Poly(2-aminoethyl methacrylate) based microgels catalyst system to be used in hydrolysis and methanolysis of NaBH4 for H2 generation

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.     

Oxygen and nitrogen-doped metal-free microalgae carbon nanoparticles for efficient hydrogen production from sodium borohydride in methanol

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.     

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

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

Very fast H2 production from the methanolysis of NaBH4 by metal‐free poly(ethylene imine) microgel catalysts

The polyethyleneimine (PEI) microgels prepared via microemulsion polymerization are protonated by hydrochloric acid treatment (p‐PEI) and quaternized (q‐PEI) via modification reaction with methyl iodide and with bromo alkanes of different alkyl chain lengths such as 1‐bromoethane, 1‐bromobutane, 1‐bromohexane, and 1‐bromooctane. The bare p‐PEI and q‐PEI microgels are used as catalysts directly without any metal nanoparticles for the methanolysis reaction of sodium borohydride (NaBH₄). Various parameters such as the protonation/quaternization reaction on PEI microgels, the amount of catalyst, the amount of NaBH₄, and temperature are investigated for their effects on the hydrogen (H₂) production rate. The reaction of self‐methanolysis of NaBH₄ finishes in about 32.5 min, whereas the bare PEI microgel as catalyst finishes the methanolysis of NaBH₄ in 22 min. Surprisingly, it is found that when the protonated PEI microgels are used as catalyst, the same methanolysis of NaBH₄ is finished in 1.5 min. The highest H₂ generation rate value is observed for protonated PEI microgels (10 mg) with 8013 mL of H₂/(g of catalyst.min) for the methanolysis of NaBH₄. Moreover, activation parameters are also calculated with activation energy value of 23.7 kJ/mol, enthalpy 20.9 kJ/mol, and entropy ?158 J/K.mol. Copyright © 2016 John Wiley & Sons, Ltd.     

Enhanced H2 generation from NaBH4 hydrolysis and methanolysis by cellulose micro-fibrous cottons as metal templated catalyst

A simple, fast, economic and environmental friendly method has been developed for the preparation of high active metal nanoparticles (MNPs) in the cellulose microfibers of cotton (CFC). The CFCs are kept in aqueous solutions of metal salts to adsorb metal ions. The CFC templated with metal ions are then treated with aqueous solution of NaBH₄ for the reduction of metal ions into nano zero-valent metal nanoparticles (nZV-MNPs). The CFC loaded with nZV-MNPs are characterized by XRD, XPS, ATR-FTIR and FE-SEM, which indicates the successful synthesis of nZV-MNPs over the surface of CFC (M@CFC). The M@CFC are utilized as an efficient catalyst for the hydrogen generation from the methanolysis/hydrolysis of NaBH₄. The Cu@CFC showed better catalytic performance for the hydrolysis of NaBH₄, whereas Ag@CFC catalytic performance were much better than the other loaded MNPs for the methanolysis reaction of NaBH₄. Effects of different parameters, which affecting the H₂ generation, like type of MNPs, amount of the catalyst, amount of NaBH₄, temperature and addition of chitosan (CH) polymer are also investigated. A very low activation energy (Ea), approximately 20.11 ± 0.12 kJ mol^?1 for methanolysis reaction of NaBH₄ is calculated at temperature range 22–40 °C. Besides, a very high H₂ generation obtained in presence of 10, 50, or 100 μL CH solution (2 wt% CH in 20% v/v aqueous acetic acid) in addition to 50 mg of Ag@CFC catalyst at 22 °C and 1000 rpm. Moreover, the reusability of the catalyst is performed and found no decrease in percent conversion, whereas percent activity decreases 35% after four cycles.     

Catalytic activity of metal-free amine-modified dextran microgels in hydrogen release through methanolysis of NaBH4

Polymeric microgels were prepared from dextran (Dex) by crosslinking linear natural polymer dextran with divinyl sulfone (DVS) with a surfactant-free emulsion technique resulting in high gravimetric yield of 78.5 ± 5.3% with wide size distribution. Dex microgels were chemically modified, and then used as catalyst in the methanolysis of NaBH₄ to produce H₂. The chemical modification of Dex microgel was done on epichlorohydrin (ECH)-reacted Dex microgels with ethylenediamine (EDA), diethylenetriamine (DETA), and triethylenetetraamine (TETA) in dimethylformamide (DMF) at 90°C for 12 hours. The modified dextran-TETA microgels were protonated using treatment with hydrochloric acid (HCl) and m-Dex microgels-TETA-HCl was found to be a very efficient catalyst for methanolysis of NaBH₄ to produce H₂. The effects of reaction temperature and NaBH₄ concentration on H₂ generation rates were investigated and m-Dex microgels-TETA-HCl catalyst possessed excellent catalytic performances with 100% conversion and 80% activity at end of 10 consecutive uses and was highly re-generatable with simple HCl treatment. Interestingly, m-Dex microgels-TETA-HCl catalyst can catalyze NaBH₄ methanolysis reaction in a mild temperature range 0 to 35°C with E_a value of 30.72 kJ/mol and in subzero temperature range, −20 to 0°C with E_a value of 32.87 kJ/mol, which is comparable with many catalysts reported in the literature.     

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.     

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.     

A novel Enteromorpha based hydrogel for copper and nickel nanoparticle preparation and their use in hydrogen production as catalysts

A novel ploy(Enteromorpha-g-acrylic acid) p(EP-g-AA) hydrogel was synthesized and used as a template to prepare Cu and Ni nanoparticles. Then the hydrogel-metal nanoparticles (hydrogel-M (M: Cu, Ni)) were employed as catalyst in the generation of hydrogen from the hydrolysis of NaBH₄. X-ray photoelectron spectroscopy (XPS), Fourier Transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), energy-dispersive X-ray spectrometer (EDS) and X-ray diffraction (XRD) were employed to determine the structure of p(EP-g-AA)-M (M: Cu, Ni) composite hydrogels. The effects of several parameters such as the amount of catalyst, initial concentration of NaBH₄ and reaction temperature on the hydrolysis reaction were investigated. The kinetics of the hydrolysis reaction under different temperatures was also evaluated to determine the activation parameters. Experimental results showed that the catalytic efficiency of p(EP-g-AA)-Ni was much better than the catalytic efficiency of p(EP-g-AA)-Cu. And increasing the amount of catalyst and decreasing the NaBH₄ concentration help to improve the reaction rate. Activation energy for the hydrolysis reaction was 42.61 kJ mol^?1 catalyzed by p(EP-g-AA)-Cu and 39.10 kJ mol^?1 by p(EP-g-AA)-Ni, respectively. At the end of five repetitive uses, p(EP-g-AA)-Cu composites possessed 64% activity and p(EP-g-AA)-Ni owned 70% activity. And after being stored for 30 days, p(EP-g-AA)-Cu and p(EP-g-AA)-Ni both remained 85% activity.     

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.     

Chitosan coated cellulose cotton fibers as catalyst for the H2 production from NaBH4 methanolysis

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.     

Insight into the role of solvents in enhancing hydrogen production: Ru-Co nanoparticles catalyzed sodium borohydride dehydrogenation

Ru-Co nanoparticles prepared in nano-size by combustion derived of citric acid used sol-gel technique followed by calcination process at 450 °C. The external and internal properties of nano-sized catalyst were characterized by XRD, XPS, SEM, TEM, ICP-OES, and N₂ sorption techniques. The characterization results proved that nano-sized catalyst was mixture of cubic Co₃O₄ (18 nm) and tetragonal RuO₂ (40 nm) crystals with mesoporous structure (12.64 m²g^-1). Insight into the role of solvents for enhancing hydrogen production from Ru-Co nanoparticles catalyzed sodium borohydride (NaBH₄, SBH) was systematically studied by altering the dehydrogenation medium with water or methanol. The reaction kinetic performance of nano-sized catalyst was evaluated by performing both hydrogen generation reactions at various reaction temperatures, initial SBH concentration, and catalyst dosage to evaluate the hydrogen generation activity. Ru-Co nanoparticles exhibited exclusive catalytic performance for hydrogen generation by hydrolysis and methanolysis of SBH. The apparent activation energies (E_a) for the catalytic hydrolysis and methanolysis of SBH over Ru-Co nanoparticles were determined to be 20.02 kJ mol⁻¹ and 54.38 kJ mol⁻¹, respectively. Furthermore, Ru-Co nanoparticles also performed satisfied stability for both hydrolysis and methanolysis reactions. Beside both hydrogen generation was achived with fully conversion of SBH, Ru-Co nanoparticles promised good recyclability for at least 5 cycle for methanolysis of SBH.     

Hydrogen generation by hydrolysis of sodium borohydride on CoB/SiO2 catalyst

Generation of hydrogen by hydrolysis of alkali metal hydrides has attracted attention. Unsupported CoB catalyst demonstrated high activity for the catalytic hydrolysis of NaBH₄ solution. However, unsupported CoB nanoparticles were easy to aggregate and difficult to reuse. To overcome these drawbacks, CoB/SiO₂ was prepared and tested for this reaction. Cobalt (II) acetate precursor was loaded onto the SiO₂ support by incipient-wetness impregnation method. After drying at 100 °C, Co cations were deposited on the support. The dried sample was then dispersed in methanol/water solution and then fully reduced by NaBH₄ at room temperature. The catalyst was characterized by N₂ sorption, XRD and XPS. The results indicated that the CoB on SiO₂ possessed amorphous structure. B and Co existed both in elemental and oxidized states. SiO₂ not only affected the surface compositions of CoB, but also affected the electronic states of Co and B. B⁰ could donate partial electron to Co⁰. The structure effect caused by the SiO₂ support helped to prevent CoB nanocluster from aggregation and therefore the activity increased significantly on hydrolysis of alkaline NaBH₄ solution. The CoB/SiO₂ catalyst showed much higher activity than the unsupported CoB catalyst. At 298 K, the hydrogen generation rate on CoB/SiO₂ catalyst was 4 times more than that on the unsupported CoB catalyst. The hydrogen generation rate was as high as 10,586 mL min⁻¹ g⁻¹ catalyst at 298 K. CoB/SiO₂ is a very promising catalyst for this reaction.     

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.     

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.     

Metal nanoparticles supported on polyacrylamide water beads as catalyst for efficient generation of H2 from NaBH4 methanolysis

Water beads made from polyacrylamide polymer p-(AAm) were decorated with high efficient metal nanoparticles by inexpensive, fast, simple, and environmental friendly method. These water beads balls were kept in the metal salt solutions for 4 h; to adsorb the metals ions from these aqueous solutions. The metal ions decorated on the p-(AAm) water beads were converted to metal nanoparticles by its reduction with aqueous solution of NaBH₄. The prepared materials p-(AAm) loaded with MNPs (M@p-(AAm)) were characterized by ATR-FTIR, XRD, XPS, FESEM, and EDS which show the successful preparation of MNPs over the surface and within p-(AAm). Afterwards the M@p-(AAm) were investigated as a catalyst for the generation of hydrogen from the methanolysis of NaBH₄. The Ag@p-(AAm) show good catalytic activity for NaBH₄ methanolysis reaction as compared to the other loaded MNPs. In addition, different parameters which effecting H₂ generation were also investigated such as; MNPs types, catalyst amount and temperature of the reaction. Low activation energy (Ea) of 21.37 ± 0.67 kJ mol⁻¹, was calculated for NaBH₄ methanolysis reaction at temperature ranging from 5.0 °C to 35 °C. Moreover, the catalyst reusability was also studied and found no decrease in percent conversion, however percent efficiency was decreases about 37% after completion of four cycles.     

Synthesis of novel biocatalyst from organic waste protonated with acid treatment for hydrogen production

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.     

Highly efficient Co-B catalysts with Chlorella Vulgaris microalgal strain modified using hydrochloric acid as a new support material for hydrogen production from methanolysis of sodium borohydride

In this study, we report for the first time the use of C. Vulgaris microalgal strain containing cellulose in the modified form to be used as a catalyst support material for the production of hydrogen from the methanolysis reaction of sodium borohydride (NaBH₄). Acetic acid, phosphoric acid, and hydrochloric acid (HCl) at different concentrations and impregnation times were used for the protonation of cellulose in the microalgal strain. The cobalt ions were added to this modified support material and, C.Vulgaris microalgal strain-supported Co-B catalyst was obtained. XRD, BET, FTIR, XPS, ICP-MS, TEM, and SEM-EDX analysis were carried out for characterization of the sample. The maximum hydrogen production rate from the methanolysis reaction of NaBH₄ with this catalyst was 13215 ml min⁻¹ g_cat⁻¹. In addition, the activation energy was determined as 25.22 kJ/mol. At the same time, re-usability studies of the microalgal strain-supported Co-B catalyst were performed and it was found that there was no decrease in the % conversion for this catalyst, while the activity decreased. XRD, BET, FTIR, XPS, ICP-MS, TEM, and SEM-EDX.     

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.     

Can fool's gold “pyrite” become real gold as a catalyst for clean-energy H2 production?

The natural, most abundant sulfide mineral of pyrite was modified using polyethyleneimine (PEI) for use as a catalyst in H₂ release reactions from NaBH₄ in methanol. The catalytic performances of pyrite, pyrite-PEI, and protonated pyrite-PEI (pyrite-PEI+) were compared and the hydrogen generation rate (HGR) values of 795 ± 26, 2883 ± 190, and 4320 ± 188 mL H₂/(g of catalyst x min)⁻¹ were measured for H₂ production from NaBH₄ methanolysis. The effect of methanol:water mixture at various ratios, the amount of catalyst, the concentration of NaBH₄, and temperature on H₂ production from NaBH₄ in methanol catalyzed by pyrite-PEI⁺ were investigated. The activation energies for pyrite-PEI, and pyrite-PEI⁺ catalyzed H₂ release reactions were calculated as 47.2 and 36.8 kJ/mol, respectively. It was found that the activity % for the pyrite-PEI⁺ catalyst decreased to 76.2 ± 2.7% after five consecutive uses with 100% conversion for each re-use study. Furthermore, the re-generation of pyrite-PEI⁺ catalyst after the 5th usage was readily ensured by HCl treatment to completely recover and further increase the activity% of the catalyst. Therefore, pyrite was shown to be a useful re-generable and economic green catalyst for H₂ production in many potential applications.