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.     

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.     

Hydrogen generation from alkaline NaBH4 solution using a dandelion-like Co–Mo–B catalyst supported on carbon cloth

In this study, a dandelion-like Co–Mo–B catalyst was prepared on carbon cloth (CC) by two-step electrodeposition method for the first time. The composition and microscopy are characterized by XRD and SEM technology. The results revealed that the as-synthesized Co–Mo–B catalyst exhibited high hydrogen generation rate (1280.80 mL min^?1 g^?1) and low activation energy (51.0 kJ mol^?1) for the hydrolysis of alkaline NaBH₄ solution. The results reveal that the reason might be due to high specific surface of the novel dandelion-like nanostructure and the synergistic effect of Co, Mo and B. Moreover, the catalytic activity was closely related to NaOH concentration, and OH^– anions were competitive with BH₄^– anions in alkaline NaBH₄ solution to transfer to the catalyst surface.     

Effect of phosphoric acid and acetic acid addition on the hydrogen evolution using Ni based catalyst prepared in ethanol,methanol, and water solvents

Ni-based catalysts were synthesized in water, methanol and ethanol solvents by chemical reduction with sodium borohydride (NaBH₄). The obtained catalyst for the first time was used to catalyze the NaBH₄ hydrolysis reaction with phosphoric acid and acetic acid including different concentrations. The maximum hydrogen production rates obtained in the hydrolysis reaction including 0.5 M phosphoric acid and 0.1 M acetic acid of the Ni-based catalyst prepared in ethanol solvent were 5214 and 3650 ml g^?1 min^?1, respectively.     

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

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

Cobalt nanoparticles supported on magnetic core-shell structured carbon as a highly efficient catalyst for hydrogen generation from NaBH4 hydrolysis

A novel recyclable cobalt nanocatalyst, supported on magnetic carbon with core-shell structure, was successfully synthesized by using wetness impregnation-chemical reduction method for hydrogen generation from hydrolysis of NaBH₄. The resultant nanocomposite was characterized to determine the structural and physical-chemical properties by a series of analytical techniques such as FT-IR (Fourier transform infrared spectroscopy), XRD (X-ray diffraction), SEM (scanning electron microscope), EDX (energy-dispersive X-ray spectroscopy), TEM (transmission electron microscopy), etc. The results demonstrated that amorphous cobalt nanoparticles were homogeneously surrounded on the surface of the support due to having abundant hydrophilic groups (such as aldehyde and hydroxyl groups) on the surface of carbon layer for the effective immobilization of metal ions. The supported catalyst showed superior catalytic performance towards the hydrolysis reaction of NaBH₄ at room temperature. The total rate of hydrogen generation and activation energy were calculated to be 1403 ml H₂ g_cat^?1 min^?1 and 49.2 kJ mol^?1, respectively, which were comparable to the values of most cobalt-based catalyst reported for hydrogen production from hydrolysis of NaBH₄. Additionally, reusability test revealed that the hydrogen in NaBH₄ substrate could be completely released within 25 min with a minimum hydrogen generation rate of 832 ml H₂ g_cat^?1 min^?1 even after five runs of hydrolytic reaction, implying the as-prepared Co/Fe₃O₄@C composite could be considered as a promising candidate catalyst for portable hydrogen fuel system such as PEMFC (proton exchange membrane fuel cells).     

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.     

Chitosan-mediated Co–Ce–B nanoparticles for catalyzing the hydrolysis of sodium borohydride

Highly dispersed Co–Ce–B nanoparticles supported on chitosan-derived carbon (Co–Ce–B/Chi–C) were synthesized through chemical reduction and carbonization. The morphology and microstructure of the Co–Ce–B/Chi–C nanocomposite were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Brunauer–Emmett–Teller adsorption analysis. This nanocomposite had uniform morphology and large surface area, and it showed high catalytic activity for NaBH₄ hydrolysis and good cycle stability. Compared with unsupported Co–Ce–B particles, this nanocomposite showed greatly increased catalytic activity for NaBH₄ hydrolysis. A remarkably high hydrogen generation rate of 4760 mL^?1 min^?1 g^?1 at 30 °C was achieved with low activation energy of 33.1 kJ mol^?1. These results indicate that the Co–Ce–B/Chi–C nanocomposite is a promising catalyst for on-demand hydrogen generation via NaBH₄ hydrolysis.     

Effect of Al2O3-supported Cu-Schiff base complex as a catalyst for hydrogen generation in NaBH4 hydrolysis

Cu-Schiff base complex which we previously synthesized (Kilinc et al., 2012) is supported on Al₂O₃. The prepared catalyst is characterized by using SEM, XRD, BET, and FT-IR methods. And Al₂O₃-supported complex is used as a catalyst in NaBH₄ hydrolysis reaction for hydrogen generation. NaBH₄ hydrolysis reactions are investigated depending on the concentration of NaBH₄ and NaOH, temperature, percentage of Cu complex, and amount of catalyst. Maximum reaction rates are 44,453.33 and 57,410.00 mL H₂/g.cat.min at 30°C and 50°C, respectively. The activation energy of NaBH₄ hydrolysis reaction is found as 225,775 kJ^.mol^?1. All the experimental results and literature comparisons show that Al₂O₃-supported Cu-Schiff base complex is a very effective catalyst in NaBH₄ hydrolysis for H₂ generation.     

Solution combustion synthesized lithium cobalt oxide as a catalytic precursor for the hydrolysis of sodium borohydride

Solution combustion synthesis (SCS) has recently been explored as one method to synthesize metal oxides (e.g. Co₃O₄) that can serve as catalytic precursors for the hydrolysis of sodium borohydride (NaBH₄). In this work, SCS is used to produce the mixed metal oxide lithium cobalt oxide (LiCoO₂) from a solution of cobalt nitrate, lithium acetate, and glycine. Its subsequent use as an effective catalyst precursor for NaBH₄ hydrolysis is characterized and compared to commercially available LiCoO_2. To remove residual impurities from the SCS material the materials were heated at a rate of 10 °C min^?1 and held for 2 h at temperatures ranging from 500 to 800 °C and subsequently characterized. It was found that the layered phase of LiCoO₂ results at heat treat temperatures above 700 °C. Using a 0.6 wt.% aqueous solution of NaBH₄ at 25 °C and a 1 wt.% catalyst precursor loading, an optimized HGR of 2.09 L min^?1 g_cat^?1 was achieved for the solution combustion synthesized LiCoO₂. In contrast, at the same conditions, a HGR of 0.29 L min^?1 g_cat^?1 was obtained for commercial materials even though the specific surface area was much higher.     

Highly stable and controllable CoB/Ni-foam catalysts for hydrogen generation from alkaline NaBH4 solution

In this work, a series of shaped CoB/Ni-foam catalysts were directly synthesized by using a convenient and simple electroless plating method. Despite the low loading amount of CoB, the catalysts showed high catalytic performance in the hydrolysis of NaBH₄ solution, and the maximum hydrogen generation rate reached 1930 mL min^?1 (g CoB)^?1 in 1 wt % NaBH₄ + 5 wt % NaOH solution at 293 K. The catalysts demonstrated distinct stability, and the hydrogen generation rate was almost unchanged after 6 cycles. Furthermore, the catalysts could be easily recovered from the reaction system by a magnet. These characteristics make CoB/Ni-foam a high performance and cost effective catalyst for practical applications of hydrogen generation.     

Carbon spheres from lactose as green catalyst for fast hydrogen production via methanolysis

Micrometer sized carbon spheres (CSs) are prepared in a single step using lactose precursor via hydrothermal method. These CSs are chemically modified with 3-chloro-2-hydroxypropyl ammonium chloride (CHPACl) and triethylenetetramine (TETA) to generate amine groups on the particle surface. Modified CSs with TETA was protonated with HCl as CSs-TETA-HCl that the zeta potential is increased to +40.3 ± 0.70 from ?51.4 ± 4.66 mV. The catalytic performance of CSs are tested as catalysts in the methanolysis of NaBH₄, and the best catalytic performance as 2586 mL min^?1 g^?1 hydrogen generation rate (HGR) was obtained by CSs-TETA-HCl catalyst at 298 K as metal free catalyst. Furthermore, various parameters such as the amount of NaBH₄, the reaction temperature, and the reusability of CSs-TETA-HCl particles are investigated. More importantly, relatively low activation energy, 23.82 kJ mol^?1 for CSs-TETA-HCl catalyzed NaBH₄ methanolysis reaction is obtained in comparison to metal nanoparticle and metal free catalysts reported for the same purpose in the literature.     

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.     

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.     

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.     

Effect of phosphoric acid addition on the hydrogen production from hydrolysis of NaBH4 with Cu based catalyst

Cu based catalysts were synthesized in water and methanol solvents by chemical reduction with sodium borohydride (NaBH₄). The obtained catalyst was used to catalyze the NaBH₄ hydrolysis reaction with phosphoric acid (H₃PO₄) including different concentrations. Surface morphology and structural properties of the Cu based catalysts prepared in water and methanol solvents were studied using by X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area measurements and Fourier-transform infrared spectroscopy (FTIR) analyses, respectively. The catalytic activity of the catalysts has been tested by measuring the hydrogen production rate by the acidified hydrolysis of NaBH₄. The maximum hydrogen production rates in the hydrolysis reaction including 0.25 M H₃PO₄ using the Cu based catalyst prepared in water and methanol solvents were 825 and 660 ml g^?1min^?1, respectively. At the same time, the hydrogen production experiments were carried out from this hydrolysis reaction with only H₃PO₄ and NaBH₄ interactions without using Cu metal catalyst. The activation energy obtained based on the nth order reaction model was found to be 61.16 kJ mol^?1.     

Experimental studies on the catalytic behavior of alloy and core-shell supported Co-Ni bimetallic nano-catalysts for hydrogen generation by hydrolysis of sodium borohydride

Monometallic (Co) and bimetallic (Co-Ni and Co-Cu) oxides catalysts supported on the almond based activated carbon (AC) were prepared by the heterogeneous deposition-precipitation method. The activity of these catalysts was evaluated as a function of reaction temperature, NaOH, and NaBH₄ concentration. Several analysis methods including XRD, XPS, FTIR, TEM, FESEM, ICP-OES, and BET were applied to characterize the structure of prepared samples. Well-dispersed supported bimetallic nano-catalysts with the size of particles below 20 nm were formed by using nickel and copper oxides as a promoter which was confirmed by XRD and TEM techniques. Surface composition of alloy and core-shell cobalt-nickel oxides catalysts was analyzed by ICP-OES which was in a good agreement with nominal content during catalyst preparation. The performance of bimetallic cobalt-nickel oxides catalysts indicated the synergic effect between cobalt and nickel in comparison with monometallic and bimetallic cobalt-copper samples for hydrogen production. Maximum hydrogen generation rate was measured for the supported core-shell catalyst as named Ni1/Co3/AC. The reaction rate increased with increasing the temperature of the alkaline solution as a significant parameter while other operating conditions were kept constant. The optimal values for NaOH and NaBH₄ content were calculated to be 10 wt % for both variables at 30 °C. Hydrogen production rates were calculated to be 252.0, 310.8 and 658.8 mL min^?1.g^?1 by applying Co3/Ni1/AC, Co3-Ni1/AC (alloy) and Ni1/Co3/AC at 30 °C in 5 wt % NaBH₄ and 5 wt % NaOH solutions, respectively. Obtained activation energy (50 kJ mol^?1) illustrated that the suitable catalysts were synthesized for hydrogen generation. The experimental study showed that the hydrolysis of NaBH₄ was a zero-order type reaction with the respect to the sodium borohydride concentration. A semi empirical kinetic model was derived at the various temperatures and NaOH concentrations.     

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.     

Superior hydrogen generation from sodium borohydride hydrolysis catalyzed by the bimetallic Co–Ru/C nanocomposite

Sodium borohydride has been widely regarded as a promising hydrogen carrier owing to its greatly hydrogen storing capability (10.8 wt%), high weight density and excellent stability in alkaline solutions. Herein, we first design and synthesize a series of bimetallic M-Ru/C nanocomposites (including Fe–Ru/C, Co–Ru/C, Ni–Ru/C and Cu–Ru/C), via simply alloying of commercial Ru/C with nonprecious metal, for superior H₂ evolution from the NaBH₄ hydrolysis. The result exhibits that H₂ generation is synergetically improved by alloying Ru/C with Co or Ni, while it is hindered by alloying Ru/C with Fe or Cu. Indeed, Co–Ru/C presents the highest efficient catalytic activity for H₂ generation, with the TOF of 117.69 mol(H₂)·mol_Ru^?1·min^?1, whereas Ru/C is only 57.08 mol(H₂)·mol_Ru^?1·min^?1. In addition, the TOF of Co–Ru/C reaches to 436.51 mol(H₂)·mol_Ru^?1·min^?1 (96.7 L(H₂)·g_Ru^?1·min^?1) in the presence of NaOH.     

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.