Metal-Schiff Base complex catalyst in KBH4 hydrolysis reaction for hydrogen production

It is the first study to synthesize Co(II)-Schiff Base complex and to use it like a catalyst for potassium borohydride hydrolysis reaction to hydrogen production. Co(II)-complex is synthesized with CoCl₂·6H₂O and 5-Amino-2,4-dichlorophenol-3,5-di-tert-butylsalisylaldimine ligand. KBH₄ hydrolysis reaction is studied according as percentage of KBH₄, percentage of KOH, amount of Co-Schiff Base complex catalyst and temperature effects. Co-Schiff Base complex is highly effective catalyst and initial rates (R_o) of KBH₄ hydrolysis reaction were 61220.00 and 99746.67 mL H₂. g⁻¹ cat. min⁻¹ at 30 °C and 50 °C. Furthermore this study includes the kinetic calculations and for this reaction calculated activation energy is 17.56 kJ mol⁻¹.     

Controllable hydrogen production from NaBH4 hydrolysis promoted by acetic acid

Numerous catalysts have been widely investigated for accelerating hydrogen production from NaBH₄ hydrolysis. However, these catalysts are usually complicated in structures, costly in fabrication, and hazardous for environment. In this work, cheap and environment-friendly acetic acid, CH₃COOH, is employed to promote NaBH₄ hydrolysis to produce hydrogen in a considerable rate. The experimental results demonstrate that the addition of suitable amount of CH₃COOH into NaBH₄ solutions stabilized with NaOH could dramatically accelerate the hydrolysis reaction. Additionally, the start/stop of NaBH₄ hydrolysis could be controlled by adding acid or base into the solution to realize “go-as-you-please” on-site hydrogen production.     

L-cysteine-protected ruthenium nanoclusters on CdS as efficient and reusable photocatalysts for hydrogen production

Nanocluster-modified semiconductor-based photocatalysts have been identified as a vital area of research in the area of photocatalytic hydrogen evolution from water. However, the existing ligand protection strategy for synthesizing ultrasmall metal nanoclusters remains confined to a few metals, including Au, Ag, Cu, and their alloys. In this investigation, we describe a facile solution-phase reduction synthesis method for the production of L-cysteine-protected Ru nanoclusters. Our findings demonstrate that these novel Ru nanoclusters function as cocatalysts, which notably increase the photocatalytic activity and photostability of CdS photocatalysts. Moreover, the hybrid CdS photocatalyst modified with Ru nanoclusters exhibits superior activity and stability relative to photoinduced Ru nanoparticles/CdS composite photocatalysts. The simplicity of the synthesized metal nanocluster cocatalyst and its effectiveness in enhancing photocatalyst activity, while reducing the use of precious metals, present new avenues for the development of advanced photocatalysts.     

Catalytic hydrolysis of hydrazine borane for chemical hydrogen storage: Highly efficient and fast hydrogen generation system at room temperature

There has been rapidly growing interest for materials suitable to store hydrogen in solid state for transportation of hydrogen that requires materials with high volumetric and gravimetric storage capacity. B-N compounds such as ammonia-triborane, ammonia-borane and amine-borane adducts are well suited for this purpose due to their light weight, high gravimetric hydrogen storage capacity and inclination for bearing protic (N-H) and hydridic (B-H) hydrogens. In addition to them, more recent study [26] has showed that hydrazine borane with a gravimetric hydrogen storage capacity of 15.4% wt needs to be considered as another B-N compound that can be used for the storage of hydrogen. Herein we report for the first time, metal catalyzed hydrolysis of hydrazine borane (N₂H₄BH₃, HB) under air at room temperature. Among the catalyst systems tested, rhodium(III) chloride was found to provide the highest catalytic activity in this reaction. In the presence of rhodium(III) chloride, the aqueous solution of hydrazine borane undergoes fast hydrolysis to release nearly 3.0 equivalent of H₂ at room temperature with previously unprecedented H₂ generation rate TOF = 12000 h⁻¹. More importantly, it was found that in the catalytic hydrolysis of hydrazine borane the reaction between hydrazine borane and water proceeds almost in stoichiometric proportion indicating that the efficient hydrogen generation can be achieved even from the highly concentrated solution of hydrazine borane or in the solid state when water added to the solid hydrazine borane. This finding is crucial especially for on-board application of the existing system. The work reported here also includes (i) finding the solubility of hydrazine borane plus its stability against self-hydrolysis in water, (ii) the definition of reaction stoichiometry and the identification of reaction products for the catalytic hydrolysis of hydrazine borane, (iii) the collection of wealthy kinetic data to demonstrate the effect of substrate and catalyst concentrations on the hydrogen generation rate and to determine the rate law for the catalytic hydrolysis of hydrazine borane, (iv) the investigation of the effect of temperature on the rate of hydrogen generation and determination of activation parameters (E_a, ΔH^#, and ΔS^#) for the catalytic hydrolysis of hydrazine borane.     

Improved hydrogen storage capacity through hydrolysis of solid NaBH4 catalyzed with cobalt boride

In this article the feasibility of the reaction of liquid water with a solid NaBH₄/catalyst mixture for improved hydrogen storage capacity and on-demand H₂ generation is reported. The synthesized low-cost nanosized catalyst consists of a Co₂B core surrounded by an oxide layer, presenting a relatively large specific surface area (70 m² g⁻¹). Calorimetric experiments coupled to simultaneous measurements of the evolved hydrogen volume have shown the positive effect of the locally heat release during reduction of the superficial oxidized layer. The synergetic effects of the exothermicity of both the oxidized layer reduction and the hydrolysis reaction coupled to the high efficiency of the cobalt boride catalyst led to an “enhanced regime” observed at room temperature. The “enhanced regime” corresponds to a global reaction stoichiometry of 1 mol of NaBH₄ reacting with 3 mol of water, conducting to a hydrogen yield of 8.7 wt.%. Effects of temperature and catalyst content were studied.     

Development of highly efficient and reusable Ruthenium complex catalyst for hydrogen evolution

Herein, we report an efficient, environmentally friendly and stable catalyst development to hydrogen evolution from sodium borohydride hydrolysis. For this purpose, Ruthenium complex catalyst successfully fabricated via 5-Amino-2,4-dichlorophenol-3,5-ditertbutylsalisylaldimine ligand and RuCl₃·H₂O salt. Ru complex catalyst was identified with X-Ray Diffraction Analysis, Infrared Spectroscopy, Elemental Analysis, Transmission electron microscopy, Scanning Electron Microscope and Brunauer-Emmett-Teller Surface Area Analysis. According to the analysis results, it was confirmed that Ru complex catalyst was successfully synthesized. Ru complex was used as a catalyst in NaBH₄ hydrolysis. The kinetic performance of Ru complex catalyst was evaluated at various reaction temperatures, various sodium borohydride concentration, catalyst concentration and sodium hydroxide concentration in hydrogen evolution. The apparent activation energy for the hydrolysis of sodium borohydride was determined as 25.8 kJ mol^?1. With fully conversion, the promised well durability of Ru complex was achieved by the five consecutive cycles for hydrogen evolution in sodium borohydride hydrolysis The hydrogen evolution rates were 299,220 and 160,832 mL H₂ g_cat^?1 min^?1 in order of at 50 °C and 30 °C. Furthermore, the proposed mechanism of Ru complex catalyzed sodium borohydride hydrolysis was defined step by step. This study provides different insight into the rational design and utilization and catalytic effects of ruthenium complex in hydrogen evolution performance.     

Ruthenium nanoparticles supported in the network of HES-p(AMPS) IPN hydrogel as efficient catalyst for hydrogen production from the hydrolysis of ethylenediamine bisborane

In this study, Ru(0) nanoparticles supported in 2-hydroxyethyl starch-p-(2-Acrylamido-2-methyl-1-propanesulfonic acid) interpenetrating polymeric network (HES-p(AMPS) IPN) were synthesized as hydrogel networks containing hydroxyethyl starch, which is a natural polymer with oxygen donor atoms. The structure and morphology of the prepared HES-p(AMPS) IPN hydrogel and Ru@HES-p(AMPS) IPN catalyst were characterized using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscope (TEM). Ru@HES-p(AMPS) IPN was used as catalyst for hydrogen production from the hydrolysis of ethylenediamine bisborane (EDAB). The activation parameters for the hydrolysis reaction of EDAB catalyzed by Ru@HES-p(AMPS) IPN were calculated as E_a = 38.92 kJ mol⁻¹, ΔH^# = 36.28 kJ mol⁻¹, and ΔS^# = −111.85 J mol⁻¹ K⁻¹, respectively. The TOF for the Ru@HES-p(AMPS) IPN catalyst was 2.253 mol H₂ (mol Ru(0) min)⁻¹. It was determined that Ru@HES-p(AMPS) IPN, a reusable catalyst, still had 81.5% catalytic activity after the 5th use.     

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.     

Fe doped-CoB catalysts with phosphoric acid-activated montmorillonite as support for efficient hydrogen production via NaBH4 hydrolysis

In this study, montmorillonite (MMT) clay was modified with different acids to be used as support material. The modified MMT clay was used to obtain hydrogen in the hydrolysis reactions of NaBH₄ (NaBH₄-HR) as a support material for the Co–B and Co–Fe–B catalyst. During the activation of MMT clay, the effects of different acids, phosphoric acid (H₃PO₄) concentration, and impregnation time with H₃PO₄ were investigated. During the hydrogen generation from the NaBH₄-HR, effects of Co loading, Fe loading, NaBH₄ concentration, temperature and, catalyst durability were investigated. The maximum HGRs for MMT-H₃PO₄–CoB and MMT-H₃PO₄–Co–Fe–B treated with 5 M H₃PO₄ for 7 days were 1869 and 4536 mL/min/g_catalyst, respectively. The activation energies for MMT-H₃PO₄–CoB and MMT-H₃PO₄–Co–Fe–B catalyst samples were 49.5 and 38.90 kJ/mol.     

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.     

Ruthenium quantum dots supported on carbon nanofibers as an efficient electrocatalyst for hydrogen evolution reaction

The hydrogen evolution reaction (HER) is a key step for producing hydrogen by water electrolysis, and an economical, facile and environment friendly method of fabricating catalysts for HER is urgent and essential. In this work, we design a high efficient and stable HER catalyst though a simple adsorption and pyrolysis method. The fabricated catalyst presents ruthenium (Ru) quantum dots (QDs) uniformly distributes on the carbon nanofibers (CNF) with a three dimensional (3D) networks structure (Ru@CNF). By means of quantum size effect of Ru QDs and the 3D networks structure of the carbon nanofibers, the former is beneficial to provide more catalytic active sites and the latter is in favour of electron transport. The sample Ru@CNF exhibits a low overpotential of 20 mV at a current density of 10 mA cm⁻² and Tafel slope of 31 mV dec⁻¹ in 1 M KOH, which is better than that of Pt/C (28 mV and 36 mV dec⁻¹), and most of reported Ru-based and transition metal catalysts. Furthermore, it exhibits robust stability when testing at an overpotential of 75 mV for 24 h. Therefore, this work provides a low-cost, simple and feasible method for fabricating HER catalyst, which possesses commercial application prospect in the field of producing hydrogen by water electrolysis.     

Ru/MoO2 decorated on CNT networks as an efficient electrocatalyst for boosting hydrogen evolution reaction

Generally, electrochemical hydrogen evolution reaction (HER) is hampered by slow kinetics and low round-trip efficiency. Electrocatalysts with a hierarchical structure and large surface area are expected to overcome these problems. Herein, we prepared a Ru/MoO₂/carbon nanotubes (RMC) hybrid with a hierarchical structure by a convenient solid-phase reaction (SPR) method, and studied the electrochemical activity for HER. After annealing as-prepared RuO₂/MoO₂/carbon nanotubes (ROMC) precursor in a tubular furnace under Ar atmosphere, RuO₂ and MoS₂ were in-situ transformed into Ru metal and MoO₂ phase by the redox SPR. Through various tests, we have confirmed that the new formed Ru metal and MoO₂ phase are combined and uniformly coated on the outer surface of CNTs. Interestingly, the RMC-500 exhibits the best HER performance with a low overpotential of 16 mV at l0 mA cm^?2, small Tafel slope of 45 mV dec^?1, higher electrochemical active surface area, and long-time durability in alkaline electrolyte.     

CeO2 supported multimetallic nano materials as an efficient catalyst for hydrogen generation from the hydrolysis of NaBH4

Nowadays, there is still no suitable method to store large amounts of energy. Hydrogen can be stored physically in carbon nanotubes or chemically in the form of hydride. In this study, sodium borohydride (NaBH₄) was used as the source of hydrogen. However, an inexpensive and useful catalyst (Co–Cr–B/CeO₂) was synthesized using the NaBH₄ reduction method and its property was characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), x-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) measurements. The optimized Co–Cr–B/CeO₂ catalyst exhibited an excellent hydrogen generation rate (9182 mLg_metal⁻¹min⁻¹) and low activation energy (35.52 kJ mol⁻¹). The strong catalytic performance of the Co–Cr–B/CeO₂ catalyst is thought to be based on the synergistic effect between multimetallic nanoparticles and the effective charge transfer interactions between the metal and the support material.     

Progress on methanol reforming technologies for highly efficient hydrogen production and applications

With the continuous development of human society, the shortages of fossil resource and environmental pollution are increasingly prominent. Hydrogen is a clean and efficient alternative energy, among various hydrogen production technologies, methanol reforming has been regarded as a promising candidate to produce hydrogen for daily energy supply due to its low cost and safe transportation. In this review, we discuss the sources of methanol and the methods of methanol reforming for hydrogen production. Then, we focus on the catalysts for methanol reforming and their preparation methods. Particular attention is paid to the structural design and manufacturing process to make methanol reforming microreactors. We also summarize recent studies on the practical applications of methanol reforming technologies, as well as the capture and utilization of the generated carbon to reduce its emission. Finally, the prospect challenges of methanol reforming for highly efficient hydrogen production technologies and contribution to the “double carbon” goals and the challenges are discussed. In summary, this review will be conducive to the development of hydrogen-methanol economy for practical and industry applications.     

Insight into the role of solvents in enhancing hydrogen production: Ru-Co nanoparticles catalyzed sodium borohydride dehydrogenation

Ru-Co nanoparticles prepared in nano-size by combustion derived of citric acid used sol-gel technique followed by calcination process at 450 °C. The external and internal properties of nano-sized catalyst were characterized by XRD, XPS, SEM, TEM, ICP-OES, and N₂ sorption techniques. The characterization results proved that nano-sized catalyst was mixture of cubic Co₃O₄ (18 nm) and tetragonal RuO₂ (40 nm) crystals with mesoporous structure (12.64 m²g^-1). Insight into the role of solvents for enhancing hydrogen production from Ru-Co nanoparticles catalyzed sodium borohydride (NaBH₄, SBH) was systematically studied by altering the dehydrogenation medium with water or methanol. The reaction kinetic performance of nano-sized catalyst was evaluated by performing both hydrogen generation reactions at various reaction temperatures, initial SBH concentration, and catalyst dosage to evaluate the hydrogen generation activity. Ru-Co nanoparticles exhibited exclusive catalytic performance for hydrogen generation by hydrolysis and methanolysis of SBH. The apparent activation energies (E_a) for the catalytic hydrolysis and methanolysis of SBH over Ru-Co nanoparticles were determined to be 20.02 kJ mol⁻¹ and 54.38 kJ mol⁻¹, respectively. Furthermore, Ru-Co nanoparticles also performed satisfied stability for both hydrolysis and methanolysis reactions. Beside both hydrogen generation was achived with fully conversion of SBH, Ru-Co nanoparticles promised good recyclability for at least 5 cycle for methanolysis of SBH.     

Ultra-fine Ru nanoparticles decorated V2O3 as a pH-universal electrocatalyst for efficient hydrogen evolution reaction

Developing high-efficiency electrocatalysts viable for pH-universal hydrogen evolution reaction (HER) has attracted great interest because hydrogen is a promising renewable energy carrier for replacing fossil fuels. Herein, we present a facile strategy for fabricating ultra-fine Ru nanoparticles (NPs) decorated V₂O₃ on the carbon cloth substrates as efficient and stable pH-universal catalysts for HER. Benefiting from the metallic property and electronic conductivity of V₂O₃ matrix, the optimized hybrid (Ru/V₂O₃-CC) exhibits excellent HER activities in a wide pH range, achieving lower overpotentials of 184, 219, and 221 mV at 100 mA cm⁻² in 0.5 M H₂SO₄, 1.0 M KOH and 1.0 M phosphate-buffered saline, respectively. Moreover, the electrode remains superior stability with negligible degradation after 5000 cyclic voltammetry scanning whether in acidic, alkaline or neutral media. Experimental results, combined with theoretical calculations, demonstrate that the interaction between Ru NPs and the support V₂O₃ induces the local electronic density diversity, allowing optimization of the adsorption energy of Ru towards hydrogen intermediate H1, thus favoring the HER process.     

Mixed-dimensional niobium disulfide-graphene foam heterostructures as an efficient catalyst for hydrogen production

Besides developing a large number of catalysts for hydrogen evolution reaction (HER) in alkaline electrolytes, its conversion efficiency remained low. Herein, we have developed mixed-dimensional heterostructures of niobium disulfide (NbS₂) with graphene foam grown on nickel foam (NbS₂-Gr-NF). The strong lateral fusion results in activating the catalytic sites of NbS₂, the three-dimensional substrate provides easy access of electrolyte to active sites and increased electrochemically active surface area, while enhanced conductivity provides faster transfer of electrons to and from active sites. Therefore, NbS₂-Gr-NF heterostructures resulted in an exceptionally high current density of 500 mA cm⁻² at a very low overpotential of 306 mV in 1 M KOH solution and even can achieve the current density values of 914 mAcm⁻² at 338 mV only at a slight increase in overpotential (32 mV). Moreover, a Tafel value of ~72 mV dec⁻¹ confirms that as-developed heterostructure provides fast reaction kinetics where the reaction is mainly controlled by the Volmer step. Achieving such high current density at a faster rate with high stability makes NbS₂-Gr-NF heterostructures a potential candidate for water-splitting, especially in alkaline electrolytes.     

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.     

Smart nanocatalyst for ammonia-borane hydrolysis: Thermo-controlled hydrogen generation

A smart catalyst was fabricated by combining ordered mesoporous silica, Pt nanoparticles with ultra-small size (<2 nm), decatungstoeuropate and thermo-responsive polymer. Due to the coating of thermo-sensitive polymer and loading of Pt nanoparticles, the catalyst shows the thermo-controlled catalytic activity in the release of hydrogen from ammonia borane. For example, the catalyst has high catalytic activity at room temperature, showing catalytic “on” state. However, the hydrogen generation can be obviously suppressed at high temperature, showing catalytic “off” state. Furthermore, the composite hydrogel shows the switchable red luminescence in solution at high/low temperatures, which offers the possibility to track catalyst and understand catalytic mechanism. The thermo-controllable system of hydrogen generation has great potential applications in the safe hydrolysis from chemical hydride fuel. The smart catalyst could automatically decrease the release of hydrogen when the temperature of fuel system is high.