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.     

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.     

CoB doped acid modified zeolite catalyst for enhanced hydrogen release from sodium borohydride hydrolysis

Cobalt-boron (CoB) catalyst supported on zeolite modified with hydrochloric acid (CoB-zeolite-HCl) and zeolite modified with acetic acid (CoB-zeolite-CH₃COOH) is prepared for the hydrogen (H₂) release from sodium borohydride (NaBH₄). The supported catalyst samples were characterized by X-ray diffraction spectroscopy (XRD), scanning electron microscope (SEM), Fourier transforms infrared spectroscopy (FTIR), nitrogen adsorption and, inductively coupled plasma optical emission spectroscopy (ICP-OES). The effects of Co metal loading, NaBH₄ concentration, NaOH concentration, temperature, and reusability on the catalytic performance of the CoB-zeolite-HCl catalyst were investigated. The completion time of the reaction using the raw zeolite supported CoB catalyst was about 265 min. However, the completion time of the reaction using the CoB-zeolite-HCl catalyst was decreased to about 80 min. BET surface area values showed that there is a 7-fold increase in the specific surface area for the zeolite activated with HCl compared to the BET surface area for the raw zeolite. The activation energy (Ea) of the catalyzed reaction was 42.45 kJ mol⁻¹.     

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.     

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.     

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.     

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.     

Preparation of CoB catalysts supported on raw and Na-exchanged bentonite clays and their application in hydrogen generation from the hydrolysis of NaBH4

The aim of this work is to prepare CoB catalysts supported on raw bentonite (CoB/bentonite) and Na-exchanged bentonite (CoB/Na-bentonite) by the impregnation and chemical reduction method. The prepared catalysts were characterized using X-ray diffractometry (XRD), X-ray fluorescence spectroscopy (XRF), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier transform infrared spectroscopy (FTIR) techniques. The activities of the catalysts were tested in the hydrolysis reaction of sodium borohydride (NaBH₄) in a semi-batch system. The volume of the evolved hydrogen gas was determined by a water displacement method. The effects of catalyst amount, NaOH (a base stabilizer) concentration, NaBH₄ concentration and solution temperature on the hydrogen generation rate were investigated. The maximum hydrogen generation rates were determined as 921.94 mL/min.g_cat for CoB/bentonite and 1601.45 mL/min.g_cat for CoB/Na-bentonite when the 5 wt % NaBH₄ and 10 wt % NaOH solutions were used at 50 °C. The activation energies (E_a) of the hydrolysis reaction over CoB/bentonite and CoB/Na-bentonite were determined as 55.76 and 56.61 kJ/mol, respectively.     

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.     

Magnetic dendritic KCC-1 nanosphere-supported cobalt composite as a separable catalyst for hydrogen generation from NaBH4 hydrolysis

The introduction of magnetism into a catalyst can greatly optimize its separation performance. In the present work, a kind of magnetically separable catalysts for promoting NaBH₄ hydrolysis have been fabricated by anchoring cobalt nanoparticles on magnetic dendritic KCC-1 nanospheres composed of magnetic Fe₃O₄ core and fibrous shell. The fabricated catalysts were characterized with various characterization methods, including absorption spectroscopy (AAS), scanning electron microscopy (SEM), high-resolution transmission electronic microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometry (VSM), and Fourier transform infrared (FT-IR), etc. This kind of catalysts exhibit high catalytic activity for promoting the hydrolysis of NaBH₄ under alkaline conditions, giving a hydrogen generation rate and activation energy of 3.83 L min⁻¹ g_Co⁻¹ (30 °C) and 53.63 kJ mol⁻¹, respectively. After used for 5 cycles, the catalyst showed 36.5% catalytic activity reserved. Most importantly, the magnetism of the catalyst made it easily separated and recycled from the solution after the reaction completed. The development of this kind of catalysts could provide a promising option for catalyzing NaBH₄ hydrolysis for portable hydrogen production from.     

PDMA cryogel beads as a catalyst for hydrogen generation from NaBH4 alcoholysis

Poly[2-(dimethylamino)ethyl methacrylate] cryogel beads were prepared under cryogenic conditions via free radical polymerization and used as a catalyst in the production hydrogen (H₂) from NaBH₄ by alcoholysis. The efficiency of the catalyst was investigated in the range of 0–40 °C by both methanolysis and ethylene glycolysis reactions, and its reuse was tested. Accordingly, it was observed that the methanolysis reaction was faster than the ethylene glycolysis reaction. When the hydrogen generation rate (HGR) values between 0 and 40 °C were compared, it was concluded that the methanolysis reaction rate increased from 1550 to 4800 mL.min⁻¹g⁻¹ and the ethylene glycolysis reaction rate increased from 923 to 3551 mL.min⁻¹g⁻¹. In the alcoholysis reaction catalyzed by PDMA cryogel beads, the activation energy was calculated as 19.34 and 22.77 kJ.mol⁻¹ for the methanolysis and ethylene glycolysis reactions, respectively. After six repetitions, the catalyst activity was calculated over 50% for NaBH₄ methanolysis and ethylene glycolysis.     

Rice husk derived graphene-like material: Activation with phosphoric acid in the absence of inert gas for hydrogen gas storage

In this study, the effect of concentration of phosphoric acid (H₃PO₄) towards the physicochemical properties of rice husk derived graphene (GRHA) in the absence of inert gas was investigated. From TGA analysis, it was found that GRHA 1:3 possessed the highest weight loss (24.66%) due to the highest reactivity towards H₃PO₄. The FTIR shows that graphene-like material was obtained as the –OH groups were vanished in GRHA structure after activation. Raman spectroscopy and XRD analysis indicated that the produced GRHA is in amorphous state and has few layers of graphene. GRHA 1:3 showed the greatest improvement in their porous structure including the highest surface area (315.07 m²/g) with the largest pore volume (0.2069 cm³/g) as compared to other samples. From the static adsorption test, it was confirmed that GRHA 1:3 stored the highest amount of hydrogen compared to other samples with 1.95 wt % contributed by its excellent porosity and surface area. To further understand the kinetics of hydrogen adsorption on GRHA, pseudo-first model and pseudo-second model was plotted. Pseudo second model was the best fitted model which indicated that the gas molecule adsorbed in the GRHA material via chemisorption. Additionally, from the kinetic study it was found that the adsorption process of GRHA 1:3 was controlled by multi-step adsorption process.     

Influence of process parameters on enhanced hydrogen generation via semi-methanolysis and semi-ethanolysis reactions of sodium borohydride using phosphoric acid

The sodium borohydride(NaBH₄) semi-methanolysis and semi-ethanolysis reactions to produce hydrogen are investigated using phosphoric acid(H₃PO₄) for the first time. The NaBH₄ concentration, H₃PO₄ concentration, and temperature parameters on these semi-alcoholysis reactions are evaluated. The normalized hydrogen generation rates (HGRs) obtained from the NaBH₄ semi-methanolysis and semi-ethanolysis acidified using 0.5 M H₃PO₄ are 11684 and 9981 ml min⁻¹ g⁻¹, respectively. Moreover, the completion times of these semi-methanolysis and semi-ethanolysis reactions with 0.5 M H₃PO₄ acid concentration are 0.10 and 0.116 min, respectively. Kinetic studies with the power-law model are evaluated. The activation energies(Ea) obtained for the NaBH₄ semi-methanolysis and semi-ethanolysis using 0.5 M H₃PO₄ are 9.08 and 32.47 kJ mol⁻¹, respectively.     

Fabrication and characterization of poly(tannic acid) coated magnetic clay decorated with cobalt nanoparticles for NaBH4 hydrolysis: RSM-CCD based modeling and optimization

Hydrogen generation from sodium borohydride (NaBH₄) hydrolysis in the presence of metal catalysts is a frequently used and encouraging method for hydrogen storage. Metal nanoparticle-supported catalysts are better recyclability and dispersion than unsupported metal catalysts. In this study, the synthesis and characterization of a polymer-supported catalyst for hydrogen generation using NaBH₄ have been investigated. For the synthesis of polymeric material, first of all, kaolin (KLN) clay has been magnetically rendered by using the co-precipitation method (Fe₃O₄@KLN) and then coated with poly tannic acid (PTA@Fe₃O₄@KLN). Then, the catalyst loaded with cobalt (Co) nanoparticles have been obtained with the NaBH₄ reduction method (Co@PTA@Fe₃O₄@KLN). The surface morphology and structural properties of the prepared catalysts have been determined using methods such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICP-MS) and vibrating sample magnetometer (VSM). The optimization of the most important variables (NaBH₄ amount, NaOH amount, catalyst amount, and metal loading rate) affecting the hydrolysis of NaBH₄ using the synthesized polymeric catalysts was carried out using response surface methodology (RSM). Depending on the evaluated parameters, the desired response was determined to be hydrogen production rate (HGR, mL/g min). HGR was 1540.4 mL/g_cat. min. in the presence of the Co@PTA@Fe₃O₄@KLN at optimum points obtained via RSM (NaBH₄ amount 0.34 M, NaOH amount 7.9 wt%, catalyst amount 3.84 mg/mL, and Co loading rate 6.1%). The reusability performance of the catalyst used in hydrolysis of NaBH₄ was investigated under optimum conditions. It was concluded that the catalyst is quite stable.     

Poly (acrylic acid)/polysaccharides IPN derived metal free catalyst for rapid hydrogen generation via NaBH4 methanolysis

Polymeric catalysts have displayed great performance for catalytic hydrogen generation. However, the reported metal free polymeric catalysts for NaBH₄ methanolysis are mainly limited to coating strategy where the catalytic activity fade after few cycles. Herein, we report an interpenetrating polymer network (IPN) strategy for rapid and highly recyclable NaBH₄ catalytic methanolysis to produce hydrogen (H₂) gas. In this study, we prepared poly(acrylic acid)/polysaccharide IPN via Pickering tempted polymerization. The hydrogen generation performance was studied employing different parameters where maximum HGR of 8182 mL H₂ min^?1 g^?1 of CAP. The activation energy Ea, enthalpy and entropy were calculated to be 62.99 kJ mol^?1, 32.25 kJ mol and ?130.92 J mol K^?1, respectively. Above all, CAP kept cyclic performance to 100% even at the 7th cycle. We confirmed the reproducibility of approach with other natural polysaccharides. This was due to strong chain entanglement of IPN synthesis which forces the active sites to stay in place during cyclic catalysis reaction. Thus, the IPN strategy ensures longer catalyst life for catalytic methanolysis of NaBH₄ for H₂ generation.     

Chlorella vulgaris microalgae strain modified with zinc chloride as a new support material for hydrogen production from NaBH4 methanolysis using CuB,NiB, and FeB metal catalysts

This study aims to produce hydrogen (HG) from sodium borohydride (NaBH₄) methanolysis using CuB, NiB or FeB catalysts prepared with a different support material including C. vulgaris microalgae strain modified using zinc chloride (CMS-ZnCl₂). The NaBH₄ concentration, metal percentage in the supported-catalyst, the optimal ZnCl₂ percentage, and temperature effect on the NaBH₄ methanolysis were investigated. X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), and Scanning electron microscopy (SEM) analysis were performed for the CMS-ZnCl₂-CuB characterization. Also, the low activation energy (Ea) of 22.71 kJ mol⁻¹ was found with the supported catalyst obtained. Under the same conditions, nearly 100% conversion was achieved in the reusability experiments repeated five times, but a gradual decrease in catalytic activity was observed after each use.     

Semi-methanolysis reaction of potassium borohydride with phosphoric acid for effective hydrogen production

The methanol and water solvents were used for the production of hydrogen from potassium borohydride. In addition, phosphoric acid was selected as the green catalyst so that this semi-methanolysis reaction would be more effective for the first time. The semi-methanolysis of potassium borohydride is investigated depend on potassium borohydride, phosphoric acid concentrations and temperatures. The maximum normalized hydrogen production rate obtained from this semi-methanolysis reaction with 1 M phosphoric acid as a catalyst was 5779 ml min ^?1 g^?1. In addition, this semi-methanolysis reaction was completed in 5 s. Kinetic studies have been carried out with the power law kinetic model. The activation energy obtained for this semi-methanolysis reaction is 1.45 kJ mol^?1.     

Co-P nanoparticles supported on dandelion-like CNTs-Ni foam composite carrier as a novel catalyst for hydrogen generation from NaBH4 methanolysis

We used the chemical vapor deposition method to prepare dandelion-like CNTs-Ni foam composite carrier, and then the electroless plating method was used to deposit Co-P nanoparticles on the CNTs of the CNTs-Ni foam. The CNTs-Ni foam and Co-P/CNTs-Ni foam were characterized by BET, SEM, XRD, XPS, and EDS. The results showed that CNTs were uniformly and densely grown in situ on the surface of Ni foam and were further successfully coated with Co-P nanoparticles. The Co-P/CNTs-Ni foam catalysts still maintained the dandelion-like structure and reached a maximum hydrogen production rate of 2430 mL min⁻¹ g⁻¹ at 25 °C. Furthermore, the Co-P/CNTs-Ni foam catalysts also exhibit a remarkable cycling performance and low activation energy (49.94 kJ mol⁻¹) for the methanolysis of sodium borohydride.     

Fly ash as catalyst support material in the hydrolysis of ethylenediamine bisborane for hydrogen production: The use of coal-fired power plant waste

Efficient, low-cost and safe new systems are still needed for the storage and usage of hydrogen energy, which is considered the most important energy source of the future. For this reason, the aim of this study was to prepare Co⁰, Ni⁰, and Cu⁰ composite catalysts with fly ash (FA) formed by combustion of coal in thermal power plants to be used for the dehydrogenation of ethylenediamine bisborane (EDAB) as a hydrogen source. In the hydrolysis reactions of EDAB, parameters such as metal type, catalyst concentration, temperature, and EDAB concentration were investigated. The FA-Cu⁰ composite catalyst was determined to be an effective catalyst system for hydrogen production by hydrolysis of EDAB from among the FA-M⁰ composite catalysts. Besides, FA can be used as an effective support material in order to prevent agglomeration of metal particles.     

Application of phosphoric acid and phytic acid-doped bacterial cellulose as novel proton-conducting membranes to PEMFC

Novel proton-conducting polymer electrolyte membranes have been prepared from bacterial cellulose by incorporation of phosphoric acid (H₃PO₄/BC) and phytic acid (PA/BC). H₃PO₄ and PA were doped by immersing the BC membranes directly in the aqueous solution of H₃PO₄ and PA, respectively. Characterizations by FTIR, TG, TS and AC conductivity measurements were carried out on the membrane electrolytes consisting of different H₃PO₄ or PA doping level. The ionic conductivity showed a sensitive variation with the concentration of the acid in the doping solution through the changes in the contents of acid and water in the membranes. Maximum conductivities up to 0.08 S cm⁻¹ at 20 °C and 0.11 S cm⁻¹ at 80 °C were obtained for BC membranes doped from H₃PO₄ concentration of 6.0 mol L⁻¹ and, 0.05 S cm⁻¹ at 20 °C and 0.09 S cm ⁻¹ at 60 °C were obtained for BC membranes doped from PA concentration of 1.6 mol L⁻¹. These types of proton-conducting membranes share not only the good mechanical properties but also the thermal stability. The temperature dependences of the conductivity follows the Arrhenius relationship at a temperature range from 20 to 80 °C and, the apparent activation energies (E_a) for proton conduction were found to be 4.02 kJ mol⁻¹ for H₃PO₄/BC membrane and 11.29 kJ mol⁻¹ for PA/BC membrane, respectively. In particular, the membrane electrode assembly fabricated with H₃PO₄/BC and PA/BC membranes reached the initial power densities of 17.9 mW cm⁻² and 23.0 mW cm⁻², which are much higher than those reported in literature in a real H₂/O₂ fuel cell at 25 °C.