Hydrolysis of ammonia borane as a hydrogen source: fundamental issues and potential solutions towards implementation

Dual Catalytic Activity of Pd-Dispersed MOF for Ammonia-Free Hydrogen Generation from Ammonia Borane and Sodium Borohydride in Aqueous and Methanol Solvents

The development of effective catalysts for hydrogen (H2) generation from chemical hydrides is essential for advancing hydrogen-based energy technologies. Herein, we synthesized a Pd-dispersed CPO-27 catalyst exhibiting exceptional performance for hydrolysis of two boron-based chemical hydrides, i.e., ammonia borane (AB) and sodium borohydride (SB). The catalyst demonstrated activation energies of 22.7 and 18.12 kJ mol-1 for AB and SB hydrolysis respectively, confirming its proficient catalytic activity. To comprehensively understand the factors influencing the production of H2, we systematically investigated the effects of the two hydrides and catalyst concentrations on H2 evolution rates. Additionally, kinetic isotope effect studies were conducted to determine the rate-determining step of hydrolysis reactions. The Pd@MOF catalyst can efficiently capture released ammonia during AB hydrolysis, addressing a major limitation of this process. Notably, the Pd@MOF catalyst demonstrated its catalytic compatibility with methanol solvent too, exploring its applicability in various reaction environments. Overall, our study highlights the capability of the Pd@MOF catalyst toward H2 release from diverse complex hydrides in different solvent systems for H2 generation in clean energy applications.

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.

Synergetic effect of Au nanoparticles and transition metal phosphides for enhanced hydrogen evolution from ammonia-borane

The hydrogen evolution from ammonia borane is intriguing but challenging due to its sluggish kinetics. In this regard, the gold nanoparticles amalgamation with metal phosphides is speculated to be more efficient catalysts. Here, the catalysts Au/Ni₂P and Au/CoP with the high synergetic effect of Au nanoparticles and metal phosphides were synthesized for ammonia borane hydrolysis. The activity of Au/Ni₂P increases 4.8-fold (i.e., 0.08 to 0.40 L∙h^-1) compared to pristine Ni₂P, and the activity of Au/CoP increases 1.7-fold (i.e., 0.74 to 1.27 L∙h^-1) compared to pristine CoP. This reveals that the synergetic effect of Au^δ+ and (Ni₂P) ^δ- is stronger than Au^δ+ and (CoP) ^δ- which is manifested by XPS analysis. The kinetics exposes that the activation energy of Au/Ni₂P (45.28 kJ∙mole^-1) is greater than Au/CoP (31.45 kJ∙mole^-1) and the TOF of Au/Ni₂P is less than Au/CoP. This research work presents an effective approach for producing active sites of Au^δ+ and (Ni₂P & CoP) ^δ- for ammonia borane hydrolysis to enhance the H₂ evolution rate.

Water State-Driven Catalytic Hydrolysis of Ammonia Borane on Cu3P-Carbon Dot-Cu Composite

Hydrogen production from ammonia borane (AB) is usually governed by water activation, which is not only energy-intensive but also requires expensive and complicated catalysts. We here propose an integrated photocatalytic-photothermal system that dramatically improves water activation and lowers the transport resistance of H₂ by means of intermediate state water evaporation. This system is constructed by covering nanocomposites (Cu₃P-carbon dots-Cu) upon vertically aligned acetate fibers (VAAFs). As a result of superior hydration effect of VAAFs and local photothermal heating for rapid water evaporation, its hydrogen production efficiency from AB hydrolysis reaches over 10 times the particulate suspension system under solar irradiation. Mechanism analysis reveals that the rapid vaporization of intermediate water promotes the cleavages of O-H bonds in bound water and the adsorption reaction of AB and water molecules at active sites. Therefore, this work provides a novel approach to optimize catalytic reaction in thermodynamics and kinetics for the hydrolysis of AB.

Rapid nanocatalytic reaction using antibody-conjugated gold nanoparticles for simple and sensitive detection of parathyroid hormone

Biomolecule-conjugated metal nanoparticles (NPs) have been primarily used as colorimetric labels in affinity-based bioassays for point-of-care testing. A facile electrochemical detection scheme using a rapid nanocatalytic reaction of a metal NP label is required to achieve more quantitative and sensitive point-of-care testing. Moreover, all the involved components should be stable in their dried form and solution. This study developed a stable component set that allows for rapid and simple nanocatalytic reactions combined with electrochemical detection and applied it for the sensitive detection of parathyroid hormone (PTH). The component set consists of an indium-tin oxide (ITO) electrode, ferrocenemethanol (FcMeOH), antibody-conjugated Au NPs, and ammonia borane (AB). Despite being a strong reducing agent, AB is selected because it is stable in its dried form and solution. The slow direct reaction between FcMeOH⁺ and AB provides a low electrochemical background, and the rapid nanocatalytic reaction allows for a high electrochemical signal. Under optimal conditions, PTH could be quantified in a wide range of concentrations in artificial serum, with a detection limit of ~0.5 pg/mL. Clinical validation of the developed PTH immunosensor using real serum samples indicates that this novel electrochemical detection scheme is promising for quantitative and sensitive immunoassays for point-of-care testing.

Ultrafine Pt nanoparticles anchored on core-shell structured zeolite-carbon for efficient catalysis of hydrogen generation

Ammonia borane (AB) is a potential hydrogen storage material with high-efficiency hydrolytic dehydrogenation under a suitable catalyst. Noble metal catalysts have drawn a lot of attention. In this study, a carbon-coated zeolite was obtained by calcination at high temperatures using glucose as a carbon source. Pt nanoparticles were fixed on a core-shell composite support by a simple chemical reduction method. A series of catalysts were prepared with different synthesis parameters. The results show that PSC-2 has excellent catalytic performance for hydrolytic dehydrogenation of AB in alkaline solution at room temperature, and the turnover frequency (TOF) is 593 min-1. The excellent catalytic performance is attributed to the carbon layer on the zeolite surface which inhibits the aggregation or deformation of metals in the catalytic reaction. The metal-support interaction activates the water and accelerates the rate-limiting step of hydrolysis. The activation energy (E a = 44 kJ mol-1) was calculated based on the reaction temperature. In addition, the kinetics of AB hydrolysis was studied, and the effects of catalyst concentration, AB concentration and NaOH concentration on AB hydrolysis rate were further investigated. The high-efficiency catalyst prepared in this work provides a new strategy for the development of chemical hydrogen production in the field of catalysis.

Broadband Plasmonic NbN Photocatalysts for Enhanced Hydrogen Generation from Ammonia Borane under Visible-Near-Infrared Illumination

The superior light-harvesting ability of plasmonic metallic nanostructures makes them uniquely suitable for applications in the light-driven chemical transformations relevant to renewable fuels. Here we demonstrate the use of niobium nitride (NbN) nanostructures as a nonprecious plasmonic photocatalyst for the highly efficient H₂ generation from the hydrolytic decomposition of ammonia borane (AB). Porous nanostructured NbN with a hierarchical flower-like nanoarchitecture was synthesized to achieve strong broadband plasmonic absorption in the visible and near-infrared (NIR) regions. The plasmonic NbN absorbers, when loaded with an optimized amount (∼2 wt %) of nanoparticulate Ni as the catalytic centers, show notably enhanced activity toward AB decomposition for H₂ evolution under both visible and NIR illumination, with the reaction rates being 4.6 (>420 nm) and 2.7 (>780 nm) times higher than that of the dark reaction. Further kinetic measurements and mechanistic investigations reveal that the photocatalytic activity originates from the plasmonic hot-carrier contributions.

Hydrolysis of Ammonia Borane on a Single Pt Atom Supported by N-Doped Graphene

The hydrolysis of ammonia borane (NH₃BH₃ or AB) at room temperature is a promising method to produce hydrogen, but the complete reaction mechanism is still less investigated. Herein, the full hydrolysis process of the AB molecule on single Pt atom coordinated by two carbon atoms and one nitrogen atom (Pt₁-C₂N₁) on nitrogen doped graphene is investigated using the density functional theory (DFT) method. Our results demonstrate that the rate-limiting step is the formation of *BH₂NH₃ by breaking the first B-H bond in AB with an energy barrier of 0.68 eV, implying that Pt₁-C₂N₁ is a potential room-temperature catalyst for the full hydrolysis of AB. In addition, 27 more types of M₁-C₂N₁ (M represents transiton metal atom) and Pt₁ supported on nitrogen-doped graphene with different local coordination environments (Pt₁-C_xN_y, x and y are the number of carbon and nitrogen atoms that coordinated with the platinum atom) are considered to screen out potential single-atom catalysts for AB hydrolysis. The screening results further show that Pt₁-C₁N₂ is another potential catalyst for AB hydrolysis. In particular, two hydrogen atoms precovered on Pt₁-C₁N₂, resulting in a lower energy barrier for the rate-limiting step than that on Pt₁-C₂N₁. This study provides a prototype of Pt₁-C₁N₂ and Pt₁-C₂N₁ for catalytic full hydrolysis of AB at room temperature.

Magnetically Isolable Pt0/Co3O4 Nanocatalysts: Outstanding Catalytic Activity and High Reusability in Hydrolytic Dehydrogenation of Ammonia Borane

The development of a new platinum nanocatalyst to maximize the catalytic efficiency of the precious noble metal catalyst in releasing hydrogen from ammonia borane (AB) is reported. Platinum(0) nanoparticles are impregnated on a reducible cobalt(II,III) oxide surface, forming magnetically isolable Pt⁰/Co₃O₄ nanocatalysts, which have (i) superb catalytic activity providing a record turnover frequency (TOF) of 4366 min^-1 for hydrogen evolution from the hydrolysis of AB at room temperature and (ii) excellent reusability, retaining the complete catalytic activity even after the 10th run of hydrolysis reaction. The outstanding activity and stability of the catalyst can be ascribed to the strong interaction between the platinum(0) nanoparticles and reducible cobalt oxide, which is supported by the results of XPS analysis. Pt⁰/Co₃O₄ exhibits the highest TOF among the reported platinum-nanocatalysts developed for hydrogen generation from the hydrolysis of AB.

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.

Cobalt ferrite supported platinum nanoparticles: Superb catalytic activity and outstanding reusability in hydrogen generation from the hydrolysis of ammonia borane

In this work, platinum(0) nanoparticles are deposited on the surface of magnetic cobalt ferrite forming magnetically separable Pt⁰/CoFe₂O₄ nanoparticles, which are efficient catalysts in H₂ generation from the hydrolysis of ammonia borane. Catalytic activity of Pt⁰/CoFe₂O₄ nanoparticles decreases with the increasing platinum loading, parallel to the average particle size. Pt⁰/CoFe₂O₄ (0.23% wt. Pt) nanoparticles have an average diameter of 2.30 ± 0.47 nm and show an extraordinary turnover frequency of 3628 min^-1 in releasing 3.0 equivalent H₂ per mole of ammonia borane from the hydrolysis at 25.0 °C. Moreover, the magnetically separable Pt⁰/CoFe₂O₄ nanoparticles possess high reusability retaining 100% of their initial catalytic activity even after ten runs of hydrolysis. The superb catalytic activity and outstanding reusability make the Pt⁰/CoFe₂O₄ nanoparticles very attractive catalysts for the hydrogen generation systems in portable and stationary fuel cell applications.

Formation of a Key Intermediate Complex Species in Catalytic Hydrolysis of NH3BH3 by Bimetal Clusters: Metal-Dihydride and Boron-Multihydroxy

The hydrolysis of AB (AB, NH₃BH₃) with the help of transition metal catalysts has been identified as one of the promising strategies for the dehydrogenation in numerous experiments. Although great progress has been achieved in experiments, evaluation of the B-N bond cleavage channel as well as the hydrogen transfer channel has not been performed to gain a deep understanding of the kinetic route. Based on the density functional theory (DFT) calculation, we presented a clear mechanistic study on the hydrolytic reaction of AB by choosing the smallest NiCu cluster as a catalyst model. Two attacking types of water molecules were considered for the hydrolytic reaction of AB: stepwise and simultaneous adsorption on the catalyst. The Ni and Cu metal atoms play the distinctive roles in catalytic activity, i.e., Ni atom takes reactions for the H₂O decomposition with the formation of [OH]⁻ group whereas Cu atom takes reactions for the hydride transfer with the formation of metal-dihydride complex. The formation of Cu-dihydride and B-multihydroxy complex is the prerequisite for the effectively hydrolytic dehydrogenation of AB. By analyzing the maximum barrier height of the pathways which determines the kinetic rates, we found that the hydride hydrogen transferring rather than the N-B bond breaking is responsible to the experimentally measured activation energy barrier.

Cu@Pd/C with Controllable Pd Dispersion as a Highly Efficient Catalyst for Hydrogen Evolution from Ammonia Borane

A series of Cu@Pd/C with different Pd contents was prepared using the galvanic reduction method to disperse Pd on the surface of Cu nanoparticles on Cu/C. The dispersion of Pd was regulated by the Cu(I) on the surface, which was introduced by pulse oxidation. The Cu₂O did not react during the galvanic reduction process and restricted the Pd atoms to a specific area. The pulse oxidation method was demonstrated to be an effective process to control the oxidization degree of Cu on Cu/C and then to govern the dispersion of Pd. The catalysts were characterized by transmission electron microscopy (TEM), high-resolution transmission electron microscope (HRTEM), high angular annular dark field scanning TEM (HAADF-STEM), energy-dispersive spectroscopy (EDS) mapping, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), auger electron spectroscopy (AES), and inductively coupled plasma optical emission spectrometer (ICP-OES), which were used to catalyze the hydrogen evolution from ammonia borane. The Cu@Pd/C had much higher activity than the PdCu/C, which was prepared by the impregnation method. The TOF increased as the Cu₂O in Cu/C used for the preparation of Cu@Pd/C increased, and the maximum TOF was 465 mol_H2 min^-1 mol_Pd^-1 at 298 K on Cu@Pd_0.5/C-640 (0.5 wt % of Pd, 640 mL of air was pulsed during the preparation of Cu/C-640). The activity could be maintained in five continuous processes, showing the strong stability of the catalysts.

Synergistic Pt-WO3 Dual Active Sites to Boost Hydrogen Production from Ammonia Borane

Development of synergistic heterogeneous catalysts with active sites working cooperatively has been a pursuit of chemists. Herein, we report for the first time the fabrication and manipulation of Pt-WO₃ dual-active-sites to boost hydrogen generation from ammonia borane. A combination of DFT calculations, structural characterization, and kinetic (isotopic) analysis reveals that Pt and WO₃ act as the active sites for ammonia borane and H₂O activation, respectively. A trade-off between the promoting effect of WO₃ and the negative effect of decreased Pt binding energy contributes to a volcano-shaped activity, and Pt/CNT-5W delivers a 4-fold increased activity of 710.1 mol_H2·mol_Pt^-1·min^-1. Moreover, WO₃ is suggested to simultaneously act as the sacrificial site that can divert B-containing by-products away from Pt sites against deactivation, yielding an increase from 24% to 68% of the initial activity after five cycles. The strategy demonstrated here could shed a new light on the design and manipulation of dual-active-site catalysts.

Hydrolytic dehydrogenation of NH3BH3 catalyzed by ruthenium nanoparticles supported on magnesium–aluminum layered double-hydroxides

Ammonia borane (AB, NH₃BH₃) with extremely high hydrogen content (19.6 wt%) is considered to be one of the most promising chemical hydrides for storing hydrogen. According to the starting materials of AB and H₂O, a hydrogen capacity of 7.8 wt% is achieved for the AB hydrolytic dehydrogenation system with the presence of a highly efficient catalyst. In this work, ruthenium nanoparticles supported on magnesium–aluminum layered double hydroxides (Ru/MgAl-LDHs) were successfully synthesized via a simple method, i.e., chemical reduction. The effect of Mg/Al molar ratios in MgAl-LDHs on the catalytic performance for AB hydrolytic dehydrogenation was systematically investigated. Catalyzed by the as-synthesized Ru/Mg₁Al₁-LDHs catalyst, it took about 130 s at room temperature to complete the hydrolysis reaction of AB, which achieved a rate of hydrogen production of about 740 ml s⁻¹ g⁻¹. Furthermore, a relatively high activity (TOF = 137.1 mol_H2 mol_Ru⁻¹ min⁻¹), low activation energy (E_a = 30.8 kJ mol⁻¹) and fairly good recyclability of the Ru/Mg₁Al₁-LDHs catalyst in ten cycles were achieved toward AB hydrolysis for hydrogen generation. More importantly, the mechanism of AB hydrolysis catalyzed by Ru/MgAl-LDHs was simulated via density functional theory. The facile preparation and high catalytic performance of Ru/MgAl-LDHs make it an efficient catalyst for hydrolytic dehydrogenation of AB.

Ru/MgAl-LDHs catalyst was successfully prepared, which exhibited higher catalytic activity and lower activation energy toward the hydrolysis of ammonia borane for hydrogen production.

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.

A MOF-derived CuCo(O)@ carbon–nitrogen framework as an efficient synergistic catalyst for the hydrolysis of ammonia borane

A CuCo(O)-embedded nitrogen-enriched porous carbon framework catalyst derived from doped metal–organic frameworks for efficient hydrolysis of ammonia borane.

Monodisperse nanoparticles for catalysis and nanomedicine

The growth and breadth of nanoparticle (NP) research now encompasses many scientific and technologic fields, which has driven the want to control NP dimensions, structures and properties. Recent advances in NP synthesis, especially in solution phase synthesis, and characterization have made it possible to tune NP sizes and shapes to optimize NP properties for various applications. In this review, we summarize the general concepts of using solution phase chemistry to control NP nucleation and growth for the formation of monodisperse NPs with polyhedral, cubic, octahedral, rod, or wire shapes and complex multicomponent heterostructures. Using some representative examples, we demonstrate how to use these monodisperse NPs to tune and optimize NP catalysis of some important energy conversion reactions, such as the oxygen reduction reaction, electrochemical carbon dioxide reduction, and cascade dehydrogenation/hydrogenation for the formation of functional organic compounds under greener chemical reaction conditions. Monodisperse NPs with controlled surface chemistry, morphologies and magnetic properties also show great potential for use in biomedicine. We highlight how monodisperse iron oxide NPs are made biocompatible and target-specific for biomedical imaging, sensing and therapeutic applications. We intend to provide readers some concrete evidence that monodisperse NPs have been established to serve as successful model systems for understanding structure-property relationships at the nanoscale and further to show great potential for advanced nanotechnological applications.

Single-walled carbon nanotube supported Pt-Ru bimetallic superb nanocatalyst for the hydrogen generation from the methanolysis of methylamine-borane at mild conditions

Several metal nanoparticle based catalysts have been synthesized for catalyzing the hydrogen production process by hydrolysis of methylamine-borane (MeAB). However, there was only one study that catalyzes the producing of hydrogenvia the methanolysis of MeAB, and it was carried out by our research group. For this reason, in this work, a new catalyst system entitled by single-walled carbon nanotube (SWCNT) supported bimetallic platinum-ruthenium nanoparticles were developed and called as PtRu@SWCNT. These NPs were characterized by several techniques (XRD, XPS, Raman, and TEM), and they were performed for the methanolysis of MeAB with high catalytic activity. The prepared PtRu@SWCNT NPs were also tested in the methanolysis of MeAB at different parameters including different temperatures, catalyst and substrate concentrations, and reusability performance. Experimental results revealed that the new PtRu@SWCNT NPs had excellent catalytic activity and reusability for removing of hydrogen from the methanolysis of MeAB at ambient conditions. According to the obtained data, the turnover frequency is 136.25 mole H₂/mole PtRu × min, and the activation energy (Ea) is 17.29 kJ/mole. More than 99% of conversion was observed at room temperature.

Ultra-small Rh nanoparticles supported on WO3-x nanowires as efficient catalysts for visible-light-enhanced hydrogen evolution from ammonia borane

Hydrolysis of ammonia borane (AB) is a safe and convenient means of H₂ production when efficient catalysts are used. Here we report a facile one-pot solvothermal method to synthesize Rh/WO_3-x hybrid nanowires. Ultra-small Rh nanoparticles with an average size of ∼1.7 nm were tightly anchored on WO_3-x nanowires. Rh/WO_3-x catalysts exhibited substantially enhanced activity for hydrolytic dehydrogenation of AB under both dark and visible light irradiation conditions relative to mixed Rh nanoparticles and WO_3-x nanowires (Rh + WO_3-x ), and Rh/C and WO_3-x nanowires. X-ray photoelectron spectroscopy (XPS) analysis indicated that the synergistic effect between Rh nanoparticles and WO_3-x nanowires was responsible for such an enhancement in activity. Specifically, Rh/WO_3-x achieved the highest turnover frequency (TOF) with a value of 805.0 mol_H2 mol_Rh ^-1 min^-1 at room temperature under visible light irradiation. The H₂ release rate as a function of reaction time exhibited a volcano plot under visible light irradiation, indicating that a self-activation process occurred in the hydrolytic dehydrogenation of AB due to additional oxygen vacancies arising from in situ reduction of WO_3-x nanowires by AB, and thus an enhanced localized surface plasmon resonance (LSPR). Such a self-activation process was responsible for the enhanced catalytic activity under visible light irradiation relative to that under dark conditions, which was supported by the lower activation energy (45.2 vs. 50.5 kJ mol^-1). In addition, Rh/WO_3-x catalysts were relatively stable with only little loss in activity after five cycles due to the tight attachment between two components.

Ex situ synthesis and characterization of a polymer-carbon nanotube-based hybrid nanocatalyst with one of the highest catalytic activities and stabilities for the hydrolytic dehydrogenation of hydrazine-borane at room temperature conditions

In this study, a facile ex situ synthesis of a polyaniline-multiwalled carbon nanotube-based Pt nanocatalyst (Pt@PANI-MWCNT) with an average particle size of 3.18 ± 0.12 nm was performed successfully. The obtained Pt@PANI-MWCNT nanocatalysts were isolated from the solution medium by centrifugation and then were characterized by spectroscopy and microscopy methods. The characterization studies showed that the prepared Pt nanoparticles were formed on PANI-MWCNT surface, and H₂ evolution was obtained by the dehydrogenation of hydrazine-borane in water as a model reaction under room temperature conditions, with the help of the synthesized nanocatalyst. It was observed that the Pt@PANI-MWCNT nanocatalyst had a very high catalytic activity for the hydrolytic dehydrogenation of hydrazine-borane and generated 2.95 mol of H₂ for 1 mol of hydrazine-borane. The initial turn-over frequency (TOF_initial) value of the prepared nanocatalyst for the model reaction at room temperature conditions was found to be 168.5 min^-1. The calculations for the kinetics of the hydrolytic dehydrogenation reaction showed that the hydrazine-borane catalytic reaction kinetics are first order, with respect to the catalyst concentration; several activation parameters, such as entropy (ΔS^#, _app = -72.11 ± 3 J/mol K), enthalpy (ΔH^#, _app = 43.5 ± 2 kJ/mol) and activation energy (E_a,app = 45.5 ± 2 kJ/mol), of the catalytic reaction with the Pt@PANI-MWCNT nanocatalyst were calculated using these kinetic data.

Iron Catalyzed Dehydrocoupling of Amine- and Phosphine-Boranes

Catalytic dehydrocoupling methodologies, whereby dihydrogen is released from a substrate (or intermolecularly from two substrates) is a mild and efficient method to construct main group element-main group element bonds, the products of which can be used in advanced materials, and also for the development of hydrogen storage materials. With growing interest in the potential of compounds such as ammonia-borane to act as hydrogen storage materials which contain a high weight% of H2, along with the current heightened interest in base metal catalyzed processes, this review covers recent developments in amine and phosphine dehydrocoupling catalyzed by iron complexes. The complexes employed, products formed and mechanistic proposals will be discussed.

Fabrication of hollow silica–nickel particles for the hydrolytic dehydrogenation of ammonia borane using rape pollen templates

Hollow silica–nickel particles were fabricated by coating silica–nickel shell on rape pollen templates following calcination.

On-demand Hydrogen Production from Organosilanes at Ambient Temperature Using Heterogeneous Gold Catalysts

An environmentally friendly (“green”), H₂-generation system was developed that involved hydrolytic oxidation of inexpensive organosilanes as hydrogen storage materials with newly developed heterogeneous gold nanoparticle catalysts. The gold catalyst functioned well at ambient temperature under aerobic conditions, providing efficient production of pure H₂. The newly developed size-selective gold nanoparticle catalysts could be separated easily from the reaction mixture containing organosilanes, allowing an on/off-switchable H₂-production by the introduction and removal of the catalyst. This is the first report of an on/off-switchable H₂-production system employing hydrolytic oxidation of inexpensive organosilanes without requiring additional energy.

Facile Synthesis of Platinum-Cerium(IV) Oxide Hybrids Arched on Reduced Graphene Oxide Catalyst in Reverse Micelles with High Activity and Durability for Hydrolysis of Ammonia Borane

Highly dispersed Pt-CeO₂ hybrids arched on reduced graphene oxide (Pt-CeO₂ /rGO) were facilely synthesized by a combination of the reverse micelle technique and a redox reaction without any additional reductant or surfactant. Under a N₂ atmosphere, the redox reaction between Ce³⁺ and Pt²⁺ occurs automatically in alkaline solution, which results in the formation of Pt-CeO₂ /rGO nanocomposites (NCs). The as-synthesized Pt-CeO₂ /rGO NCs exhibit superior catalytic performance relative to that shown by the free Pt nanoparticles, Pt/rGO, Pt-CeO₂ hybrid, and the physical mixture of Pt-CeO₂ and rGO; furthermore, the nanocomposites show significantly better activity than the commercial Pt/C catalyst toward the hydrolysis of ammonia borane (NH₃ BH₃ ) at room temperature. Moreover, the Pt-CeO₂ /rGO NCs have remarkable stability, and 92 % of their initial catalytic activity is preserved even after 10 runs. The excellent activity of the Pt-CeO₂ /rGO NCs can be attributed not only to the synergistic structure but also to the electronic effects of the Pt-CeO₂ /rGO NCs among Pt, CeO₂ , and rGO.

Covalent triazine framework supported non-noble metal nanoparticles with superior activity for catalytic hydrolysis of ammonia borane: from mechanistic study to catalyst design

Development of non-noble metal catalysts with similar activity and stability to noble metals is of significant importance in the conversion and utilization of clean energies.

Development of non-noble metal catalysts with similar activity and stability to noble metals is of significant importance in the conversion and utilization of clean energy. The catalytic hydrolysis of ammonia borane (AB) to produce 3 equiv. of H₂, as an example of where noble metal catalysts significantly outperform their non-noble peers, serves as an excellent test site for the design and optimization of non-noble metal catalysts. Our kinetic isotopic effect measurements reveal, for the first time, that the kinetic key step of the hydrolysis is the activation of H₂O. Deducibly, a transition metal with an optimal electronic structure that bonds H₂O and –OH in intermediate strengths would favor the hydrolysis of AB. By employing a covalent triazine framework (CTF), a newly developed porous material capable of donating electrons through the lone pairs on N, the electron densities of nano-sized Co and Ni supported on CTF are markedly increased, as well as their catalytic activities. Specifically, Co/CTF exhibits a total turnover frequency of 42.3 mol_H2 mol_Co^–1 min^–1 at room temperature, which is superior to all peer non-noble metal catalysts ever reported and even comparable to some noble metal catalysts.

In Pursuit of Sustainable Hydrogen Storage with Boron-Nitride Fullerene as the Storage Medium

Using well calibrated DFT studies we predict that experimentally synthesized B24 N24 fullerene can serve as a potential reversible chemical hydrogen storage material with hydrogen-gas storage capacity up to 5.13 wt %. Our theoretical studies show that hydrogenation and dehydrogenation of the fullerene framework can be achieved at reasonable rates using existing metal-free hydrogenating agents and base metal-containing dehydrogenation catalysts.

Alkaline Ammonia Electrolysis on Electrodeposited Platinum for Controllable Hydrogen Production

Ammonia is beginning to attract a great deal of attention as an alternative energy source carrier, because clean hydrogen can be produced through electrolytic processes without the emission of COx . In this study, we deposited various shapes of Pt catalysts under potentiostatic mode; the electrocatalytic oxidation behavior of ammonia using these catalysts was studied in alkaline media. The electrodeposited Pt was characterized by both qualitative and quantitative analysis. To discover the optimal structure and the effect of ammonia concentration, the bulk pH value, reaction temperature, and applied current of ammonia oxidation were investigated using potential sweep and galvanostatic methods. Finally, ammonia electrolysis was conducted using a zero-gap cell, producing highly pure hydrogen with an energy efficiency over 80 %.

Palladium(0) nanoparticles supported on polydopamine coated Fe3O4 as magnetically isolable, highly active and reusable catalysts for hydrolytic dehydrogenation of ammonia borane

Palladium(0) nanoparticles supported on polydopamine coated magnetic ferrite nanopowders are highly active and reusable catalyst in hydrogen generation from the hydrolysis of ammonia borane with a turnover frequency of 14.5 min⁻¹ at 25.0 ± 0.1 °C.