Yingbin Tan

Monodisperse magnesium hydride nanoparticles uniformly self-assembled on graphene.

Monodisperse MgH2 nanoparticles with homogeneous distribution and a high loading percent are developed through hydrogenation-induced self-assembly under the structure-directing role of graphene. Graphene acts not only as a structural support, but also as a space barrier to prevent the growth of MgH2 nanoparticles and as a thermally conductive pathway, leading to outstanding performance.

Structure and decomposition of zinc borohydride ammonia adduct: towards a pure hydrogen release

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) A, b = 8.417(6) A, c = 6.388(4) A 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.

A New Ammine Dual‐Cation (Li, Mg) Borohydride: Synthesis, Structure, and Dehydrogenation Enhancement

A new ammine dual-cation borohydride, LiMg(BH(4))(3)(NH(3))(2), has been successfully synthesized simply by ball-milling of Mg(BH(4))(2) and LiBH(4)·NH(3). Structure analysis of the synthesized LiMg(BH(4))(3)(NH(3))(2) revealed that it crystallized in the space group P6(3) (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 BH(4) units. Strong N-H···H-B dihydrogen bonds exist between the NH(3) and BH(4) units, enabling LiMg(BH(4))(3)(NH(3))(2) to undergo dehydrogenation at a much lower temperature. Dehydrogenation studies have revealed that the LiMg(BH(4))(3)(NH(3))(2)/LiBH(4) composite is able to release over 8 wt% hydrogen below 200 °C, which is comparable to that released by Mg(BH(4))(3)(NH(3))(2). More importantly, it was found that release of the byproduct NH(3) in this system can be completely suppressed by adjusting the ratio of Mg(BH(4))(2) and LiBH(4)·NH(3). This chemical control route highlights a potential method for modifying the dehydrogenation properties of other ammine borohydride systems.

Carbon‐Coated Li3N Nanofibers for Advanced Hydrogen Storage

3D porous carbon-coated Li3 N nanofibers are successfully fabricated via the electrospinning technique. The as-prepared nanofibers exhibit a highly improved hydrogen-sorption performance in terms of both thermodynamics and kinetics. More interestingly, a stable regeneration can be achieved due to the unique structure of the nanofibers, over 10 cycles of H2 sorption at a temperature as low as 250 °C.

A novel aided-cation strategy to advance the dehydrogenation of calcium borohydride monoammoniate

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 A, b = 12.0103 A, c = 5.6922 A and V = 576.1121 A3, 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.

Mixed-metal (Li, Al) amidoborane: synthesis and enhanced hydrogen storage properties

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.

A liquid-based eutectic system: LiBH4·NH3–nNH3BH3 with high dehydrogenation capacity at moderate temperature

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.

Ammonia borane modified zirconium borohydride octaammoniate with enhanced dehydrogenation properties

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.

A synergistic strategy established by the combination of two H-enriched B–N based hydrides towards superior dehydrogenation

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) A. 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 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.

Immobilization of Aluminum Borohydride Hexammoniate in a Nanoporous Polymer Stabilizer for Enhanced Chemical Hydrogen Storage

With global warming and environmentalpollution worsening,thesearchforalternativefuelsisamatterofgreatimportance.Hydrogen is an excellent energy-storage medium because ofits abundance, high chemical energy, and low-emissioncombustion. However, hydrogen remains underutilized asa fuel source because of a lack of storage capacity.