Performance of g-C3N4 nanoparticles by EDTA modification and protonation for hydrogen release from sodium borohydride methanolysis

Here, for the first time, a metal-free catalyst was synthesized by ethylenediamine tetra-acetic acid (EDTA) modification of the carbon nitride (g-C₃N₄) sample and protonation of the obtained sample. The catalyst was used for the production of H₂ from the methanolysis of sodium borohydride (NaBH₄). The EDTA modification and protonation of the g-C₃N₄ sample was confirmed by XRD, FTIR, SEM-EDX, and TEM analyses. During the hydrogen generation, NaBH₄ concentration effect, catalyst amount effect, temperature effect and catalyst reusability were investigated. The HGR value obtained with 2.5% NaBH₄ using 10 mg catalyst was 7571 mL min^?1g^?1. The activation energy (Ea) for the g–C₃N₄–EDTA-H catalyst was found to be 32.2 kJ mol^?1 The reusability of the g–C₃N₄–EDTA-H catalyst shows a catalytic performance of 72% even after its fifth use.     

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.     

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.     

g-C3N4 particles with boron and oxygen dopants/carbon vacancies for efficient dehydrogenation in sodium borohydride methanolysis

In the study, metal-free boron and oxygen incorporated graphitic carbon nitride (B and O doped g-C₃N₄) with carbon vacancy was successfully prepared and applied as a catalyst to the dehydrogenation of sodium borohydride (NaBH₄) in methanol for the first time. The hydrogen generation rate (HGR) value was found to be 11,600 mL min^?1g^?1 by NaBH₄ of 2.5%. This is 2.53 times higher than the g-C₃N₄ catalyst without the addition of B and O. The obtained activation energy was 25.46 kJ mol^?1. X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM), energy dispersive X-Ray analyser (EDX), Transmission electron microscopy (TEM) and Fourier-transform infrared spectroscopy (FTIR) analyses for characterization were performed. A possible mechanism of H₂ production from the reaction using metal-free B and O doped g-C₃N₄ catalyst with carbon vacancy has been proposed. This study showed that g-C₃N₄ and its composites with doping atoms can be used effectively in H₂ production by NaBH₄ methanolysis.     

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.     

Metal-free hybrid composite particles with phosphorus and oxygen-doped graphitic carbon nitride dispersed on kaolin for catalytic activity toward efficient hydrogen release

Here, hybrid kaolin-g-C₃N₄ heterostructure particles were fabricated by calcination in the first step, followed by hydrothermal phosphoric acid activation in the second step, and phosphorus (P) and oxygen (O) doped kaolin-g-C₃N₄ metal-free catalyst was synthesized. This hybrid metal-free catalyst was used for the first time for the production of effective hydrogen (H₂) from sodium borohydride (NaBH₄) methanolysis. The hydrogen generation rate (HGR) value of 5500 ml min⁻¹g⁻¹ was obtained with the P and O doped kaolin-g-C₃N₄ catalyst. The activation energy (Ea) of 31.90 kJ mol⁻¹ by P and O doped kaolin-g-C₃N₄ for the production of H₂ was obtained. The kaolin-g-C₃N₄ and P and O doped kaolin-g-C₃N₄ metal-free catalysts were systematically characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR). Based on the results obtained, the mechanism of P and O-doped kaolin-g-C₃N₄ catalyst on H₂ production from NaBH₄ methanolysis was also proposed.     

Metal-free catalyst fabrication by incorporating oxygen groups on the surface of the carbonaceous sample and efficient hydrogen production from NaBH4 methanolysis

In the present study, metal-free catalysts for efficient H₂ generation from NaBH₄ methanolysis was produced for the first time from apricot kernel shells with two-step activation. The first stage of the two-stage activation includes the production of activated carbon with the KOH agent (AKOH), and the second stage includes hydrothermally HNO₃ activation with oxygen doping (O doped AKOH + N). The hydrogen production rate (HGR) and the activation energy (Ea) of the reaction with the obtained metal-free catalyst (10 mg) were determined as 14,444 ml min^?1 g^?1 and 7.86 kJ mol^?1, respectively. The structural and physical-chemical properties of these catalysts were characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy), elemental CHNS analysis, FT-IR (Fourier transform infrared spectroscopy), and nitrogen adsorption analysis. Also, the reusability results of this metal-free catalyst for H₂ production are promising.     

Synthesis of cobalt-doped catalyst for NaBH4 hydrolysis using eggshell biowaste

In the present study, a cobalt-doped catalyst was prepared from chicken eggshell powder (CEP) biowaste to be used in the hydrolysis of sodium borohydride (NaBH₄). In the presence of the prepared catalyst (CEP_cat), possible effects of the parameters of NaOH concentration (%), catalyst amount (g), NaBH₄ concentration (%), process temperature (^oC) and reusability affecting the hydrolysis of sodium borohydride were examined. The CEP_cat obtained was characterized with FT-IR, TGA, XRD, SEM and EDX analyses. The hydrogen generation rate (HGR) was determined as 432 mL g_Co⁻¹ min⁻¹ in the presence of 1 g CEP_cat, a CoO/CaO ratio of 10/90 and 1% NaBH₄ concentration. The activation energy of the NaBH₄ hydrolysis reaction was calculated as 16.78 kJ mol⁻¹. After 16 reuses of the CEP_cat there was no significant decrease in the hydrogen volume. Compared to the first use while there was an increase in the HGR. These results showed that the CEP_cat prepared has a significant advantage over other catalysts for use in NaBH₄ hydrolysis.     

Very efficient dehydrogenation of methanolysis reaction with nitrogen doped Chlorella Vulgaris microalgae carbon as metal-free catalysts

In this study, nitrogen (N) doped metal-free catalysts were obtained as a result of nitric acid (HNO₃) activation of carbon sample (C–KOH–N), which was obtained based on Chlorella Vulgaris microalgae by KOH activation (C–KOH). These catalysts have been effectively used to produce hydrogen (H₂) from the sodium borohydride (NaBH₄) methanolysis reaction. Compared to the C–KOH catalyst, the catalytic activity for C–KOH–N showed a seven-fold improvement. Hydrogen generation rate (HGR) values obtained for the NaBH₄ methanolysis reaction for C–KOH and C–KOH–N metal-free catalysts were 3250 and 20,100 mL min^?1 g^?1. The catalysts were characterized using various analytical techniques such as XPS, XRD, SEM, FTIR, BET, and elemental analysis. This work can provide a new alternative strategy to produce specific heteroatom-doped metal-free carbon catalysts for environmentally friendly conversion to produce H₂ efficiently.     

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.     

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.     

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.     

Optimisation of sepiolite clay with phosphoric acid treatment as support material for CoB catalyst and application to produce hydrogen from the NaBH4 hydrolysis

Herein, the CoB catalyst supported on the sepiolite clay treated with phosphoric acid was utilized to produce hydrogen from the NaBH₄ hydrolysis. In order to analyse the performance of the phosphoric acid treated sepiolite clay supported-CoB catalyst, the NaBH₄ concentration effect, phosphoric acid concentration effect, phosphoric acid impregnation time effect, CoB catalyst percentage effect, and temperature effect were studied. In addition, XRD, XPS, SEM, TEM, BET, and FTIR analysis were performed for characterization of Co–B catalyst supported on the acid-treated sepiolite. The completion time of this hydrolysis reaction with Co–B (20%) catalyst supported on the sepiolite treated by 5 M phosphoric acid was approximately 80 min, whereas the completion time of this hydrolysis reaction with acid-free sepiolite-supported Co–B (20%) catalyst was approximately 260 min. There is a five-fold increase in the maximum production rate. The maximum hydrogen production rates of this hydrolysis reaction at 30 and 60 °C were found as 1486 and 5025 ml min⁻¹g⁻¹_catalyst, respectively. Activation energy was found as 21.4 kJ/mol. This result indicates that the acid treatment on sepiolite is quite successful. The re-usability of NaBH₄ hydrolysis reaction by CoB catalyst supported on sepiolite treated phosphoric acid for successive five cycles of NaBH₄ at 30 °C was investigated.     

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.     

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.     

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.     

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.     

Production of metal-free catalyst from defatted spent coffee ground for hydrogen generation by sodium borohyride methanolysis

In the present study, defatted spent coffee ground (DSCG) treated with different acids was used as a metal-free catalyst for the first time. The aim of undertaken work is to demonstrate that DSCG can be used as a green catalyst to produce hydrogen through methanolysis of sodium borohydride. To produce hydrogen by the sodium borohydride methanolysis (NaBH₄), DSCG was pretreated with different acids (HNO₃, CH₃COOH, HCl). According to the superior acid performance, acetic acid was selected and then different concentrations of the chosen acid were evaluated (1M, 3M, 5M, and 7M). Subsewuently, different temperatures (200, 300, 400 and 500 °C) and burning times (30, 45, 60 and 90 min) for the optimization of DSCG-catalyst were tested. The experiments with the use of CH₃COOH treated DSCG-catalyst reveal that the optimal acid concentration was 1M CH₃COOH and the burning temperatures and time were 300 °C and 60 min, respectively. FTIR, SEM, ICP-MS and CHNS elemental analysis were carried out for a through characterization of the catalyst samples. In this study, the experiments were carried out with 10 ml methanol solution contained 0.025 g NaBH₄ with 0.1 g catalyst at 30 °C unless otherwise stated. The effect of NaBH₄ concentration was investigated with use of 1%, 2.5%, 5%, and 7.5% NaBH₄, while the influence of catalyst concentration was discovered with the use of 0.05, 0.1, 0.15, and 0.25 g catalyst. Different temperatures were chosen (30, 40, 50 and 60 °C) to explore the hydrogen production performance of the catalyst. In addition, the maximum hydrogen production rate through methanolysis reaction of NaBH₄ by this catalyst was found to be 3171.4 mL min⁻¹gcat⁻¹. Also, the activation energy was determined to be 25.23 kJ mol⁻¹.     

Stability and kinetic studies of MOF‐derived carbon‐confined ultrafine Co catalyst for sodium borohydride hydrolysis

A mesoporous carbon‐confined cobalt (Co@C) catalyst was fabricated by pyrolysis of macroscale Co‐metal–organic framework (MOF) crystals and used to catalyze NaBH₄ hydrolysis for hydrogen production. To reveal the structural changes of cobalt nanoparticles, we characterized the fresh and used Co@C catalysts using X‐ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and N₂ adsorption. This MOF‐derived Co@C exhibits high and stable activity toward NaBH₄ hydrolysis. No obvious agglomeration of Co nanoparticles occurred after five consecutive runs, implying good resistance of Co@C composite to metal aggregation. The kinetics of NaBH₄ hydrolysis was experimentally studied by changing initial NaBH₄ concentration, NaOH concentration, and catalyst dosage, respectively. It was found that the hydrogen generation rate follows a power law: r = A exp (?45.0/RT)[NaBH₄]^0.985[cat]^1.169[NaOH]^?0.451 .     

Sulphur and nitrogen-doped metal-free microalgal carbon catalysts for very active dehydrogenation of sodium borohydride in methanol

Micro algae based on Spirulina platensis is successfully used for the synthesis of S and N-doped metal-free carbon materials. The procedure consists of three stages; (i) Activated carbon production by KOH activation in CO₂ atmosphere (S-AC), (ii) S atom doping to the obtained S-AC using sulphuric acid by hydrothermal activation (S-AC-S), (iii) N atom doping by hydrothermal activation to S-AC obtained using nitric acid (S-AC-S-N). The S and N doped metal-free catalysts are used for H₂ release in NaBH₄ methanolysis reaction (NaBH₄-MR) for the first time. The metal-free carbon catalysts are characterized by X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM-EDS), X-ray diffractometer spectroscopy (XRD), Fourier-transform infrared spectroscopy (FTIR), nitrogen adsorption and elemental analysis (CHNS) methods. When the HGR values obtained for S-AC-S-N (26,000 mL min^?1 g^?1) and S-AC (2641 mL min^?1 g^?1) are compared, there is a 9.84-fold increase. Activation energy (Ea) value for S-AC-S-N was 10.59 kJ mol^?1.