CN109331804B - Graphene nanodisk and preparation method and application thereof - Google Patents
Graphene nanodisk 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 91
- 229910021389 graphene Inorganic materials 0.000 title claims abstract description 87
- 238000002360 preparation method Methods 0.000 title claims abstract description 29
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 claims abstract description 60
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 claims abstract description 27
- 235000019253 formic acid Nutrition 0.000 claims abstract description 27
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 19
- 239000002994 raw material Substances 0.000 claims abstract description 14
- 238000000034 method Methods 0.000 claims abstract description 13
- 238000004519 manufacturing process Methods 0.000 claims abstract description 7
- 230000008569 process Effects 0.000 claims abstract description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 claims description 53
- 229910002092 carbon dioxide Inorganic materials 0.000 claims description 42
- 239000001569 carbon dioxide Substances 0.000 claims description 26
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 22
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 22
- 229910017604 nitric acid Inorganic materials 0.000 claims description 22
- 238000006243 chemical reaction Methods 0.000 claims description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 20
- 238000003756 stirring Methods 0.000 claims description 19
- 239000002055 nanoplate Substances 0.000 claims description 16
- 230000009467 reduction Effects 0.000 claims description 14
- 238000005119 centrifugation Methods 0.000 claims description 12
- 239000002107 nanodisc Substances 0.000 claims description 12
- 238000005303 weighing Methods 0.000 claims description 12
- 238000001035 drying Methods 0.000 claims description 11
- 238000005406 washing Methods 0.000 claims description 11
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 8
- 239000008367 deionised water Substances 0.000 claims description 8
- 229910021641 deionized water Inorganic materials 0.000 claims description 8
- 238000000502 dialysis Methods 0.000 claims description 8
- 239000012153 distilled water Substances 0.000 claims description 8
- 238000002390 rotary evaporation Methods 0.000 claims description 8
- 230000003647 oxidation Effects 0.000 claims description 7
- 238000007254 oxidation reaction Methods 0.000 claims description 7
- 238000004108 freeze drying Methods 0.000 claims description 4
- 239000005457 ice water Substances 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 4
- 230000007935 neutral effect Effects 0.000 claims description 4
- 239000000843 powder Substances 0.000 claims description 4
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Inorganic materials [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 claims description 4
- 239000007787 solid Substances 0.000 claims description 4
- 239000002904 solvent Substances 0.000 claims description 4
- 239000000725 suspension Substances 0.000 claims description 4
- 238000001291 vacuum drying Methods 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 229910021382 natural graphite Inorganic materials 0.000 claims description 3
- 230000035484 reaction time Effects 0.000 claims description 3
- 239000000243 solution Substances 0.000 abstract description 26
- 239000003054 catalyst Substances 0.000 abstract description 9
- 239000003575 carbonaceous material Substances 0.000 abstract description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 abstract description 5
- 238000010531 catalytic reduction reaction Methods 0.000 abstract description 5
- 230000007547 defect Effects 0.000 abstract description 5
- 239000001301 oxygen Substances 0.000 abstract description 5
- 229910052760 oxygen Inorganic materials 0.000 abstract description 5
- 230000015572 biosynthetic process Effects 0.000 abstract description 3
- 229910052799 carbon Inorganic materials 0.000 abstract description 3
- 239000002356 single layer Substances 0.000 abstract description 3
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical group [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 abstract description 2
- 239000006227 byproduct Substances 0.000 abstract description 2
- 239000003792 electrolyte Substances 0.000 abstract description 2
- 239000002086 nanomaterial Substances 0.000 abstract description 2
- 239000005416 organic matter Substances 0.000 abstract description 2
- 235000002639 sodium chloride Nutrition 0.000 abstract description 2
- 239000011780 sodium chloride Substances 0.000 abstract description 2
- 238000006722 reduction reaction Methods 0.000 description 17
- 239000002245 particle Substances 0.000 description 11
- 239000000446 fuel Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 238000000089 atomic force micrograph Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 4
- 238000001000 micrograph Methods 0.000 description 4
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 description 3
- 230000005291 magnetic effect Effects 0.000 description 3
- 238000001075 voltammogram Methods 0.000 description 3
- 238000004435 EPR spectroscopy Methods 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- UIIMBOGNXHQVGW-UHFFFAOYSA-M Sodium bicarbonate Chemical compound [Na+].OC([O-])=O UIIMBOGNXHQVGW-UHFFFAOYSA-M 0.000 description 2
- 239000008151 electrolyte solution Substances 0.000 description 2
- 229940021013 electrolyte solution Drugs 0.000 description 2
- 239000010410 layer Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 238000011946 reduction process Methods 0.000 description 2
- 230000004044 response Effects 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 239000007832 Na2SO4 Substances 0.000 description 1
- 229920000557 Nafion® Polymers 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- ZOMNIUBKTOKEHS-UHFFFAOYSA-L dimercury dichloride Chemical class Cl[Hg][Hg]Cl ZOMNIUBKTOKEHS-UHFFFAOYSA-L 0.000 description 1
- 238000009510 drug design Methods 0.000 description 1
- 239000010411 electrocatalyst Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 239000005431 greenhouse gas Substances 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 239000011736 potassium bicarbonate Substances 0.000 description 1
- 229910000028 potassium bicarbonate Inorganic materials 0.000 description 1
- 150000003384 small molecules Chemical class 0.000 description 1
- 229910000030 sodium bicarbonate Inorganic materials 0.000 description 1
- 229910052938 sodium sulfate Inorganic materials 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 238000010792 warming Methods 0.000 description 1
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
- B01J21/18—Carbon
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J35/00—Catalysts, in general, characterised by their form or physical properties
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- B01J35/33—Electric or magnetic properties
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- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/182—Graphene
- C01B32/184—Preparation
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B3/00—Electrolytic production of organic compounds
- C25B3/20—Processes
- C25B3/25—Reduction
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Abstract
The invention relates to a nano material, in particular to a nano materialRelates to a graphene nanodisk with controllable size and uniform appearance, and a preparation method and application thereof. The invention prepares the single-layer graphene nanodisk with controllable size and uniform appearance by a simple one-step hydrothermal method for the first time, which is a low-cost carbon-based material rich in oxygen defects and has excellent CO2Catalytic reduction performance. Catalyzing CO at overpotential 430mV2The faradaic efficiency of generating formic acid can reach 87 percent, the initial overpotential is as low as 230mV, and no other by-products exist, so that the problems of the carbon-based catalyst are solved, and the carbon-based material for catalyzing and reducing CO is reported to be the carbon-based material2Best performance of formic acid formation. The preparation method of the graphene nanodisk provided by the invention has the advantages that the raw materials are easily available, the process flow is simple, the production cost is greatly reduced, and the large-scale industrial application is facilitated; and the electrolyte is common salt solution without adding any organic matter.
Description
Technical Field
The invention relates to a nano material, in particular to a graphene nanodisk with controllable size and uniform appearance, and a preparation method and application thereof.
Background
Since the industrial revolution, with the rapid progress of human production and life, more and more carbon dioxide has been discharged into the atmosphere. This continuously increasing emission of carbon dioxide has begun to gradually impact the earth's environment. In addition, CO2Global warming due to large emissions has become one of the most environmental concerns worldwide. Therefore, the greenhouse gas CO is efficiently introduced2The conversion into liquid fuel with added value is very valuable for research. Electrocatalytic reduction of carbon dioxide (CO) due to mild reaction conditions and controllability of reaction products2RR) are economically valuable small molecule products that have become promising solutions to increase energy demand. Over the course of several years of research, although researchers have developed a number of highly efficient electrocatalysts for the electrocatalytic reduction of CO2However, how to realize the purpose of meeting the actual production requirement and reducing the preparation cost of the catalyst and simultaneously still maintaining higher catalytic efficiencyIs a research difficulty in the field.
Electrochemical carbon dioxide reduction processes also face numerous challenges, the most important of which is how to increase reaction efficiency and product selectivity, which requires rational design of the catalyst to achieve efficient and highly selective carbon dioxide reduction reactions. Formic acid has received much attention from researchers as a renewable transportation fuel due to its high energy density, ease of remote transportation, and direct ability to make a promising formic acid fuel cell. However, the production process of the currently reported catalyst for converting carbon dioxide into formic acid is complex, the cost of raw materials is high, and the catalyst mainly comprises a metal catalyst; moreover, the efficiency of converting the formic acid into the formic acid is low, and the required overpotential is high.
Disclosure of Invention
The invention aims to solve the technical problems in the prior art and provides a graphene nanodisk with controllable size and uniform appearance as well as a preparation method and application thereof. The graphene nanodisk is a carbon-based material rich in oxygen defects and used for catalytic reduction of CO at a lower overpotential (430mV)2Formic acid is generated, the Faraday efficiency reaches 87%, the preparation process is extremely simple, the production cost is greatly reduced, and the large-scale industrial application is facilitated.
In order to solve the technical problems, the technical scheme of the invention is as follows:
the invention provides a preparation method of a graphene nanodisk, which comprises the following steps:
graphene oxide powder is used as a raw material, concentrated nitric acid is used as a solvent, and a graphene nanoplate is prepared by a hydrothermal method.
In the above technical scheme, the graphene oxide powder is prepared by the following method:
weighing 1g of natural graphite, adding 0.74g of NaNO3And 34mL of 98% H2SO4Mixing in ice-water bath, and stirring vigorously; later 5g KMnO was slowly added4Keeping the temperature below 20 ℃, and then transferring the mixture into a water bath at 35 ℃ to stir for 3 hours; after stirring, 250mL of deionized water was added and 4mL of 30% wt H was slowly added2O2Finishing the reaction; the bright yellow suspension obtained is washed by centrifugation with a 5% hydrochloric acid solution to remove the remaining H2SO4Washing with deionized water for several times until the pH value is neutral; and drying the washed graphene solution in a freeze drying or vacuum drying mode to obtain solid powder.
In the technical scheme, the mass fraction of the concentrated nitric acid is 65%.
In the above technical scheme, the preparation method of the graphene nanoplate specifically comprises the steps of:
weighing dried graphene oxide powder, adding 65% by mass of concentrated nitric acid, wherein the volume of the concentrated nitric acid is 1/10-1/20 of the mass of the graphene oxide powder, performing ultrasonic stirring until a uniformly dispersed solution is formed, then placing the solution in a hydrothermal reaction kettle, reacting for 4-10 hours at the temperature of 100 plus of 200 ℃, cooling the reaction kettle to the normal temperature, adding distilled water for multiple times, washing, collecting and drying in a rotary evaporation, centrifugation and dialysis mode, and obtaining the graphene nanoplate with controllable size and uniform appearance.
In the technical scheme, the dosage of the graphene oxide powder is 400mg, and the dosage of the concentrated nitric acid is 20-40 mL.
In the technical scheme, the reaction temperature is 140-180 ℃.
In the technical scheme, the reaction temperature is 160 ℃, and the reaction time is 6 hours.
The invention also provides the graphene nanodisk prepared by the preparation method.
In the technical scheme, the size of the graphene nanodisk is 30-180 nm, and the thickness is 1 nm; and the oxidation degree g value reaches 2.01.
The invention also provides an application of the graphene nano disc prepared by the preparation method in efficient electrocatalytic reduction of carbon dioxide to generate formic acid.
The invention has the beneficial effects that:
1. electrocatalytic reduction of CO known in the prior art2Most of catalysts for generating formic acid are metal and alloying materials thereof, raw materials are expensive, and preparation process is adoptedThe complexity is high; and there are few reports that the carbon-based material itself can catalyze the reduction of CO2. The invention prepares the single-layer graphene nanodisk with controllable size and uniform appearance by a simple one-step hydrothermal method for the first time, which is a low-cost carbon-based material rich in oxygen defects and has excellent CO2Catalytic reduction performance.
2. The graphene nanodisk provided by the invention is used as a catalyst for catalytic reduction of CO2Formic acid is generated, and CO is catalyzed under the condition of overpotential of 430mV2The faradaic efficiency of generating formic acid can reach 87 percent, the initial overpotential is as low as 230mV, and no other by-products exist, so that the problems of the carbon-based catalyst are solved, and the carbon-based material for catalyzing and reducing CO is reported to be the carbon-based material2Best performance of formic acid formation. Meanwhile, the invention also provides graphene nanodiscs with different oxidation degrees and CO electrocatalytic reduction thereof2The correlation of the properties of formic acid formation was also investigated.
3. The preparation method of the graphene nanodisk provided by the invention has the advantages that the raw materials are easily available, the process flow is simple, the production cost is greatly reduced, and the large-scale industrial application is facilitated; and the electrolyte is common salt solution without adding any organic matter.
4. The graphene nanodisk prepared by the preparation method provided by the invention electrocatalysis CO2The formic acid generated by reduction is convenient for remote transportation due to high energy density; therefore, the fuel cell can be directly made into a promising formic acid fuel cell, and is a good way to recycle CO2The method of (1).
Drawings
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Fig. 1 is a transmission electron microscope image of a graphene nanoplate prepared in example 1 of the present invention.
Fig. 2 is an atomic force microscope image of the graphene nanodisk prepared in example 1 of the present invention.
Fig. 3 is an atomic force microscope image of graphene oxide with different thicknesses prepared by the present invention.
Fig. 4 is an electron paramagnetic resonance image of the graphene nanodisk prepared in example 1 of the present invention.
FIG. 5 shows that the graphene nanodisks prepared in example 1 of the present invention reduce CO2Linear scan voltammogram of (a).
FIG. 6 shows that the graphene nanodisks prepared in example 1 of the present invention react with CO at different potentials2Faradaic efficiency plot reduced to formic acid.
FIG. 7 shows that graphene nanodiscs prepared in examples 1, 2 and 3 of the present invention at different hydrothermal reaction temperatures reduce CO2Linear sweep voltammogram of (a).
FIG. 8 shows that the graphene nanodiscs prepared in examples 1, 2 and 3 of the present invention react with CO at different hydrothermal reaction temperatures2Comparative faradaic efficiency figures for reduction to formic acid.
FIG. 9 shows that the graphene nanodisk prepared in example 1 of the present invention catalyzes CO at-0.68V2Reduction to give a nuclear magnetic map of formic acid.
Fig. 10 is a transmission electron microscope image of the graphene nanodisk prepared in example 1 at another magnification.
Detailed Description
The invention provides a preparation method of a graphene nanodisk with controllable size and uniform appearance, which comprises the following steps:
graphene oxide powder is used as a raw material, concentrated nitric acid is used as a solvent, and a hydrothermal method is adopted to prepare the graphene nanoplate with controllable size and uniform appearance.
The invention preferably takes the graphene oxide powder prepared by the improved Hummers method as a raw material (the thickness of the graphene can be a single layer or a plurality of layers); the method comprises the following specific steps:
weighing 1g of natural graphite, adding 0.74g of NaNO3And 34mL of 98% H2SO4Mixing in ice-water bath, and stirring vigorously; later 5g KMnO was slowly added4Keeping the temperature below 20 ℃, and then transferring the mixture into a water bath at 35 ℃ to stir for 3 hours; after stirring, 250mL of deionized water was added and 4mL of 30% wt H was slowly added2O2Finishing the reaction; the bright yellow suspension obtained is washed by centrifugation with a 5% hydrochloric acid solution to removeRemaining H2SO4Washing with deionized water for several times until the pH value is neutral; and drying the washed graphene solution in a freeze drying or vacuum drying mode to obtain solid powder.
Taking the graphene oxide powder prepared by the improved Hummers method as a raw material, taking concentrated nitric acid as a solvent, and preparing an oxygen-enriched defect graphene nanodisk with uniform size and thickness of only 1nm by a hydrothermal method; and the graphene nanodisk material is used for electrocatalytic reduction of CO2Formic acid is generated.
Preferably, the mass fraction of the concentrated nitric acid is 65%.
The preferable preparation method of the graphene nanodisk with controllable size and uniform appearance comprises the following specific steps:
weighing dried graphene oxide powder, adding 65% by mass of concentrated nitric acid, wherein the volume of the concentrated nitric acid is 1/10-1/20 of the mass of the graphene oxide powder, performing ultrasonic stirring until a uniformly dispersed solution is formed, then placing the solution in a hydrothermal reaction kettle, reacting for 4-10 hours at the temperature of 100 plus of 200 ℃, cooling the reaction kettle to the normal temperature, adding distilled water for multiple times to wash, collect and dry the solution by adopting a rotary evaporation, centrifugation and dialysis mode, and obtaining the graphene nanoplate with controllable size and uniform appearance.
Preferably, the dosage of the graphene oxide powder is 400mg, and the dosage of the concentrated nitric acid is 20-40 mL.
Further preferably, the reaction temperature is 140 ℃ and 180 ℃. Most preferably, the reaction temperature is 160 ℃ and the reaction time is 6 hours.
The invention also provides the graphene nanodisk prepared by the preparation method. The size of the graphene nanodisk is 30-180 nm, and the thickness is 1 nm; and the oxidation degree g value reaches 2.01.
The invention also provides an application of the graphene nano disc prepared by the preparation method in efficient electrocatalytic reduction of carbon dioxide to generate formic acid.
The present invention will be described in detail with reference to the accompanying drawings.
Preparing a graphene oxide raw material:
weighing natural stoneInk 1g, Add 0.74g NaNO3And 34mL of 98% H2SO4Mixing in ice-water bath, and stirring vigorously; later 5g KMnO was slowly added4The temperature was maintained below 20 ℃ and then transferred to a 35 ℃ water bath and stirred for 3 hours. After stirring, 250mL of deionized water was added and 4mL of 30% wt H was slowly added2O2The reaction was terminated. The bright yellow suspension obtained is washed by centrifugation with a 5% hydrochloric acid solution to remove the remaining H2SO4And then repeatedly washing with deionized water until the pH value is neutral. And drying the washed graphene solution in a freeze drying or vacuum drying mode to obtain a solid.
Example 1: preparation of graphene nanodisk with particle size of 70nm
Weighing 400mg of dried graphene oxide powder, adding 40mL of concentrated nitric acid with the mass fraction of 65%, ultrasonically stirring for 3 hours until a uniformly dispersed solution is formed, then placing the solution in a hydrothermal reaction kettle, reacting for 6 hours at 160 ℃, after the reaction kettle is cooled to normal temperature, adding distilled water for 4-5 times in a rotary evaporation, centrifugation and dialysis manner, washing, collecting and drying to obtain a graphene nanoplate with the particle size of 70nm and the thickness of 1 nm.
Example 2: preparation of graphene nanodisk with particle size of 180nm
Weighing 400mg of dried graphene oxide powder, adding 40mL of concentrated nitric acid with the mass fraction of 65%, ultrasonically stirring for 3 hours until a uniformly dispersed solution is formed, then placing the solution in a hydrothermal reaction kettle, reacting for 4 hours at 140 ℃, after the reaction kettle is cooled to normal temperature, adding distilled water for 4-5 times in a rotary evaporation, centrifugation and dialysis manner, washing, collecting and drying to obtain a graphene nanoplate with the particle size of 180nm and the thickness of 1 nm.
Example 3: preparation of graphene nanodisk with particle size of 30nm
Weighing 400mg of dried graphene oxide powder, adding 40mL of concentrated nitric acid with the mass fraction of 65%, ultrasonically stirring for 3 hours until a uniformly dispersed solution is formed, then placing the solution in a hydrothermal reaction kettle, reacting for 10 hours at 180 ℃, after the reaction kettle is cooled to normal temperature, adding distilled water for 4-5 times in a rotary evaporation, centrifugation and dialysis manner, washing, collecting and drying to obtain a graphene nanoplate with the particle size of 30nm and the thickness of 1 nm.
Example 4: preparation of graphene nanodisk with particle size of 140nm
Weighing 400mg of dried graphene oxide powder, adding 40ml of concentrated nitric acid with the mass fraction of 65%, ultrasonically stirring for 3 hours until a uniformly dispersed solution is formed, then placing the solution in a hydrothermal reaction kettle, reacting for 10 hours at 100 ℃, after the reaction kettle is cooled to normal temperature, adding distilled water for 4-5 times in a rotary evaporation, centrifugation and dialysis manner, washing, collecting and drying to obtain a graphene nanoplate with the particle size of 140nm and the thickness of 1 nm.
Example 5: preparation of graphene nanodisk with particle size of 60nm
Weighing 400mg of dried graphene oxide powder, adding 20 ml of 65% concentrated nitric acid, ultrasonically stirring for 3 hours until a uniformly dispersed solution is formed, then placing the solution in a hydrothermal reaction kettle, reacting for 8 hours at 200 ℃, after the reaction kettle is cooled to normal temperature, adding distilled water for 4-5 times in a rotary evaporation, centrifugation and dialysis manner, washing, collecting and drying to obtain a graphene nanoplate with the particle size of 60nm and the thickness of 1 nm.
Example 6
The method for preparing the formic acid by using the graphene nanodisk material to efficiently electro-catalytically reduce carbon dioxide comprises the following specific steps:
in a three-electrode electrolytic cell partitioned by a proton exchange membrane, the graphene nanodisk powder prepared in examples 1, 2 and 3 was mixed with ethanol and Nafion solution, ultrasonically dispersed, uniformly coated on carbon paper as a working electrode, a platinum sheet as a counter electrode, a saturated calomel electrode as a reference electrode, electrolyte solutions were filled in a cathode cell and an anode cell, respectively, and CO was introduced2To saturation, then continuously introducing CO2Reduction of CO at constant potential under the conditions of (1)2The potential control range in the constant potential reduction process is-0.33V to-0.93V vs. RHE, and the electrolytic reduction time is 3-5 h. The electrolyte solution is NaHCO3、KHCO3Or Na2SO4And (3) solution.
Fig. 1 is a transmission electron microscope image of a graphene nanoplate prepared in example 1 of the present invention; the figure shows that the graphene nanodiscs prepared in example 1 have a circular ultrathin sheet layer structure and are uniform in size.
Fig. 2 is an atomic force microscope image of a graphene nanodisk prepared in example 1 of the present invention; it can be seen from the figure that the average thickness is 1 nm.
FIG. 3 is an atomic force microscope image of graphene oxide having a thickness of 0.7nm and 2nm prepared according to the method for preparing a graphene oxide raw material of the present invention; it can be seen from the figure that the two graphene oxide raw materials are both in an amorphous lamellar structure, and the thicknesses are obviously different. The shape of the nano disc finally prepared by the preparation method of the graphene nano disc provided by the invention is irrelevant to the thickness of the raw material, and the graphene nano disc with controllable size and uniform appearance can be obtained by using the graphene oxide raw materials with different thicknesses.
Fig. 4 is an electron paramagnetic resonance (nmr) map of a graphene nanodisk prepared in example 1 of the present invention; the graph shows that the graphene nanodisk prepared by the method has very high oxidation degree and rich oxygen defects, and the oxidation g value reaches 2.01.
FIG. 5 shows that the graphene nanodisks prepared in example 1 of the present invention reduce CO2Linear scanning voltammogram of (a); from the figure, it can be seen that the prepared graphene nanodisk material is aligned to CO2The response of (a) is very large.
FIG. 6 shows that the graphene nanodisks prepared in example 1 of the present invention react with CO at different potentials2Faradaic efficiency plot reduced to formic acid; it can be seen from the figure that the faradaic efficiency for formic acid reaches a maximum of 87% when the potential is-0.68V; and when the initial overpotential is only 0.23V, the Faraday efficiency of formic acid generation can still reach 28%.
FIG. 7 shows that graphene nanodiscs prepared in examples 1, 2 and 3 of the present invention at different hydrothermal reaction temperatures reduce CO2Linear sweep voltammetric comparison plot of (a); this figure illustrates graphite synthesized at different hydrothermal reaction temperaturesAlkene nanodisk pair CO2The response of (2) is different, the graphene nanodisk at a temperature of 160 ℃ shows the largest current and the smallest initial potential.
FIG. 8 shows that the graphene nanodiscs prepared in examples 1, 2 and 3 of the present invention react with CO at different hydrothermal reaction temperatures2Comparative faradaic efficiency figures for reduction to formic acid; as can be seen from the figure, the graphene nanodisk CO synthesized at 160 ℃ is2The reduction performance is best. The peak overpotential at 160 ℃ is obviously lower than that of the graphene nanoplate at 180 ℃, and the faradaic efficiency of generating formic acid is also obviously higher than that of other two different temperatures. This also further verifies CO2The catalytic reduction performance is related to the degree of oxidation of the material.
FIG. 9 shows that the graphene nanodisk prepared in example 1 of the present invention catalyzes CO at-0.68V2Reduction to give a nuclear magnetic map of formic acid. The figure illustrates that: formic acid was indeed detected by nuclear magnetic NMR (AV 500) hydrogen spectroscopy, as shown by the graphical indication; and quantitation was performed with DMSO as internal standard.
Fig. 10 is a transmission electron microscope image of the graphene nanodisk prepared in example 1 at another magnification. From the figure, it can be seen that the average particle size of the prepared graphene nanoplate is 70 nm.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications therefrom are within the scope of the invention.
Claims (9)
1. A preparation method of a graphene nanodisk is characterized by comprising the following steps:
preparing a graphene nanoplate by using graphene oxide powder as a raw material and concentrated nitric acid as a solvent through a hydrothermal method;
the size of the graphene nanodisk is 30-180 nm, and the thickness is 1 nm;
the mass fraction of the concentrated nitric acid is 65%, and the adding volume of the concentrated nitric acid is 1/10-1/20 of the mass of the graphene oxide powder;
the hydrothermal condition is 100-200 ℃ for 4-10 hours.
2. The production method according to claim 1, wherein the graphene oxide powder is produced by:
weighing 1g of natural graphite, adding 0.74g of NaNO3And 34mL of 98% H2SO4Mixing in ice water bath and stirring; later 5g KMnO was added4Keeping the temperature below 20 ℃, and then transferring the mixture into a water bath at 35 ℃ to stir for 3 hours; after stirring, 250mL of deionized water was added followed by 4mL of 30% wt H2O2Finishing the reaction; the bright yellow suspension obtained is washed by centrifugation with a 5% hydrochloric acid solution to remove the remaining H2SO4Washing with deionized water for several times until the pH value is neutral; and drying the washed graphene solution in a freeze drying or vacuum drying mode to obtain solid powder.
3. The preparation method according to claim 1, characterized by comprising the following specific steps:
weighing dry graphene oxide powder, adding 65% by mass of concentrated nitric acid, wherein the volume of the concentrated nitric acid is 1/10-1/20 of the mass of the graphene oxide powder, performing ultrasonic stirring until a uniformly dispersed solution is formed, then placing the solution in a hydrothermal reaction kettle, reacting for 4-10 hours at the temperature of 100 plus of 200 ℃, cooling the reaction kettle to normal temperature, adding distilled water for multiple times, washing, collecting and drying in a rotary evaporation, centrifugation and dialysis manner, and obtaining the graphene nanoplate with controllable size and uniform appearance.
4. The preparation method according to claim 3, wherein the amount of the graphene oxide powder is 400mg, and the amount of the concentrated nitric acid is 20-40 mL.
5. The method as claimed in claim 3, wherein the reaction temperature is 140-180 ℃.
6. The process according to claim 3, wherein the reaction temperature is 160 ℃ and the reaction time is 6 hours.
7. A graphene nanodisk made by the method of any one of claims 1-6.
8. The graphene nanodisk as claimed in claim 7, wherein the graphene nanodisk is 30-180 nm in size and 1nm thick; and the oxidation degree g value reaches 2.01.
9. The application of the graphene nanodiscs prepared by the preparation method of any one of claims 1-6 in high-efficiency electrocatalytic reduction of carbon dioxide to formic acid.
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