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    • 专利摘要:
    The present invention pertains to the field of electrocatalysts, more specifically to electrocatalysts derived from metal-organic frames. In particular, the present invention relates to an iron zeolitic imidazolate framework, to the process for obtaining it and to a nanocomposite of graphitic carbon and iron nanoparticles, as well as to the process for obtaining said nanocomposite from the zeolitic iron imidazolate framework. In addition, the present invention relates to the use of the nanocomposite as a catalyst. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2703849A1
    申请号:ES201731106
    申请日:2017-09-12
    公开日:2019-03-12
    发明作者:Espallargas Guillermo Minguez；Cabrelles Javier Lopez；Pascual Jorge Romero；Miralles Eugenio Coronado
    申请人:Universitat de Valencia；
    IPC主号:
    专利说明:

    [0001]
    [0002] Iron zeolitic imidazolate framework, process for obtaining it and nanocomposite derived from it
    [0003]
    [0004] Field of the invention
    [0005] The present invention pertains to the field of electrocatalysts, more specifically to electrocatalysts derived from metal-organic frames. In particular, the present invention relates to an iron zeolitic imidazolate framework, to the process for obtaining it and to a nanocomposite of graphitic carbon and iron nanoparticles, as well as to the process for obtaining said nanocomposite from the zeolitic iron imidazolate framework, In addition, the present invention relates to the use of the nanocomposite as a catalyst.
    [0006]
    [0007] Background
    [0008] Oxygen electrochemistry involves oxygen reduction (ORR) and evolution (OER) reactions, which are the two most important reactions for electrochemical storage and energy conversion technologies, including fuel cells, metal batteries and electrolysis of the water. Electrochemical applications require highly active and stable electrocatalysts for ORR and OER. Noble metals are usually good electrocatalysts for these applications. For example, platinum-based nanocomposites are the most effective commercial electrocatalysts for ORR, whereas precious nanocomposites based on ruthenium and iridium are commonly used in the OER process. However, the low stability, scarcity and high cost of these oxygen-based electrocatalysts of noble metals prevent their implementation on a large scale. Therefore, it is urgent to develop highly effective and long-lasting alternatives with low cost, ideally with the bifunctional capacity for ORR and OER.
    [0009] In the last decade, it has been found that a wide range of alternative materials, including nanocarbons, metal oxides, carbides / nitrides and composites thereof, are electroactive for electrochemical oxygen processes. Among them, nanocarbons have shown a promising catalytic activity and also stability. In addition, the catalytic properties could be improved by the introduction of heteroatoms, including nitrogen, sulfur, boron, etc. In particular, it have described several nitrogen-doped nanocarbons grafted with nitrogen, including carbon nanotubes (CNT), graphene, mesoporous carbons and their nanocomposites, as possible alternatives to platinum catalysts. It is believed that the improved performance is related to the modified electronic structure and the carbon defects induced by the heteroatoms. However, in a few cases up to now an excellent activity and durability comparable to that of platinum / carbon catalysts has been found.
    [0010]
    [0011] Recently, metal-organic frames have emerged as a new platform for the synthesis of new nanocarbon compounds. As a subclass of metal-organic frameworks, zeolitic imidazolate frameworks, known as ZIFs, are excellent precursors for nanocarbon electrocatalysts in view of the abundance of carbon and nitrogen species, however, the nanocomposites derivatives of metal-organic frames are mostly microporous and poor graphitic grade, which are considered unfavorable for the transport of ions and electrons.Although a number of nanocarbons derived from metal-organic frames have been investigated as electrocatalysts, most of them exhibit an unsatisfactory electrochemical activity.
    [0012]
    [0013] ZIFs are a type of metal-organic framework that topologically has the same morphology as zeolites. Zeolites are porous aluminosilicate minerals that are found in nature but are also produced industrially on a large scale due to their commercial interest as adsorbents and catalysts.
    [0014]
    [0015] ZIFs are composed of transition metal ions coordinated tetrahedrally and connected by imidazolate ligands. It is said that ZIFs have zeolite type topologies since the metal-imidazole-metal angle is similar to the Si-O-Si angle of 145 ° in zeolites. ZIFs are usually prepared by solvothermal or hydrothermal techniques, where the crystals grow slowly by heating a solution of a hydrated metal salt, an imidazolate, a solvent and a base.
    [0016]
    [0017] US8314245 B2 describes various zinc ZIFs obtained by heating a solution of zinc nitrate tetrahydrate and imidazole or an imidazole derivative in a solvent at temperatures between 85 and 150 ° C for between 48 and 96 hours.
    [0018]
    [0019] Bao Yu Xia et al. describe the so-called cobalt ZIF-67, obtained from a solution of cobalt nitrate hexahydrate and 2-methylimidazole in a 1: 1 mixture of methanol: ethanol (Nature Energy, 2016, 1, 15006). Bao Yu Xia et al. they also describe the use of this ZIF-67 as a precursor to an electrocatalyst based on structures of carbon nanotubes doped with nitrogen.
    [0020]
    [0021] There is still a need to find new, more efficient electrocatalysts that can be equated with costly platinum catalysts.
    [0022]
    [0023] Description of the invention
    [0024] The present invention provides a new carbon and iron nanocomposite with excellent electrocatalytic behavior. The inventors of the present invention have obtained an electrocatalyst from a zeolitic iron framework not described to date. The inventors have also found an advantageous process to obtain said zeolitic framework of iron, precursor of the nanocomposite with excellent electrocatalytic activity. This advantageous process is cleaner and more careful with the environment, since it does not use solvents and therefore does not generate waste.
    [0025]
    [0026] In addition, the process for obtaining the nanocomposite of the present invention from the zeolitic framework of the present invention is quick and economical, since it is carried out at lower temperatures and in shorter times than other processes of the prior art.
    [0027]
    [0028] Therefore, in a first aspect, the present invention relates to a zeolitic framework comprising the general structure A-B-A where A is iron and B is a compound of formula I
    [0029]
    [0030]
    [0031]
    [0032]
    [0033] where R1, R2 and R3 are independently hydrogen, C1-4 alkyl, halo, cyano or nitro, where when R2 and R3 are C1.4 alkyl, R2 and R3 can be attached to form a cycle of 3 to 7 carbons.
    [0034]
    [0035] In a preferred embodiment, the zeolitic frame of the first aspect is isolated. Preferably, the zeolitic framework of the first aspect of the present invention has a purity of at least 80%, preferably at least 85%, more preferably at least 90% and even more preferably at least 95%. Preferably, the zeolitic framework of the first aspect is isolated and has a purity of at least 99%. Preferably, the zeolitic framework of the first aspect is isolated and has a purity of 100%.
    [0036]
    [0037] In a preferred embodiment of the first aspect of the present invention, the compound of formula I is imidazolate or 2-methylimidazolate. More preferably, the compound of formula I is 2-methylimidazolate.
    [0038]
    [0039] In a preferred embodiment, the zeolitic framework of the first aspect has zeolitic SOD topology. In a preferred embodiment, the zeolitic framework of the first aspect has the crystallographic structure of ZIF-8.
    [0040]
    [0041] In a preferred embodiment of the first aspect, the zeolitic framework is isolated, has a purity of at least 95%, comprises the general ABA structure where A is iron and B is 2-methylimidazole, has zeolitic SOD topology and the crystallographic structure of ZIF- 8
    [0042] A second aspect of the present invention relates to a process for obtaining the zeolitic frame of the first aspect, which comprises the following steps:
    [0043]
    [0044] to. mixing ferrocene and a compound of formula I as described in the first aspect, preferably 2-methylimidazole, in the presence of a template ligand,
    [0045] b. heating the sealed mixture of step (a) to a temperature of between 80 and 250 ° C for a time of at least 12 hours, preferably for at least 24 hours.
    [0046]
    [0047] As used herein, the term "template ligand" refers to a compound that is not incorporated into the structure of the zeolitic framework and that influences the reaction kinetics between ferrocene and the compound of formula I, which is preferably -methylimidazole In a preferred embodiment of the method of the second aspect, the template ligand is solid at room temperature (25 ° C.) Preferably, the template ligand is an aromatic heterocycle. More preferably, the template ligand is a heterocycle. aromatic where the heteroatom is nitrogen. Even more preferably, the template ligand is a pyridine or a pyridine derivative. More preferably, the template ligand is a bipyridine or a bipyridine derivative. In a preferred embodiment of the method of the second aspect, the template ligand is 4,4-bipyridine.
    [0048]
    [0049] In another preferred embodiment of the process of the second aspect, before heating the mixture of step (a), said mixture is sealed in a container under vacuum. Preferably, the vacuum is at least 10 "2 mbar, preferably at least 10" 3 mbar. preferably, the mixture of step (a) is prepared in the absence of solvent.
    [0050]
    [0051] In a preferred embodiment of the process of the second aspect, the molar ratio 4,4-bipyridine: 2-methylimidazole in the mixture of step (a) is at least 1.
    [0052]
    [0053] In another preferred embodiment of the process of the second aspect, step (b) is carried out at a temperature of between 110 and 200 ° C, preferably step (b) is carried out at a temperature of between 140 and 160 ° C. .
    [0054]
    [0055] In another preferred embodiment of the process of the second aspect, step (b) has a duration of between 2 and 6 days, preferably, stage (b) lasts between 3.5 and 4.5 days.
    [0056]
    [0057] In a preferred embodiment, the process of the second aspect of the present invention comprises the following steps:
    [0058]
    [0059] (a) mix ferrocene with 2-methylimidazole in the presence of 4,4-bipyridine, where the molar ratio 4,4-bipyridine: 2-methylimidazole is at least 1,
    [0060] (b) sealing the mixture of step (a) under a vacuum of at least 10 "2 mbar, and
    [0061] (c) heating the sealed mixture of step (b) to 110 and 200 ° C for between 2 and 6 days.
    [0062]
    [0063] In a third aspect, the present invention relates to a nanocomposite comprising:
    [0064]
    [0065] (i) a graphitic carbon matrix and
    [0066] (ii) between 0.1 and 3% by weight, preferably between 0.3 and 2% by weight, more preferably between 0.7 and 0.9% by weight of iron nanoparticles with respect to the total weight of the nanocomposite,
    [0067] wherein said iron nanoparticles have a diameter of between 1 and 60 nm, preferably between 5 and 45 nm, more preferably between 10 and 30 nm,
    [0068] where said nanocomposite comprises:
    [0069]
    [0070] between 70 and 95% by weight, preferably 80 and 94% by weight, more preferably between 90 and 92% by weight of carbon
    [0071]
    [0072] between 3 and 20% by weight, preferably between 5 and 15% by weight, more preferably between 7 and 9% by weight of oxygen, and
    [0073]
    [0074] between 0.2 and 5% by weight, preferably between 0.5 and 3% by weight, more preferably between 0.8 and 1.2% by weight of nitrogen,
    [0075]
    [0076] with respect to the total weight of the nanocomposite, and
    [0077]
    [0078] wherein said nanocomposite has a current density in the oxygen evolution reaction (OER) greater than 200 mA / cm2 in 1M KOH, preferably higher than 230 mA / cm2 in 1M KOH, more preferably higher than 300 mA / cm2 in 1M KOH .
    [0079]
    [0080] Preferably, the nanocomposite of the third aspect has a current density in the hydrogen evolution reaction (HER) of less than -300 mA / cm2 in 1M KOH, preferably less than -430 mA / cm2 in 1M KOH, more preferably less than - 500 mA / cm2 in 1M KOH.
    [0081]
    [0082] The current density of the nanocomposite of the present invention was analyzed in the HER reaction at -0.75 V vs. RHE and in the OER reaction at 1.8 V vs. RHE.
    [0083]
    [0084] The current density of a nanocomposite can be calculated in the HER reaction or in the OER reaction, and in different media, so that the current density for the same nanocomposite for the same reaction is not the same according to the medium in which it is used. calculate When the current density in the OER reaction is calculated in 0.1 M KOH, the nanocomposite of the third aspect of the present invention has a current density higher than 50 mA / cm2, preferably higher than 100 mA / cm2, more preferably higher at 180 mA / cm2. When the current density in the HER reaction is calculated in 0.1 M KOH, the nanocomposite of the third aspect of the present invention has a current density of less than -100 mA / cm2, preferably has a current density of less than -140. mA / cm2, more preferably has a current density of less than -200 mA / cm2. When the current density in the HER reaction is calculated in 1 M H2SO4, the nanocomposite of the third aspect of the present invention has a current density lower than -100 mA / cm2, preferably has a current density lower than -200 mA / cm2, more preferably has a density of current lower than -250 mA / cm2. When the current density in the HER reaction is calculated in H2SO40.5 M, the nanocomposite of the third aspect of the present invention has a current density of less than -100 mA / cm2, preferably has a current density of less than -140 mA / cm2, more preferably has a current density lower than -200 mA / cm2. When the current density in the HER reaction is calculated in a buffer at pH 7, the nanocomposite of the third aspect of the present invention has a current density of less than -20 mA / cm2, preferably has a current density of less than -25. mA / cm2, more preferably has a current density of less than -40 mA / cm2.
    [0085] In a preferred embodiment, the nanocomposite of the third aspect of the present invention has a start of hydrogen evolution reaction (HER) of more than -0.5 V (vs. RHE in 1M KOH) or more than -0.42 V ( vs RHE in 0.1 M KOH) or more than -0.62 V (vs. RHE in H2SO41 M) or more than -0.75 V (vs. RHE in H2SO40.5 M) or more than -0.85 V ( vs RHE in buffer solution pH 7). In a more preferred embodiment, the nanocomposite of the third aspect of the present invention has a hydrogen evolution reaction (HER) start of more than -0.45 V (vs. RHE in 1M KOH) or more than -0.35 V (vs RHE in 0.1 M KOH) or more than -0.57 V (vs. RHE in H2SO41 M) or more than -0.70 V (vs. RHE in H2SO40.5 M) or more than -0.80 V (vs RHE in buffer solution pH 7). In an even more preferred embodiment, the nanocomposite of the third aspect of the present invention has a hydrogen evolution reaction (HER) start of more than -0.40 V (vs. RHE in 1M KOH) or more than -0.32. V (vs. RHE in 0.1 M KOH) or more than -0.53 V (vs. RHE in H2SO41 M) or more than -0.67 V (vs. RHE in H2SO40.5 M) or more than -0.78 V (vs RHE in buffer solution pH 7).
    [0086]
    [0087] In a preferred embodiment, the nanocomposite of the third aspect of the present invention has an oxygen evolution reaction (OER) start of less than 1.75 V (vs. RHE in 1 M KOH or 0.1 M KOH). Preferably, the nanocomposite of the third aspect of the present invention has an oxygen evolution reaction (OER) start of less than 1.70 V (vs. RHE in 1 M KOH or 0.1 M KOH). More preferably, the nanocomposite of the third aspect of the present invention has an oxygen evolution reaction (OER) start of less than 1.65 V (vs. RHE in 1 M KOH or 0.1 M KOH).
    [0088] In a preferred embodiment, the nanocomposite of the third aspect of the present invention has a Tafel slope of less than 57 mV per decade (in 1M KOH) or less than 68 mV per decade (in 0.1M KOH). Preferably, the nanocomposite of the third aspect of the present invention has a Tafel slope of less than 47 mV per decade (in 1M KOH) or less than 58 mV per decade (in 0.1M KOH). More preferably, the nanocomposite of the third aspect of the present invention has a Tafel slope of less than 40 mV per decade (in 1M KOH) or less than 50 mV per decade (in 0.1 M KOH).
    [0089]
    [0090] In a preferred embodiment, the nanocomposite of the third aspect of the present invention has a pore size of 0.5 to 15 nm, preferably 1 to 10 nm, more preferably 3 to 5 nm, calculated by adsorption tests.
    [0091]
    [0092] In a preferred embodiment, the nanocomposite of the third aspect of the present invention has a pore volume of 0.1 to 2 cm3 g-1, preferably 0.5 to 1.5 cm3 g-1, more preferably 0.9 at 1.1 cm3 g-1, calculated by adsorption tests.
    [0093] In a preferred embodiment, the nanocomposite of the third aspect of the present invention has a micropore volume of 0.01 to 1 cm3 g-1, preferably 0.05 to 0.5 cm3 g-1, more preferably 0.09 to 0.11 cm3 g-1, calculated by adsorption tests.
    [0094]
    [0095] In a preferred embodiment, the nanocomposite of the third aspect of the present invention has a BET area greater than 100 m2 / g, preferably greater than 200 m2 / g, more preferably greater than 400 m2 / g, calculated by adsorption tests. In another preferred embodiment, the nanocomposite of the third aspect of the present invention has a BET area of 100 to 1200 m2 / g, preferably 200 to 800 m2 / g, more preferably 400 to 600 m2 / g, calculated by adsorption tests .
    [0096]
    [0097] In a preferred embodiment, the nanocomposite the third aspect comprises a graphitic carbon matrix and between 0.3 and 2% by weight of iron nanoparticles with respect to the total weight of the nanocomposite, where said iron nanoparticles have a diameter of between 5 and 45 nm, wherein said nanocomposite comprises between 80 and 94% by weight of carbon, between 5 and 15% by weight of oxygen, and between 0.5 and 3% by weight of nitrogen, with respect to the total weight of the nanocomposite, where said nanocomposite has a current density in the hydrogen evolution reaction (HER) of less than -430 mA / cm2 in 1M KOH and a current density in the OER reaction greater than 230 mA / cm2 in 1M KOH, and wherein said nanocomposite has a BET area greater than 200 m2 / g and a micropore volume of 0.05 to 0.5 cm3 g-1.
    [0098]
    [0099] In a fourth aspect, the present invention relates to a process for obtaining a nanocomposite according to the third aspect, which comprises the following steps:
    [0100]
    [0101] to. obtaining from a zeolitic framework comprising the general structure A-B-A where A is iron and B is a compound of formula I according to the first aspect, by a process according to the second aspect, and
    [0102]
    [0103] b. calcining the zeolitic framework obtained in step (a) at a temperature of between 500 and 900 ° C, preferably between 600 and 800 ° C, more preferably between 680 and 720 ° C for a time of at least 1 hour, preferably during less 2 hours, more preferably for at least 3 hours.
    [0104]
    [0105] In a preferred embodiment of the process of the fourth aspect, in stage (b) the zeolitic framework obtained in step (a) is calcined at a temperature of between 500 and 900 ° C for a time of between 2 and 5 hours, preferably during between 3 and 4 hours.
    [0106]
    [0107] In a preferred embodiment of the process of the fourth aspect, before stage (b) the zeolitic framework of step (a) is introduced into a solvent and an inert atmosphere is created, preferably with nitrogen. Preferably, the solvent is acetonitrile.
    [0108]
    [0109] In a fifth aspect, the present invention relates to the nanocomposite obtained by the process according to the fourth aspect of the invention.
    [0110]
    [0111] In a sixth aspect, the present invention relates to the use of the nanocomposite according to the third or fifth aspect, as a catalyst. Preferably, the nanocomposite of the present invention is used as a catalyst in fuel cells of proton exchange membranes or PEMFC, from the English "proton exchange membrane fuel cells".
    [0112] Description of the figures
    [0113] Figure 1. A and B. Photographs made by scanning electron microscope of the crystals of the iron imidazolate zeolitic framework of the present invention. C. Photograph by optical microscope of the crystals of the iron imidazolate zeolitic framework of the present invention. The scale bar is 300 microns in A and 500 microns in B.
    [0114] Figure 2. A. Tetrahedral coordination environment of the iron (II) atoms in the structure of the iron imidazolate zeolitic framework of the present invention. B. Representation of a pore and channel belonging to the structure of the iron imidazolate zeolitic framework of the present invention where the iron atoms have been represented in the form of tetrahedra, the carbons and nitrogens are represented in the form of dots and the sphere represents the empty cavity or pore of the material. C. Representation of the SOD type structure of zeolites. D. X-ray diffractogram of the iron imidazolate zeolitic framework of the present invention (peak line) and difference [(Iobs-Icald)] (bottom line) of the Pawley refinement (range of 20: 4.0-40.0 °).
    [0115]
    [0116] Figure 3. A. Graphic representation of the product of magnetic susceptibility by temperature versus temperature. B. Graphical representation of the magnetization in front of the field at 2K. The dotted line shows the Brillouin function for a S = 2 system without magnetic interactions.
    [0117]
    [0118] Figure 4. X-ray diffractogram of the nanocomposite of the present invention.
    [0119]
    [0120] Figure 5. Photographs made by high resolution transmission electron microscope of the nanocomposite of the present invention. The scale bar has a length of 20 nm, 2 nm, 10 nm and 10 nm in photographs A to D, respectively.
    [0121]
    [0122] Figure 6. Photographs of the nanocomposite of the present invention made by scanning electron microscope.
    [0123]
    [0124] Figure 7. X-ray spectroscopy (XPS) signal of the iron in the nanocomposite of the present invention.
    [0125]
    [0126] Figure 8. XPS signal of the nitrogen in the nanocomposite of the present invention.
    [0127] Figure 9. XPS signal of the carbon in the nanocomposite of the present invention.
    [0128]
    [0129] Figure 10. N2 isotherm of the nanocomposite of the present invention.
    [0130]
    [0131] Figure 11. CO2 isotherm of the nanocomposite of the present invention.
    [0132]
    [0133] Figure 12. Pore distribution of the nanocomposite of the present invention.
    [0134]
    [0135] Figure 13. Oxygen evolution reaction (OER) of the nanocomposite of the present invention (black) and of the nickel foam (gray) in 0.1 M KOH.
    [0136] Figure 14. OER of the nanocomposite of the present invention (black) and of the nickel foam (gray) in 1M KOH.
    [0137]
    [0138] Figure 15. Hydrogen evolution reaction (HER) of the nanocomposite of the present invention (black) and of the nickel foam (gray) in 0.1 M KOH.
    [0139]
    [0140] Figure 16. HER of the nanocomposite of the present invention (black) and of the nickel foam (gray) in 1M KOH.
    [0141]
    [0142] Figure 17. HER of the nanocomposite of the present invention (black) and of the carbon felt (gray) in H2SO40.5 M.
    [0143]
    [0144] Figure 18. HER of the nanocomposite of the present invention (black) and of the carbon felt (gray) in H2SO41 M.
    [0145]
    [0146] Figure 19. Tafel earrings of the nanocomposite of the present invention in the two basic media.
    [0147]
    [0148] Figure 20. Galvanostatic stability of the nanocomposite of the present invention in 0.1 M KOH.
    [0149]
    [0150] Figure 21. Galvanostatic stability of the nanocomposite of the present invention in 1 M KOH.
    [0151]
    [0152] Figure 22. Potentiostatic stability of the nanocomposite of the present invention in 1M KOH.
    [0153]
    [0154] Examples
    [0155] The following examples illustrate the present invention and demonstrate the advantageous properties of the nanocomposites of the present invention, as well as of the method of the present invention.
    [0156]
    [0157] Example 1: Synthesis of iron ZIF:
    [0158]
    [0159] Ferrocene (30 mg, 0.16 mmol), 4,4-bipyridine (50 mg, 0.32 mmol) and 2-methylimidazole (20 mg, 0.24 mmol) are used for the synthesis of iron ZIF. These three solids are mixed and sealed under vacuum in a tube. The mixture is heated at 150 ° C for 4 days to obtain yellow crystals suitable for X-ray diffraction in single crystal (Figure 1). The product obtained is allowed to cool, and the tube is opened. The crystals are cleaned by removing reactants that have not reacted with acetonitrile and benzene. The purity of the final solid is determined by X-ray powder diffraction. All reagents are commercially available and have been used without further purification.
    [0160]
    [0161] Example 2: Analysis of iron ZIF by powder X-ray diffraction.
    [0162]
    [0163] The crystallographic studies at 120 K reveal that the yellow crystals are isostructural with ZIF-8 (a = 17.1794 Á), with the spatial group I-43m. The metal centers, Fe (II), are in a tetrahedral coordination environment, connected by NCN bridges created by the 2-methylimidazole ligands, as can be seen in Figure 2. The Fe-N distances are 2,032 Á and the Fe distances. -Fe are 6,069 Á. The Pawley refinement of the X-ray powder diffractogram (PXRD) obtained shows a single crystalline phase, since a Rwp factor of 0.01462 is obtained, this Rwp indicates that the error The profile of the diffractogram is very low (1.46%), which implies that there is only one phase: the iron ZIF, and a GOF (of the English "goodness of fit") close to 1: of 1,103. In figure 2D the intensity and width of the peaks can be seen, which denotes a high crystallinity. With the scanning electron microscope (SEM) the morphology of the crystals was studied, obtaining crystals with very well defined faces, and with a size around 300 microns (figure 1).
    [0164]
    [0165] The N-C-N bridges between the iron centers allow the magnetic exchange, and the tetrahedral environment of the Fe (II) that grants an S = 2 for each metallic center allows the appearance of magnetic ordering. As we can see in figure 3, where the product of magnetic susceptibility (xm) is represented with temperature (T) versus temperature, xmT decreases as it cools, indicating the presence of antiferromagnetic interactions between Fe-Fe centers through the imidazolate bridges. The antiferromagnetic nature of the compound is also observed in the magnetization graph, where a much lower saturation value than that expected for paramagnetic Fe (II) centers can be seen.
    [0166]
    [0167] Example 3: synthesis of the nanocomposite.
    [0168]
    [0169] For the synthesis of the nanocomposite, the iron ZIF was introduced into a ship with acetonitrile to avoid contact with oxygen in the atmosphere. The inert atmosphere of nitrogen was created and the ramp was made, in which it was burned at 700 ° C for 3.5 h, with a ramp up and down of 2 ° C / min. Once calcined, the nanocomposite obtained by the calcination is washed with a solution of 0.5 M nitric acid for 6 h for the elimination of the remaining metal.
    [0170] Example 4: Characterization of the nanocomposite.
    [0171]
    [0172] X-ray measurements (XRPD) confirm the presence of small traces of iron nanoparticles in the nanocomposite, showing characteristic peaks of metallic iron and graphitic carbon (Figure 4).
    [0173]
    [0174] On the other hand, high-resolution transmission electron microscopy (HRTEM) images show that the structure of the nanocomposite is formed by a graphitized carbon matrix, with iron nanoparticles of an approximate size between 10 and 30 nm, as can be observe in figure 5 A. Said nanoparticles that are in the carbonaceous matrix are also surrounded by layers of graphene (figure 5 B). The formation of carbon nanostructures, such as nanocebollas and graphene layers already mentioned above, can also be clearly observed (figure 5 C and D).
    [0175] The images of the scanning electron microscope (FESEM) of the nanocomposite ( Error! The origin of the reference is not found 6) show how, after calcination, the nanocomposite loses the geometric structure observed in the ZIF. In addition, you can see a structure with different sheets of graphene and many "dimples", which correspond to the pores that provide that high specific area to the nanocomposite.
    [0176]
    [0177] Table 1. Percentages of carbon, nitrogen and oxygen of the composite obtained by X-ray spectroscopy (XPS).
    [0178]
    [0179] C (at.%) N (at.%) O (at.%)
    [0180]
    [0181]
    [0182]
    [0183] The measurements of X-ray spectroscopy (XPS) show that the nanocomposite has a percentage of 90.7; 8.2 and 1.1 in atomic% carbon, oxygen and nitrogen respectively (table 1), which shows that there is a doping of nitrogen. In this measure the iron is not detected, since it is a surface measurement and the nanoparticles are surrounded by several layers of carbon, as seen in the HRTEM images. Regarding nitrogen, we can observe in Figure 8 that pyridine nitrogen and graphitic nitrogen predominate in nitrogen doping (Table 2).
    [0184]
    [0185] Table 2. Percentages of the different types of N obtained by XPS.
    [0186]
    [0187] Pyridine Nitrogen Graphitic Nitrogen
    [0188]
    [0189]
    [0190] Nitrogen doping is very important in this type of composites, since it induces electronic interaction with nearby carbon / metal atoms to provide catalytically active zones and also produces structural defects in the carbon nanoforms to form oxygen adsorption sites. Finally, figure 9 shows the carbon signal, which can be deconvolved in 4 different peaks, from which we extract the proportions of the different types of carbon that appear in table 3.
    [0191]
    [0192] Table 3. Percentages of the different types of carbon obtained through XPS.
    [0193]
    [0194]
    [0195]
    [0196] The atomic emission spectroscopy analyzes by inductively coupled plasma (ICP-OES) indicate that the nanocomposite contains 0.79% by weight of iron.
    [0197]
    [0198] To estimate the surface area of the nanocomposite, the porous texture of the nanocomposite was characterized by tests of nitrogen adsorption (N2) at 77 K and adsorption tests of carbon dioxide (CO 2 ) at 273 K (figures 10 to 12). For this, an AUTOSORB-6 team was used. The samples were degassed for 8 hours at 523 K and 5 10 "5 bar before being analyzed.The surface areas were estimated according to the BET model and the pore size dimensions were calculated with the functional theory of the solid density ( QSDFT) for the adsorption branch assuming a cylindrical pore model.The micropore volumes were determined by applying t-plot and DR methods to the adsorption data of N2 and CO2.
    [0199]
    [0200] Table 2. Porosity data obtained by means of adsorption measurements, from the nitrogen and carbon dioxide isotherms.
    [0201]
    [0202]
    [0203]
    [0204] a Data obtained from N2 adsorption. Specific area calculated with the BET method. Area contributed by micropores SM and external area ST using the t-plot method. b Total volume at P / P0 = 0.96. c Data obtained from CO2 adsorption. Volume of micropores (<0.7 nm) calculated according to the DR method. d Calculated micropore volume of N2 adsorption using the DR method. e Volume of mesoporos calculated according to: Vmeso = VTotal - VmDR. f Volume of mesoporous (Vmeso (P / P0)) calculated from the difference of the total (Vt) to P / P0 and the volume of micropore (Vmicro).
    [0205] The nitrogen isotherms show a type IV adsorption, whose values are illustrated in table 4, showing a specific area of 463 m2g-1. The pore volume of the nanocomposite is 0.96 cm3g-1, which indicates a micropore and mesoporous distribution of approximately 3 nm. For a better study of micropores smaller than 0.7 nm, measurements of CO2 adsorption were made at 273 K. In this case, the measurements indicate a volume of micropores of 0.12 cm3g-1 (figures 10 to 12).
    [0206] The electrocatalytic behavior of the nanocomposite of the present invention was characterized by different electrochemical measurements in a typical 3-electrode cell. For these measurements, different electrolytes with different concentrations were used (that is, media with different pH were used), always using a stainless steel sheet and an Ag / AgCl electrode as counter electrode and reference electrode respectively. The different nanocomposites, embedded in nickel foam for the basic media and carbon felt for the acid media (to avoid the reaction between the nickel foam and the acid) of an area of 0, have been used as working electrodes. 2 cm2. The deposition of the nanocomposites was carried out by preparing a suspension of the material to be analyzed with vinylidene polyfluoride (PVDF) and carbon black (ratio 80:10:10) in ethanol. Once deposited in the nickel foam or carbon felt, it was allowed to dry for 2 h at 80 ° C. To study the electrocatalytic activity of the nanocomposite, basic media (1 M and 0.1 M KOH), acid media (0.5 M H2SO4) and a neutral medium (pH 7 phosphate buffer) were used.
    [0207]
    [0208] To measure its behavior as an oxygen catalyst (OER) it was tested in two basic media (0.1 and 1 M KOH). Measurements of linear voltammetry were made, showing a start of catalysis at 1,542 V and 1,588 V (vs RHE) for the media of 0.1 M and 1 M KOH, respectively. As can be seen in figures 13 and 14, we see that the values obtained with the nanocomposite against their respective targets are much higher, demonstrating that the nanocomposite of the present invention has a high electrocatalytic behavior.
    [0209]
    [0210] Table 5. Voltage values of the start of oxygen catalysis of the material in the different media.
    [0211]
    [0212]
    [0213]
    [0214] For further characterization of its catalytic behavior, other parameters were calculated, such as the overpotential (q) obtained at different current densities (10). and 15 mAcm-2); the current density (j) at an overpotential of n = 300 and 400 mV; and the slopes of Tafel in the different media. In figure 19 we can see the slopes of Tafel in the two basic media, obtaining very low values, being 48 and 37 mV per decade for 0.1 M and 1 M KOH respectively.
    [0215]
    [0216] The stability and durability of the nanocomposite of the present invention was tested by means of a galvanostatic test applying continuous current densities of j = 10 and 15 mAcm-2, and by potentiometric tests applying an overpotential of n = 300 and 400 mV, during 1,000 seconds in both cases. As can be seen in figures 20 to 22, a very good stability is observed in both media, obtaining practically constant values of current density and overpotential.
    [0217]
    [0218] Finally, the behavior of the nanocomposite of the present invention as a hydrogen catalyst (HER) was measured, being tested in basic media (0.1 and 1 M KOH), acid media (H2SO41 and 0.5 M) and in neutral medium (phosphate buffer) of pH 7). Linear voltammetry measurements were made, showing a start of catalysis always above the corresponding target measurement in that medium, as can be seen in figures 15 to 18. The start values of hydrogen catalysis in the different media You can see it in table 6.
    [0219]
    [0220] Table 3. Starting voltage values of hydrogen catalysis of the material in the different media.
    [0221]
    [0222]
    权利要求:
    Claims (45)
    [1]
    1. A zeolitic framework comprising the general structure A-B-A where A is iron and B is a compound of formula I

    [2]
    2. The zeolitic framework according to claim 1, wherein the compound of formula I is imidazolate or 2-methylimidazolate.
    [3]
    3. The zeolitic framework according to any of claims 1 or 2, wherein the compound of formula I is 2-methylimidazolate.
    [4]
    4. The zeolitic framework according to any of claims 1 to 3, wherein said frame has zeolitic SOD topology.
    [5]
    5. The zeolitic framework according to any of claims 1 to 4, wherein said frame has the crystallographic structure of ZIF-8.
    [6]
    6. A process for obtaining the zeolitic framework according to any of claims 1 to 5, comprising the following steps:
    to. mixing ferrocene and a compound of formula I as described in claim 1, in the presence of a template ligand,
    b. heating the sealed mixture of step (a) to a temperature of between 80 and 250 ° C for a time of at least 12 hours.
    [7]
    7. The process according to claim 6, wherein the compound of formula I is 2-methylimidazole.
    [8]
    8. The process according to any of claims 6 or 7, wherein the template ligand is solid at 25 ° C.
    [9]
    9. The process according to any of claims 6 to 8, wherein the mixture of step (a) is prepared in the absence of solvent.
    [10]
    10. The process according to any of claims 6 to 9, wherein the template ligand is an aromatic heterocycle.
    [11]
    11. The process according to any of claims 6 to 10, wherein the template ligand is an aromatic heterocycle wherein the heteroatom is nitrogen.
    [12]
    12. The process according to any of claims 6 to 11, wherein the template ligand is a pyridine or a pyridine derivative.
    [13]
    The process according to any of claims 6 to 12, wherein the template ligand is a bipyridine or a bipyridine derivative.
    [14]
    The process according to any of claims 6 to 13, wherein the template ligand is 4,4-bipyridine.
    [15]
    15. The process according to claim 14, wherein the molar ratio 4,4-bipyridine: 2-methylimidazole in the mixture of step (a) is at least 1.
    [16]
    16. The process according to any of claims 6 to 15, wherein step (b) is carried out at a temperature between 110 and 200 ° C.
    [17]
    17. The process according to any of claims 5 to 16, wherein step (b) is carried out at a temperature between 140 and 160 ° C.
    [18]
    18. The process according to any of claims 6 to 17, wherein step (b) has a duration of between 2 and 6 days.
    [19]
    19. The process according to any of claims 6 to 18, wherein step (b) has a duration of between 3.5 and 4.5 days.
    [20]
    20. A nanocomposite comprising:
    a graphitic carbon matrix and between 0.1 and 3% by weight of iron nanoparticles with respect to the total weight of the nanocomposite,
    where said iron nanoparticles have a diameter between 1 and 60 nm,
    wherein said nanocomposite comprises between 70 and 95% by weight of carbon, between 3 and 20% by weight of oxygen and between 0.2 and 5% by weight of nitrogen, with respect to the total weight of the nanocomposite,
    and wherein said nanocomposite has a current density in the oxygen evolution reaction (OER) greater than 200 mA / cm2 in 1M KOH.
    [21]
    21. The nanocomposite according to claim 20, wherein the pore size is from 0.5 to 15 nm, calculated by adsorption tests.
    [22]
    22. The nanocomposite according to any of claims 20 or 21, wherein the pore size is from 1 to 10 nm, calculated by adsorption tests.
    [23]
    23. The nanocomposite according to any of claims 20 to 22, wherein the pore size is from 3 to 5 nm, calculated by adsorption tests.
    [24]
    24. The nanocomposite according to any of claims 20 to 23, wherein the pore volume is 0.1 to 2 cm3 g-1, calculated by adsorption tests.
    [25]
    25. The nanocomposite according to any of claims 20 to 24, wherein the pore volume is from 0.5 to 1.5 cm3 g-1, calculated by adsorption tests.
    [26]
    26. The nanocomposite according to any of claims 20 to 25, wherein the pore volume is from 0.9 to 1.1 cm3 g-1, calculated by adsorption tests.
    [27]
    27. The nanocomposite according to any of claims 20 to 26, wherein the micropore volume is 0.01 to 1 cm3 g-1, calculated by adsorption tests.
    [28]
    28. The nanocomposite according to any of claims 20 to 27, wherein the micropore volume is 0.05 to 0.5 cm3 g-1, calculated by adsorption tests.
    [29]
    29. The nanocomposite according to any of claims 20 to 28, wherein the micropore volume is 0.09 to 0.11 cm3 g-1, calculated by adsorption tests.
    [30]
    30. The nanocomposite according to any of claims 20 to 29, wherein the BET area is greater than 100 m2 / g, calculated by adsorption tests.
    [31]
    31. The nanocomposite according to any of claims 20 to 30, wherein the BET area is greater than 200 m2 / g, calculated by adsorption tests.
    [32]
    32. The nanocomposite according to any of claims 20 to 31, wherein the BET area is greater than 400 m2 / g, calculated by adsorption tests.
    [33]
    The nanocomposite according to any of claims 20 to 32, wherein said nanocomposite comprises between 80 and 94% by weight of carbon, between 5 and 15% by weight of oxygen and between 0.5 and 3% by weight of nitrogen and between 0.3 to 2% by weight of iron, with respect to the total weight of the nanocomposite.
    [34]
    The nanocomposite according to any of claims 20 to 33, wherein said nanocomposite comprises between 90 and 92% by weight of carbon, between 7 and 9% by weight of oxygen and between 0.8 and 1.2% by weight of nitrogen and between 0.7 and 0.9% by weight of iron, with respect to the total weight of the nanocomposite.
    [35]
    35. The nanocomposite according to any of claims 20 to 34, wherein the iron nanoparticles have a diameter between 5 and 45 nm.
    [36]
    36. The nanocomposite according to any of claims 20 to 35, wherein the iron nanoparticles have a diameter between 10 and 30 nm.
    [37]
    37. The nanocomposite according to any of claims 20 to 36, wherein said nanocomposite has a current density in the oxygen evolution reaction (OER) greater than 230 mA / cm2 in 1M KOH.
    [38]
    38. The nanocomposite according to any of claims 20 to 37, wherein said nanocomposite has a current density in the oxygen evolution reaction (OER) greater than 300 mA / cm2 in 1M KOH.
    [39]
    39. A process for obtaining a nanocomposite according to any of claims 20 to 38 comprising the following steps:
    to. obtaining from a zeolitic framework comprising the general structure A-B-A wherein A is iron and B is a compound of formula I according to any of claims 1 to 5 by a process according to any of claims 6 to 19, and
    b. calcining the zeolitic framework obtained in step (a) at a temperature of between 500 and 900 ° C for a time of at least 1 hour.
    [40]
    40. The process according to claim 39, wherein step (b) is carried out at a temperature between 600 and 800 ° C.
    [41]
    41. The process according to any of claims 39 or 40, wherein step (b) is carried out at a temperature between 680 and 720 ° C.
    [42]
    42. The process according to any of claims 39 to 41, wherein step (b) has a duration of at least 2 hours.
    [43]
    43. The process according to any of claims 39 to 42, wherein step (b) has a duration of at least 3 hours.
    [44]
    44. A nanocomposite obtained by the process according to any of claims 39 to 43.
    [45]
    45. Use of the nanocomposite according to any of claims 20 to 38 or of the nanocomposite according to claim 44, as a catalyst.
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    同族专利:
    公开号 | 公开日
    EP3683224A4|2021-03-03|
    ES2703849B2|2019-11-28|
    CA3074913A1|2019-03-21|
    JP2020535120A|2020-12-03|
    WO2019053312A1|2019-03-21|
    US20200270291A1|2020-08-27|
    EP3683224A1|2020-07-22|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US20070202038A1|2006-02-28|2007-08-30|The Regents Of The University Of Michigan|Preparation of functionalized zeolitic frameworks|
    US20140093790A1|2012-09-28|2014-04-03|Di-Jia Liu|Nanofibrous electrocatalysts|
    CN110474062A|2019-08-02|2019-11-19|北京化工大学常州先进材料研究院|A kind of preparation and application of efficient MXene titanium carbide cell catalyst|
    CN110479302A|2019-08-07|2019-11-22|上海尚析环保设备有限公司|A kind of preparation method of micropore iron carbon composite catalytic agent and thus obtained micropore iron carbon composite catalytic agent and its application|
    CN112371150B|2020-10-26|2021-09-17|厦门大学|Nickel-aluminum bimetal nitrogen-carbon doped catalyst, preparation method thereof and application thereof in catalyzing levulinic acid hydrogenation to prepare gamma-valerolactone|
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