Hydrogen generation from sodium borohydride hydrolysis by multi-walled carbon nanotube supported platinum catalyst: A kinetic study

In this study, it is aimed to investigate hydrogen (H₂) generation from sodium borohydride (NaBH₄) hydrolysis by multi-walled carbon nanotube supported platinum catalyst (Pt/MWCNT) under various conditions (0–0.03 g Pt amount catalyst, 2.58–5.03 wt % NaBH₄, and 27–67 °C) in detail. For comparison, carbon supported platinum (Pt/C) commercial catalyst was used for H₂ generation experiments under the same conditions. The reaction rate of the experiments was described by a power law model which depends on the temperature of the reaction and concentrations of NaBH₄. Kinetic studies of both Pt/MWCNT and Pt/C catalysts were done and activation energies, which is the required minimum energy to overcome the energy barrier, were found as 27 kJ/mol and 36 kJ/mol, respectively. Pt/MWCNT catalyst is accelerated the reaction less than Pt/C catalyst while Pt/MWCNT is more efficient than Pt/C catalyst, they are approximately 98% and 95%, respectively. According to the results of experiments and the kinetic study, the reaction system based on NaBH₄ in the presence of Pt/MWCNT catalyst can be a potential hydrogen generation system for portable applications of proton exchange membrane fuel cell (PEMFC).     

A highly active Co-B catalyst for hydrogen generation from sodium borohydride hydrolysis

Co-B catalysts were prepared by the chemical reduction of CoCl₂ with NaBH₄ for hydrogen generation from borohydride hydrolysis. The catalytic properties of the Co-B catalysts were found to be sensitive to the preparation conditions including pH of the NaBH₄ solution and mixing manner of the precursors. A Co-B catalyst with a very high catalytic activity was obtained through the formation of a colloidal Co(OH)₂ intermediate. The ultra-fine particle size of 10 nm accounted for its super activity for hydrogen generation with a maximum rate of 26 L min⁻¹ g⁻¹ at 30 °C. The catalyst also changed the hydrolysis kinetics from zero-order to first-order.     

Hydrogen generation from the hydrolysis of ammonia-borane using intrazeolite cobalt(0) nanoclusters catalyst

Previously being used as highly active catalyst in the hydrolysis of sodium borohydride, intrazeolite cobalt(0) nanoclusters were also employed as catalyst in the hydrolysis of ammonia-borane (H₃NBH₃). Intrazeolite cobalt(0) nanoclusters were found to be active catalyst in this hydrolysis reaction of ammonia-borane providing 5450 total turnovers at room temperature before deactivation. The results of the kinetic study shows that the catalytic hydrolysis of AB is first order with respect to the catalyst concentration and zero order with respect to substrate concentration. Activation parameters could be obtained from the evaluation of the rate constants at different temperature. The results reveal that intrazeolite cobalt(0) nanoclusters can be considered as promising candidate to be used as catalyst in developing highly efficient portable hydrogen generation systems using ammonia-borane as solid hydrogen storage material.     

A review: Hydrogen generation from borohydride hydrolysis reaction

In this review, a convenient hydrogen generation technology based on sodium borohydride and water as hydrogen carriers has been summarized. The recent progresses in the development of the hydrogen generation from sodium borohydride hydrolysis are reviewed. The NaBH₄ hydrolysis behavior is discussed in detail. From reported results, it is considered that hydrogen generation from sodium borohydride hydrolysis is a feasible technology to supply hydrogen for the PEMFC. It has been found that the reported results are encouraging although there are some engineering problems that lie ahead. The critical issues of this hydrogen generation technology have been highlighted and discussed.     

Hydrogen generation utilizing alkaline sodium borohydride solution and supported cobalt catalyst

Supported Co catalysts with different supports were prepared for hydrogen generation (HG) from catalytic hydrolysis of alkaline sodium borohydride solution. As a result, we found that a γ-Al₂O₃ supported Co catalyst was very effective because of its special structure. A maximum HG rate of 220 mL min⁻¹ g⁻¹ catalyst and approximately 100% efficiency at 303 K were achieved using a Co/γ-Al₂O₃ catalyst containing 9 wt.% Co. The catalyst has quick response and good durability to the hydrolysis of alkaline NaBH₄ solution. It is feasible to use this catalyst in hydrogen generators with stabilized NaBH₄ solutions to provide on-site hydrogen with desired rate for mobile applications, such as proton exchange membrane fuel cell (PEMFC) systems.     

Nickel modified dolomite in the hydrogen generation from sodium borohydride hydrolysis

Hydrogen is expected to play an important role as an energy carrier in the world's future energy systems, as it is environmentally friendly and flexible in use. Hydrolysis of NaBH₄ is a promising and effective method, especially for fuel cells and other portable devices, thanks to hydrogen release. Therefore, catalyst research is of great importance in the development of this technology. In this study, Ni/Dolomite catalyst was synthesized by wet impregnation method and used in hydrolysis process. Additionally, the effects of reaction temperature (30–60 °C), nickel content (10–40 wt%), catalyst amount (25–125 mg), NaOH concentration (0.10–0.75 M), and an initial amount of NaBH₄ (25–125 mg) on hydrogen yield were investigated. Eventually, the catalyst with 40 wt% Ni content was assigned as the most suitable catalyst, attaining H₂ production of 100% with a rate of 88.16 mL H₂/g_cat.min at 60 °C with 5 mL of 0.25 M NaOH, NaBH₄, and Ni/Dolomite catalyst (100 mg).     

Hydroxyapatite-supported palladium(0) nanoclusters as effective and reusable catalyst for hydrogen generation from the hydrolysis of ammonia-borane

Herein we report the preparation, characterization and catalytic use of hydroxyapatite-supported palladium(0) nanoclusters in the hydrolysis of ammonia-borane. Palladium(0) nanoclusters were formed in situ from the reduction of palladium(II) ion exchanged hydroxyapatite during the hydrolysis of ammonia-borane and supported on hydroxyapatite. The hydroxyapatite-supported palladium(0) nanoclusters are stable enough to be isolated as solid materials and characterized by using a combination of advanced analytical techniques. They are isolable, redispersible and reusable as an active catalyst in the hydrolysis of ammonia-borane even at low concentration and temperature. They provide a maximum hydrogen generation rate of ∼1425 mL H₂ min⁻¹ (g Pd)⁻¹ and 12300 turnovers in the hydrolysis of ammonia-borane at 25 ± 0.1 °C before deactivation. The work reported here also includes the full experimental details for the collection of a wealth of kinetic data to determine the activation energy (E_a = 54.8 ± 2.2 kJ/mol) and the effect of catalyst concentration on the rate for the catalytic hydrolysis of ammonia-borane.     

Zeolite confined palladium(0) nanoclusters as effective and reusable catalyst for hydrogen generation from the hydrolysis of ammonia-borane

Zeolite confined palladium(0) nanoclusters were prepared by a two step procedure: incorporation of Pd²⁺ ions into the zeolite-Y by ion-exchange followed by the reduction of Pd²⁺ ions in the supercages of zeolite-Y with sodium borohydride at room temperature. Zeolite confined palladium(0) nanoclusters are stable enough to be isolated as solid materials and characterized by ICP-OES, XRD, HRTEM, SEM, X-ray photoelectron spectroscopy and N₂ adsorption technique. These nanoclusters are isolable, redispersible and reusable as an active catalyst in the hydrolysis of ammonia-borane solution. Zeolite confined palladium(0) nanoclusters provide 15,600 turnovers in hydrogen generation from the hydrolysis of ammonia-borane at 25.0 ± 0.1 °C.     

Catalytic hydrolysis of sodium borohydride by a novel nickel–cobalt–boride catalyst

With the aim of designing an efficient hydrogen generator for portable fuel cell applications nickel–cobalt–boride (Ni–Co–B) catalysts were prepared by a chemical reduction method and their catalytic hydrolysis reaction with alkaline NaBH₄ solution was studied. The performance of the catalysts prepared from NaBH₄ solution with NaOH, and without NaOH show different hydrogen generation kinetics. The rate of hydrogen generation was measured using Ni–Co–B catalyst as a function of the concentrations of NaOH and NaBH₄, as well as the reaction temperature, in the hydrolysis of alkaline NaBH₄ solution. The hydrogen generation rate increases for lower NaOH concentrations in the alkaline NaBH₄ solution and decreases after reaching a maximum at 15 wt.% of NaOH. The hydrogen generation rate is found to be constant with respect to the concentration of NaBH₄ in the alkaline NaBH₄ solution. The activation energy for hydrogen generation is found to be 62 kJ mol⁻¹, which is comparable with that of hydrogen generation by a ruthenium catalyst.     

Hydrogen generation by hydrolysis of sodium borohydride on CoB/SiO2 catalyst

Generation of hydrogen by hydrolysis of alkali metal hydrides has attracted attention. Unsupported CoB catalyst demonstrated high activity for the catalytic hydrolysis of NaBH₄ solution. However, unsupported CoB nanoparticles were easy to aggregate and difficult to reuse. To overcome these drawbacks, CoB/SiO₂ was prepared and tested for this reaction. Cobalt (II) acetate precursor was loaded onto the SiO₂ support by incipient-wetness impregnation method. After drying at 100 °C, Co cations were deposited on the support. The dried sample was then dispersed in methanol/water solution and then fully reduced by NaBH₄ at room temperature. The catalyst was characterized by N₂ sorption, XRD and XPS. The results indicated that the CoB on SiO₂ possessed amorphous structure. B and Co existed both in elemental and oxidized states. SiO₂ not only affected the surface compositions of CoB, but also affected the electronic states of Co and B. B⁰ could donate partial electron to Co⁰. The structure effect caused by the SiO₂ support helped to prevent CoB nanocluster from aggregation and therefore the activity increased significantly on hydrolysis of alkaline NaBH₄ solution. The CoB/SiO₂ catalyst showed much higher activity than the unsupported CoB catalyst. At 298 K, the hydrogen generation rate on CoB/SiO₂ catalyst was 4 times more than that on the unsupported CoB catalyst. The hydrogen generation rate was as high as 10,586 mL min⁻¹ g⁻¹ catalyst at 298 K. CoB/SiO₂ is a very promising catalyst for this reaction.     

Carbon-supported cobalt catalyst for hydrogen generation from alkaline sodium borohydride solution

Low cost transition metal catalysts with high performance are attractive for the development of on-board hydrogen generation systems by catalytic hydrolysis of sodium borohydride (NaBH₄) in fuel cell fields. In this study, hydrogen production from alkaline NaBH₄ via hydrolysis process over carbon-supported cobalt catalysts was studied. The catalytic activity of the supported cobalt catalyst was found to be highly dependent on the calcination temperatures. The hydrogen generation rate increases with calcination temperatures in the range of 200–400 °C, but a high calcination temperature above 500 °C led to markedly decreased activity. X-ray diffraction patterns reveal that the catalysts experience phase transition from amorphous Co–B to crystalline cobalt hydroxide with increase in calcination temperatures. The reaction performance is also dependent on the concentration of NaBH₄, and the hydrogen generation rate increases for lower NaBH₄ concentrations and decreases after reaching a maximum at 10 wt.% of NaBH₄.     

Water soluble laurate-stabilized ruthenium(0) nanoclusters catalyst for hydrogen generation from the hydrolysis of ammonia-borane: High activity and long lifetime

The simplest amine-borane, considered as solid hydrogen storage material, ammonia-borane (H₃NBH₃) can release hydrogen gas upon catalytic hydrolysis under mild conditions. Herein, we report the preparation of a novel catalyst, water dispersible laurate-stabilized ruthenium(0) nanoclusters from the dimethylamine-borane reduction of ruthenium(III) chloride in sodium laurate solution at room temperature. The ruthenium nanoclusters in average size of 2.6 ± 1.2 nm were isolated from the solution and well characterized by using TEM, XPS, FTIR, and UV–visible electronic absorption spectroscopy. The water dispersible laurate-stabilized ruthenium(0) nanoclusters were found to be highly active and long-live catalyst with a TOF of 75 mol H₂/mol Ru·min and TTO value of 5900 mol H₂/mol Ru in the hydrolysis of ammonia-borane at 25.0 ± 0.1 °C.     

Sodium borohydride hydrolysis by using ceramic foam supported bimetallic and trimetallic catalysts

In this study, bimetallic and trimetallic catalysts with different contents on ceramic foam support were prepared in an integrated continuous system and performances of catalysts were investigated using a fixed bed reactor. Bimetallic copper-cobalt, lithium-cobalt, and platinum and palladium added bimetallic (trimetallic) catalysts were prepared and characterized by SEM for morphological structure analysis, BET for surface area measurements, and XRD and XPS for crystal structure analysis. In the hydrogen production tests carried out at different flow rates and temperatures, Pd included trimetallic catalysts performed slightly better than Pt added bimetallic catalysts. Although Pd catalysts have low activity than Pt catalysts according to literature, Pd catalyst prepared on ceramic foam had higher activity. In this work, PdLiCo and PdCuCo catalysts demonstrated highest hydrogen production rates (respectively 4.76 ml/min and 4.69 ml/min) as well as highest specific surface area (7.301 m²/g for PdLiCo, 11.821 m²/g for PdCuCo).     

Nickel-based catalysts for hydrogen evolution by hydrolysis of sodium borohydride: from structured nickel hydrazine nitrate complexes to reduced counterparts

Nickel complexes have recently been presented as prospective catalytic materials for hydrogen H₂ evolution by hydrolysis of sodium borohydride NaBH₄. An attractive complex is nickel hydrazine nitrate [Ni(N₂H₄)₃][NO₃]₂ for which little variations in the synthesis procedure result in different morphologies like hexagonal plates, clews and discs. In our conditions, the clews have the better catalytic activity owing to more defects and more active sites. There is an effect of the morphology on the catalytic activity. However, the H₂ evolution curves (regardless the initial morphology) show an induction period during which the complex (purple violet in color) evolves into a catalytically active form (fine black powder). The evolution is featured by changes in morphology and chemical state of nickel. The catalytically active form is even more active than the pristine complex: it shows a higher H₂ generation rate (three times higher in the best case). The starting complexes and the “reduced” counterparts have been then characterized (e.g. SEM, FTIR, XRD, XPS) to better understand the aforementioned evolutions. One of our main conclusions is that there are some marked analogies between our nickel-based catalysts and the much-investigated cobalt-based catalysts.     

Examination of the catalytic effect of Ni,NiCr, and NiV catalysts prepared as thin films by magnetron sputtering process in the hydrolysis of sodium borohydride

In this study, nickel, nickel-chromium alloy, and nickel-vanadium alloy were coated to form a thin film on the slides prepared by magnetron sputtering process, which were used as a catalyst for the hydrolysis of alkaline sodium borohydride. Factors, such as the temperature of the solution, amount of the catalyst, initial pH of the solution and the performance of these catalysts on hydrogen generation rate were investigated using response surface methodology. Moreover, the catalysts were characterized using XRD and FE-SEM/EDS analyses. Utilizing the obtained optimum conditions of the response surface methodology estimation, the maximum hydrogen generation rate was 35,071 mL min⁻¹ g_NiV⁻¹ from NiV catalyst at 60 °C, pH 6, and 1.75 g catalyst conditions. Under the same experiment conditions, the maximum hydrogen generation rates of Ni and NiCr catalyst systems are 28,362 mL min⁻¹ g_Ni⁻¹, and 30,608 mL min⁻¹ gNiCr⁻¹, respectively.     

Hydrogen generation from hydrolysis of concentrated NaBH4 solutions under adiabatic conditions

In this study, catalytic hydrolysis of aqueous solutions of NaBH₄ under isothermal and adiabatic conditions was investigated. A finely dispersed cobalt powder based on titanium oxide was used as a model catalyst. It was determined that catalytic activity of this catalyst practically did not change after 20 cycles. It was shown that the activation energy, determined by the rate of hydrogen generation, depends on NaBH₄ concentrations. We believe that this effect is associated with sorption/desorption processes. If to conduct hydrolysis under conditions close to adiabatic, the time of hydrolysis is significantly reduced. As united solution of equations of kinetics and energy conversation shows, the data of experiments in a thermally insulated reactor can be reasonably predicted.     

Hydrogen generation from sodium borohydride solution using a ruthenium supported on graphite catalyst

The catalyst with high activity and durability plays a crucial role in the hydrogen generation systems for the portable fuel cell generators. In the present study, a ruthenium supported on graphite catalyst (Ru/G) for hydrogen generation from sodium borohydride (NaBH₄) solution is prepared by a modified impregnation method. This is done by surface pretreatment with NH₂ functionalization via silanization, followed by adsorption of Ru (III) ion onto the surface, and then reduced by a reducing agent. The obtained catalyst is characterized by transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). Very uniform Ru nanoparticles with sizes of about 10 nm are chemically bonded on the graphite surface. The hydrolysis kinetics measurements show that the concentrations of NaBH₄ and NaOH all exert considerable influence on the catalytic activity of Ru/G catalyst towards the hydrolysis reaction of NaBH₄. A hydrogen generation rate of 32.3 L min⁻¹ g⁻¹ (Ru) in a 10 wt.% NaBH₄ + 5 wt.% NaOH solution has been achieved, which is comparable to other noble catalysts that have been reported.     

Electrospun carbon nanofiber-encapsulated NiS nanoparticles as an efficient catalyst for hydrogen production from hydrolysis of sodium borohydride

Carbon nanofibers (CNFs) incorporating NiS nanoparticles (NPs), namely NiS@CNFs were prepared by one-step electrospinning and successfully employed as a catalyst for hydrogen production from hydrolytic dehydrogenation of sodium borohydride (SBH). As-prepared NiS@CNFs, composed of polyacrylonitrile (PAN), nickel acetate, and ammonium sulfide, was calcined at 900 °C in argon atmosphere, and characterized using standard surface science techniques. The combined results revealed the growth of NiS NPs inside the CNFs, hence confirmed the presence of elemental Ni, S, and C. The as-prepared NiS@CNFs catalyst has a significantly higher surface area (650.92 m²/g) than the reported value of 376 m²/g. Importantly, this catalyst exhibited a much higher catalytic performance, for H₂ production from SBH, than that of Ni@CNFs, as evidenced by its low activation energy (∼25.11576 kJ/mol) and their R_max values of 2962 vs. 1770 mL/g·min. Recyclability tests on using NiS@CNFs catalyst showed quantitatively production (∼100% conversion) of H₂ from SBH and retained up to 70% of its initial catalytic activity after five successive cycles. The low cost and high catalytic performance of the designed NiS@CNFs catalyst enable facile H₂ production from readily available hydrogen storage materials.     

Hydrogen generation from aqueous acid-catalyzed hydrolysis of sodium borohydride

In this study, the hydrogen feed from both Ru-catalyzed and organic acid-catalyzed hydrolysis of NaBH₄ was studied in terms of hydrogen generation rate and integrated PEMFC performance. Hydrogen feed generated from the conventional Ru-catalyzed hydrolysis of NaBH₄ caused a drastic loss of PEMFC performance. It was found that the presence of sodium ion in hydrogen feed was a main factor that increased the interfacial resistance of fuel cell and, consequently, reduced the performance. Acid-catalyzed hydrolysis with powder form of NaBH₄ was adopted in order to minimize the detrimental effect of sodium ion. The hydrogen feed from acid-catalyzed hydrolysis was quite dry so that even water vapor, the carrier of sodium ion, was not detected after condensation of hydrogen feed. It was confirmed by the several experiments that the hydrogen release rate can be controlled by varying the injection rate and concentration of aqueous acid. Various organic acids were employed in the production of hydrogen and found that acidity, acid type and chemical structure are also important factors on hydrolysis of NaBH₄. The performance from the integrated acid-catalyzed hydrogen generation system with PEMFC was quite stable and no significant loss was observed contrary to that from the integrated Ru-catalyzed hydrogen generation system–PEMFC test. This result also clarified that the detrimental effect of sodium ion could be removed by minimizing the water vapor in this manner. Based on the experiment of acid-catalyzed hydrolysis, a small-scale hydrogen-generating device was designed and fabricated, from which hydrogen release was controlled by the acid concentration and injection rate of aqueous acid solution.