Dehydrogenation Of Ammonia Borane Research Articles

Mechanism of complete dehydrogenation of ammonia borane in electrochemical alkaline environment

Ammonia borane (NH3BH3, AB) has been considered to be a promising chemical hydrogen storage material. The dehydrogenation reaction of AB on the surface of MgSiP2 is investigated by the first-principles method. We have verified the two conventional intramolecular dehydrogenation pathways in the AB hydrolysis reaction, B-distal dehydrogenation (the rate-determining step (RDS) was 0.71 eV) and B-N bond dissociation dehydrogenation (the RDS was 1.00 eV). A new reaction route for dehydrogenation, the BN alternate dehydrogenation, was also explored. The reaction heat of the RDS was 0.71 eV. Note that the entire reaction process in the path of the dissociation of the BN bond can completely release the 6H protons in AB. With the help of the dissociation of H2O, the H2 output ratio of 1:6 can be achieved. In addition, we also considered the influence of *OH– on the RDS of each dehydrogenation reaction in alkaline environment. The calculations have found that the presence of *OH– is beneficial to reduce the reaction heat of dehydrogenation in the AB hydrolysis reaction, making the reaction heat of the RDS of B-distal dehydrogenation is changed from 0.71 eV to 0.15 eV, the B-N bond dissociation dehydrogenation is changed from 1.00 eV to 0.09 eV and the BN alternate dehydrogenation is changed from 0.71 eV to 0.15 eV. This shows that *OH– greatly promotes the production of H2 from the dehydrogenation of AB.

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 with free energy barrier of 2.07 and 1.54 eV respectively. Remarkably, the rate constant further quantitatively confirmed the real situation of the first step of dehydrogenation of AB on the Os/P3C and Os/P3C_O substrates. We found that kf1 at 400 K is equivalent to kf2 at 800 K, which greatly improves the temperature of the first step of AB dehydrogenation on P3C_O. We hope this work can provide a promising method for the design of catalysts for AB dehydrogenation reactions on the surface of two-dimensional materials (2D).

Highly dispersed palladium nanoparticles supported on graphitic carbon nitride for selective hydrogenation of nitro compounds and Ullmann coupling reaction

High catalytic activity and superior stability are important criterion for the utilization of a noble metal‐based nano‐composite catalyst. Herein, we report a facile synthesis of highly dispersed palladium nanoparticles embedded on graphitic carbon nitride (Pd@CNx) by ultrasound assisted method without aid of any external reducing agent. The Pd@CNx composite was well characterized by different techniques. This Pd@CNx shows effective catalytic activity towards easy dehydrogenation of sodium borohydride (NaBH4) and ammonia borane in aqueous medium and also can easily hydrogenate 4‐nitrophenol to 4‐aminophenol with fast kinetics. The catalyst is highly selective towards nitro groups in presence of other reducible groups with good stability. Furthermore, the catalyst exhibits superior catalytic activity towards Ullmann coupling reaction of different aryl halides with broad range of substrates scope with easy recovery of the catalyst and notable recycling property.

Unravelling the synergy in platinum-nickel bimetal catalysts designed by atomic layer deposition for efficient hydrolytic dehydrogenation of ammonia borane

Bimetal catalysis has been one of the major categories in heterogeneous catalysis field, and the efficient and durable catalysts can be well achieved by the bimetal synergy. Herein we report a remarkable achievement of both dehydrogenation activity of ammonia borane and durability by controllably engineering Pt-Ni interfacial sites via the Pt and the following NiO atomic layer deposition strategy, which can also realize the controllable synthesis of other Pt-M (M=Co, Cu, Fe and Zn) bimetal catalysts. Multiple characterization techniques, kinetic-isotopic analyses and density functional theory calculations were employed to unravel the nature of the Pt-Ni synergy. Experimental and theoretical results reveal that the decoration of nickel species on the Pt nanoparticles constructing the targeted Pt-Ni interfacial sites could lower the reaction activation energy, promote the adsorption, activation and dissociation of H2O molecules, and facilitate the desorption of hydrogen atoms, resulting in the doubly enhanced activity with a turnover frequency value of 751.6 molH2 molPt-1 min-1 and the remarkably improved durability. Our work offers an alternative and general strategy for the rational design of bimetal catalysts with specific interfacial structure and provides fundamental guidance for in-depth understanding of the bimetal synergy.

Dehydrogenation of ammonia-borane to functionalize neutral and Li+-encapsulated C60, C70 and C36 fullerene cages: a DFT approach.

Mechanistic investigations into the functionalization of three fullerene cages, viz. C60, C70, and C36 through dehydrogenation of ammonia-borane (AB) have been conducted using Density Functional Theory (DFT). In this process of functionalization, different ring fusions, namely (6-6), (6-5) positions for C60 and C70, and an additional (5-5) for C36 fullerene have been investigated. The optimized geometries of all the complexes and transition states have been characterized using the M06-2X functional in conjunction with the 6-31G(d) basis set. The effect of Li+-encapsulation on the energetics and activation barriers of H2 attachment has also been examined. Although the process of functionalization of neutral fullerenes proceeds extensively through concerted pathways, a step-wise route has been observed for the encapsulated systems. NPA charge analysis and Wiberg bond index (WBI) have been used in order to detect the change in the nature of participating hydrogen atoms and validate the variation in the bond order of the C-C connectivity respectively upon hydrogenation. GCRD parameters have also been calculated to explicate the electronic properties of the hydrogenated products. The (6-6) hydrogenation is observed to be favoured thermodynamically and kinetically for both neutral and Li+-encapsulated C60 and C70, while (5-5) is found to be the most preferred site for C36 systems. Our theoretical exploration suggests that the covalent functionalization of the fullerene cages can be done successfully viaAB resulting in the stabilization of these systems. In short, the present work will provide a general idea about the detailed mechanism related to the functionalization of fullerene cages, which will further motivate researchers in fullerene chemistry.

Crystal facet effects of platinum single-atom catalysts in hydrolytic dehydrogenation of ammonia borane

More electron depletion of the Pt center of the Pt1/Co3O4-c surface facilitates overall electron transfer from the B atom to the ammonia borane (AB) molecule, which ensures the highest activity among Pt1/Co3O4-x in the hydrolytic dehydrogenation of AB reaction.

Regulation of Co3o4/Co Hetero-Structures Embedded in N-Doped Porous Carbon as High-Efficient Catalysts for Dehydrogenation of Ammonia Borane

Regulation of Co3o4/Co Hetero-Structures Embedded in N-Doped Porous Carbon as High-Efficient Catalysts for Dehydrogenation of Ammonia Borane

Hydrolytic dehydrogenation of ammonia borane in neat water using recyclable zeolite-supported cyclic alkyl amino carbene (CAAC)–Ru catalysts

Highly effective ammonia borane dehydrogenation was carried out using a heterogenized ruthenium-CAAC complex in water.

The curious saga of dehydrogenation/hydrogenation for chemical hydrogen storage: a mechanistic perspective.

Hydrogen storage is an indispensable component of hydrogen-based fuel economy. Chemical hydrogen storage relies on the development of lightweight compounds which can deliver high weight percentage of H2 at moderate temperatures through dehydrogenation and can be recovered from the dehydrogenated mass by hydrogenation for reuse. In this feature article we primarily discuss the mechanistic underpinnings of the catalytic dehydrogenation of ammonia-borane, a potential candidate for hydrogen storage and the challenges associated with its regeneration from the dehydrogenated mass. Moreover, we highlight the mechanistic intricacies, viability, sustainability and unresolved issues of allied chemical hydrogen storage avenues such as the CH3OH-CO2 cycle.

Cu2O nanoparticle-catalyzed tandem reactions for the synthesis of robust polybenzoxazole.

We report the synthesis of Cu2O nanoparticles (NPs) by controlled oxidation of Cu NPs and the study of these NPs as a robust catalyst for ammonia borane dehydrogenation, nitroarene hydrogenation, and amine/aldehyde condensation into Schiff-base compounds. Upon investigation of the size-dependent catalysis for ammonia borane dehydrogenation and nitroarene hydrogenation using 8-18 nm Cu2O NPs, we found 13 nm Cu2O NPs to be especially active with quantitative conversion of nitro groups to amines. The 13 nm Cu2O NPs also efficiently catalyze tandem reactions of ammonia borane, diisopropoxy-dinitrobenzene, and terephthalaldehyde, leading to a controlled polymerization and the facile synthesis of polybenzoxazole (PBO). The highly pure PBO (Mw = 19 kDa) shows much enhanced chemical stability than the commercial PBO against hydrolysis in boiling water or simulated seawater, demonstrating a great potential of using noble metal-free catalysts for green chemistry synthesis of PBO as a robust lightweight structural material for thermally and mechanically demanding applications.

Cobalt Phosphide with Porous Multishelled Hollow Structure Design Realizing Promoted Ammonia Borane Dehydrogenation: Elucidating Roles of Architectural and Electronic Effect

Cobalt Phosphide with Porous Multishelled Hollow Structure Design Realizing Promoted Ammonia Borane Dehydrogenation: Elucidating Roles of Architectural and Electronic Effect

Alkaline ultrasonic irradiation-mediated boosted H2 production over O/N-rich porous carbon anchored Ru nanoclusters

Developing efficient catalytic systems to boost hydrogen evolution from hydrolytic dehydrogenation of ammonia borane (AB) is of broad interest but remains a formidable challenge since the widespread usages of hydrogen have been considered as sustainable solutions to ensure future energy security. Herein, we developed an alkaline ultrasonic irradiation-mediated catalytic system with O/N-rich porous carbon supported Ru nanoclusters (NCs) (Ru/ONPC) to considerably boost the catalytic activity for hydrogen production from the hydrolytic dehydrogenation of AB. The uniformly distributed sub-2.0 nm Ru NCs on the ONPC were demonstrated to be efficient catalysts to boost hydrogen generation from the hydrolytic dehydrogenation of AB with the synergistic effect between ultrasonic irradiation and alkaline additive without any additional heating. An ultrahigh turnover frequency (TOF) of 4004 min−1 was achieved in the developed catalytic system, which was significantly higher than that of ultrasound-mediated AB hydrolysis without alkali (TOF: 485 min−1) and alkaline AB hydrolysis (TOF: 1747 min−1) without ultrasound mixing. The alkaline ultrasonic irradiation was beneficial for the cleavage of the OH bonds in the attacked H2O molecules catalyzed by the Ru/ONPC and thus considerably boost the catalytic hydrogen generation from AB. This study provides a tractable and ecofriendly pathway to promote the activity toward AB hydrolysis to release hydrogen.

Defective Ehanced Subnano-Rh Catalyst Supported on an Ni@Ni-N-C Substrate for Highly Efficient Hydrolytic Dehydrogenation of Ammonia Borane

Defective Ehanced Subnano-Rh Catalyst Supported on an Ni@Ni-N-C Substrate for Highly Efficient Hydrolytic Dehydrogenation of Ammonia Borane

Solvent-free synthesis of Rh/meso-Al2O3 via mechanochemistry for hydrolytic dehydrogenation of ammonia borane

An effective strategy synthesis of Rh/meso-Al2O3 catalysts was demonstrated by mechanochemistry for hydrolytic dehydrogenation of ammonia borane (AB). These catalysts are characterized systematically by N2 adsorption-desorption isotherms, X-ray diffraction (XRD), X-ray photoelectron spectrometry (XPS), scanning electron microscope (SEM), and transmission electron microscope (TEM). The results show that the turnover frequency (TOF) and activation energy (Ea) are 246.8 molH2·molRh−1·min−1 and 47.9 kJ mol−1 for hydrolytic dehydrogenation of at 298 K catalyzed by Rh/Al2O3-CTAB-400, obviously higher than those previously reported catalysts. Furthermore, catalyst Rh/Al2O3-CTAB-400 can be recycled by simple centrifugal separation and the catalytic activity is still well maintained after five cycles. In addition, a plausible mechanism for hydrolytic dehydrogenation of AB has also been proposed. This mechanochemical synthesis method exhibits great application prospects for the preparation of heterogeneous catalysts.

Dehydrogenation of ammonia borane recrystallized by different techniques

The literature shows that practically no attention has been paid to the size and shape of the particles of bulk ammonia borane (NH 3 BH 3 ). The published results about the influence of the dispersity of this hydride on its dehydrogenation are not numerous and contradictory. This work presents new results on the low-temperature solid-state dehydrogenation of bulk NH 3 BH 3 . The samples under study were recrystallized using different procedures and had, therefore, different particle characteristics. The reactivity of these samples of NH 3 BH 3 was compared on the basis of thermal analysis data obtained under non-isothermal conditions, including the Kissinger kinetics, and H 2 evolution under isothermal conditions (84–96°С) using Avrami-Erofeev kinetics. The finely dispersed sample with a particle size of <40 μm was found to be the most active one. A correlation between the NH 3 BH 3 melting temperature and the temperature of its dehydrogenation has been established. A filamentous NH 3 BH 3 with a length-to-thickness ratio of the filaments of >100 was synthesized and described for the first time. It was suggested that its relatively high reactivity was determined by its ordered structure. These results show the importance of further investigations of bulk ammonia borane with different types of particles. • Effect of dispersity of bulk NH 3 BH 3 (AB) on its dehydrogenation is still contradictory. • AB of different characteristics were prepared by different recrystallization methods. • Мelting temperature of AB correlates with the temperature of its dehydrogenation. • Finely dispersed AB with a particle size of <40 μm is the most active one. • Relatively high activity of non-dispersed but ordered filamentous AB is discussed.

Ammonia-Borane Dehydrogenation Catalyzed by Dual-Mode Proton-Responsive Ir-CNNH Complexes.

Metal complexes incorporating proton-responsive ligands have been proved to be superior catalysts in reactions involving the H2 molecule. In this contribution, a series of IrIII complexes based on lutidine-derived CNNH pincers containing N-heterocyclic carbene and secondary amino NHR [R = Ph (4a), tBu (4b), benzyl (4c)] donors as flanking groups have been synthesized and tested in the dehydrogenation of ammonia–borane (NH3BH3, AB) in the presence of substoichiometric amounts (2.5 equiv) of tBuOK. These preactivated derivatives are efficient catalysts in AB dehydrogenation in THF at room temperature, albeit significantly different reaction rates were observed. Thus, by using 0.4 mol % of 4a, 1.0 equiv of H2 per mole of AB was released in 8.5 min (turnover frequency (TOF50%) = 1875 h–1), while complexes 4b and 4c (0.8 mol %) exhibited lower catalytic activities (TOF50% = 55–60 h–1). 4a is currently the best performing IrIII homogeneous catalyst for AB dehydrogenation. Kinetic rate measurements show a zero-order dependence with respect to AB, and first order with the catalyst in the dehydrogenation with 4a (−d[AB]/dt = k[4a]). Conversely, the reaction with 4b is second order in AB and first order in the catalyst (−d[AB]/dt = k[4b][AB]2). Moreover, the reactions of the derivatives 4a and 4b with an excess of tBuOK (2.5 equiv) have been analyzed through NMR spectroscopy. For the former precursor, formation of the iridate 5 was observed as a result of a double deprotonation at the amine and the NHC pincer arm. In marked contrast, in the case of 4b, a monodeprotonated (at the pincer NHC-arm) species 6 is observed upon reaction with tBuOK. Complex 6 is capable of activating H2 reversibly to yield the trihydride derivative 7. Finally, DFT calculations of the first AB dehydrogenation step catalyzed by 5 has been performed at the DFT//MN15 level of theory in order to get information on the predominant metal–ligand cooperation mode.

Research Progress on Supported Ultrafine Nano-catalysts for Hydrolytic Dehydrogenation of Ammonia Borane

Research Progress on Supported Ultrafine Nano-catalysts for Hydrolytic Dehydrogenation of Ammonia Borane

Binary CuO/TiO2 nanocomposites as high-performance catalysts for tandem hydrogenation of nitroaromatics

In situ hydrogenation of unsaturated compounds by released hydrogen from various hydrogen sources is a good strategy to achieve highly selective hydrogenation. In this work, inexpensive CuO/TiO 2 nanocomposites were systematically screened their performance for catalyzing dehydrogenation of ammonia borane (AB) and the tandem hydrogenation of some nitroaromatics. Those CuO/TiO 2 binary nanocomposites were found to maximize the hydrogen production from the catalytic hydrolysis of AB. Owing to a positive in-situ hydrogen activation, under mild conditions these CuO/TiO 2 nanocomposites exhibited highly excellent reactivities accompanying with better recyclability in the current one-pot hydrogenation. Notably, a selected CuO (0.5) /TiO 2(0.5) nanocomposites displayed high activity and regioselectivity (up to100% yield of aim product) as well as increased ability of inhibiting the dehalogenation reaction, especially for 4-bromonitrobenzene or 4-iodonitrobenzene (up to 71.65% yield for 4-bromoaniline or 68.02% yield of 4-iodoaniline). Moreover, that CuO (0.5) /TiO 2(0.5) nanocomposites from a co-precipitation method displayed relatively better recyclability against those two control samples obtained from a stepwise preparation process. Owing to positive in-situ hydrogen activation mechanism, CuO/TiO 2 binary nanocomposites from co-precipitation method display highly excellent reactivity, regioselectivity, and better recyclability for the tandem hydrogenation of aromatic nitro-compounds under highly mild conditions. • Binary CuO/TiO2 nanocomposites exhibited attractive reactivity toward the tandem hydrogenation of nitro-compounds. • Control experiments powerfully confirm a positive in-situ hydrogen activation benefitting the efficient tandem hydrogenation. • Distinguishable catalytic performances were observed for those catalysts coming from different preparation methods.

Enhanced catalytic performance of cobalt ferrite by a facile reductive treatment for H2 release from ammonia borane

Although magnetic cobalt ferrite (CoFe2O4) has been applied as support to gain magnetically separable nanocomposites for H2 evolution upon the hydrolytic dehydrogenation of ammonia borane (AB), none of them find that only CoFe2O4 could be used as the efficient catalyst for the H2 evolution. Herein, we report a facile reduction strategy to significantly improve the catalytic activity of CoFe2O4 by producing more oxygen vacancies and enhencing surface adsorbed oxygen species. The reduced CoFe2O4 catalyst exhibited superior catalytic activity for H2 evolution upon hydrolytic dehydrogenation of AB, with a TOF of 245 mol(H2)·molcat-1·h−1, whereas the pristine CoFe2O4 does not work. Interestingly the TOF of reduced CoFe2O4 in the H2 evolution increased sharply from 245 to 390 mol(H2)·molcat-1·h−1 in the presence of NaOH. In addition, as-prepared reduced CoFe2O4 has been successfully reused at least 5 cycles without any catalytic activity loss in the hydrolytic dehydrogenation of AB.

Remarkably boosting Ru-Ni nanocatalysis via surface/interface regulation for efficient hydrolytic dehydrogenation of ammonia borane

Ammonia borane (NH3BH3, AB) has been considered as one of the most attractive candidates for chemical hydrogen-storage materials. Development of low-cost and high-performance catalysts for hydrogen generation from AB is highly desirable, which is still a huge challenge. Herein, Ru-Ni bimetallic nanoparticles were fabricated on (3-aminopropyl) triethoxysilane-functionalized reduced graphene oxide nanosheet (APTS-rGO) by a facile one-step in situ co-reduction strategy. The newly developed Ru1Ni4/APTS-rGO catalyst with hydrophilic interface and narrow particle size-distribution presented a remarkably enhanced catalytic activity for hydrolytic H2 generation from AB, affording an ultra-high TOF value of 1559 min−1. The APTS-rGO support was effective to minimize the aggregation of Ru-Ni nanoparticles, achieving the immobilization of ultrasmall Ru-Ni nanoparticles (2.0 nm) on support surface. The change in local charge density of catalyst surface caused by Ru-Ni synergistic effect and metals-support interaction improved the catalytic performance of Ru1Ni4/APTS-rGO. Hydrophilic NH2-containing interface ensured high dispersibility of catalysts in reaction solution, increasing the contact opportunities between active sites and AB molecules. These factors contributed together to the exceptional catalytic performance of Ru1Ni4/APTS-rGO. This catalytic system has potential applications in various catalytic fields due to its obvious advantages of the facile preparation method, good hydrophilicity, and the outstanding catalytic performance.