Sodium Borohydride Solution Research Articles

Development of Al2O3 carrier-Ru composite catalyst for hydrogen generation from alkaline NaBH4 hydrolysis

A recyclable and reusable Ru/Al2O3 catalyst is prepared for hydrogen generation from the hydrolysis process of alkaline sodium borohydride (NaBH4) solution. The hydrogen generation rate by the hydrolysis and methanolysis of alkaline NaBH4 was explored as a function of NaOH concentration. Meantime, the byproducts derived from the spent alkaline NaBH4 solution were characterized by X-ray diffraction (XRD), scanning electro microscope/energy dispersive spectrometer (SEM/EDS) and NMR (Nuclear Magnetic Resonance). The effect of NaOH concentration on the hydrogen generation from the hydrolysis of NaBH4 significantly depends on the type of catalysts. With increasing NaOH concentration, the hydrogen generation rates decrease when using ruthenium (Ru) composite as a catalyst. The hydrogen generation rate of the methanolysis of NaBH4 is significantly inhibited in the presence of NaOH as compared with the hydrolysis of NaBH4. The durability test of the Ru/Al2O3 catalyst shows that the hydrogen generation rate decreases with recycling and reuse. The XRD and NMR analysis results show that the borate hydrate (NaBO2 H2O) was derived from the hydrolysis of 20 wt% and 30 wt% NaBH4.

Effect of bath composition on properties of electroless deposited Co–P/Ni foam catalyst for hydrolysis of sodium borohydride solution

Abstract The effect of bath composition on the properties of electroless deposited Co–P/Ni foam catalyst for hydrolysis of sodium borohydride solution was investigated by varying the bath composition. The NaH2PO2/CoCl2 and NH2CH2COOH/CoCl2 concentration ratio had a strong effect on the catalyst properties. The effect of NH2CH2COOH/CoCl2 was larger than that of NaH2PO2/CoCl2 for the concentration ratio range with practical deposition rates. The optimum concentration ratio of the coating bath was CoCl2:NH2CH2COOH:NaH2PO2 = 1:4:10. As the concentration of each component increased at the optimum concentration ratio, the coating bath decomposed on its own. As the amount of solute dissolved in the coating bath increased, the coating bath became unstable. The optimum composition of the stable coating bath to realize Co–P/Ni foam catalyst with good catalytic activity was 0.1 m (molality, mol/kg) CoCl2, 0.4 m NH2CH2COOH, and 1.0 m NaH2PO2. The weight percent of the deposited catalyst and hydrogen generation rate per deposited catalyst of 1 g at optimum composition were 8.39 wt% and 0.93 L/min·g (deposited catalyst), respectively. The bath composition was found to have a great effect on the Co–P/Ni foam catalyst properties and coating bath stability.

Effect of manufacturing conditions on properties of electroless deposited Co–P/Ni foam catalyst for hydrolysis of sodium borohydride solution

The effects of the deposition time and coating bath with various pH and temperatures on the deposition rate, hydrogen generation rate per deposited catalyst of 1 g, surface morphology, catalyst particle distribution, and microstructure of electroless deposited Co–P/Ni foam catalysts were investigated. The degree of the effects of the parameters was in the following order: pH > temperature > deposition time. The effects of heat treatment temperature on the durability and catalytic activity were also investigated. Durability increased slightly in response to heat treatment, but hydrogen generation reduced owing to sodium sintering and oxide film formation. The optimum conditions were 12.0 (pH), 50 °C (temperature), and 30 min (deposition time) without heat treatment. The weight percent of the deposited catalyst and hydrogen generation rate per deposited catalyst of 1 g under the optimum conditions were 4.86 wt% and 1.49 L/min g (deposited catalyst), respectively. The apparent activation energy of the catalyst manufactured under the optimum conditions was 46.8 kJ/mol. The manufacturing conditions considerably affected the catalyst properties.

Influence of acid sites on the propene selectivity during propane dehydrogenation on zeolite Pt/Zn,Na-MCM-22

Several bimetallic Pt/Zn,Na-MCM-22 catalysts were tested for the non-oxidative dehydrogenation of propane. Since acid-catalyzed side reactions in the large cavities of the MCM-22 catalysts play an important role here, several methods for decreasing the concentration of acid sites were tried. The most successful technique was the reduction of the metals with aqueous sodium borohydride solution instead of hydrogen, which led to a significantly increased yield of propene.

Hydrogen generation with sodium borohydride solution by Ru catalyst

SUMMARY High-purity hydrogen generated by the hydrolysis of sodium borohydride can be used as proton exchange membrane fuel cells (PEMFCs) for portable device applications. Because of its advantages in high storage capacity, controllable reaction, and mild condition, hydrogen generation by catalytic hydrolysis of a chemical hydride, such as sodium borohydride, has recently attracted much attention for development. Hydrogen generated by the hydrolysis of sodium borohydride using a Ru catalyst is reported in the present study. A multi-layer coating process was used on the Ru/Ni foam catalyst to enhance the cycling generation. The optimal deposition density of the Ru particle on Ni foam was confirmed by SEM morphology. The cycling generation for the steady state reaction can be maintained at least 10 times, and gradually decreases to 82% performance after the 17th cycling generation. It was found that a combination of 20 wt% NaBH4 solution concentration and 3 wt% NaOH yields the highest performance for hydrogen generation. A hydrogen generation efficiency of 95% was obtained for a solution with a 1-g/min flow rate flowing onto the 6-cm2 area of a catalyst plate, which had a hydrogen generation rate of 0.45 L/min. As the solution flow rate was increased, the reaction efficiency decreased because of the decreased reaction time. Hydrogen fuel saturated with water generated by a NaBH4 solution shows an advantage over that from a gas cylinder for fuel cell operation. A PEM fuel cell was integrated with the hydrogen generator in the present study. The hydrogen fuel from the hydrogen generator with saturated water vapor showed a better cell performance compared with using hydrogen from a gas cylinder. Copyright © 2012 John Wiley & Sons, Ltd.

Efficient Catalytic Reduction of Hexavalent Chromium Using Palladium Nanoparticle-Immobilized Electrospun Polymer Nanofibers

We report a facile and economic approach to fabricating catalytic active palladium (Pd) nanoparticle (NP)-immobilized electrospun polyethyleneimine (PEI)/polyvinyl alcohol (PVA) nanofibers for catalytic reduction of hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)). In this study, PEI/PVA nanofibrous mats were first electrospun from homogeneous mixture solution of PEI and PVA, followed by cross-linking with glutaraldehyde vapor to render the fibers with good water stability. The nanofibrous mats were then alternatively soaked in potassium tetrachloropallidate (K2PdCl4) and sodium borohydride solution, and the PdCl4(2-) anions complexed with the free amine groups of PEI were able to be reduced to form zero-valent Pd NPs. The formed Pd NP-containing PEI/PVA nanofibers were characterized by different techniques. We show that the immobilization of Pd NPs does not significantly change the morphology of the PEI/PVA nanofibers; instead the mechanical durability of the fibers is significantly improved. The formed Pd NPs with a mean diameter of 2.6 nm are quite uniformly distributed within the fibers with a small portion of particles having a denser distribution at the outer surface of the fibers. The catalytic activity and reusability of the fabricated Pd NP-containing fibrous mats were evaluated by transformation of Cr(VI) to Cr(III) in aqueous solution in the presence of a reducing agent. Our results reveal that the Pd NP-containing nanofibrous mats display an excellent catalytic activity and reusability for the reduction of Cr(VI) to Cr(III). The facile approach to fabricating metal NP-immobilized polymer nanofibers with a high surface area to volume ratio, enhanced mechanical durability, and uniform NP distribution may be extended to prepare different NP-immobilized fibrous systems for various applications in catalysis, sensing, environmental sciences, and biomedicine.

Rapid synthesis of Ag nanoparticles-embedded mesoporous silica via solution plasma and its catalysis for 4-nitrophenol reduction

The rapid synthesis of Ag nanoparticles-embedded mesoporous silica (AgNP@SiO2) was completed within a one-pot process in which a discharge occurred in solution of the substances utilized for synthesizing mesoporous silica (tetraethyl orthosilicate (TEOS), P123 block copolymer) and various Ag precursor concentrations (AgNO3: 1, 5, and 10mM). The solidification of the polysilicate network via hydrolysis and condensation during sol–gel reaction could be rapidly achieved after discharge at 3min. The morphology of rope-like particles with hexagonal mesopore arrangements was observed using electron microscopy. The catalytic activity of AgNP@SiO2 particles with high surface areas for 4-nitrophenol reduction was investigated under sodium borohydride (NaBH4) solution with reaction time dependence. The results showed that reduction of concentrated 4-nitrophenol (0.25mM) was completed at 12min using AgNP@SiO2 from 10mM Ag precursor.

High performance and eco-friendly chitosan hydrogel membrane electrolytes for direct borohydride fuel cells

Novel, cost-effective, and environmentally benign polymer electrolyte membranes (PEMs) consisting of ionically cross-linked chitosan (CS) hydrogel is reported for direct borohydride fuel cells (DBFCs). The membranes have been prepared by ionic cross-linking of CS with sulfate and hydrogen phosphate salts of sodium. Use of Na2SO4 and Na2HPO4 as cross-linking agents in the preparation of ionically cross-linked CS hydrogel membrane electrolytes (ICCSHMEs) not only enhances cost-effectiveness but also environmental friendliness of fuel cell technologies. The DBFCs have been assembled with a composite of nickel and carbon-supported palladium as anode catalyst, carbon-supported platinum as cathode catalyst and ICCSHMEs as electrolytes-cum-separators. The DBFCs have been studied by using an aqueous alkaline solution of sodium borohydride as fuel in flowing mode using a peristaltic pump and oxygen as oxidant. A maximum peak power density of about 810mWcm−2 has been achieved for the DBFC employing Na2HPO4-based ICCSHME and operating at a cell temperature of 70°C.

Investigation into Hydrolysis of Alkaline Sodium Borohydride Solution Using Attapulgite Clay-Supported Co-B-Ce Catalyst

Hydrolysis of sodium borohydride is regarded as a promising technology to produce pure hydrogen in portable fuel cell fields. In this paper, Ce is examined to be a better co-catalyst than Ni and Fe for the attapulgite clay (AT)-supported cobalt-boride (Co-B) catalyst. Factors, such as solution temperature, NaBH4 concentration and NaOH concentration on performance of these catalysts in hydrolysis of sodium borohydride are investigated. Furthermore, characteristics of these AT-supported catalysts are studied using SEM and XRD. Activation energy of hydrogen generation using such catalysts is estimated to be 37.02 kJ/mol.

Reduction of aromatic nitro compounds on colloidal hollow silver nanospheres

Hollow silver nanospheres colloids were successfully prepared by a simple reaction of silver nitrate (AgNO3), sodium hydroxide (NaOH) and hydroxylammonium hydrosulfate ((NH2OH)2·H2SO4) in the presence of gelatin. Formations of colloidal hollow silver nanospheres were observed by UV–vis absorption spectroscopy, particle size analyzer and transmission electron microscopy (TEM) and X-ray diffraction (XRD). Dispersion destabilization of nanospheres colloids was detected by Turbiscan. Superior catalytic performance was observed in a test reaction of 4-nitrophenol (4-NP) and 4-nitroaniline (4-NA) reduction in the presence of freshly prepared ice cold aqueous solution of sodium borohydride (NaBH4) at room temperature. The reduction process was monitored by UV–vis absorption spectroscopy. The reaction followed pseudo-first order kinetics with respect to nitro compound and the rate constant was found to be larger compared to other silver catalyst used for the reduction reaction.

Photoluminescence of oxidized porous silicon treated by sodium borohydride aqueous solution

Alkaline solutions are usually used to remove porous layer from porous silicon. However, novel star-like photoluminescent oxidized porous silicon (PS) particles have been successfully fabricated in sodium borohydride (NaBH4) solution in this work. It is interesting that porous layer has been oxidized in NaBH4 alkaline solution, rather than being removed. Silicon oxide is formed due to the constant reactions of silicon nanocrystals and NaOH. Then these oxides are adjusted to star-like morphology by the pressure of H2. Both NaOH and H2 are generated from the hydrolysis of NaBH4. Oxidized PS shows bright orange photoluminescence (PL) at 550nm. This emission can be simply tuned into red or blue by illumination of high pressure mercury lamp or high temperature treatment. The PL of NaBH4-treated PS is originated from quantum confinement and surface state of silicon nanocrystallites.

Tin content determination in canned fruits and vegetables by hydride generation inductively coupled plasma optical emission spectrometry.

Tin content in samples of canned fruits and vegetables was determined by hydride generation inductively coupled plasma atomic emission spectrometry (HG-ICP-OES), and it was compared with results obtained by standard method of flame atomic absorption spectrometry (AAS). Selected tin emission lines intensity was measured in prepared samples after addition of tartaric acid and followed by hydride generation with sodium borohydride solution. The most favorable line at 189.991 nm showed the best detection limit (1.9 μg L−1) and limit of quantification (6.4 μg kg−1). Good linearity and sensitivity were established from time resolved analysis and calibration tests. Analytical accuracy of 98–102% was obtained by recovery study of spiked samples. Method of standard addition was applied for tin determination in samples from fully protected tinplate. Tin presence at low-concentration range was successfully determined. It was shown that tenth times less concentrations of Sn were present in protected cans than in nonprotected or partially protected tinplate.

Water Dispersible Ru (0) Nanorods: A Highly Efficient Heterogeneous Catalyst for the Hydrogen Generation from Sodium Borohydride Solutions

Water-dispersible Ru (0) nanorods stabilized by Poly (N-vinyl-2-pyrrolidone) (PVP) were employed as catalyst in the hydrolysis of sodium borohydride (NaBH4). The hydrogen generation rate was determined as a function of solution temperature, NaBH4 concentration, and catalyst amount. Ru (0) nanorods were found to be highly active catalysts even at room temperature. Kinetics study indicated that the hydrolysis reaction was first order in catalyst concentration and zeroth order in substrate concentration. The activation parameters of the hydrolysis reaction were also determined from the evaluation of the kinetic data. The PVP-stabilized Ru (0) nanorods provided a lower apparent activation energy (Ea = 33.4 ± 1 kJ/mol) than bulk Ru(0) metal and other reported Ru-based supported catalysts for the hydrolysis of NaBH4.

Influence of different types of stabilisers on the properties of silver nanoparticles suspension

In this Letter some effects of different type of stabilisers on physicochemical properties of silver nanoparticles (AgNPs) have been presented. The AgNPs were prepared by reduction method with some modifications. A sodium borohydride solution was added drop-wise (∼1 drop/s) to a solution of silver nitrate. The reaction mixture was stirred vigorously on a magnetic stirrer plate at room temperature for 15 min. The synthesis method developed for this experiment and conducted in exactly controlled conditions produces monodispersed AgNPs. In this study the solutions of tri-sodium citrate dihydrate, C6H5Na3O7·2H2O; polyvinyl alcohol (C2H4O)n and poly(N-vinylpyrrolidone) (C6H9NO)n with different concentrations were prepared by dissolving appropriate for the experiment amount of stabiliser in doubly distilled water. For nanostructure identification dynamic light-scattering measurements, UV–vis spectroscopy as well as scanning electron microscopy with ‘back scattered electron’ detector and energy dispersive X-ray spectroscopy has been applied. It was found that type of stabiliser was playing an important role in the formation of the silver nanostructures.

Electrical and Thermal Behavior of Copper‐Epoxy Nanocomposites Prepared via Aqueous to Organic Phase Transfer Technique

The preparation, electrical, and thermal behaviors of copper‐epoxy nanocomposites are described. Cetyltrimethylammonium bromide‐ (CTAB‐) stabilized copper (Cu) particles were synthesized via phase transfer technique. Isopropanol (IPA), sodium borohydride (NaBH4), and toluene solution of diglycidyl ether of bisphenol A (DGEBA) were used as transferring, reducing agent, and the organic phase, respectively. The UV‐Vis absorbance spectra of all the sols prepared indicate that the presence of Cu particles with the particles transfer efficiency is ≥97%. The amount, size, and size distribution of particles in the organosol were dependent on the content of organic solute in the organosol. The composites were obtained upon drying the organosols and these were then subjected to further studies on the curing, thermal, and electrical characteristic. The presence of Cu fillers does not significantly affect the completeness of the composite curing process and only slightly reduce the thermal stability of the composites that is >300°C. The highest conductivity value of the composites obtained is 3.06 × 10−2 S cm−1.

Novel Naphthalene-Based Open Chain Crown Ether: Synthesis and Crystal Structure

A novel naphthalene-based open-chain crown ether has been synthesized by the etherification of 2-bromo- N-phenylacetamide with 3,6-dibromo-2,7-dihydroxynaphthalene, followed by reduction with sodium borohydride and boron trifluoride ether solution, in 95% total yield. Its crystal structure was determined by X-ray diffraction method. The crystal is of triclinic space group P-1 with a=9.588(3) A, b=10.898(3) A, c=13.060(4) A, α=103.190(4)°, β=93.953(4)°, γ= 115.622(5)°, V=1176.0(6) A 3 , Z=2, Dc=1.571 g/cm 3 , λ=0.71075 A, μ(Mo Kα)=3.472 mm -1 , Mr=353.22 and F(000)= 560. In the structure, one of the N—H groups forms bifurcated N—H…Br and N—H…O hydrogen bonds. These link the molecules into inversion related dimers. The centrosymmetric dimers are aggregated via pairs of C—H…π interactions into two-dimensional sheets parallel to (110). Keywords open-chain crown ethers; synthesis; crystal structure

Advances in producing cost-effective direct borohydride fuel cells and road to its commercialization

A direct borohydride fuel cell (DBFC) converts chemical energy stored in borohydride ion (BH4-) and an oxidant directly into electricity by redox processes. Usually, a DBFC employs an alkaline solution of sodium borohydride (NaBH4) as fuel and oxygen or hydrogen peroxide as oxidant. Some of the attractive features in DBFC include high open circuit potential, ease of electro-oxidation of BH4- on non-precious metals, such as nickel, low operational temperature and high power density. The DBFC is a promising power system for portable applications. The biggest barriers to its commercialization are its high cost and long-term stability. This paper discusses some of the recent advances made in reducing the cost of DBFC. The technology is reaching a point where it could soon be commercialized. The effect of the reduced cost on its commercialization is discussed in this paper.

Hydrolysis of aqueous-alkaline solutions of sodium borohydride. Asymptotics of low concentrations of the alkali

Distinctive features of modeling the kinetics of the hydrolysis of aqueous-alkaline solutions of sodium borohydride taking account of the change in the pH of the solutions investigated are described.

Effects of the Pre-Freezing Time on the Structures and Electrochemical Performances of Co-B Alloys

A series of Co-B alloys with uniform nanoparticles were prepared via a vacuum freeze-drying method, which the precursors of Co-B alloys were prepared by the reduction of bivalent cobalt chloride with aqueous sodium borohydride solution. The alloys were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and brunauer emmett teller (BET) surface area measurement. The electrochemical activities of Co-B samples were examined by charge-discharge test. This work studied the influence of pre-freezing time on the microstructure and electrochemical performance. The sample pre-freezing for 3 hours exhibits the best cycling performance than others, the discharge capacity increase to its maximum 438mAh/g, and it still remained 232 mAh/g after 60 cycles at a current of 50 mAh/g; while those of samples pre-freezing for 1 hour and 5 hours are 399 mAh/g and 413mAh/g, respectively.

Design and development of a fuel cell-powered small unmanned aircraft

The design, construction, and flight test of a fuel cell-powered small unmanned aircraft are described. A fuel cell system featuring a polymer electrolyte membrane fuel cell combined with a hydrogen generator, which serves as a new power source alternative to the existing batteries, is proposed. The hydrogen generator uses a catalytic hydrolysis reaction to extract hydrogen from an alkaline solution of sodium borohydride, and constructed with a reactor, pump, separator, and fuel cartridge. Considering the performance characteristics of the fuel cell, the hybrid power management of a fuel cell and a battery was contrived. The fuel cell stack, hydrogen generator, and power management system were evaluated at the various load conditions. A high efficiency unmanned aircraft was designed and fabricated to validate the possibility of the proposed fuel cell system, and a small flight control system was developed for a high endurance test flight. Wind-tunnel tests were conducted before the flight tests under actual flight conditions. The possibility for the utilization of a fuel cell in a small aircraft was validated through the fuel cell powered flight test. The fuel cell aircraft flew for 2 h without incidents in the fuel cell system.