Hydrolytic Dehydrogenation Of Ammonia Borane Research Articles

A review on platinum(0) nanocatalysts for hydrogen generation from the hydrolysis of ammonia borane.

This review reports a survey on the progress in developing highly efficient platinum nanocatalysts for the hydrolytic dehydrogenation of ammonia borane (AB). After a short prelude emphasizing the importance of increasing the atom efficiency of high cost, precious platinum nanoparticles (NPs) which are known to be one of the highest activity catalysts for hydrogen generation from the hydrolysis of AB, this article reviews all the available reports on the use of platinum-based catalysts for this hydrolysis reaction covering (i) early tested platinum catalysts, (ii) platinum(0) NPs supported on oxides, (iii) platinum(0) NPs supported on carbonaceous materials, (iv) supported platinum single-atom catalysts, (v) bimetallic- and (vi) multimetallic-platinum NP nanocatalysts, and (vii) magnetically separable platinum-based catalysts. All the reported results are tabulated along with the important parameters used in the platinum-catalyzed hydrolysis of AB. In the section "Concluding remarks and a look towards the future" a discussion is devoted to the approaches for making high cost, precious platinum catalysts as efficient as possible, ultimately lowering the cost, including the suggestions for the future research in this field.

Amorphous Alloy Architectures in Pore Walls: Mesoporous Amorphous NiCoB Alloy Spheres with Controlled Compositions via a Chemical Reduction

Amorphous bimetallic borides are an emerging class of catalytic nanomaterial that has demonstrated excellent catalytic performance due to its glass-like structure, abundant unsaturated active sites, and synergistic electronic effects. However, the creation of mesoporous Earth-abundant bimetallic metal borides with tunable metal proportion remains a challenge. Herein, we develop a sophisticated and controllable dual-reducing agent strategy to synthesize the mesoporous nickel-cobalt boron (NiCoB) amorphous alloy spheres (AASs) with adjustable compositions by using a soft template-directed assembly approach. The selective use of tetrabutylphosphonium bromide (Bu4PBr) is beneficial to generate well-defined mesopores because it both moderates the reduction rate by decreasing the reducibility of M2+ species and prevents the generation of soap bubbles. Our meso-Ni10.0Co74.5B15.5 AASs generate the highest catalytic performance for the hydrolytic dehydrogenation of ammonia borane (AB). Its high performance is attributed to the combination of optimal synergistic effects between Ni, Co, and B as well as the high surface area and the good mass transport efficiency due to the open mesopores. This work describes a systematic approach for the design and synthesis of mesoporous bimetallic borides as efficient catalysts.

Visible-light-enhanced catalytic hydrolysis of ammonia borane using RuP2 quantum dots supported by graphitic carbon nitride

Hydrolytic dehydrogenation of ammonia borane (AB) driven by efficient catalysts has attracted considerable attention and is regarded as a promising strategy for hydrogen generation. Herein, RuP2 quantum dots supported on graphitic carbon nitride (g-C3N4) were successfully prepared by in-situ phosphorization, yielding a highly efficient photocatalyst toward AB hydrolysis. The catalysts were characterized by field-emission scanning electron microscopy, transmission electron microscopy, x-ray diffraction, x-ray photoelectron microscopy, inductively coupled plasma atomic emission spectroscopy, UV–visible diffuse reflectance spectroscopy and photoluminescence spectroscopy. A conventional water-displacement method was employed to record the hydrogen volume as a function of reaction time. Owing to visible-light irradiation, the initial turnover frequency of the AB hydrolysis was significantly enhanced by 110% (i.e., 134 min−1) at room temperature. Furthermore, the apparent activation energy decreased from 67.7 ± 0.9 to 47.6 ± 1.0 kJ mol−1. The photocatalytic hydrolysis mechanism and catalyst reusability were also investigated.

Ketjen Black supported monodisperse nickel–platinum alloy nanoparticles for the efficient catalyst in the hydrolytic dehydrogenation of ammonia borane

In this study, we research the efficiency of the catalysis of Ketjen Black (KB) assembled monodisperse NiPt alloy nanoparticles (NPs) in the hydrolytic dehydrogenation of ammonia borane (AB). Monodisperse NiPt alloy NPs were synthesized by the coreduction of nickel(II) acetate and platinum(II) acetylacetonate with borane tert‐butylamine under gentle conditions. As synthesized NiPt alloy NPs were supported on the KB, reduced graphene oxide (rGO) and mesoporous graphitic carbon nitride (mpg‐C3N4) by liquid‐phase self‐assembly method. The characterization of the presented nanocatalyst was carried out by X‐ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma‐mass spectroscopy (ICP‐MS), and X‐ray photoelectron spectroscopy (XPS) techniques. The catalytic activity of three different supported NiPt alloy NPs was used in the hydrolysis of AB. Among the tested nanocatalysts, KB‐supported NiPt NPs showed high activity and durability in the hydrolytic dehydrogenation of AB. The modified recipe organized to control the composition of NiPt NPs and Ni70Pt30 NPs showed the best catalytic activity with the turnover frequency (TOF) of 1479 min−1. We report the detailed kinetics of KB‐NiPt nanocatalyst depending on AB concentration, catalyst amount, temperature, and reusability. The activation energy of catalytic hydrolysis of AB was calculated to be 25.4 kJ mol−1.

Ultrafine Pd nanoparticles stabilized on magnetic Fe3O4@SiO2-g-C3N4 composites for the hydrolytic dehydrogenation of ammonia borane

The magnetic composites consisting of a porous graphitic carbon nitride (g-C3N4) and the core-shell Fe3O4@SiO2 were facilely prepared. Subsequently, the Pd nanoparticles (NPs) were stabilized on the composites by the in-situ reduction of PdCl2 with sodium borohydride. The mass ratio of Fe3O4@SiO2 to g-C3N4 was optimized in view of the catalytic activity of the corresponding Pd-based catalysts for ammonia borane (AB) hydrolysis. The results showed that the catalyst fabricated with a mass ratio of 1:1 (Fe3O4@SiO2: g-C3N4) displayed the highest catalytic activity. The Pd NPs were mainly distributed in the region of 5.4–9.8 nm in the optimal Pd/Fe3O4@SiO2-g-C3N4 catalyst, which had a specific surface area of 47.5 m2 g−1 and a total pore volume of 0.126 cm3 g−1. Catalyzed by the optimal catalyst, the turnover frequency was 33.7molH2·molPd−1·min−1, and the apparent activation energy was 31.4 kJ mol−1. Also, the recycling experiments indicated that the optimal catalyst still maintained a high catalytic activity even after eight runs. The superior catalytic performance is presumably due to the highly dispersed Pd NPs and the stably porous structure with large specific surface area. The excellent catalytic and magnetic properties endow Pd/Fe3O4@SiO2-g-C3N4 exciting potential in the hydrogenation generation from the hydrolysis of solid hydrogen storage materials.

Pd-doped Cu nanoparticles confined by ZIF-67@ZIF-8 for efficient dehydrogenation of ammonia borane

To exploit the low-cost and efficient catalyst for the hydrolytic dehydrogenation of ammonia borane, trace amount of palladium-doped transition metal (Cu, Ni, Co, Fe and Zn) nanoparticles have been incorporated into the interior of metal-organic frameworks named ZIF-8, ZIF-67, ZIF-67/ZIF-8 and core-shell ZIF-67@ZIF-8 by a double-solvent approach. The optimized catalyst of CuPd0.01@ZIF-67@ZIF-8 composite exhibited an excellent activity with a turnover frequency (TOF) value of 30.15 mol H2 (molmetal)−1 min−1 at 298 K and a relatively low activation energy of 38.78 kJ mol−1. It might attributed to both ultrafine size of metal nanoparticles (~3 nm) induced by the confinement of core-shell ZIF-67@ZIF-8 and the synergistic effect between Pd and Cu. Moreover, the detailed kinetic study has manifested that this catalytic reaction is first-order in regards to the catalyst amount while zero-order as for the concentration of ammonia borane. In addition, the durability and recyclability of CuPd0.01@ZIF-67@ZIF-8 have been demonstrated to be great.

Composition-dependent catalytic activity of bimetallic PtPd dendrimer-encapsulated nanoparticles having an average size of 1.7 nm for hydrolytic dehydrogenation of ammonia borane

We investigated composition-dependent catalytic activity of bimetallic PtPd dendrimer-encapsulated nanoparticles (DENs) that had a uniform size of ∼1.7nm for hydrolytic dehydrogenation of ammonia borane (AB). The PtPd DENs, composed of seven different Pt: Pd ratios, were synthesized using hydroxyl-terminated sixth-generation polyamidoamine dendrimers as a molecular template. The dendrimer-templating method allowed for synthesizing bimetallic PtPd DENs with controllable nanoparticle composition while fixing the size of the nanoparticles uniformly at ∼1.7 nm. Compared with monometallic Pt and Pd DENs, the bimetallic PtPd DENs showed superior catalytic activity for the hydrolytic dehydrogenation of AB. Furthermore, the bimetallic PtPd DENs exhibited composition-dependent activity with the maximum activity (i.e., average turnover frequency=108.5±15.9molH2·molatom Pt+pd−1·min−1) at a Pt: Pd ratio of 1:1 for the catalytic hydrolysis of AB.

Pt Nanoparticles Supported on Mesoporous Graphitic Carbon Nitride as Catalysts for Hydrolytic Dehydrogenation of Ammonia Borane

Platinum (Pt) nanoparticles (NPs) supported on mesoporous graphitic carbon nitride (mpg-CN/Pt) were synthesized in situ via the reduction of as-prepared mpg-CN/Pt(IV) composites during the catalyti...

Highly efficient hydrolysis of ammonia borane using ultrafine bimetallic RuPd nanoalloys encapsulated in porous g-C3N4

The hydrolysis of solid storage compounds including ammonia borane (NH3BH3) is promising for the upcoming hydrogen economy. So, developing highly efficient heterogeneous catalysts for the hydrolysis of ammonia borane is one of the key issues since this reaction is not kinetically feasible at room temperature. In this work, a facile adsorption-in situ reduction method is adopted to stabilize the ultrafine bimetallic RuPd nanoparticles on an ultrathin porous graphite carbon nitride. Due to the synergistic alloying effect, most of the resultant bimetallic Ru1-xPdx/g-C3N4 catalysts possess much higher catalytic activity than the monometallic Ru/g-C3N4 and Pd/g-C3N4 in the hydrolytic dehydrogenation of ammonia borane. Catalyzed by the optimal Ru0.85Pd0.15/g-C3N4, the turnover frequency and the apparent activation energy are 948.2 molH2·molCat-1·min-1 and 24.2 kJ mol−1, respectively, which are much superior to many catalysts previously reported. The high catalytic activity and satisfactory durability endow Ru0.85Pd0.15/g-C3N4 desirable potential in the hydrogen generation from the hydrolysis of chemical storage materials.

Hierarchical Porous g-C3N4 Coupled Ultrafine RuNi Alloys as Extremely Active Catalysts for the Hydrolytic Dehydrogenation of Ammonia Borane

It is a crucial and urgent task to develop high performance catalysts for the hydrolysis of ammonia borane (NH3¬BH3, AB), which is thought to be an effective strategy for the hydrogen generation at...

Co-CoOx supported onto TiO2 coated with carbon as a catalyst for efficient and stable hydrogen generation from ammonia borane

Ammonia borane (AB) can be catalytically hydrolyzed to provide hydrogen at room temperature due to its high potentaial for hydrogen storage. Non-precious metal heterogeneous catalysts have broad application in the field of energy catalysis. In this article, catalysts precursor is obtained from Co-Ti-resorcinol-formaldehyde resin by sol–gel method. Co/TiO2@N-C (CTC) catalyst is prepared by calcining the precursor under high temperature conditions in nitrogen atmosphere. Co-CoOx/TiO2@N-C (COTC) is generated by the controllable oxidation reaction of CTC. The catalyst can effectively promote the release of hydrogen during the hydrolytic dehydrogenation of AB. High hydrogen generation at a specific rate of 5905 mL min−1 gCo−1 is achieved at room temperature. The catalyst retains its 85% initial catalytic activity even for its fifth time use in AB hydrolysis. The synergistic effect among Co, Co3O4 and TiO2 promotes the rate limiting step with dissociation and activation of water molecules by reducing its activation energy. The applied method in this study promotes the development of non-precious metals in catalysis for utilization in clean energy sources.

Rhodium(0), Ruthenium(0) and Palladium(0) nanoparticles supported on carbon-coated iron: Magnetically isolable and reusable catalysts for hydrolytic dehydrogenation of ammonia borane

We report the synthesis of magnetically isolable ruthenium(0), rhodium(0), and palladium(0) nanoparticles, supported on carbon-coated magnetic iron particles, and their employment as catalysts in hydrolysis of ammonia borane. Carbon-coated iron (C–Fe) particles are obtained by co-processing of iron powders with methane in a radio frequency thermal plasma reactor. The impregnation of ruthenium(III), rhodium(III) and palladium(II) ions on the carbon-coated iron particles followed by aqueous solution of sodium borohydride leads to the formation of respective metal(0) nanoparticles supported on carbon-coated iron, M0/C–Fe NP (M = Ru, Rh, and Pd) at room temperature. M0/C–Fe NPs are characterized using the ICP-OES, XPS, TEM, and EDX techniques and tested as catalysts for hydrolysis of ammonia borane at 298 K. The results reveal that Rh0/C–Fe, Ru0/C–Fe, Pd0/C–Fe catalysts provide turnover frequency of 83, 93, and 29 min−1, respectively, in this industrially important reaction. More importantly, these magnetically separable metal(0) nanoparticles show very high reusability with no noticeable activity loss in subsequent runs of hydrolysis evolving 3.0 equivalent H2 per mole of ammonia borane.

Engineering Nickel/Palladium Heterojunctions for Dehydrogenation of Ammonia Borane: Improving the Catalytic Performance with 3D Mesoporous Structures and External Nitrogen-Doped Carbon Layers.

Catalysts based on metallic NPs have shown high activities in heterogeneous catalysis, due to their high fractions of surface-active atoms, which, however, will lead to the sacrifices in stability and recycle of catalysts. In order to balance well the relationship between activity, stability, and recovery, in this paper, we have constructed a 3D mesoporous sphere structure assembled by N-doped carbon coated Ni/Pd NP heterojunctions (Ni/Pd@N-C). This obtained Ni/Pd@N-C has shown high catalytic activity, durability and recyclability for the hydrolytic dehydrogenation of ammonia borane (AB). Further investigations, including experimental and theoretical results, have shown that the unique structural features, the synergistic effect between Ni and Pd, and the coating of N-doped carbon layer are responsible for the good catalytic performance of Ni/Pd@N-C mesoporous spheres.

In situ synthesized hollow spheres of a silica–ruthenium–nickel composite catalyst for the hydrolytic dehydrogenation of ammonia borane

The present study investigated the fabrication of hollow spheres of a silica–ruthenium–nickel composite catalyst for the hydrolitic dehydrogenation of ammonia borane.

Interface electron collaborative migration of Co–Co3O4/carbon dots: Boosting the hydrolytic dehydrogenation of ammonia borane

Ammonia borane (AB) is an excellent candidate for the chemical storage of hydrogen. However, its practical utilization for hydrogen production is hindered by the need for expensive noble-metal-based catalysts. Herein, we report Co–Co 3 O 4 nanoparticles (NPs) facilely deposited on carbon dots (CDs) as a highly efficient, robust, and noble-metal-free catalyst for the hydrolysis of AB. The incorporation of the multi-interfaces between Co, Co 3 O 4 NPs, and CDs endows this hybrid material with excellent catalytic activity ( r B = 6816 m L H 2 min –1 g Co –1 ) exceeding that of previous non-noble-metal NP systems and even that of some noble-metal NP systems. A further mechanistic study suggests that these interfacial interactions can affect the electronic structures of interfacial atoms and provide abundant adsorption sites for AB and water molecules, resulting in a low energy barrier for the activation of reactive molecules and thus substantial improvement of the catalytic rate. The Co–Co 3 O 4 /CDs was proved to be a highly efficient noble-metal-free catalyst for AB hydrolysis. The incorporation of the multi-interfaces between Co, Co 3 O 4 NPs, and CDs endows the hybrid material with excellent catalytic activity.

Surfactant PVA-Stabilized Co–Mo Nanocatalyst Supported by Graphene Oxide Sheets Toward the Hydrolytic Dehydrogenation of Ammonia Borane

By adding surfactant polyvinyl alcohol (PVA) and controlling the preparation process, we successfully synthesized Co–Mo catalysts. For further improving the dispersion, reduced graphene oxide sheets as catalyst carrier were introduced to synthesize Co–Mo@rGO composite catalyst as highly efficient catalysts for hydrolytic dehydrogenation of ammonia borane. The introduction of Mo for preparing Co–Mo@rGO catalyst helped to form alloy catalyst with better structure, better dispersity and smaller particle size. When the molar ratio of Co and Mo was 0.75:0.25, the bimetallic composite catalyst exhibited superior activity with TOF value of 16.29[Formula: see text]mol[Formula: see text]. The activation energy of the reaction was calculated to be 43.72[Formula: see text]kJ[Formula: see text][Formula: see text]. Furthermore, the reusability tests reveal that waxberry-like Co–Mo still show good catalytic activity with 80.3% of their initial activity in five successive runs. The enhanced catalytic activities were due to the synergistic interaction between graphene sheets and waxberry-like Co–Mo NPs, which was beneficial to improve the dispersion and stability of bimetallic NPs. Also, ligand effects on the formation of waxberry-like structure and amorphous state further promoted the catalytic activity.

Synthesis of Pt Nanocatalyst Supported on Halloysite Nanotubes via Strong Electronic Adsorption for Hydrolytic Dehydrogenation of Ammonia Borane

Highly dispersed ultrafine Pt nanoparticles were supported on halloysite nanotubes by a strong electronic adsorption method. The as-prepared nanocatalyst showed excellent catalytic performance with...

Cu0.4Co0.6MoO4 Nanorods Supported on Graphitic Carbon Nitride as a Highly Active Catalyst for the Hydrolytic Dehydrogenation of Ammonia Borane

As a typical chemical hydride, ammonia borane (AB) has received extensive attention because of its safety and high hydrogen storage capacity. The aim of this work was to develop a cost-efficient and highly reactive catalyst for hydrolyzing AB. Herein, we synthesized a series of CuxCo1–xMoO4 dispersed on graphitic carbon nitride (g-C3N4) to dehydrogenate AB. Among those CuxCo1–xMoO4/g-C3N4 catalysts, Cu0.4Co0.6MoO4/g-C3N4 exhibited the highest site time yield (STY) value of 75.7 m o l H 2 m o l c a t − 1 m i n − 1 with a low activation energy of 14.46 kJ mol−1. The STY value for Cu0.4Co0.6MoO4/g-C3N4 was about 4.3 times as high as that for the unsupported Cu0.4Co0.6MoO4, indicating that the g-C3N4 support plays a crucial role in improving the catalytic activity. Considering its low cost and high catalytic activity, our Cu0.4Co0.6MoO4/g-C3N4 catalyst is a strong candidate for AB hydrolysis for hydrogen production in practical applications.

Electrospun Bimetallic NiCr Nanoparticles@Carbon Nanofibers as an Efficient Catalyst for Hydrogen Generation from Ammonia Borane.

In this study, we report on the fabrication and utilization of NiCr alloy nanoparticles (NPs)-decorated carbon nanofibers (CNFs) as efficient and competent non-precious catalysts for the hydrolytic dehydrogenation of ammonia borane (AB) at 25 ± 2 °C. The introduced NFs have been fabricated in one step using a high-temperature thermal decomposition of the prepared electrospun nanofiber mats (nickel acetate tetrahydrate, chromium acetate dimer, and polyvinyl alcohol) in an inert atmosphere. The chemical composition of the NFs with different proportions of Ni1−xCrx (x = 0.0, 0.1, 0.15, 0.2, 0.25, 0.3) was established via standard characterization techniques. These techniques proved the formation of disorder Cr2Ni3 alloy and carbon for all the formulations. The as-synthesized composite NFs exhibited a higher catalytic performance for AB dehydrogenation than that of Cr-free Ni–CNFs. Among all the formulations, the sample composed of 15% Cr shows the best catalytic performance, as more H2 was released in less time. Furthermore, it shows good stability, as it is recyclable with little decline in the catalytic activity after six cycles. It also demonstrates the activation energy, entropy (ΔS), and enthalpy (ΔH) with 37.6 kJ/mole, 0.094 kJ/mole, and 35.03 kJ/mole, respectively. Accordingly, the introduced catalyst has a lower price with higher performance encouraging a practical sustainable H2 energy application from the chemical hydrogen storage materials.

Magnetically separable rhodium nanoparticles as catalysts for releasing hydrogen from the hydrolysis of ammonia borane

Magnetically separable catalysts attract considerable attention in catalysis due to their facile separation from the reaction medium. This propensity is crucial for efficient multiple use of precious noble metal nanoparticles in catalysis. In fact, the isolation of catalysts from the reaction medium by filtration and washing results usually in the loss of huge amount of activity in the subsequent run of catalysis. Although many transition metal nanoparticle catalysts have been reported for the H2 generation from the hydrolysis of ammonia borane, there is no study reporting the magnetically separable rhodium based catalysts for the hydrolytic dehydrogenation of ammonia borane. Here, we report the preparation of rhodium(0) nanoparticles supported on the surface of Fe3O4 and CoFe2O4 magnetic nanopowders as the first example of magnetically separable rhodium nanocatalysts. The resulting magnetically separable Rh0/Fe3O4 and Rh0/CoFe2O4 nanoparticles are highly active, long-lived and reusable catalysts in H2 generation from the hydrolysis of ammonia borane providing a turnover frequency value of 273 and 720 min−1, respectively, at 25.0 ± 0.1 °C. These magnetically separable catalysts show high reusability and long-term stability in the hydrolysis reaction. They retain their complete initial activity even after the 5th use releasing exactly 3.0 equivalent H2 gas per mole of ammonia borane. The long-term stability tests show that Rh0/Fe3O4 and Rh0/CoFe2O4 nanoparticles provide a total turnover number of 125,000 and 245,000, respectively, in releasing H2 from the hydrolysis of ammonia borane at room temperature. The long term stability and reusability of magnetically separable Rh0/Fe3O4 and Rh0/CoFe2O4 nanoparticles make them attractive catalysts for hydrogen generation in fuel cell applications.