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Abstract: Solid-state NaBH4/Ru-based catalyst composites have been fabricated for hydrogen generation through a high-energy ball-milling process, providing uniform dispersion of resin-supported Ru3+ catalysts among pulverized NaBH4 (SBH) particles, so as to increase the contacts of SBH with active catalytic sites. Consequently, the gravimetric hydrogen storage capacity as high as 7.3wt% could be achieved by utilizing water as a limiting reagent to overcome the issue of deactivated catalysts whose active sites are often blocked by precipitates caused by limited NaBO2 solubility occurring in conventional aqueous SBH systems for hydrogen productions. Products of hydrolyzed SBH that greatly influence the gravimetric H2 storage capacity are found to be most likely NaBO2·2H2O and NaBO2·4H2O from SBH/H2O reacting systems with initial weight ratios, SBH/H2O=1/2 and 1/10, respectively, according to the TGA and XRD analyses. [Copyright &y& Elsevier]

Abstract: A fast and simple fabrication process, viz. a wet-chemical reduction process, was utilized for preparation of a cobalt-based catalyst to be used for hydrogen generation from alkaline NaBH4 solution. Characteristics of this cobalt-based catalyst were carried out by using various instruments, such as SEM/EDS, XPS, ICP, VSM, BET and TGA. The surface chemistry of the obtained catalyst is mainly cobalt oxides, not cobalt borides. Ferromagnetic property of the cobalt-based catalyst makes it convenient for being recycled from spent NaBH4 solution. The rate of hydrogen generation from catalyzed hydrolysis of alkaline NaBH4 solution was determined as a function of temperature, NaBH4 concentration, and NaOH concentration in the presence of prepared catalysts. In general, stable generation rate of highly pure hydrogen near 200mLmin−1 g−1 was achieved in 100mL of 5wt% NaBH4 solution containing 5wt% NaOH solution and 200mg of Co/IR-120 catalyst, in which no temperature runoff was observed during the course of hydrogen production. The activation energy of NaBH4 hydrolysis reaction was found at 66.67kJmol−1, which was comparable with others reported in the open literatures. [Copyright &y& Elsevier]

Abstract: Magnetic nickel–ruthenium based catalysts on resin beads for hydrogen generation from alkaline NaBH4 solutions were synthesized with combined methods of chemical reduction and electroless deposition. Factors, such as solution temperature, NaBH4 loadings, and NaOH concentration, on performance of these catalysts on hydrogen production from alkaline NaBH4 solutions were investigated. Furthermore, characteristics of these nickel–ruthenium based catalysts were carried out by using various instruments, such as SEM/EDS, XPS, SQUID VSM and BET. These catalysts can be easily recycled from spent NaBH4 solution with permanent magnets owing to their intrinsic soft ferromagnetism and, therefore, reducing the operation cost of the hydrogen generation process. A rate of hydrogen evolution as high as ca. 400mL min−1 g−1 could be reached at 35°C in 10wt% NaBH4 solution containing 5wt% NaOH using Ni–Ru/50WX8 catalysts. Activation energy of hydrogen generation using such catalysts is estimated at 52.73kJ mol−1. [Copyright &y& Elsevier]

Preparation and characterization of bimetallic Ni–Co nanoparticle catalysts loaded on the reduced graphene oxide, denoted as Ni–Co/r-GO, for hydrogen generation from catalytic hydrolysis of sodium borohydride were studied. The reduced graphene oxide nanosheets were prepared from natural graphite. The Ni and Co metals were electrolessly deposited on the light-weighted reduced graphene oxide (r-GO) nanosheets. Process parameters affecting the hydrolysis reaction of NaBH 4 in the presence of Ni–Co/r-GO catalysts, such as NaOH and NaBH 4 concentrations, as well as catalyst loadings and reaction temperature, were investigated. A hydrogen production rate as high as ca. 1280 mL min −1 (g cat.) −1 could be obtained using the prepared Ni–Co/r-GO catalysts. The activation energy of the catalytic hydrolysis reaction of sodium borohydride was found at 55.12 kJ mol −1 from the system consisting of 10 wt% NaBH 4 and 5 wt% NaOH as well as a catalyst loading at 0.1 g catalyst per g NaBH 4 . [ABSTRACT FROM AUTHOR]

Abstract: Hydrolysis of sodium borohydride (NaBH4) is a promising method for on-board hydrogen supply to polymer electrolyte membrane fuel cells (PEMFC). This article presents an attempt to design a novel solid-state NaBH4 composite, which is made up of NaBH4 powder, Co2+/IR-120 catalyst and silicone rubber, for hydrogen generator. The silicone rubber can act as a stabilizer in the solid-state NaBH4 composite because of its surface hydrophobicity leading to reduced diffusion rate of water into the composite. The solid-state NaBH4 composite can produce hydrogen stably near 25mLmin−1 for at least 2h without employment of any mechanical control system. Using the hydrogen generated from the solid-state NaBH4 composite, a 2W PEMFC stack is successfully operated to power a cellular phone. [Copyright &y& Elsevier]

Abstract: Solid-state composites of NaBH4 and Co-based catalyst have been fabricated for hydrogen generation via a novel mechanochemical technique, i.e. the high-energy ball milling, in which the gravimetric storage capacity of hydrogen has reached 6.7 wt%, meeting the 2010 target of at least 0.06 kg H2/kg set by the U.S. Department of Energy (DOE). The active catalysts used in the hydrolysis reaction of sodium borohydride for hydrogen generation are mainly cobalt oxides. Controlled addition of water, namely water used as a limiting agent, to the solid composites of NaBH4 and Co-based catalyst greatly improves the H2 storage capacity and resolved the issues of low gravimetric H2 storage in conventional aqueous system of sodium borohydride. Factors influencing the performance of hydrogen production such as amounts of H2O added, catalyst loadings and durations of ball-milling processes are investigated. Moreover the hydrolyzed products of NaBH4 and spent catalysts are analyzed as well. [Copyright &y& Elsevier]

Abstract: High-energy ball milling was employed to regenerate spent-sodium borohydride, i.e., mainly the sodium metaborate (NaBO2), back to sodium borohydride (NaBH4) by a reaction with magnesium hydride (MgH2). The samples were characterized using scanning electron microscopy (SEM), Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy, X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) spectroscopy. In general, as the ball-milling duration increases, the yield of NaBH4 increases accordingly and leads to an extreme value of 76%, when MgH2 in stoichiometric excess by 40% was initially present in ball mills. [Copyright &y& Elsevier]