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.     

Co complex modified on Eupergit C as a highly active catalyst for enhanced hydrogen production

In present paper, the preparation and catalytic activity of Eupergit C polymer (EC) modified Co complex was reported. Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Brunauer-Emmett-Teller Surface Area Analysis (BET), Fourier Transform Infrared Spectroscopy (FT-IR), Transmission Electron Microscopy (TEM) coupled with energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) were used to characterization of catalyst. EC modified-Co complex was the first time examined as a catalyst in NaBH₄ hydrolysis to H₂ evolution. The kinetic calculations were determined by using two different kinetic methods. The low activation energy barriers were achieved as 21.673 kJ mol^?1 for nth order model and as 21.061kJmol^?1 for Langmuir-Hinshelwood (L-H) model at low temperatures. EC modified-Co complex catalyst exhibited high performance with H₂ evolution rates of 3914 mL H₂g_cat^?1min^?1 and 9183 mLH₂g_cat^?1min^?1 at 30 °C–50 °C. Additionally, Langmuir–Hinshelwood mechanism was explained for EC modified Co complex catalyzed sodium borohydride hydrolysis reaction. The reusability experiments showed that EC modified-Co complex catalyst maintained excellent stability with 100% conversion and without significant lost after the 6th run.     

Synthesis of polymer supported Ni (II)-Schiff Base complex and its usage as a catalyst in sodium borohydride hydrolysis

Influence of using as catalysis, Ni-Schiff Base complex which we previously synthesized [1] used to support with amberzyme oxirane resin (A.O.R.) polymer for increasing the catalytic activity in NaBH₄ hydrolysis reaction, to hydrogen generation was studied. The prepared catalyst was characterized by using SEM, XRD, BET, FT-IR analyze technique. Polymer supported Ni-Schiff Base complex catalyzed NaBH₄ hydrolysis reaction was investigated depending on concentration of NaBH₄, concentration of NaOH, temperature, percentage of Ni complex in total polymer supported Ni-Schiff Base complex and amount of catalyst factors. The maximum hydrogen production rate from hydrolysis of sodium borohydride with nickel-based complex catalyst compared to the pure nickel catalyst is increased from 772 mL H₂·g^?1 cat.·min^?1 to 2240 mL H₂ g^?1 cat.·min^?1 [1], and with supported amberzyme oxirane resin polymer this nickel based complex catalyst was increased to 13000 mL H₂·g^?1 cat.·min^?1 at 30 °C. The activation energy of complex catalyzed NaBH₄ hydrolysis reaction was found as 25.377 kJ/mol. This work also includes kinetic information for the hydrolysis of NaBH₄.     

Highly efficient and reactivated electrocatalyst of ruthenium electrodeposited on nickel foam for hydrogen evolution from NaBH4 alkaline solution

Cyclic life of catalyst for hydrolysis of sodium borohydride is one of the key issues, which hinder commercialization of hydrogen generation from sodium borohydride (NaBH₄) solution. This paper is aimed at promoting the cyclic life of Ru/Ni foam catalysts by employing an electro-deposition method. The effect of hydrolysis parameters on hydrolysis of sodium borohydride was studied for improving the catalytic performance. It is found that the hydrogen generation rate (HGR) of the hydrolysis reaction catalyzed by Ru/Ni foam catalyst can reach as high as 23.03 L min^?1 g^?1 (Ru). The Ru/Ni foam catalyst shows good catalytic activity after a cycleability test of 100 cycles by rinsing with HCl, which is considered as more effective method than rinsing with water for recovering the performance of Ru/Ni foam catalyst.     

Al2O3 based Co-Schiff Base complex catalyst in hydrogen generation

This work presents the study of the catalytic activity of aluminum oxide supported Co-Schiff Base complex derived from 4,4′-Methylenebis(2,6-diethylaniline)-3,5-ditertbutylsalicylaldimine-Co-Schiff Base complex in sodium borohydride hydrolysis. This catalyst is characterized with XRD, FT-IR, SEM, TEM, and BET. The respective reaction kinetics have been calculated. With the catalyst condition, maximum reaction (initial) rate is 106540 and 147193,3 mL H₂/g_cat.^.min. at 30 °C and 50 °C. For this reaction apparent activation energy is 44,7792 kJ^.mol⁻¹ with 20–50 °C. The reaction order value (n) for this catalytic system is 0,31. Additionally when Al₂O₃ supported Co-Schiff Base complex compared with pure Co-Schiff Base complex, the experimental results show that the aluminum oxide support exhibits enhancing effect with 106540 and 64147 mL H₂/g_cat. min respectively in sodium borohydride hydrolysis to Hydrogen production.     

Ruthenium-Imine catalyzed KBH4 hydrolysis as an efficient hydrogen production system

The present study focused on the increasing of hydrogen evolution through hydrolysis of potassium borohydride in the presence of Ruthenium complex catalyst. It is the first time to use the Ru-Imine complex catalyst in KBH₄ hydrolysis reaction to hydrogen evolution. The new Ru complex was synthesized from the tetradentate Imine ligand namely 4,4′-methylenebis (2,6-diethyl)aniline-3,5-di-tert-butylsalisylaldimine and Ru salt under the inert atmosphere. Ru-Imine complex was fully characterized by Elemental Analysis, Infrared Spectroscopy, Scanning Electron Microscope, X-Ray Diffraction Analysis, Brunauer-Emmett-Teller Surface Area Analysis and Transmission Electron Microscopy. By the synthesized Ru-Imine complex catalyst, the potassium borohydride hydrolysis reaction resulted in a lower energy barrier with 20,826 kJ/mol activation energy (Ea) for nth order kinetic model and 18,045 kJ/mol for Langmuir-Hinshelwood (L-H) kinetic model. According to the results Ru-complex was highly active and stable catalyst in KBH₄ hydrolysis reaction to hydrogen evolution with 45,466 mL H₂/g_cat.min and 76,815 mL H2/g_cat.min hydrogen generation rates at 30 °C and 50 °C respectively. Moreover Ru-Imine complex catalyst displayed 100% stability even at fifth recycle.     

Cobalt-nickel bimetal carbon sphere catalysts for efficient hydrolysis of sodium borohydride: The role of synergy and confine effect

Sodium borohydride exhibits great potential in the field of chemical hydrogen storage. A competent catalyst would accelerate its practical application for hydrogen utilization by enhance the efficiency of hydrogen generation from hydrolysis of sodium borohydride. Herein, a kind of highly efficient and durable synergistic Co–Ni bimetal inlaid carbon sphere catalyst (Co-NiΦC) was prepared by a co-pyrolysis method, of which the configuration of metal inlaid carbon sphere could effectively expose and anchor the active component by contrast with the capsule catalyst (Co–Ni@C) and supported catalyst (Co–Ni/C). Further, diverse cobalt-nickel contents of the Co-NiΦC catalysts were optimized to achieve the best hydrolysis performance of sodium borohydride. The structure-performance relationship of inlaid catalyst and the bimetallic synergistic mechanism were investigated by multiple characterization measurements and the density functional theory (DFT). As demonstrated, the inlaid Co-NiΦC-2 catalyst (Co/Ni molar ratio of 8/2) shows a promising catalytic activity of hydrogen generation rate up to 6364 mL_H2·min^?1·g_metal^?1, a relative low reaction activation energy of 30.3 kJ/mol as well as robust durability where it still remains about 83.4% of its initial reaction rate after the fifth cycle. The outstanding performance of the optimized catalyst may ascribe to the high dispersion, remarkable Co–Ni synergy and high stabilization of the Co–Ni nanoparticles under the confinement effect of the inlaid metal-carbon sphere configuration. This work provides an alternative avenue for the application of efficient carbon-supported bimetal catalysts in the future.     

Effective TiO2 supported Cu-Complex catalyst in NaBH4 hydrolysis reaction to hydrogen generation

This paper reports the experimental results on using TiO₂ based Cu(II)-Schiff Base complex catalyst for hydrolysis of NaBH₄. In the presence of Cu-Schiff Base complex which we reported in advance [1] and with titanium dioxide supports a novel catalyst named TiO₂ supported 4-4′-Methylenbis (2,6-diethyl)aniline-3,5-di-tert-buthylsalisylaldimine-Cu complex is prepared, successfully. The synthesized catalyst was characterized by means of X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Brunauer-Emmett-Teller Surface Area Analysis (BET) and Fourier Transform Infrared Spectroscopy (FT-IR). The as prepared catalyst was employed to generate hydrogen through hydrolysis reaction of NaBH₄. Effects of different parameters (e.g. amount of Cu-Schiff Base complex in all catalyst, percentage of NaBH₄, percentage of NaOH, amount of TiO₂ supported Cu-Schiff Base complex catalyst and different temperatures) are also investigated. A high apparent activation energy (Ea), 25,196 kJ.mol^-1 is calculated for hydrolysis of NaBH₄ at 20–50 °C. Hydrogen generation rate was 14,020 mL H₂/g_cat.min and 22,071 mL H₂/g_cat.min in order of 30 °C and 50 °C.     

Ceria supported manganese(0) nanoparticle catalysts for hydrogen generation from the hydrolysis of sodium borohydride

Herein we report for the first time the preparation and catalytic use of the ceria supported manganese(0) nanoparticles in hydrogen generation from the hydrolysis of sodium borohydride. They are in situ formed from the reduction of manganese(II) ions on the surface of ceria nanopowders during the catalytic hydrolysis of sodium borohydride in aqueous solution at room temperature. Manganese(0) nanoparticles are isolated from the reaction solution by centrifugation and characterized by a combination of analytical techniques. Nanoceria supported manganese(0) nanoparticles are highly active and long-lived catalysts providing a turnover frequency of 417 h^?1 and 45,000 turnovers in hydrogen generation from the hydrolysis of sodium borohydride at 25.0 ± 0.1 °C. They also have high durability as they retain 55% of their initial catalytic activity after the fifth cycle of hydrolysis providing a release of 4 equivalent H₂ gas per mol of sodium borohydride. The noticeable activity loss in successive runs of hydrolysis is attributed to the deactivation due to agglomeration. High activity and stability of ceria supported manganese(0) nanoparticles are ascribed to the unique nature of reducible cerium oxide. The formation of cerium(III) defects under catalytic conditions provides strong binding for the manganese(0) nanoparticles to oxide surface which makes the catalytic activity and stability favorable. Our report also includes the results of kinetic study of catalytic hydrolysis of sodium borohydride depending on the temperature, catalyst and substrate concentration.     

Hydrolysis of sodium borohydride solutions both in the presence of Ni–B catalyst and in the case of microwave application

In this study, the nickel boron (Ni–B) catalyst was studied in the microwave environment for hydrogen production from the hydrolysis of a sodium borohydride solution to release H₂. The catalytic activity of the Ni–B catalyst was measured by hydrogen production from the hydrolysis of sodium borohydride. The catalytic properties of the Ni–B catalyst in the microwave medium were examined by considering parameters such as NaOH concentration, NaBH₄ concentration, catalyst amount, temperature, and microwave power. Thus, the results obtained from the experiments carried out with Ni–B catalyst both in non-microwave and microwave media were compared. In the experiments, under microwave irradiation, the best result was the release of hydrogen gas from the Ni–B catalyst by applying 100 W of microwave energy at 40 °C. Activation energy values were calculated using the reaction rate constants obtained at different temperatures in the nth order kinetic model and the Langmuir - Hinshelwood model.     

Performance of Zn-Schiff Base complex catalyst in NaBH4 hydrolysis reaction

This study presents 4,4′-methylenebis(2,6-diethyl)aniline-3,5-ditertbutylsalisilaldimine-Zn complex synthesis and its using as a catalyst in sodium borohydride hydrolysis to H₂ generation. Surface morphology and structural properties of Zn-complex were investigated with XRD, FTIR, SEM, and BET analysis. The effects of different substrate concentration, effects of solution temperature, and effects of catalyst amount were studied for the hydrogen generation rate. Additionally kinetic parameters were studied. The activation energy was 22.978 kJ/mol and H₂ generation rates were calculated as 952.5 mmol H₂/g_cat^.min and 614.4 mmol H₂/g_cat^.min at 50 °C and 30 °C respectively for sodium borohydride hydrolysis reaction.     

Hydrogen generation from catalytic hydrolysis of sodium borohydride solution using supported amorphous alloy catalysts (Ni–Co–P/γ-Al2O3)

The supported amorphous alloy catalysts Ni–Co–P/γ-Al₂O₃ were synthesized by electroless plating for hydrogen generation from catalytic hydrolysis of sodium borohydride solution. The influences of deposition time, pH, NaBH₄ concentration and the Co/Ni atomic ratio on the hydrogen generation rate were investigated in this paper. The reported work also includes the full experimental details for the collection of a wealth of kinetic data to determine the activation energy (E_a = 52.05 kJ mol⁻¹). Energy dispersive X-ray spectrometer (EDS), field emission scanning electron Microscope (SEM), inductively coupled plasma-atomic emission spectrometer (ICP-AES) and X-ray diffraction (XRD), nitrogen adsorption–desorption isotherm were used to characterize surface element composition, morphology and structure of the amorphous alloy.     

Hydrogen generation by catalytic hydrolysis of sodium borohydride using the nano-bimetallic catalysts supported on the core-shell magnetic nanocomposite of activated carbon

The purpose of this study were to prepare the novel supported bimetallic cobalt-nickel catalysts on the core-shell magnetic nanocomposite of activated carbon derived from wood by sequential and co-deposition-precipitation. The performance of the prepared catalyst was evaluated for the hydrogen generation from hydrolysis of sodium borohydride. The magnetic catalysts were characterized by applying the XRD, XPS, FTIR, FESEM, TEM, ICP, BET and VSM tests. The hydrogen generation rate was increased with the reduction of calcination temperature. The well dispersed magnetic nanoparticles were fabricated with average size below of 30 nm which was confirmed by TEM, FESEM and XRD results. The activity of the prepared samples with respect to the preparation method was illustrated to follow a specific order: Co/Ni/MWAC > Ni/Co/MWAC > Co–Ni/MWAC. The developed model derived from design of experiments could correlate the operating parameters with the experimental data while the correlation coefficient was achieved to be 0.99. The hydrogen generation rate was increased with increasing the reaction temperature and the concentration of sodium borohydride in the alkaline solutions. The hydrogen generation rate was measured to be 740.70 ml min⁻¹. gcat⁻¹ in the presence of the Co/Ni/MWAC at 30 °C. The experimental study also indicated that the hydrolysis of sodium borohydride was a zero order type reaction and the activation energy was calculated 40.70 kJ mol⁻¹. The stability of the prepared sample was also investigated for six cycles which showed the acceptable performance of the synthesized catalyst for the practical applications.     

Graphene supported Pt–Ni bimetallic nanoparticles for efficient hydrogen generation from KBH4/NH3BH3 hydrolysis

Developing highly efficient and stable supported bimetallic nanoparticles catalysts via a facile strategy is one of the most admirable methods for sustainable hydrogen production from borohydride hydrolysis. Herein, we developed a facile technology for rapidly and straightforwardly manufacturing Pt–Ni bimetallic nanoparticles (BNPs) supported by partially reduced graphene oxide (prGO) with excellent catalytic activity and outstanding durability for hydrogen production from KBH₄ and NH₃BH₃ alkaline solution. The uniformly dispersed Pt₄₀–Ni₆₀ BNPs with a statistical size of around 2.6 nm exhibited a surprising catalytic activity of 23,460 mol-H₂·h^?1·mol-Pt^?1 at 308 K, moreover, whose activity was high up to 80% of the first time even after 30 runs, demonstrating an outstanding stability. The apparent activation energy for dehydrogenation of KBH₄ and NH₃BH₃ were respectively about 27.8 and 33.6 kJ/mol for the prepared Pt₄₀–Ni₆₀/prGO catalyst. The extraordinary catalytic activity of the Pt₄₀–Ni₆₀/prGO catalyst owing to the strong charge transfer effect between Pt–Ni BNPs and graphene.     

Nanocatalyst: Electrospun nanofibers of PVDF – Dicationic tetrachloronickelate (II) anion and their effect on hydrogen generation from the hydrolysis of sodium borohydride

In this article, we report poly(vinylidene fluoride) (PVDF) – dicationic tetrachloronickelate (II) anion (dicationic ionic salt [C₆(mpy)₂][NiCl₄]²⁻) nanofiber composites used as catalyst for hydrogen generation from the hydrolysis of sodium borohydride. The nanofiber composites were produced by electrospinning method. The synthesized nanofibers are characterized by SEM, TEM, EDX, and FTIR. The rate of hydrogen generation from catalyzed hydrolysis of NaBH₄ solution was determined as a function of temperature, substrate concentration, and catalyst concentration in the presence of prepared catalyst. The result shows that IL based nanofiber composite is a highly efficient and most important advantage that it can be easily recovered and repeatedly reused.     

Investigation on salisylaldimine-Ni complex catalyst as an alternative to increasing the performance of catalytic hydrolysis of sodium borohydride

In this study, 5-amino-2, 4-dichlorophenol-3, 5-ditertbutylsalisylaldimine-Ni complex catalyst is synthesised and used as an alternative to previous studies to produce hydrogen from hydrolysis of sodium borohydride. The resulting complex catalyst is characterised by XRD, XPS, SEM, FT-IR and BET surface area analyses. Experimental works are carried out at 30 °C with 2% NaBH₄, 7% NaOH and 5 mg of catalyst. The maximum hydrogen production rate from hydrolysis of sodium borohydride with nickel-based complex catalyst compared to the pure nickel catalyst is increased from 772 ml min^?1g^?1 to 2240 ml min^?1g^?1 by an increase of 190%. At the same time, the hydrolysis reaction with pure nickel catalyst is completed in 145 min while the hydrolysis reaction with nickel-based complex catalyst is completed in 50 min. The activation energy of this hydrolysis reaction was calculated as 18.16 kJ mol^?1. This work also includes kinetic information for the hydrolysis of NaBH₄.The reusability of the nickel-based complex catalyst used in this study has also been studied. The nickel-based complex catalyst is maintained the activity of 72% after the sixth use, compared to the first catalytic use.     

Hydrogen generation from hydrolysis of sodium borohydride by cubic Co–La–Zr–B nano particles as novel catalyst

Cubic Co–La–Zr–B nano particles were prepared in situ for the first time from the reduction of Co(II), La(III) and Zr(IV) chloride by sodium borohydride in methanol under reflux condition. Poly N-vinyl-2-pyrrolidone (PVP) as stabilizing agent was used for preparation of Co–La–Zr–B nano particles. Obtained powders were characterized by XRD, BET, ICP, SEM, TEM and UV–vis techniques. XRD patterns declare that under argon atmosphere only metalboride phase has been crystallized and it was not seen any oxide phase of metals. TEM image depicts that PVP stabilized nano particles are square shaped particles that containing many nanoclusters. Cubic Co–La–Zr–B nano particles were also confirmed by SEM image. Co–La–Zr–B is highly active catalysts for hydrogen generation from the hydrolysis of sodium borohydride. The reported work also includes the full experimental details for the collection of a wealth of kinetic data to determine the activation energy (E_a = 53 kJ mol⁻¹) and effects of the catalyst dosage, amount of NaBH₄, and temperature on the rate of the catalytic hydrolysis of sodium borohydride. Catalytic hydrolysis of NaBH₄ is first order with respect to the catalyst concentration and also first order to the NaBH₄ concentration in the case of cubic Co–La–Zr–B nano particles.     

Optimization of synthesis parameters for catalytic performance of Ni–B catalysts using response surface methodology

Hydrogen production through hydrolysis of sodium borohydride (NaBH₄) by using metal catalysts is promising for fuel cell applications. Nickel (Ni) and its alloys are favorable due to their high catalytic activity, relatively low cost and availability. In present study, the effects of temperature, pH, reduction rate and reducing agent concentration, which significantly affect the catalyst performance, were investigated using the response surface methodology (RSM). A mathematical model was derived according to results which were obtained from four-level orthogonal Taguchi L16 (4⁴) experimental design used for the optimization of multiple parameters in the process. From the RSM analyses, that compatible with the predicted experimental results, maximum hydrogen generation rate (HGR) 49.81 L min^?1 g_cat^?1 was obtained temperature of 278.12 K, pH of 5.52, reducing agent concentration of 85.96 NaBH₄.water^?1 and reduction rate of 6.82 mL min^?1. Analysis of variance reveals that both pH and rate of reduction have significant effect than the temperature on the HGR.     

A novel and active ruthenium based supported multiwalled carbon nanotube tungsten nanoalloy catalyst for sodium borohydride hydrolysis

At present, a novel and active catalyst, RuW/MWCNT catalyst, was successfully synthesized to complete the hydrolysis reaction of sodium borohydride (NaBH₄). The activity of Ru catalyst was increased by adding tungsten (W) to ruthenium (Ru) on multi-walled carbon nanotube (MWCNT) support. Surface characterization of the catalyst was performed with scanning electron microscope (SEM-EDX), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmissing electron microscope (TEM) analysis methods. SEM-EDX revealed that RuW (95:5) catalyst metal ratio was obtained at desired nominal ratio. XRD characterization revealed that W addittion to the Ru structure increased its activity by forming an alloy. W addition Ru altered the electronic structure of the Ru. Parameters affecting the hydrolysis performance of RuW/MWCNT catalyst such as temperature, amount of catalyst, NaBH₄ concentration and sodium hydroxide (NaOH) concentration were investigated. Adding NaOH to the reaction vessel reduced the activity of the RuW/MWCNT catalyst. From the hydrolysis measurements, the activation energy of RuW(95–5)/MWCNT catalyst was found to be 16.327 kjmol^?1, the reaction order as 0.61 and the initial rate as 95,841,4 mL H₂g_catmin^?1. The stability of the RuW/MWCNT catalyst was tested using 5 times and it was observed that this novel RuW/MWCNT catalyst could complete the hydrolysis reaction despite repeated use.     

Bacterial cellulose derived carbon as a support for catalytically active Co–B alloy for hydrolysis of sodium borohydride

The fast release of hydrogen from borohydride is highly desired for a fuel cell system. However, the generation of hydrogen from borohydride is limited by the low activity and low stability of the catalyst. Herein, a highly active catalyst is synthesized through a simple one-step chemical reduction using bacterial cellulose (BC) derived carbon as a support for the active Co–B alloy. The morphology and microstructure of the BC/Co–B nanocomposite are characterized by SEM, TEM, XRD, and BET adsorption analysis. The BC/Co–B possesses high surface area (125.31 m² g^?1) high stability and excellent catalytic activity for the hydrolysis of NaBH₄. Compared with unsupported Co–B nanocomposite or commercial carbon supported Co–B, the BC/Co–B nanocomposite shows greatly improved catalytic activity for the hydrolysis of NaBH₄ with a high hydrogen generation rate of 3887.1 mL min^?1 g^?1 at 30 °C. An activation energy of 56.37 kJ mol^?1 was achieved for the hydrolysis reaction. Furthermore, the BC/Co–B demonstrated excellent stability. These results indicate that the BC/Co–B nanocomposite is a promising candidate for the hydrolysis of borohydrides.