Hydrolytic Dehydrogenation Research Articles

Nanostructured Ni2P as a Robust Catalyst for the Hydrolytic Dehydrogenation of Ammonia–Borane

AbstractAmmonia–borane (AB) is a promising chemical hydrogen‐storage material. However, the development of real‐time, efficient, controllable, and safe methods for hydrogen release under mild conditions is a challenge in the large‐scale use of hydrogen as a long‐term solution for future energy security. A new class of low‐cost catalytic system is presented that uses nanostructured Ni2P as catalyst, which exhibits excellent catalytic activity and high sustainability toward hydrolysis of ammonia–borane with the initial turnover frequency of 40.4 mol(H2) mol(Ni2P)−1 min−1 under air atmosphere and at ambient temperature. This value is higher than those reported for noble‐metal‐free catalysts, and the obtained Arrhenius activation energy (Ea=44.6 kJ mol−1) for the hydrolysis reaction is comparable to Ru‐based bimetallic catalysts. A clearly mechanistic analysis of the hydrolytic reaction of AB based on experimental results and a density functional theory calculation is presented.

Hydrolytic dehydrogenation of ammonia borane catalyzed by metal-organic framework supported bimetallic RhNi nanoparticles

Highly dispersed bimetallic Rh–Ni nanoparticles with an average diameter of 1.1 ± 0.2 nm have been successfully anchored on the metal-organic frameworks (ZIF-8) by using a simple liquid impregnation method. The RhNi@ZIF-8 nanocatalysts are isolated from the solution and well characterized by using powder XRD, TEM, EDX, XPS, ICP-AES, and N2 adsorption-desorption. Among all the tested catalysts with different compositions, Rh15Ni85@ZIF-8 exhibits the highest catalytic activity toward hydrolysis of ammonia borane, with the turnover frequency value of 58.8 mol H2·min−1·(mol catalyst)−1, and 100% hydrogen selectivity at room temperature.

Synthesis and catalytic performance of a novel RuCuNi/CNTs nanocomposite in hydrolytic dehydrogenation of ammonia borane

Trimetallic RuCuNi nanoparticles (NPs) were successfully immobilized on carbon nanotubes (CNTs) using a simple liquid impregnation-reduction method, and the RuCuNi/CNTs catalyst was applied to the hydrolytic dehydrogenation of ammonia borane (AB) at room temperature. All the catalyst activity from different metal Ru, Cu, Ni supported on CNTs have been detailedly investigated. Well dispersed RuCuNi nanoparticles are stabilized and immobilized by CNTs. The research results show that the RuCuNi/CNTs nanomaterials exhibit a higher catalytic activity than those of monometallic Ru, Cu, Ni and bimetallic RuCu, RuNi counterparts loadings as well as RuCuNi NPs, owing to the strong trimetallic synergistic effects, uniform distribution of nanoparticles on the surface of CNTs and bi-functional effects between the RuCuNi nanoparticles and the support of CNTs. The activation energy (Ea) and the turn over frequency (TOF) of this RuCuNi/CNTs catalyst are 36.67 kJ/mol and 311.15 mol H2 min−1 (mol Ru)−1, respectively. In addition, the catalytic stability during the recycling tests also has an outstanding performance for the hydrolysis of AB.

Ruthenium nanoparticles confined in SBA-15 as highly efficient catalyst for hydrolytic dehydrogenation of ammonia borane and hydrazine borane.

Ultrafine ruthenium nanoparticles (NPs) within the mesopores of the SBA-15 have been successfully prepared by using a “double solvents” method, in which n-hexane is used as a hydrophobic solvent and RuCl3 aqueous solution is used as a hydrophilic solvent. After the impregnation and reduction processes, the samples were characterized by XRD, TEM, EDX, XPS, N2 adsorption-desorption, and ICP techniques. The TEM images show that small sized Ru NPs with an average size of 3.0 ± 0.8 nm are uniformly dispersed in the mesopores of SBA-15. The as-synthesized Ru@SBA-15 nanocomposites (NCs) display exceptional catalytic activity for hydrogen generation by the hydrolysis of ammonia borane (NH3BH3, AB) and hydrazine borane (N2H4BH3, HB) at room temperature with the turnover frequency (TOF) value of 316 and 706 mol H2 (mol Ru min)−1, respectively, relatively high values reported so far for the same reaction. The activation energies (Ea) for the hydrolysis of AB and HB catalyzed by Ru@SBA-15 NCs are measured to be 34.8 ± 2 and 41.3 ± 2 kJ mol−1, respectively. Moreover, Ru@SBA-15 NCs also show satisfied durable stability for the hydrolytic dehydrogenation of AB and HB, respectively.

Hydrogen generation from hydrolytic dehydrogenation of hydrazine borane by poly(N-vinyl-2-pyrrolidone)-stabilized palladium nanoparticles

Poly(N-vinyl-2-pyrrolidone)-stabilized palladium nanoparticles (3.5 ± 1.0 nm) are efficient catalysts in the hydrolytic dehydrogenation of hydrazine borane to give hydrogen gas. The catalyst, prepared by reduction of palladium metal ion in ethanol/water mixture by an alcohol reduction method, is durable and efficient catalysts for hydrogen generation from the hydrolytic dehydrogenation of hydrazine borane even at very low concentrations and temperature, providing an average turnover frequency of 42.9 min−1 with an activation energy of 54.5 ± 2 kJ mol−1 for the hydrolytic dehydrogenation of hydrazine borane.

Efficient catalytic hydrolytic dehydrogenation of ammonia borane over surfactant-free bimetallic nanoparticles immobilized on amine-functionalized carbon nanotubes

A series of surfactant-free bimetallic Au−M (M = Co, Ni) nanoparticles (NPs) immobilized on amine-functionalized carbon nanotubes (CNTs) have been successfully prepared using three synthesis methods and then used as effective catalysts for hydrolytic dehydrogenation of ammonia borane (NH3BH3, AB). Surprisingly, compared to the ex situ and one-pot seeding-growth synthesized Au–Co catalysts, the in situ synthesized Au–Co alloy catalyst exhibited remarkably enhanced activity, featuring turnover frequency (TOF) values of 36.05 and 148.51 molH2 molcat−1 min−1 at 298 and 328 K, respectively, comparable to the values acquired from the reported highly active Co-based catalysts for hydrolytic dehydrogenation of aqueous AB. The XRD investigations of catalysts after heating at different temperatures in Ar atmosphere showed the different existence state of amorphous Co species of Au–Co NPs. In addition, these catalysts could keep the high activity even after 14 h, indicating that they had high stability/durability.

Porous Materials for Hydrolytic Dehydrogenation of Ammonia Borane.

Hydrogen storage is still one of the most significant issues hindering the development of a “hydrogen energy economy”. Ammonia borane is notable for its high hydrogen densities. For the material, one of the main challenges is to release efficiently the maximum amount of the stored hydrogen. Hydrolysis reaction is a promising process by which hydrogen can be easily generated from this compound. High purity hydrogen from this compound can be evolved in the presence of solid acid or metal based catalyst. The reaction performance depends on the morphology and/or structure of these materials. In this review, we survey the research on nanostructured materials, especially porous materials for hydrogen generation from hydrolysis of ammonia borane.

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

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

Carbon dispersed copper-cobalt alloy nanoparticles: A cost-effective heterogeneous catalyst with exceptional performance in the hydrolytic dehydrogenation of ammonia-borane

Herein, we report the development of a new and cost-effective nanocatalyst for the hydrolytic dehydrogenation of ammonia-borane (NH3BH3), which is considered to be one of the most promising solid hydrogen carriers due to its high gravimetric hydrogen storage capacity (19.6wt%) and low molecular weight. The new catalyst system consisting of bimetallic copper-cobalt alloy nanoparticles supported on activated carbon was simply and reproducibly prepared by surfactant-free deposition-reduction technique at room temperature. The characterization of this new catalytic material was done by the combination of multi-pronged techniques including ICP-MS, XRD, XPS, BFTEM, HR-TEM, STEM and HAADF-STEM-line analysis. The sum of their results revealed that the formation of copper-cobalt alloy nanoparticles (dmean=1.8nm) on the surface of activated carbon (CuCo/C). These new carbon supported copper-cobalt alloy nanoparticles act as highly active catalyst in the hydrolytic dehydrogenation of ammonia-borane, providing an initial turnover frequency of TOF=2700h−1 at 298K, which is not only higher than all the non-noble metal catalysts but also higher than the majority of the noble metal based homogeneous and heterogeneous catalysts employed in the same reaction. More importantly, easy recovery and high durability of these supported CuCo nanoparticles make CuCo/C recyclable heterogeneous catalyst for the hydrolytic dehydrogenation of ammonia-borane. They retain almost their inherent activity even at 10th catalytic reuse in the hydrolytic dehydrogenation of ammonia-borane at 298K.

Synergetic Catalysis of Non-noble Bimetallic Cu–Co Nanoparticles Embedded in SiO2 Nanospheres in Hydrolytic Dehydrogenation of Ammonia Borane

Ultrafine non-noble bimetallic Cu–Co nanoparticles (∼2 nm) encapsulated within SiO2 nanospheres (Cu–Co@SiO2) have been successfully synthesized via a one-pot synthetic route in a reverse micelle system and characterized by SEM, TEM, EDS, XPS, PXRD, ICP, and N2 adsorption–desorption methods. In each core–shell Cu–Co@SiO2 nanosphere, several Cu–Co NPs are separately embedded in SiO2. Compared with their monometallic counterparts, the bimetallic core–shell nanospheres CuxCo1–x@SiO2 with different metal compositions show a higher catalytic performance for hydrogen generation from the hydrolysis of ammonia borane (NH3BH3, AB) at room temperature, due to the strain and ligand effects on the modification of the surface electronic structure and chemical properties of Cu–Co NPs in the SiO2 nanospheres. Especially, the Cu0.5Co0.5@SiO2 nanospheres show the best catalytic performance among all the synthesized CuxCo1–x@SiO2 catalysts in the hydrolytic dehydrogenation of AB. In addition, the activation energy (Ea) of C...

Carbon Nanotubes as Support in the Platinum‐Catalyzed Hydrolytic Dehydrogenation of Ammonia Borane

We report remarkable support effects for carbon nanotubes (CNTs) in the Pt/CNT-catalyzed hydrolytic dehydrogenation of ammonia borane. The origin of the support-dependent activity and durability is elucidated by combining the catalytic and durability testing with characterization by a range of spectroscopy and high-angle annular dark-field scanning transmission electron microscopy techniques and ICP analysis. The effects mainly arise from different electronic properties and different abilities for the adsorption of boron-containing species on platinum surfaces and changes in size and shape of the platinum particles during the reaction. Defect-rich CNTs in particular are a promising support material, as it not only enhances the platinum binding energy, leading to the highest hydrogen generation rate, but also inhibits the adsorption of boron-containing species and stabilizes the platinum nanoparticles to resist the agglomeration during the reaction, leading to the highest durability. The insights revealed herein may pave the way for the rational design of highly active and durable metal/carbon catalysts for the hydrolytic dehydrogenation of ammonia borane.

Kinetics study on hydrolytic dehydrogenation of alkaline sodium borohydride catalyzed by Mo-modified Co–B nanoparticles

Mo-modified Co–B nanoparticles have been prepared by the co-deposition chemical reduction method. The relationship between microstructure, catalytic activity and kinetics performance for H2 generation by hydrolysis of alkaline NaBH4 is studied. Compared to unmodified Co–B nanoparticles, the synthesized Co–Mo–B nanoparticles exhibit smaller particle size with average diameter of 30 nm, more uniform distribution with unconspicuous agglomeration, and larger specific surface area. The induced Mo in the Co–Mo–B catalyst exists as molybdenum oxides, which facilitates the dissociation of water due to weakening of the bond strength of the H–OH bond and promote the hydrolysis reaction of NaBH4. As a result, the maximum hydrogen generation rate and the activation energy of the hydrolysis reaction catalyzed by Mo-modified Co–B catalyst reach to 4200mLH2min−1gcatalyst−1 and 43.7 kJ mol−1, respectively, which are superior to those of the Co–B catalyst. Kinetic studies show that, in low concentration of NaBH4, first-order reaction is observed with respect to NaBH4 concentration, indicating that surface adsorption of BH4− is the rate-limiting step. At high NaBH4 concentration, hydrolysis reaction is zero-order, and the hydrolysis rate depends on surface reaction of adsorbed molecules.

Influence of Si/Al molar ratio of hollow silica–alumina composite spheres on their activity for hydrolytic dehydrogenation of ammonia borane

In this work, we investigated influence of Si/Al molar ratio of hollow silica–alumina composite spheres on their activity for hydrolytic dehydrogenation of ammonia borane. The hollow spheres were prepared by polystyrene templates method. In this method, silica–alumina composite shell were coated on polystyrene particles via sol–gel reaction, and the PS template particles were removed by calcination. From the result of transmission electron microscopy, the obtained hollow spheres with Si/Al molar ratios of 12, 23, 49, 92, and 186 were almost similar morphologies. The activities of these hollow spheres for the hydrolytic dehydrogenation of ammonia borane were compared. The amount of hydrogen evolution of hollow spheres with a Si/Al molar ratio of 49 was the highest of all the hollow spheres. From the result of solid-state 27Al MAS NMR and NH3-TPD, the dispersion and amount of aluminum species play important roles in determining the amount of hydrogen evolution. Additionally, the amount of hydrogen evolution depends on the amount of Brønsted acid sites of the hollow spheres.

Air-Stable (CAAC)CuCl and (CAAC)CuBH4 Complexes as Catalysts for the Hydrolytic Dehydrogenation of BH3NH3.

The first stable copper borohydride complex [(CAAC)CuBH4] [CAAC = cyclic(alkyl)(amino)carbene] bearing a single monodentate ligand was prepared by addition of NaBH4 or BH3NH3 to the corresponding [(CAAC)CuCl] complex. Both complexes are air-stable and promote the catalytic hydrolytic dehydrogenation of ammonia borane. The amount of hydrogen released reaches 2.8 H2/BH3 NH3 with a turnover frequency of 8400 mol H2 molcat(-1) h(-1) at 25 °C. In a fifteen-cycle experiment, the catalyst was reused without any loss of efficiency.

Air‐Stable (CAAC)CuCl and (CAAC)CuBH4 Complexes as Catalysts for the Hydrolytic Dehydrogenation of BH3NH3

AbstractThe first stable copper borohydride complex [(CAAC)CuBH4] [CAAC=cyclic(alkyl)(amino)carbene] bearing a single monodentate ligand was prepared by addition of NaBH4 or BH3NH3 to the corresponding [(CAAC)CuCl] complex. Both complexes are air‐stable and promote the catalytic hydrolytic dehydrogenation of ammonia borane. The amount of hydrogen released reaches 2.8 H2/BH3NH3 with a turnover frequency of 8400 mol molcat−1 h−1 at 25 °C. In a fifteen‐cycle experiment, the catalyst was reused without any loss of efficiency.

Preparation, characterization and catalytic sodium borohydride hydrolysis of nanostructured cobalt–phosphorous catalysts

In this paper, we report on the preparation, characterization and catalytic NaBH4 hydrolysis of nanostructured Co–P catalysts prepared using electroless plating method on the Cu sheet. Co–P catalysts composed of nanoplatelets, nanospheres and nanoflowers are successfully obtained by tuning the NaH2PO2 concentration. The as-prepared Co–P sample with hierarchical flower-like shape shows significantly enhanced catalytic activity during hydrolytic dehydrogenation of NaBH4, affording hydrogen release rate of 1647.9 mL min−1 g−1 at 30 °C and an activation energy of 47.0 kJ mol−1. This enhanced activity is due to their novel nanoflower architectures made up of nanoplatelets or the high surface roughness, providing many defects of angle, step, or edge and so on, to form more active sites on the catalyst surface. Furthermore, the hydrogen generation rate decreases gradually after 11 cycles, about 61% of the initial hydrogen generation rate. The study reveals the reason may be the decrease in the amount of P that provides active metallic Co sites on the catalyst surface.

Catalytic hydrolysis of ammonia borane for hydrogen generation using Cu(0) nanoparticles supported on TiO 2 nanofibers

Abstract Cu(0) nanoparticles supported on TiO 2 nanofibers (Cu-decorated TiO 2 NFs) are introduced as an effective photocatalyst for hydrolytic dehydrogenation of ammonia borane (AB) under solar radiation. The introduced Cu-decorated TiO 2 NFs were prepared using electrospinning followed by hydrothermal treatment as a novel route for preparation of metal-decorated metal oxide nanofibers. Interestingly, the utilized physicochemical characterizations showed that the prepared nanocatalyst composed of core TiO 2 NFs decorated by Cu(0) NPs. A strong photocatalytic activity for catalytic hydrolysis of AB under solar radiation using the introduced nanocatalysts was observed. The results reveal that high rate of hydrogen release from ammonia borane (2.75 equivalent moles) as compared to undecorated TiO 2 NFs (1.6 equivalent moles) and pristine Cu NPs (1.2 equivalent moles). The obtained high hydrogen production, in case of the introduced Cu-decorated TiO 2 NFs, is attributed to the dual effect of counter parts. Furthermore, the introduced nanofibers could be utilized for three successive cycles with the same efficiency which reflects high stability. Moreover, the photocatalytic activity of the introduced NFs was further confirmed by photodegradation of methylene blue (MB) under solar radiation; complete removal was observed after 120 min.

Composition-controlled catalysis of reduced graphene oxide supported CuPd alloy nanoparticles in the hydrolytic dehydrogenation of ammonia borane

Addressed herein is the composition-controlled catalysis of CuPd alloy nanoparticles (NPs) supported on reduced graphene oxide (RGO) in the hydrolytic dehydrogenation of ammonia borane (AB). Nearly monodisperse CuPd alloy NPs were synthesized by using a surfactant-assisted organic solution phase protocol comprising the co-reduction of acetylacetonate complexes of Pd and Cu by morpholine borane complex in oleylamine and 1-octadecene at 80°C. The presented recipe allowed us to make a composition control over the CuPd alloy NPs. Three different compositions of CuPd alloy NPs (2.7nm Cu30Pd70, 2.9nm Cu48Pd52, 3.0nm Cu75Pd25) could be prepared among which the Cu75Pd25 NPs showed the best catalytic performance in hydrogen generation from the hydrolysis of AB. Among the various support materials tested for as-prepared Cu75Pd25 alloy NPs, the RGO-Cu75Pd25 catalysts showed the highest performance in the hydrolysis of AB. Moreover, the activity of the RGO-Cu75Pd25 catalysts were dramatically enhanced by annealing them at 400°C for 1h under Ar–H2 (5% H2) gas flow and an unprecedented TOF value of 29.9min−1 was obtained in the hydrolysis of AB at room temperature. The reported TOF value here is much higher than RGO-Cu (TOF=3.61min−1) and even higher than RGO-Pd catalysts (TOF=26.6min−1). The detailed kinetics of RGO-Cu75Pd25 catalyzed AB hydrolysis was also studied depending on catalyst concentration, substrate concentration and temperature. The apparent activation energy of the catalytic hydrolysis of AB was calculated to be 45±3kJmol−1.

Control of particle size of hollow silica-alumina composite spheres prepared using L(+)-arginine and their activity for hydrolytic dehydrogenation of ammonia borane

Control of particle size of hollow silica-alumina composite spheres prepared using L(+)-arginine and their activity for hydrolytic dehydrogenation of ammonia borane

Influence of pH on immobilization of molybdosilicic acid on hollow silica spheres and promotion of hydrolytic dehydrogenation of ammonia borane

In this work, we investigated the influence of the pH condition during the impregnation process on the immobilization of molybdosilicic acid on hollow silica spheres and their activity for hydrolytic dehydrogenation of ammonia borane. To adjust the pH, amino acids such as L-aspartic acid and L(+)-arginine were added to the impregnating solution. Transmission and scanning electron microscopy showed that samples prepared at lower pH consist of homogeneous hollow silica spheres while those prepared at higher pH include collapsed hollow spheres. The activity for hydrogen evolusion from aqueous NH3BH3 solution depends on the catalyst; the molar ratios of the hydrolytically generated hydrogen to the initial NH3BH3 were 2.0, 1.3, 1.3, and 1.0 at pH = 4.0, 6.0, 8.0, and 9.7, respectively. After the reaction, the sample prepared at lower pH had a higher valence value of Mo species according to results from X-ray photoelectron spectroscopy, and the corresponding amount of Mo species in the reaction solution was also lower. The results indicated that the molybdosilicic acid supported on homogeneous hollow silica spheres had a higher valence value of Mo species and the effectively immobilized acid had a higher activity for hydrogen evolusion from aqueous NH3BH3 solution.