reverse. The findings in this paper provide general guidelines and inspiration for the design and synthesis of novel nano-fibrous materials with controllable dimensions for hydrogen storage applications.
Co-reporter:Yingbin Tan, Yanhui Guo, Shaofeng Li, Weiwei Sun, Yihan Zhu, Qian Li and Xuebin Yu
Journal of Materials Chemistry A 2011 vol. 21(Issue 38) pp:14509-14515
Publication Date(Web):11 Aug 2011
DOI:10.1039/C1JM11158B
A novel eutectic hydrogen storage system, LiBH4·NH3–nNH3BH3, which exists in a liquid state at room temperature, was synthesized through a simple mixing of LiBH4·NH3 and NH3BH3 (AB). In the temperature range of 90–110 °C, the eutectic system showed significantly improved dehydrogenation properties compared to the neat AB and LiBH4·NH3 alone. For example, in the case of the LiBH4·NH3/AB with a mole ratio of 1:3, over 8 wt.% hydrogen could be released at 90 °C within 4 h, while only 5 wt.% hydrogen released from the neat AB at the same conditions. Through a series of experiments it has been demonstrated that the hydrogen release of the new system is resulted from an interaction of AB and the NH3 group in the LiBH4·NH3, in which LiBH4 works as a carrier of ammonia and plays a crucial role in promoting the interaction between the NH3 group and AB. The enhanced dehydrogenation of LiBH4·NH3/AB may result from the polar liquid state reaction environments and the initially promoted formation of the diammoniate of diborane, which will facilitate the B–H⋯H–N interaction between LiBH4·NH3 and AB. Kinetics analysis revealed that the rate-controlling steps of the dehydrogenation process are three-dimensional diffusion of hydrogen at temperatures ranging from 90 to 110 °C.
This paper reports for the first time that under ammonia atmosphere, ammonia borane (AB) reversibly absorbs up to at least 6 equiv of NH3, forming liquid AB(NH3)n (n = 1−6) complexes at 0 °C. Reasonable structures for AB(NH3)n were identified via density functional theory calculations, which indicate that the strong classical hydrogen bond formed between the lone pair of NH3 and the -NH3 of AB is the driving force for the absorption of ammonia by AB. By use of the van’t Hoff equation, the enthalpy change (ΔH) for AB to absorb one NH3 was determined to be −2.24 kcal/mol, which is in good agreement with the theoretical calculations. Other organic amines were screened to further confirm the role of the N lone pair; only 1,4-diazabicyclo[2.2.2]octane (DABCO) formed a stable adduct, which X-ray structural analysis showed was the DABCO-BH3 species. Finally, Raman spectra of AB(NH3)n were collected, and its unique spectral features are also discussed.
Novel TiO2(B)@anatase hybrid nanowires with a bicrystalline structure consisting of TiO2(B) core and anatase shell exhibit superior Li ion storage capacities, cycling stability and rate capability. Owing to the excellent electrochemical performance, TiO2(B)@anatase hybrid nanowires could be promising anode materials for lithium ion batteries.
Successful synthesis and investigation of a new material that uses copper-metal–organic frameworks (Cu-MOFs) as the template for loading LiBH4 are reported. The nanoconfinement of LiBH4 in the pores of Cu-MOFs results in an interaction between LiBH4 and Cu2+ ions, enabling the LiBH4@Cu-MOFs system to achieve a much lower dehydrogenation temperature than pristine LiBH4.
In this paper, ammine lithium borohydride (LiBH4·NH3) was successfully impregnated into multi-walled carbon nanotubes (CNTs) through a melting technique. X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller, and density measurements were employed to confirm the formation of the nanostructured LiBH4·NH3/CNTs composites. As a consequence, it was found that the dehydrogenation of the loaded LiBH4·NH3 was remarkably enhanced, showing an onset dehydrogenation at temperatures below 100 °C, together with a prominent desorption of pure hydrogen at around 280 °C, with a capacity as high as 6.7 wt.%, while only a trace of H2 liberation was present for the pristine LiBH4·NH3 in the same temperature range. Structural examination indicated that the significant modification of the thermal decomposition route of LiBH4·NH3 achieved in the present study is due to the CNT-assisted formation of B–N-based hydride composite, starting at a temperature below 100 °C. It is demonstrated that the formation of this B–N-based hydride covalently stabilized the [NH] groups that were weakly coordinated on Li cations in the pristine LiBH4·NH3via strong B–N bonds, and furthermore, accounted for the substantial hydrogen desorption at higher temperatures.
Co-reporter:M. Ismail, Y. Zhao, X.B. Yu, J.F. Mao, S.X. Dou
International Journal of Hydrogen Energy 2011 Volume 36(Issue 15) pp:9045-9050
Publication Date(Web):July 2011
DOI:10.1016/j.ijhydene.2011.04.132
In this study, we report the hydrogen absorption/desorption properties and reaction mechanism of the MgH2–NaAlH4 (4:1) composite system. This composite system showed improved dehydrogenation performance compared with that of as-milled NaAlH4 and MgH2 alone. The dehydrogenation process in the MgH2–NaAlH4 composite can be divided into four stages: NaAlH4 is first reacted with MgH2 to form a perovskite-type hydride, NaMgH3 and Al. In the second dehydrogenation stage, the Al phase reacts with MgH2 to form Mg17Al12 phase accompanied with the self-decomposition of the excessive MgH2. NaMgH3 goes on to decompose to NaH during the third dehydrogenation stage, and the last stage is the decomposition of NaH. Kissinger analysis indicated that the apparent activation energy, EA, for the MgH2-relevent decomposition in MgH2–NaAlH4 composite was 148 kJ/mol, which is 20 kJ/mol less than for as-milled MgH2 (168 kJ/mol). X-ray diffraction patterns indicate that the second, third, and fourth stages are fully reversible. It is believed that the formation of Al12Mg17 phase during the dehydrogenation process alters the reaction pathway of the MgH2–NaAlH4 (4:1) composite system and improves its thermodynamic properties.Highlights► We report the hydrogen absorption/desorption properties and reaction mechanism of the MgH2–NaAlH4 (4:1) composite system. ► This composite system showed improved dehydrogenation performance compared with that of as-milled NaAlH4 and MgH2 alone. ► The dehydrogenation process in the MgH2–NaAlH4 composite can be divided into four stages. ► X-ray diffraction patterns indicate that the second, third, and fourth stages are fully reversible. ► The formation of Mg17Al12 phase may play a critical role in the enhancement of dehydrogenation in MgH2–NaAlH4 composite.
International Journal of Hydrogen Energy 2011 Volume 36(Issue 21) pp:13640-13644
Publication Date(Web):October 2011
DOI:10.1016/j.ijhydene.2011.07.104
A kind of promising hydrogen storage material-hydrazine bisborane (N2H4(BH3)2, HBB) is synthesized by a typical chemical method. HBB exhibits relatively low dehydrogenation temperature (around 100 °C), effective prevention of any unwanted gaseous products, such as ammonia, diborane, confirming a very high hydrogen release purity of >99%. The activation energy (Ea) of the first-step dehydrogenation of HBB is calculated to be 106.4 kJ/mol using Kissinger’s method. According to the 11B NMR and FT-IR results, the thermal decomposition of HBB was determined to produce [HBN2BH]2 dimers, in which the coordination environment of B atoms located in the formation of HBN2.Highlights► The hydrogen storage properties of hydrazine bisborane is reported. ► The hydrazine bisborane refined to crystallize in the cubic system. ► The hydrazine bisborane shows a low dehydrogenation temperature without any unwanted gaseous products.
Co-reporter:Jianfeng Mao, Zaiping Guo, Xuebin Yu, Mohammad Ismail, Huakun Liu
International Journal of Hydrogen Energy 2011 Volume 36(Issue 9) pp:5369-5374
Publication Date(Web):May 2011
DOI:10.1016/j.ijhydene.2011.02.001
The mutual destabilization of LiAlH4 and MgH2 in the reactive hydride composite LiAlH4–MgH2 is attributed to the formation of intermediate compounds, including Li–Mg and Mg–Al alloys, upon dehydrogenation. TiF3 was doped into the composite for promoting this interaction and thus enhancing the hydrogen sorption properties. Experimental analysis on the LiAlH4–MgH2–TiF3 composite was performed via temperature-programmed desorption (TPD), differential scanning calorimetry (DSC), isothermal sorption, pressure-composition isotherms (PCI), and powder X-ray diffraction (XRD). For LiAlH4–MgH2–TiF3 composite (mole ratio 1:1:0.05), the dehydrogenation temperature range starts from about 60 °C, which is 100 °C lower than for LiAlH4–MgH2. At 300 °C, the LiAlH4–MgH2–TiF3 composite can desorb 2.48 wt% hydrogen in 10 min during its second stage dehydrogenation, corresponding to the decomposition of MgH2. In contrast, 20 min was required for the LiAlH4–MgH2 sample to release so much hydrogen capacity under the same conditions. The hydrogen absorption properties of the LiAlH4–MgH2–TiF3 composite were also improved significantly as compared to the LiAlH4–MgH2 composite. A hydrogen absorption capacity of 2.68 wt% under 300 °C and 20 atm H2 pressure was reached after 5 min in the LiAlH4–MgH2–TiF3 composite, which is larger than that of LiAlH4–MgH2 (1.75 wt%). XRD results show that the MgH2 and LiH were reformed after rehydrogenation.
Journal of Alloys and Compounds 2011 Volume 509(Supplement 2) pp:S724-S727
Publication Date(Web):September 2011
DOI:10.1016/j.jallcom.2010.11.076
The thermal decomposition properties of Ca(BH4)2/LiNH2 system were investigated. It was found that the mixtures started to release hydrogen at around 250 °C, but accompanied emission of ammonia at lower temperature was also occurred. XRD results revealed that, after a shot time of ball mining, the Ca(BH4)2/LiNH2 mixtures transferred to unidentified new phases and the decomposed product mainly consists of LiCa4(BN2)3. Further improvement on restraining the ammonia release can be achieved by heating treatment of this composite or addition of LiH to the binary system.Research highlights▶ Thermal decomposition properties of a combined Ca(BH4)2/LiNH2 system. ▶ The dehydrogenation of Ca(BH4)2/LiNH2 results in the formation of LiCa4(BN2)3. ▶ Further improvement on the dehydrogenation can be achieved by addition of LiH. ▶ The dehydrogenation is based on a combination of BH and NH sources.
International Journal of Hydrogen Energy 2011 Volume 36(Issue 12) pp:7128-7135
Publication Date(Web):June 2011
DOI:10.1016/j.ijhydene.2011.03.060
Though LiBH4–MgH2 system exhibits an excellent hydrogen storage property, it still presents high decomposition temperature over 350 °C and sluggish hydrogen absorption/desorption kinetics. In order to improve the hydrogen storage properties, the influence of MoCl3 as an additive on the hydrogenation and dehydrogenation properties of LiBH4–MgH2 system is investigated. The reversible hydrogen storage performance is significantly improved, which leads to a capacity of about 7 wt.% hydrogen at 300 °C. XRD analysis reveals that the metallic Mo is formed by the reaction between LiBH4 and MoCl3, which is highly dispersed in the sample and results in improved dehydrogenation and hydrogenation performance of LiBH4–MgH2 system. From Kissinger plot, the activation energy for hydrogen desorption of LiBH4–MgH2 system with additive MoCl3 is estimated to be ∼43 kJ mol−1 H2, 10 kJ mol−1 lower than that for the pure LiBH4–MgH2 system indicating that the kinetics of LiBH4–MgH2 composite is significantly improved by the introduction of Mo.Highlights► The influence of MoCl3 as an additive on the hydrogenation and dehydrogenation properties of LiBH4–MgH2 was investigated. ► The reversible hydrogen storage properties of LiBH4–MgH2 at 300 °C, with a capacity of about 7 wt.% hydrogen, was significantly improved by addition of MoCl3. ► The improved hydrogen storage properties of LiBH4–MgH2 is attributed to the formation of metallic Mo through the reaction of LiBH4 and MoCl3.
Co-reporter:Jianfeng Mao, Zaiping Guo, Xuebin Yu, Huakun Liu
Journal of Alloys and Compounds 2011 Volume 509(Issue 15) pp:5012-5016
Publication Date(Web):14 April 2011
DOI:10.1016/j.jallcom.2011.02.004
The LiBH4–MgH2 system has a high reversible hydrogen storage capacity. However, the hydrogen de/absorption kinetics has to be further enhanced for its practical application. Motivated by the possibility that the metal catalysts facilitating the dissociation and combination of hydrogen molecules and activating Mg–H and B–H bonds, a novel catalyst, ruthenium nanoparticles supported on multiwalled carbon nanotubes (Ru/C) is prepared and its effect on the hydrogen sorption properties of LiBH4–MgH2 systems is investigated. The experimental results show that the Ru/C catalyst is active in reducing the dehydrogenation temperature and enhancing the dehydrogenation kinetics. Furthermore, the reversible capacity is also markedly enhanced under moderate conditions, and the catalytically enhanced hydrogen absorption capacity persists well during three de/rehydrogenation cycles.Research highlights► Ruthenium nanoparticles supported on multiwalled carbon nanotubes as catalyst. ► Catalysing the LiBH4–MgH2 system with improved hydrogen storage properties. ► Hydrogen de/absorption test revealed a significant increase in the rate of de/absorption as well as the weight percentage of hydrogen absorbed with catalyst.
The Journal of Physical Chemistry C 2011 Volume 115(Issue 7) pp:3188-3193
Publication Date(Web):February 3, 2011
DOI:10.1021/jp111218t
A combined hydrogen storage system of Ca(BH4)2/[C(NH2)3]+[BH4]− (GBH) complexes is reported. By a short time ball milling of Ca(BH4)2 and GBH, a new composite of Ca(BH4)2/GBH complex was produced. It was found that the newly formed composite exhibits a significant improvement of dehydrogenation, which not only decreases the onset dehydrogenation to around 60 °C, but also depresses the emission of ammonia from GBH thoroughly, leading to more than 10 wt % fairly pure H2 released below 300 °C. Further investigations revealed that the complexation between Ca(BH4)2 and GBH as well as balancing the protic and hydridic hydrogen are two crucial factors in improvement of the dehydrogenation of this system, which may serve as a new strategy for developing the new boron−nitrogen−hydrogen system as hydrogen storage materials.
Co-reporter:Jianfeng Mao ; Zaiping Guo ; Xuebin Yu ;Huakun Liu
The Journal of Physical Chemistry C 2011 Volume 115(Issue 18) pp:9283-9290
Publication Date(Web):April 14, 2011
DOI:10.1021/jp2020319
NaBH4, with a 10.6 wt % theoretical H2 capacity, is a promising hydrogen storage candidate material. However, the high thermodynamic stability and slow H-exchange kinetics have to be improved for its practical use. In this study, NaBH4 was destabilized by using CaH2 or Ca(BH4)2. Temperature-programmed desorption experiments revealed a significant improvement in the decomposition temperature and the rate of desorption, as well as the weight percentage of hydrogen released from composites with the additive upon heating to 500 °C. X-ray diffraction has confirmed the formation of CaB6 upon dehydrogenation, which stabilizes the dehydrogenated state of boron and, therefore, destabilizes the NaBH4. Interestingly, as a source of CaH2, the addition of Ca(BH4)2 results in superior hydrogen desorption performance compared with that of CaH2. To fully characterize this composite system, xNaBH4 + Ca(BH4)2 composites, for several x values between 1 and 20, were systematically investigated by a series of dehydrogenation and structural analyses. Furthermore, partial reversibility of the NaBH4/Ca(BH4)2 composite with and without NbF5 catalyst was also confirmed under moderate conditions. The mechanism underlying the characteristic enhancement in the NaBH4/CaH2 and NaBH4/Ca(BH4)2 is also discussed.
Chemical Communications 2010 vol. 46(Issue 15) pp:2599-2601
Publication Date(Web):04 Feb 2010
DOI:10.1039/B924057H
Amminelithium borohydride, LiBH4·NH3 which has two temperature sensitive chemical bonds N:→Li+ and N–H⋯H–B, is shown to release hydrogen at low temperatures by stabilizing the ammonia and promoting the recombination of the NH⋯HB bond.
Under optimized synthesis conditions, very large area uniform SnO2 nanofibers consisting of orderly bonded nanoparticles have been obtained for the first time by thermal pyrolysis and oxidization of electrospun tin(II)2-ethylhexanoate/polyacrylonitrile (PAN) polymer nanofibers in air. The structure and morphology were elaborated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The SnO2 nanofibers delivered a reversible capacity of 446 mAh g−1 after 50 cycles at the 100 mA g−1 rate and excellent rate capability of 477.7 mAh g−1 at 10.0 C. Owing to the improved electrochemical performance, this electrospun SnO2 nanofiber could be one of the most promising candidate anode materials for the lithium-ion battery.
Co-reporter:Jianfeng Mao, Zaiping Guo, Xuebin Yu, Huakun Liu, Zhu Wu, Jun Ni
International Journal of Hydrogen Energy 2010 Volume 35(Issue 10) pp:4569-4575
Publication Date(Web):May 2010
DOI:10.1016/j.ijhydene.2010.02.107
MgH2 is one of the most promising hydrogen storage materials due to its high capacity and low cost. In an effort to develop MgH2 with a low dehydriding temperature and fast sorption kinetics, doping MgH2 with NiCl2 and CoCl2 has been investigated in this paper. Both the dehydrogenation temperature and the absorption/desorption kinetics have been improved by adding either NiCl2 or CoCl2, and a significant enhancement was obtained in the case of the NiCl2 doped sample. For example, a hydrogen absorption capacity of 5.17 wt% was reached at 300 °C in 60 s for the MgH2/NiCl2 sample. In contrast, the ball-milled MgH2 just absorbed 3.51 wt% hydrogen at 300 °C in 400 s. An activation energy of 102.6 kJ/mol for the MgH2/NiCl2 sample has been obtained from the desorption data, 18.7 kJ/mol and 55.9 kJ/mol smaller than those of the MgH2/CoCl2, which also exhibits an enhanced kinetics, and of the pure MgH2 sample, respectively. In addition, the enhanced kinetics was observed to persist even after 9 cycles in the case of the NiCl2 doped MgH2 sample. Further kinetic investigation indicated that the hydrogen desorption from the milled MgH2 is controlled by a slow, random nucleation and growth process, which is transformed into two-dimensional growth after NiCl2 or CoCl2 doping, suggesting that the additives reduced the barrier and lowered the driving forces for nucleation.
International Journal of Hydrogen Energy 2010 Volume 35(Issue 12) pp:6338-6344
Publication Date(Web):June 2010
DOI:10.1016/j.ijhydene.2010.03.089
The effect of Ti0.4Cr0.15Mn0.15V0.3 (termed BCC due to the body centered cubic structure) alloy on the hydrogen storage properties of MgH2 was investigated. It was found that the hydrogenated BCC alloy showed superior catalysis properties compared to the quenched and ingot samples. As an example, the 1 h milled MgH2 + 20 wt.% hydrogenated BCC shows a peak temperature of dehydrogenation of about 294 °C. This is 16, 27 and 74 °C lower than those of MgH2 ball milled with quenched BCC, ingot BCC and an uncatalysed MgH2 sample, respectively. The hydrogenated BCC alloy is much easier to crush into small particles, and embed in MgH2 aggregates as revealed by X-ray diffraction and scanning electron microscope results. The BCC not only increases the hydrogen atomic diffusivity in the bulk Mg but also promotes the dissociation and recombination of hydrogen. The activation energy, Ea, for the dehydrogenation of the MgH2/hydrogenated BCC mixture was found to be 71.2 ± 5 kJ mol H2−1 using the Kissinger method. This represents a significant decrease compared to the pure MgH2 (179.7 ± 5 kJ mol H2−1), suggesting that the catalytic effect of the BCC alloy significantly decreases the activation energy of MgH2 for dehydrogenation by surface activation.
The Journal of Physical Chemistry C 2010 Volume 114(Issue 41) pp:17947-17953
Publication Date(Web):September 28, 2010
DOI:10.1021/jp1075753
Promotion of dehydrogenation based on a combination of [BH] and [NH] sources has been demonstrated to be an effective approach in developing an advanced borohydride/amide multicompound hydrogen storage system. In this article, the hydrogen storage properties of Mg(NH2)2−LiBH4 composite are studied systematically. It has been shown that the Mg(NH2)2−LiBH4 binary system exhibits an onset dehydrogenation temperature of 250 °C, accompanied by an emission of 5.5 mol % ammonia. Further investigation has revealed that addition of metal chlorides results in significant improvement of the dehydrogenation of Mg(NH2)2−LiBH4. In particular, with NiCl2 addition up to 20 wt %, the modified composite exhibits more favorable thermodynamics, as demonstrated by an onset dehydrogenation temperature as low as 60 °C, accompanied by the suppressed evolution of byproduct NH3 (2 mol %), which enables this modified system to release 7.3 wt % hydrogen in the temperature range of 60−400 °C, which is vastly superior compared with the dehydrogenation of Mg(NH2)2−LiBH4 alone. X-ray diffraction results indicate that the presence of Mg(NH2)2 results in an accelerated exchange reaction between LiBH4 and NiCl2, which may be the dominant reason for the improved thermodynamics and kinetics in the NiCl2-added Mg(NH2)2−LiBH4 system.
Co-reporter:S. F. Li ; Y. H Guo ; W. W. Sun ; D. L. Sun ;X. B. Yu
The Journal of Physical Chemistry C 2010 Volume 114(Issue 49) pp:21885-21890
Publication Date(Web):November 18, 2010
DOI:10.1021/jp1091152
In this paper, the dehydrogenation properties of ammonia-borane (AB, NH3BH3) modified with platinum nanoparticle functionalized carbon nanotubes (CNTs) (Pt@CNTs) that were prepared through a new “ammonia-deliquescence” method are reported. It has been demonstrated that the synergetic catalysis of CNTs and platinum nanoparticles, and the nanoconfinement of AB incorporated into the CNTs are two crucial factors in enhancing the dehydrogenation of AB. Both CNTs and platinum nanoparticles showed favorable catalytic activities toward the thermolysis of AB, which not only depressed the emission of the poisonous byproduct borazine, but also prevented severe material foaming and expansion during the decomposition. Meanwhile, the nanoconfinement of AB through the “ammonia-deliquescence” method led to enhanced dehydrogenation kinetics, releasing the first equivalent of hydrogen at 70 °C within 5 h, while no hydrogen was released from pristine AB under the same conditions. By the Arrhenius method, the activation energy of the modified AB was calculated to be 106.2 kJ mol−1, which is reduced considerably compared to the activation energy for the pristine AB (137.8 kJ mol−1). These results indicate that the “ammonia-deliquescence” method combined with the utilization of Pt@CNTs as catalyst is an effective approach in modifying the properties of AB with favorable dehydrogenation.
Co-reporter:Guanglin Xia Dr. ;Yanhui Guo;Zhu Wu ;Chuanzhen Yang ;Huangkun Liu ;Shixue Dou
Chemistry - A European Journal 2010 Volume 16( Issue 12) pp:3763-3769
Publication Date(Web):
DOI:10.1002/chem.200903220
Abstract
The monoammoniate of lithium amidoborane, Li(NH3)NH2BH3, was synthesized by treatment of LiNH2BH3 with ammonia at room temperature. This compound exists in the amorphous state at room temperature, but at −20 °C crystallizes in the orthorhombic space group Pbca with lattice parameters of a=9.711(4), b=8.7027(5), c=7.1999(1) Å, and V=608.51 Å3. The thermal decomposition behavior of this compound under argon and under ammonia was investigated. Through a series of experiments we have demonstrated that Li(NH3)NH2BH3 is able to absorb/desorb ammonia reversibly at room temperature. In the temperature range of 40–70 °C, this compound showed favorable dehydrogenation characteristics. Specifically, under ammonia this material was able to release 3.0 equiv hydrogen (11.18 wt %) rapidly at 60 °C, which represents a significant advantage over LiNH2BH3. It has been found that the formation of the coordination bond between ammonia and Li+ in LiNH2BH3 plays a crucial role in promoting the combination of hydridic BH bonds and protic NH bonds, leading to dehydrogenation at low temperature.
The Journal of Physical Chemistry C 2010 Volume 114(Issue 20) pp:9534-9540
Publication Date(Web):May 5, 2010
DOI:10.1021/jp103012t
The dehydrogenation properties and mechanism of MgCl2(NH3)/MBH4 (here, M is Li or Na) were investigated by thermogravimetric analysis and mass spectrometry, X-ray diffraction (XRD), solid-state 11B NMR, Fourier transform infrared, and differential scanning calorimetry (DSC). As for the MgCl2(NH3)/LiBH4 system, it was found that a new phase, namely, MgCl2(NH3)·LiBH4, to which the following dehydrogenation relates, is formed after ball milling. Judging from the reaction products, it is confirmed that MgCl2 is inclined to work as an ammonia carrier, and the ligand NH3, transferring from MgCl2, is able to combine with the LiBH4 to release H2 with a trace of ammonia at ca. 240 °C. With the increase of LiBH4 content in the mixture, the emission of ammonia was totally suppressed, and Mg(BH4)2 was produced by the decomposition reaction of MgCl2 with the excessive LiBH4 after the ligand NH3 was exhausted, resulting in an improved dehydrogenation in the whole system. As for the MgCl2(NH3)/NaBH4 system, no new phases are detected by XRD after ball milling. The MgCl2 works as a BH4− acceptor, and the ligand NH3 stays with Mg2+ to combine with the BH4−, which transfers from NaBH4 to Mg2+, resulting in a totally different decomposition route and thermal effects as compared with the MgCl2(NH3)/LiBH4 system. DSC results revealed that the decomposition of MgCl2(NH3)/LiBH4 presented an exothermic reaction with an enthalpy of −3.8 kJ mol−1 H2, while the MgCl2(NH3)/NaBH4 showed two apparent endothermic peaks associated with its two-step dehydrogenation with enthalpies of 8.6 and 2.2 kJ mol−1 H2, respectively. Moreover, the MS profiles of the MgCl2(NH3)/2NaBH4, with excessive BH4−, still released a trace of NH3, indicating that the NaBH4 is not so effective in suppressing the emission of NH3 as LiBH4 did.
Co-reporter:Jianfeng Mao, Zaiping Guo, Haiyan Leng, Zhu Wu, Yanhui Guo, Xuebin Yu and Huakun Liu
The Journal of Physical Chemistry C 2010 Volume 114(Issue 26) pp:11643-11649
Publication Date(Web):June 10, 2010
DOI:10.1021/jp1012208
This paper reports the hydrogen storage properties of a ternary hydride system, LiAlH4−MgH2−LiBH4 (molar ratio 1:1:1), both undoped and doped with TiF3 addition. It was found that there is a mutual destabilization among the three hydrides. This new ternary system possesses superior hydrogen desorption properties compared with the unary components (LiAlH4, MgH2, and LiBH4) or binary mixtures of those components (LiAlH4−MgH2, LiAlH4−LiBH4, and MgH2−LiBH4). On doping with TiF3, the system starts to release hydrogen at 60 °C and completes dehydrogenation below 400 °C. Three major dehydrogenation steps were observed in the undoped and TiF3-doped systems, which corresponds to the decomposition of LiAlH4, MgH2, and LiBH4, respectively. X-ray diffraction (XRD) measurements on the as-dehydrogenated samples were executed to identify the dehydrogenation pathway. The third step decomposition enthalpy of the doped system was determined by pressure−composition−temperature (PCT) measurements and the van’t Hoff equation to be 54 kJ/mol H2, which is smaller than that of LiBH4 alone (74 kJ/mol H2). In addition, the TiF3-doped system is partially reversible at moderate temperature and pressure (4 MPa, 400 °C) with good cycling. The enhancement of the hydrogen sorption properties was attributed to the formation of intermediate compounds, including Li−Mg, Mg−Al, and Mg−Al−B alloys, upon dehydrogenation, which change the thermodynamics of the reactions through altering the de/rehydrogenation pathway. The TiF3 component in the doped system plays a catalytic role through the formation of Ti-containing and F-containing catalytic species, which strengthens this interaction and thus further improves the dehydrogenation and hydrogenation of this system.
Co-reporter:Y. H. Guo, W. W. Sun, Z. P. Guo, H. K. Liu, D. L. Sun and X. B. Yu
The Journal of Physical Chemistry C 2010 Volume 114(Issue 29) pp:12823-12827
Publication Date(Web):July 2, 2010
DOI:10.1021/jp1038255
Amminelithium borohydride (LiBH4·NH3) is one of the most hydrogen-rich inorganic materials, showing potential application for hydrogen storage. In this paper, the dehydrogenation of LiBH4·NH3 was promoted significantly through heating in ammonia atmosphere which demonstrated that the coordinate between NH3 and LiBH4 is a crucial factor in inducing the hydrogen release for this system. Meanwhile, several metal hydrides LiH, NaH, and CaH2 were found to be effective in promoting the dehydrogenation of LiBH4·NH3. Among the studied additives, the effect of LiH, as an example, was discussed in detail. It was found that the promotion of dehydrogenation through LiH is due to the reaction: 3LiH + 3LiBH4·NH3 → Li4BN3H10 + 2LiBH4 + 3H2, releasing hydrogen from 60 °C.
Co-reporter:Liang Gao, Yan Hui Guo, Guang Lin Xia and Xue Bin Yu
Journal of Materials Chemistry A 2009 vol. 19(Issue 42) pp:7826-7829
Publication Date(Web):29 Sep 2009
DOI:10.1039/B916503G
A new complex material system, Mg(NH3)nCl2–nLiBH4 (here n can be 1, 2 and 6), in which the MgCl2 works as ammonia carrier but plays a crucial role in promoting the interaction between LiBH4 and NH3 to release hydrogen at temperature below 100 °C, is reported.
Journal of Alloys and Compounds 2009 Volume 487(1–2) pp:434-438
Publication Date(Web):13 November 2009
DOI:10.1016/j.jallcom.2009.07.158
We have investigated the hydrogen storage properties of the LiAlH4–LiBH4 system, both un-doped and doped with titanium based catalysts. It was found that TiF3 exhibited the superior catalytic effects in terms of enhancing the hydriding/dehydriding kinetics and reducing the dehydrogenation temperature of the LiAlH4–LiBH4 system. Compared to the un-doped LiAlH4–LiBH4 system, the onset temperatures of the 5 mol% TiF3-doped sample for the first and second dehydrogenation steps were decreased by 64 and 150 °C, respectively. X-ray diffraction patterns of the dehydrogenated samples revealed that the produced Al from LiAlH4 could react with B from the decomposition of LiBH4 to form AlB2 and LiAl compounds. Pressure-composition-temperature (PCT) and van’t Hoff plots made it clear that the decomposition enthalpy of LiBH4 in the TiF3-doped LiAlH4–LiBH4 system is decreased from 74 kJ/(mol of H2) for the pure LiBH4 to 60.4 kJ/(mol of H2). The dehydrogenation products of the TiF3-doped LiAlH4–LiBH4 sample can absorb 3.76 and 4.78 wt.% of hydrogen in 1 h and 14 h, respectively, at 600 °C and under 4 MPa of hydrogen. The formation of LiBH4 was detected by X-ray diffraction in the rehydrogenated sample.
Co-reporter:X. B. Yu, D. M. Grant and G. S. Walker
The Journal of Physical Chemistry C 2009 Volume 113(Issue 41) pp:17945-17949
Publication Date(Web):September 18, 2009
DOI:10.1021/jp906519p
Lithium borohydride is a promising candidate for hydrogen storage and fuel cell application due to its high hydrogen content. In the present work, the effect of various oxides on the dehydrogenation of LiBH4 was investigated. The MS-TG results showed that the LiBH4/oxide mixtures were able to dehydrogenate at much lower temperatures; for example, the onset of dehydrogenation was below 100 °C for a LiBH4−Fe2O3 mixture with a mass ratio of 1:2, and the majority of the hydrogen (∼6 wt %) could be released after heating to 200 °C. The order of destabilization effect for LiBH4 for the studied oxides was Fe2O3 > V2O5 > Nb2O5 > TiO2 > SiO2. XRD results revealed that the destabilization of LiBH4 by the oxides resulted from a redox reaction of LiBH4 + MOx → LiMOx + B + 2H2. Investigation of mixed metal oxides showed that a TiO2/SiO2 sample produced an even greater effect, decreasing the temperature of hydrogen release from LiBH4 by more than either TiO2 and SiO2 alone.
Co-reporter:J. F. Mao, X. B. Yu, Z. P. Guo, C. K. Poh, H. K. Liu, Z. Wu and J. Ni
The Journal of Physical Chemistry C 2009 Volume 113(Issue 24) pp:10813-10818
Publication Date(Web):May 21, 2009
DOI:10.1021/jp808269v
The hydrogen storage properties of a combined LiAlH4−NaBH4 system have been investigated. It was found that there is a mutual destabilization between the LiAlH4 and the NaBH4. Two major dehydrogenation steps with hydrogen capacities of 3.1 wt % and 5.2 wt % were observed for the system with a molar ratio of LiAlH4:NaBH4 = 1:1 at around 250 and 600 °C, respectively. The onset dehydrogenation temperatures for the first and the second steps in the LiAlH4−NaBH4 mixture were decreased to 95 and 450 °C, respectively, which are 30 and 50 °C lower than those of bare LiAlH4 and NaBH4, respectively. Furthermore, doping with TiF3 significantly decreases the hydrogen release temperature compared to the undoped system. The TiF3 doping can further decrease the onset temperatures of the first and second steps to 60 and 300 °C. The presence of TiF3 also destabilizes the NaH phase, which leads to an increased desorption capacity. Pressure−composition−temperature (PCT) and van’t Hoff plots illustrate that the decomposition enthalpy of NaBH4 in the TiF3-doped LiAlH4−NaBH4 system is decreased from 106.8 kJ/(mol of H2) for pure NaBH4 to 68.16 kJ/(mol of H2). In addition, about 4 wt % hydrogen can be reversibly stored by the dehydrogenated product, and the formation of NaBH4 was detected by X-ray diffraction in the rehydrogenated sample.
Co-reporter:X. B. Yu, Y. H. Guo, H. Yang, Z. Wu, D. M. Grant and G. S. Walker
The Journal of Physical Chemistry C 2009 Volume 113(Issue 13) pp:5324-5328
Publication Date(Web):2017-2-22
DOI:10.1021/jp810504w
MgH2 surface modified with nanosized Ti0.4Cr0.15Mn0.15V0.3 alloy was prepared by a short ball mill period with hydrogenated Ti0.4Cr0.15Mn0.15V0.3 alloy. The catalyzed MgH2 showed attractive absorption/desorption properties, desorbing 5.7 wt % hydrogen in 30 min at 290 °C and absorbing more than 90% of its initial hydrogen capacity with 100 min even at below 100 °C. Moreover, the hydrogen capacity did not show any significant decrease after 73 cycles. It was proposed that the BCC particles with a highly dispersed nanosize and/or amorphous phase on the surface of MgH2 play a crucial role in significantly improving the kinetic properties of the MgH2.
Successful synthesis and investigation of a new material that uses copper-metal–organic frameworks (Cu-MOFs) as the template for loading LiBH4 are reported. The nanoconfinement of LiBH4 in the pores of Cu-MOFs results in an interaction between LiBH4 and Cu2+ ions, enabling the LiBH4@Cu-MOFs system to achieve a much lower dehydrogenation temperature than pristine LiBH4.
Journal of Materials Chemistry A 2014 - vol. 2(Issue 27) pp:NaN10687-10687
Publication Date(Web):2014/05/08
DOI:10.1039/C4TA01631A
Three organic amine-boranes—diethylenetriamine-borane (C4H13N3·3BH3, DETAB), triethylenetetramine-borane (C6H18N4·4BH3, TETAB) and tetraethylenepentamine-borane (C8H23N5·5BH3, TEPAB)—are synthesized via the liquid-phase reaction of diethylenetriamine (C4H13N3, DETA), triethylenetetramine (C6H18N4, TETA) and tetraethylenepentamine (C8H23N5, TEPA), respectively, with BH3–THF solution. By using high-resolution synchrotron powder X-ray diffraction (HR-XRD), Fourier transform infrared (FTIR), elemental analysis and solid-state 11B nuclear magnetic resonance (NMR) measurements, the structural properties of the three compounds are characterized. Hydrogen desorption properties of these compounds are measured by temperature-programmed desorption (TPD) and thermogravimetry (TG) over a temperature range from 50 to 250 °C, in which 5.5, 6.6 and 6.9 equivalents hydrogen are released in two steps based on the combination of protic (N–H) and hydridic (B–H) hydrogens. It is confirmed by mass spectrometry (MS) results that only H2 is liberated during the thermal decomposition of the three compounds. The dynamics are investigated by isothermal dehydrogenation at various temperatures. Compared with ammonia borane (NH3BH3, AB), these compounds show a faster dehydrogenation rate. A regeneration study shows that DETAB can be regenerated by treating its dehydrogenated products with lithium aluminium hydride (LiAlH4) and ammonium chloride (NH4Cl) at room temperature.
Co-reporter:Guanglin Xia, Xiaowei Chen, Cuifeng Zhou, Chaofeng Zhang, Dan Li, Qinfen Gu, Zaiping Guo, Huakun Liu, Zongwen Liu and Xuebin Yu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 24) pp:NaN12652-12652
Publication Date(Web):2015/05/14
DOI:10.1039/C5TA00259A
A Li–Mg–N–H system is a highly promising source of hydrogen storage materials due to its favorable thermodynamics and potential reversibility. Its application has been greatly hindered, however, by its rather high activation energy barriers. Herein, we report a novel multi-reaction methodology for the synthesis of nanosized Li2Mg(NH)2 space-confined into thin-film hollow carbon spheres (THCSs) with a uniform dispersion. It shows that a completely depressed release of ammonia and reversible hydrogen sorption at a temperature of 105 °C, the lowest temperature reported so far, were achieved for the nano-confined Li2Mg(NH)2. Furthermore, a stable cycling capacity close to the theoretical value was also successfully realized, even through up to 20 cycles of de-/re-hydrogenation.
Co-reporter:Yingbin Tan, Yanhui Guo, Shaofeng Li, Weiwei Sun, Yihan Zhu, Qian Li and Xuebin Yu
Journal of Materials Chemistry A 2011 - vol. 21(Issue 38) pp:NaN14515-14515
Publication Date(Web):2011/08/11
DOI:10.1039/C1JM11158B
A novel eutectic hydrogen storage system, LiBH4·NH3–nNH3BH3, which exists in a liquid state at room temperature, was synthesized through a simple mixing of LiBH4·NH3 and NH3BH3 (AB). In the temperature range of 90–110 °C, the eutectic system showed significantly improved dehydrogenation properties compared to the neat AB and LiBH4·NH3 alone. For example, in the case of the LiBH4·NH3/AB with a mole ratio of 1:3, over 8 wt.% hydrogen could be released at 90 °C within 4 h, while only 5 wt.% hydrogen released from the neat AB at the same conditions. Through a series of experiments it has been demonstrated that the hydrogen release of the new system is resulted from an interaction of AB and the NH3 group in the LiBH4·NH3, in which LiBH4 works as a carrier of ammonia and plays a crucial role in promoting the interaction between the NH3 group and AB. The enhanced dehydrogenation of LiBH4·NH3/AB may result from the polar liquid state reaction environments and the initially promoted formation of the diammoniate of diborane, which will facilitate the B–H⋯H–N interaction between LiBH4·NH3 and AB. Kinetics analysis revealed that the rate-controlling steps of the dehydrogenation process are three-dimensional diffusion of hydrogen at temperatures ranging from 90 to 110 °C.
Chemical Communications 2010 - vol. 46(Issue 15) pp:NaN2601-2601
Publication Date(Web):2010/02/04
DOI:10.1039/B924057H
Amminelithium borohydride, LiBH4·NH3 which has two temperature sensitive chemical bonds N:→Li+ and N–H⋯H–B, is shown to release hydrogen at low temperatures by stabilizing the ammonia and promoting the recombination of the NH⋯HB bond.
Co-reporter:Ziwei Tang, Shaofeng Li, Zunxian Yang and Xuebin Yu
Journal of Materials Chemistry A 2011 - vol. 21(Issue 38) pp:NaN14621-14621
Publication Date(Web):2011/08/15
DOI:10.1039/C1JM12190A
An effective strategy of utilizing electrospinning techniques to fabricate MgCl2 catalyzed ammonia borane (AB) nanofibers with a tunable fiber diameter is reported. The synergistic effect obtained by combining nanofibers and metallic catalyst plays a crucial role in the decomposition of MgCl2-doped AB nanofibers, which leads to significant improvements in dehydrogenation kinetics and complete suppression of unwanted byproducts. The results of dehydrogenation show that MgCl2-doped AB nanofibers were able to release over 10.0 wt % pure H2 below 100 °C with favorable kinetics, a significant advance over releases from bulk AB. Furthermore, the dehydrogenation of MgCl2-doped AB nanofibers gives a weak exothermic reaction, −3.84 kJ mol−1 H2, which is dramatically lower than that of neat AB (−21 kJ mol−1 H2), which suggests that the electrospun sample is potentially more feasible to reverse. The findings in this paper provide general guidelines and inspiration for the design and synthesis of novel nano-fibrous materials with controllable dimensions for hydrogen storage applications.
Co-reporter:Guanglin Xia, Qinfen Gu, Yanhui Guo and Xuebin Yu
Journal of Materials Chemistry A 2012 - vol. 22(Issue 15) pp:NaN7307-7307
Publication Date(Web):2012/03/06
DOI:10.1039/C2JM16370E
The synthesis and dehydrogenation performance of purified NaZn(BH4)3 with a new phase and its novel ammine metal borohydride, NaZn(BH4)3·2NH3, were first reported. Structure analysis shows that NaZn(BH4)3·2NH3 crystallizes in an orthorhombic structure with lattice parameters of a = 7.2965(2) Å, b = 10.1444(2) Å and c = 12.9714(3) Å and space group P21nb, in which the Zn atoms are located in a tetrahedral coordination environment with two NH3 molecules and two BH4− units, presenting a novel 3D framework comprised of isolated BH4−1 units and [NaZn(BH4)2(NH3)2]+ complexes. Dehydrogenation results showed that the ZnCl2 assisted NaZn(BH4)3·2NH3 is able to release 7.9 wt% hydrogen at 110 °C without the concomitant release of undesirable gases such as ammonia and/or boranes, thereby demonstrating the potential of the ammoniated Zn-based borohydrides to be used as solid hydrogen storage materials.
Co-reporter:Ziwei Tang, Yingbin Tan, Xiaowei Chen and Xuebin Yu
Chemical Communications 2012 - vol. 48(Issue 74) pp:NaN9298-9298
Publication Date(Web):2012/07/25
DOI:10.1039/C2CC34932A
Regenerable hydrogen storage of lithium amidoborane is firstly achieved through the routes of direct thermal dehydrogenation and subsequent chemical hydrogenation of its dehydrogenated products by treatment with hydrazine in liquid ammonia.
Co-reporter:Ziwei Tang, Shaofeng Li, Weina Yang and Xuebin Yu
Journal of Materials Chemistry A 2012 - vol. 22(Issue 25) pp:NaN12758-12758
Publication Date(Web):2012/05/01
DOI:10.1039/C2JM30382E
A novel strategy of adopting the reversible swelling effect of a promising scaffold—hypercrosslinked porous poly(styrene-co-divinylbenzene) resin (PSDB) to nanoconfine hydrogen storage materials is reported, in which nanoconfined ammonia–borane (AB) is endowed with high loading ratio and significantly improved hydrogen storage capabilities. To verify the importance of swelling behavior displayed by this polymeric scaffold in dehydrogenation, an ammonia-dissolving route (PSDB–AB (NH3)) that does not involve swelling, was performed to enable direct comparison with the methanol-dissolving route (PSDB–AB (CH3OH)). Moreover, solid-state 11B NMR measurements were employed to illustrate the different reaction mechanisms in these two PSDB-confined AB samples, where decomposition involving both the diammoniate of diborane (DADB) and linear dimer are observed for PSDB–AB (NH3) but only the latter route is seen for PSDB–AB (CH3OH), deeply demonstrating the difference of dehydrogenation properties in these two samples. Our findings establish a prospective approach via utilizing this class of polymers for promoting the design and construction of advanced energy materials with high performances.
In this paper, ammine lithium borohydride (LiBH4·NH3) was successfully impregnated into multi-walled carbon nanotubes (CNTs) through a melting technique. X-ray diffraction, scanning electron microscopy, Brunauer–Emmett–Teller, and density measurements were employed to confirm the formation of the nanostructured LiBH4·NH3/CNTs composites. As a consequence, it was found that the dehydrogenation of the loaded LiBH4·NH3 was remarkably enhanced, showing an onset dehydrogenation at temperatures below 100 °C, together with a prominent desorption of pure hydrogen at around 280 °C, with a capacity as high as 6.7 wt.%, while only a trace of H2 liberation was present for the pristine LiBH4·NH3 in the same temperature range. Structural examination indicated that the significant modification of the thermal decomposition route of LiBH4·NH3 achieved in the present study is due to the CNT-assisted formation of B–N-based hydride composite, starting at a temperature below 100 °C. It is demonstrated that the formation of this B–N-based hydride covalently stabilized the [NH] groups that were weakly coordinated on Li cations in the pristine LiBH4·NH3via strong B–N bonds, and furthermore, accounted for the substantial hydrogen desorption at higher temperatures.
Co-reporter:Xiaowei Chen, Feng Yuan, Qinfen Gu and Xuebin Yu
Journal of Materials Chemistry A 2013 - vol. 1(Issue 38) pp:NaN11710-11710
Publication Date(Web):2013/07/31
DOI:10.1039/C3TA11940H
The structural stability and hydrogen adsorption capacity of an alkali (Li, Na and K) and alkali earth (Mg and Ca) metal atom decorated covalent triazine-based framework (CTF-1) are studied using ab initio density functional calculations. The calculation results revealed that Li, Na, K and Ca atoms can be adsorbed on the CTF-1 with the formation of a uniform and stable coverage due to the charge transfer between the metal atoms and the CTF-1 substrate, thus avoiding the clustering problem that occurs for the decoration of metal atoms on other substrates. The metal decorated CTF-1 could adsorb up to 30 hydrogen molecules with an average binding energy of ∼0.16–0.26 eV/H2, corresponding to a gravimetric density of 12.3, 10.3 and 8.8 wt% for the CTF–Li6, CTF–Na6 and CTF–Ca6 complexes, respectively, thereby enabling the Li, Na and Ca decorated covalent triazine-based frameworks to be very promising materials for effective reversible hydrogen storage at near ambient conditions.
Co-reporter:Leigang Li, Qinfen Gu, Ziwei Tang, Xiaowei Chen, Yingbin Tan, Qian Li and Xuebin Yu
Journal of Materials Chemistry A 2013 - vol. 1(Issue 39) pp:NaN12269-12269
Publication Date(Web):2013/08/07
DOI:10.1039/C3TA11988B
Two new derivatives of ammonia borane (AB), 1,2/1,3-di-aminopropane borane (1,2/1,3-TMDAB), were prepared through the coordination reaction between 1,2/1,3-di-aminopropane and BH3–THF, which were then characterized by HR-XRD, FT-IR, 13C and 11B NMR. The crystal structure of 1,3-TMDAB was obtained with a combined technique of HR-XRD data and DFT calculations. 1,3-TMDAB crystallizes in the space group of P212121 (no. 19) with an orthorhombic crystal system and lattice constants of a = 12.6439(8) Å, b = 8.6289(3) Å, c = 7.2322(2) Å, and V = 789.05(3) Å3. Both samples, with a theoretical hydrogen content of 9.8 wt%, were shown to release pure H2 during thermal dehydrogenation, presenting great advantages over AB which releases large amounts of impurities (such as NH3, B2H6 or borazine). Moreover, 1,2/1,3-TMDAB did not foam and showed a faster dehydrogenation rate compared with AB. Our newly synthesized 1,2/1,3-TMDAB may serve as a superior alternative to AB for hydrogen storage and enrich the research field of B–N–H hydrogen storage materials.
Co-reporter:Guanglin Xia, Yingbin Tan, Xiaowei Chen, Zaiping Guo, Huakun Liu and Xuebin Yu
Journal of Materials Chemistry A 2013 - vol. 1(Issue 5) pp:NaN1820-1820
Publication Date(Web):2012/11/30
DOI:10.1039/C2TA00697A
Mixed-metal (Li, Al) amidoborane has been synthesized via mechanical ball milling of ammonia borane with lithium hexahydridoaluminate in different molar ratios. The reversible dehydrogenation properties of the thus-synthesized metallic amidoborane and its mixtures with ammonia borane in different ratios were systematically investigated in comparison with neat ammonia borane (AB). On the basis of thermogravimetric analysis and mass spectrometry results, the thus-synthesized mixed-metal amidoborane was shown to release around 10 wt% hydrogen below 200 °C, with an effective suppression of volatile side products. Furthermore, a synergistic effect between metallic amidoborane and ammonia borane has been identified, which leads to the release of 9 wt% hydrogen with high purity at 120 °C. Additionally, upon treatment with hydrazine in liquid ammonia, the regenerated products from the decomposed Li3AlH6–nAB (n = 4, 5, and 6) composites can release 3.5 wt% hydrogen with high purity, corresponding to an approximate 35%, 30%, and 26% regeneration yield for the post-milled Li3AlH6–nAB (n = 4, 5, and 6) composites, respectively.
Co-reporter:Yingbin Tan, Qinfen Gu, Justin A. Kimpton, Qian Li, Xiaowei Chen, Liuzhang Ouyang, Min Zhu, Dalin Sun and Xuebin Yu
Journal of Materials Chemistry A 2013 - vol. 1(Issue 35) pp:NaN10165-10165
Publication Date(Web):2013/06/10
DOI:10.1039/C3TA11599B
A strategy for establishing Hδ+⋯−δH interactions by the combination of two kinds of H-enriched B–N based hydrides, ammine metal borohydrides (AMBs) and ammonia borane (AB), to achieve superior dehydrogenation properties is reported. Two novel combined complexes: Al(BH4)3·6NH3–4AB and Li2Al(BH4)5(NH3BH3)3·6NH3 were successfully synthesized. Structural analysis revealed that a partial NH3 unit transferred from Al(BH4)3·6NH3 to AB, resulting in the formation of two new phases of Al(BH4)3·5.4NH3 and NH3BH3·0.15NH3 in the Al(BH4)3·6NH3–4AB composite. In contrast, Li2Al(BH4)5(NH3BH3)3·6NH3 formed with a single-phase that was indexed to a cubic unit cell with a refined lattice parameter, a = 23.1220(3) Å. The structure of Li2Al(BH4)5(NH3BH3)3·6NH3 is composed of alternate Li+, [Al(NH3)6]3+ and AB layers stacked along the b-axis as a 3D framework. Compared to the unitary compound, the H-enriched complex system presented a mutual dehydrogenation improvement in terms of a considerable decrease in the dehydrogenation temperature and the preferable suppression of the simultaneous release of by-products; for example, over 11 wt% of hydrogen, with a purity of >98 mol%, can be released from both Al(BH4)3·6NH3–4AB and Li2Al(BH4)5(NH3BH3)3·6NH3 below 120 °C. The significantly improved dehydrogenation in the H-enriched complex system can be attributed to the initial interaction between the AB and an NH3 group (from the AMBs), which results in the balanced B–H and N–H units in the AMBs, thereby leading to a more activated and thorough Hδ+⋯−δH interaction in the composite. Moreover, an ammonia-liquification technique was employed to impregnate the complex system into a hypercrosslinked nano-porous polymer (PSDB) template, resulting in the average particle size of the Al(BH4)3·6NH3–4AB composite to be <5 nm, which enables it to release more than 10 wt% high-pure hydrogen (>99.8 mol%) below 110 °C. These advanced dehydrogenation properties affirm Al(BH4)3·6NH3–4AB and Li2Al(BH4)5(NH3BH3)3·6NH3 as strong candidates for potential hydrogen storage materials.
Co-reporter:Jianmei Huang, Yingbin Tan, Jiahao Su, Qinfen Gu, Radovan Černý, Liuzhang Ouyang, Dalin Sun, Xuebin Yu and Min Zhu
Chemical Communications 2015 - vol. 51(Issue 14) pp:NaN2797-2797
Publication Date(Web):2014/12/11
DOI:10.1039/C4CC09317H
A new metal borohydride ammoniate (MBA), Zr(BH4)4·8NH3, was synthesized via ammoniation of the Zr(BH4)4 crystal. Zr(BH4)4·8NH3 has a distinctive structure and the highest coordination number of NH3 groups among all the known MBAs. This compound could quickly dehydrogenate at 130 °C, enabling it a potential hydrogen storage material.
Co-reporter:Jianmei Huang, Yingbin Tan, Qinfen Gu, Liuzhang Ouyang, Xuebin Yu and Min Zhu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 10) pp:NaN5304-5304
Publication Date(Web):2014/12/18
DOI:10.1039/C4TA05328A
A new complex system, Zr(BH4)4·8NH3–nNH3BH3 (n = 2, 3, 4, 5), was prepared via ball milling of Zr(BH4)4·8NH3 and NH3BH3 (AB). The combination strategy effectively suppressed ammonia release and reduced the dehydrogenation temperature when compared to the individual compounds. In the optimized composition, Zr(BH4)4·8NH3–4AB, the hydrogen purity was improved to 96.1 mol% and 7.0 wt% of hydrogen was released at 100 °C. These remarkable improvements are attributed to the interaction between AB and the NH3 group in Zr(BH4)4·8NH3, which enables a more active interaction of Hδ+⋯−δH. These advanced dehydrogenation properties suggest that Zr(BH4)4·8NH3–4AB is a promising candidate for potential hydrogen storage applications.
Co-reporter:Liang Gao, Yan Hui Guo, Guang Lin Xia and Xue Bin Yu
Journal of Materials Chemistry A 2009 - vol. 19(Issue 42) pp:NaN7829-7829
Publication Date(Web):2009/09/29
DOI:10.1039/B916503G
A new complex material system, Mg(NH3)nCl2–nLiBH4 (here n can be 1, 2 and 6), in which the MgCl2 works as ammonia carrier but plays a crucial role in promoting the interaction between LiBH4 and NH3 to release hydrogen at temperature below 100 °C, is reported.
The synthesis, crystal structure and dehydrogenation performances of two new H-enriched compounds, Mg(BH4)2(NH3BH3)2 and Mg(BH4)2·(NH3)2(NH3BH3), are reported. Due to the introduction of ammonia ligands, the Mg(BH4)2·(NH3)2(NH3BH3) exhibits dramatically improved dehydrogenation properties over its parent compound.
Co-reporter:Zunxian Yang, Guodong Du, Zaiping Guo, Xuebin Yu, Zhixin Chen, Tailiang Guo and Huakun Liu
Journal of Materials Chemistry A 2011 - vol. 21(Issue 24) pp:NaN8596-8596
Publication Date(Web):2011/05/09
DOI:10.1039/C0JM03873C
Novel TiO2(B)@carbon composite nanowires were simply prepared by a two-step hydrothermal process with subsequent heat treatment in argon. The nanostructures exhibit the unique feature of having TiO2(B) encapsulated inside and an amorphous carbon layer coating the outside. The unique core/shell structure and chemical composition is likely to lead to perfect performance in many applications. In this paper, the results of Li-ion battery testing are presented to demonstrate the superior cyclic performance and rate capability of the TiO2(B)@carbon nanowires. The composite nanowires exhibit a high reversible capacity of 560 mAh g−1 after 100 cycles at the current density of 30 mA g−1, and excellent cycling stability and rate capability (200 mAh g−1 when cycled at the current density of 750 mA g−1), indicating that the composite is a promising anode candidate for Li-ion batteries.
This paper reports a complete ammonia borane (AB) regeneration process in which Bu3SnH was utilized as a reductant for the reductive dechlorination of BCl3, and Et2PhN was selected as a ‘helper ligand’ to generate Et2PhN·BH3, which gives rise to a high yield of AB by a base-exchange reaction at ambient temperature.
Co-reporter:Lijun Zhang, Guanglin Xia, Yu Ge, Caiyun Wang, Zaiping Guo, Xingguo Li and Xuebin Yu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 41) pp:NaN20499-20499
Publication Date(Web):2015/08/31
DOI:10.1039/C5TA05540G
Borane–amine adducts (H3N·BH3, AB) in tetrahydrofuran solution were infiltrated into polypyrrole (PPy) nanotubes by a capillary effect, forming an ammonia borane (AB)@PPy combined system. This composite system combines the synergetic catalysis of nitrogen atoms with nanoconfinement in nanotubes, resulting in a significant improvement in the dehydrogenation properties. Dehydrogenation results showed that the AB loaded on PPy can release 15.3% hydrogen below 150 °C with an onset decomposition temperature as low as 48 °C. More importantly, the evolution of harmful ammonia, diborane, and borazine was entirely suppressed.
Co-reporter:Yanhui Guo, Yixiao Jiang, Guanglin Xia and Xuebin Yu
Chemical Communications 2012 - vol. 48(Issue 37) pp:NaN4410-4410
Publication Date(Web):2012/02/29
DOI:10.1039/C2CC30751K
Ammine aluminium borohydride system is found to release >12 wt% pure H2 below 120 °C via a combined strategy of changing the coordination number and adopting mixed cations.
Journal of Materials Chemistry A 2011 - vol. 21(Issue 20) pp:NaN7144-7144
Publication Date(Web):2011/04/04
DOI:10.1039/C0JM04485G
A novel combined hydrogen storage system LiBH4/[C(NH2)3]+[BH4]− (GBH) complexes were reported. By a short time ball milling of LiBH4 and guanidinium chloride, a series of new LiBH4/GBH complexes were produced. It was found that the two potential hydrogen storage materials exhibited a mutual dehydrogenation improvement, releasing >10.0 wt.% of fairly pure H2 from LiBH4/GBH below 250 °C. Further investigations revealed that balancing the protic and hydridic hydrogens, and the complexation between LiBH4 and GBH, are two important roles in the improvement of the dehydrogenation of this system, which may serve as an alternative strategy for developing a new metal borohydride/B–N–H system with favourable dehydrogenation.
Co-reporter:Jie Chen, Guanglin Xia, Zaiping Guo, Zhenguo Huang, Huakun Liu and Xuebin Yu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 31) pp:NaN15848-15848
Publication Date(Web):2015/07/03
DOI:10.1039/C5TA03721B
Porous Ni nanofibers (NFs) were synthesized via a single-nozzle electrospinning technique with subsequent calcination and reduction. The as-prepared continuous Ni NFs, with a uniform diameter of ∼50 nm and porous structure composed of a myriad of Ni nanocrystallites, were adopted to catalyze MgH2. The homogeneous distribution of Ni nanoparticles (NPs), obtained by ball milling Ni NFs with MgH2, on the surface of MgH2 offered effective catalytic sites to significantly enhance the hydrogen storage properties of MgH2. In particular, 4% Ni NF catalyzed MgH2 (MgH2–4% Ni NFs) starts to release hydrogen at only 143 °C, with a peak temperature of 244 °C, 157 °C and 96 °C lower than for MgH2 catalyzed with as-milled 4% Ni powders (MgH2–4% Ni powders), and it dehydrogenates completely within only 11 min at 325 °C (7.02 wt%). Compared with plain MgH2 and MgH2–4% Ni powders, the activation energy of the as-milled MgH2–4% Ni NF composite is significantly decreased to 81.5 kJ mol−1.
Co-reporter:Xiaowei Chen, Yu-Jun Zhao and Xuebin Yu
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 3) pp:NaN900-900
Publication Date(Web):2012/11/19
DOI:10.1039/C2CP43016A
First-principles calculations based on density functional theory were carried out to investigate the formation and migration of native defects in LiNH2BH3. The structural properties and formation energies of H, Li, N and B related defects in various charge states were examined. Our analysis showed that the dominant atomic H defects are positively and negatively charged H interstitial (IH+ and IH−). The Li related defects are dominated by positively charged Li interstitial (ILi+) and negatively charged Li vacancy (VLi−). For N related defects, the energetically favorable defects are positively and negatively charged NH2 interstitial (INH2+ and INH2−), while B related defect is dominated by neutral BH3 interstitial (IBH30). Further results indicated that the neutral H2 interstitial (IH2) has the lowest formation energy (0.31 eV), suggesting that the major defect in LiNH2BH3 is IH2. Investigation of migration processes of the defects showed that the migration barriers for V(B)H+ (positively charged H vacancy on a B–H site), IH+ and IH− are relatively high (0.50–0.68 eV), whereas moderate diffusion barriers are presented for V(N)H− (negatively charged H vacancy on a N–H site) and ILi+ (0.29 and 0.32 eV, respectively). The VLi− and IH2 defects can migrate with low energy barriers of 0.13 and 0.16 eV, respectively. With a low activation energy of 0.47 eV, IH2 is the major diffusive species in LiNH2BH3. Our calculation results further suggest that the creation of the V(N)H−, ILi+ and VLi− defects is the rate-limiting step for their transportation in LiNH2BH3.
Co-reporter:Guanglin Xia, Li Li, Zaiping Guo, Qinfen Gu, Yanhui Guo, Xuebin Yu, Huakun Liu and Zongwen Liu
Journal of Materials Chemistry A 2013 - vol. 1(Issue 2) pp:NaN257-257
Publication Date(Web):2012/09/27
DOI:10.1039/C2TA00195K
In the present work, the decomposition behaviour of NaZn(BH4)3 nanoconfined in mesoporous SBA-15 has been investigated in detail and compared to bulk NaZn(BH4)3 that was ball milled with SBA-15, but not nanoconfined. The successful incorporation of nanoconfined NaZn(BH4)3 into mesopores of SBA-15 was confirmed by scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, 11B nuclear magnetic resonance, nitrogen absorption/desorption isotherms, and Fourier transform infrared spectroscopy measurements. It is demonstrated that the dehydrogenation of the space-confined NaZn(BH4)3 is free of emission of boric by-products, and significantly improved hydrogen release kinetics is also achieved, with pure hydrogen release at temperatures ranging from 50 to 150 °C. By the Arrhenius method, the activation energy for the modified NaZn(BH4)3 was calculated to be only 38.9 kJ mol−1, a reduction of 5.3 kJ mol−1 compared to that of bulk NaZn(BH4)3. This work indicates that nanoconfinement within a mesoporous scaffold is a promising approach towards stabilizing unstable metal borohydrides to achieve hydrogen release with high purity.
Co-reporter:Shaofeng Li, Ziwei Tang, Qiaolong Gong, Xuebin Yu, Paul R. Beaumont and Craig M. Jensen
Journal of Materials Chemistry A 2012 - vol. 22(Issue 39) pp:NaN21023-21023
Publication Date(Web):2012/08/21
DOI:10.1039/C2JM34766K
Novel borohydrides of para- and meta-bis-(ammonium)-benzene (m/p-BABB), possessing theoretical hydrogen storage capacities of 10.1 wt%, have been synthesized upon metathesis of p/m-benzenediamine dihydrochloride (p/m-BDADC) and lithium borohydride through simple ball-milling. It was found that the dehydrogenation of the BABBs proceeds in the temperature range of 50–200 °C via a multistep mechanism similar to that of NH3BH3 and [NH4]+[BH4]−, releasing 8.35 and 6.52 wt% hydrogen from p- and m-BABB, respectively. Solid state 11B MAS NMR studies indicate that the dehydrogenation process of p-BABB and m-BABB follows a pathway similar to that of [NH4]+[BH4]−via [BH2(NH3)2]+[BH4]− (DADB). The residues obtained after releasing ∼6 equiv. H2 are mainly N,N′-phenyl substituted polyborazylenes. The dehydrogenated products can be converted back to N,N′-phenyl substituted ammonia-boranes by treatment with hydrazine sulfate [(N2H4)2·H2SO4] in liquid ammonia (NH3) for one week at 45 °C, demonstrating the potential of this class of material for regenerable chemical hydrogen storage.
Co-reporter:Ziwei Tang, Yingbin Tan, Qinfen Gu and Xuebin Yu
Journal of Materials Chemistry A 2012 - vol. 22(Issue 12) pp:NaN5318-5318
Publication Date(Web):2012/01/05
DOI:10.1039/C2JM14990G
The crystal structure of a promising hydrogen storage material, calcium borohydride monoammoniate (Ca(BH4)2·NH3), is reported. Structural analysis revealed that this compound crystallizes in an orthorhombic structure (space group Pna21) with unit-cell parameters of a = 8.4270 Å, b = 12.0103 Å, c = 5.6922 Å and V = 576.1121 Å3, in which the Ca atom centrally resides in a slightly distorted octahedral environment furnished by five B atoms from BH4 units and one N atom from the NH3 unit. As Ca(BH4)2·NH3 tends to release ammonia rather than hydrogen when heated in argon, a novel aided-cation strategy via combining this compound with LiBH4 was employed to advance its dehydrogenation. It shows that the interaction of the two potential hydrogen storage substances upon heating, based on a promoted recombination reaction of BH and NH groups, enables a significant mutual dehydrogenation improvement beyond them alone, resulting in more than 12 wt% high-pure H2 (>99%) released below 250 °C. The synergetic effect of associating the dihydrogen reaction with mutually aided-metal cations on optimizing the dehydrogenation of this kind of composites may serve as an alternative strategy for developing and expanding the future B–N–H systems with superior and tuneable dehydrogenation properties.
Journal of Materials Chemistry A 2012 - vol. 22(Issue 3) pp:NaN1068-1068
Publication Date(Web):2011/11/15
DOI:10.1039/C1JM13002A
The ammine complex of yttrium borohydride Y(BH4)3·4NH3, which contains a theoretical hydrogen capacity of 11.9 wt.%, has been successfully synthesized via a simple ball milling of YCl3·4NH3 and LiBH4. The structure of Y(BH4)3·4NH3, determined by high resolution powder X-ray diffraction, crystallizes in the orthorhombic space group Pc21n with lattice parameters a = 7.1151(1) Å, b = 11.4192(2) Å, c = 12.2710(2) Å and V = 997.02(2) Å3, in which the dihydrogen bonds with distances in the range of 2.043 to 2.349 Å occurred between the NH3 and BH4− units contribute to the hydrogen liberation via the combination reaction of N–H⋯H–B. Thermal gravimetric analysis combined with mass spectrometer results revealed that the decomposition of Y(BH4)3·4NH3 consists of three steps with peaks at 86 °C, 179 °C and 279 °C, respectively, in which the first and second steps mainly release hydrogen accompanied by a fair amount of ammonia emission, while the third one accounts for a pure hydrogen release. Isothermal dehydrogenation results revealed that over 8.7 wt.% hydrogen was released for Y(BH4)3·4NH3 at 200 °C, which are improved significantly in terms of both capacity and kinetics comparing to Y(BH4)3, in which the hydrogen capacity is only 3.2 wt.% at the same temperature. The favorable dehydrogenation properties presented by the Y(BH4)3·4NH3, i.e., lower dehydrogenation temperature and higher nominal hydrogen contents than that of Y(BH4)3, enable it to be a promising candidate for hydrogen storage. In addition, in situ high resolution X-ray diffraction, differential scanning calorimetry, solid-state 11B nuclear magnetic resonance and Fourier transform infrared spectroscopy measurements were employed to understand the dehydrogenation pathway of Y(BH4)3·4NH3.
Co-reporter:Yingbin Tan, Xiaowei Chen, Jie Chen, Qinfen Gu and Xuebin Yu
Journal of Materials Chemistry A 2014 - vol. 2(Issue 37) pp:NaN15632-15632
Publication Date(Web):2014/07/16
DOI:10.1039/C4TA02842B
The intermolecular interactions of N–H⋯B–H (proton–hydride) have been considered to mediate the release of hydrogen from B–N-based complexes. Mass spectroscopy studies on the thermal decomposition of isotopomer α-LiN2H3BD3, however, indicate that the initial dehydrogenation occurs through a homopolar N–H⋯H–N (proton–proton) pathway, followed by the N–H⋯B–H (proton–hydride) and B–H⋯B–H (hydride–hydride) pathways. The unexpected scission of the N–H bonds prior to B–H bonds can be attributed to the molecular structure of Li[NH2–NH–BH3], in which the detachment of the (N)H atoms results in a significant reduction of the N–N and N–B bond length, hence reducing the (N)H detachment energy. The scission of N–H bonds further facilitates the detachment of the (B)H atom, therefore, promoting the following proton–hydride and hydride–hydride dehydrogenation pathways.
Co-reporter:Zunxian Yang, Qing Meng, Zaiping Guo, Xuebin Yu, Tailiang Guo and Rong Zeng
Journal of Materials Chemistry A 2013 - vol. 1(Issue 35) pp:NaN10402-10402
Publication Date(Web):2013/06/25
DOI:10.1039/C3TA11751K
Highly uniform, relatively large area TiO2/SnO2/carbon hybrid nanofibers were synthesized by a simple method based on thermal pyrolysis and oxidation of an as-spun titanium–tin/polyacrylonitrile nanoweb composite in an argon atmosphere. This novel composite features the uniform dispersion and encapsulation of highly uniform nanoscale TiO2/SnO2 crystals in a porous carbon matrix. The high porosity of the nanofiber composite material, together with the conductive carbon matrix, enhanced the electrochemical performance of the TiO2/SnO2/carbon nanofiber electrode. The TiO2/SnO2/carbon nanofiber electrode displays a reversible capacity of 442.8 mA h g−1 for up to 100 cycles, and exhibits excellent rate capability. The results indicate that the composite could be a promising anode candidate for lithium ion batteries.
![Boron, [m-(hydrazine-kN1:kN2)]hexahydrodi-](http://img.cochemist.com/ccimg/13800/13730-91-1.png)
![Boron, [m-(hydrazine-kN1:kN2)]hexahydrodi-](http://img.cochemist.com/ccimg/13800/13730-91-1_b.png)
