Preparation method and application of coal tar-based porous carbon

Abstract

The present application belongs to the field of material preparation technology, and specifically relates to a preparation method of coal tar pitch-based porous carbon and its application. The preparation method of the coal tar pitch-based porous carbon comprises the following steps: (1) subjecting the coal tar pitch to a first high-temperature thermal shock treatment in an air atmosphere to obtain pre-oxidized asphalt; (2) subjecting the pre-oxidized asphalt to a second high-temperature thermal shock treatment in an inert atmosphere to obtain pre-carbonized asphalt; (3) mixing the pre-carbonized asphalt with an activator to obtain a mixed powder, and subjecting the mixed powder to a third high-temperature thermal shock treatment to obtain coal tar pitch-based porous carbon. The beneficial effects of the present application include: the preparation method of the present application utilizes high-temperature thermal shock to pre-oxidize the coal tar pitch, thereby increasing the specific surface area of ​​the coal tar pitch porous carbon; and adopts high-temperature thermal shock to pre-carbonize the pre-oxidized asphalt, thereby increasing the carbon yield and stability of the final product, so that the coal tar pitch-based porous carbon has an ideal porous structure and a high specific surface area.

Description

Technical Field

[0001] The present invention belongs to the technical field of material preparation, and in particular relates to a preparation method of coal tar pitch-based porous carbon and application thereof. Background Art

[0002] High-stability coal liquefaction pitch is a heavy organic material extracted from coal through the coal liquefaction process. It has a complex chemical composition, high carbon content, good thermal stability, and high viscosity. It is a carbon source for preparing materials such as porous carbon, activated carbon, and carbon fiber. It has important applications in fuel cells, supercapacitor electrode materials, and catalyst supports.

[0003] There are many methods for preparing porous carbon from coal liquefaction pitch, including pyrolysis, chemical activation, physical activation, and template methods. The pyrolysis method involves heating coal tar pitch in an inert atmosphere at high temperature to decompose it into a porous structure. This method is simple and easy to mass-produce, but it is not conducive to regulating the pore structure and specific surface area of ​​the carbon material. The chemical activation method involves mixing coal tar pitch with a chemical activator (e.g., KOH, NaOH, K2CO3, Na2CO3, KCl, NaCl, H3PO4, etc.) and reacting them at high temperature to produce porous carbon. Although this method can significantly increase the specific surface area and pore structure of the carbon material, it is costly and difficult to handle. The physical activation method involves first carbonizing the coal tar pitch at high temperature and then activating it with a gas (carbon dioxide, water vapor) at high temperature. The resulting porous structure is relatively uniform, but this method has low activation efficiency and requires high energy. The template method involves mixing coal tar pitch with a hard template such as silica or magnesia or a soft polymer template, followed by carbonization and acid washing. This allows for precise control of pore size and pore structure, but the process is complex and may cause environmental pollution. Summary of the Invention

[0004] The present application provides a preparation method and application of coal tar pitch-based porous carbon, aiming to solve the problems of the existing coal tar pitch-based porous carbon in that the specific surface area and pore size distribution are difficult to control, and the preparation process is complex, inefficient and costly.

[0005] In a first aspect of the present application, a method for preparing coal tar pitch-based porous carbon is provided, comprising the following steps:

[0006] (1) subjecting the coal tar pitch to a first high-temperature thermal shock treatment in an air atmosphere to obtain pre-oxidized asphalt;

[0007] (2) subjecting the pre-oxidized asphalt to a second high-temperature thermal shock treatment in an inert atmosphere to obtain a pre-carbonized asphalt;

[0008] (3) The pre-carbonized asphalt and activator potassium hydroxide are mixed to obtain a mixed powder, and the mixed powder is subjected to a third high-temperature thermal shock treatment to obtain coal tar-based porous carbon.

[0009] The preparation method described in this application utilizes high-temperature thermal shock to pre-oxidize coal tar pitch, introduce oxygen-containing functional groups, increase the content of heteroatoms, and further promote the decomposition of polycyclic aromatic hydrocarbons into small molecules, so as to improve the subsequent activation of carbonized asphalt and increase the specific surface area of ​​coal tar pitch porous carbon.

[0010] Using high-temperature thermal shock to pre-carbonize pre-oxidized pitch promotes the polymerization of coal-tar pitch precursors and improves the carbon yield of the final product. During the high-temperature thermal shock activation process, the activator instantly melts into small droplets. The instantaneous Joule heating from the high-temperature rapid quench effectively creates a large number of pores with uniform size distribution in the coal-tar pitch, making it easier for the coal-tar pitch to interact with the activator, resulting in porous carbon with an ideal porous structure and high specific surface area. This method overcomes the problems of traditional methods, such as long activation time, high cost, large and uneven pore structure, and relatively low specific surface area.

[0011] The prepared porous carbon with high specific surface area is used as a support for fuel cell catalysts, has high catalytic activity and stability, and shows excellent electrochemical performance.

[0012] According to some embodiments of the method for preparing coal tar pitch-based porous carbon described in the present application, in step (1), the voltage of the first high-temperature thermal shock treatment is 350-400V, and the current of the first high-temperature thermal shock treatment is 25-35A.

[0013] According to some embodiments of the method for preparing coal tar pitch-based porous carbon described in the present application, the power of the first high-temperature thermal shock treatment is 18-25 kW, and the time of the first high-temperature thermal shock treatment is 5-15 s.

[0014] According to some embodiments of the method for preparing coal tar-based porous carbon described in the present application, in step (2), the voltage of the second high-temperature thermal shock treatment is 350-400V; the current of the second high-temperature thermal shock treatment is 25-35A.

[0015] According to some embodiments of the method for preparing coal tar pitch-based porous carbon described in the present application, the power of the second high-temperature thermal shock treatment is 28-32 kW, and the time of the second high-temperature thermal shock treatment is 5-20 s.

[0016] According to some embodiments of the method for preparing coal tar pitch-based porous carbon described in the present application, in step (3), the mass ratio of the pre-carbonized asphalt to the activator is (1-4):1.

[0017] According to some embodiments of the method for preparing coal tar pitch-based porous carbon described in the present application, the activator includes one or more of NaOH, K2CO3, Na2CO3, ZnCl2, KCl, NaCl and H3PO4.

[0018] According to some embodiments of the method for preparing coal tar pitch-based porous carbon described in the present application, the voltage of the third high-temperature thermal shock treatment is 350-400V; the current of the third high-temperature thermal shock treatment is 25-35A.

[0019] According to some embodiments of the method for preparing coal tar pitch-based porous carbon described in the present application, the power of the third high-temperature thermal shock treatment is 40-48 kW, and the time of the third high-temperature thermal shock treatment is 10-30 s.

[0020] According to some embodiments of the method for preparing the coal tar pitch-based porous carbon described in the present application, the preparation method further includes cleaning and drying the product after the third high-temperature thermal shock treatment.

[0021] According to some embodiments of the method for preparing coal tar pitch-based porous carbon described in the present application, the cleaning is performed sequentially using hydrochloric acid and water; more preferably, the concentration of the hydrochloric acid is 1-3 mol / L.

[0022] According to some embodiments of the method for preparing coal tar pitch-based porous carbon described in the present application, the cleaning is ultrasonic cleaning, and the cleaning time is 30-60 minutes.

[0023] According to some embodiments of the method for preparing coal tar pitch-based porous carbon described in the present application, the drying temperature is 50-70° C., and the drying time is 8-12 hours.

[0024] According to some embodiments of the method for preparing the coal tar pitch-based porous carbon of the present application, the specific surface area of ​​the coal tar pitch-based porous carbon is 1100-1200 m 2 / g.

[0025] According to some embodiments of the method for preparing the coal tar pitch-based porous carbon of the present application, the pore volume of the coal tar pitch-based porous carbon is 1.0-2.0 cm 3 / g.

[0026] According to some embodiments of the method for preparing the coal tar pitch-based porous carbon described in the present application, the pore size distribution of the coal tar pitch-based porous carbon is 4-15 nm.

[0027] According to some embodiments of the method for preparing the coal tar pitch-based porous carbon described in the present application, the thermal stability of the coal tar pitch-based porous carbon is 600-700°C.

[0028] The second aspect of the present application provides a catalyst, comprising coal tar pitch-based porous carbon obtained by the preparation method described in the first aspect of the present application, and metal nanoparticles supported on the coal tar pitch-based porous carbon.

[0029] The porous carbon obtained by the preparation method described in the present application has a high specific surface area and good stability. When used as a catalyst carrier to prepare a fuel cell catalyst, the obtained catalyst has high catalytic activity and cyclic stability, and shows high electrocatalytic performance.

[0030] According to some embodiments of the catalyst described herein, the mass ratio of the coal tar pitch-based porous carbon to the metal nanoparticles is 5:(4-8).

[0031] According to some embodiments of the catalyst described herein, the metal nanoparticles are derived from one or more of chloroplatinic acid, chloroauric acid, chloroiridic acid, and ruthenium chloride.

[0032] In a third aspect of the present application, a working electrode is provided, wherein the working electrode comprises the catalyst described in the second aspect of the present application.

[0033] According to some embodiments of the working electrode described in this application, the catalyst loading on the working electrode is 10-200 μg / cm 2 .

[0034] The coal tar pitch-based porous carbon described in this application can be applied to fuel cells, electrochemistry and other aspects. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1a This is the N2 adsorption-desorption isotherm of the coal tar-based porous carbon prepared in Example 5;

[0036] Figure 1b This is the pore size distribution curve of the coal tar-based porous carbon prepared in Example 5;

[0037] Figure 2 This is a transmission electron micrograph of the coal tar-based porous carbon prepared in Example 1 of the present application;

[0038] Figure 3 This is a transmission electron micrograph of the coal tar-based porous carbon prepared in Example 2 of the present application;

[0039] Figure 4 This is a transmission electron micrograph of the coal tar-based porous carbon prepared in Example 3 of the present application;

[0040] Figure 5 This is a transmission electron micrograph of the coal tar-based porous carbon prepared in Example 4 of the present application;

[0041] Figure 6This is a transmission electron micrograph of the coal tar-based porous carbon prepared in Example 5 of the present application;

[0042] Figure 7 This is the infrared spectra of the coal tar-based porous carbon prepared in Example 1 and Comparative Example 1 of the present application;

[0043] Figure 8 The Raman spectra of the coal tar-based porous carbon prepared in Example 1 and Comparative Example 2 of the present application are shown;

[0044] Figure 9 This is a thermogravimetric analysis graph of the coal tar-based porous carbon prepared in Example 1 and Comparative Example 3 of the present application;

[0045] Figure 10 This is the X-ray diffraction spectrum of the coal tar-based porous carbon prepared in Examples 1-5 of the present application;

[0046] Figure 11 This is an SEM image of the coal tar-based porous carbon prepared in Example 2 of the present application;

[0047] Figure 12 This is an SEM image of the coal tar-based porous carbon prepared in Comparative Example 3 of this application;

[0048] Figure 13 The cyclic voltammetry curves of the working electrodes prepared from the coal tar pitch-based porous carbon described in Example 3 and Comparative Example 2 of the present application are shown respectively;

[0049] Figure 14 1 and 2 are polarization curves of the working electrodes prepared from the coal tar pitch-based porous carbon described in Example 3 and Comparative Example 2 of the present application, respectively. DETAILED DESCRIPTION

[0050] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0051] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0052] The present invention provides a method for preparing coal tar pitch-based porous carbon, comprising the following steps:

[0053] (1) subjecting the coal tar pitch to a first high-temperature thermal shock treatment in an air atmosphere to obtain pre-oxidized asphalt;

[0054] (2) subjecting the pre-oxidized asphalt to a second high-temperature thermal shock treatment in an inert atmosphere to obtain a pre-carbonized asphalt;

[0055] (3) The pre-carbonized asphalt and activator potassium hydroxide are mixed to obtain a mixed powder, and the mixed powder is subjected to a third high-temperature thermal shock treatment to obtain coal tar-based porous carbon.

[0056] The preparation method described in this application utilizes high-temperature thermal shock to pre-oxidize coal tar pitch, introduce oxygen-containing functional groups, increase the content of heteroatoms, and further promote the decomposition of polycyclic aromatic hydrocarbons into small molecules, so as to improve the subsequent activation of carbonized asphalt and increase the specific surface area of ​​coal tar pitch porous carbon.

[0057] Using high-temperature thermal shock to pre-carbonize pre-oxidized pitch promotes the polymerization of coal-tar pitch precursors and improves the carbon yield of the final product. During the high-temperature thermal shock activation process, the activator instantly melts into small droplets. The instantaneous Joule heating from the high-temperature rapid quench effectively creates a large number of pores with uniform size distribution in the coal-tar pitch, making it easier for the coal-tar pitch to interact with the activator, resulting in porous carbon with an ideal porous structure and high specific surface area. This method overcomes the problems of traditional methods, such as long activation time, high cost, large and uneven pore structure, and relatively low specific surface area.

[0058] The prepared porous carbon with high specific surface area is used as a support for fuel cell catalysts, has high catalytic activity and stability, and shows excellent electrochemical performance.

[0059] In some embodiments of the present application, the softening point of the coal tar pitch is 100-130°C, and the quinoline-insoluble matter in the coal tar pitch is less than 0.01%. The coal tar pitch is generally pulverized before pre-oxidation, that is, the coal tar pitch is placed in a crusher for crushing, and then the coal tar pitch is screened through a 100-mesh standard sieve.

[0060] In some embodiments of the present application, in step (1), the voltage of the first high-temperature thermal shock treatment is 350-400V; for example, 350V, 380V, 390V, 400V, etc., and the current of the first high-temperature thermal shock treatment is 25-35A; for example, 25A, 28A, 30A, 32A, 33A, 35A, etc.

[0061] The first high-temperature thermal shock treatment is to evenly spread the coal tar pitch on the carbon cloth electrode, connect the carbon cloth electrode loaded with coal tar pitch powder to a DC source with current pulses in an instantaneous electric heating device, and perform pre-oxidation treatment in an air atmosphere.

[0062] In some embodiments of the present application, the power of the first high-temperature thermal shock treatment is 18-25 kW, such as 18 kW, 20 kW, 22 kW, 25 kW, etc., and the duration of the first high-temperature thermal shock treatment is 5-15 seconds, such as 5 seconds, 8 seconds, 10 seconds, 12 seconds, 15 seconds, etc. Under these thermal shock conditions, the thermal shock temperature can be maintained in the range of 250-400° C., which is conducive to the decomposition of polycyclic aromatic hydrocarbons, ensures a moderate heteroatom content, and achieves a better pre-oxidation effect.

[0063] In some embodiments of the present application, in step (2), the voltage of the second high-temperature thermal shock treatment is 350-400V; for example, 350V, 380V, 390V, 400V, etc., and the current of the second high-temperature thermal shock treatment is 25-35A; for example, 25A, 28A, 30A, 32A, 33A, 35A, etc.

[0064] In some embodiments of the present application, the power of the second high-temperature thermal shock treatment is 28-32 kW, for example, 28 kW, 30 kW, 32 kW, etc., and the duration of the second high-temperature thermal shock treatment is 5-20 seconds, for example, 5 seconds, 10 seconds, 12 seconds, 15 seconds, 18 seconds, 20 seconds, etc. Within this power range, the thermal shock temperature can be controlled within the range of 450-650°C, which can improve the carbon yield of subsequent products and achieve the best pre-carbonization effect.

[0065] The second high-temperature thermal shock method is to evenly spread the pre-oxidized coal tar powder on the carbon cloth electrode, connect the carbon cloth electrode loaded with the pre-oxidized coal tar powder to a DC source with current pulses in an instantaneous electric heating device, and protect heating in a nitrogen range to perform pre-carbonization treatment.

[0066] In some embodiments of the present application, in step (3), the mass ratio of the pre-carbonized coal tar pitch to the activator is (1-4):1; for example, 4:1, 3:1, 2:1, 1:1, etc. The pre-carbonized coal tar pitch and the activator are uniformly mixed using a mixing vibration ball mill for 1-5 minutes, and then the mixed powder is evenly spread on a carbon cloth electrode. The carbon cloth electrode loaded with the mixed powder is connected to a DC source with a current pulse in an instantaneous electric heating device and protected and heated in a nitrogen atmosphere.

[0067] In some embodiments of the present application, the activator includes one or more of NaOH, K2CO3, Na2CO3, ZnCl2, KCl, NaCl and H3PO4.

[0068] In some embodiments of the present application, the voltage of the third high-temperature thermal shock treatment is 350-400V; for example, 350V, 380V, 390V, 400V, etc., and the current of the third high-temperature thermal shock treatment is 25-35A, for example, 25A, 28A, 30A, 32A, 33A, 35A, etc.

[0069] In some embodiments of the present application, the power of the third high-temperature thermal shock treatment is 40-48 kW, for example, 40 kW, 42 kW, 45 kW, 46 kW, 48 kW, etc., and the time of the third high-temperature thermal shock treatment is 10-30 s, for example, 10 s, 15 s, 18 s, 20 s, 22 s, 26 s, 28 s, 30 s, etc. Under this condition, the temperature of the thermal shock can be controlled in the range of 650-1000 ° C, which helps to improve the stability and specific surface area of ​​the product and achieve the best activation effect.

[0070] In some embodiments of the present application, the preparation method further comprises cleaning and drying the product after the third high-temperature thermal shock treatment.

[0071] In some embodiments of the present application, the cleaning is performed using hydrochloric acid and water in sequence.

[0072] In some embodiments of the present application, the concentration of the hydrochloric acid is 1-3 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L, etc.

[0073] In some embodiments of the present application, the cleaning is ultrasonic cleaning, and the cleaning time is 30-60 min, for example, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min, etc.

[0074] In some embodiments of the present application, the drying temperature is 50-70°C, for example, 50°C, 60°C, 65°C, 70°C, etc., and the drying time is 8-12h, for example, 8h, 10h, 11h, 12h, etc.

[0075] In some embodiments of the present application, the specific surface area of ​​the coal tar-based porous carbon is 1100-1200 m 2 / g; for example, 1100m 2 / g、1150m 2 / g、1180m 2 / g、1185m 2 / g、1120m 2 / g, etc.

[0076] In some embodiments of the present application, the pore volume of the coal tar-based porous carbon is 1.0-2.0 cm 3 / g; for example 1.0cm 3 / g, 1.2cm 3 / g, 1.22cm 3 / g, 1.28cm 3 / g, 1.83cm 3 / g, 1.89cm 3 / g, 2.0cm 3 / g, etc.

[0077] In some embodiments of the present application, the pore size distribution of the coal tar-based porous carbon is 4-15 nm; for example, 4 nm, 8 nm, 9 nm, 10 nm, 12 nm, 15 nm, etc.

[0078] In some embodiments of the present application, the thermal stability of the coal tar-based porous carbon is 600-700°C; for example, 600°C, 620°C, 650°C, 680°C, 690°C, 700°C, etc.

[0079] In a second aspect of the present application, a catalyst is provided, comprising a coal tar pitch-based porous carbon obtained by the preparation method described in the first aspect of the present application, and metal nanoparticles supported on the coal tar pitch-based porous carbon. The catalyst has an electrochemical active area of ​​165.8 m2 at 25°C in a three-electrode system with N2 saturated 0.1 mol / L HClO4 as the electrolyte, in a scanning range of -0.1 to 1.2 V, and a rate of 50 mV / s. 2 / g, current density at 0.9V: 4.41mA / cm 2 .

[0080] In some embodiments of the present application, 500 mg of the coal tar-based porous carbon (the coal tar-based porous carbon described in the first aspect of the present application) was weighed using an electronic balance and dispersed in an ethanol-water solution (the volume percentage of ethanol: 1%-30%), and a certain amount (mass percentage of 20%-80%, for example, 20%, 40%, 60%, 80%) of a noble metal precursor (such as chloroplatinic acid, chloroauric acid, chloroiridic acid, ruthenium chloride, etc.) was added, and the mixture was stirred and dissolved for 30 minutes;

[0081] (2) Add an excess of reducing agent (such as HCHO, HCOONa, Na2SO3, NH2NH2, NaBH4, etc.) and add 5%-15% of the mass of the aqueous solution of a charged surfactant (such as quaternary ammonium salt, PPh3, PVP, PVA, etc.) in the temperature range of 25-55°C; during the catalyst preparation process, the addition of a surfactant can effectively disperse the precious metal nanoparticles and increase the active specific surface area of ​​the catalyst.

[0082] (3) Under the assistance of ultrasonic waves of certain power (50W, 100W, 200W), the reduction reaction and the dispersion of raw materials were promoted to prepare a porous carbon@metal element catalyst slurry. After multiple centrifugal washings with deionized water and vacuum drying at 60°C for 8-12h, the catalyst was obtained.

[0083] In some embodiments of the present application, the mass ratio of the coal tar-based porous carbon to the metal compound is 5:(4-8); for example, 5:4, 5:5, 5:6, 5:7, 5:8, etc.

[0084] In some embodiments of the present application, the metal compound includes one or more of chloroplatinic acid, chloroauric acid, chloroiridic acid and ruthenium chloride.

[0085] An embodiment of the present application also provides a working electrode, which includes the catalyst described in the second aspect of the present application.

[0086] In some embodiments of the present application, the catalyst loading on the working electrode is 10-200 μg / cm 2 , for example 10 μg / cm 2 , 20μg / cm 2 , 50μg / cm 2 , 80μg / cm 2 , 100 μg / cm 2 , 120μg / cm 2 , 130μg / cm 2 , 160μg / cm 2 , 180μg / cm 2 , 200 μg / cm 2 wait.

[0087] The porous carbon obtained by the preparation method described in the present application has a high specific surface area and good stability. When used as a catalyst carrier to prepare a fuel cell catalyst, the obtained catalyst has high catalytic activity and cyclic stability, and shows high electrocatalytic performance.

[0088] In some embodiments of the present application, 5 mg of the catalyst described in the second aspect of the present application was accurately weighed, and 5-20 μl of 5% Nafion solution, ultrapure water, and isopropanol were added to the catalyst in sequence, and then ultrasonicated with an ultrasonic power greater than 200 W for 30 minutes to fully mix the slurry. During the ultrasonication process, the water bath temperature was kept below 20°C.

[0089] The catalyst loading range of the electrode surface is 10-200 μg / cm 2 , take an appropriate amount of the dispersed slurry and evenly apply it twice to the smooth and clean surface of the disk electrode, let it dry completely naturally, and use it as the working electrode.

[0090] The technical solution of this application is described in detail below with reference to specific embodiments and drawings.

[0091] Example 1

[0092] A method for preparing coal tar pitch-based porous carbon comprises the following steps:

[0093] (1) Weigh 100 g of refined deashed asphalt after coal liquefaction (softening point 130°C, quinoline insoluble matter <0.01%, obtained from China Shenhua Coal to Liquid Chemical Co., Ltd.) and crush it with a crusher for 10 min; then sieve the coal tar pitch powder with a 100-mesh standard sieve, weigh 10 g of the sieved asphalt powder, and further grind it with an agate mortar; evenly spread the ground coal tar pitch powder on a carbon cloth electrode, connect the carbon cloth loaded with coal tar pitch powder to a DC source with a current pulse in an instantaneous electric heating device, adjust the voltage so that the power of the first high-temperature thermal shock treatment is 18 kW, and heat it for 10 s under this power and air atmosphere to obtain pre-oxidized asphalt;

[0094] (2) Pre-oxidized coal tar pitch powder was evenly spread on a carbon cloth electrode, and the carbon cloth loaded with coal tar pitch powder was connected to a DC source with a current pulse in an instantaneous electric heating device. The voltage was adjusted so that the power of the second high-temperature thermal shock treatment was 28 kW. The carbon cloth was heated for 10 s at this power and in a nitrogen atmosphere to obtain pre-carbonized asphalt.

[0095] (3) Pre-carbonized coal tar and potassium hydroxide powder were uniformly mixed in a mass ratio of 2:1 using a mixed vibration ball mill for 3 minutes; the mixed powder was evenly spread on a carbon cloth electrode, and the carbon cloth loaded with the mixed powder was connected to a DC source with a current pulse in an instantaneous electric heating device. The voltage was adjusted so that the power of the third high-temperature thermal shock treatment was 40 kW, and the material was heated for 20 seconds under this power and nitrogen atmosphere; then the material obtained by the third high-temperature thermal shock treatment was ultrasonically cleaned with 2 mol / L HCl and deionized water in turn, and the cleaned material was vacuum dried at 60°C for 12 hours to obtain coal tar-based porous carbon.

[0096] Example 2

[0097] The only difference between the preparation method of the coal tar-based porous carbon described in Example 2 and that of Example 1 is that the time of the first high-temperature thermal shock treatment in the preparation method of the coal tar-based porous carbon described in Example 2 is 15 seconds (the carbon cloth loaded with coal tar powder is connected to a DC source with current pulses in an instantaneous electric heating device for 15 seconds).

[0098] Example 3

[0099] The only difference between the preparation method of the coal tar-based porous carbon described in Example 3 and that of Example 1 is that the time of the second high-temperature thermal shock treatment in the preparation method of the coal tar-based porous carbon described in Example 3 is 20 seconds (the carbon cloth loaded with pre-oxidized coal tar powder is connected to a DC source with current pulses in an instantaneous electric heating device for 20 seconds).

[0100] Example 4

[0101] The only difference between the preparation method of the coal tar pitch-based porous carbon described in Example 4 and that of Example 1 is that the time of the third high-temperature thermal shock treatment in the preparation method of the coal tar pitch-based porous carbon described in Example 4 is 10 seconds (the carbon cloth loaded with the mixed powder is connected to a DC source with a current pulse in an instantaneous electric heating device for 10 seconds).

[0102] Example 5

[0103] The only difference between the method for preparing the coal tar pitch-based porous carbon described in Example 5 and that in Example 1 is that the power of the third high-temperature thermal shock treatment in the method for preparing the coal tar pitch-based porous carbon described in Example 5 is 50 KW.

[0104] Comparative Example 1

[0105] The only difference between the preparation method of the coal tar pitch-based porous carbon described in Comparative Example 1 and Example 1 is that the preparation method of the coal tar pitch-based porous carbon described in Comparative Example 1 does not pre-oxidize the coal tar pitch, but directly pre-carbonizes the coal tar pitch in an inert atmosphere.

[0106] Comparative Example 2

[0107] The only difference between the preparation method of the coal tar pitch-based porous carbon described in Comparative Example 2 and that of Example 1 is that the preparation method of the coal tar pitch-based porous carbon described in Comparative Example 2 does not perform pre-carbonization treatment of the coal tar pitch, that is, pre-oxidized coal tar pitch and an activator are mixed to obtain a mixed powder, and the mixed powder is subjected to a third high-temperature thermal shock treatment to obtain coal tar pitch-based porous carbon.

[0108] Comparative Example 3

[0109] The only difference between the preparation method of the coal tar pitch-based porous carbon described in Comparative Example 3 and that in Example 1 is that the preparation method of the coal tar pitch-based porous carbon described in Comparative Example 3 does not pre-oxidize, carbonize, and activate the coal tar pitch through a high-temperature thermal shock process.

[0110] The specific operation is as follows: grind and mix coal tar and KOH in a mass ratio of 2:1, place the mixed powder in a high-temperature tube furnace for carbonization treatment, and carry out the treatment in a nitrogen atmosphere with a nitrogen flow rate of 50 mL / min, a carbonization treatment temperature of 1000°C, a heating rate of 10°C / min, and a carbonization time of 3 h.

[0111] 1. The physical properties of the coal tar pitch-based porous carbon obtained by the preparation methods described in Examples 1-5 and Comparative Examples 1-3 of the present application are shown in Table 1:

[0112] The N2 adsorption-desorption isotherm and pore size distribution of the coal tar-based porous carbon of Example 5 and Comparative Example 3 were measured by BET adsorption method. Figure 1a and Figure 1b shown.

[0113] Table 1

[0114]

[0115] Note: The specific surface area, pore volume and pore size distribution described in this application were determined using the BET adsorption method.

[0116] The stability described in this application was obtained by thermogravimetric testing. An appropriate amount of sample was weighed and placed in a test crucible of a thermogravimetric analyzer with nitrogen as the working gas. The sample was heated from room temperature to an end point temperature of 800°C at a heating rate of 10°C / min, and the sample temperature-mass curve was recorded.

[0117] The carbon yield described in this application is the mass ratio of coal tar pitch before and after high-temperature thermal shock pre-oxidation, carbonization and activation treatment.

[0118] From Table 1, Figure 1a and Figure 1b It can be seen that the heating power and time during high-temperature thermal shock treatment have an impact on the specific surface area, pore volume, pore size distribution and stability of coal tar-based porous carbon.

[0119] From the comparison of the sample data of Example 1 and Comparative Example 1, it can be seen that the specific surface area and pore volume of the coal tar-based porous carbon can be significantly improved through high-temperature thermal shock pre-oxidation treatment, and the pore size distribution can be precisely controlled, because the pre-oxidation treatment can effectively decompose polycyclic aromatic hydrocarbons and introduce heteroatoms and oxygen-containing functional groups.

[0120] From the comparison of the sample data of Example 1 and Comparative Example 2, it can be seen that the thermal stability and carbon yield of the coal base can be significantly improved by high-temperature thermal shock pre-carbonization treatment, and a product with better property parameters can be obtained.

[0121] From the comparison of the sample data of Example 1 and Comparative Example 3, it can be seen that compared with the traditional carbon activation method, the product obtained by the high-temperature thermal shock method has obvious advantages, such as easy operation, short process and high product performance.

[0122] 2. The high-magnification transmission electron microscopy images of the coal tar pitch-based porous carbon prepared in Examples 1-5 of the present application are as follows: Figure 2-6 shown.

[0123] from Figure 2-6As can be seen from the results, the coal-tar-based porous carbon has a distinct porous structure, but the specific morphology and structure of the porous carbon samples vary with different process parameters. Experimental results show that Example 1 has the most optimal property parameters because the high-temperature thermal shock pre-oxidation and carbonization treatment time in Example 1 is moderate, which not only achieves the introduction of heteroatoms but also improves the stability of the sample, achieving the best pretreatment effect. The sample obtains the optimal specific surface area and pore volume, and the pore size distribution is precisely controlled.

[0124] 3. The infrared spectra of the coal tar-based porous carbon prepared in Example 1 and Comparative Example 1 of the present application are as follows: Figure 7 shown.

[0125] from Figure 7 It can be seen that the coal tar pitch-based porous carbon prepared by the preparation method of the present application contains atomic functional groups such as C, S, N, and O. The sample of Example 1 after pre-oxidation treatment has a carbon density of 800-900 cm -1 The wavelength range has obvious CO functional group characteristic peaks, while the sample of Comparative Example 1 does not have obvious CO functional group characteristic peaks. Therefore, the pre-oxidation treatment has the effect of decomposing polycyclic aromatic hydrocarbons and introducing heteroatoms and oxygen-containing functional groups.

[0126] 4. The Raman spectra of the coal tar pitch based porous carbon prepared in Example 1 and Comparative Example 2 of the present application are shown in FIG. Figure 8 shown.

[0127] from Figure 8 It can be seen that the coal tar pitch based porous carbon prepared in Example 1 of the present application has a -1 and 1590cm -1 There are two typical carbon characteristic peaks nearby, namely D peak representing defect structure and G peak representing ordered structure. I D / I G , Example 1 sample I D / I G is 1.22, while the I of the sample of Comparative Example 1 is D / I G The value of γ is 1.41, indicating that the sample of Example 1 has a higher degree of graphitization. Therefore, high-temperature thermal shock pre-carbonization treatment can significantly improve the thermal stability of coal-based materials and improve the degree of graphitization of porous carbon.

[0128] 5. The thermal gravimetric analysis curves of the coal tar pitch based porous carbon prepared in Example 1 and Comparative Example 3 of the present application are as follows: Figure 9 shown.

[0129] from Figure 9It can be seen that the coal tar-based porous carbon prepared in Example 1 of the present application has higher thermal stability, wherein the thermal decomposition temperature of the sample in Example 1 is 685°C, and the thermal decomposition temperature of the sample in Comparative Example 1 is 435°C.

[0130] 6. The X-ray diffraction spectra of the coal tar-based porous carbon prepared in Examples 1-5 of the present application are as follows: Figure 10 shown.

[0131] from Figure 10 It can be seen that the coal tar-based porous carbon samples all have carbon characteristic diffraction peaks near 2θ of 23° and 44°, which correspond to the 002 diffraction peak of the aromatic sheet stacking orientation and the 100 diffraction peak of the aromatic sheet size, respectively.

[0132] 7. The SEM images of the coal tar-based porous carbon prepared in Example 2 and Comparative Example 3 of the present application are as follows: Figure 11 and Figure 12 shown.

[0133] from Figure 11 and Figure 12 As can be seen from the figure, the surface morphology of the coal-tar pitch-based porous carbon prepared by the high-temperature thermal shock method is more uniform and regular, while the porous carbon prepared by the traditional method has a wider pore structure distribution and a rough, non-smooth surface. Therefore, the coal-tar pitch-based porous carbon prepared by the high-temperature thermal shock method has a higher specific surface area.

[0134] Example 6

[0135] A method for preparing a working electrode comprises the following steps:

[0136] (1) 500 mg of the coal tar-based porous carbon prepared in Example 3 of the present application was dispersed in 20 mL of a 10% ethanol-water solution, and 60% chloroplatinic acid in an aqueous solution was added to the aqueous solution, stirred and dissolved, and mixed for 30 minutes; while maintaining the temperature at 25° C., an excess of NaBH4 was added as a reducing agent, and 5% quaternary ammonium salt dodecyl ammonium chloride in an aqueous solution was added as a surfactant; a reduction reaction was carried out under the assistance of ultrasonic waves at a power of 200 W to obtain a porous carbon@Pt catalyst; the catalyst was washed by centrifugation with deionized water and dried in vacuo at 60° C. for 12 hours to obtain a catalyst;

[0137] (2) Weigh 5 mg of the above catalyst, add 50 μl of 5% Nafion solution, 2 mL of ultrapure water, and 2 mL of isopropanol to the catalyst in sequence, and then use ultrasonic treatment with a power of 300 W for 30 min to mix the slurry evenly. During the ultrasonic process, keep the water bath temperature below 20 ° C; according to the catalyst loading on the electrode surface of 30 μg / cm 2Take an appropriate amount of the dispersed slurry and evenly apply it to the smooth and clean surface of the disk electrode twice. Place it in a moisture-proof cabinet and dry it completely to serve as the working electrode.

[0138] Comparative Example 4

[0139] The preparation method of the working electrode described in Comparative Example 4 is different from that of Example 6 only in that the coal tar pitch-based porous carbon prepared in Comparative Example 2 is used instead of the coal tar pitch-based porous carbon prepared in Example 3.

[0140] Performance study of the working electrode described in this application:

[0141] 1. Research method: High-purity N2 (99.99%) was introduced into a 0.1 mol / L HClO4 aqueous solution and purged for at least 30 minutes to remove the dissolved oxygen in the solution. Then, in a three-electrode system, a thin film electrode was used as the working electrode (the working electrode prepared by Example 6 of the present application and the working electrode prepared by Comparative Example 4 of the present application), a saturated calomel electrode was used as the reference electrode, a Pt sheet was used as the counter electrode, and the electrolyte was a 0.1 mol / L HClO4 solution saturated with N2. Cyclic voltammetry curve test was performed at 25°C. The catalyst was first activated at a scan rate of 100 mV / s, and the catalyst surface was cleaned until the hydrogen desorption peak area no longer increased. At 0-1.2 V (relative to the reversible hydrogen electrode, V RHE ) Under the potential scanning range, scan 5 times at a speed of 50mV / s and record the cyclic voltammetry curve at this time. The results are as follows Figure 13 shown.

[0142] from Figure 13 It can be seen that the working electrode described in Example 6 of the present application has obvious redox catalytic performance, and the catalytic performance is significantly better than that of the working electrode described in Comparative Example 4, and has a higher electrochemical active area.

[0143] 2. At 25°C, in a three-electrode system, O2-saturated 0.1 mol / L HClO4 was used as the electrolyte, the ring electrode rotated at 1500 r / min, and the voltage was between 0 and 1.0 V. RHE Under the potential scanning range, the forward scanning was performed at a rate of 10 mV / s, and the polarization curves of the working electrodes (the working electrodes prepared in Example 6 of the present application and the working electrodes prepared in Comparative Example 4 of the present application) were recorded. The results are shown in FIG. Figure 14 shown.

[0144] from Figure 14 It can be seen that the working electrode prepared in Example 6 of the present application has a RHE There is a higher current density between them.

[0145] Although the above embodiments have been shown and described, it is understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. Changes, modifications, substitutions and variations of the above embodiments by those skilled in the art are all within the scope of protection of the present invention.

Claims

1. A method for preparing coal tar pitch-based porous carbon, characterized in that: The following steps are involved: (1) subjecting the coal tar pitch to a first high-temperature thermal shock treatment in an air atmosphere to obtain pre-oxidized asphalt; (2) subjecting the pre-oxidized asphalt to a second high-temperature thermal shock treatment in an inert atmosphere to obtain a pre-carbonized asphalt; (3) The pre-carbonized asphalt and the activator are mixed to obtain a mixed powder, and the mixed powder is subjected to a third high-temperature thermal shock treatment to obtain coal tar-based porous carbon.

2. The method for preparing coal tar pitch-based porous carbon according to claim 1, characterized in that: In step (1), the voltage of the first high-temperature thermal shock treatment is 350-400V; the current of the first high-temperature thermal shock treatment is 25-35A; And / or, the power of the first high-temperature thermal shock treatment is 18-25 kW, and the time of the first high-temperature thermal shock treatment is 5-15 s.

3. The method for preparing coal tar pitch-based porous carbon according to claim 1, wherein: In step (2), the voltage of the second high-temperature thermal shock treatment is 350-400V; the current of the second high-temperature thermal shock treatment is 25-35A; And / or, the power of the second high-temperature thermal shock treatment is 28-32 kW, and the time of the second high-temperature thermal shock treatment is 5-20 s.

4. The method for preparing coal tar pitch-based porous carbon according to claim 1, wherein: In step (3), the mass ratio of the pre-carbonized asphalt to the activator is (1-4):1; and / or, the activator comprises one or more of NaOH, K2CO3, Na2CO3, ZnCl2, KCl, NaCl and H3PO4; And / or, the voltage of the third high-temperature thermal shock treatment is 350-400V; the current of the third high-temperature thermal shock treatment is 25-35A; And / or, the power of the third high-temperature thermal shock treatment is 40-48 kW, and the time of the third high-temperature thermal shock treatment is 10-30 s.

5. The method for preparing coal tar pitch-based porous carbon according to claim 1, wherein: The preparation method further comprises cleaning and drying the product after the third high-temperature thermal shock treatment.

6. The method for preparing coal tar pitch-based porous carbon according to claim 5, characterized in that: The cleaning is carried out by sequentially using hydrochloric acid and water.

7. The method for preparing coal tar pitch-based porous carbon according to claim 6, characterized in that: The concentration of the hydrochloric acid is 1-3 mol / L.

8. The method for preparing coal tar pitch-based porous carbon according to claim 5, characterized in that: The cleaning is ultrasonic cleaning, and the cleaning time is 30-60 minutes.

9. The method for preparing coal tar pitch-based porous carbon according to claim 5, wherein: The drying temperature is 50-70° C., and the drying time is 8-12 hours.

10. The method for preparing coal tar pitch-based porous carbon according to claim 1, wherein: The specific surface area of ​​the coal tar-based porous carbon is 1100-1200m 2 / g; And / or, the pore volume of the coal tar-based porous carbon is 1.0-2.0 cm 3 / g; and / or, the pore size distribution of the coal tar pitch-based porous carbon is 4-15 nm; And / or, the thermal stability of the coal tar pitch-based porous carbon is 600-700°C.

11. A catalyst, characterized in that The invention comprises coal tar pitch-based porous carbon obtained by the preparation method according to any one of claims 1 to 10, and metal nanoparticles supported on the coal tar pitch-based porous carbon.

12. The catalyst according to claim 11, characterized in that The mass ratio of the coal tar pitch-based porous carbon to the metal nanoparticles is 5:(4-8); And / or, the metal nanoparticles are derived from one or more of chloroplatinic acid, chloroauric acid, chloroiridic acid and ruthenium chloride.

13. A working electrode, characterized in that The working electrode comprises the catalyst according to any one of claims 11-12.

14. The working electrode according to claim 13, characterized in that The catalyst loading on the working electrode is 10-200 μg / cm 2 .

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