Hydrolytic Dehydrogenation Of Ammonia Borane Research Articles

Two-dimensional molybdenum boride coordinating with ruthenium nanoparticles to boost hydrogen generation from hydrolytic dehydrogenation of ammonia borane

The coordination between carrier and active metal is critical to the catalytic efficiency of ammonia borane (AB) hydrolysis reaction. In the present study, we report a new type of catalytic support based on molybdenum boride (MBene) MoAl1-xB and demonstrate that the effective combination of MoAl1-xB with Ru nanoparticles can realize the significantly enhanced performance for hydrogen generation. Owing to the efficient activation and dissociation of reactants, the optimal Ru/MoAl1-xB catalyst achieves the large turnover frequency of 494 molH2 molRu-1 min−1, high hydrogen generation rate of 119817 mL min−1 gRu-1 and favorable apparent activation energy of 39.2 kJ mol−1 for the catalytic hydrolysis of AB under alkaline-free condition. The isotopic test suggests the cleavage of OH bond in H2O is the rate-determining step for hydrolysis reaction, while the fracture of B–H bond in AB is also well revealed by attenuated total reflectance (ATR)-Fourier transform infrared (FTIR) spectroscopy. Significantly, the flexible on-demand hydrogen generation is achieved by using chemical switches for on–off AB hydrolysis. This study provides a new support platform based on two-dimensional MBene to exploit efficient catalysts to boost AB dehydrogenation.

Exploring Enhanced Hydrolytic Dehydrogenation of Ammonia Borane with Porous Graphene-Supported Platinum Catalysts.

Graphene is a good support for immobilizing catalysts, due to its large theoretical specific surface area and high electric conductivity. Solid chemical converted graphene, in a form with multiple layers, decreases the practical specific surface area. Building pores in graphene can increase specific surface area and provide anchor sites for catalysts. In this study, we have prepared porous graphene (PG) via the process of equilibrium precipitation followed by carbothermal reduction of ZnO. During the equilibrium precipitation process, hydrolyzed N,N-dimethylformamide sluggishly generates hydroxyl groups which transform Zn2+ into amorphous ZnO nanodots anchored on reduced graphene oxide. After carbothermal reduction of zinc oxide, micropores are formed in PG. When the Zn2+ feeding amount is 0.12 mmol, the average size of the Pt nanoparticles on PG in the catalyst is 7.25 nm. The resulting Pt/PG exhibited the highest turnover frequency of 511.6 min-1 for ammonia borane hydrolysis, which is 2.43 times that for Pt on graphene without the addition of Zn2+. Therefore, PG treated via equilibrium precipitation and subsequent carbothermal reduction can serve as an effective support for the catalytic hydrolysis of ammonia borane.

Ultrafine Ni-MoOx Nanoparticles Anchored on Nitrogen-Doped Carbon Nanosheets: A Highly Efficient Noble-Metal-Free Catalyst for Ammonia Borane Hydrolysis.

The development of low-cost and high-efficiency catalysts for the hydrolytic dehydrogenation of ammonia borane (AB, NH3BH3) is still a challenging technology. Herein, ultrafine MoOx-doped Ni nanoparticles (~3.0 nm) were anchored on g-C3N4@glucose-derived nitrogen-doped carbon nanosheets via a phosphate-mediated method. The strong adsorption of phosphate-mediated nitrogen-doped carbon nanosheets (PNCS) for metal ions is a key factor for the preparation of ultrasmall Ni nanoparticles (NPs). Notably, the alkaline environment formed by the reduction of metal ions removes the phosphate from the PNCS surface to generate P-free (P)NCS so that the phosphate does not participate in the subsequent catalytic reaction. The synthesized Ni-MoOx/(P)NCS catalysts exhibited outstanding catalytic properties for the hydrolysis of AB, with a high turnover frequency (TOF) value of up to 85.7 min-1, comparable to the most efficient noble-metal-free catalysts and commercial Pt/C catalyst ever reported for catalytic hydrogen production from AB hydrolysis. The superior performance of Ni-MoOx/(P)NCS can be ascribed to its well-dispersed ultrafine metal NPs, abundant surface basic sites, and electron-rich nickel species induced by strong electronic interactions between Ni-MoOx and (P)NCS. The strategy of combining multiple modification measures adopted in this study provides new insights into the development of economical and high-efficiency noble-metal-free catalysts for energy catalysis applications.

CoNi Nanoparticles Supported on Hierarchical SAPO-34 Zeolite as a Catalyst for the Hydrolytic Dehydrogenation of Ammonia Borane

CoNi Nanoparticles Supported on Hierarchical SAPO-34 Zeolite as a Catalyst for the Hydrolytic Dehydrogenation of Ammonia Borane

An evidence for electron transfer of hydrolytic dehydrogenation of ammonia borane over ruthenium ultra-fine nanoparticles

Hydrogen production from ammonia-borane hydrolysis has been widely studied for its high efficiency and many catalytic mechanisms with different viewpoints have been proposed. However, no attention has been paid to electron transfer during catalytic reactions to form H2 in these catalytic mechanisms. In the present contribution, we propose two possible electron transfer pathways for hydrogen production from AB hydrolysis, which were validated by hydrogen evolution reaction (HER) tests. The electrochemical characterization correlates with the AB hydrolysis test results, where Ru4/Fe–N–C catalyst has the largest active surface area and the smallest charge transfer resistance, along with the largest turnover frequency (298.7 molH2 molRu−1 min−1). These results indicate that Ru4/Fe–N–C catalyst not only provides the adsorption/desorption sites but also provides an effective approach for electron transfer in hydrogen production from AB hydrolysis.

Reducible tungsten(VI) oxide-supported ruthenium(0) nanoparticles: highly active catalyst for hydrolytic dehydrogenation of ammonia borane.

Reducible WO3 powder with a mean diameter of 100 nm is used as support to stabilize ruthenium(0) nanoparticles. Ruthenium(0) nanoparticles are obtained by NaBH4 reduction of ruthenium(III) precursor on the surface of WO3 support at room temperature. Ruthenium(0) nanoparticles are uniformly dispersed on the surface of tungsten(VI) oxide. The obtained Ru0/WO3 nanoparticles are found to be active catalysts in hydrolytic dehydrogenation of ammonia borane. The turnover frequency (TOF) values of the Ru0/WO3 nanocatalysts with the metal loading of 1.0%, 2.0%, and 3.0% wt. Ru are 122, 106, and 83 min-1, respectively, in releasing hydrogen gas from the hydrolysis of ammonia borane at 25.0 °C. As the Ru0/WO3 (1.0% wt. Ru) nanocatalyst with an average particle size of 2.6 nm provides the highest activity among them, it is extensively investigated. Although the Ru0/WO3 (1.0% wt. Ru) nanocatalyst is not magnetically separable, it has extremely high reusability in the hydrolysis reaction as it preserves 100% of initial catalytic activity even after the 5th run of hydrolysis. The high activity and reusability of Ru0/WO3 (1.0% wt. Ru) nanocatalyst are attributed to the favorable metal-support interaction between the ruthenium(0) nanoparticles and the reducible tungsten(VI) oxide. The high catalytic activity and high stability of Ru0/WO3 nanoparticles increase the catalytic efficiency of precious ruthenium in hydrolytic dehydrogenation of ammonia borane.

MCM-41 supported NiPCeOx nanoparticles as highly efficient non-noble metal catalyst for hydrolytic dehydrogenation of ammonia borane

Efficient and controllable hydrogen release from ammonia borane (NH3BH3, AB) hydrolysis is a secure and effective way to generate hydrogen on-demand. The development of high-efficiency and low-cost catalysts is of important but still remains a great challenge. Herein, uniformly dispersed NiPCeOx nanoparticles (NPs) with narrow size distribution supported on mesoporous MCM-41 were prepared by incipient wetness impregnation followed by NaBH4 reduction. Attributing to the ordered mesoporous structure of the support as well as the efficiently enhancement of electron density on the Ni active sites brought by the electron transfers, the NiPCeOx/MCM-41 catalyst exhibits exceptional catalytic performance towards AB hydrolysis with a high turnover frequency (TOF) value of 47.3 molH2(molNi·min)−1 at 298 K and a low apparent activation energy (Ea) of 35.86 kJ mol−1. Furthermore, the NiPCeOx/MCM-41 catalyst shows excellent durability with 76.5% of the initial TOF value remained after five cycles.

Rational 3D Structure of Monolithic Catalysts for Enhanced Hydrolytic Dehydrogenation of Ammonia Borane

Monolithic catalysts have irreplaceable advantages in hydrogen (H2) production through catalytic dehydrogenation from liquid-phase hydrogen storage materials. However, monolithic catalysts suffer from an inevitable reduction in accessible active sites due to the reduced specific surface area and hindered mass transfer. Therefore, a rational three-dimensional (3D) structure of monolithic catalysts is needed to adjust the structural factors for maximizing performance. Herein, a series of efficient and low-cost 3D catalysts with designed periodic structures were successfully fabricated. Due to the optimized specific surface area and bubble transport of the elaborate 3D structure, compared to the disordered foam structure, the new series of monolithic catalysts showed 2.3- and 1.6-fold improvement in overall catalytic performance at 298 and 318 K without any change in physiochemical characteristics, with hydrogen generation rates of 2548 and 3885 mL gcat–1 min–1, respectively. In addition, a three-period structural design philosophy for 3D catalysts was summarized, and the concept of surface activity was introduced to provide quantifiable criteria for guidance of structural optimization. The outcomes in this paper may open up new insights for building high-efficiency monolithic catalysts.

Increasing the catalytic efficiency of rhodium(0) nanoparticles in hydrolytic dehydrogenation of ammonia borane

It reviews the papers reporting on the use of rhodium nanocatalysts in hydrogen generation from the hydrolysis of ammonia borane in the following groups: (i) water soluble rhodium complexes, (ii) colloidal nanoparticles of rhodium, (iii) rhodium(0) nanoparticles supported on carbonaceous materials such as activated carbon, graphene, carbon nanotubes, (iv) the use of oxide supports for rhodium(0) nanoparticles, (v) the use of magnetic powders as support for rhodium(0) nanoparticles to make them magnetically recoverable. In each group, the reported results are evaluated by considering the increase in the catalytic activity (specifically measured in turnover frequency), the stability and durability, the lifetime (that is, how long the nanocatalyst can be used in releasing hydrogen gas from the hydrolysis of ammonia borane at appreciable rate), reusability (that is, how many times the catalyst can be isolated and reused for the same hydrolysis reaction generating hydrogen at acceptable rate). Overall, the work reported in each of the papers is evaluated in terms of contribution to the catalytic efficiency of rhodium nanocatalysts in hydrogen generation from the hydrolysis of ammonia borane at room temperature. At the end, conclusions and suggestions are given how to increase the overall catalytic efficacy of the precious rhodium nanocatalysts in hydrolytic dehydrogenation of ammonia borane.

A facile preparation of graphene hydrogel-supported bimetallic RuM (M: Co, Ni, Cu) nanoparticles as catalysts in the hydrogen generation from ammonia borane

Abstract The synthesis of ultrafine well-dispersed bimetallic RuM (M: Co, Ni, Cu) nanoparticles (NPs) supported on graphene hydrogel (GH) was accomplished by a novel one-pot wet-chemical protocol that comprised the hydrothermal reduction of the mixture of graphene oxide and metal precursors by ethylene glycol (EG) in a Teflon-coated stainless-steel reactor at 180 °C. In this study, for the first time, we report the synthesis of bimetallic RuM NPs anchored on GH during the hydrothermal production of GH from graphene oxide (GH-RuM) and the catalysis of the yielded GH-Ru in the hydrolysis of ammonia borane (AB). As-synthesized GH-RuM (M: Co, Ni, Cu) nanocatalysts were characterized by using many advanced instrumental techniques including TEM, XRD, XPS, and ICP-MS. The bimetallic catalysts denoted as GH-Ru20Co80, GH-Ru30Ni70 and GH-Ru10Cu90 exhibited much higher catalytic activity compared to their Ru, Co, Ni and Cu monometallic counterparts in the hydrolytic dehydrogenation of AB. The catalytic performance of as-prepared NPs in terms of hydrogen generation rate (HGR) was achieved in the order of RuCo > RuNi > RuCu and the highest HGR calculated for the catalyst GH-Ru20Co80 reached 8911.5 mL H2 gcat −1 min−1 at room temperature with an activation energy of 52.5 kJ mol−1.

Waste-biomass-derived activated carbon supported Co-Cu-P nanocatalysts for hydrolytic dehydrogenation of ammonia borane.

Hydrolytic dehydrogenation of ammonia borane is a significant and promising approach for on-site hydrogen production at ambient conditions, and developing highly efficient and low-cost catalysts has attracted considerable attention. Herein, waste-biomass-derived activated carbon (AC) was prepared by hydrothermal carbonization and alkali-assisted activation, and non-precious bimetal phosphides (Co-Cu-P) nanocatalysts with a series of different Co/Cu ratios were synthesized on the AC surface through in situ phosphidation method. Owing to the synergetic effects, the optimal Co0.8Cu0.2P/AC presents an outstanding turnover frequency of 26.5 min-1 (25 °C), which is much higher than that of many reported catalysts. The reaction activation energy was measured to be 34.6 kJ mol-1. Benefiting from the ferromagnetic nature of the phosphides, the Co0.8Cu0.2P/AC can be magnetically separated and reused again. After recycling six times, the catalyst still retains 72% of the initial activity, thus indicating great potential for practical applications.

In situ encapsulating cobalt phosphide into a quasi-MOF: a high-performance catalyst for hydrolytic dehydrogenation of ammonia borane

The development of efficient, durable and economical catalysts based on non-precious metals for the controllable and fast hydrogen evolution from chemical hydrogen storage materials is highly desirable for the hydrogen economy.

Synergistic catalysis over Ni/ZrOx for hydrogen production from hydrolysis of ammonia borane

The Ni/ZrOx-500 catalyst with a suitable metal–support interaction exhibited efficient hydrogen generation for hydrolytic dehydrogenation of ammonia borane.

The doped Co on Rh/Ni@Ni–N–C that weakened the catalytic performance for ammonia borane hydrolysis

Alloy catalyst has been widely studied and used for hydrolytic dehydrogenation of ammonia borane (NH3BH3, AB) with excellent catalytic performance due to the synergistic effect of bimetal. Herein, a series of Rh1-xCox/Ni@Ni–N–C catalysts were prepared by an impregnation reduction method. The optimized Rh0.75Co0.25/Ni@Ni–N–C catalyst exhibited good catalytic performance with turnover frequency of 223.08 molH2 molcat−1 min−1 at 303 K, but decreased the catalytic performance compared with Rh/Ni@Ni–N–C. According to the XPS and Raman analysis, the RhCo alloy nanoparticles could be loaded at the defect position of Ni@Ni–N–C, and the Co nanoparticles occupied the intercalation between Rh and the defective site of the carrier, which could weaken the catalytic activity of AB hydrolysis. Based on the above research, we proposed the catalytic mechanism of the activation of the RhCo–H species. This work provides a new strategy for designing alloy-supported nano-catalysts.

Tuning Fe doping Co/CoOx amorphous nanofilms to enhance the hydrolytic activity towards ammonia borane

Hydrolytic dehydrogenation of ammonia borane (AB) has attracted much attention due to its high hydrogen content and stability. Therefore, the design and construction of low-cost and high-performance catalysts for AB hydrolysis are of great significance. In this work, Co/CoFeOx-X (X is the additional content of Fe precursor) bimetallic oxide nanofilms having an amorphous structure were prepared on an (IL)/water interface for the hydrolysis of AB. Strategies including the rapid addition of metal precursors and variation of Co/Fe atom ratios were employed to induce an amorphous structure for inhibiting the rearrangement of the formed metal nuclei and optimizing the alloying effect on the IL/water interface. This ultrathin amorphous nanofilm structure can expose more metal active sites. Moreover, the electronic interaction between Fe and Co after doping Fe into the Co/CoOx nanofilms facilitates the adsorption and activation for AB and H2O molecules. As a result, the optimized Co/CoFeOx-25 catalyst exhibits excellent catalytic activity with a turnover frequency (TOF) value of 12.25 molH2·molCo–1·min–1, which is considerably higher than that of the monometallic Co/CoOx catalyst. This enhanced activity can be ascribed to the morphology advantages and the electronic effect of Fe and Co on the Co/CoFeOx-25 catalyst. This work provides a promising method to design the highly efficient non-noble metal catalysts for the hydrolysis of chemical hydrides.

Solid-state mechanochemical synthesis of Rh/Al2O3 catalysts for effective hydrolysis of ammonia borane

Aluminium oxide (Al2O3) is a promising catalyst support due to its excellent stability, high specific surface area, low price, and wide applicability. At present, most of the synthesis methods of Al2O3 are wet chemical process, and the solid-state synthesis of catalysts is underdeveloped under solvent-free conditions. In this study, we proposed a novel strategy for solvent-free synthesis of Rh/Al2O3 catalysts via mechanochemistry. The pore properties of the catalysts can be tuned by simply adjusting the amount of template CTAB and calcination temperatures. As a proof of concept, as-prepared catalysts are used to catalyze hydrolytic dehydrogenation of ammonia borane. The best catalyst Rh/Al2O3-CTAB(0.4)-500 achieves a total turnover frequency of 186.0 molH2·molRh−1·min−1 at 298 K and the activation energy is 44.8 kJ·mol−1. It also exhibits good cycling properties for catalyzing the hydrolysis of ammonia borane completely even after five runs. The catalysts were also characterized by various methods, including SEM, TEM, XPS, XRD, etc., to study the relationship between their structure and catalytic performance. The results show that the high activity of the catalyst is closely related to its large BET specific surface area and appropriate average pore size.

AuPt alloy nanoparticles supported on graphitic carbon nitride: In situ synthesis and superb catalytic performance in the light-assisted hydrolytic dehydrogenation of ammonia borane

Addressed herein is the enhancement of catalytic activity of Pt-based nanocatalysts in the hydrolysis of ammonia borane (AB) via in-situ synthesis of bimetallic AuPt alloy nanoparticles (NPs) supported on graphitic carbon nitride (gCN). The presented in-situ synthesis protocol yielded gCN/AuxPt100-x (x = 0, 8, 15, 33) nanocatalysts with highly dispersed AuxPt100-x NPs having the average particle sizes varied in the range of 1.6–2.6 nm over the gCN nanosheets. The generated gCN/Pt92Au8 (600.3 mol H2 mol Pt−1 min−1) and gCN/Pt85Au15 (587.1 mol H2 mol Pt−1 min−1) nanocatalysts showed higher catalytic activity compared to gCN/Pt100 (525.7 mol H2 mol Pt−1 min−1) under white-light irradiation, attributed to the synergistic effects aroused in the AuPt alloy NPs and heterojunctions formed between gCN and AuPt alloy NPs. The detailed characterization of photophysical properties of gCN/AuxPt100-x nanocatalysts revealed that their boosted catalytic activity is attributed to the improved charge kinetics, higher light absorption, and effective electron transfer channels from gCN to the bimetallic AuPt alloy NPs. The role of photogenerated carriers in the photocatalytic AB dehydrogenation was also elucidated via scavenger studies. This study shows that gCN/AuxPt100-x nanocatalysts can be prepared in situ during the hydrolysis of AB at room temperature and the yielded nanocatalysts have a significant role in boosting the hydrogen production from the light-assisted hydrolysis of AB.

Palladium nanoparticles supported on cobalt(II,III) oxide nanocatalyst: High reusability and outstanding catalytic activity in hydrolytic dehydrogenation of ammonia borane

A new palladium(0) nanocatalyst is developed to enhance the catalytic efficiency of precious metal catalysts in hydrogen generation from the hydrolytic dehydrogenation of ammonia borane. Magnetically separable Pd0/Co3O4 nanocatalyst can readily be obtained by the reduction of palladium(II) cations impregnated on cobalt(II, III) oxide at room temperature. The obtained Pd0/Co3O4 nanocatalyst with 0.25% wt. palladium loading has outstanding catalytic activity with a record turnover frequency of 3048 min−1 in the releasing H2 from the hydrolysis of ammonia borane at 25.0 °C. They also provide outstanding reusability even after the tenth run of the hydrolysis of ammonia borane at 25.0 °C. The high activity and superb stability of magnetically isolable Pd0/Co3O4 nanoparticles are attributed to the favorable interaction of palladium with the surface of reducible cobalt oxide.

CuO–Ru0.3@Co3O4 nanocomposites act as a tandem catalyst for dehydrogenation of ammonia borane and hydrogenation of nitrobenezene

The development of catalysts with high activity for tandem reaction are all the ways pursued by chemists. Herein, CuO–Ru0.3@Co3O4 has been synthesized and used as efficient tandem catalyst to promote the release of hydrogen from hydrolytic dehydrogenation of ammonia borane (AB) to catalyze the hydrogenation of nitrobenezenes (NBs). The catalyst exhibits the TOF of 29.87 min−1 and provides the apparent activation energy of 45.2 kJ mol−1 for the hydrolytic dehydrogenation of AB. Additionally, benefited from the magnetic separation capability, up to 99% of its initial catalytic activity is retained after four catalytic cycles.

Intrinsic size‐dependent activity of Pt nanoparticles without masking by heterogeneous oxidation states of Pt for hydrolytic dehydrogenation of NH 3 BH 3

We report size-dependent activity of Pt nanoparticles for hydrolytic dehydrogenation of ammonia borane (AB, NH3BH3) in the size range of 1 to 4 nm without masking by heterogeneous oxidation states of Pt. Specifically, we synthesized five differently sized Pt nanoparticles encapsulated inside generation 6 poly(amidoamine) dendrimers with a uniform oxidation state of Pt in an effort to study the intrinsic size effect of Pt nanoparticles on their catalysis. The five differently sized Pt nanoparticles exhibited significant catalytic activity for hydrolytic dehydrogenation of AB under mild conditions. Interestingly, we found that the catalytic activity of the Pt nanoparticles encapsulated inside dendrimers was tunable even with the subnanometer changes in the sizes of Pt nanoparticles in the range of small sizes less than 4 nm. In particular, the Pt nanoparticle with a mean size of 2.5 nm exhibited the highest catalytic activity with a turnover frequency value of 242.3 ± 7.1 mol H 2 molPt−1 min−1 for hydrogen generation from the hydrolysis of AB at 25°C. The size-dependent activity of Pt nanoparticles was attributed to be geometric in nature, primarily due to the square face Pt atoms as the dominant active sites for the hydrolytic dehydrogenation of AB. Novelty Statement We report size-dependent activity of Pt nanoparticles in the size range of 1 to 4 nm for hydrolytic dehydrogenation of NH3BH3. We synthesized five differently sized Pt nanoparticles, which were encapsulated inside dendrimers, with a uniform oxidation state of Pt in an effort to study the intrinsic size effect of Pt nanoparticles on their catalytic activity without masking by heterogeneous oxidation states of Pt catalysts. The five differently sized Pt nanoparticles exhibited significant catalytic activity for the dehydrogenation of NH3BH3 under mild conditions.