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.     

Apricot Kernel shell waste treated with phosphoric acid used as a green,metal-free catalyst for hydrogen generation from hydrolysis of sodium borohydride

In this study, grinded apricot kernel shell (GAKS) biobased waste was used for the first time as a cost-effective, efficient, green and metal-free catalyst for hydrogen generation from the hydrolysis reaction of sodium borohydride (NaBH₄). For the hydrogen production by NaBH₄ hydrolysis reaction, GAKS was treated with various acids (HCl, HNO₃, CH₃COOH, H₃PO₄), salt (ZnCl₂) and base (KOH). As a result, the phosphoric acid (H₃PO₄) demonstrated better catalytic activity than other chemical agents. The hydrolysis of NaBH₄ with the GAKS-catalyst (GAKS_cat) was studied depending on different parameters such as acid concentration, furnace burning temperature and time, catalyst amount, NaBH₄ concentration and hydrolysis reaction temperature. The obtained GAKS_cat was characterized by ICP-MS, elemental analysis, TGA, XRD, FT-IR, Boehm, TEM and SEM analyses and was evaluated for its catalytic activity in the hydrogen production from the hydrolysis reaction of NaBH₄. According to the results, the optimal H₃PO₄ percentage was found as 15%. The maximum hydrogen generation rate from the hydrolysis of NaBH₄ with the GAKS_cat was calculated as 20,199 mL min⁻¹ g_cat⁻¹. As a result, it can be said that GAKS treated with 15% H₃PO₄ as a catalyst for hydrogen production is an effective alternative due to its high hydrogen production rate.     

Phosphorus and oxygen doped carbon-based on Spirulina microalgae as efficient metal-free catalysts to obtain H2 from methanolysis of NaBH4

Metal-free catalysts (SP–KOH–P) doped phosphorus and oxygen as a result of modification with H₃PO₄ to the surface of the activated carbon sample (SP–KOH) obtained by activation of KOH with Spirulina microalgae were used to obtain hydrogen (H₂) from methanolysis of NaBH₄. The characteristic structure of SP-KOH-P and SP-KOH metal-free catalysts were examined by XRD, TEM, elemental analysis, FTIR, and ICP-MS. The effects of the amount of catalyst, NaBH₄ concentration, reusability, and temperature on H₂ production rate from NaBH₄ methanolysis reaction were investigated. The hydrogen production rate (HGR) obtained with 25 mg SP-KOH-P was found to be 19,500 mL min^?1 g^?1. The activation energy (Ea) value of SP-KOH-P metal-free catalyst sample was calculated as 38.79 kJ mol^?1.     

Spirulina Platensis microalgae strain modified with phosphoric acid as a novel support material for Co–B catalysts: Its application to hydrogen production

Spirulina platensis is defined as the dried biomass of cyanobacteria in commercial use and is biomass with high carbon content. Spirulina platensis microalgae strain supported-CoB catalysts to produce hydrogen from sodium borohydride (NaBH₄) were prepared for the first time. The Spirulina platensis microalgae strain was modified with phosphoric acid (H₃PO₄) to proton. Then, the supported catalyst was performed to produce hydrogen from NaBH₄ hydrolysis. The optimum H₃PO₄ concentration, optimum Co amount, and optimum impregnation time of the H₃PO₄ with the microalgae strain were investigated. The maximum hydrogen production rate for the 30% CoB catalyst supported on microalgae strain treated with H₃PO₄ was found to be 3940 mL min⁻¹g⁻¹catalyst. X-ray powder diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), and scanning electron microscope (SEM) analysis were performed for characterization of CoB catalyst supported on Spirulina microalgae strain. After four consecutive uses, the performance and conversion values of this catalyst were investigated. At the same time, the effect of temperature on the hydrogen production from this hydrolysis reaction was examined. The activation energy with the CoB catalyst supported on Spirulina microalgae strain was calculated as 35.25 kJ mol⁻¹. According to the kinetic model of a power law, n value was found as 0.25 for kinetic studies.     

Ethylene glycol as an alternative solvent approach for very efficient hydrogen production from sodium borohydride with phosphoric acid and acetic acid catalysts

For the first time, phosphoric acid (H₃PO₄) and acetic acid (CH₃COOH) catalysts were used for efficient hydrogen (H₂) production from sodium borohydride (NaBH₄) ethylene glycolysis reaction. In this experimental study, the effects of ethylene glycol/water ratio, ethylene glycol/acid ratio, NaBH₄ concentration, acid concentration, and temperature were investigated. These ethylene glycol/water ratio experiments showed that the use of water alongside ethylene glycol negatively affects H₂ production. The hydrogen generation rate (HGR) values obtained for this ethylene glycolysis reaction with 1 M H₃PO₄ and 1 M CH₃COOH catalysts are 5800 and 4542 mLmin^-1, respectively. Also, the completion times of ethylene glycolysis reactions with these acids are 8 and 10 s, respectively. The n value obtained for ethylene glycolysis reactions according to the power-law kinetic model was 0.50. The activation energies obtained with H₃PO₄ and CH₃COOH catalysts were 24.45 kJ mol^?1and 33.23 kJ mol^?1, respectively.     

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.     

Investigation of hydrogen generation from sodium borohydride using different cobalt catalysts

Effective Co/Cu, CoB/Cu, and CoBM (M = Mo,Zn,Fe)/Cu catalysts were prepared on the copper surface by a simple electroless deposition method using a morpholine borane as a reducing agent in the glycine solution. The activity of the deposited catalysts was investigated for hydrogen generation from an alkaline sodium borohydride solution. It was determined that these synthesized catalysts demonstrated the catalytic activity for the hydrolysis reaction of NaBH₄. The lowest obtained activation energy (E_A) of the hydrolysis reaction of NaBH₄was 27 kJ mol^?1 for the CoBMo/Cu catalyst. The hydrogen generation rate of 15.30 ml min^?1 was achieved using CoBMo/Cu catalysts at 313 K and it increased ~3.5 times with the increase of temperature to 343 K. The highest hydrogen generation rate obtained by CoBMo/Cu films may be related to the hierarchical cauliflower-shaped 3D structures and the high roughness surface area. Moreover, the CoBMo/Cu catalyst showed an excellent reusability.     

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.     

Protection and confinement effect of carbon on Co/CoxOy nano-catalyst for efficient NaBH4 hydrolysis

The hydrolysis of sodium borohydride (NaBH₄) over catalysts is a promising method to produce hydrogen. Although Co-based catalysts exhibit high activity for NaBH₄ hydrolysis, they are still far from satisfying practical applications, especially their poor durability in alkaline media. Herein, a carbon shell structure was designed and synthesized to improve the stability of the mixture of Co⁰ and Co_xO_y nanofilms (Co/Co_xO_y@C) during NaBH₄ hydrolysis via a facile polymerization-pyrolysis strategy with Co/Co_xO_y nanofilms as the precursor. As a result, the Co/Co_xO_y@C catalyst can achieve a remarkable H₂ generation rate of 4348.6 mL min^?1 g_Co^?1 with a low activation energy of 43.6 kJ mol^?1, which is superior to most previously reported catalysts. Moreover, the catalyst shows high stability with an H₂ generation-specific rate of 79% after five cycles. The excellent performance of carbon substrate can well prevent the agglomeration of Co-based nanoparticle and improve the corrosion resistance of the active Co to BO₂^? and OH^?. This work would widen the road for the preparation of nanoconfined catalysts, which has prospective application potentials for H₂ production from NaBH₄ hydrolysis.     

Synthesis of solid-state NaBH4/Co-based catalyst composite for hydrogen storage through a high-energy ball-milling process

Solid-state composites of NaBH₄ and Co-based catalyst have been fabricated for hydrogen generation via a novel mechanochemical technique, i.e. the high-energy ball milling, in which the gravimetric storage capacity of hydrogen has reached 6.7 wt%, meeting the 2010 target of at least 0.06 kg H₂/kg set by the U.S. Department of Energy (DOE). The active catalysts used in the hydrolysis reaction of sodium borohydride for hydrogen generation are mainly cobalt oxides. Controlled addition of water, namely water used as a limiting agent, to the solid composites of NaBH₄ and Co-based catalyst greatly improves the H₂ storage capacity and resolved the issues of low gravimetric H₂ storage in conventional aqueous system of sodium borohydride. Factors influencing the performance of hydrogen production such as amounts of H₂O added, catalyst loadings and durations of ball-milling processes are investigated. Moreover the hydrolyzed products of NaBH₄ and spent catalysts are analyzed as well.     

Electroless-deposited Co–P catalysts for hydrogen generation from alkaline NaBH4 solution

Cobalt–phosphorus (Co–P) catalysts, which were electroless deposited on Cu sheet, have been investigated for hydrogen generation from alkaline NaBH₄ solution. The microstructures of the as-prepared Co–P catalysts and their catalytic activities for hydrolysis of NaBH₄ are analyzed in relation to pH value, NaH₂PO₂ concentration, and the deposition time. Experimental results show that the Co–P catalyst formed in the bath solution with pH value of 12.5, NaH₂PO₂ concentration of 0.8 M, and the deposition time no more than 6 min presents the highest hydrogen generation rate of 1846 mL min⁻¹ g⁻¹. Furthermore, the as-prepared catalyst also shows good cycling capability and the corresponding activation energy is calculated to be 48.1 kJ mol⁻¹. The favorable catalytic performance of the electroless-deposited Co–P catalysts indicates their potential application for quick hydrogen generation from hydrolysis of NaBH₄ solution.     

Preparation and catalytic activity of wheat straw cellulose based hydrogel-nanometal composites for hydrogen generation from NaBH4 hydrolysis

A novel WSC (wheat straw cellulose) based hydrogel was prepared by solution polymerization and then applied as a template for in situ preparation of Ni and Cu nanoparticles for further utilization as catalyst in hydrogen generation from the hydrolysis of NaBH₄. SEM with EDS, XRD, TGA, XPS and BET surface area analyses were employed to characterize the structure of WSC based hydrogel-nanometal (Ni or Cu) composites. The effects of several parameters such as the mesh size of catalyst, the amount of catalyst, the initial concentration of NaBH₄ and the reaction temperature were studied. Based on the analysis of kinetics of the hydrolysis reaction of NaBH₄ at different temperatures, the activation energy was 32.66 (34.83) kJ mol^?1 for WSC based hydrogel-Ni (Cu) composites. The WSC based hydrogel-Ni (Cu) composites can be used up to 5 times with 100% conversion and 77.5% (70%) activity. When the catalyst was stored for 30 days, the catalyst was remained 70% activity for hydrogel-Ni composites and 65% activity for hydrogel-Cu composites, respectively.     

A study on hydrogen generation from NaBH4 solution using Co-loaded resin catalysts

Hydrogen production via chemical processes has gained great attention in recent years. In this study, Co-based complex catalyst obtained by adsorption of Co metal to Amberlite IRC-748 resin and Diaion CR11 were tested for hydrogen production from alkaline NaBH₄ via hydrolysis process. Their catalytic activity and microstructure were investigated. Process parameters affecting the catalytic activity, such as NaOH concentration, Co percentage and catalyst amount, as well as NaBH₄ concentration and temperature were investigated. Furthermore, characteristics of these catalysts were carried out via SEM, XRD and FT-IR analysis. Hydrogen production rates equal to 211 and 221 ml min⁻¹ g_cat⁻¹ could be obtained with Amberlite IRC-748 resin and Diaion CR11 Co based complex catalysts, respectively. The activation energies of the catalytic hydrolysis reaction of NaBH₄ were calculated as 46.9 and 59.42 kJ mol⁻¹ for Amberlite IRC-748 resin and Diaion CR11 based catalysts respectively kJ mol⁻¹ from the system consisting of 3% Co, 10 wt% NaBH₄ and 7 wt% NaOH as well as 50 mg catalyst dosage. It can be concluded that Co-based resins as catalysts for hydrogen production is an effective alternative to other catalysts having higher rate.     

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).     

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.     

A novel cost-effective catalyst from orange peel waste protonated with phosphoric acid for hydrogen generation from methanolysis of NaBH4

In this study, orange peel (OP), one of the organic wastes, was first used as a metal-free catalyst for the production of hydrogen from sodium boron hydride (NaBH₄). In order to prepare an orange peel catalyst (OP–H₃PO₄-Cat) with the best catalytic activity, experiments were carried out on pure orange peel with different acid types, different burning temperatures and different burning times. As a result of these experiments, it was determined that OP-H₃PO₄-Cat treated with 30% H₃PO₄ and burned at 400 °C for 45 min had the best catalytic activity. The OP-H₃PO₄-Cat material was characterised by several techniques such as FTIR, XRD and SEM. As a result, the hydrogen generation rates (HGR) at 30 °C and 60 °C in the methanolysis reaction of 2.5% NaBH₄ catalysed by OP-H₃PO₄-Cat were found as 45,244 and 61,892 mLmin^?1g.cat^?1, respectively. The activation energy of OP-H₃PO₄-Cat catalyst was calculated as 12.47 kJmol^-1.     

Preparation of CoB/ZIF-8 supported catalyst by single step reduction and its activity in hydrogen production

CoB/ZIF-8 supported catalysts were successfully prepared using Co/Zn-ZIF-8 as the precursor by single-step reduction, which was applied in hydrogen release from the hydrolysis of NaBH₄. Reducible Co ions of Co/Zn-ZIF-8 can be partially in-situ transformed into CoB by direct reduction, whereas ZIF-8 framework structure can be well preserved due to the resistance of Zn to reducing ambiences. Accordingly, CoB active components can be highly loaded onto ZIF-8 support to produce CoB/ZIF-8 catalysts. The texture evolution of Co/Zn-ZIF-8 during reduction was investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscope and nitrogen adsorption–desorption isotherms. Compared with the reduction of Co-ZIF-67, the framework structure of Co/Zn-ZIF-8 can be effectively preserved although Co ions of Co/Zn-ZIF-8 were partially reduced into cobalt-based alloy. In the hydrogen release from hydrolysis of NaBH₄, CoB/ZIF-8 supported catalyst exhibits excellent catalytic activity. The effect of NaOH concentration, NaBH₄ concentration and reaction temperature on hydrolysis reaction of NaBH₄ was deeply studied based on this catalyst. Compared with other published catalysts, this catalyst exhibits relatively low activation energy of about 57.72 kJ mol^?1.     

Polypyrrole supported Co–W–B nanoparticles as an efficient catalyst for improved hydrogen generation from hydrolysis of sodium borohydride

Effective and reusable catalysts with high performance are essentially necessary for NaBH₄ based on-demand hydrogen generators to the widespread use for energy conversion in fuel cell power systems. Herein, we report a facile synthesis of surfactant-directed polypyrrole-supported Co–W–B nanoparticles as a robust catalyst for efficient hydrolysis of NaBH₄ reaction. This non-noble metal catalyst provides much higher catalytic activity than a conventional cobalt boride catalyst. By incorporating tungsten to catalyst composition and tuning molar ratio of W/(Co + W), about a four-fold higher hydrogen generation rate was attained compared to bare Co–B. Among the all catalysts tested, Co–W–B/PPy with 7.5% W possessed the remarkable catalytic performance of 9.92 L min^?1 g^?1 and high stability over five cycles with the apparent activation energy of 49.18 kJ mol^?1.     

Mechanistic implications of the solvent kinetic isotope effect in the hydrolysis of NaBH4

The sodium borohydride, NaBH₄, hydrolysis mechanism is studied via the H₂O/D₂O kinetic isotope effect (KIE). This reaction is of importance as NaBH₄ is considered as a hydrogen storage material. Nowadays, hydrogen is thought to be one of the most promising and efficient clean energy carriers. In order to control the rate of the hydrogen evolution reaction (HER), one has to understand the mechanism of its production. The H₂O/D₂O KIE of the reactions of NaBH₄ and NaBD₄ with water was studied in solutions containing a ratio of H₂O/D₂O = 1.00. The separation factor, α, of both reactions is α = 5.0 ± 1.0. The rate of the hydrolysis of BD₄^? in H₂O is faster than that of BH₄^?. The results point out that the rate-determining step in all hydrolysis stages is the H–OH bond scission.     

Catalytic hydrolysis of NaBH4 over titanate nanotube supported Co for hydrogen production

A Co/HTNT catalyst is developed by immobilizing Co on the surface of titanate nanotubes. The microstructure and composition of the catalyst are investigated with atomic absorption spectroscopy (AAS), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR) and X-ray photoelectron spectroscopy (XPS). The developed Co/HTNT catalyst shows great performance in catalyzing NaBH₄ hydrolysis. The hydrolysis of 25 mg NaBH₄ catalyzed by 50 mg Co/HTNT in 10 g NaOH solution (12.5 wt%) provides a hydrogen production rate of 1.04 L min^?1 g_Co^?1 at 30 °C, and the activation energy of the reaction is 29.68 kJ mol^?1. The high catalytic activity and economical property make this catalyst a promising choice for on-site hydrogen production from NaBH₄ hydrolysis.