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1.
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.  相似文献   

2.
Metal-free catalysts (C–KOH–P) containing phosphorus (P) and oxygen (O) prepared by the modification with phosphoric acid (H3PO4) of activated carbon (C–KOH) obtained by activation of Chlorella Vulgaris microalgae with potassium hydroxide (KOH) were investigated for the hydrogen (H2) generation reaction from methanolysis of sodium borohydride (NaBH4). Elemental analysis, XRD, FTIR, ICP-MS, and nitrogen adsorption were used to analyze the characteristics of metal-free catalysts. The results showed that groups containing O and P were attached to the carbon sample. In the study, the hydrogen production rates (HGR) obtained with metal-free C–KOH and C–KOH–P catalysts were 3250 and 10,263 mL/min/g, respectively. These HGR values are better than most values obtained for many catalysts presented in the literature. Besides, relatively low activation energy (Ea) of 27.9 kJ/mol was obtained for this metal-free catalyst. The C–KOH–P metal-free catalyst showed ideal reusability with 100% conversion and a partial reduction in the H2 production studies of NaBH4 methanolysis after five consecutive uses.  相似文献   

3.
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.  相似文献   

4.
Here, the oxygen(O) and nitrogen(N) doped metal-free carbon synthesis including potassium hydroxide (KOH) activation of Spirulina Platensis microalgae, followed by nitric acid (HNO3) activation is reported for the first time. Oxygen and nitrogen-doped metal-free catalysts were investigated for efficient hydrogen (H2) production from methanolysis of sodium borohydride (NaBH4). Compared to the catalyst obtained with the KOH activation, the catalytic activity for O and N doped metal-free showed about a four-fold improvement. The catalysts were analysed by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffractometer (XRD), nitrogen adsorption, elemental analysis and Fourier-transform infrared spectroscopy (FTIR). The effects of temperature, NaBH4 amounts, catalyst loading and reusability experiments on the catalytic performance of obtained metal-free catalysts by H2 release from NaBH4 methanolysis were performed. This study can provide a new alternative strategy to produce specific metal-free carbon catalysts doped heteroatom for environmentally friendly conversion to produce H2 efficiently.  相似文献   

5.
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.  相似文献   

6.
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.  相似文献   

7.
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.  相似文献   

8.
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.  相似文献   

9.
Here, the carbon nanodots were successfully synthesized from pomegranate peels (PPCD). This obtained PPCD was treated by a hydrothermal process with phosphoric acid for P doping (P doped PPCD) and used as a metal-free catalyst to obtain hydrogen(H2) from sodium borohydride (NaBH4) methanolysis for the first time. The characteristics of the samples obtained by ultraviolet, fluorescence, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM) and Inductively coupled plasma mass spectrometry (ICP-MS) analyses were examined. NaBH4 concentration effect, temperature effect and catalyst reusability experiments were carried out. Using 10 mg of the catalyst with 2.5% NaBH4, an HGR value of 13000 mL min?1g?1 was obtained. The activation energy (Ea) for the P-doped PPCD catalyst was 30.96 kJ mol?1.  相似文献   

10.
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.  相似文献   

11.
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.  相似文献   

12.
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.  相似文献   

13.
In this study, activated carbon is produced from defatted hazelnut bagasse at different activation conditions. The catalytic activities of activated carbons are evaluated for NaBH4 methanolysis and electrooxidation. These materials are characterized by N2 adsorption-desorption, FTIR, SEM-EDS and XPS and results show that these materials are prepared successfully. N2 adsorption-desorption results reveal that activated carbon (FH3-500) has the highest BET surface area as 548 m2/g, total pore volume as 0.367 cm3/g and micropore volume as 0.205 cm3/g. On the orher hand, as a result of hydrogen production studies, FH3-500 activated carbon catalyst has the highest initial hydrogen production rate compared to other materials. At 50 °C, this metal-free activated carbon catalyst has a high initial hydrogen production rate of 13591.20 mL/min.gcat, which is higher than literature values. Sodium borohydride electrooxidation measurements reveal that FH2-500 also has the highest electrocatalytic activity and stability. Hazelnut pulp-based activated carbons are firstly used as a metal-free catalyst in the methanolysis and electrooxidation of sodium borohydride, and its catalytic activity is good as a metal-free catalyst. The results show that the hazelnut pulp-based activated carbon catalyst is promising as a metal-free catalyst for the methanolysis and electrooxidation of sodium borohydride.  相似文献   

14.
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.  相似文献   

15.
The poly(2-aminoethyl methacrylate) (p(AEM)) microgels were synthesized by microemulsion polymerization technique and used for in situ metal nanoparticle preparation to render as p(AEM)-M (M: Co or Ni) microgel composites and were used in p(AEM) based poly ionic liquid (PIL) microgels. Next, these p(AEM)) based microgel materials were used as catalysts for hydrogen (H2) production from both hydrolysis and methanolysis reactions of sodium borohydride (NaBH4). It was found that the catalytic hydrolysis of the NaBH4 reaction, catalyzed by p(AEM)-Co microgel composite was completed in 140 min, whereas the methanolysis of NaBH4 methanolysis catalyzed by the PIL of p(AEM)+Cl microgels was completed in 5 min both with 250 ± 2 mL H2 production. Furthermore, p(AEM)-Co microgel composite catalysts maintained 80% catalytic activity after 5 consecutive uses in NaBH4 hydrolysis. On the other hand, p(AEM)+Cl microgels were found to afford more than 50% catalytic activity even after 20 repetitive use in NaBH4 methanolysis due to superior regeneration ability. Moreover, activation energy values for p(AEM)-Co microgel composites catalyzed NaBH4 hydrolysis reaction were calculated as 38.9 kJ/mol in comparison to 37.3 kJ/mol activation energy of p(AEM)+Cl microgel catalyzed methanolysis reaction.  相似文献   

16.
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.  相似文献   

17.
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.  相似文献   

18.
In this research study, orange peel-based biocatalysts developed from different acid protonation were used as a metal-free catalyst for hydrogen production from sodium borohydride (NaBH4). In order to prepare the orange peel-based biocatalyst with higher catalytic activity, experiments were conducted with pure orange peel, different acid molar concentrations, and calcination temperatures. The physical morphology, surface texture, and chemical interaction were thoroughly analyzed by XRD, FTIR Raman, FESEM, BET, and TGA. As a result of the experiment, it was determined that the highly acid-treated biocatalyst (40% H3PO4, 40% H2SO4, 40% HCl) and calcinated at 450 °C for 1 h had higher catalytic activity. As a result, bio-hydrogen production at 35 °C and 70 °C methanolysis with 3% NaBH4 catalyzed by a mixture of acid-treated catalysts were found as 46,213 and 63,842 ml min−1g.cat−1, respectively. However, with the increase of molar concentration of biocatalyst with 40% individual acid prolonged samples, the HGR rates will not have a satisfactory value in comparison with the 40% mixture of the acid-treated catalyst due to less number of active sites.  相似文献   

19.
Herein, the surface properties of graphitic carbon nitride (GCN) with sulphur(S), boron (B) and oxygen (O) dopants were improved. The heteroatom-doped metal-free GCN exhibited both rich surface functional groups and a carbon defect structure. These metal-free catalysts were used to obtain hydrogen (H2) from the sodium borohydride (SB) methanolysis for the first time. Compared to GCN, S, B, and O doped GCN catalyst obtained showed a 2.2-fold improvement in H2 production. HGR value obtained with B, O and S doped GCN (10 mg) via SB of 2.5% was 9166 ml min −1g−1. XPS, SEM-EDX, TEM, FTIR, and XRD analyses were used for the structural properties of catalysts. The activation energy (Ea) for B, O and S doped GCN was 28.89 kJ mol−1.  相似文献   

20.
Cellulose cotton fibers (CF) are coated with chitosan (CH) by simple, economic, and environmental friendly method. The CFs are kept in aqueous acetic acid solution to protonate the fibers before coated with CH solution (1.5% w/v in acetic acid aqueous solution (20% v/v)), represented as CF-A-CH. These materials are characterized by ATR-FTIR, XRD, FE-SEM and EDS which shows the successful coating of the CH on the CF surface. The prepared materials are exploited as an effective catalyst for the production of hydrogen (H2) from NaBH4 methanolysis reaction. In addition, other polymers (gelatin and agarose) and surfactants (brij-56, pluronic F-127 and urea) as well as CH in solution form are testified as catalyst for NaBH4 methanolysis reaction. High generation rate (8 times) and increase in amount of H2 (150 mL) is observe using only 50 μL CH solution. Furthermore, influences of various constraints, which affect the H2 production, like catalyst types, catalyst amount, NaBH4 amount, effect of temperature are also explored. A low activation energy (Ea), almost 14.41 ± 0.46 kJ mol−1 is calculated for NaBH4 methanolysis reaction in presence of CF-A-CH at temperature range 0 °C - 45 °C. Moreover, the catalyst reusability is also analyzed and no decline in percent conversion is found, whereas a little reduction in percent performance is detected after every cycle and only 18% lost is observed in its percent activity after completion of five successive cycles.  相似文献   

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