Efficient catalysis of ammonia borane dehydrogenation

In the presence of an iridium pincer complex, dehydrogenation of ammonia borane (H3NBH3) occurs rapidly at room temperature in tetrahydrofuran to generate 1.0 equivalent of H2 and [NH2BH2]5. A metal borohydride complex has been isolated as a dormant form of the catalyst which can be reactivated by reaction with H2.     

石墨型氮化碳对氨硼烷放氢性能的影响

利用石墨型氮化碳(C₃N₄)和氨硼烷(NH₃BH₃,AB)球磨制备了AB-C₃N₄体系,发现C₃N₄的加入使AB放氢反应温度明显降低,但是副产物氨气浓度有所升高. 因此,利用LiBH₄改性的C₃N₄(LC₃N₄)同AB球磨合成出了AB-LC₃N₄体系,并采用X射线衍射、程序升温脱附-质谱联用、热重-差热分析及核磁共振等技术考察了该体系的脱氢性能. 结果表明,由于LC₃N₄的加入,AB的放氢反应温度明显降低,放氢反应速率加快,放氢诱导期缩短,同时抑制了副产物无机苯的生成. 另外,C₃N₄的化学修饰也降低了AB-LC₃N₄放氢过程中生成氨气的浓度. 动力学分析和核磁共振结果表明,AB-LC₃N₄分解过程依然遵循NH₃BH₂NH₃BH₄诱导的氨硼烷自分解机理.     

Solid-state NMR study of Li-assisted dehydrogenation of ammonia borane

The mechanism of thermochemical dehydrogenation of the 1:3 mixture of Li(3)AlH(6) and NH(3)BH(3) (AB) has been studied by the extensive use of solid-state NMR spectroscopy and theoretical calculations. The activation energy for the dehydrogenation is estimated to be 110 kJ mol(-1), which is lower than for pristine AB (184 kJ mol(-1)). The major hydrogen release from the mixture occurs at 60 and 72 °C, which compares favorably with pristine AB and related hydrogen storage materials, such as lithium amidoborane (LiNH(2)BH(3), LiAB). The NMR studies suggest that Li(3)AlH(6) improves the dehydrogenation kinetics of AB by forming an intermediate compound (LiAB)(x)(AB)(1-x). A part of AB in the mixture transforms into LiAB to form this intermediate, which accelerates the subsequent formation of branched polyaminoborane species and further release of hydrogen. The detailed reaction mechanism, in particular the role of lithium, revealed in the present study highlights new opportunities for using ammonia borane and its derivatives as hydrogen storage materials.     

Tetraglyme-mediated synthesis of Pd nanoparticles for dehydrogenation of ammonia borane

Palladium nanoparticles (PdNPs) were conveniently prepared in tetraglyme (TG) solution using a variety of palladium precursors. At 140 °C, TG promoted Pd(3)(OAc)(6) to produce irregular shaped PdNPs with an average size of 4 nm. When these PdNPs were re-dispersed in TG and used for the dehydrogenation of ammonia borane (AB) at 85 °C, remarkably enhanced catalytic performance was achieved to release 2.3 equiv. of H(2) in 1 h.     

Amineborane-based chemical hydrogen storage: enhanced ammonia borane dehydrogenation in ionic liquids

Ionic liquids are shown to provide advantageous media for amineborane-based chemical hydrogen storage systems. Both the extent and rate of hydrogen release from ammonia borane dehydrogenation are significantly increased at 85, 90, and 95 degrees C when the reactions are carried out in 1-butyl-3-methylimidazolium chloride compared to analogous solid-state reactions. NMR studies in conjunction with DFT/GIAO chemical shift calculations indicate that both polyaminoborane and the diammoniate of diborane, [(NH3)2BH2+]BH4-, are initial products in the reactions.     

Graphene oxide based recyclable dehydrogenation of ammonia borane within a hybrid nanostructure

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 H(2) 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.     

Ruthenium deposited on MCM-41 as efficient catalyst for hydrolytic dehydrogenation of ammonia borane and methylamine borane

Ultrafine Ru nanoparticles are successfully deposited on MCM-41 by using a simple liquid impregnationreduction method, and further investigated for catalytic hydrolysis of ammonia borane and methylamine borane. Among all the catalysts tested, 1.12 wt% Ru/MCM-41 exhibits the highest catalytic activity, with turnover frequency value of 288 min^-1.     

A robust, air-stable, reusable ruthenium catalyst for dehydrogenation of ammonia borane

We describe an efficient homogeneous ruthenium catalyst for the dehydrogenation of ammonia borane (AB). This catalyst liberates more than 2 equiv of H(2) and up to 4.6 system wt % H(2) from concentrated AB suspensions under air. Importantly, this catalyst is robust, delivering several cycles of dehydrogenation at high [AB] without loss of catalytic activity, even with exposure to air and water.     

Synthesis of Ni-Ru alloy nanoparticles and their high catalytic activity in dehydrogenation of ammonia borane

We report the synthesis and characterization of new Ni(x)Ru(1-x) (x = 0.56-0.74) alloy nanoparticles (NPs) and their catalytic activity for hydrogen release in the ammonia borane hydrolysis process. The alloy NPs were obtained by wet-chemistry method using a rapid lithium triethylborohydride reduction of Ni(2+) and Ru(3+) precursors in oleylamine. The nature of each alloy sample was fully characterized by TEM, XRD, energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). We found that the as-prepared Ni-Ru alloy NPs exhibited exceptional catalytic activity for the ammonia borane hydrolysis reaction for hydrogen release. All Ni-Ru alloy NPs, and in particular the Ni(0.74)Ru(0.26) sample, outperform the activity of similar size monometallic Ni and Ru NPs, and even of Ni@Ru core-shell NPs. The hydrolysis activation energy for the Ni(0.74)Ru(0.26) alloy catalyst was measured to be approximately 37?kJ?mol(-1). This value is considerably lower than the values measured for monometallic Ni (≈70?kJ?mol(-1)) and Ru NPs (≈49?kJ?mol(-1)), and for Ni@Ru (≈44?kJ?mol(-1)), and is also lower than the values of most noble-metal-containing bimetallic NPs reported in the literature. Thus, a remarkable improvement of catalytic activity of Ru in the dehydrogenation of ammonia borane was obtained by alloying Ru with a Ni, which is a relatively cheap metal.     

An efficient single atom catalysts Os/P3C sheet for ammonia borane dehydrogenation

Ammonia borane （NH₃BH₃, AB） has been considered to be a promising chemical hydrogen storage material. Based on density functional theory, a series of transition metal atoms supported P₃C （P₃C＿O） sheet is systematically investigated to screen out the most promising catalyst for dehydrogenation of AB. The results indicate that the Os/P₃C and Os/P₃C＿O could be an efficient single atom catalyst （SACs） and the stepwise reaction pathway...     

Anomalous metastable hcp Ni nanocatalyst induced by non-metal N doping enables promoted ammonia borane dehydrogenation

Developing high-performing non-noble transition metal catalysts for H₂ evolution from chemical hydrogen storage materials is of great significance for the hydrogen economy system, yet challenging. Herein,we present for the first time that anomalous metastable hexagonal close-packed Ni nanoparticles induced by heteroatom N doping encapsulated in carbon(N-hcp-Ni/C) can exhibit admirable catalytic performance for ammonia borane(AB) dehydrogenation, prominently outperforming conventional ...     

A DFT investigation of the potential of porous cages for the catalysis of ammonia borane dehydrogenation

Full DFT based quantum mechanical studies reveal that zero dimensional porous structures, especially the newly proposed phosphorus incorporated organic cages, can be excellent catalysts for the dehydrogenation of ammonia borane.     

Reductive amination using ammonia borane

A variety of primary, secondary, and tertiary amines were prepared in 84-95% yields using ammonia borane for the reductive amination of aldehydes and ketones in the presence of titanium isopropoxide.     

Ruthenium-catalyzed dehydrogenation of ammonia boranes

The dehydrogenation of ammonia borane (AB) and methylammonia borane (MeAB) is shown to be catalyzed by several Ru-amido complexes. Up to 1 equiv of H2 (1.0 system wt %) is released from AB by as little as 0.03 mol % Ru within 5 min, and up to 2 equiv of H2 (3.0 system wt %) are released from MeAB with 0.5 mol % Ru in under 10 min at room temperature, the first equivalent emerging within 10 s. Also, a mixture of AB/MeAB yields up to 3.6 system wt % H2 within 1 h with 0.1 mol % Ru. Computational studies were performed to elucidate the mechanism of dehydrogenation of AB. Finally, it was shown that alkylamine-boranes can serve as a source of H2 in the Ru-catalyzed reduction of ketones and imines.