Salicylaldimine-Ni complex supported on Al2O3: Highly efficient catalyst for hydrogen production from hydrolysis of sodium borohydride

In this study, the Ni-based complex catalyst containing nickel of 1% supported on Al₂O₃ is used as for the hydrogen production from NaBH₄ hydrolysis. The maximum hydrogen production rate from hydrolysis of NaBH₄ with Ni-based complex catalyst supported on Al₂O₃ containing nickel of 1% is 62535 ml min^?1 g^?1 (complex catalyst containing 1 wt% Ni). The resulting complex catalyst is characterised by XRD, XPS, SEM, FT-IR, UV, and BET surface area analyses. The Arrhenius activation energy is found to be 27.29 kJ mol^?1 for the nickel-based complex catalyst supported on Al₂O₃. The reusability of the catalyst used in this study has also been investigated. The Ni-based complex catalyst supported on Al₂O₃ containing nickel of 1% is maintained the activity of 100% after the fifth use, compared to the first catalytic use. The n value for the reaction rate order of NaBH₄ is found to be about 0.33.     

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.     

New reactor design for catalytic sodium borohydride hydrolysis

Hydrogen supply to a fuel cell for portable consumer products requires a simple and safe technology for its storage and on-demand production. Hydrogen production by hydrolysis of sodium borohydride solution in the presence of metal catalyst could be a promising and feasible method.     

Exploring the technological maturity of hydrogen production by hydrolysis of sodium borohydride

Sodium borohydride NaBH₄ (SB) has been rediscovered in the late 1990s and been presented as a promising hydrogen storage material owing to its high gravimetric hydrogen density of 10.8 wt% and ability to produce H₂ by hydrolysis at ambient conditions. This looked promising, but soon hydrolysis of SB encountered numerous obstacles. In 2015, a progress report (Int J Hydrogen Energy 2015; 40:2673–91) showed that the 2000–2014 research did not overcome all of the obstacles, making SB far from being technologically mature. Eight years have passed since 2015. Have we put more effort into all aspects relating to hydrolysis of SB? If so, do we have produced scaled-up technologies and prototypes, of which we would have a better knowledge? Have we been able to gain in technological readiness level? Answering these questions is the main objective of this article. A secondary objective is to summarize the newly acquired knowledge. Five main observations stand out. First, the 2015–2022 period is regrettably similar to the 2000–2014 since, again, catalysts have dominated the field and the other aspects (e.g. recycling of the by-product to regenerate SB, scale-up and implementation) have received little attention. Second, hydrolysis of SB still runs into numerous obstacles, some of the obstacles being known since a long time and other ones being relatively new and unknown. Third, there has been little gain in terms of technological readiness level while few research groups have shown that there is room for new ideas and innovation. Fourth, energy, exergy and economic analyses are needed to evaluate the overall cost of H₂ from SB. Fifth, SB has not effectively thought from the end user perspective. In conclusion, many obstacles remain to be overcome before hydrolysis of SB can be a commercial solution for carrying and producing H₂. However, all efforts should be dedicated to (i) construct, operate and optimize H₂ production systems (i.e. prototypes and demonstrators), (ii) handle SB at the gram-to-kilogram scale, (iii) make production of SB even more efficient, and (iv) overcome all obstacles while thinking from the end user perspective.     

Investigation on the effect of synthesizing temperature on the catalytic activity of nickel cobalt boron catalysts in sodium borohydride hydrolysis process

Hydrogen production through the reaction between sodium borohydride (NaBH₄) and water in presence of three different catalysts including; NiB, CoB and NiCoB is studied. The catalysts are synthesized by chemical reduction method at room and 0 °C temperature. The products are characterized by X-Ray Diffraction (XRD), High-Resolution Scanning Electron Microscopy (HRSEM) and Inductively Coupled Plasma-optical emission spectroscopy (ICP). The results showed that carrying out synthesizing process at low temperature, causes decreasing the nuclei size and reducing driving force for the growth stage, and results in a meaningful reduction in size of the produced catalysts particles. Furthermore, it leads to a recognizable change in particles shape to fine spherical with definite boundaries and slightly increase in boron content of each catalyst. These changes, especially in size and shape of the produced catalysts, results in an improvement in catalytic activity of the synthesized catalysts and the rate of hydrogen generation through using them. This achievement were successfully proved for all three NiB, CoB and NiCoB catalysts, although it was more pronounced for CoB so that it was possible to produce 1.4 lit hydrogen in less than 13 s (12,923 ml·min^?1.g^?1_catalyst) by using 0.5 g of CoB catalyst synthesized at 0 °C.     

Kinetics of Ru-catalyzed sodium borohydride hydrolysis

Chemical hydrides have been identified as a potential medium for on-board hydrogen storage, one of the most challenging technical barriers to the prospective transition from gasoline to hydrogen-powered vehicles. Systematic study of the feasibility of the sodium borohydride systems, and chemical-hydride systems more generally, requires detailed kinetic studies of the reaction for use in reactor modeling and system-level experiments. This work reports an experimental study of the kinetics of sodium borohydride hydrolysis with a Ru-on-carbon catalyst and a Langmuir-Hinshelwood kinetic model developed based on experimental data. The model assumes that the reaction consists of two important steps: the equilibrated adsorption of sodium borohydride on the surface of the catalyst and the reaction of the adsorbed species. The model successfully captures both the reaction's zero-order behavior at low temperatures and the first-order behavior at higher temperatures. Reaction rate constants at different temperatures are determined from the experimental data, and the activation energy is found to be 66.9 kJ mol⁻¹ from an Arrhenius plot.     

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.     

Preparation of pompon-like Co-B nanoalloy by a room-temperature solid-state-reaction as a catalyst for hydrolysis of borohydride solution

Pompon-like Co-B alloy composed of nanosheets with a large specific surface area of 202.4 m² g^?1 was synthesized via a facile room-temperature solid-state-reaction. By changing the mass ratios of CoCl₂·6H₂O to CO(NH₂)₂ in the synthesis, the morphology of the Co-B alloy can be controlled. Correspondingly, the specific surface area can increase from ca. 43.4–202.4 m² g^?1. When the pompon-like Co-B severs as a catalyst for the hydrolysis of NaBH₄, the hydrogen generation rate can be up to $8\text{.}26{\text{L}}_{\text{hydrogen}}{\text{min}}^{\mathrm{?}1}{{\text{g}}_{\text{catalyst}}}^{\mathrm{?}1}$. This value is larger compared with those of many other Co-B nanoalloys in previous reports. Additionally, the corresponding activated energy for the hydrolytic reaction is as low as 25 kJ mol^?1, hinting that the pompon-like Co-B catalyst possesses superior catalytic performance. The pompon-like Co-B alloy has the advantages of low cost, good recoverability, as well as high activity, which may find practical application in NaBH₄ hydrolysis for hydrogen production.     

New insights on the mechanism of vapour phase hydrolysis of sodium borohydride in a fed-batch reactor

This study aims to produce H₂ from sodium borohydride (NaBH₄) and to initiate its hydrolysis at elevated temperature in the absence of a catalyst. Experimental results indicated that the hydrogen generation yield increased up to %99 at 150 °C in the NaBH₄ concentration of %5 wt in the acidic medium. It can be concluded that experimental characterization of the by-products is quite important since they affected the reaction mechanism or pathway. When the experiments are carried out under aqueous condition, the primary by- product is sodium metaborate while it is boric acid under acidic condition. It is postulated that by-product boric acid decreased the mass transfer limitation due to its higher solubility that prevents the formation of shell and thus increases the contact area between NaBH₄ and vapor. A series of fed-batch reactions were performed to confirm the hypothesis, and the conversions of NaBH₄ reached 99% under the acidic condition.     

Research progress on catalysts for hydrogen generation through sodium borohydride alcoholysis

Hydrogen is a promising energy carrier for realizing the transition from fossil fuels to renewable energy sources. Nowadays, the development of the hydrogen economy faces many challenges connected with its efficient production, storage, distribution, and end-use. During the past decade, the alcoholysis, particularly methanolysis, of sodium borohydride (NaBH₄) has attracted much attention due to the nonflammability, nontoxicity, potential for utilization in cold conditions of the reaction system. Highly efficient catalysts are of great significance to guarantee the efficiency of the reaction and control the hydrogen release. In this review, we summarize recent advances in both metallic and nonmetallic catalysts for the alcoholysis of NaBH₄. This review also summarizes the advantages and disadvantages of various catalysts in the investigations to assess the potential opportunities and challenges for their application in NaBH₄ methanolysis. The catalytic mechanisms related to NaBH₄ methanolysis were also 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.     

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.     

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.     

Co3O4 hollow fiber: An efficient catalyst precursor for hydrolysis of sodium borohydride to generate hydrogen

Sodium borohydride (NaBH₄) is one of promising hydrogen storage materials for practical application, and the development of high-efficient catalysts for NaBH₄ hydrolysis to generate hydrogen is of critical importance. In this communication, Co₃O₄ hollow fiber composed of nanoparticles array was served as catalyst precursor and facilely prepared by combustion method with template of the absorbent cotton. For characterization, FE-SEM, HRTEM, EDS, XRD, FTIR and ICP were applied, respectively, and typical water-displacement method was performed to evaluate the catalytic activity. Using a solution composed of 10 wt% NaBH₄ and 2 wt% NaOH, hydrogen generation rate was up to 11.12 L min^?1 g^?1 (25 °C), which is much higher than that of the commercial cobalt oxides and similar catalyst precursors reported in literature.     

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.