Hydrolytic Dehydrogenation Of Ammonia Borane Research Articles

Polyoxometalates-engineered hydrogen generation rate and durability of Pt/CNT catalysts from ammonia borane

Heterogeneously catalyzed hydrolytic dehydrogenation of ammonia borane is a remarkable structure sensitive reaction. In this work, a strategy by using polyoxometalates (POMs) as the ligands is proposed to engineer the surface and electronic properties of Pt/CNT catalysts toward the enhanced hydrogen generation rate and durability. Three kinds of POMs, i.e., silicotungstic acid (STA), phosphotungstic acid (PTA) and molybdophosphoric acid (PMA), are comparatively studied, among which the STA shows positive effects on the catalytic activity and durability. A catalyst structure-performance relationship is established by a combination of kinetic and isotopic analyses with multiple characterization techniques, such as HAADF-STEM, EDS, Raman spectroscopy and XPS. It is shown that the STA compared to the other two POMs can increase the Pt binding energy and thus promote the reaction. The insights demonstrated here could open a new avenue for boosting the reaction by employing the POMs as the ligands to engineer the catalyst electronic properties.

Effect of LDH composition on the catalytic activity of Ru/LDH for the hydrolytic dehydrogenation of ammonia borane

The hydrolytic dehydrogenation of ammonia borane (NH3-BH3, AB for short) in the presence of catalysts has been identified to be a safe and efficient way for hydrogen release. Understanding the dehydrogenation mechanism of AB is helpful and important to design efficient catalysts. So far, although the effects of various factors on dehydrogenation of AB have been studied, such as the noble metal particle size effect, crystal-phase effect and the support crystal plane effect, the effect of support composition on dehydrogenation of AB has rarely been reported yet. In this study, we choose composition-adjustable layered double hydroxide (MgAl-LDHs) as support for Ru nanoparticles, and use the as-prepared catalysts for comparing their catalytic activity towards the dehydrogenation of AB. The catalytic results demonstrate the catalytic activity of Ru/MgAl-LDHs is related to MgAl-LDHs composition, exhibiting a support-composition effect in the hydrolytic dehydrogenation of AB. Combining various characterizations, the different composition of MgAl-LDHs has an effect on the interaction between Ru nanoparticles and MgAl-LDHs, which directly affects the catalytic activity for the hydrolysis of AB. This study provides new important fundamental knowledge on the mechanism of AB hydrolysis over practical supported metal catalysts which can be used for a better catalyst design.

Novel activated carbon supported trimetallic PdCoAg nanoparticles as efficient catalysts for the hydrolytic dehydrogenation of ammonia borane

Activated carbon (AC) supported palladium, cobalt and silver nanoparticle (PdCoAg/AC) catalysts were prepared by in situ reduction of sodium borohydride (NaBH4) and characterized by various techniques such as X-ray diffraction (XRD), scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDX), Transmission electron microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). The PdCoAg/AC catalyst is active in the hydrolysis of ammonia-borane (AB) even at low temperatures. Compared with mono- (Pd) and bi-metallic (PdCo) nanoparticles, this trimetallic (PdCoAg) structure showed greatly increased catalytic activity for AB hydrolysis. Their hydrolysis completion time was 50 s. This study also included full experimental details of kinetic data to determine the activation parameters (Ea, ΔH and ΔS) for the rate law and the catalytic hydrolysis of AB. In addition, the PdCoAg/AC catalysts had favorable catalytic activity also after seven runs. Hydrogen generation rate (HG), Ea, ΔH and ΔS were obtained at 25 °C as 4666.66 mL min−1g−1 (2 mmol AB and 50 mg PdCoAg/AC), 26.836 kJ mol-1, 29.416 kJ mol−1and –108.42 J mol−1K−1, respectively. In addition, the study showed that Pd0.6Co0.2CAg0.2/AC (Pd:Co:Ag atomic ratio = 6:2:2) showed the total turnover frequency (TOF) value of 6624 h−1. These results demonstrate that the PdCoAg/AC catalyst is a promising alternative in search of the practical application of AB as a hydrogen storage material for fuel cell applications.

Reduced Graphene Oxide Sheets Supported Waxberry‐like Co Catalysts for Improved Hydrolytic Dehydrogenation of Ammonia Borane

AbstractCobalt nanoparticles (NPs) supported on reduced graphene oxide sheets have been synthesized via a facile chemical reduction method by adding surfactant PVA and controlling the preparation process. Compared with regular Co NPs and unsupported waxberry‐like Co NPs, the synthesized Co@rGO exhibited waxberry‐like structure and amorphous state, good dispersion, uniform particle size with 25 nm. The waxberry‐like Co@rGO catalyst needed 10.8 min for hydrolytic dehydrogenation of NH3⋅BH3, with an initial turnover frequency (TOF) of 12.14 molH2⋅min–1⋅molCo–1 and the activation energy of 45.49 kJ⋅mol–1. The improved catalytic activity can be ascribed to the special morphology and decreased particle size of Co NPs, as well as the synergistic effect between graphene sheets and Co NPs. The work also includes the kinetic studies on zero‐order with respect to substrate concentration and first‐order reaction with respect to catalyst concentration.

Electromagnetic-field-assisted synthesis of Ni foam film-supported CoCu alloy microspheres composed of nanosheets: A high performance catalyst for the hydrolysis of ammonia borane

The development of low-cost catalysts with high activity and stability for the dehydrogenation of ammonia borane for hydrogen production becomes important in the field of heterogeneous catalysis. In this communication, an electromagnetic-field-assisted deposition process was adopted to prepare Ni foam supported CoCu alloy microspheres composed of nanosheets (CoCu/Ni). In the hydrolytic dehydrogenation of ammonia borane, the initial rate of hydrogen production for the as-prepared CoCu/Ni catalyst can reach 30.5 mol H2 min−1 molcat−1. Moreover, the CoCu/Ni catalyst maintained its activity after 10 consecutive catalytic cycles, demonstrating its high stability and good reusability.

Ni nanoparticles supported on graphitic carbon nitride as visible light catalysts for hydrolytic dehydrogenation of ammonia borane.

The development of a robust and low-cost non-noble metal catalyst for photocatalytic H2 evolution is of great importance for practical applications. In this study, monodisperse Ni nanoparticles of controlled sizes were prepared by a facile method and anchored on graphitic carbon nitride (g-C3N4) nanosheets via a self-assembly route. The noble-metal-free Ni/g-C3N4 composite catalysts exhibit excellent photocatalytic activities for the hydrolytic dehydrogenation of ammonia borane (AB) under visible light. An optimum AB hydrolysis rate was obtained when the size of the Ni NPs was 3.2 nm, with an initial turnover frequency of 18.7 mol(hydrogen) mol(catalyst)-1 min-1 and an apparent activation energy of 36 kJ mol-1. This study provides validity for constructing high performance first-row transition metal nano-photocatalysts for the hydrolytic dehydrogenation of AB.

Discovery of a self-healing catalyst for the hydrolytic dehydrogenation of ammonia borane

Sustainable catalysts based on earth-abundant elements are considered as economical alternatives to precious-metal-bearing catalysts and could be impactful for many applications.

Kinetics-assisted discrimination of active sites in Ru catalyzed hydrolytic dehydrogenation of ammonia borane

The kinetics-assisted method is simple yet effective in discriminating Ru edge atoms as the dominant active sites for the reaction.

Group 4 oxides supported Rhodium(0) catalysts in hydrolytic dehydrogenation of ammonia borane

Rh3+ ions are first impregnated on Group 4 metal oxides (TiO2, ZrO2, HfO2) in aqueous solution and, then reduced with aqueous solution of NaBH4 to form rhodium(0) nanoparticles (NPs) on the oxide surface. The analyses reveal that Rh(0) NPs are highly dispersed on the surface of TiO2, ZrO2, HfO2. Rh0/MO2 (M: Ti, Zr, Hf) NPs have high activity and reusability in releasing H2 from the hydrolysis of ammonia borane with an initial turnover frequency of 643, 198, and 188 min−1, respectively, at 25.0 ± 0.1 °C. The reusability of Rh0/ZrO2 and Rh0/HfO2 catalysts is higher than that of the Rh0/TiO2 catalyst.

Influence of Nitrilotriacetic Acid (NTA) Addition on the Activity of Spherical Silica-nickel Particles for Hydrolytic Dehydrogenation of Ammonia Borane

Influence of Nitrilotriacetic Acid (NTA) Addition on the Activity of Spherical Silica-nickel Particles for Hydrolytic Dehydrogenation of Ammonia Borane

Copper oxide hollow spheres: Synthesis and catalytic application in hydrolytic dehydrogenation of ammonia borane

In this paper, CuO hollow microspheres with different shell thickness and porosity have been synthesized using carbonaceous saccharide microspheres as templates according to a modified literature method. These CuO hollow microspheres were characterized and their catalytic properties in the hydrolytic dehydrogenation of ammonia borane (NH3BH3, AB) were examined. A kinetic study indicated that a maximum hydrogen generation rate of 294 mL H2 min−1 (g catalyst)−1 can be achieved at 45 ± 0.2 °C in the present system, which is comparable with that for other reported Cu based catalysts.

Preparation of Spherical Molybdosilicic Acid-silica Composite Particles for Acid Promoted Hydrolytic Dehydrogenation of Ammonia Borane

Preparation of Spherical Molybdosilicic Acid-silica Composite Particles for Acid Promoted Hydrolytic Dehydrogenation of Ammonia Borane

Control of pore size in shell of hollow silica–alumina composite spheres for hydrolytic dehydrogenation of ammonia borane

In the present study, we attempted to control the shell pore size of hollow spheres and investigated the resulting effect on their acidic properties and activity for the acid-promoted hydrolytic dehydrogenation of ammonia borane. Silica shells were formed on polystyrene template particles via sol–gel method, followed by calcination. For controlling the pore structure, surfactants with various molecular lengths (decyltrimethylammonium bromide (DeTAB), cethyltrimethylammonium bromide (CTAB), and stearyltrimethylammonium bromide (STAB)) were used. The shells of all the hollow spheres included monodispersed and well-ordered pores, and the pore size increased with increase in the molecular length of the surfactant. In particular, the hollow spheres prepared with CTAB and STAB consisted of numerous well-ordered mesopores with sharp peaks centered at approximately 2.4 and 2.8 nm, respectively. The molar ratios of the hydrolytically evolved hydrogen to the initial NH3BH3 in the presence of the hollow spheres prepared with DeTAB, CTAB, and STAB were 0.9, 3.0, and 2.7, respectively, which indicated the stoichiometric amount of hydrogen was evolved in the presence of the hollow spheres prepared with CTAB and STAB. The amount and rate of hydrogen evolution depended on the pore structure, and the hollow spheres with well-ordered and appropriate-sized mesopores in the shells showed a large amount and high rate of hydrogen evolution.

Ruthenium(0) nanoparticles supported on silica coated Fe3O4 as magnetically separable catalysts for hydrolytic dehydrogenation of ammonia borane

Ruthenium(0) nanoparticles supported on bare or silica-coated magnetite are prepared by impregnation of ruthenium(III) ions followed by their reduction with aqueous solution of sodium borohydride on the surface of support. These magnetically isolable catalysts are used in hydrogen generation from the hydrolysis of ammonia borane at room temperature. They conserve their initial catalytic activity even after the fifth reuse in the hydrolysis reaction. Ruthenium(0) nanoparticles supported on bare magnetite and silica-coated magnetite provide turnover frequency values of 29 min−1 and 127 min−1 and in hydrolytic dehydrogenation of ammonia borane at 25.0 ± 0.1 °C. Thus, coating of the surface of magnetite with silica results in a significant enhancement in catalytic activity of ruthenium(0) nanoparticles in hydrogen generation from the hydrolysis of ammonia borane.

Monodisperse PtCu alloy nanoparticles as highly efficient catalysts for the hydrolytic dehydrogenation of ammonia borane

Pt-M alloy nanoparticles (NPs) with well-defined size and compositions exhibit dramatically catalytic performance in chemical reactions. In this work, monodisperse PtCu NPs with controlled size and compositions were synthesized by the co-reduction method in the presence of oleylamine. These NPs have excellent catalytic activities in the hydrolytic dehydrogenation of ammonia borane (AB) and their activities were composition dependent. Among the different-composition PtCu NPs, the Cu50Pt50 NPs exhibit the highest catalytic activity with an initial turnover frequency of 102.5 mol(hydrogen)·mol(catalyst)−1·min−1 and an apparent activation energy of 36 kJ·mol−1, which demonstrate the validity of partly replacing Pt by a first-row transition metal on constructing high performance heterogeneous nanocatalysts for the hydrolytic dehydrogenation of AB.

Effect of Ru crystal phase on the catalytic activity of hydrolytic dehydrogenation of ammonia borane

Ruthenium (Ru) is one of the most attractive catalysts in the hydrolytic dehygrogenation of ammonia borane. So far, the employed Ru-based catalysts are mainly focusing on hexagonal close packed structured Ru. In this work, we study the crystal phase effect of Ru on the hydrolytic dehygrogenation of ammonia borane, using face-centered cubic structured and hexagonal close packed structured Ru nanoparticles supported on γ-Al2O3. The results show that the catalytic activity is different even these two kinds of Ru nanoparticles hold similar size. Impressively, with the Ru particle size change, the variation trend of activity is opposite for face-centered cubic and hexagonal close packed structured Ru/γ-Al2O3. Finally, some possible reasons for their difference are proposed based on density functional theory calculations.

Hydrolytic dehydrogenation of ammonia borane catalyzed by poly(amidoamine) dendrimers-modified reduced graphene oxide nanosheets supported Ag0.3Co0.7 nanoparticles

Poly(amidoamine) dendrimers-modified reduced graphene oxide nanosheets (PAMAM/rGO) composite was selected as a carrier of heterogeneous Ag0.3Co0.7 nanoparticles in order to obtain an excellent catalyst for ammonia borane (AB) hydrolysis. During the synthetic processes, GO could easily assembled with PAMAM by the electrostatic and hydrogen-bonding interactions. Structural characterization revealed that Ag0.3Co0.7 bimetallic nanoparticles with uniform size distribution of 5nm are well dispersed on PAMAM/rGO composite architecture. Ag0.3Co0.7@PAMAM/rGO was found to be a highly active and reusable catalyst in hydrogen generation from the hydrolysis of AB with a turnover frequency value (TOF) of 19.79 molH2min–1molM–1 at 25.0±0.1°C and retained 75.4% of their initial activity with a complete release of hydrogen in five runs. The relatively high TOF value and low apparent activation energy (34.21kJmol–1) make these Ag0.3Co0.7@PAMAM/rGO NPs as a high-efficient catalyst for catalytic dehydrogenation of AB facilitating the development of practically applicable energy storage materials.

Ultrafine palladium nanoparticles anchoring graphene oxide-ionic liquid grafted chitosan self-assembled materials: The novel organic-inorganic hybrid catalysts for hydrogen generation in hydrolysis of ammonia borane

The novel graphene oxide-ionic liquid grafted chitosan composites (denoted as GO-ILCS) are firstly prepared via a self-assembly process. Then, they are used to anchor ultrafine palladium nanoparticles by the in-situ reduction of palladium chloride with sodium borohydride. The resultant Pd(0)/GO-ILCS organic-inorganic hybrid catalysts are characterized by various techniques and used to catalyze the hydrolytic dehydrogenation of ammonia borane (NH3BH3, AB) under ambient conditions. The results reveal that the palladium nanoparticles are highly dispersed on GO-ILCS and the Pd(0)/GO-ILCS catalysts exhibit high catalytic activity and excellent reusability in the reaction. The turnover frequency (TOF) is as high as 25.6 molH2·molPd-1·min-1 and the catalytic activity does not decrease obviously after six runs. The orders of palladium and AB concentrations are 1.00 and 0.33 in the catalytic reaction, respectively. Notably, the activation energy of the reaction (Ea = 38 kJ mol−1) over the resultant catalysts is obviously lower than most of the palladium-based catalysts reported previously. It is expected the Pd(0)/GO-ILCS catalysts are of exciting potential in the field of hydrogen energy.

Synergistic effects in atomic-layer-deposited PtCox/CNTs catalysts enhancing hydrolytic dehydrogenation of ammonia borane

Highly dispersed and narrowly size-distributed Pt-Co bimetallic nanoparticles supported on CNTs are fabricated by atomic layer deposition (ALD) of Pt followed by CoO ALD for hydrolytic dehydrogenation of ammonia borane. The controlled decoration of CoO significantly enhances the hydrogen evolution activity of the Pt-based catalysts due to the remarkable Pt-Co synergy, i.e., the TOF value is up to 675.1 molH2 molPt−1 min−1 for bimetallic PtCo20/CNTs catalyst, which is 1.8 times higher than that of monometallic Pt/CNTs catalyst. The underlying nature of the Pt-Co synergy is systematically investigated by combining multiple characterizations with kinetic and isotopic analyses. It is revealed that the decoration of CoO onto Pt provides unique Pt-Co interfaces and targeted Pt electronic properties, thereby exhibiting the lower activation energy and favorable OH bond cleavage being the rate-determining step for the hydrolysis reaction. The insights revealed here provide inspiration and guide for the rational design of other advanced nanocatalysts.

One-step synthesis of reduced graphene oxide supported CoW nanoparticles as efficient catalysts for hydrogen generation from NH3BH3

W-doped Co nanoparticles (NPs) supported on reduced graphene oxide (RGO) were prepared by the one-step in situ co-reduction of an aqueous solution of cobalt(II) chloride, sodium tungstate dihydrate, and graphene oxide (GO) using NaBH4 as the sole reductant at room temperature. The structure, size, and composition of the CoW/RGO catalysts were characterized by powder XRD, FTIR, EDS, and TEM. The as-synthesized Co0.9W0.1/RGO catalysts exhibited good catalytic activity for the hydrolytic dehydrogenation of ammonia borane (AB) at room temperature. Co/RGO, W/RGO, RGO-free Co0.9W0.1, and Co0.9W0.1/RGO catalyst had a turnover frequency (TOF) of 3.0, 0.1, 1.2, 16.4 mol H2 (mol catalyst)−1 min−1 at 25 °C. Compared to Co/RGO, W/RGO, and the RGO-free Co0.9W0.1, the as-synthesized Co0.9W0.1/RGO nanocatalysts exhibited much better catalytic activity. In addition, kinetic studies indicated that the catalytic hydrolysis of AB by Co0.9W0.1/RGO shows zeroth order kinetics with respect to the substrate concentration, but first order kinetics with respect to the catalyst concentration. Furthermore, the activation energy (Ea) of Co0.9W0.1/RGO was estimated to be 30.7 kJ mol−1, which is lower than the values of most reported metal-based catalysts.