• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
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    • 专利摘要:
    Graphene nanoporous carbon, preparation procedure and use as an electrode. The object of the present invention relates to a new carbon material consisting of a carbon xerogel of high microporosity and mesoporosity and that is doped with a certain amount of graphene homogeneously distributed in its internal structure. Said material has a high specific surface area and a high electrical conductivity, which gives it excellent electrochemical properties for use as a supercapacitor electrode. This material is produced by mixing resorcinol, formaldehyde, methanol, a catalyst and an aqueous suspension of graphene oxide; subjecting this mixture to heating with microwaves and later to a process of carbonization or activation. (Machine-translation by Google Translate, not legally binding)
    公开号:ES2660884A1
    申请号:ES201631248
    申请日:2016-09-26
    公开日:2018-03-26
    发明作者:José Angel MENÉNDEZ DÍAZ；Ana Arenillas De La Puente；Ignacio MARTÍN GULLÓN；Gloria RAMOS FERNÁNDEZ
    申请人:Consejo Superior de Investigaciones Cientificas CSIC；Universidad de Alicante；
    IPC主号:
    专利说明:

    image 1
    GRAPHENED NANOPOROUS COAL, PREPARATION PROCEDURE AND USE AS ELECTRODE DESCRIPTION 5 SECTOR AND OBJECT OF THE INVENTION
    The present invention belongs to the sector of materials with electrochemical applications, specifically that of carbonaceous materials.
    Particularly, the object of the present invention relates to a new carbon material consisting of a carbon xerogel of high microporosity and mesoporosity and which is doped with a certain amount of graphene homogeneously distributed in its internal structure. Said material presents a
    15 high specific surface area and high electrical conductivity, which gives it excellent electrochemical properties for use as a supercapacitor electrode. This material is produced by mixing resorcinol, formaldehyde, methanol, a catalyst and an aqueous suspension of graphene oxide; subjecting this mixture to a microwave heating and subsequently to a process of
    20 carbonization or activation.
    STATE OF THE TECHNIQUE
    Carbon materials do not usually have, in the same material, high
    25 electrical conductivities, specific surfaces and pore volume. This is because an electrical conductivity implies a material with an ordered structure, such as graphite, which in turn implies poor porous properties; that is to say little specific surface and little volume of pores. On the contrary, carbon materials with high specific surface area and high pore volume
    30 are not usually good electrical conductors, since the former implies a disordered nanoporous structure that is not a good conductor of the current. This is a problem in many electrochemical applications of these materials, such as their use as a supercapacitor electrode, where good porous properties and high electrical conductivity are required.
    image2
    Spanish patent ES2354782 describes a method of obtaining organic xerogels analogous to that of the present invention. The resulting carbon xerogels have high specific surface area and high mesoporosity. However, said xerogels are not doped with graphene and therefore, the carbon structure is
    5 different from that of the material object of the present invention. Nor is the electrical conductivity of the material or electrochemical properties mentioned. The proportion of methanol in the precursor solution is not indicated.
    Chinese patent CN103274384 describes an airgel synthesized from resorcinol
    10 and formaldehyde doped with graphene oxide and subsequently carbonized. The gel has a low density and high specific surface. This patent mentions the possible use of this material as an adsorbent. However, it is not mentioned that it has a high electrical conductivity or electrochemical properties suitable for use as a supercapacitor electrode. In addition, the material
    15 has a much lower density than the material object of the present invention and the specific surface does not exceed 1100 m2 / g. The synthesis process of the material is very different from that described in the present invention, with no methanol in the precursor solution.
    20 There are some patents describing graphene aerogels such as US8993113 or US20120034442. However, the structure of these materials, synthesized exclusively from graphene oxide, is very different from that of the material object of this invention, consisting of a nanoporous xerogel doped with graphene. So while the electrical conductivity
    25 of these materials is greater than that of the material described in the present invention, its porous texture is not as developed. For example, specific surface areas are never greater than 1500 m2 / g. On the other hand, these materials do not have micropores, as in the case of the material object of the present invention.
    The patent US 20100144904, is similar to the previous ones although it is mentioned that the graphene airgel can be reinforced with a polymer.
    US20140299818 describes materials that combine a graphite material of high specific surface nanometer size (graphene nanoplateles and / or carbon nanotubes) and other carbon materials (activated carbon, carbon airgel, carbon black). However, these materials are obtained by a physical mixture of the components to form a film, so graphene is not incorporated into the internal structure of the material as in the case of the material object of the
    image3
    5 present invention.
    Patent CN201310590113 describes a method for preparing active carbons doped with graphene, resulting in materials with a high specific surface area and a high graphene content. However, the method of preparation is very different from that of the material object of the present invention, so the resulting structure is also very different as well. On the other hand, the amount of graphene presented by the material is markedly greater than that of the material object of this invention. This patent does not mention that the materials possess mesopores or their conductivity, or their zero charge point. Properties, all of them,
    15 important for use as a supercapacitor electrode.
    WO2013132259 refers to aerogels and xerogels containing graphene and graphene oxide. However, these materials also contain certain metals, the method of production is very different from that described herein.
    20 invention and are applied to capture CO2 and not as supercapacitor electrodes. On the other hand, it is not mentioned that these materials possess high specific surfaces, neither high volume of mesopores, nor high electrical conductivity, nor other properties that characterize the material described in the present invention.
    25 The publication “Carbon-based supercapacitor produced by activation of graphene”, Science, 332 (2011) 1537-1541, describes a nanoporous material based on graphene sheets, with a specific surface area of more than 2000 m2 / g and mesopores around 4 nm, which is used as a supercapacitor electrode. However the
    The material is obtained by activation with KOH of a graphene oxide reduced with a microwave at 800 ° C, a method very different from that described in this patent; Therefore, the resulting structure differs markedly from that of the graphene carbon object of the present invention, since the material does not have the carbon sheets smaller than 10 nm characteristic of the carbon xerogel. In addition, the graphene oxide is used exclusively to obtain the material, so that the amount of graphene in the resulting material is much greater than that of graphene carbon, object of the present invention, in which graphene is found in small proportions No other important properties of the material are mentioned as they are
    image4
    5 its density, zero charge point or chemical composition.
    The publication "An ionic liquid template approach to graphene-carbon xerogel composites for supercapacitors with enhanced performance", Journal of Materials Chemistry A, 2 (2014) 14329-14333, describes a doped carbon xerogel with 10 graphene, which is used as an electrode of supercapacitors. However, said material is synthesized by adding graphene, instead of graphene oxide, to the precursor mixture and using a reaction medium consisting of an ionic liquid that molds the resulting structure. As a consequence, the resulting structure is different from that of the graphene nanoporous carbon object of the present invention.
    In addition, these materials have specific areas smaller than 1000 m2 / g and pore volumes, in general, smaller than those of the material object of the present invention. No other important properties of the material are mentioned, such as its electrical conductivity, density, or zero charge point.
    20 The publication “Graphene cross-linked phenol – formaldehyde hybrid organic and carbon xerogel during ambient pressure drying”, Journal of Sol-Gel Science and Technology, 66 (2013) 1-5, describes a doped carbon xerogel with graphene synthesized from of phenol / formaldehyde and graphene oxide. However, the specific surface area of this material is only 395 m2 / g. In addition, the structure
    25 of this material is very different from that of graphene nanoporous carbon object of the present invention. The publication does not describe other physical or chemical properties of the material.
    The publication “Preparation of highly conductive carbon cryogel based on pristine
    30 graphene ”, Synthetic Metals, 162 (2012) 743-747, describes a graphene-doped carbon cryogel that exhibits high electrical conductivity. However, the specific surface area of this material is a maximum of 244 m2 / g. In addition, both the method of production and the structural and porous characteristics differ markedly from the graphene nanoporous carbon object of the present invention.
    image5
    The document Meng, Fanchang, et al. "Alkali-treated graphene oxide as a solid base catalyst: synthesis and electrochemical capacitance of graphene / carbon composite aerogels" Journal of Materials Chemistry, 2011, vol. 21, no 46, p. 18537-18539 refers to a carbon airgel doped with graphene oxide for use as
    5 electrode in a supercapacitor, among others. Specifically, a carbon material is described in which the amount of graphene oxide is in a proportion of 2% with a pore volume of 0.9%, a surface area of 646 m2 / g, a density of 0.114 g / cm3 and a conductivity of 1.51 S / m. Likewise, it shows a digital image in which it indicates a graphene sheet of length greater than 10 nm.
    Said material is obtained from the sol-gel polymerization of resorcinol and formaldehyde on which a dispersion of graphene stabilized with sodium hydroxide is added.
    However, this is a non-mesoporous material with a specific BET surface that is half that of the material object of the present invention. The method of production is clearly different from that used in the present invention and nothing is mentioned in the document about important chemical properties such as the zero charge point or percentage of impurities.
    20 The document Xia, Xiao-hong et al. "Preparation of high specific surface area composite carbon cryogels from self-assembly of graphene oxide and resorcinol monomers for supercapacitors"; Journal of Solid State Electrochemistry, 2016, vol.20 no. 6, p. 1793-1802, discloses a carbon material doped with graphene that presents
    25 high specific surface for use as an electrode in supercapacitors. In particular, a material with a graphene content of 1.3%, a specific surface area of 1178 m2 / g and a total pore volume of 0.67 cm3 / g having a high electrical conductivity is described. In turn, a method of production is described which comprises the addition of resorcinol (R) and formaldehyde (F) in a
    30 R / F molar ratio of 0.5 to a suspension of graphene oxide in different concentrations (9.1%, 4.8%, 2.0%, 1.3%, 1.0% and 0.7% by weight) and then sodium carbonate. The resulting mixture is subjected to a heat treatment at a temperature of 80 ° C for 168 h, the resulting gel is frozen for 72 h and,
    image6
    finally, it is subjected to a temperature of 900 in an atmosphere of N2 for more than 60 min.
    However, the pore volume of this material and the BET specific surface area are markedly smaller than those of the material object of the present invention. In addition, the method of obtaining is very different from that described in the present invention.
    The document Hen, Tian-Tian; Song, Wei-Li; Fan, Li-Zhen. “Engineering graphene aerogels with porous carbon of large surface area for flexible all-solid-state
    10 supercapacitors ”Electrochimica Acta, 2015, vol. 165, p. 92-97 describes a graphene doped porous carbon airgel with a C content of 91.97%, N of 1.2% and O of 6.83%. In turn, it has a surface area of 1221 m2 / g, a total pore volume of 0.305 cm3 / g and a micropore volume of 0.333 cm3 / g. Said material shows high capacitance values.
    However, this material is based exclusively on graphene, so its nanometric structure is completely different from that of the material object of the present invention. In addition, it has a higher percentage of heteroatoms and a smaller pore volume than the material object of the present invention. Also this
    20 material is not mesoporous.
    In view of the state of the art it is concluded that it would be of interest to have carbonaceous materials that simultaneously present high specific surfaces and electrical conductivities. 25 EXPLANATION OF THE INVENTION
    The material object of the present invention improves other existing nanoporous carbon materials, in the sense that it jointly presents good
    30 porous properties, comparable to those of activated carbon with a high specific surface area, and an electrical conductivity superior to that of other nanoporous carbon with a high specific surface area. For the manufacture of the material, small amounts of graphene oxide are used, which give rise to small percentages of graphene in the structure of the material, but homogeneously distributed. This


    It represents an economic advantage over materials composed exclusively of graphene or with high proportions of graphene, as production costs do not increase significantly, compared to those of undoped material with graphene.
    5 Different terms used throughout the description of the present invention are defined below:
    Organic xerogel is defined as a type of organic gel that is obtained under pressure
    10 atmospheric and at temperatures close to the ambient temperatures (never negative and at a maximum of about 100 ºC). Examples include among other xerogels based on resorcinol / formadehyde (xerogel RF), phenol / formaldehyde and, in general, any product of the polymerization of a hydroxylated benzene, such as, for example, resorcinol, phenol and catechol, and an aldehyde, such as, among others,
    15 formaldehyde and furfural.
    Carbon xerogel is defined as an organic gel subjected to a carbonization process. If the process is activation the resulting material is defined as activated carbon xerogel.
    20 Carbonization is defined as the thermal process at high temperatures (700 ° C - 1100 ° C) in which the decomposition and transformation of the organic xerogel into a carbon material takes place. This process can take place in an inert atmosphere or in the presence of an activating agent, in which case it is defined as activation.
    Activating agent is defined as a reagent capable of partially oxidizing an organic substrate resulting in the formation of pores. For example, water vapor, oxygen, air or carbon dioxide are gasifying agents.
    30 Graphene oxide is defined as a material consisting of one or more sheets composed of carbon atoms containing oxygenated groups both at the edges of the sheets (mainly) and at the basal plane. If this material is dispersed in water, it is called an aqueous graphene oxide suspension. When this material is reduced, that is, oxygen is removed, by a process


    of carbothermia, that is to say reaction with carbon at high temperature, results in sheets of carbon atoms that are called graphene.
    Microwave oven is defined as a device capable of generating microwaves with
    5 sufficient power to reach the temperatures of the gelation process and which are transmitted to a cavity where the precursor mixture of the organic xerogel is found.
    Pore volume is defined as the volume occupied by empty spaces or 10 gaps within a particle of a material.
    Pore size is defined as the distance between two opposite walls of an internal pore or hole. Thus, the pore whose size is between 2 and 50 nm is defined as mesopore, and the pore whose size is less than 2 nm is micropore.
    15 Nanoporous material is defined as a porous material that has a high volume of pores with a size in the order of the nanometers and mainly microporous and mesoporous. Specific surface is defined as the ratio between the total surface area of a
    20 solid and its mass. The specific surface of the materials mentioned in the present invention has been calculated by applying the BET method to the adsorption isotherms of N2 to 77K.
    Density is defined as the amount of material mass in a given
    25 volume, expressed in g / cm3. The density of the materials mentioned in the present invention has been measured by helium pycnometry (dHe) and by the packing method (demp); The latter consists in measuring the volume occupied by particles of the material, of size <75 microns, and compacted in a graduated specimen by applying a systematized patter.
    30 Zero charge point (pHpzc) is defined as the pH at which the electrical charge on the surface of the material submerged in an electrolyte has a net value of zero; that is, the amount of negative and positive charges on the surface of the material is the same. The zero charge point is an important property in the formation of the electrical double layer of supercapacitors. The zero charge point of a material determines in some way behavior as an electrode of that material based on the pH of the medium and the type of electrolyte. For example, if the pH of the medium is higher than the pHpzc of the electrode, it will have a negative net charge and therefore the
    image7
    5 cation adsorption; if the pH of the medium is below the pHpzc of the electrode, it will have a positive net charge and therefore anion adsorption will be favored. However, this property is usually ignored by the producers of carbonaceous materials for electrodes.
    10 Electrical conductivity (k) is defined as the ability of a material to freely circulate the electric current expressed in siemens per centimeter (S / cm). The electrical conductivity is the inverse of the resistivity (R). The electrical conductivity of the materials mentioned in this patent is measured using the 4-pointed method (based on the Van der Pauw equation) by applying to sheets of material
    15 compacted at 20 ° C. Typical values of k for porous carbon materials measured by this method vary between 0.2 S / cm and 1 S / cm.
    Electrical capacity or capacitance is defined as the capacity of a material to maintain an electrical charge or as the amount of electrical energy that can be stored for a given difference in electrical potential. The electrical capacities of the materials mentioned in this patent are expressed in Farads per gram (F / g) and are calculated from a galvanostatic test carried out on a potentiostat-galvanostat (VSP Biological Science Instruments). The test is carried out on a 2 mm diameter and 0.18 mm thick disc of powder material 25 (particles below 75 microns) mixed with a Teflon suspension in a proportion of 10% by weight. The disc is obtained in a press in which a force of 10 tons is applied for 10 seconds. The disc is mounted in a Swagelok® cell to which a solution of 1 molar H2SO4 is added, until the disc is completely soaked. Cyclic voltammetry is carried out at 0.2 Amps (A) and
    30 a potential window ranging from 0.6 to 1.2 volts (V). The galvanostatic test is carried out at 1 V and the specific current intensity is varied between 0.1 and 16 (A / g).
    The capacity of the supercapacitor is calculated C = (Δt / ΔV) Ie; where C is the capacity expressed in farads / gram, Δt is time invested in achieving the difference of


    ΔV potential expressed in seconds, ΔV corresponds to the potential window corresponding to the supercapacitor discharge, and Ie is the specific current intensity expressed in amps / gram. The capacity of each electrode of the supercapacitor Ce would be the capacity of the supercapacitor multiplied by 2.
    5 The specific energy (E) of the supercapacitor at a specific specific current intensity is calculated as
    E (Wh / kg) = [C (ΔV) 2] / [7200 m];
    10 where C is the capacity of the electrode (F), ΔV is the potential window, and m equals the mass of an electrode in kg.
    The Specific Power of the supercapacitor (P) is calculated as 15 P (W / kg) = [(ΔV-ΔU) 2] / 4ESRm;
    where ΔV is the potential window (V), ΔU is the ohmic drop (V), ESR is the equivalent series resistance (Ω) and m the mass of an electrode.
    A first object of the present invention is a graphene-doped nanoporous carbon material having: -a content of more than 90% by weight of carbon -a content of heteroatoms less than 5% by weight -a content of inorganic impurities less than 0.5% by weight
    25 -a pore volume between 0.5 cm3 / g and 2 cm3 / g -a helium density between 1 g / cm3 and 2.5 g / cm3 -a packing density between 0.1 g / cm3 and 0.5 g / cm3 - a zero charge point between 7 and 14 - a quantity of graphene between 0.5% and 5% by weight, with graphene being
    30 in the form of sheets with a length greater than 10 nm embedded and distributed homogeneously within the material.
    The material is characterized in that it has a specific surface area between 750 m2 / g and 2500 m2 / g and an electrical conductivity greater than 1.60 S / cm


    In a preferred embodiment of the invention, the material has: -a carbon content greater than 95% by weight -heteroatoms are H, O or N or combinations thereof -a content in inorganic impurities is less than 0, 1% by weight
    5 -a pore volume greater than 1 cm3 / g -a specific surface area between 1200 m2 / g and 2500 m2 / g -a density of helium between 2 g / cm3 and 2.5 g / cm3 -a package density included between 0.2 g / cm3 and 0.4 g / cm3 - zero load point between 8 and 10.
    10 In an even more preferred embodiment, the volume of mesopores is between 0.2 cm3 / g and 1 cm3 / g with an average mesopore size between 2 nm and 20 nm and the volume of micropores is between 0.2 cm3 / g and 1 cm3 / g. Particularly, the volume of mesopores is greater than 0.5
    15 cm3 / g with an average size between 4 and 10 nm and the micropore volume is greater than 0.5 cm3 / g.
    In successive preferred embodiments of the material, the amount of graphene is between 1.5% and 5% by weight and has an electrical conductivity greater than 20 to 3 S / cm.
    A second object of the present invention is a process for preparing a graphene-doped nanoporous carbon material comprising:
    25 -resorcinol mixture in proportions between 3% and 44% by weight with -formaldehyde in proportions between 5% and 30% by weight -methanol in proportions between 3% and 22% by weight -water in proportions between 36% and 87% by weight and - graphene oxide in proportions between 0.1% and 1% by weight
    30 -addition of a catalyst until the pH of the resulting mixture is adjusted between 3.0 and 7.0. - homogenization of the mixture obtained in the previous stages - heat treatment at atmospheric pressure, in an air atmosphere and at temperatures between 50 ºC and 100 ºC for a period of time between 1 h and 96 h obtaining an organic xerogel doped with graphene oxide


    -treatment of the organic xerogel obtained in the previous stage at temperatures between 800 ° C and 1100 ° C for at least 60 min obtaining a carbon xerogel and reducing graphene oxide to graphene.
    In a preferred embodiment, the step of mixing resorcinol with formaldehyde, methanol, water and graphene oxide is carried out in the following proportions:
    -between 18% and 28% by weight of resorcinol -between 10% and 15% by weight of formaldehyde
    10 -between 3% and 8% by weight of methanol -between 53 and 67% by weight of water -between 0.2% and 0.5% by weight of graphene oxide
    The catalyst added for pH adjustment can be:
    15 -a basic catalyst selected from Ca (OH) 2, Na (OH), K (OH), CaCO3 or combinations thereof. - an acid catalyst that is selected from H2SO4, HNO3, CH3COOH or combinations thereof.
    20 As for the heat treatments: -the one of the precursor mixture is carried out at temperatures between 80 ºC and 90 ºC which can be done in a conventional oven for a period of time between 24 h and 96 h in a microwave oven for a period of time between 1 h and 6 h.
    The heat treatment of the organic xerogel is carried out at a temperature between 900 ° C and 1000 ° C and can be carried out in an inert atmosphere, for example of N2, or in an oxidizing atmosphere, for example of water vapor, or of CO2 with a CO2 flow rate between 1 and 10 m3 / h.kg, preferably between 2 and 6 m3 / h.kg, for at least 60 min.
    Finally, it is a third object of the present invention to use graphene-doped nanoporous carbon material as a supercapacitor electrode.
    BRIEF DESCRIPTION OF THE FIGURES


    Figure 1: Images taken with an HRTEM microscope of (a and b) the structure of graphened nanoporous carbon (GC); (c) structure of graphene nanoporous carbon at fewer increases; and (d) carbon xerogel (XE).
    5 Figure 2: Image taken with an SEM microscope of the structure of the graphered porous carbon (GC).
    DETAILED DESCRIPTION OF THE INVENTION
    The material object of the present invention has a structure composed of a certain amount of graphene sheets; that is to say laminar structures composed of carbon, with a length greater than 10 nm. These graphene sheets are embedded and distributed homogeneously within the material whose structure is similar to that of a carbon xerogel; that is small sheet structures
    15 composed of carbon, with a length less than 10 nm. These structures are visible by HRTEM microscopy (Figure 1). The amount of graphene can vary between 0.5% by weight and 5% by weight and preferably between 1.5% by weight and 5% by weight. This amount is sufficient to reach the electric percolation point; that is, all graphene sheets are interconnected between
    20 yes. Graphene sheets, in turn, serve as a connection between the smaller carbon sheets (<10 nm), characteristic of carbon xerogels. This type of structure, unique to the graphene nanoporous carbon object of this invention, favors the movement of electrons within the material and, therefore, causes the material to have a good electrical conductivity.
    As for the properties related to porosity, the material has a structure formed by agglomerates, more or less spherical, joined together and gaps (pores) between these agglomerates (Figure 1c and Figure 2). These holes are the mesopores and the macropores; while the micropores are located within the
    30 mentioned spherical agglomerates. The size of these carbon agglomerates can vary between 5 nm and 50 nm. On a smaller scale, these agglomerates have the structure formed by the carbon (<10 nm) and graphene (> 10 nm) sheets described above.
    image8
    The material preparation process requires very little graphene oxide (less than 1% by weight). However, the proportion of graphene in the resulting material is higher, and can be up to 5% by weight. This is because there is release of volatile substances in the different stages of
    5 synthesis, which causes graphene to concentrate on the resulting material. The use of small amounts of graphene facilitates the preparation of aqueous suspensions of this material. On the other hand, when very little graphene oxide is used, the impact on the production costs of the material is very low.
    10 The procedure includes the following stages:
    Preparation stage of the precursor mixture
    In a container that allows stirring, they are mixed:
    15 (i) resorcinol in proportions that can vary between 3 and 44% by weight, preferably between 18 and 28% by weight;
    (ii) formaldehyde in proportions that can vary between 5 and 30% by weight, preferably between 10 and 15% by weight;
    (iii) methanol in proportions that can vary between 0 and 22% by weight, preferably between 3 and 8% by weight;
    (iv)  water in proportions that can vary between 36 and 87% by weight, preferably between 53 and 67% by weight and
    (v) Graphene oxide in proportions that can vary between 0.1 and 1% by weight, preferably between 0.2 and 0.5% by weight.
    For this, an aqueous suspension of graphene or, preferably, graphene oxide is prepared; by adding graphite oxide or pristine graphite in water; without or with the help of surfactants. This suspension, which is in concentrations between 0.1 and 10 mg / L and preferably between 2 and 5 mg / L, is subjected to an exfoliation process with
    30 ultrasound, high shear or hydrothermal; with which a stable dispersion of monoláminas in the sine of the water is obtained; which, in turn, allows to obtain a homogeneous distribution of graphene in the resulting graphene nanoporous carbon.
    image9
    Once these components have been mixed, a basic catalyst is added, such as: Ca (OH), Na (OH), K (OH), CaCO3, or any other base, but preferably Ca (OH) or Na (OH); or an acid catalyst, such as: H2SO4, HNO3, CH3COOH or any other acid, but preferably HNO3 or CH3COOH. This
    The catalyst is added until the pH of the resulting mixture is adjusted between 3.0 and 7.0, preferably between 5.8 and 6.8.
    Stage of gelation, curing and drying
    10 Once the precursor mixture is homogenized, it is poured into a suitable container and subjected to a heat treatment at atmospheric pressure, in an atmosphere of air and at temperatures that can vary between 50 ° C and 100 ° C, but preferably enters 80 ° C and 90 ° C. This stage can be carried out in a normal stove or in a microwave oven, the latter being preferable, since by drastically shortening the times
    15 of this stage allows an industrial production of the material and a reduction in the production costs of the same. In the case of using a normal stove, the time necessary to carry out this stage must be at least 24 hours and preferably 96 hours. In the case of using a microwave oven this stage may vary between 1 hour and 6 hours, with 3 hours to 5 hours being preferable. In this
    In the process, a material that can be called organic xerogel doped with graphene oxide is obtained.
    Carbonization stage and activation and reduction of graphene oxide
    The organic xerogel doped with graphene oxide is then subjected to a new thermal process, at temperatures that can range between 800 ° C and 1100 ° C, but preferably between 900 ° C and 1000 ° C. This process can be carried out in an inert atmosphere, such as N2, or in some oxidizing atmosphere, such as water vapor or CO2, this being preferable.
    30 last option. If CO2 is used as an activating agent, the CO2 flow rate can vary between 1 and 10 m3 / hkg and preferably between 2 and 6 m3 / hkg. The duration of this stage must be at least 60 minutes. During this stage volatile substances are removed and the organic xerogel is transformed into a xerogel of


    carbon. Likewise, graphene oxide is reduced to graphene by the combined action of temperature and carbon.
    The material resulting from this stage is the material object of the invention: a carbon of
    5 high purity (carbon content greater than 95% by weight), high porosity composed of micropores and mesopores, large specific surface area and high electrical conductivity, due to the presence of graphene sheets homogeneously distributed within the material. These characteristics make it the ideal material for use as a supercapacitor electrode.
    10 EMBODIMENT OF THE INVENTION Example 1: Tables showing the characteristics of a graphene-doped nanopore material (CG) are shown and compared with a commercial nanoporous activated carbon, for use
    15 typical in supercapacitor electrodes (KU), and with a nanoporous carbon xerogel not doped with graphene (XE). Figures 1a and 1b show photographs obtained with an HRTEM microscope in which it can be seen how the material is doped with graphene sheets.
    Chemical properties
    %C %OR% H% N% impuritiespHpzc% graphene
    CG 96.90.22.80.1<0.19.92.4
    XE 96.90.32.70.1<0.19.00
    Ku 96.60.32.10.50.57.00
    Physical properties
    Vp (cm3 / g) Vmeso (cm3 / g)dmeso (nm)Vmicro (cm3 / g)SBET (m2 / g)dHe (g / cm3)demp (g / cm3)k (S / cm)
    CG 1.20.680.61,5562.240.223.1
    XE 1.10.670.61,5992.230.231.1
    Ku 0.70.220.61,6792.380.310.5
    The chemical composition of the three materials is similar, although CG has a zero charge point (pHpzc) higher than the other materials. The porous properties of 17
    image10
    CG and XE are similar and both have a larger pore volume than KU and a mesopore volume that triples that of KU. The average size of the mesoporos of the graphene-doped material is also similar to that of the non-doped and is around 8 nm, while the KU reference carbon barely has larger mesopores
    5 of 2 nm. The electrical conductivity of CG is almost triple that of XE (an increase of 182%) and more than 6 times (an increase of 520%) that of KU. Only CG contains graphene in its structure, in a proportion of 2.4% by weight.
    The images in Figures 1a and 1b, taken using an HRTEM microscope,
    10 clearly show how graphene sheets, with lengths greater than 10 nm, are homogeneously distributed within the CG material. There is also a similar photograph of carbon xerogel not doped with graphene (Figure 1d) with which the material (XE) is compared. In the latter you can see the typical structure of these materials, with carbon laminar structures below
    15 10 nm, but no graphene sheet is observed. The CG material therefore has a structure that combines the structure of the xerogels with graphene sheets distributed homogeneously within the material.
    On a larger scale (Figure 1c and Figure 2), it can be seen that porous coal
    Graphene (CG) has a structure formed by agglomerates, more or less spherical, connected to each other, but leaving gaps (pores) between these agglomerates. These holes correspond to the macropores and mesopores; while micropores (not visible) are found within the agglomerates
    25 Example 2: A typical recipe of a precursor mixture with which the material whose properties are shown in example 1 is shown is shown in the table.
    Characteristics of the precursor mixture to obtain CG
    %Beef. % For.% Met.% H2O% OGpH
    CG 22.712.43.361.40.26.5
    % Res .: mass percentage of resorcinol added; % For .: mass percentage of formaldehyde added; % Met .: mass percentage of methanol added;


    % H2O: mass percentage of water added; % OG: mass percentage of graphene oxide added; pH: pH to which the mixture was adjusted by adding NaOH until reaching this pH.
    This mixture was subjected to microwave heating at a temperature of 85 ° C for a time of 4 h, thus obtaining the organic xerogel. It was subsequently ground and subjected to heating in an electric oven at 1000
    5 ° C for a time of 3 h while passing a CO2 flow rate of 5 m3 / h.kg, thus obtaining the nanoporous carbon doped with graphene CG, the characteristics of which have been shown in example 1.
    Example 3
    It is shown as a supercapacitor that uses electrodes made with the material object of the invention has a capacitance (C, expressed in F / g), a specific energy (E, expressed in Wh / kg) and a specific power (P, expressed in W / kg) much larger than those presented by capacitors that use electrodes
    15 made with the undoped carbon xerogel with graphene (XE) or with commercial activated carbon (KU), with which they are compared. These increases are all the greater, the higher the specific current intensity that is applied in the supercapacitor; being able to be of: up to 41% or 138% in the capacitance, for XE and KU, respectively; 46% or 167% in energy
    20 specific, for XE and KU, respectively and 136% or 599% in specific power, for XE and KU, respectively. In addition, the decrease in capacitance and specific energy, by increasing the specific current intensity, is much smaller when the graphene carbon is used as an electrode, object of this patent, than when using any of the other two materials with which It compares;
    25 being 22% in the case of CG, 30% in the case of XE and 61% in the case of KU.
    The supercapacitor is constructed with a Swagelok® cell that uses a 1 molar solution of H2SO4 as an electrolyte. Each electrode consists of a 10 mm diameter and 0.18 mm thick disk; which is manufactured by compressing the pulverized material
    30 below 75 microns, and mixed with a Teflon suspension in a proportion of 10% by weight, to which a force of 10 tons is applied for 10 seconds. The data shown in the table correspond to a voltage of 1 V, while the specific current intensity of the measurement is expressed with the corresponding sub-index, this being: 0.2 A / g, 6 A / g and 16 A / g.
    image11
    Electrochemical properties C C6 C16 E0.2 E6 E16 P0.2 P6 P16
    (F / g) (F / g) (F / g) (Wh / kg) (Wh / kg) (Wh / kg) (W / kg) (W / kg) (W / kg) CG 146 124 114 20 17 16 43167 45053 45645 XE 120 91 85 16 12 11 16020 19804 19316 KU 126 83 48 17 11 6 10005 9712 6533
    权利要求:
    Claims (15)
    [1]
    image 1
    1.-Graphene-doped nanoporous carbon material that presents: -a content of more than 90% by weight of carbon
    5 -a content of heteroatoms less than 5% by weight -a content of inorganic impurities less than 0.5% by weight -a pore volume between 0.5 cm3 / g and 2 cm3 / g -a density of helium between 1 g / cm3 and 2.5 g / cm3 - a packing density between 0.1 g / cm3 and 0.5 g / cm3
    10 -a zero load point between 7 and 14 -a quantity of graphene between 0.5% and 5% by weight, with graphene in the form of sheets with a length greater than 10 nm embedded and distributed homogeneously in the breast of the material characterized in that the material has a specific surface area between 750 m2 / g and 2500 m2 / g and a conductivity
    15 electrical exceeding 1.60 S / cm
    [2]
    2. Nanoporous carbon material according to claim 1, characterized in that: -the carbon content is greater than 95% by weight -heteroatoms are H, O or N or combinations thereof
    20 -the content of inorganic impurities is less than 0.1% by weight -the pore volume is greater than 1 cm3 / g -the specific surface area between 1200 m2 / g and 2500 m2 / g -the density of helium is between 2 g / cm3 and 2.5 g / cm3 - the packing density is between 0.2 g / cm3 and 0.4 g / cm3
    25 -the zero charge point is between 8 and 10.
    [3]
    3. Nanoporous carbon material according to any one of claims 1 or 2, characterized in that it has: -a volume of mesopores comprised between 0.2 cm3 / g and 1 cm3 / g with a size
    30 mesopore medium comprised between 2 nm and 20 nm -a volume of micropores comprised between 0.2 cm3 / g and 1 cm3 / g 4.-Nanoporous carbon material according to claim 3, characterized in that the volume of mesopores is greater than 0 , 5 cm3 / g with an average size between 4 and 10 nm and the micropore volume is greater than 0.5 cm3 / g.
    image2
    5. Nanoporous carbon material according to any one of claims 1 to 4, characterized in that the amount of graphene is between 1.5% and 5% by weight.
    [6]
    6. Nanoporous carbon material according to any one of claims 1 to 10 5, characterized in that it has an electrical conductivity greater than 3 S / cm.
    [7]
    7. Process for preparing a graphene-doped nanoporous carbon material as defined in claims 1 to 6, comprising: -resorcinol mixture in proportions between 3% and 44% by weight with
    Formaldehyde in proportions between 5% and 30% by weight, with methanol in proportions between 3% and 22% by weight, with water in proportions between 36% and 87% by weight and with graphene oxide in proportions between 0.1% and 1% by weight -addition of a catalyst until the pH of the resulting mixture is adjusted between 3.0 and 7.0.
    20 - homogenization of the mixture obtained in the previous stages - heat treatment at atmospheric pressure, in an air atmosphere and at temperatures between 50 ºC and 100 ºC for a period of time between 1 h and 96 h obtaining an organic xerogel doped with oxide of Graphene - heat treatment of the organic xerogel obtained in the previous stage at temperatures
    25 between 800 ° C and 1100 ° C for at least 60 min obtaining a carbon xerogel and reducing graphene oxide to graphene.
    [8]
    8. Method according to claim 7, characterized in that: the step of mixing resorcinol with formaldehyde, methanol, water and graphene oxide
    30 is carried out in the following proportions: - between 18% and 28% by weight of resorcinol - between 10% and 15% by weight of formaldehyde - between 3% and 8% by weight of methanol - between 53 and 67% by weight of water - between 0.2% and 0.5% by weight of graphene oxide
    image3
    [9]
    9. Method according to claims 7 or 8, characterized in that the catalyst is a basic catalyst.
    Method according to claim 9, characterized in that the basic catalyst is selected from Ca (OH) 2, Na (OH), K (OH), CaCO3 or combinations thereof.
    11. Method according to claims 7 or 8, characterized in that the catalyst is an acid catalyst.
    [12]
    12. Method according to claim 11, characterized in that the acid catalyst is selected from H2SO4, HNO3, CH3COOH or combinations thereof.
    13. Method according to any one of claims 6 to 12, characterized in that the heat treatment of the precursor mixture is carried out at temperatures between 80 ° C and 90 ° C.
    14. Method according to any one of claims 7 to 13, characterized in that the heat treatment of the precursor mixture is carried out in a conventional oven for a period of time between 24 h and 96 h.
    [15]
    15. Method according to any one of claims 7 to 13, characterized in that the heat treatment of the precursor mixture is carried out in a microwave oven for a period of time between 1 h and 6 h.
    [16]
    16. Method according to any one of claims 1 to 15, characterized in that the thermal treatment of the organic xerogel is carried out at a temperature between 900 ° C and 1000 ° C.
    [17]
    17. Method according to any one of claims 1 to 16, characterized in that the thermal treatment of the organic xerogel is carried out in an inert atmosphere.
    image4
    [18]
    18. Method according to claim 17, characterized in that the heat treatment of the xerogel is carried out under an N2 atmosphere.
    [19]
    19. Method according to any one of claims 1 to 16, characterized in that the heat treatment of the organic xerogel is carried out in an oxidizing atmosphere.
    [20]
    20. Method according to claim 19, characterized in that the thermal treatment of the organic xerogel is carried out in a water vapor atmosphere.
    21. Method according to claim 19, characterized in that the thermal treatment of the organic xerogel is carried out in a CO2 atmosphere with a CO2 flow rate between 1 and 10 m3 / h.kg for at least 60 min.
    22. 22. Method according to claim 21, characterized in that the CO2 flow is between 2 and 6 m3 / h.kg
    [23]
    23. Use of a graphene-doped nanoporous carbon material as defined in claims 1 to 6 as a supercapacitor electrode.
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    同族专利:
    公开号 | 公开日
    ES2660884B1|2019-01-15|
    WO2018055226A3|2018-08-09|
    WO2018055226A2|2018-03-29|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    CN103274384B|2013-04-24|2015-05-13|中科院广州化学有限公司|Graphene oxide reinforced carbon aerogel material, and preparation method and application thereof|
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