CN111701596B - Preparation method of atomic-scale active site catalyst for synthesizing ammonia under mild condition - Google Patents
Preparation method of atomic-scale active site catalyst for synthesizing ammonia under mild condition Download PDFInfo
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- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 title claims abstract description 118
- 239000003054 catalyst Substances 0.000 title claims abstract description 78
- 229910021529 ammonia Inorganic materials 0.000 title claims abstract description 59
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 230000002194 synthesizing effect Effects 0.000 title description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 44
- 238000006243 chemical reaction Methods 0.000 claims abstract description 33
- 229910021389 graphene Inorganic materials 0.000 claims abstract description 30
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 26
- 230000000694 effects Effects 0.000 claims abstract description 25
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 19
- 238000003786 synthesis reaction Methods 0.000 claims abstract description 19
- 239000002131 composite material Substances 0.000 claims abstract description 14
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 13
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000001257 hydrogen Substances 0.000 claims abstract description 10
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 10
- 239000011259 mixed solution Substances 0.000 claims description 160
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 64
- 239000008367 deionised water Substances 0.000 claims description 55
- 229910021641 deionized water Inorganic materials 0.000 claims description 55
- 239000000243 solution Substances 0.000 claims description 51
- 238000003756 stirring Methods 0.000 claims description 44
- 239000011521 glass Substances 0.000 claims description 42
- UMGDCJDMYOKAJW-UHFFFAOYSA-N thiourea Chemical compound NC(N)=S UMGDCJDMYOKAJW-UHFFFAOYSA-N 0.000 claims description 42
- 239000010410 layer Substances 0.000 claims description 30
- 238000001291 vacuum drying Methods 0.000 claims description 28
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Natural products NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 21
- 229910002804 graphite Inorganic materials 0.000 claims description 21
- 239000010439 graphite Substances 0.000 claims description 21
- 239000005457 ice water Substances 0.000 claims description 21
- 239000012286 potassium permanganate Substances 0.000 claims description 21
- 235000015393 sodium molybdate Nutrition 0.000 claims description 21
- 239000011684 sodium molybdate Substances 0.000 claims description 21
- TVXXNOYZHKPKGW-UHFFFAOYSA-N sodium molybdate (anhydrous) Chemical compound [Na+].[Na+].[O-][Mo]([O-])(=O)=O TVXXNOYZHKPKGW-UHFFFAOYSA-N 0.000 claims description 21
- 239000006228 supernatant Substances 0.000 claims description 21
- 150000001875 compounds Chemical class 0.000 claims description 20
- 239000011229 interlayer Substances 0.000 claims description 20
- 238000002156 mixing Methods 0.000 claims description 19
- NWZSZGALRFJKBT-KNIFDHDWSA-N (2s)-2,6-diaminohexanoic acid;(2s)-2-hydroxybutanedioic acid Chemical compound OC(=O)[C@@H](O)CC(O)=O.NCCCC[C@H](N)C(O)=O NWZSZGALRFJKBT-KNIFDHDWSA-N 0.000 claims description 14
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 14
- IKDUDTNKRLTJSI-UHFFFAOYSA-N hydrazine monohydrate Substances O.NN IKDUDTNKRLTJSI-UHFFFAOYSA-N 0.000 claims description 14
- 230000001590 oxidative effect Effects 0.000 claims description 14
- 239000000126 substance Substances 0.000 claims description 14
- QAOWNCQODCNURD-UHFFFAOYSA-N sulfuric acid Substances OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 14
- 238000001035 drying Methods 0.000 claims description 12
- 238000005119 centrifugation Methods 0.000 claims description 11
- 238000006460 hydrolysis reaction Methods 0.000 claims description 11
- 239000000047 product Substances 0.000 claims description 11
- 239000012495 reaction gas Substances 0.000 claims description 9
- 239000012279 sodium borohydride Substances 0.000 claims description 8
- 229910000033 sodium borohydride Inorganic materials 0.000 claims description 8
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 7
- 230000003197 catalytic effect Effects 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 7
- -1 polytetrafluoroethylene Polymers 0.000 claims description 7
- 229920001343 polytetrafluoroethylene Polymers 0.000 claims description 7
- 239000004810 polytetrafluoroethylene Substances 0.000 claims description 7
- 239000002244 precipitate Substances 0.000 claims description 7
- 239000013049 sediment Substances 0.000 claims description 7
- 229910001220 stainless steel Inorganic materials 0.000 claims description 7
- 239000010935 stainless steel Substances 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 7
- 238000005259 measurement Methods 0.000 claims description 5
- 238000009210 therapy by ultrasound Methods 0.000 claims description 4
- 238000005265 energy consumption Methods 0.000 abstract description 4
- 238000001179 sorption measurement Methods 0.000 abstract description 4
- 230000008901 benefit Effects 0.000 abstract description 3
- 239000006185 dispersion Substances 0.000 abstract description 3
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 abstract 4
- CWQXQMHSOZUFJS-UHFFFAOYSA-N molybdenum disulfide Chemical compound S=[Mo]=S CWQXQMHSOZUFJS-UHFFFAOYSA-N 0.000 abstract 3
- 229910052982 molybdenum disulfide Inorganic materials 0.000 abstract 3
- 230000005540 biological transmission Effects 0.000 abstract 1
- 229910052697 platinum Inorganic materials 0.000 abstract 1
- 238000007036 catalytic synthesis reaction Methods 0.000 description 10
- 238000000034 method Methods 0.000 description 9
- 230000008569 process Effects 0.000 description 7
- 230000001699 photocatalysis Effects 0.000 description 5
- 241000282326 Felis catus Species 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 4
- 238000004178 biological nitrogen fixation Methods 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 4
- 230000007062 hydrolysis Effects 0.000 description 4
- 230000007246 mechanism Effects 0.000 description 4
- 230000004913 activation Effects 0.000 description 3
- 238000001994 activation Methods 0.000 description 3
- 238000006555 catalytic reaction Methods 0.000 description 3
- 238000007146 photocatalysis Methods 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- 230000004888 barrier function Effects 0.000 description 2
- 230000003592 biomimetic effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000010494 dissociation reaction Methods 0.000 description 2
- 230000005593 dissociations Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000002135 nanosheet Substances 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 102000004190 Enzymes Human genes 0.000 description 1
- 108090000790 Enzymes Proteins 0.000 description 1
- 229910017116 Fe—Mo Inorganic materials 0.000 description 1
- 238000009620 Haber process Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000002860 competitive effect Effects 0.000 description 1
- 238000005984 hydrogenation reaction Methods 0.000 description 1
- 238000001027 hydrothermal synthesis Methods 0.000 description 1
- 238000002329 infrared spectrum Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 239000012048 reactive intermediate Substances 0.000 description 1
- 230000005476 size effect Effects 0.000 description 1
- 238000000527 sonication Methods 0.000 description 1
- 241000894007 species Species 0.000 description 1
- 230000002195 synergetic effect Effects 0.000 description 1
- 229910052723 transition metal Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
Classifications
-
- 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
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
- B01J27/04—Sulfides
- B01J27/047—Sulfides with chromium, molybdenum, tungsten or polonium
- B01J27/051—Molybdenum
- B01J27/0515—Molybdenum with iron group metals or platinum group metals
-
- 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
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/02—Sulfur, selenium or tellurium; Compounds thereof
- B01J27/04—Sulfides
- B01J27/047—Sulfides with chromium, molybdenum, tungsten or polonium
- B01J27/051—Molybdenum
-
- 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
- B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
- B01J35/391—Physical properties of the active metal ingredient
- B01J35/394—Metal dispersion value, e.g. percentage or fraction
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01C—AMMONIA; CYANOGEN; COMPOUNDS THEREOF
- C01C1/00—Ammonia; Compounds thereof
- C01C1/02—Preparation, purification or separation of ammonia
- C01C1/04—Preparation of ammonia by synthesis in the gas phase
- C01C1/0405—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst
- C01C1/0411—Preparation of ammonia by synthesis in the gas phase from N2 and H2 in presence of a catalyst characterised by the catalyst
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Analytical Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Catalysts (AREA)
Abstract
The invention discloses a preparation method of an atomic-scale active site catalyst capable of catalyzing nitrogen and hydrogen to synthesize ammonia under mild conditions, wherein the catalyst is used for Reducing Graphene Oxide (RGO) and molybdenum disulfide (MoS) 2 ) Is a composite carrier, takes atomically dispersed platinum (Pt) as an active component, and synthesizes the Pt-MoS 2 the/RGO catalyst can significantly increase the rate of ammonia synthesis. The composite carrier has MoS 2 Strong adsorption property and good RGO conductivity, moS 2 The composite carrier has the advantages that the composite carrier is deposited on the RGO surface in a multilayer form, a continuous electron transmission network is formed by the RGO and the RGO, atomic-level Pt is uniformly dispersed on the composite carrier, the limit of atomic dispersion is reached, the activity and the stability of the synthetic ammonia reaction are obviously improved, the synthetic ammonia reaction can be driven under a mild condition, and the energy consumption of the traditional synthetic ammonia industry is reduced.
Description
Technical Field
The invention belongs to the field of preparation methods of synthetic ammonia catalysts, and particularly relates to a preparation method of an atomic-scale active site catalyst for catalyzing nitrogen and hydrogen to synthesize ammonia under mild conditions.
Background
The industrial synthesis of ammonia mainly depends on an energy-intensive Haber-Bosch process, which requires high-temperature (300-550 ℃) and high-pressure (15-25 MPa) operating conditions and is a process with high energy consumption and high carbon dioxide emission. In order to reduce energy consumption, synthetic ammonia was sought under mild conditions.
Currently, the mainstream ammonia synthesis technologies under mild conditions include photocatalytic synthesis of ammonia, electrocatalytic synthesis of ammonia, artificial biomimetic catalytic synthesis of ammonia, and thermocatalytic synthesis of ammonia. The technology for synthesizing ammonia by utilizing solar photocatalysis is limited by the limitations of adsorption, activation and dissociation processes of nitrogen molecules caused by the extremely high chemical stability of the nitrogen molecules, so that the yield of the ammonia synthesized by photocatalysis is low. Furthermore, nitrogen molecules are in aqueous solutionThe medium and extremely low solubility and the slow kinetic characteristics of the water oxidation reaction limit the supply of nitrogen and protons as reactants, further affecting the efficiency of photocatalytic synthesis of ammonia. The problem that a large amount of sunlight in a visible-infrared spectrum region is wasted exists in the process of synthesizing ammonia by photocatalysis, and the efficiency of a solar energy-chemical energy conversion process is generally low. The electro-catalysis synthesis of ammonia realizes the synthesis of ammonia under mild conditions by means of externally input electric energy, and has the advantages of energy consumption reduction, cleanness, no pollution and the like. Researchers hope to improve the performance of the electro-catalytic synthesis of ammonia by modifying and adding a catalyst and the like, but the electro-catalytic synthesis of ammonia is limited by competitive hydrogen evolution reaction caused by the close proximity of Hydrogen Evolution Reaction (HER) potential and nitrogen reduction potential, the ammonia production rate and Faraday current efficiency are still low, and a more efficient non-noble metal catalyst needs to be developed to improve the performance of the electro-catalytic synthesis of ammonia in the future. The artificial biomimetic catalytic synthesis of ammonia is to simulate the Fe-Mo synergistic catalytic mechanism of biological nitrogen fixation enzyme in nature by an artificial method. Different from the traditional industrial ammonia synthesis process, the biological nitrogen fixation can be carried out under mild conditions without the limitation of the high-temperature high-pressure catalytic conditions of heterogeneous thermocatalytic ammonia synthesis, so that the N is reduced by preferentially combining a hydrogenation mechanism 2 Activation energy barrier of, and evasion
-restrictions of Evans-Polanyi (BEP) relationship. However, as the biological nitrogen fixation mechanism is not completely understood, the efficiency of synthesizing ammonia by artificially simulating the biological nitrogen fixation mechanism under mild conditions is still low, and the method is not suitable for large-scale popularization and application. In the traditional thermocatalysis process, a transition metal catalyst is mostly used for catalyzing nitrogen and hydrogen to synthesize ammonia, but N 2 Molecular dissociation is limited by the BEP relationship, N 2 There is a conflicting relationship between the molecular activation barrier and the adsorption energy of reactive intermediate species, and an ideal ammonia synthesis catalyst should balance the relationship between the two, near the top of the volcano-type curve. In the process of synthesizing ammonia by thermal catalysis, the limitation of BEP relation needs to be broken, and the high-efficiency synthesis of ammonia can be realized.
Disclosure of Invention
The inventionAims to overcome the defects of the prior art and provide a preparation method of an atomic-scale active site catalyst for catalyzing nitrogen and hydrogen to synthesize ammonia under mild conditions. Synthetic Pt-MoS 2 the/RGO catalyst can obviously improve the activity and stability of the synthetic ammonia reaction, so that the synthetic ammonia reaction can be driven under mild conditions.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention relates to an atomic-level active site catalyst for catalyzing nitrogen and hydrogen to synthesize ammonia under mild conditions, which comprises the following steps:
an atomic-scale active site catalyst for catalyzing nitrogen and hydrogen to synthesize ammonia under mild conditions is characterized by comprising the following steps:
step one, preparing a reduced graphene oxide carrier:
(1) Under the condition of ice-water bath at 0-4 ℃, 50-100 mL of concentrated sulfuric acid with mass fraction of 98% is slowly added into a round bottom flask under the stirring of a glass rod, and then 1.0000-2.0000 g of NaNO is slowly added 3 And 1.0000-2.0000 g of graphite powder to form a mixed solution; when the temperature of the mixed solution is reduced to 0-4 ℃, slowly adding 6.0000-12.0000 g of potassium permanganate in three times, after adding the potassium permanganate in the last time, reacting in an ice-water bath at 0-4 ℃ for 20-40 min at constant temperature, oxidizing graphite powder to form a sulfuric acid-graphite interlayer compound, and marking the obtained mixed solution as a mixed solution A; removing the ice water bath to ensure that the mixed solution A continues to react for 1 to 3 hours after the temperature is raised to 20 to 25 ℃, deeply oxidizing the sulfuric acid-graphite interlayer compound, and marking the obtained mixed solution as a mixed solution B;
(2) Adding 60-100 mL of deionized water into the mixed solution B, gradually increasing the temperature of the mixed solution B to 96-100 ℃ by utilizing the heat released when the residual concentrated sulfuric acid added in the step (1) reacts with water, and then reacting for 0.3-0.7 h under the stirring of a glass rod to enable a sulfuric acid-graphite interlayer compound in the mixed solution B to generate hydrolysis reaction; adding 5-25 mL of H with the mass fraction of 10-30% into the hydrolyzed mixed solution 2 O 2 Removing excessive potassium permanganate from the solution to obtain a solution which is marked as a mixed solution C; then mixing the mixed solution CTransferring the sample to a high-speed centrifuge with the speed of 8000-12000 r/min for centrifugation for 10-40 min, pouring out the supernatant of the centrifuge tube, and obtaining the precipitate at the lower layer of the centrifuge tube as graphene oxide;
(3) Transferring graphene oxide on the lower layer of the centrifugal tube into a beaker, sequentially adding 60-100 mL of deionized water and 30-60 mL of pure hydrazine hydrate into the beaker, and uniformly stirring by using a glass rod to obtain a mixed solution D; placing the mixed solution D in a vacuum drying oven at 100-140 ℃ for reacting for 8-10 h to obtain an RGO carrier, washing the RGO carrier with deionized water for three times, removing residual hydrazine hydrate, then placing the RGO carrier in the vacuum drying oven again, and drying the RGO carrier at 100-140 ℃ for 1-3 h to obtain a pure RGO carrier;
step two, moS 2 Preparation of/RGO Complex Carrier:
(1) Placing 0.0024-0.0048 g of pure RGO carrier in a beaker, adding 60-100 mL of deionized water, and ultrasonically treating for 10-30 min by using an ultrasonic cleaner to completely dissolve the pure RGO to obtain RGO mixed solution;
(2) Adding 0.0242g of sodium molybdate into the RGO solution and stirring uniformly by using a glass rod to obtain an RGO mixed solution dissolved with the sodium molybdate; dissolving 0.0076-0.0380 g of thiourea in 40-60 mL of deionized water to obtain a thiourea solution; slowly dripping the thiourea solution into an RGO mixed solution dissolved with sodium molybdate by using a dropper, uniformly stirring by using a glass rod, adding a hydrochloric acid solution with the mass fraction of 10% to adjust the pH value to be 0.1-7, and obtaining a mixed solution E;
(3) Transferring the mixed solution E into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and growing MoS at the temperature of 100-250 DEG C 2 Taking out after growing for 18-30 h, transferring to a high-speed centrifuge with 8000-12000 r/min for centrifugation for 10-40 min, pouring out the supernatant of the centrifuge tube, wherein the sediment at the lower layer of the centrifuge tube is MoS 2 /RGO, moS 2 the/RGO product is washed three times by deionized water and is dried for 1 to 3 hours in a vacuum drying oven at the temperature of between 100 and 140 ℃ to obtain MoS 2 an/RGO complex carrier;
step three, pt-MoS 2 Preparation of/RGO catalyst:
(1) Mixing 0.0200-0.0800 gMoS 2 Placing the/RGO composite carrier in a beaker, adding 60-100 mL of the composite carrier for deionizationSub-water is treated by ultrasonic for 10 to 30min by an ultrasonic cleaner to ensure that MoS is generated 2 the/RGO is completely dissolved to obtain a mixed solution F;
(2) Mixing 0.0020-0.0100 g H 2 PtCl 6 ·6H 2 Adding O into 60-100 mL of mixed solution F, uniformly stirring, dropwise adding 60-100mL of 0.5mol/L sodium borohydride solution into the mixed solution F by using a dropper at the temperature of 20-25 ℃, uniformly stirring by using a glass rod while dropwise adding, transferring the obtained mixture after reaction into a high-speed centrifuge of 8000-12000 r/min, centrifuging for 10-40 min, pouring out the supernatant of a centrifuge tube, wherein the lower-layer substance of the centrifuge tube is Pt-MoS 2 an/RGO catalyst; mixing Pt-MoS 2 The RGO catalyst is respectively washed by deionized water and absolute ethyl alcohol with the mass fraction of 10-30% for three times and then is placed in a vacuum drying oven with the temperature of 160-240 ℃ for drying for 2-5 h to obtain pure Pt-MoS 2 an/RGO catalyst.
Compared with the prior art, the invention has the following advantages:
(1) Atomic-scale dispersion of Pt. MoS 2 The active site of (A) is located only in MoS 2 The edges of the sheet layer and the surface of the sheet layer show chemical inertness, which limits the wide application of the sheet layer, and in order to further increase the number of active sites and increase the performance of ammonia synthesis, atomically dispersed Pt is introduced. When the Pt dispersion degree reaches the atom size, the properties such as surface free energy, quantum size effect, unsaturated coordination environment, metal-carrier interaction and the like can be caused to change sharply, and the synthetic ammonia performance of the catalyst is improved remarkably.
(2) Space confinement effect of the catalyst carrier. MoS 2 The edge of the graphene oxide has a large number of dangling bonds which can provide more adsorption sites for catalytic reaction, and the defect existing on the surface of the reduced graphene oxide is MoS 2 Provides a site for MoS growth 2 Growing on the surface of the reduced graphene oxide. The carbon material is added into a hydrothermal reaction system, a steric hindrance effect can be formed in a solution, and MoS can be inhibited 2 Stacking of nanosheets while also spatially confining MoS 2 The aggregation of the nano sheets further improves the specific surface area of the material, generates more active sites and realizes the high-efficiency catalytic synthesis of ammonia under mild conditions.
Detailed Description
In order to make the description of the invention easier to understand, the following specific examples are set forth, but the scope of the claims of the present invention is not limited by these examples. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
The invention relates to an atomic-scale active site catalyst for catalyzing nitrogen and hydrogen to synthesize ammonia under mild conditions, which comprises the following steps:
step one, preparing a reduced graphene oxide carrier:
(1) Under the condition of ice-water bath at 0-4 ℃, 50-100 mL of concentrated sulfuric acid with mass fraction of 98% is slowly added into a round bottom flask under the stirring of a glass rod, and then 1.0000-2.0000 g of NaNO is slowly added 3 And 1.0000-2.0000 g of graphite powder to form a mixed solution; when the temperature of the mixed solution is reduced to 0-4 ℃, slowly adding 6.0000-12.0000 g of potassium permanganate in three times, after adding the potassium permanganate in the last time, reacting in an ice-water bath at 0-4 ℃ for 20-40 min at constant temperature, oxidizing graphite powder to form a sulfuric acid-graphite interlayer compound, and marking the obtained mixed solution as a mixed solution A; removing the ice water bath to ensure that the mixed solution A continues to react for 1 to 3 hours after the temperature is raised to 20 to 25 ℃, deeply oxidizing the sulfuric acid-graphite interlayer compound, and marking the obtained mixed solution as a mixed solution B.
(2) Adding 60-100 mL of deionized water into the mixed solution B, gradually increasing the temperature of the mixed solution B to 96-100 ℃ by utilizing the heat released when the residual concentrated sulfuric acid added in the step (1) reacts with water, and then reacting for 0.3-0.7 h under the stirring of a glass rod to enable the sulfuric acid-graphite interlayer compound in the mixed solution B to generate hydrolysis reaction. Adding 5-25 mL of H with the mass fraction of 10-30% into the hydrolyzed mixed solution 2 O 2 Removing excessive potassium permanganate from the solution to obtain a solution which is marked as a mixed solution C; and then transferring the mixed solution C to a high-speed centrifuge with the speed of 8000-12000 r/min for centrifugation for 10-40 min, pouring out the supernatant of the centrifuge tube, and obtaining the precipitate at the lower layer of the centrifuge tube, namely the graphene oxide.
(3) Transferring graphene oxide on the lower layer of the centrifugal tube into a beaker, sequentially adding 60-100 mL of deionized water and 30-60 mL of pure hydrazine hydrate into the beaker, and uniformly stirring by using a glass rod to obtain a mixed solution D; and (3) placing the mixed solution D in a vacuum drying oven at 100-140 ℃ for reacting for 8-10 h to obtain an RGO (reduced graphene oxide) carrier, washing the RGO carrier with deionized water for three times, removing residual hydrazine hydrate, then placing the RGO carrier in the vacuum drying oven again, and drying the RGO carrier for 1-3 h at 100-140 ℃ to obtain the pure RGO carrier.
Step two, moS 2 Preparation of/RGO Complex Carrier:
(1) Placing 0.0024-0.0048 g of pure RGO carrier in a beaker, adding 60-100 mL of deionized water, and ultrasonically treating for 10-30 min by an ultrasonic cleaner to completely dissolve the pure RGO to obtain RGO mixed solution.
(2) Adding 0.0242g of sodium molybdate into the RGO solution and stirring uniformly by using a glass rod to obtain an RGO mixed solution dissolved with the sodium molybdate; dissolving 0.0076-0.0380 g of thiourea in 40-60 mL of deionized water to obtain a thiourea solution; the thiourea solution is slowly dripped into the RGO mixed solution dissolved with sodium molybdate by a dropper, and after being uniformly stirred by a glass rod, the hydrochloric acid solution with the mass fraction of 10 percent is added to adjust the pH value to be 0.1 to 7, so as to obtain a mixed solution E.
(3) Transferring the mixed solution E into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and growing MoS at the temperature of 100-250 DEG C 2 Taking out after growing for 18-30 h, transferring the product to a high-speed centrifuge with 8000-12000 r/min for centrifugation for 10-40 min, pouring out the supernatant of the centrifuge tube, and obtaining the sediment at the lower layer of the centrifuge tube as MoS 2 /RGO, moS 2 The RGO product is washed three times by deionized water and is dried for 1 to 3 hours in a vacuum drying oven at the temperature of between 100 and 140 ℃ to obtain MoS 2 a/RGO complex carrier.
Step three, pt-MoS 2 Preparation of/RGO catalyst:
(1) Mixing 0.0200-0.0800 gMoS 2 Placing the/RGO composite carrier in a beaker, adding 60-100 mL deionized water, and ultrasonically treating for 10-30 min by using an ultrasonic cleaner to enable MoS 2 the/RGO was completely dissolved to obtain a mixed solution F.
(2) Mixing 0.0020-0.0100 g H 2 PtCl 6 ·6H 2 Adding O into 60-100 mL of mixed solution F, uniformly stirring, dropwise adding 60-100mL of 0.5mol/L sodium borohydride solution into the mixed solution F by using a dropper at the temperature of 20-25 ℃, uniformly stirring by using a glass rod while dropwise adding, transferring the obtained mixture after reaction into a high-speed centrifuge of 8000-12000 r/min, centrifuging for 10-40 min, pouring out the supernatant of a centrifuge tube, wherein the lower-layer substance of the centrifuge tube is Pt-MoS 2 an/RGO catalyst; mixing Pt-MoS 2 The RGO catalyst is respectively washed by deionized water and absolute ethyl alcohol with the mass fraction of 10-30% for three times and then is placed in a vacuum drying oven with the temperature of 160-240 ℃ for drying for 2-5 h to obtain pure Pt-MoS 2 an/RGO catalyst.
Example 1
Step one, preparing a reduced graphene oxide carrier:
(1) Under the condition of ice-water bath at 0 ℃, 50mL of concentrated sulfuric acid with the mass fraction of 98% is slowly added into a round-bottom flask under stirring of a glass rod, and then 1.0000g of NaNO is slowly added 3 And 1.0000g of graphite powder to form a mixed solution; after the temperature of the mixed solution is reduced to 0 ℃, slowly adding 6.0000g of potassium permanganate in three times, reacting in an ice-water bath at 0 ℃ for 20min at constant temperature after adding the potassium permanganate in the last time, oxidizing graphite powder to form a sulfuric acid-graphite interlayer compound, and marking the obtained mixed solution as a mixed solution A; and removing the ice water bath, raising the temperature of the mixed solution A to 20 ℃, continuing to react for 1h, deeply oxidizing the sulfuric acid-graphite interlayer compound, and recording the obtained mixed solution as a mixed solution B.
(2) Adding 60mL of deionized water into the mixed solution B, gradually increasing the temperature of the mixed solution B to 96 ℃ by using the heat released when the residual concentrated sulfuric acid added in the step (1) reacts with water, and then reacting for 0.3h under the stirring of a glass rod to enable the sulfuric acid-graphite interlayer compound in the mixed solution B to generate hydrolysis reaction. Adding 5mL of H with the mass fraction of 10% into the mixed solution after hydrolysis 2 O 2 Removing excessive potassium permanganate from the solution to obtain a solution which is marked as a mixed solution C; then transferring the mixed solution C to a high-speed centrifuge with 8000r/min for centrifugation for 10min, pouring out the supernatant of the centrifuge tube, and collecting the precipitate at the lower layer of the centrifuge tubeNamely the graphene oxide.
(3) Transferring graphene oxide on the lower layer of the centrifugal tube into a beaker, sequentially adding 60mL of deionized water and 30mL of pure hydrazine hydrate into the beaker, and uniformly stirring by using a glass rod to obtain a mixed solution D; and (3) placing the mixed solution D in a vacuum drying oven at 100 ℃ for reacting for 8h to obtain an RGO (reduced graphene oxide) carrier, washing the RGO carrier with deionized water for three times, removing residual hydrazine hydrate, then placing the RGO carrier in the vacuum drying oven again, and drying the RGO carrier for 1h at 100 ℃ to obtain the pure RGO carrier.
Step two, moS 2 Preparation of/RGO Complex Carrier:
(1) 0.0024g of pure RGO carrier is placed in a beaker, 60mL of deionized water is added, and ultrasonic treatment is carried out for 10min by an ultrasonic cleaner to completely dissolve the pure RGO, thus obtaining an RGO mixed solution.
(2) Adding 0.0242g of sodium molybdate into the RGO solution and stirring uniformly by using a glass rod to obtain an RGO mixed solution dissolved with the sodium molybdate; dissolving 0.0076g of thiourea in 40mL of deionized water to obtain a thiourea solution; the thiourea solution is slowly dripped into an RGO mixed solution dissolved with sodium molybdate by a dropper, and after being uniformly stirred by a glass rod, a hydrochloric acid solution with the mass fraction of 10% is added to adjust the pH value to 0.1, so as to obtain a mixed solution E.
(3) Transferring the mixed solution E into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and growing MoS at the temperature of 100 DEG C 2 Taking out after growing for 18h, transferring to a 8000r/min high-speed centrifuge for centrifuging for 10min, pouring out the supernatant of the centrifuge tube, wherein the sediment at the lower layer of the centrifuge tube is MoS 2 /RGO product, moS 2 the/RGO product is washed three times by deionized water and is dried for 1h in a vacuum drying oven at 100 ℃ to obtain MoS 2 a/RGO complex carrier.
Step three, pt-MoS 2 Preparation of/RGO catalyst:
(1) Mixing 0.0200gMoS 2 Placing the/RGO composite carrier in a beaker, adding 60mL of deionized water, and ultrasonically treating for 10min by using an ultrasonic cleaner to enable MoS 2 the/RGO was completely dissolved to obtain a mixed solution F.
(2) Mixing 0.0020g H 2 PtCl 6 ·6H 2 O addition60mL of the mixed solution F is uniformly stirred, 60mL of 0.5mol/L sodium borohydride solution is dropwise added into the mixed solution F by a dropper at 20 ℃, a glass rod is uniformly stirred while the 60mL of 0.5mol/L sodium borohydride solution is dropwise added, the obtained mixture after reaction is transferred into a 8000r/min high-speed centrifuge for centrifugation for 10min, supernatant of a centrifuge tube is poured off, and the lower substance of the centrifuge tube is Pt-MoS 2 an/RGO catalyst; mixing Pt-MoS 2 the/RGO catalyst is respectively washed by deionized water and 10 percent of absolute ethyl alcohol for three times and then is dried in a vacuum drying oven at 160 ℃ for 2 hours to obtain pure Pt-MoS 2 an/RGO catalyst.
Pt-MoS 2 Activity evaluation of/RGO catalyst:
the activity of the catalyst is measured in a high-temperature high-pressure activity measuring device, and 2mg of the catalyst is placed in the isothermal zone of the reaction. The catalyst was activated in the reaction apparatus at 300 ℃ for 2h and then stabilized under the test conditions for 2h. The measurement conditions were: the temperature is 250 ℃, the pressure is 5MPa, and the reaction gas N 2 ：H 2 Is 1:3 (volume ratio), airspeed 15000h -1 . The ammonia concentration in the outlet reaction gas was 131.4mmol g as measured by chemical absorption cat -1 h -1 The catalytic synthesis ammonia activity of the atomic-level active site catalyst is not obviously reduced within 54 h. The prepared atomic-level active site ammonia synthesis catalyst has better catalytic activity and stability under mild conditions.
Example 2
Step one, preparing a reduced graphene oxide carrier:
(1) Under the condition of ice-water bath at the temperature of 2 ℃, 60mL of concentrated sulfuric acid with the mass fraction of 98 percent is slowly added into a round-bottom flask under the stirring of a glass rod, and then 1.5000g of NaNO is slowly added 3 And 1.5000g of graphite powder to form a mixed solution; after the temperature of the mixed solution is reduced to 2 ℃, slowly adding 9.0000g of potassium permanganate in three times, reacting in an ice-water bath at 2 ℃ for 30min at constant temperature after adding the potassium permanganate in the last time, oxidizing graphite powder to form a sulfuric acid-graphite interlayer compound, and marking the obtained mixed solution as a mixed solution A; removing the ice water bath to raise the temperature of the mixed solution A to 22 ℃, continuing to react for 1.5h, and deeply oxidizing the sulfuric acid-graphite interlayer compoundThe resulting mixed solution was designated as mixed solution B.
(2) And (2) adding 70mL of deionized water into the mixed solution B, gradually raising the temperature of the mixed solution B to 98 ℃ by utilizing the heat released when the residual concentrated sulfuric acid added in the step (1) reacts with water, and then reacting for 0.5 hour under the stirring of a glass rod to perform hydrolysis reaction on the sulfuric acid-graphite intercalation compound in the mixed solution B. Adding 10mL of H with the mass fraction of 15% into the mixed solution after hydrolysis 2 O 2 Removing excessive potassium permanganate from the solution to obtain a solution which is marked as a mixed solution C; and then transferring the mixed solution C to a 10000r/min high-speed centrifuge for centrifugation for 20min, pouring out the supernatant of the centrifuge tube, and obtaining the precipitate at the lower layer of the centrifuge tube, namely the graphene oxide.
(3) Transferring graphene oxide on the lower layer of the centrifugal tube into a beaker, sequentially adding 70mL of deionized water and 45mL of pure hydrazine hydrate into the beaker, and uniformly stirring by using a glass rod to obtain a mixed solution D; and (3) placing the mixed solution D in a vacuum drying oven at 120 ℃ for reaction for 9h to obtain an RGO (reduced graphene oxide) carrier, washing the RGO carrier with deionized water for three times, removing residual hydrazine hydrate, then placing the RGO carrier in the vacuum drying oven again, and drying the RGO carrier at 120 ℃ for 2h to obtain a pure RGO carrier.
Step two, moS 2 Preparation of/RGO Complex Carrier:
(1) 0.0036g of pure RGO carrier was placed in a beaker, 70mL of deionized water was added, and the pure RGO was completely dissolved by sonication for 20min with an ultrasonic cleaner to obtain an RGO mixed solution.
(2) Adding 0.0242g of sodium molybdate into the RGO solution and stirring uniformly by using a glass rod to obtain an RGO mixed solution dissolved with the sodium molybdate; dissolving 0.0152g of thiourea in 50mL of deionized water to obtain a thiourea solution; and slowly dripping the thiourea solution into the RGO mixed solution dissolved with sodium molybdate by using a dropper, uniformly stirring by using a glass rod, adding a hydrochloric acid solution with the mass fraction of 10%, and adjusting the pH value to 3 to obtain a mixed solution E.
(3) Transferring the mixed solution E into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and growing MoS at the temperature of 150 DEG C 2 Taking out after growing for 24h, and centrifuging for 20min in a high-speed centrifuge of 10000r/minThen pouring out the supernatant of the centrifugal tube, and obtaining the sediment at the lower layer of the centrifugal tube as MoS 2 /RGO, moS 2 The RGO product is washed three times by deionized water and is dried in a vacuum drying oven at 120 ℃ for 1.5h to obtain MoS 2 a/RGO complex carrier.
Step three, pt-MoS 2 Preparation of/RGO catalyst:
(1) Mixing 0.0400gMoS 2 Placing the/RGO composite carrier in a beaker, adding 70mL deionized water, and ultrasonically treating for 20min with an ultrasonic cleaner to obtain MoS 2 the/RGO was completely dissolved to obtain a mixed solution F.
(2) 0.0040g H 2 PtCl 6 ·6H 2 Adding O into 70mL of mixed solution F, uniformly stirring, dropwise adding 70mL of 0.5mol/L sodium borohydride solution into the mixed solution F by using a dropper at 22 ℃, uniformly stirring by using a glass rod while dropwise adding, transferring the obtained mixture after reaction into a 10000r/min high-speed centrifuge, centrifuging for 20min, pouring out the supernatant of a centrifuge tube, wherein the lower-layer substance of the centrifuge tube is Pt-MoS 2 an/RGO catalyst; mixing Pt-MoS 2 The RGO catalyst is respectively washed by deionized water and 20 percent absolute ethyl alcohol for three times and then is placed in a vacuum drying oven at 180 ℃ for drying for 3 hours to obtain pure Pt-MoS 2 an/RGO catalyst.
Pt-MoS 2 Activity evaluation of/RGO catalyst:
the activity of the catalyst is measured in a high-temperature high-pressure activity measuring device, and 2mg of the catalyst is placed in the isothermal zone of the reaction. The catalyst was activated in the reaction apparatus at 300 ℃ for 2h and then stabilized under the test conditions for 2h. The measurement conditions were: the temperature is 250 ℃, the pressure is 5MPa, and the reaction gas N 2 ：H 2 Is 1:3 (volume ratio), airspeed 15000h -1 . The ammonia concentration in the outlet reaction gas was 742.6mmol g measured by chemical absorption cat -1 h -1 The catalytic synthesis ammonia activity of the atomic-level active site catalyst is not obviously reduced within 54 h. The prepared atomic-level active site ammonia synthesis catalyst has better catalytic activity and stability under mild conditions.
Example 3
Step one, preparing a reduced graphene oxide carrier:
(1) Under the condition of ice-water bath at 3 ℃, 90mL of concentrated sulfuric acid with the mass fraction of 98 percent is slowly added into a round-bottom flask under stirring of a glass rod, and then 1.8000g of NaNO is slowly added 3 1.8000g graphite powder to form a mixed solution; when the temperature of the mixed solution is reduced to 3 ℃, slowly adding 10.0000g of potassium permanganate in three times, reacting in an ice-water bath at 3 ℃ for 35min at constant temperature after adding the potassium permanganate for the last time, oxidizing graphite powder to form a sulfuric acid-graphite interlayer compound, and marking the obtained mixed solution as a mixed solution A; and removing the ice water bath to ensure that the mixed solution A continues to react for 2.5 hours after the temperature is raised to 24 ℃, deeply oxidizing the sulfuric acid-graphite interlayer compound, and recording the obtained mixed solution as a mixed solution B.
(2) And (2) adding 90mL of deionized water into the mixed solution B, gradually increasing the temperature of the mixed solution B to 99 ℃ by utilizing the heat released when the residual concentrated sulfuric acid added in the step (1) reacts with water, and then reacting for 0.6h under the stirring of a glass rod to perform hydrolysis reaction on the sulfuric acid-graphite interlayer compound in the mixed solution B. Adding 20mL of H with the mass fraction of 28% into the mixed solution after hydrolysis 2 O 2 Removing excessive potassium permanganate from the solution to obtain a solution which is marked as a mixed solution C; and then transferring the mixed solution C to a 11000r/min high-speed centrifuge for centrifugation for 30min, pouring out the supernatant of the centrifuge tube, and obtaining the precipitate at the lower layer of the centrifuge tube, namely the graphene oxide.
(3) Transferring graphene oxide on the lower layer of the centrifugal tube into a beaker, sequentially adding 90mL of deionized water and 50mL of pure hydrazine hydrate into the beaker, and uniformly stirring by using a glass rod to obtain a mixed solution D; and (3) placing the mixed solution D in a vacuum drying oven at 130 ℃ for reaction for 9.5h to obtain an RGO (reduced graphene oxide) carrier, washing the RGO carrier with deionized water for three times, removing residual hydrazine hydrate, then placing the RGO carrier in the vacuum drying oven again, and drying the RGO carrier at 130 ℃ for 2.5h to obtain a pure RGO carrier.
Step two, moS 2 Preparation of/RGO composite Carrier:
(1) 0.0040g of pure RGO carrier is placed in a beaker, 90mL of deionized water is added, and the pure RGO is completely dissolved by ultrasonic treatment for 28min with an ultrasonic cleaner, so as to obtain an RGO mixed solution.
(2) Adding 0.0242g of sodium molybdate into the RGO solution and stirring uniformly by using a glass rod to obtain an RGO mixed solution dissolved with the sodium molybdate; dissolving 0.0290g of thiourea in 58mL of deionized water to obtain a thiourea solution; and slowly dripping the thiourea solution into the RGO mixed solution dissolved with sodium molybdate by using a dropper, uniformly stirring by using a glass rod, adding a hydrochloric acid solution with the mass fraction of 10% to adjust the pH value to 5, and thus obtaining a mixed solution E.
(3) Transferring the mixed solution E into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and growing MoS at 220 DEG C 2 Taking out after growing for 26h, transferring to a 11000r/min high-speed centrifuge for centrifuging for 35min, pouring out supernatant of a centrifuge tube, wherein sediment at the lower layer of the centrifuge tube is MoS 2 /RGO product, moS 2 the/RGO product is washed three times by deionized water and is dried for 2.5h in a vacuum drying oven at 130 ℃ to obtain MoS 2 a/RGO complex carrier.
Step three, pt-MoS 2 Preparation of/RGO catalyst:
(1) 0.0600gMoS 2 Placing the/RGO composite carrier in a beaker, adding 90mL of deionized water, and ultrasonically treating for 28min by using an ultrasonic cleaner to enable MoS 2 the/RGO was completely dissolved to obtain a mixed solution F.
(2) Mixing 0.0080g H 2 PtCl 6 ·6H 2 Adding O into 90mL of mixed solution F, uniformly stirring, dropwise adding 90mL of 0.5mol/L sodium borohydride solution into the mixed solution F by using a dropper at 24 ℃, uniformly stirring by using a glass rod while dropwise adding, transferring the obtained mixture after reaction into a 11000r/min high-speed centrifuge, centrifuging for 35min, pouring out the supernatant of a centrifuge tube, wherein the lower-layer substance of the centrifuge tube is Pt-MoS 2 an/RGO catalyst; mixing Pt-MoS 2 the/RGO catalyst is respectively washed with deionized water and 28 mass percent absolute ethyl alcohol for three times and then is placed in a vacuum drying oven at 220 ℃ for drying for 4 hours to obtain pure Pt-MoS 2 an/RGO catalyst.
Pt-MoS 2 Activity evaluation of/RGO catalyst:
the activity of the catalyst is measured in a high-temperature high-pressure activity measuring device, 2mg of the catalyst is taken and placed in the reactionThe temperature range of the isothermal zone. The catalyst was activated in the reaction apparatus at 300 ℃ for 2h and then stabilized under the test conditions for 2h. The measurement conditions were: the temperature is 250 ℃, the pressure is 5MPa, and the reaction gas N 2 ：H 2 Is 1:3 (volume ratio), airspeed 15000h -1 . The ammonia concentration in the outlet reaction gas was 631.2mmol g measured by chemical absorption cat -1 h -1 The catalytic synthesis ammonia activity of the atomic-level active site catalyst is not obviously reduced within 54 h. The prepared atomic-level active site ammonia synthesis catalyst has better catalytic activity and stability under mild conditions.
Example 4
Step one, preparing a reduced graphene oxide carrier:
(1) Under the condition of ice-water bath at 4 ℃, 100mL of concentrated sulfuric acid with the mass fraction of 98 percent is slowly added into a round-bottom flask under stirring of a glass rod, and then 2.0000g of NaNO is slowly added 3 And 2.0000g of graphite powder to form a mixed solution; after the temperature of the mixed solution is reduced to 4 ℃, slowly adding 12.0000g of potassium permanganate in three times, reacting in an ice-water bath at 4 ℃ for 40min at constant temperature after adding the potassium permanganate in the last time, oxidizing graphite powder to form a sulfuric acid-graphite interlayer compound, and marking the obtained mixed solution as a mixed solution A; and removing the ice water bath to ensure that the mixed solution A continues to react for 3 hours after the temperature is raised to 25 ℃, deeply oxidizing the sulfuric acid-graphite interlayer compound, and marking the obtained mixed solution as a mixed solution B.
(2) And (2) adding 100mL of deionized water into the mixed solution B, gradually increasing the temperature of the mixed solution B to 100 ℃ by utilizing the heat released when the residual concentrated sulfuric acid added in the step (1) reacts with water, and then reacting for 0.7h under the stirring of a glass rod to perform hydrolysis reaction on the sulfuric acid-graphite interlayer compound in the mixed solution B. Adding 25mL of H with the mass fraction of 30% into the mixed solution after hydrolysis 2 O 2 Removing excessive potassium permanganate from the solution to obtain a solution which is marked as a mixed solution C; and then transferring the mixed solution C to a high-speed centrifuge of 12000r/min for centrifugation for 40min, pouring out the supernatant of the centrifuge tube, and obtaining the precipitate at the lower layer of the centrifuge tube, namely the graphene oxide.
(3) Transferring graphene oxide on the lower layer of the centrifugal tube into a beaker, sequentially adding 100mL of deionized water and 60mL of pure hydrazine hydrate into the beaker, and uniformly stirring with a glass rod to obtain a mixed solution D; and (3) placing the mixed solution D in a vacuum drying oven at 140 ℃ for reaction for 10h to obtain an RGO (reduced graphene oxide) carrier, washing the RGO carrier with deionized water for three times, removing residual hydrazine hydrate, then placing the RGO carrier in the vacuum drying oven again, and drying the RGO carrier at 140 ℃ for 3h to obtain a pure RGO carrier.
Step two, moS 2 Preparation of/RGO Complex Carrier:
(1) 0.0048g of pure RGO carrier is placed in a beaker, 100mL of deionized water is added, and the pure RGO is completely dissolved by ultrasonic treatment for 30min with an ultrasonic cleaner, so as to obtain an RGO mixed solution.
(2) Adding 0.0242g of sodium molybdate into the RGO solution and stirring uniformly by a glass rod to obtain an RGO mixed solution in which the sodium molybdate is dissolved; dissolving 0.0380g of thiourea in 60mL of deionized water to obtain a thiourea solution, slowly dripping the thiourea solution into an RGO mixed solution dissolved with sodium molybdate by using a dropper, uniformly stirring by using a glass rod, adding a hydrochloric acid solution with the mass fraction of 10% to adjust the pH value to 7, and obtaining a mixed solution E.
(3) Transferring the mixed solution E into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and growing MoS at the temperature of 250 DEG C 2 Taking out after growing for 30h, transferring to a high-speed centrifuge of 12000r/min for centrifuging for 40min, pouring out supernatant of a centrifuge tube, wherein sediment at the lower layer of the centrifuge tube is MoS 2 /RGO product, moS 2 the/RGO product is washed three times by deionized water and is dried for 3 hours in a vacuum drying oven at the temperature of 140 ℃ to obtain MoS 2 a/RGO complex carrier.
Step three, pt-MoS 2 Preparation of the/RGO catalyst:
(1) 0.0800gMoS 2 Placing the/RGO composite carrier in a beaker, adding 100mL of deionized water, and ultrasonically treating for 30min by using an ultrasonic cleaner to enable MoS 2 the/RGO was completely dissolved to obtain a mixed solution F.
(2) Mixing 0.0100g H 2 PtCl 6 ·6H 2 O is added to 100mL of the mixed solution F and stirred uniformly, and then dropwise added thereto at 25 ℃ with a dropper100mL of 0.5mol/L sodium borohydride solution, dropwise adding and uniformly stirring by using a glass rod, transferring the obtained mixture after reaction into a high-speed centrifuge of 12000r/min for centrifuging for 40min, pouring off the supernatant of a centrifuge tube, wherein the substance at the lower layer of the centrifuge tube is Pt-MoS 2 an/RGO catalyst; mixing Pt-MoS 2 the/RGO catalyst is respectively washed by deionized water and absolute ethyl alcohol with the mass fraction of 30 percent for three times and then is placed in a vacuum drying oven with the temperature of 240 ℃ for drying for 5 hours to obtain pure Pt-MoS 2 an/RGO catalyst.
Pt-MoS 2 Activity evaluation of/RGO catalyst:
the activity of the catalyst is measured in a high-temperature high-pressure activity measuring device, and 2mg of the catalyst is placed in the isothermal zone of the reaction. The catalyst was activated in the reaction apparatus at 300 ℃ for 2h and then stabilized under the test conditions for 2h. The measurement conditions were: the temperature is 250 ℃, the pressure is 5MPa, and the reaction gas N 2 ：H 2 Is 1:3 (volume ratio), airspeed 15000h -1 . The concentration of ammonia in the outlet reaction gas was 398.1mmol g measured by chemical absorption cat -1 h -1 The catalytic synthesis ammonia activity of the atomic-level active site catalyst is not obviously reduced within 54 h. The prepared atomic-level active site ammonia synthesis catalyst has better catalytic activity and stability under mild conditions.
From the above 4 examples, it can be seen that the invention prepares Pt-MoS as an ammonia catalyst synthesized by atomic-scale active sites under mild conditions 2 the/RGO has excellent performance, higher synthetic ammonia activity and stability.
The above examples are provided for the purpose of describing the present invention only and are not intended to limit the scope of the present invention. The scope of the invention is to be determined by the appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.
Claims (1)
1. An atomic-scale active site catalyst for catalyzing nitrogen and hydrogen to synthesize ammonia under mild conditions is characterized by comprising the following steps:
step one, preparing a reduced graphene oxide carrier:
(1) Under the condition of ice-water bath at 0-4 ℃, 50-100 mL of concentrated sulfuric acid with mass fraction of 98% is slowly added into a round bottom flask under the stirring of a glass rod, and then 1.0000-2.0000 g of NaNO is slowly added 3 And 1.0000-2.0000 g of graphite powder to form a mixed solution; when the temperature of the mixed solution is reduced to 0-4 ℃, slowly adding 6.0000-12.0000 g of potassium permanganate in three times, after adding the potassium permanganate in the last time, reacting in an ice-water bath at 0-4 ℃ for 20-40 min at constant temperature, oxidizing graphite powder to form a sulfuric acid-graphite interlayer compound, and marking the obtained mixed solution as a mixed solution A; removing the ice water bath to ensure that the mixed solution A continues to react for 1 to 3 hours after the temperature is raised to 20 to 25 ℃, deeply oxidizing the sulfuric acid-graphite interlayer compound, and marking the obtained mixed solution as a mixed solution B;
(2) Adding 60-100 mL of deionized water into the mixed solution B, gradually raising the temperature of the mixed solution B to 96-100 ℃ by utilizing the heat released when the residual concentrated sulfuric acid added in the step (1) reacts with water, and then reacting for 0.3-0.7 h under the stirring of a glass rod to perform hydrolysis reaction on the sulfuric acid-graphite interlayer compound in the mixed solution B; adding 5-25 mL of H with the mass fraction of 10-30% into the hydrolyzed mixed solution 2 O 2 Removing excessive potassium permanganate from the solution to obtain a solution which is marked as a mixed solution C; then transferring the mixed solution C into a high-speed centrifuge with the speed of 8000-12000 r/min for centrifugation for 10-40 min, pouring out the supernatant of the centrifuge tube, and obtaining the precipitate at the lower layer of the centrifuge tube as graphene oxide;
(3) Transferring graphene oxide on the lower layer of the centrifugal tube into a beaker, sequentially adding 60-100 mL of deionized water and 30-60 mL of pure hydrazine hydrate into the beaker, and uniformly stirring by using a glass rod to obtain a mixed solution D; placing the mixed solution D in a vacuum drying oven at 100-140 ℃ for reacting for 8-10 h to obtain an RGO carrier, washing the RGO carrier with deionized water for three times, removing residual hydrazine hydrate, then placing the RGO carrier in the vacuum drying oven again, and drying the RGO carrier at 100-140 ℃ for 1-3 h to obtain a pure RGO carrier;
step two, moS 2 Preparation of/RGO Complex Carrier:
(1) Placing 0.0024-0.0048 g of pure RGO carrier in a beaker, adding 60-100 mL of deionized water, and carrying out ultrasonic treatment for 10-30 min by using an ultrasonic cleaner to completely dissolve the pure RGO to obtain an RGO mixed solution;
(2) Adding 0.0242g of sodium molybdate into the RGO solution and stirring uniformly by a glass rod to obtain an RGO mixed solution in which the sodium molybdate is dissolved; dissolving 0.0076-0.0380 g of thiourea in 40-60 mL of deionized water to obtain a thiourea solution; slowly dripping the thiourea solution into an RGO mixed solution dissolved with sodium molybdate by using a dropper, uniformly stirring by using a glass rod, adding a hydrochloric acid solution with the mass fraction of 10% to adjust the pH value to be 0.1-7, and obtaining a mixed solution E;
(3) Transferring the mixed solution E into a stainless steel reaction kettle with a polytetrafluoroethylene lining, and growing MoS at the temperature of 100-250 DEG C 2 Taking out after growing for 18-30 h, transferring to a high-speed centrifuge with 8000-12000 r/min for centrifugation for 10-40 min, pouring out the supernatant of the centrifuge tube, wherein the sediment at the lower layer of the centrifuge tube is MoS 2 /RGO, moS 2 the/RGO product is washed three times by deionized water and is dried for 1 to 3 hours in a vacuum drying oven at the temperature of between 100 and 140 ℃ to obtain MoS 2 an/RGO complex carrier;
step three, pt-MoS 2 Preparation of the/RGO catalyst:
(1) Mixing 0.0200-0.0800 gMoS 2 Placing the/RGO composite carrier in a beaker, adding 60-100 mL deionized water, and ultrasonically treating for 10-30 min by using an ultrasonic cleaner to enable MoS 2 the/RGO is completely dissolved to obtain a mixed solution F;
(2) Mixing 0.0020-0.0100 g H 2 PtCl 6 ·6H 2 Adding O into 60-100 mL of mixed solution F, uniformly stirring, dropwise adding 60-100mL of 0.5mol/L sodium borohydride solution into the mixed solution F by using a dropper at the temperature of 20-25 ℃, uniformly stirring by using a glass rod while dropwise adding, transferring the obtained mixture after reaction into a high-speed centrifuge of 8000-12000 r/min, centrifuging for 10-40 min, pouring out the supernatant of a centrifuge tube, wherein the lower-layer substance of the centrifuge tube is Pt-MoS 2 an/RGO catalyst; mixing Pt-MoS 2 the/RGO catalyst is respectively washed by deionized water and 10 to 30 mass percent of absolute ethyl alcohol for three times and then is dried in a vacuum drying oven at 160 to 240 ℃ for 2 to 5 hours to obtain pure Pt-MoS 2 /RGO catalyst, then to saidPt-MoS 2 Perrgo catalyst Activity valency: the activity of the catalyst is measured in a high-temperature high-pressure activity measuring device, 2mg of the catalyst is placed in an isothermal zone of the reaction, the catalyst is activated for 2 hours at 300 ℃ in the reaction device, and then the catalyst is stabilized for 2 hours under the test condition; the measurement conditions were: the temperature is 250 ℃, the pressure is 5MPa, and the reaction gas N 2 ：H 2 Is 1:3 airspeed of 15000h -1 The Pt-MoS 2 The catalytic ammonia synthesis activity of the/RGO catalyst is not obviously reduced within 54 h.
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| CN113403643B (en) * | 2021-05-25 | 2022-05-13 | 杭州师范大学 | Fe2/MoS2 electrocatalyst, preparation method and application |
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