Influence of process parameters on enhanced hydrogen evolution from alcoholysis of sodium borohydride with a boric acid catalyst

The hydrogen evolution via alcoholysis reaction of sodium borohydride with an H₃BO₃ catalyst was carried out for the first time. In the process of methanol and NaBH₄ (NaBH₄-MR), the effects of the H₃BO₃ and NaBH₄ concentration, and temperature parameters were examined and evaluated. The hydrogen yields by the NaBH₄-MR, NaBH₄ ethanolysis (NaBH₄-ER) and NaBH₄ hydrolysis reactions (NaBH₄-HR) with 0.2 M H₃BO₃ catalyst are 99, 62, and 88% compared to the theoretical hydrogen yield, respectively. The completion times of the NaBH₄-MR using the H₃BO₃ concentrations of 0.2, 0.4, 0.5, 1 M, and saturated acid solution were about 50, 15, 10, 2 and 1 min, respectively. The hydrogen yields obtained with 50, 15, 10, 2, and 1 min for the same acid concentration values were about 100% compared to the theoretical hydrogen value. By increasing the H₃BO₃ concentration from 0.2 M to the saturated H₃BO₃ concentration, the completion time of this NaBH₄-MR process was reduced by approximately 50 times, resulting in a significant result. The activation energy (Ea) of the NaBH₄-MR with the H₃BO₃ catalyst was 57.3 kJ/mol.     

Kinetics of hydrolysis of sodium borohydride for hydrogen production in fuel cell applications: A review

Hydrogen generation from the hydrolysis of sodium borohydride (NaBH₄) solution has drawn much attention since early 2000s, due to its high theoretical hydrogen storage capacity (10.8 wt%) and potentially safe operation. However, hydrolysis of NaBH₄ for hydrogen generation is a complex process, which is influenced by factors such as catalyst performance, NaBH₄ concentration, stabilizer concentration, reaction temperature, complex kinetics and excess water requirement. All of these limit the hydrogen storage capacities of NaBH₄, whose practical application, however, has not yet reached a scientific and technical maturity. Despite extensive efforts, the kinetics of NaBH₄ hydrolysis reaction is not fully understood. Therefore, better understanding of the kinetics of hydrolysis reaction and development of a reliable kinetic model is a field of great importance in the study of NaBH₄ based hydrogen generation system. This review summarizes in detail the extensive literature on kinetics of hydrolysis of aqueous NaBH₄ solution.     

Oxygen and nitrogen-doped metal-free microalgae carbon nanoparticles for efficient hydrogen production from sodium borohydride in methanol

Here, the oxygen(O) and nitrogen(N) doped metal-free carbon synthesis including potassium hydroxide (KOH) activation of Spirulina Platensis microalgae, followed by nitric acid (HNO₃) activation is reported for the first time. Oxygen and nitrogen-doped metal-free catalysts were investigated for efficient hydrogen (H₂) production from methanolysis of sodium borohydride (NaBH₄). Compared to the catalyst obtained with the KOH activation, the catalytic activity for O and N doped metal-free showed about a four-fold improvement. The catalysts were analysed by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (XRD), nitrogen adsorption, elemental analysis and Fourier-transform infrared spectroscopy (FTIR). The effects of temperature, NaBH₄ amounts, catalyst loading and reusability experiments on the catalytic performance of obtained metal-free catalysts by H₂ release from NaBH₄ methanolysis were performed. This study can provide a new alternative strategy to produce specific metal-free carbon catalysts doped heteroatom for environmentally friendly conversion to produce H₂ efficiently.     

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).     

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.     

Apparatus for the production of hydrogen from sodium borohydride in alkaline solution

Extended application of hydrogen as energy carrier demands an economical, safe and reliable technology for storage. In particular, chemical hydrides appear as capable and promising to overcome the issues related to hydrogen safety and handling and to be considered competitive with respect to conventional fuels.     

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.     

Catalytic hydrolysis of sodium borohydride solution for hydrogen production using thermal plasma synthesized nickel nanoparticles

In the present study nickel nanoparticles were synthesized by thermal plasma route. In this method we obtained highly crystalline almost spherical nanoparticles with maximum number of particles having size around 30–50 nm. These nanoparticles were thoroughly characterized and employed as a catalyst for hydrogen production using hydrolysis of sodium borohydride (NaBH₄). The effect of initial concentration of NaBH₄, pH and temperature of solution on the rate of hydrogen production was investigated. Nickel nanoparticles exhibits first order reaction with respect to NaBH₄ concentration at elevated temperatures. After hydrolysis, the nickel nanoparticles showed presences of B–O and B–OH species on the nickel surface. The catalyst was found to be stable during 5 sequential cycles of test.     

Bimetallic Ag-Ni nanoparticles as an effective catalyst for hydrogen generation from hydrolysis of sodium borohydride

Stable Ag-Ni bimetallic NPs was prepared, characterized, and applied for the dehydrogenation of sodium borohydride in aqueous media. The structure morphology and properties of Ag-Ni NPs were characterized by using conventional techniques such as surface field scanning electron microscopy (FESEM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV–visible spectroscopy, energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy. The Ag-Ni NPs were found to be highly effective catalyst to the hydrogen generation from the hydrolysis of sodium borohydride. The catalytic activity of Ag-Ni was increased with increasing the ratio of Ni (Ag₂₅-Ni₂₅ ˂ Ag₂₅-Ni₅₀ ˂ Ag₂₅-Ni₇₅). The reaction follows first-order kinetics with respect to [NaBH₄]. The apparent activation energy = 16.2 kJ/mol, activation enthalpy = 13.4 kJ/mol, and activation entropy = −135.2 J/K/mol were calculated for the hydrogen generation. The activation energy is much lower than those of the other bimetallic nano catalysts. The excellent catalytic activity, good stability, and low cost make the Ag based Ag-Ni NPs a suitable catalyst for the generation of hydrogen in sodium borohydride hydrolysis. It was found that the Ag₂₅-Ni₇₅ is one of the most reusable and durable catalyst for six consecutive cycles without any significant decrease in their catalytic activity.     

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.     

Sulphur and nitrogen-doped metal-free microalgal carbon catalysts for very active dehydrogenation of sodium borohydride in methanol

Micro algae based on Spirulina platensis is successfully used for the synthesis of S and N-doped metal-free carbon materials. The procedure consists of three stages; (i) Activated carbon production by KOH activation in CO₂ atmosphere (S-AC), (ii) S atom doping to the obtained S-AC using sulphuric acid by hydrothermal activation (S-AC-S), (iii) N atom doping by hydrothermal activation to S-AC obtained using nitric acid (S-AC-S-N). The S and N doped metal-free catalysts are used for H₂ release in NaBH₄ methanolysis reaction (NaBH₄-MR) for the first time. The metal-free carbon catalysts are characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM-EDS), X-ray diffractometer spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR), nitrogen adsorption and elemental analysis (CHNS) methods. When the HGR values obtained for S-AC-S-N (26,000 mL min^?1 g^?1) and S-AC (2641 mL min^?1 g^?1) are compared, there is a 9.84-fold increase. Activation energy (Ea) value for S-AC-S-N was 10.59 kJ mol^?1.     

Hydrogen production from solid sodium borohydride with hydrogen peroxide decomposition reaction

This study investigates hydrogen production from solid sodium borohydride with hydrogen peroxide decomposition reaction for a fuel cell based air-independent propulsion system in space and underwater applications. Sodium borohydride in the solid state was used as a hydrogen source in the present study. Pure hydrogen could be generated by a catalytic hydrolysis reaction in which the water source was obtained from the hydrogen peroxide decomposition. Hydrogen peroxide was selected as an oxidizer, being decomposed catalytically to generate oxygen and water. The pure oxygen was provided to a fuel cell and the water was stored separately for the hydrolysis reaction. A fuel cell system was fabricated to validate the fuel cell based air-independent power system proposed in the present study. Two catalytic reactors were prepared; one for the solid sodium borohydride hydrolysis reaction and the other for the hydrogen peroxide decomposition reaction. The hydrogen and oxygen generation rate were measured based on the various conditions. The performance evaluation of a fuel cell system proposed in the present study was carried out.     

Preparation and application of sodium borohydride composites for portable hydrogen production

Novel composites consisting of cobalt–boron (CoB) catalyst and sodium borohydride (NaBH₄) implantation in polymers (polyethylene glycol (PEG) or sodium alginate) were prepared for portable hydrogen production. The CoB catalyst was synthesized by the reduction of cobalt salt in NaBH₄ solution followed by heat treatment in nitrogen atmosphere. The catalyst was embedded in PEG gel or alginate beads and NaBH₄ was directly added in PEG–dimethylformamide (DMF) gel and adsorbed in alginate beads. It is noted that the composites prepared are stable in dry air and can be easily used for hydrogen production. A rate of hydrogen production of 750 ml min⁻¹ g⁻¹ was reached when simply putting the composites into pure water. The humidified pure hydrogen can be used conveniently for fuel cells.     

Fluorinated cobalt for catalyzing hydrogen generation from sodium borohydride

The present paper reports preliminary results relating to a search for durable cobalt-based catalyst intended to catalyze the hydrolysis of sodium borohydride (NaBH₄). Fluorination of Co [Suda S, Sun YM, Liu BH, Zhou Y, Morimitsu S, Arai K, et al. Catalytic generation of hydrogen by applying fluorinated-metal hydrides as catalysts. Appl Phys A 2001; 72: 209–12.] has attracted our attention whereas the fluorination of Co boride has never been envisaged so far. Our first objective was to compare the reactivity of fluorinated Co with that of Co boride. We focused our attention on the formation of Co boride from fluorinated Co. Our second objective was to show the fluorination effect on the reactivity of Co. Our third objective was to find an efficient, durable Co catalyst. It was observed a limited stabilization of the Co surface by virtue of the fluorination, which made the formation of surface Co boride more difficult while the catalytic activity was unaltered. The fluorination did not affect the number of surface active sites. Nevertheless, it did not prevent the formation of Co boride. The fluorination of Co boride was inefficient. Hence, fluorination is a way to gain in stabilization of the catalytic surface but it is quite inefficient to hinder the boride formation. Accordingly, it did not permit to compare the reactivity of Co boride with that of Co.     

The use of metallurgical waste sludge as a catalyst in hydrogen production from sodium borohydride

In this study, the metallurgic sludge which contained oil and was obtained as waste of grinding, sharpening and milling parts was used in the production of hydrogen (H₂) from sodium borohydride (NaBH₄). The hydrolysis of NaBH₄ with the metallurgic sludge catalyst was investigated depending on several parameters such as sodium hydroxide (NaOH) concentration, catalyst amount, NaBH₄ concentration and temperature. The obtained metallurgic sludge catalyst was characterized by the XRD, FT-IR and SEM techniques and was evaluated for its activity in the H₂ generation from NaBH₄ hydrolysis. The maximum H₂ production rate from the hydrolysis of NaBH₄ with the metallurgic sludge catalyst was calculated as 9366 ml min⁻¹.g_cat⁻¹. The value of activation energy was found as 48.05 kJ mol⁻¹.     

Aluminum chloride for accelerating hydrogen generation from sodium borohydride

The present research paper reports preliminary results about the utilization of anhydrous aluminum chloride (AlCl₃) for accelerating hydrogen generation through hydrolysis of aqueous solution of sodium borohydride (NaBH₄) at 80 °C. To the best of our knowledge, AlCl₃ has never been considered for that reaction although many transition metal salts had already been assessed. AlCl₃ reactivity was compared to those of AlCl₃·6H₂O, AlF₃, CoCl₂, RuCl₃ and NiCl₂. With AlCl₃ and a NaBH₄ solution having a gravimetric hydrogen storage capacity (GHSC) of 2.9 wt.%, almost 100% hydrogen was generated in few seconds, i.e., with a hydrogen generation rate (HGR) of 354 L min⁻¹ g⁻¹(Al). This HGR is one of the highest rates ever reported. Higher HGRs were obtained by mixing AlCl₃ with CoCl2, RuCl₃ or NiCl₂. For example, the system RuCl₃:AlCl₃ (50:50 mass proportion) showed a HGR > 1000 L min⁻¹ g⁻¹(Ru:Al). The hydrolysis by-products (once dried) were identified (by XRD, IR and elemental analysis) as being Al(OH)₃, NaCl and Na₂B(OH)₄Cl and it was observed that even in situ formed Al(OH)₃ has catalytic abilities with HGRs of 5 L min⁻¹ g⁻¹(Al). All of these preliminary results are discussed, which concludes that AlCl₃ has a potential as accelerator for single-use NaBH₄-based storage system.     

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.     

Mechanistic insights into hydrogen production from formic acid catalyzed by Pd@N-doped graphene: The role of the nitrogen dopant

The catalytic decomposition of formic acid (HCOOH) is a crucial process for hydrogen production technologies. Herein, periodic density functional theory (DFT) calculations were employed to explore the effect of N-doping on the decomposition of formic acid. We designed a series of single Pd-atoms deposited in the single vacancy of N-doped graphene sheets, namely Pd-DGr, Pd–N1Gr, Pd–N2Gr, and Pd–N3Gr, as the proposed catalysts. Our findings show that H₂ production from HCOOH dehydrogenation on these surfaces proceeds via the formate (HCOO) pathway (Path-I) rather than the carboxylate (COOH) pathway (Path-II). Furthermore, the Pd–N3Gr catalyst shows the greatest catalytic reactivity toward HCOOH dehydrogenation via Path-I, requiring an activation energy (E_a) of 0.38 eV.On the other hand, the undesirable dehydration of HCOOH to carbon monoxide (CO) through COOH (Path-IIIA) or formyl (HCO) (Path-IIIB) intermediates is unlikely to occur on Pd–N3Gr due to a large activation energy. We found that the active species on the catalyst surface increased with N-doping concentration. Additionally, microkinetic simulations of the HCOOH decomposition on these surfaces confirmed the high activity and selectivity of the Pd–N3Gr catalyst toward HCOOH dehydrogenation (Path-I). These calculated results highlight that the Pd–N3Gr catalyst is a promising candidate for the formic acid decomposition reaction to yield hydrogen.     

Room temperature hydrolytic dehydrogenation of ammonia borane catalyzed by Co nanoparticles

Amorphous and well dispersed Co nanoparticles (less than 10 nm) have been in situ synthesized in aqueous solution at room temperature. The as-synthesized Co nanoparticles possess high catalytic activity (1116 L mol⁻¹ min⁻¹) and excellent recycling property for the hydrogen generation from aqueous solution of ammonia borane under ambient atmosphere at room temperature. The present low-cost catalyst, high hydrogen generation rate and mild reaction conditions (at room temperature in aqueous solution) represent a promising step toward the development of ammonia borane as a viable on-board hydrogen-storage and supply material.