High-capacity LiBH 4 is a promising solid hydrogen storage material. However, the large electron cloud density between the B-H bonds in LiBH 4 induces high dehydrogenation temperatures and sluggish dehydrogenation kinetics. To solve the above problems, it is proposed to enhance the hydrogen storage properties of LiBH 4 through the synergistic effect of Brønsted and Lewis acid in Hβ zeolite. Composite hydrogen storage systems with different mass ratios were prepared by simple ball-milling. At a LiBH 4 -to-Hβ mass ratio of 6:4, the 6LiBH 4 -4Hβ system released hydrogen at 190 °C and achieved a hydrogen release capacity of 7.0 wt% H 2 upon heating to 400 °C. More importantly, the hydrogen release capacity of the system reached 6.02 wt% at 350 °C under isothermal conditions after 100 min and 7.2 wt% at 400 °C under isothermal conditions after 80 min, whereas the pristine LiBH 4 only achieved 2.2 wt%. The improvement in hydrogen storage performance of the system was mainly attributed to two factors: (i) Lewis acid sites with acceptable electrons in the Hβ weaken the electron density of B–H bonds in LiBH 4 , and (ii) the H + proton from the Brønsted acid sites and H − of LiBH 4 undergo a H + + H − = H 2 reaction. Theoretical calculations revealed that the Lewis and Brønsted acid sites in the Hβ zeolite are conducive to the weakening of B – H bonds and that storage charge transfer occurs near the Lewis acid sites. The present work provides new insights into improving the hydrogen storage performance of LiBH 4 by weakening the B–H bonds in the LiBH 4 .
Magnesium borohydride (Mg(BH 4 ) 2 ) is widely regarded as a promising hydrogen storage material due to its high capacity; however, it is still challenging to synthesize Mg(BH 4 ) 2 with low cost. Traditionally, Mg(BH 4 ) 2 has been mainly produced using other borohydride as the starting materials via exchange reactions. Herein, we report an economical method to synthesize Mg(BH 4 ) 2 by converting B-O bonds in widely available borates or boric acid to B-H. The borates or boric acid is ball-milled with MgH 2 under ambient conditions to form Mg(BH 4 ) 2 with high yield (>80%). Mg(BH 4 ) 2 was also successfully generated by reacting low-cost Mg with boric acid. Compared with previous approaches, this method avoids expensive boron sources such as LiBH 4 , NaBH 4 , and B 2 H 6 , and does not require high pressure H 2 gas and high temperatures, and therefore significantly reduces costs. This method could be an alternative to the current Mg(BH 4 ) 2 synthesis processes.
Zichun Ding,Lishuai Zong,Chenghao Wang,Siying Wang,RunZe Liu,Xigao Jian,Jinyan Wang
The current design of phthalonitrile resins has been faced with mutual constraints between heat resistance and functionality. Instead of retaining complex heat-resistant structures in the monomer to ensure thermal performance, this study proposes a new strategy to endow carborane cages with dual identities as curing sites and heat-resistant components by utilizing the σ–π double coordination properties of cyano groups. Through the NMR tracking of the soluble B-stage resin and the XPS test of the stage cured product, it is confirmed that the cyano group was bonded to the B–H bond on the carborane cage at the initial stage of curing. In the later stage of curing, carborane is evenly dispersed in the curing network during the formation of triazine and phthalocyanine rings and becomes an inorganic filler to enhance the temperature resistance of the resin system. By performing TGA on the cured product, the 5% decomposition temperature (Td5%) of the component containing the carborane curing agent was increased by 75 °C up to 582 °C under nitrogen atmosphere. The design of this new carborane curing agent with dual functions before and after curing provides a new idea for improving the comprehensive performance of the phthalonitrile resin system.
Herein, we describe the synthesis of tetraphenylphosphonium o-carboranyl dithiocarboxylate (Ligand 1) and methyldithiocarboxyl-o-carborane (Ligand 2). The complexes [Cp*M(o-C2B10H11CS2)Cl] (M = Ir (3); Rh (4)) and [Cp*M(o-C2B10H11CS2)2] (M = Ir (5); Rh (6)) have been synthesized based on Ligand 1. The selective B–H bond activation of Ligand 2 has also been explored, leading to the synthesis of the B–H activated complex [Cp*Ir(o-C2B10H10CS2CH3)Cl] (7) and four of its substituted derivatives (8, 9, 10 and 11). All of these compounds have been characterised through single-crystal X-ray diffraction, NMR, IR spectroscopy and elemental analysis.
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