A novel Microcystis aeruginosa supported manganese catalyst for hydrogen generation through methanolysis of sodium borohydride

In this study, Microcystis Aeruginosa (MA)- microalgae species was used for the first time as a support material with metal ions loading to fabricate a highly efficient catalyst for the hydrogen generation through methanolysis of sodium borohydride (NaBH₄). Microalgae was pre-treated with hydrochloric acid (3 M HCl) for 24 h at 80 °C. Subsequently, different metal ions (Mn, Co, and Mo) were loaded to the pre-treated samples. Finally, metal-loaded samples were subjected to burning in oven to fabricate the catalyst. Primarily, manganese metal was selected based on the best metal performance. Afterwards, different metal loading ratios, burning temperatures and burning times were evaluated to synthesize the optimal MA-HCl-Mn catalyst. Results showed the optimal conditions as Mn ratio, burning temperature and time as 50%, 500 °C and 45 min, respectively. To characterize the catalyst, FTIR, SEM-EDX, XRD, XPS and TEM analyses were performed. Hydrogen generation via methanolysis was performed at various NaBH4 ratio of 1–7.5% while changing concentrations from 0.05 to 0.25 g catalysts with diverge temperatures of (30, 40, 50 and 60 °C). The maximum hydrogen generation rate (HGR) by this novel catalyst was found as 4335.3, 5949.9, 7649.4 and 8758.9 mLmin⁻¹gcat⁻¹, respectively. Furthermore, the activation energy was determined to be 8.46 kJ mol⁻¹.     

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.     

A novel hazelnutt bagasse based activated carbon as sodium borohydride methanolysis and electrooxidation catalyst

In this study, activated carbon is produced from defatted hazelnut bagasse at different activation conditions. The catalytic activities of activated carbons are evaluated for NaBH₄ methanolysis and electrooxidation. These materials are characterized by N₂ adsorption-desorption, FTIR, SEM-EDS and XPS and results show that these materials are prepared successfully. N₂ adsorption-desorption results reveal that activated carbon (FH3-500) has the highest BET surface area as 548 m²/g, total pore volume as 0.367 cm³/g and micropore volume as 0.205 cm³/g. On the orher hand, as a result of hydrogen production studies, FH3-500 activated carbon catalyst has the highest initial hydrogen production rate compared to other materials. At 50 °C, this metal-free activated carbon catalyst has a high initial hydrogen production rate of 13591.20 mL/min.g_cat, which is higher than literature values. Sodium borohydride electrooxidation measurements reveal that FH2-500 also has the highest electrocatalytic activity and stability. Hazelnut pulp-based activated carbons are firstly used as a metal-free catalyst in the methanolysis and electrooxidation of sodium borohydride, and its catalytic activity is good as a metal-free catalyst. The results show that the hazelnut pulp-based activated carbon catalyst is promising as a metal-free catalyst for the methanolysis and electrooxidation of sodium borohydride.     

Evaluating organic waste sources (spent coffee ground) as metal-free catalyst for hydrogen generation by the methanolysis of sodium borohydride

In this study, organic waste sources (spent coffee ground (SCG)) is used as metal-free catalyst in comparison with conventional noble-metal catalyst materials for hydrogen generation based on the methanolysis of sodium borohydride solution. Spent coffee ground (SCG) is used as a metal-free catalyst for the first time as treated with different chemicals. The aim is to synthesize the metal-free catalyst that can be used for the production of hydrogen, a renewable energy source. SCG, which was collected from coffee shops, was used for preparing the catalyst. To produce hydrogen by sodium borohydride (NaBH₄) methanolysis, SCG is pretreated with different chemical agents (H₃PO₄, KOH, ZnCl₂). According to the acid performances, the choice of phosphoric acid was evaluated at different mixing ratios (10%, 20%, 30%, 40%, 50%, 100%) (w/w), different temperatures (200, 300 and 400 °C) and burning times (30, 45, 60 and 90 min) for the optimization of SCG-catalyst. A detailed characterization of the samples were carried out with the aid of FTIR, SEM, XRD and BET analysis. In this study, the experiments were generally carried out effectively under ambient temperature conditions in10 ml methanol solution containing 0.025 g NaBH₄ and 0.1 g of the catalyst. The hydrogen obtained in the experimental studies was determined volumetrically by the gas measurement system. When evaluating the hydrogen volume, different NaBH₄ concentrations, catalyst amount and different temperature effects were investigated. The effect of the amount of NaBH₄ was investigated with 1%, 2.5%, 5%, and 7.5% ratio of NaBH₄ while the influence of the concentration of catalyst was carried-out at 0.05, 0.1, 0.15, and 0.25 g catalysts. Four different temperatures were tested (20, 30, 40, 50 and 60 °C) to explore the performance of the catalyst under different temperatures. The experiments by using SCG-catalyst treated with H₃PO₄ reveal that the best acid ratio was 100% H₃PO₄. The maximum hydrogen production rate with the use of SCG-catalyst for the methanolysis of NaBH₄ was found to be 8335.5 mL min⁻¹gcat⁻¹. Also, the activation energy was determined to be 9.81 kJ mol⁻¹. Moreover, it was discovered that there was no decline in the percentage of converted catalyst material.     

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.     

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.     

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.     

Pd-C powder and thin film catalysts for hydrogen production by hydrolysis of sodium borohydride

In this work we study the hydrogen generation by catalytic hydrolysis of alkaline _NaBH4${\mathrm{NaBH}}_4$ solution employing Pd-supported on carbon powder (Pd/C) as well as in form of Pd and Pd–C thin films synthesized by pulsed laser deposition (PLD). Two sets of samples were prepared: (1) pure Pd catalyst films which were bombarded with Ar⁺${\mathrm{Ar}}^{+}$ ions at different ions fluence in order to increase the surface roughness; (2) highly irregular C film were deposited by using different Ar pressure in the PLD chamber prior to deposition of the Pd film to further increase the surface area for the active Pd catalyst. Surface morphology was studied by using scanning electron microscopy (SEM) and atomic force microscopy (AFM) while compositional analysis was performed by using energy dispersive spectroscopy (EDS). Cone like structure on the surface of the Pd film developed by Ar⁺${\mathrm{Ar}}^{+}$ ion bombardment was not efficient to enhance the catalytic activity of the Pd. Pd/C films showed higher catalytic activity in comparison to Pd/C powders when the same amount of catalyst is used. The results are discussed in relation to the morphology of the C-films.     

Stability of alkaline aqueous solutions of sodium borohydride

Experimental results regarding long-term stability of the alkaline-water borohydride solutions for hydrogen generation are presented. The influence of the concentration of sodium borohydride and sodium hydroxide on the rate of borohydride hydrolysis is analyzed at various temperatures, such as 25 °C, 40 °C, and 80 °C, and various concentrations of NaOH. The rate of hydrolysis decreases with the increase of the water to sodium borohydride mole ratio. For diluted solutions at H₂O/NaBH₄ >30, the rate of hydrolysis and hydrogen generation at a given temperature remains constant. At room temperature in 1.0 N NaOH, the degree of hydrolysis is 0.01% NaBH₄/h that meets the stability requirements for the borohydride solutions during the long-term storage.     

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.     

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 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.     

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.     

Water consumption during solid state sodium borohydride hydrolysis

In this paper nickel acetate catalyzed sodium borohydride cartridges have been prepared and hydrolyzed with water for hydrogen production. Two technological solutions have been tested to increase the overall hydrogen yield, namely a porous water diffuser and a hydrophobic membrane. The first was used to improve water diffusion inside the hydride while the second to confine water inside the cartridge. The generated hydrogen flow showed a very reproducible behavior. Hydrogen promptly evolved just after water was pumped into the cartridge. After some initial peaks, a constant hydrogen flow has been recorded for the whole reaction time. The constant flow was related to the presence of the porous diffuser. The use of a hydrophobic membrane to confine the water inside the cartridge allowed to increase the overall hydrogen yield: about 6 water molecules per mol of hydride were required to complete the reaction. The reaction product was identified by XRD as Na₂B₂O₄*8H₂O. The cartridge hydrogen gravimetric content, based on water and sodium borohydride weight, was as high as 4.64%.     

Hydrogen generation and storage from hydrolysis of sodium borohydride in batch reactors

The catalytic hydrolysis of alkaline sodium borohydride (NaBH₄) solution was studied using a non-noble; nickel-based powered catalyst exhibiting strong activity even after long time storage. This easy-to-prepare catalyst showed an enhanced activity after being recovered from previous use. The effects of temperature, NaBH₄ concentration, NaOH concentration and pressure on the hydrogen generation rate were investigated. Particular importance has the effect of pressure, since the maximum reached pressure of hydrogen is always substantially lower than predictions (considering 100% conversion) due to solubility effects. The solubility of hydrogen is greatly enhanced by the rising pressure during reaction, leading to storage of hydrogen in the liquid phase. This effect can induce new ways of using this type of catalyst and reactor for the construction of hydrogen generators and even containers for portable and in situ applications.     

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.