CN116705517A - Porous carbon prepared from lignite as raw material and preparation method and application thereof - Google Patents
Porous carbon prepared from lignite as raw material and preparation method and application thereof Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 84
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 82
- 239000003077 lignite Substances 0.000 title claims abstract description 46
- 238000002360 preparation method Methods 0.000 title claims abstract description 17
- 239000002994 raw material Substances 0.000 title claims abstract description 11
- 238000010438 heat treatment Methods 0.000 claims abstract description 48
- 238000000197 pyrolysis Methods 0.000 claims abstract description 36
- 239000007772 electrode material Substances 0.000 claims abstract description 29
- 239000011148 porous material Substances 0.000 claims abstract description 28
- 239000012670 alkaline solution Substances 0.000 claims abstract description 17
- 238000002156 mixing Methods 0.000 claims abstract description 17
- 238000010669 acid-base reaction Methods 0.000 claims abstract description 13
- 230000003213 activating effect Effects 0.000 claims abstract description 10
- 239000003795 chemical substances by application Substances 0.000 claims abstract description 10
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 33
- 239000000243 solution Substances 0.000 claims description 30
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 22
- 238000000034 method Methods 0.000 claims description 19
- 239000012190 activator Substances 0.000 claims description 12
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 11
- 230000001105 regulatory effect Effects 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 2
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical group OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims 1
- 239000003990 capacitor Substances 0.000 abstract description 15
- 238000000498 ball milling Methods 0.000 description 22
- 239000000047 product Substances 0.000 description 19
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 11
- 238000001035 drying Methods 0.000 description 11
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical group [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 10
- QJZYHAIUNVAGQP-UHFFFAOYSA-N 3-nitrobicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid Chemical compound C1C2C=CC1C(C(=O)O)C2(C(O)=O)[N+]([O-])=O QJZYHAIUNVAGQP-UHFFFAOYSA-N 0.000 description 9
- 238000009826 distribution Methods 0.000 description 9
- 238000005119 centrifugation Methods 0.000 description 8
- 238000001816 cooling Methods 0.000 description 8
- 239000004021 humic acid Substances 0.000 description 8
- 239000003575 carbonaceous material Substances 0.000 description 7
- 238000011282 treatment Methods 0.000 description 7
- 238000003756 stirring Methods 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 239000002253 acid Substances 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- 238000001291 vacuum drying Methods 0.000 description 5
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 4
- 238000010306 acid treatment Methods 0.000 description 4
- 125000003118 aryl group Chemical group 0.000 description 4
- 239000012298 atmosphere Substances 0.000 description 4
- 239000007833 carbon precursor Substances 0.000 description 4
- 238000000227 grinding Methods 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- 239000011734 sodium Substances 0.000 description 4
- 229910052708 sodium Inorganic materials 0.000 description 4
- 238000005406 washing Methods 0.000 description 4
- IRXRGVFLQOSHOH-UHFFFAOYSA-L dipotassium;oxalate Chemical compound [K+].[K+].[O-]C(=O)C([O-])=O IRXRGVFLQOSHOH-UHFFFAOYSA-L 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 239000011812 mixed powder Substances 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 230000020477 pH reduction Effects 0.000 description 3
- 239000012264 purified product Substances 0.000 description 3
- 239000007790 solid phase Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000006230 acetylene black Substances 0.000 description 2
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 2
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 229910052593 corundum Inorganic materials 0.000 description 2
- 239000010431 corundum Substances 0.000 description 2
- 238000003795 desorption Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 125000000956 methoxy group Chemical group [H]C([H])([H])O* 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 150000003891 oxalate salts Chemical group 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000000746 purification Methods 0.000 description 2
- -1 quinoyl Chemical group 0.000 description 2
- 238000006479 redox reaction Methods 0.000 description 2
- 239000002002 slurry Substances 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000006978 adaptation Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 229940062993 ferrous oxalate Drugs 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- OWZIYWAUNZMLRT-UHFFFAOYSA-L iron(2+);oxalate Chemical compound [Fe+2].[O-]C(=O)C([O-])=O OWZIYWAUNZMLRT-UHFFFAOYSA-L 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 231100000053 low toxicity Toxicity 0.000 description 1
- 229920002521 macromolecule Polymers 0.000 description 1
- UHNWOJJPXCYKCG-UHFFFAOYSA-L magnesium oxalate Chemical compound [Mg+2].[O-]C(=O)C([O-])=O UHNWOJJPXCYKCG-UHFFFAOYSA-L 0.000 description 1
- 238000003760 magnetic stirring Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000011232 storage material Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/32—Carbon-based
- H01G11/44—Raw materials therefor, e.g. resins or coal
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/24—Electrodes characterised by structural features of the materials making up or comprised in the electrodes, e.g. form, surface area or porosity; characterised by the structural features of powders or particles used therefor
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
- H01G11/22—Electrodes
- H01G11/30—Electrodes characterised by their material
- H01G11/32—Carbon-based
- H01G11/34—Carbon-based characterised by carbonisation or activation of carbon
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/13—Energy storage using capacitors
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Carbon And Carbon Compounds (AREA)
Abstract
The invention provides porous carbon prepared from lignite as a raw material, and a preparation method and application thereof, and belongs to the technical field of supercapacitors. The preparation method of the porous carbon prepared by taking lignite as a raw material provided by the invention comprises the following steps: (1) Mixing lignite with an alkaline solution, and heating to perform an acid-base reaction to obtain humate; (2) And (3) mixing the humate obtained in the step (1) with an activating agent, and then performing pyrolysis to obtain the porous carbon. The average pore diameter of the porous carbon prepared by the preparation method provided by the invention is distributed at about 0.5nm, and the porous carbon has a microporous structure; when the porous carbon is used as the electrode material of the super capacitor, the porous carbon has high specific capacitance, high energy density and high power density, and can be applied to the field of the electrode material of the super capacitor.
Description
Technical Field
The invention relates to the technical field of super capacitors, in particular to porous carbon prepared from lignite as a raw material, and a preparation method and application thereof.
Background
The super capacitor is used as a novel energy storage material, has the advantages of high charge and discharge rate, long cycle life and the like, and the carbon-based material is a natural and available raw material due to good conductivity, high specific surface area and high stability, and is an important source of the electrode material of the super capacitor.
The brown coal in China is rich in reserves, but the direct utilization rate is not high due to low degree of coalification of the brown coal, ash content in the brown coal is high, and impurities are more, so that the brown coal is often low in specific capacitance and energy density when the brown coal is used for preparing the electrode material of the supercapacitor. Lignite contains a large amount of humic acid, which is an organic macromolecule rich in various oxygen functional groups and can be used for preparing supercapacitor electrode materials. However, the current use of humic acid in lignite to produce high-performance porous carbon materials is still under investigation.
Therefore, how to use lignite as a raw material to prepare porous carbon applicable to supercapacitor electrodes and enable electrode materials prepared from the porous carbon to have high specific capacitance, high energy density and high power density is a technical problem to be solved in the art.
Disclosure of Invention
The invention aims to provide a preparation method and application of porous carbon prepared from lignite. The porous carbon prepared by the preparation method of the porous carbon prepared by taking lignite as a raw material is of a sub-nano pore structure, and the electrode prepared by adopting the porous carbon has high specific capacitance, high energy density and high power density, and can be applied to the field of super capacitor electrode materials.
In order to achieve the above object, the present invention provides the following technical solutions:
the invention provides a preparation method of porous carbon prepared from lignite, which comprises the following steps:
(1) Mixing lignite with an alkaline solution, and heating to perform an acid-base reaction to obtain humate;
(2) And (3) mixing the humate obtained in the step (1) with an activating agent, and then performing pyrolysis to obtain the porous carbon.
Preferably, the alkaline solution in the step (1) is a mixed solution of sodium carbonate solution and sodium hydroxide solution.
Preferably, the volume ratio of the lignite mass in the step (1) to the sodium carbonate solution and the sodium hydroxide solution is 1g: (1-2.5) mL: (1-2.5) mL.
Preferably, the concentration of the sodium carbonate solution and the sodium hydroxide solution is independently 1-2 mol/L.
Preferably, the heating in the step (1) includes the steps of:
(a) Mixing lignite with an alkaline solution and then carrying out first heating to obtain a product 1;
(b) Regulating the pH value of the product 1 obtained in the step (a) to 11-12, and then performing second heating to obtain humate;
the temperature of the first heating in the step (a) and the second heating in the step (b) is independently 75-85 ℃, and the time of the first heating and the second heating is independently 60-180 min.
Preferably, in the step (2), the mass ratio of the humate to the activator is 1: (1-3).
Preferably, the activator is an oxalate.
Preferably, the pyrolysis temperature in the step (2) is 700-900 ℃, and the pyrolysis time is 2-3 h.
The invention provides the porous carbon prepared by the preparation method of the technical scheme, and the porous carbon has a sub-nano pore structure.
The invention provides application of the porous carbon in the super capacitor electrode material.
The invention provides a preparation method of porous carbon prepared from lignite, which comprises the following steps: (1) Mixing lignite with an alkaline solution, and heating to perform an acid-base reaction to obtain humate; (2) And (3) mixing the humate obtained in the step (1) with an activating agent, and then performing pyrolysis to obtain the porous carbon. The invention adopts brown coal as raw material, utilizes organic macromolecular humic acid containing rich oxygen functional groups (carboxyl, hydroxyl, carbonyl, quinoyl, methoxy and the like) in brown coal, and prepares porous carbon with sub-nano pore structure by acid-base reaction to obtain humate, and takes the humate as carbon precursor; during the pyrolysis of humate and activator, the oxygen content in humate is due toHigher, the CO generated at lower temperature is oxidized into CO by oxygen functional groups contained in humates 2 ，CO 2 The method has the physical pore-forming function, so that the effect of regulating and controlling pore structures is realized at a lower temperature, and the pyrolysis temperature is reduced; on the other hand, as the non-carbon element is eliminated at high temperature, the carbon precursor is condensed into an aromatic skeleton, and then the aromatic skeleton is etched through oxidation-reduction reaction with an activator to form a porous structure, so that the prepared porous carbon has a sub-nano pore structure, presents a large specific surface area and good pore structure distribution, and when used as an electrode material of a supercapacitor, the porous carbon has high specific capacitance, and due to the existence of oxygen functional groups, the pseudo-capacitance characteristic of the supercapacitor in the electrochemical process can effectively widen a voltage window to increase the energy density of the supercapacitor. Experimental results show that the porous carbon prepared by the preparation method provided by the invention has average pore diameter distribution of about 0.5nm and is of a microporous structure; when the porous carbon is used as the electrode material of the super capacitor, the current density is 1 A.g -1 When the mass specific capacitance is 252-302 F.g -1 The method comprises the steps of carrying out a first treatment on the surface of the At a power density of 550 W.kg -1 The energy density is 20-31.8 Wh.kg -1 At a power density of 22000 W.kg -1 When the energy density is 9.8 to 17.7Wh.kg -1 Has high specific capacitance, high energy density and high power density, can be applied to the field of super capacitor electrode materials.
Drawings
FIG. 1 is an SEM image of porous carbon of sub-nano-pore structure prepared in example 1 of the present invention;
FIG. 2 is N of porous carbon of sub-nano pore structure prepared in example 1 of the present invention 2 Adsorption and desorption isothermal curves;
FIG. 3 is a graph showing pore size distribution of a porous carbon material having a sub-nano pore structure prepared in example 1 of the present invention;
FIG. 4 shows the current density of 1 A.g in a three-electrode system using the porous carbon prepared in examples 1 and 2 of the present invention as an electrode material for a supercapacitor -1 Constant current charge-discharge (GCD) curve;
FIG. 5 shows the preparation of the polymers according to examples 1 and 2 of the inventionThe current density of the porous carbon serving as the electrode material of the super capacitor is 0.5-20A.g under a three-electrode system -1 The mass ratio capacitance measured is measured;
FIG. 6 is a drawing showing the results of measuring the porous carbon prepared in examples 1 and 2 of the present invention as an electrode material for a supercapacitor in a double electrode system;
fig. 7 is a cycle curve of the porous carbon prepared in example 1 of the present invention as an electrode material for a supercapacitor.
Detailed Description
The invention provides a preparation method of porous carbon prepared from lignite, which comprises the following steps:
(1) Mixing lignite with an alkaline solution, and heating to perform an acid-base reaction to obtain humate;
(2) And (3) mixing the humate obtained in the step (1) with an activating agent, and then performing pyrolysis to obtain the porous carbon.
The invention mixes lignite with alkaline solution and then heats to perform acid-base reaction to obtain humate.
In the present invention, the lignite particle size is preferably <0.15mm, more preferably <0.074mm. The particle size of the lignite is set within the range, so that humic acid in the lignite can be extracted more fully.
In the present invention, the alkaline solution is preferably a mixed solution of sodium carbonate solution and sodium hydroxide solution; the concentration of the sodium carbonate solution and the sodium hydroxide solution is preferably independently 1 to 2mol/L, more preferably 1 to 1.5mol/L, and still more preferably 1mol/L. The invention can improve the yield of humate by setting the type and concentration of the alkaline solution in the above range.
In the present invention, the volume ratio of the mass of lignite to the sodium carbonate solution and sodium hydroxide solution is preferably 1g: (1-2.5) mL: (1 to 2.5) mL, more preferably 1g: (1-1.5) mL: (1 to 1.5) mL, more preferably 1g:1mL:1mL. The invention limits the mass of the lignite to the volume ratio of the sodium carbonate solution and the sodium hydroxide solution to the above range, so that humic acid in the lignite can be fully extracted, and the yield of the humic acid is improved.
In the present invention, the heating preferably includes the steps of:
(a) Mixing lignite with an alkaline solution and then carrying out first heating to obtain a product 1;
(b) Regulating the pH value of the product 1 obtained in the step (a) to 11-12, and then performing second heating to obtain humate;
the temperature of the first heating in the step (a) and the second heating in the step (b) is independently 75-85 ℃, and the time of the first heating and the second heating is independently 60-180 min.
In the invention, the lignite is preferably mixed with an alkaline solution and then subjected to first heating, so that a product 1 is obtained.
In the present invention, the temperature of the first heating is preferably 75 to 85 ℃, more preferably 80 ℃; the time of the first heating is preferably 60 to 180 minutes, more preferably 120 minutes. The invention sets the temperature and time of the first heating to be in the above range, so that the lignite and the alkaline solution can be fully mixed and subjected to preliminary acid-base reaction.
After the product 1 is obtained, the pH of the product 1 is preferably adjusted to 11-12, and then the second heating is carried out to obtain the humate.
The invention preferably uses deionized water to adjust the pH of the product 1 to 11-12. According to the invention, the pH value of the product 1 is regulated to 11-12, so that humic acid in lignite can be fully dissolved in alkaline solution, and the yield of humic acid salt is improved.
In the present invention, the temperature of the second heating is preferably 75 to 85 ℃, more preferably 80 ℃; the time of the second heating is preferably 60 to 180 minutes, more preferably 120 minutes. The invention sets the temperature and time of the second heating to be in the above range, so that the lignite and the alkaline solution can be fully reacted to obtain humate.
In the invention, the heating modes of the first heating and the second heating are preferably constant-temperature water bath heating. The invention can ensure the uniformity of the temperature of the reaction system by heating in a constant-temperature water bath.
The invention can make the acid-base reaction more sufficient and make the humate have higher productivity by setting the heating to the first heating and the second heating.
After the acid-base reaction is finished, the invention preferably carries out cooling and centrifugation on the mixture obtained by the acid-base reaction in sequence to obtain the extracting solution.
The mode and operation of the cooling in the present invention are not particularly limited, and the temperature of the mixture may be cooled to room temperature.
The centrifugation operation is not particularly limited, and the liquid and the solid in the mixture obtained by the acid-base reaction can be separated.
After the extracting solution is obtained, the extracting solution is preferably subjected to acidification treatment, centrifugation, drying and grinding in sequence to obtain the humate.
In the present invention, the acid used for the acidification treatment is preferably any one of hydrochloric acid, nitric acid and sulfuric acid; the concentration of the acid is preferably 1mol/L. In the present invention, humate in the extract can be precipitated by acidification treatment. The amount of the acid to be added in the present invention is not particularly limited, and the pH of the extract may be adjusted to 1 to 2.
In the present invention, the rotational speed of the centrifugation is preferably 7500 to 8500r/min, more preferably 8000r/min. The invention has no special limitation on the centrifugation time, and can separate out the settled humate.
In the present invention, the drying is preferably performed in a vacuum drying oven; the temperature of the drying is preferably 80 ℃, and the time of the drying is preferably 48 hours. The present invention can make humate remove water better by setting the drying temperature and time to the above range.
The method has no special requirement on grinding, and the dried and agglomerated humate can be ground into powder.
After the humate is obtained, the humate and the activating agent are mixed and pyrolyzed to obtain the porous carbon.
In the invention, the mass ratio of the humate to the activator is preferably 1: (1 to 3), more preferably 1:2. the mass ratio of the humate to the activating agent is limited to be within the range, so that the humate and the activating agent can better react, the pore structure can be regulated and controlled, and the porous carbon with good pore structure distribution is obtained.
In the present invention, the activator is preferably oxalate, more preferably one of potassium oxalate, ferrous oxalate and magnesium oxalate. The invention limits the types of the activating agents to the above range, and can realize the production requirements of green and low toxicity.
In the present invention, the mixing of the humate and the activator is preferably ball milling.
In the present invention, the ball milling is preferably solid phase ball milling; the solid phase ball milling is preferably dry alternating ball milling, and the specific operation of the dry alternating ball milling is clockwise ball milling for 30 minutes, anticlockwise ball milling for 30 minutes, and alternating according to the cycle. According to the invention, by limiting the ball milling to the mode, the humate and the activating agent can be fully and uniformly mixed.
In the invention, the ball-to-material ratio of the dry alternating ball milling is preferably 1: (3 to 10), more preferably 1: (4 to 6), more preferably 1:5, a step of; the rotation speed of the dry-method alternate ball milling is preferably 300-800 r/min, more preferably 400-600 r/min, and even more preferably 500r/min; the dry-process alternate ball milling time is preferably 60 to 180min, more preferably 120min. The ball-milling ball-material ratio, the rotating speed and the time of the ball milling are set within the ranges, so that the full ball milling of the mixed powder of the humate and the activator can be ensured, and the follow-up pyrolysis reaction can be facilitated.
In the present invention, the particle size of the mixed powder obtained after the ball milling is preferably <0.074mm. The particle size of the mixed powder obtained after ball milling is controlled to be in the range, so that the pyrolysis reaction can be carried out.
In the present invention, the pyrolysis is preferably performed in a pyrolysis furnace; the pyrolysis furnace is preferably a tube furnace. In the present invention, the pyrolysis process is preferably performed in an inert atmosphere; the inert atmosphere is preferably nitrogen or argon. According to the invention, the pyrolysis atmosphere is set to be an inert atmosphere, so that the influence of gases such as oxygen and the like on the generation of porous carbon by pyrolysis can be avoided.
In the present invention, the temperature of the pyrolysis is preferably 700 to 900 ℃, more preferably 700 to 800 ℃, further preferably 700 ℃; the pyrolysis time is preferably 2 to 3 hours, more preferably 2 to 2.5 hours, and even more preferably 2 hours; the heating rate of the pyrolysis is preferably 4.5 to 5.5 ℃/min, more preferably 5 ℃/min. According to the invention, the porous carbon with a sub-nano porous structure can be generated by pyrolysis by limiting the temperature, time and heating rate of the pyrolysis within the ranges.
After pyrolysis is completed, the invention preferably carries out cooling, purification treatment and drying on the pyrolysis product in sequence to obtain the porous carbon. In the present invention, the cooling means is preferably natural cooling. The invention is not particularly limited to the natural cooling operation, and the pyrolysis product can be cooled to room temperature.
In the present invention, the purification treatment is preferably an acid treatment; the acid used for the acid treatment is preferably hydrochloric acid; the concentration of the hydrochloric acid is preferably 1mol/L. The invention can remove impurities from pyrolysis products through acid treatment.
The specific operation of the acid treatment in the present invention is preferably: and (3) carrying out reaction on the impurity phase of the pyrolysis product according to XRD (X-ray diffraction) by adopting 1mol/L hydrochloric acid and the pyrolysis product under the stirring condition, and then washing and centrifuging to obtain a purified product.
In the present invention, the stirring is preferably magnetic stirring; the stirring time is preferably 12 hours. The stirring speed is not particularly limited, and stirring speeds well known to those skilled in the art may be used.
The operation of the washing is not particularly limited, and the washing may be performed so that the pH of the washing liquid is neutral.
The operation of the centrifugation is not particularly limited in the present invention, and the centrifugation operation known to those skilled in the art can be used to separate the liquid from the solid.
In the present invention, the drying is preferably performed under vacuum; the temperature of the drying is preferably 80 ℃; the drying time is preferably 12 hours. The invention can ensure the stability of the porous carbon material structure through vacuum drying.
The invention adopts the brown coal as the raw material, and is beneficial toOrganic macromolecular humic acid containing rich oxygen functional groups (carboxyl, hydroxyl, carbonyl, quinoyl, methoxy and the like) in lignite is used for preparing porous carbon with a sub-nano pore structure by reacting with acid and alkali to obtain humate, and the humate is used as a carbon precursor; in the pyrolysis process of the humate and the activator, CO generated at a lower temperature is oxidized into CO by oxygen functional groups contained in the humate due to higher oxygen content in the humate 2 ，CO 2 The method has the physical pore-forming function, so that the effect of regulating and controlling pore structures is realized at a lower temperature, and the pyrolysis temperature is reduced; on the other hand, as the non-carbon element is eliminated at high temperature, the carbon precursor is condensed into an aromatic skeleton, and then the aromatic skeleton is etched through oxidation-reduction reaction with an activator to form a porous structure, so that the prepared porous carbon has a sub-nano pore structure, presents a large specific surface area and good pore structure distribution, and when used as an electrode material of a supercapacitor, the porous carbon has high specific capacitance, and due to the existence of oxygen functional groups, the pseudo-capacitance characteristic of the supercapacitor in the electrochemical process can effectively widen a voltage window to increase the energy density of the supercapacitor.
The invention also provides the porous carbon prepared by the preparation method of the technical scheme, and the porous carbon has a sub-nano pore structure.
The pore size distribution of the porous carbon in the present invention is preferably 1nm or less; the specific surface area of the porous carbon is preferably more than or equal to 500m 2 Preferably ≡g ≡700m 2 And/g. The porous carbon with the sub-nano pore structure can ensure smaller pore size distribution and larger specific surface area, so that the electrode material prepared from the porous carbon has high specific capacitance, high energy density and high power density.
The invention provides application of the porous carbon in the super capacitor electrode material.
The technical solutions of the present invention will be clearly and completely described in the following in connection with the embodiments of the present invention. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
The invention provides a preparation method of porous carbon prepared from lignite, which comprises the following steps:
(1) Lignite powder with the particle size of less than 0.074mm, 1mol/L sodium carbonate solution and 1mol/L sodium hydroxide solution are mixed according to the mass volume ratio of 1g:1mL: heating in a constant-temperature water bath at 80 ℃ for 120min after 1mL mixing, then adjusting the pH of the system to 11-12, heating in the constant-temperature water bath for 120min to perform acid-base reaction, cooling and centrifuging the reaction product after the reaction is finished to obtain an extracting solution, adjusting the pH of the extracting solution to 2 by adopting 1mol/L HCl, settling sodium humate in the extracting solution, centrifuging at 8000r/min, drying the centrifuging product in a vacuum drying oven at 80 ℃ for 48h, and grinding to obtain sodium humate;
(2) And (3) mixing the sodium humate and potassium oxalate obtained in the step (1) according to the mass ratio of 1:2, uniformly mixing by adopting a solid-phase ball milling mode, wherein the mass ratio of the mixture to ball milling steel balls is 1:5, adopting a dry method alternate ball milling method, wherein the ball milling time is 120min, the ball milling rotating speed is 500r/min, loading the ball-milled mixture into a corundum boat, placing the corundum boat into a tube furnace in nitrogen atmosphere, heating to 700 ℃ at a heating rate of 5 ℃/min, carrying out pyrolysis for 2h, naturally cooling to room temperature after the pyrolysis is finished to obtain a pyrolysis product, carrying out XRD (X-ray diffraction) measurement on the pyrolysis product, analyzing the impurity phase in the product, carrying out repeated centrifugation and cleaning after reacting 1mol/L hydrochloric acid with the pyrolysis product for 12h under the stirring condition to obtain a purified product, and carrying out vacuum drying on the purified product at 80 ℃ for 12h to obtain porous carbon which is denoted as PC700-2.
A scanning electron microscope image of the porous carbon of the sub-nano pore structure prepared in example 1 is shown in FIG. 1. As can be seen from FIG. 1, the prepared porous carbon has a sub-nano pore structure, and the specific surface area is 722.5m 2 /g。
N of porous carbon prepared in example 1 2 The adsorption and desorption isothermal curves are shown in FIG. 2Shown. As can be seen from FIG. 2, the curve is a typical curve of type I (a), indicating that the porous carbon prepared in example 1 is a purely microporous porous carbon material.
The pore size distribution curve of the porous carbon material prepared in example 1 is shown in fig. 3. As can be seen from the figure, the average pore size distribution was about 0.5nm, and the structure was microporous.
Example 2
The mass ratio of sodium humate to potassium oxalate in example 1 was replaced with 1:1 the porous carbon prepared in example 2 was designated as PC700-1 in the same manner as in example 1.
Application examples 1 and 2
The porous carbon materials prepared in the examples 1 and 2 are used as electrode materials of a supercapacitor, and are assembled into the supercapacitor to carry out electrochemical constant current charge-discharge (GCD), and the specific steps are as follows:
grinding the prepared porous carbon, polyvinylidene fluoride and acetylene black respectively, wherein the mass ratio of the porous carbon to the polyvinylidene fluoride to the acetylene black is 8:1:1, adding absolute ethyl alcohol to prepare slurry, coating the slurry on a carbon sheet, vacuum drying to prepare an electrode, assembling a super capacitor to measure specific capacitance and energy density in a three-electrode and two-electrode system, wherein the three-electrode and the two-electrode system are respectively measured in 6mol/LKOH electrolyte, a CHI760E electrochemical workstation is selected to measure electrical properties, and the constant-current charge-discharge current density range is 0.5-20 A.g -1 。
The porous carbon prepared in examples 1 and 2 had a current density of 1 A.g under a three-electrode system as an electrode material for a supercapacitor -1 The constant current charge-discharge (GCD) curve at this time is shown in fig. 4. As can be seen from fig. 4, the porous carbons prepared in examples 1 and 2 all showed quasi-linear and symmetrical triangular profiles as supercapacitor electrodes, indicating typical electric double layer capacitance characteristics.
The porous carbon prepared in examples 1 and 2 has a current density of 0.5 to 20 A.g under a three-electrode system as an electrode material for a supercapacitor -1 As shown in FIG. 5, the mass specific capacitance measured below is shown, and as can be seen from FIG. 5, the prepared porous carbon is used as the electrode material of the super capacitor, and the current density is 1 A.g -1 In the case of example 1, the mass specific capacitance was 302 F.g -1 The mass specific capacitance of example 2 was 252 F.g -1 The prepared porous carbon is shown to have excellent electrochemical performance when used as an electrode material of a supercapacitor.
As can be seen from FIG. 6, the Lagong diagrams of the porous carbon prepared in examples 1 and 2 as the electrode material of the supercapacitor measured in the double electrode system are shown in FIG. 6, and the porous carbon prepared in example 1 has a power density of 550 W.kg -1 At the time of energy density of 31.8 Wh.kg -1 The power density is 22000 W.kg -1 At the time of energy density of 17.7 Wh.kg -1 The porous carbon prepared in example 2 had a power density of 550 W.kg -1 At the time of energy density of 20 Wh.kg -1 The power density is 21000 W.kg -1 At the time of energy density 9.8 Wh.kg -1 As can be seen from the Lagong plot, the prepared porous carbon of sub-nano-porous structure shows high energy density.
The cycling curve of the porous carbon prepared in example 1 as an electrode material of a supercapacitor is shown in FIG. 7, and it can be seen from FIG. 7 that 5 A.g.was measured under a double electrode system -1 The cycle stability of (2) can still maintain 60.6% of capacitance after 6800 circles of cycle, and the coulomb efficiency reaches 99.4%.
As shown by testing the performances of the porous carbon prepared in the examples 1 and 2 and the supercapacitor electrode material composed of the porous carbon, the average pore size of the porous carbon prepared by the invention is distributed at about 0.5nm, and the porous carbon has a micropore structure; when the porous carbon is used as the electrode material of the super capacitor, the current density is 1 A.g -1 When the mass specific capacitance is 252-302 F.g -1 The method comprises the steps of carrying out a first treatment on the surface of the At a power density of 550 W.kg -1 The energy density is 20-31.8 Wh.kg -1 At a power density of 22000 W.kg -1 When the energy density is 9.8 to 17.7Wh.kg -1 Has high specific capacitance, high energy density and high power density, can be applied to the field of super capacitor electrode materials.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (10)
1. The preparation method of the porous carbon prepared by taking the lignite as the raw material comprises the following steps:
(1) Mixing lignite with an alkaline solution, and heating to perform an acid-base reaction to obtain humate;
(2) And (3) mixing the humate obtained in the step (1) with an activating agent, and then performing pyrolysis to obtain the porous carbon.
2. The method according to claim 1, wherein the alkaline solution in the step (1) is a mixture of sodium carbonate solution and sodium hydroxide solution.
3. The method according to claim 2, wherein the volume ratio of the lignite mass to the sodium carbonate solution and sodium hydroxide solution in step (1) is 1g: (1-2.5) mL: (1-2.5) mL.
4. A method according to claim 2 or 3, characterized in that the concentration of the sodium carbonate solution and the sodium hydroxide solution is independently 1-2 mol/L.
5. The method of claim 1, wherein the heating in step (1) comprises the steps of:
(a) Mixing lignite with an alkaline solution and then carrying out first heating to obtain a product 1;
(b) Regulating the pH value of the product 1 obtained in the step (a) to 11-12, and then performing second heating to obtain humate;
the temperature of the first heating in the step (a) and the second heating in the step (b) is independently 75-85 ℃, and the time of the first heating and the second heating is independently 60-180 min.
6. The method according to claim 1, wherein the mass ratio of humate to activator in step (2) is 1: (1-3).
7. The method of claim 1 or 6, wherein the activator is an oxalate.
8. The method according to claim 1, wherein the pyrolysis in the step (2) is performed at a temperature of 700 to 900 ℃ for a time of 2 to 3 hours.
9. The porous carbon produced by the production method according to any one of claims 1 to 8, wherein the porous carbon has a sub-nano pore structure.
10. Use of the porous carbon of claim 9 in supercapacitor electrode materials.
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