CN110935444A - Method for preparing precious metal alloy/reduced graphene oxide composite material - Google Patents
Method for preparing precious metal alloy/reduced graphene oxide composite material Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 128
- 229910021389 graphene Inorganic materials 0.000 title claims abstract description 127
- 239000002131 composite material Substances 0.000 title claims abstract description 63
- 238000000034 method Methods 0.000 title claims abstract description 39
- 229910000923 precious metal alloy Inorganic materials 0.000 title claims description 10
- 239000007864 aqueous solution Substances 0.000 claims abstract description 222
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 117
- 238000006243 chemical reaction Methods 0.000 claims abstract description 83
- TVMXDCGIABBOFY-UHFFFAOYSA-N octane Chemical compound CCCCCCCC TVMXDCGIABBOFY-UHFFFAOYSA-N 0.000 claims abstract description 56
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- 229910045601 alloy Inorganic materials 0.000 claims abstract description 27
- 239000000956 alloy Substances 0.000 claims abstract description 27
- 239000002243 precursor Substances 0.000 claims abstract description 25
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- 229910000510 noble metal Inorganic materials 0.000 claims abstract description 16
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- 230000005514 two-phase flow Effects 0.000 claims abstract description 7
- 229910021645 metal ion Inorganic materials 0.000 claims description 38
- SQGYOTSLMSWVJD-UHFFFAOYSA-N silver(I) nitrate Inorganic materials [Ag+].[O-]N(=O)=O SQGYOTSLMSWVJD-UHFFFAOYSA-N 0.000 claims description 37
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- 238000002360 preparation method Methods 0.000 claims description 14
- 238000002156 mixing Methods 0.000 claims description 12
- 239000000243 solution Substances 0.000 claims description 10
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- 229910003603 H2PdCl4 Inorganic materials 0.000 claims description 8
- 229910002621 H2PtCl6 Inorganic materials 0.000 claims description 7
- 239000008346 aqueous phase Substances 0.000 claims description 6
- 239000012071 phase Substances 0.000 claims description 6
- 229910002666 PdCl2 Inorganic materials 0.000 claims description 5
- PIBWKRNGBLPSSY-UHFFFAOYSA-L palladium(II) chloride Chemical compound Cl[Pd]Cl PIBWKRNGBLPSSY-UHFFFAOYSA-L 0.000 claims description 5
- 229910003244 Na2PdCl4 Inorganic materials 0.000 claims description 4
- 239000000463 material Substances 0.000 claims description 4
- 229910002093 potassium tetrachloropalladate(II) Inorganic materials 0.000 claims description 4
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- 230000009467 reduction Effects 0.000 claims description 3
- 239000000126 substance Substances 0.000 claims description 3
- 239000012295 chemical reaction liquid Substances 0.000 claims description 2
- ORTQZVOHEJQUHG-UHFFFAOYSA-L copper(II) chloride Chemical compound Cl[Cu]Cl ORTQZVOHEJQUHG-UHFFFAOYSA-L 0.000 claims description 2
- 229910000366 copper(II) sulfate Inorganic materials 0.000 claims description 2
- 238000009826 distribution Methods 0.000 abstract description 13
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- GPNDARIEYHPYAY-UHFFFAOYSA-N palladium(II) nitrate Inorganic materials [Pd+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O GPNDARIEYHPYAY-UHFFFAOYSA-N 0.000 description 5
- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical compound [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 description 4
- 238000006731 degradation reaction Methods 0.000 description 4
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- 230000015556 catabolic process Effects 0.000 description 3
- 239000010949 copper Substances 0.000 description 3
- 239000008367 deionised water Substances 0.000 description 3
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- 238000007254 oxidation reaction Methods 0.000 description 3
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- VVJKKWFAADXIJK-UHFFFAOYSA-N Allylamine Chemical compound NCC=C VVJKKWFAADXIJK-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 230000032683 aging Effects 0.000 description 2
- 239000003054 catalyst Substances 0.000 description 2
- XTVVROIMIGLXTD-UHFFFAOYSA-N copper(II) nitrate Inorganic materials [Cu+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O XTVVROIMIGLXTD-UHFFFAOYSA-N 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 238000001027 hydrothermal synthesis Methods 0.000 description 2
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 2
- 238000005580 one pot reaction Methods 0.000 description 2
- IQUPABOKLQSFBK-UHFFFAOYSA-N 2-nitrophenol Chemical compound OC1=CC=CC=C1[N+]([O-])=O IQUPABOKLQSFBK-UHFFFAOYSA-N 0.000 description 1
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 1
- 101710134784 Agnoprotein Proteins 0.000 description 1
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 1
- PMMYEEVYMWASQN-DMTCNVIQSA-N Hydroxyproline Chemical compound O[C@H]1CN[C@H](C(O)=O)C1 PMMYEEVYMWASQN-DMTCNVIQSA-N 0.000 description 1
- 229910020427 K2PtCl4 Inorganic materials 0.000 description 1
- WHNWPMSKXPGLAX-UHFFFAOYSA-N N-Vinyl-2-pyrrolidone Chemical compound C=CN1CCCC1=O WHNWPMSKXPGLAX-UHFFFAOYSA-N 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 229910002837 PtCo Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 229910002091 carbon monoxide Inorganic materials 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
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- 235000019253 formic acid Nutrition 0.000 description 1
- 238000009775 high-speed stirring Methods 0.000 description 1
- 239000000017 hydrogel Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 239000002923 metal particle Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 150000002825 nitriles Chemical class 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 239000003381 stabilizer Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- FGMPLJWBKKVCDB-UHFFFAOYSA-N trans-L-hydroxy-proline Natural products ON1CCCC1C(O)=O FGMPLJWBKKVCDB-UHFFFAOYSA-N 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 238000002834 transmittance Methods 0.000 description 1
- 238000011144 upstream manufacturing Methods 0.000 description 1
- MWOOGOJBHIARFG-UHFFFAOYSA-N vanillin Chemical compound COC1=CC(C=O)=CC=C1O MWOOGOJBHIARFG-UHFFFAOYSA-N 0.000 description 1
- FGQOOHJZONJGDT-UHFFFAOYSA-N vanillin Natural products COC1=CC(O)=CC(C=O)=C1 FGQOOHJZONJGDT-UHFFFAOYSA-N 0.000 description 1
- 235000012141 vanillin Nutrition 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
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/48—Silver or gold
- B01J23/50—Silver
-
- 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
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
- B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
- B01J23/44—Palladium
-
- 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
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
- B01J23/8926—Copper and noble metals
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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
- B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C213/00—Preparation of compounds containing amino and hydroxy, amino and etherified hydroxy or amino and esterified hydroxy groups bound to the same carbon skeleton
- C07C213/02—Preparation of compounds containing amino and hydroxy, amino and etherified hydroxy or amino and esterified hydroxy groups bound to the same carbon skeleton by reactions involving the formation of amino groups from compounds containing hydroxy groups or etherified or esterified hydroxy groups
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Abstract
The invention provides a method for preparing a noble metal alloy/reduced graphene oxide composite material, which is to continuously prepare the noble metal alloy/reduced graphene oxide composite material by utilizing liquid-liquid two-phase flow in a microchannel reactor. The method specifically comprises the following steps: preparing a metal precursor 1, a metal precursor 2, polyvinylpyrrolidone and graphene oxide into an aqueous solution A, and preparing sodium borohydride and sodium hydroxide into an aqueous solution B and an aqueous solution C. And then simultaneously injecting the aqueous solution A, the aqueous solution B and n-octane into a micro mixer I, and flowing into a reaction tube I for reaction. And the reactant flows out of the reaction tube I and then enters the micro mixer II, and the aqueous solution C is mixed and then flows into the reaction tube II. And centrifuging and washing the suspension obtained at the outlet of the reaction tube II. The method has the advantages of continuous process, simple process, mild reaction conditions, wide applicability, short retention time, small average grain diameter of the alloy nano particles of the obtained composite material, narrow grain diameter distribution, good repeatability among batches and the like.
Description
Technical Field
The invention belongs to the field of material science and engineering, and relates to a method for preparing a precious metal alloy/reduced graphene oxide composite material by utilizing liquid-liquid two-phase flow in a microchannel reactor.
Background
In recent decades, bimetallic nanoparticles have gained much attention due to their unique surface binding sites and electronic properties resulting in more novel electronic properties and superior catalytic activity than their single-component metals. Since individual bimetallic nanoparticles tend to agglomerate to lower specific surface energies, resulting in reduced catalytic performance, researchers have deposited metallic nanoparticles on a support to prevent agglomeration of the bimetallic NPs to ensure good dispersion of the bimetallic nanoparticles. Graphene is a two-dimensional carbon material with one to several atomic layer thicknesses, and is one of the most promising carriers due to its ultra-high specific surface area, high light transmittance, excellent mechanical strength, excellent electrical conductivity, and good chemical inertness. Hitherto, bimetallic/graphene composite materials of various components (such as PtPd, PtCu, AgPd, PtCo, AuPd, AuAg) are widely applied to the fields of hydrogen production by formic acid, alcohol oxidation, carbon monoxide conversion and the like, and show huge application potential. Numerous studies have shown that the catalytic performance of noble metals is highly dependent on their size. The ultrafine noble metal nanoparticles, particularly noble metal particles smaller than 5nm, show super-excellent catalytic performance in methanol oxidation, oxygen reduction reaction, reduction on nitrophenol and other reactions. At present, the preparation of the bimetal/graphene composite material mostly adopts a co-reduction method, namely, the preparation method comprises the steps of mixing a metal precursor, graphene oxide and a stabilizer, adding a reducing agent to reduce metal and graphene together, and carrying out subsequent ageing, hydrothermal treatment and the like.
Study by Liu et al, "AgPd nanoparticles supported on reduced graphene oxide A high catalytic activity catalyst for the transformation of nitriles, Catalysis Communications,2018,108, 103-107" sacrificial by non-noble metalsThe AgPd/reduced graphene oxide composite material is prepared by the method. First, Co is mixed3(BO3)2、AgNO3、H2PdCl4Mixing with graphene oxide, and dropwise adding NaBH under high-speed stirring4Mixing Co3(BO3)2Co-depositing the solid and AgPd nano particles on the surface of the reduced graphene oxide, and centrifuging and washing the obtained solid; then, the solid is dispersed in H3PO4Removing Co from solution by acid etching3(BO3)2Removing, washing and centrifuging to obtain AgPd/reduced graphene oxide. The average particle size of AgPd NPs is 4.3 +/-0.9 nm. The method is intermittent operation, complex in process, long in time consumption and incapable of continuous production.
Study by Li et al "synthetic Ag-Pd nanoparticles-purified graphene oxide a facsimiling, three-dimensional, nano-crystalline as an electron crystallographic sensing platform for vanillin determination, electrochemical Acta,2015,176, 827-835" one-pot method for preparation of AgPd/reduced graphene oxide. Preparing AgNO3, PdCl2 and graphene oxide into an aqueous solution in a batch kettle, adding polyethylene glycol, stirring for reacting for 2 hours, standing and aging for 5 hours, and finally centrifuging and washing to obtain the product. The average grain diameter of AgPd NPs is 5-30 nm. The method is intermittent operation, long in time consumption, obvious in AgPdNPs agglomeration of the obtained product, large in average particle size and uneven in particle size distribution.
Gong et al, research "Platinum-copper alloys supported on reduced graphene oxides-One-pot synthesis and electrochemical applications, Carbon,2015,91, 338-" hydrothermal preparation of PtCu/reduced graphene oxide composites. Will K2PtCl4And CuCl2Mixing with allylamine hydrochloric acid, and adding HCHO; after hydrothermal treatment at 120 ℃ for 4 hours, the product was obtained by centrifugal washing. The average particle size of PtCu nanoparticles in the obtained PtCu/reduced graphene oxide is 6 nm. The method has the disadvantages of intermittent operation and long time consumption.
Shi et al studied "One-step hydrothermal synthesis of a three-dimensional reduced graphene oxide hydrogels andthe organic PtPd alloyedparations for ethylene glycol oxidation and hydrogen evolution reactions, Electrochimica Acta,2019,293,504-513. "preparation of PtPd/reduced graphene oxide composite material by hydrothermal method, mixing L-hydroxyproline and H-hydroxyproline2PtCl6、H2PdCl4And graphene oxide, and carrying out hydrothermal treatment at 180 ℃ for 12 hours. The average particle size of the PtPd nanoparticles in the obtained material is 5 nm. The method has the defects of intermittent operation, long production time and large high-temperature energy consumption.
In summary, the preparation process of the precious metal alloy/reduced graphene oxide composite material is mostly intermittent operation carried out in the traditional reactor at present, and has the defects of complicated process, long production time, discontinuous process, large particle size of loaded alloy particles, uneven particle size distribution, poor repeatability among batches and the like. Therefore, it is very urgent to develop a method which is simple, fast, and capable of continuous mass production, and the obtained nano material has small particle size, uniform particle size and good repeatability among batches. Compared with the traditional stirring type reactor, the micro-reactor has the advantages of good transfer performance, accurate and controllable reaction conditions, narrow residence time distribution, uniform micro-reaction environment, easy integration and the like, so the micro-reactor has incomparable advantages in the aspect of preparing micro/nano materials. In the microreactor, the nucleation and growth of crystals are carried out in a uniform microcosmic environment, so that a product with uniform particle size and good batch-to-batch repeatability is obtained. In addition, the preparation process of the nano material based on the micro chemical technology is in a continuous operation mode, and the large-scale production is easy. However, the problem of blockage caused by crystallization of particles on the wall surface is difficult to avoid in the preparation process of the micro-nano material due to homogeneous phase flow.
Disclosure of Invention
In order to solve the technical problems, the invention provides a method for preparing a noble metal alloy/reduced graphene oxide composite material by adopting liquid-liquid two-phase flow and gas-liquid three-phase flow in a microreactor, and as the microreactor can strengthen the mixing process, the prepared alloy nanoparticle/reduced graphene oxide composite material has narrow particle size distribution of nanoparticles, the average particle size can be controlled below 3nm, and the composite material can continuously run for a long time without blockage.
The technical scheme adopted by the invention is as follows: a method for preparing a noble metal alloy/reduced graphene oxide composite material is to continuously prepare the noble metal alloy/reduced graphene oxide composite material by utilizing liquid-liquid two-phase flow in a microchannel reactor, and comprises the following steps:
(1) introducing the aqueous solution A, the aqueous solution B and n-octane into a microchannel reactor for reaction;
the aqueous solution A is prepared from a metal precursor 1, a metal precursor 2, polyvinylpyrrolidone, graphene oxide and water. Wherein the total molar concentration of the metal ions is 0.25-1mmol/L, and the mass concentration of the polyvinylpyrrolidone is 0.8-3.2g/L, preferably 1.5-3.2 g/L; the mass concentration ratio of the total metal ions to the graphene oxide in the aqueous solution A is 0.66:1-0.06:1, preferably 0.08:1-0.54: 1;
the aqueous solution B is a mixed aqueous solution of sodium borohydride and sodium hydroxide; the molar concentration ratio of the sodium borohydride in the aqueous solution B to the total metal ions in the aqueous solution A is 1:1-5: 1; the molar concentration of NaOH in the aqueous solution B is 1.5-10mmol/L, preferably 1.5-8 mmol/L;
wherein the volume flow rates of the aqueous solution A and the aqueous solution B are equal, and the volume flow rate ranges from 0.05 mL/min to 1.5mL/min, preferably from 0.1 mL/min to 0.8 mL/min; the ratio of the volume flow rate of n-octane to the total volume flow rate of aqueous solution A and aqueous solution B is in the range of 0.16:1 to 6:1, preferably 0.25:1 to 4: 1;
(2) introducing the aqueous solution C into the microchannel reactor, and continuing the reaction;
the aqueous solution C is a mixed aqueous solution of sodium borohydride and sodium hydroxide; the aqueous solution B and the aqueous solution C are two mixed aqueous solutions of sodium borohydride and sodium hydroxide with different concentrations; wherein the molar concentration ratio of the sodium borohydride in the aqueous solution C to the total metal ions in the aqueous solution A is 5:1-20:1, preferably 10:1-20: 1; the molar concentration of NaOH in the aqueous solution C is 1.5-20mmol/L, preferably 10-20 mmol/L;
the volume flow rate of the aqueous solution C is equal to the volume flow rate of the aqueous solution a;
(3) centrifuging and washing the obtained product (suspension liquid) to obtain the noble metal alloy/reduced graphene oxide composite material;
the reaction temperature range of the microchannel reactor is 55-100 ℃, and preferably 60-90 ℃.
In the above technical solution, preferably, in the step (1), the aqueous solution a, the aqueous solution B, and n-octane are introduced into a micro mixer I; the aqueous solution A and the aqueous solution B are quickly mixed and are dispersed into independent aqueous phase liquid bullets (aqueous phase droplets) by the n-octane to form two-phase flow which takes the n-octane as a continuous phase and the aqueous solution as a dispersed phase and flows into the reaction tube I; in the step (2), the reaction materials flow into a micro mixer II through a reaction tube I, meanwhile, the aqueous solution C is also injected into the micro mixer II, and aqueous phase liquid bullets (aqueous phase liquid drops) are rapidly mixed with the aqueous solution C and enter the reaction tube II to continue to react;
the micro mixer I, the reaction tube I, the micro mixer II and the reaction tube II are all placed in a constant-temperature water bath/oil bath to control the reaction temperature, the reaction temperature range is 55-100 ℃, and 60-90 ℃ is preferred.
In the above technical scheme, preferably, the total residence time of the reactants is 0.8-4.8 min.
In the above-described embodiment, the ratio of the amounts of the metal precursor 1 and the metal precursor 2 is preferably 1:9 to 9:1, and more preferably 1:4 to 4: 1.
In the above technical solution, preferably, when preparing the AgPd/reduced graphene oxide composite material, the metal precursor 1 is AgNO3The metal precursor 2 is Pd (NO)3)2、H2PdCl4、PdCl2、Na2PdCl4、K2PdCl4One of (1); when preparing the PtCu/reduced graphene oxide composite material, the metal precursor 1 is H2PtCl6The metal precursor 2 is Cu (NO)3)2、CuCl2、CuSO4One of (1); when preparing the PtPd/reduced graphene oxide composite material, the metal precursor 1 is H2PtCl6The metal precursor 2 is Pd (NO)3)2、H2PdCl4、PdCl2、Na2PdCl4、K2PdCl4One kind of (1).
In the above technical scheme, preferably, for the preparation of the AgPd/reduced graphene oxide composite material, the concentration range of NaOH in the aqueous solution B is 1.5-6 mmol/L; for the preparation of the PtCu/reduced graphene oxide composite material, the concentration range of NaOH in the aqueous solution B is 2.6-8 mmol/L; for the preparation of the PtPd/reduced graphene oxide composite material, the concentration range of NaOH in the aqueous solution B is 3.1-6 mmol/L.
In the above technical solution, preferably, the micro mixer I has three inlet channels and one outlet channel, which are respectively marked as channel a, channel B, channel C and channel D, the cross sections of the four channels are all circular, and the central axes are on the same plane; the channel A and the channel B are symmetrically distributed on two sides of the channel C, and the included angle between the channel A and the channel B and the channel D is 30-90 degrees; the central axes of the channel D and the channel C are on the same straight line; the diameters and the lengths of the four channels are equal, the diameters are 0.5-1.0mm, and the lengths are 6-24 mm; the aqueous solution A, the aqueous solution B and the n-octane respectively enter a micro mixer I through a channel A, a channel B and a channel C; the micro mixer I is connected with a reaction tube I through a channel D, the diameter of the reaction tube I is 0.5-1.0mm, and the length of the reaction tube I is 1-4 m.
In the above technical solution, preferably, the micro mixer II has two inlet channels and one outlet channel, which are respectively marked as channel E, channel F and channel G, the cross-sectional areas of the three channels are all circular, and the central axes are on the same plane; the channels E and F are symmetrically distributed on two sides of the channel G, and the included angle between the channels E and F and the channel G is 90-150 degrees; the diameters and the lengths of the three channels are equal, the diameter is 0.5-1.0mm, and the length is 6-24 mm; and the water solution C and the reaction liquid from the reaction tube I respectively enter a micro mixer II through a channel E and a channel F, the micro mixer II is connected with the reaction tube II through a channel G, the diameter of the reaction tube II is 0.6-1.0mm, and the length of the reaction tube II is 1-4 m.
The invention also relates to a method for protecting the precious metal alloy/reduced graphene oxide composite material prepared by the method. Alloy nano particles in the noble metal alloy/reduced graphene oxide composite material are uniformly dispersed on the surface of a graphene sheet layer, the particle size range of the alloy nano particles is 1-5nm, and the average particle size is less than 3 nm.
The invention also relates to application of the prepared precious metal alloy/reduced graphene oxide composite material in catalyzing p-nitrophenol reduction, and the precious metal alloy/reduced graphene oxide composite material has more excellent catalytic performance than a single metal/reduced graphene oxide composite material.
Compared with the prior art, the invention has the prominent substantive characteristics and remarkable progress that:
1. the method for synthesizing the noble metal alloy/reduced graphene oxide composite material by using the liquid-liquid two-phase flow based on the microreactor has the advantages of simple process, wide application range, short time consumption (short retention time), mild reaction conditions, continuous process and good repeatability among batches;
2. the noble metal alloy nanoparticles in the obtained composite material are uniformly loaded on the surface of the graphene oxide, the morphology and the particle size of the noble metal alloy nanoparticles are uniform, the average particle size is small and is less than 3nm, and the particle size distribution is narrow;
3. the obtained noble metal alloy/reduced graphene oxide composite material has better catalytic performance than single metal/reduced graphene oxide.
Drawings
FIG. 1 is a process flow diagram of the present invention, wherein 1, 2, 3, 4 are the first, second, third, and fourth injection pumps.
Fig. 2 is an XRD spectrum of the AgPd/reduced graphene oxide composite material prepared in example 1.
Fig. 3 is a TEM photograph of the AgPd/reduced graphene oxide composite prepared in example 1.
Fig. 4 is an XRD spectrum of the PtCu/reduced graphene oxide composite material prepared in example 2.
Fig. 5 is a TEM photograph of the PtCu/reduced graphene oxide composite material prepared in example 2.
Fig. 6 is an XRD spectrum of the PtPd/reduced graphene oxide composite material prepared in example 3.
Fig. 7 is a TEM photograph of the PtPd/reduced graphene oxide composite material prepared in example 3.
Fig. 8 is a TEM photograph of the AgPd/reduced graphene oxide composite prepared in example 4.
Fig. 9 is a TEM photograph of the AgPd/reduced graphene oxide composite prepared in example 5.
Fig. 10 is a TEM photograph of the AgPd/reduced graphene oxide composite prepared in comparative example 1.
Fig. 11 is a TEM photograph of the PtPd/reduced graphene oxide composite material prepared in comparative example 2.
Fig. 12 is a TEM photograph of the AgPd/reduced graphene oxide composite prepared in comparative example 3.
FIG. 13 is a degradation curve of p-nitrophenol.
Detailed Description
In the following embodiments, the microreactors used are composed of a micromixer I, a reaction tube I, a micromixer II and a reaction tube II: the micro mixer I is provided with three inlet channels and one outlet channel which are respectively marked as a channel A, a channel B, a channel C and a channel D, the cross sections of the four channels are all circular, and the central axes are on the same plane. The channel A and the channel B are symmetrically distributed on two sides of the channel C, and the included angle between the channel A and the channel B and the channel D is 90 degrees; the central axes of the channel D and the channel C are on the same straight line. The four channels are equal in diameter and length, 0.5mm in diameter and 10mm in length. And the aqueous solution A, the aqueous solution B and the n-octane respectively enter a micro mixer I through a channel A, a channel B and a channel C. The reaction tube I is connected with the channel D, the diameter of the reaction tube I is 0.8mm, and the length of the reaction tube I is 4 m; the micro mixer II is provided with two inlet channels and one outlet channel which are respectively marked as a channel E, a channel F and a channel G, the cross-sectional areas of the three channels are all circular, and the central axes are on the same plane. The channels E and F are symmetrically distributed on two sides of the channel G, and the included angle between the channels E and F and the channel G is 90 degrees. The diameters and the lengths of the three channels are equal, the diameter is 0.5mm, and the length is 10 mm. The aqueous solution C and the reaction solution from the upstream enter the micromixer II through a channel E and a channel F respectively. The reaction tube II was connected to the channel G and had a diameter of 0.8mm and a length of 1 m.
The invention is further illustrated by the following examples.
Example 1
In this example, the micro mixer I, the reaction tube I, the micro mixer II, and the reaction tube II were placed in a constant temperature water bath/oil bath to control the reaction temperature, which was 60 ℃.
(1) Mixing AgNO3、Pd(NO3)2The polyvinylpyrrolidone, the graphene oxide and the water are prepared into an aqueous solution A. Wherein, AgNO3And Pd (NO)3)2The molar concentrations of the metal ions are 0.25mmol/L and 0.25mmol/L respectively, the mass concentration of the polyvinylpyrrolidone is 2.0g/L, and the mass concentration ratio of the total metal ions to the graphene oxide is 0.19: 1;
(2) preparing two mixed aqueous solutions of sodium borohydride and sodium hydroxide with different concentrations, and marking as an aqueous solution B and an aqueous solution C. Wherein the molar concentration ratio of the sodium borohydride in the aqueous solution B to the total metal ions in the aqueous solution A is 3: 1; the molar concentration ratio of sodium borohydride in the aqueous solution C to total metal ions in the aqueous solution A is 20: 1; the molar concentration of NaOH in the aqueous solution B is 3 mmol/L; the molar concentration of NaOH in the aqueous solution C is 20 mmol/L;
(3) introducing the aqueous solution A, the aqueous solution B and n-octane into a micro mixer I; wherein the volume flow rates of the aqueous solution A and the aqueous solution B are both 0.2mL/min, and the ratio of the volume flow rate of the n-octane to the total volume flow rate of the aqueous solution A and the aqueous solution B is 2: 3;
(4) injecting the aqueous solution C into the micro mixer II, wherein the volume flow rate of the aqueous solution C is equal to that of the aqueous solution A;
(5) and centrifuging and washing the sample obtained from the outlet of the reaction tube II for several times to finally prepare the AgPd/reduced graphene oxide sample. The loading of the metal of the resulting AgPd/reduced graphene oxide sample was 16 wt.%. The XRD spectrum and TEM photograph of the obtained sample are shown in fig. 2 and 3, respectively. As can be seen from the figure: in the AgPd/reduced graphene oxide composite material, all graphene oxide is reduced into reduced graphene oxide, and metal exists in the form of AgPd alloy; AgPd alloy nano particles are uniformly dispersed on the surface of the reduced graphene oxide, the average particle size is 2.7nm, and the particle size distribution is narrow.
Example 2
In this example, the micro mixer I, the reaction tube I, the micro mixer II, and the reaction tube II were placed in a constant temperature water bath/oil bath to control the reaction temperature, which was 60 ℃.
(1) H is to be2PtCl6、Cu(NO3)2The polyvinylpyrrolidone, the graphene oxide and the water are prepared into an aqueous solution A. Wherein H2PtCl6And Cu (NO)3)2The molar concentrations of the metal ions are 0.25mmol/L and 0.25mmol/L respectively, the mass concentration of the polyvinylpyrrolidone is 2.0g/L, and the mass concentration ratio of the total metal ions to the graphene oxide is 0.23: 1;
(2) preparing two mixed aqueous solutions of sodium borohydride and sodium hydroxide with different concentrations, and marking as an aqueous solution B and an aqueous solution C. Wherein the molar concentration ratio of the sodium borohydride in the aqueous solution B to the total metal ions in the aqueous solution A is 3: 1; the molar concentration ratio of sodium borohydride in the aqueous solution C to total metal ions in the aqueous solution A is 20: 1; the molar concentration of NaOH in the aqueous solution B is 4.1 mmol/L; the molar concentration of NaOH in the aqueous solution C is 20 mmol/L;
(3) introducing the aqueous solution A, the aqueous solution B and n-octane into a micro mixer I; wherein the volume flow rates of the aqueous solution A and the aqueous solution B are both 0.2 mL/min; the ratio of the volume flow rate of n-octane to the total volume flow rate of the aqueous solution A and the aqueous solution B is 2: 3;
(4) injecting the aqueous solution C into the micro mixer II, wherein the volume flow rate of the aqueous solution C is equal to that of the aqueous solution A;
(5) and centrifuging and washing the sample obtained from the outlet of the reaction tube II for several times to finally prepare the PtCu/reduced graphene oxide sample. The metal loading of the resulting PtCu/reduced graphene oxide sample was 19 wt.%. The XRD spectrum and TEM photograph of the obtained sample are shown in fig. 4 and 5, respectively. As can be seen from the figure: in the PtCu/reduced graphene oxide composite material, all graphene oxide is reduced into reduced graphene oxide, and metal exists in the form of PtCu alloy; the PtCu alloy nano particles are uniformly dispersed on the surface of the reduced graphene oxide, the average particle size is 2.5nm, and the particle size distribution is narrow.
Example 3
In this example, the micro mixer I, the reaction tube I, the micro mixer II, and the reaction tube II were placed in a constant temperature water bath/oil bath to control the reaction temperature, which was 60 ℃.
(1) H is to be2PtCl6、H2PdCl4Poly (A), poly (B)The vinyl pyrrolidone, the graphene oxide and the water are prepared into an aqueous solution A. Wherein H2PtCl6And H2PdCl4The molar concentrations of the metal ions are 0.25mmol/L and 0.25mmol/L respectively, the mass concentration of the polyvinylpyrrolidone is 2.0g/L, and the mass concentration ratio of the total metal ions to the graphene oxide is 0.27: 1;
(2) preparing two mixed aqueous solutions of sodium borohydride and sodium hydroxide with different concentrations, and marking as an aqueous solution B and an aqueous solution C. Wherein the molar concentration ratio of the sodium borohydride in the aqueous solution B to the total metal ions in the aqueous solution A is 3: 1; the molar concentration ratio of sodium borohydride in the aqueous solution C to total metal ions in the aqueous solution A is 20: 1; the molar concentration of NaOH in the aqueous solution B is 4.6 mmol/L; the molar concentration of NaOH in the aqueous solution C is 20 mmol/L;
(3) introducing the aqueous solution A, the aqueous solution B and n-octane into a micro mixer I; wherein the volume flow rates of the aqueous solution A and the aqueous solution B are both 0.2 mL/min; the ratio of the volume flow rate of n-octane to the total volume flow rate of the aqueous solution A and the aqueous solution B is 2: 3;
(4) injecting the aqueous solution C into the micro mixer II, wherein the volume flow rate of the aqueous solution C is equal to that of the aqueous solution A;
(5) and centrifuging and washing the sample obtained from the outlet of the reaction tube II for several times to finally prepare the PtPd/reduced graphene oxide sample. The metal loading of the resulting PtPd/reduced graphene oxide sample was 21 wt.%. The XRD spectrum and TEM photograph of the obtained sample are shown in fig. 6 and 7, respectively. As can be seen from the figure: in the PtPd/reduced graphene oxide composite material, all graphene oxide is reduced into reduced graphene oxide, and metal exists in the form of PtPd alloy; the PtPd alloy nano particles are uniformly dispersed on the surface of the reduced graphene oxide, the average particle size is 2.2nm, and the particle size distribution is narrow.
Example 4
In this example, the micro mixer I, the reaction tube I, the micro mixer II, and the reaction tube II were placed in a constant temperature water bath/oil bath to control the reaction temperature, which was 60 ℃.
(1) Mixing AgNO3、Pd(NO3)2The polyvinylpyrrolidone, the graphene oxide and the water are prepared into waterSolution A. Wherein, AgNO3And Pd (NO)3)2The molar concentrations of the metal ions are 0.25mmol/L and 0.25mmol/L respectively, the mass concentration of the polyvinylpyrrolidone is 2.0g/L, and the mass concentration ratio of the total metal ions to the graphene oxide is 0.19: 1;
(2) preparing two mixed aqueous solutions of sodium borohydride and sodium hydroxide with different concentrations, and marking as an aqueous solution B and an aqueous solution C. Wherein the molar concentration ratio of the sodium borohydride in the aqueous solution B to the total metal ions in the aqueous solution A is 3: 1; the molar concentration ratio of sodium borohydride in the aqueous solution C to total metal ions in the aqueous solution A is 20: 1; the molar concentration of NaOH in the aqueous solution B is 3.0 mmol/L; the molar concentration of NaOH in the aqueous solution C is 20 mmol/L;
(3) introducing the aqueous solution A, the aqueous solution B and n-octane into a micro mixer I; wherein the volume flow rates of the aqueous solution A and the aqueous solution B are both 0.2 mL/min; the ratio of the volume flow rate of n-octane to the total volume flow rate of the aqueous solution A and the aqueous solution B is 2: 3;
(4) injecting the aqueous solution C into the micro mixer II, wherein the volume flow rate of the aqueous solution C is equal to that of the aqueous solution A;
(5) and centrifuging and washing the sample obtained from the outlet of the reaction tube II for several times to finally prepare the AgPd/reduced graphene oxide sample. The loading of metal for the resulting AgPd/reduced graphene oxide sample was 16 wt.%. The TEM photographs of the obtained samples are shown in fig. 8, respectively. As can be seen from the figure: AgPd alloy nano particles are uniformly dispersed on the surface of the reduced graphene oxide, the average particle size is 2.6nm, and the particle size distribution is narrow.
Example 5
In this example, the micro mixer I, the reaction tube I, the micro mixer II, and the reaction tube II were placed in a constant temperature water bath/oil bath to control the reaction temperature, which was 60 ℃.
(1) Mixing AgNO3、Pd(NO3)2The polyvinylpyrrolidone, the graphene oxide and the water are prepared into an aqueous solution A. Wherein, AgNO3And Pd (NO)3)2The molar concentrations of the compounds are 0.6mmol/L and 0.4mmol/L respectively, the mass concentration of the polyvinylpyrrolidone is 3.2g/L, and the mass concentration ratio of the total metal ions to the graphene oxide is 0.38:1；
(2) Preparing two mixed aqueous solutions of sodium borohydride and sodium hydroxide with different concentrations, and marking as an aqueous solution B and an aqueous solution C. Wherein the molar concentration ratio of the sodium borohydride in the aqueous solution B to the total metal ions in the aqueous solution A is 3: 1; the molar concentration ratio of sodium borohydride in the aqueous solution C to total metal ions in the aqueous solution A is 20: 1; the molar concentration of NaOH in the aqueous solution B is 3 mmol/L; the molar concentration of NaOH in the aqueous solution C is 20 mmol/L;
(3) introducing the aqueous solution A, the aqueous solution B and n-octane into a micro mixer I; wherein the volume flow rates of the aqueous solution A and the aqueous solution B are both 0.2mL/min, and the ratio of the volume flow rate of the n-octane to the total volume flow rate of the aqueous solution A and the aqueous solution B is 2: 3;
(4) injecting the aqueous solution C into the micro mixer II, wherein the volume flow rate of the aqueous solution C is equal to that of the aqueous solution A;
(5) and centrifuging and washing the sample obtained from the outlet of the reaction tube II for several times to finally prepare the AgPd/reduced graphene oxide sample. The metal loading of the resulting AgPd/reduced graphene oxide sample was 28 wt.%. The TEM photograph of the obtained sample is shown in FIG. 9. As can be seen from the figure: AgPd alloy nano particles are uniformly dispersed on the surface of the reduced graphene oxide, the average particle size is 2.8nm, and the particle size distribution is narrow.
Comparative example 1
In this comparative example, the micromixer I, the reaction tube I, the micromixer II, and the reaction tube II were placed in a constant temperature water bath/oil bath to control the reaction temperature, which was 60 ℃.
(1) Mixing AgNO3、Pd(NO3)2The sodium dodecyl sulfate, the graphene oxide and the water are prepared into an aqueous solution A. Wherein, AgNO3And Pd (NO)3)2The molar concentrations of the metal ions are 0.25mmol/L and 0.25mmol/L respectively, the mass concentration of the sodium dodecyl sulfate is 2.9g/L, and the mass concentration ratio of the total metal ions to the graphene oxide is 0.19: 1;
(2) preparing two mixed aqueous solutions of sodium borohydride and sodium hydroxide with different concentrations, and marking as an aqueous solution B and an aqueous solution C. Wherein the molar concentration ratio of the sodium borohydride in the aqueous solution B to the total metal ions in the aqueous solution A is 3: 1; the molar concentration ratio of sodium borohydride in the aqueous solution C to total metal ions in the aqueous solution A is 20: 1; the molar concentration of NaOH in the aqueous solution B is 3.0 mmol/L; the molar concentration of NaOH in the aqueous solution C is 20 mmol/L;
(3) introducing the aqueous solution A, the aqueous solution B and n-octane into a micro mixer I; wherein the volume flow rates of the aqueous solution A and the aqueous solution B are both 0.2 mL/min; the ratio of the volume flow rate of n-octane to the total volume flow rate of the aqueous solution A and the aqueous solution B is 2: 3;
(4) injecting the aqueous solution C into the micro mixer II, wherein the volume flow rate of the aqueous solution C is equal to that of the aqueous solution A;
(5) and centrifuging and washing the sample obtained from the outlet of the reaction tube II for several times. The TEM photograph of the obtained sample is shown in FIG. 10. As can be seen from the figure: the metal nanoparticles are in a free state, i.e., the metal nanoparticles are not successfully loaded on the surface of the reduced graphene oxide.
Comparative example 2
In this comparative example, the micromixer I, the reaction tube I, the micromixer II, and the reaction tube II were placed in a constant temperature water bath/oil bath to control the reaction temperature, which was 60 ℃.
(1) H is to be2PtCl6、Cu(NO3)2The sodium dodecyl sulfate, the graphene oxide and the water are prepared into an aqueous solution A. Wherein H2PtCl6And Cu (NO)3)2The molar concentrations of the metal ions are 0.25mmol/L and 0.25mmol/L respectively, the mass concentration of the sodium dodecyl sulfate is 2.9g/L, and the mass concentration ratio of the total metal ions to the graphene oxide is 0.23: 1;
(2) preparing two mixed aqueous solutions of sodium borohydride and sodium hydroxide with different concentrations, and marking as an aqueous solution B and an aqueous solution C. Wherein the molar concentration ratio of the sodium borohydride in the aqueous solution B to the total metal ions in the aqueous solution A is 3: 1; the molar concentration ratio of sodium borohydride in the aqueous solution C to total metal ions in the aqueous solution A is 20: 1; the molar concentration of NaOH in the aqueous solution B is 4.1 mmol/L; the molar concentration of NaOH in the aqueous solution C is 20 mmol/L;
(3) introducing the aqueous solution A, the aqueous solution B and n-octane into a micro mixer I; wherein the volume flow rates of the aqueous solution A and the aqueous solution B are both 0.2 mL/min; the ratio of the volume flow rate of n-octane to the total volume flow rate of the aqueous solution A and the aqueous solution B is 2: 3;
(4) injecting the aqueous solution C into the micro mixer II, wherein the volume flow rate of the aqueous solution C is equal to that of the aqueous solution A;
(5) and centrifuging and washing the sample obtained from the outlet of the reaction tube II for several times. The TEM photograph of the obtained sample is shown in FIG. 11. It can be seen from the figure that only a few PtCu nanoparticles are loaded on the surface of the reduced graphene oxide, and the distribution is not uniform.
Comparative example 3
(1) Mixing AgNO3、Pd(NO3)2The polyvinylpyrrolidone, the graphene oxide and the water are prepared into an aqueous solution A. Wherein, AgNO3And Pd (NO)3)2The molar concentrations of the metal ions are 0.25mmol/L and 0.25mmol/L respectively, the mass concentration of the polyvinylpyrrolidone is 2.0g/L, and the mass concentration ratio of the total metal ions to the graphene oxide is 0.19: 1;
(2) preparing two mixed aqueous solutions B of sodium borohydride and sodium hydroxide. Wherein the molar concentration ratio of sodium borohydride to total metal ions in the aqueous solution A is 23: 1; the molar concentration of NaOH in the aqueous solution B is 20 mmol/L;
(3) while stirring vigorously, aqueous solution A and aqueous solution B were dropped simultaneously at a rate of 3.0mL/min into a 250mL three-necked flask to which 10mL of deionized water had been previously added, and the flask was placed in a thermostatic water bath at 60 ℃. After the aqueous solution is added, stirring is continued for 10 minutes. And centrifuging and washing the obtained sample to obtain the AgPd/reduced graphene oxide sample. The TEM photograph of the obtained sample is shown in FIG. 12. It can be seen that the AgPd nanoparticles have a broad particle size distribution and a large average particle size.
Application example
The AgPd/reduced graphene oxide composite material prepared in the embodiment 1 catalyzes and degrades p-nitrophenol:
(1) dissolving 0.0483g of p-nitrophenol in 100mL of deionized water, taking 5mL of the solution, diluting to 100mL, and taking 2mL of the solution as degradation reaction;
(2) dissolving 0.095g of sodium borohydride in 50mL of deionized water to obtain 50mmol/L sodium borohydride aqueous solution, and adding 0.7mL of sodium borohydride aqueous solution into 2mL of p-nitrophenol obtained in the step (1);
(3) adding 4X 10 of the mixed solution obtained in the step (2)-3mg of the AgPd/reduced graphene oxide composite material prepared in the embodiment 1 is used as a catalyst, and the AgPd/reduced graphene oxide composite material is uniformly mixed to achieve adsorption balance;
(4) performing UV-vis detection every 30 s;
(5) the detection results were processed and plotted for p-nitrophenol degradation as shown in FIG. 12.
By AgNO3Instead of Pd (NO) in example 13)2As a metal precursor, Ag/reduced graphene oxide was prepared by the method of steps (1) to (5) described in example 1; with Pd (NO)3)2Instead of AgNO in example 13As the metal precursor, Pd/reduced graphene oxide was prepared by the method of steps (1) to (5) described in example 1.
The catalytic performance of the Ag/reduced graphene oxide composite material and the Pd/reduced graphene oxide composite material prepared by the method described in example 1 were tested by the methods of the above steps (1) to (5), and a p-nitrophenol degradation curve was obtained and compared with the catalytic performance of the AgPd/reduced graphene oxide composite material prepared in example 1. It can be seen that the catalytic performance of AgPd/reduced graphene oxide is several times higher than the catalytic activity of Ag/reduced graphene oxide and Pd/reduced graphene oxide.
Claims (10)
1. A method for preparing a precious metal alloy/reduced graphene oxide composite material is characterized by comprising the following steps:
(1) introducing the aqueous solution A, the aqueous solution B and n-octane into a microchannel reactor for reaction;
the aqueous solution A is prepared from a metal precursor 1, a metal precursor 2, polyvinylpyrrolidone, graphene oxide and water; the total molar concentration of the metal ions is 0.25-1mmol/L, the mass concentration of the polyvinylpyrrolidone is 0.8-3.2g/L, and the mass ratio of the total mass of the metal ions in the aqueous solution A to the mass of the graphene oxide is 0.66:1-0.06: 1;
the aqueous solution B is a mixed aqueous solution of sodium borohydride and sodium hydroxide; the ratio of the molar concentration of sodium borohydride in the aqueous solution B to the total molar concentration of metal ions in the aqueous solution A is 1:1-5: 1; the molar concentration of NaOH in the aqueous solution B is 1.5-10 mmol/L;
the volume flow rates of the aqueous solution A and the aqueous solution B are equal and are 0.05-1.5 mL/min; the ratio of the volume flow rate of the n-octane to the total volume flow rate of the aqueous solution A and the aqueous solution B is 0.16:1-6: 1;
(2) introducing the aqueous solution C into the microchannel reactor, and continuing the reaction;
wherein the aqueous solution C is a mixed aqueous solution of sodium borohydride and sodium hydroxide; the ratio of the molar concentration of sodium borohydride in the aqueous solution C to the total molar concentration of metal ions in the aqueous solution A is 5:1-20: 1; the molar concentration of NaOH in the aqueous solution C is 1.5-20 mmol/L;
the volume flow rate of the aqueous solution C is equal to the volume flow rate of the aqueous solution A;
(3) centrifuging and washing the obtained product to obtain a noble metal alloy/reduced graphene oxide composite material;
the reaction temperature of the microchannel reactor is 55-100 ℃.
2. The method of claim 1, wherein: in the step (1), introducing the aqueous solution A, the aqueous solution B and n-octane into a micro mixer I, mixing the aqueous solution A and the aqueous solution B, dispersing the aqueous solution A and the aqueous solution B into independent aqueous phase droplets by the n-octane to form two-phase flow taking the n-octane as a continuous phase and the aqueous solution as a dispersed phase, and flowing into a reaction tube I;
in the step (2), the reaction materials flow into a micro mixer II through a reaction tube I, meanwhile, the aqueous solution C is also injected into the micro mixer II, and aqueous phase droplets are mixed with the aqueous solution C and enter the reaction tube II for continuous reaction;
the reaction temperature of the micro mixer I, the reaction tube I, the micro mixer II and the reaction tube II is 55-100 ℃.
3. The method according to claim 1 or 2, characterized in that: the ratio of the amounts of the substances of the metal precursor 1 and the metal precursor 2 is 1:9 to 9: 1.
4. The method according to claim 1 or 2, characterized in that: when preparing the AgPd/reduced graphene oxide composite material, the metal precursor 1 is AgNO3The metal precursor 2 is Pd (NO)3)2、H2PdCl4、PdCl2、Na2PdCl4、K2PdCl4One of (1); when preparing the PtCu/reduced graphene oxide composite material, the metal precursor 1 is H2PtCl6The metal precursor 2 is Cu (NO)3)2、CuCl2、CuSO4One of (1); when preparing the PtPd/reduced graphene oxide composite material, the metal precursor 1 is H2PtCl6The metal precursor 2 is Pd (NO)3)2、H2PdCl4、PdCl2、Na2PdCl4、K2PdCl4One kind of (1).
5. The method of claim 1, wherein: for the preparation of the AgPd/reduced graphene oxide composite material, the concentration of NaOH in the aqueous solution B is 1.5-6 mmol/L; for the preparation of the PtCu/reduced graphene oxide composite material, the concentration of NaOH in the aqueous solution B is 2.6-8 mmol/L; for the preparation of the PtPd/reduced graphene oxide composite material, the concentration of NaOH in the aqueous solution B is 3.1-6 mmol/L.
6. The method of claim 2, further comprising: the micro mixer I is provided with three inlet channels and one outlet channel which are respectively marked as a channel A, a channel B, a channel C and a channel D, the cross sections of the four channels are circular, and the central axes are on the same plane; the channel A and the channel B are symmetrically distributed on two sides of the channel C, and the included angle between the channel A and the channel B and the channel D is 30-90 degrees; the central axes of the channel D and the channel C are on the same straight line; the diameters and the lengths of the four channels are equal, the diameters are 0.5-1.0mm, and the lengths are 6-24 mm; the aqueous solution A, the aqueous solution B and the n-octane respectively enter a micro mixer I through a channel A, a channel B and a channel C; the micro mixer I is connected with a reaction tube I through a channel D, the diameter of the reaction tube I is 0.5-1.0mm, and the length of the reaction tube I is 1-4 m.
7. The method of claim 2, wherein: the micro mixer II is provided with two inlet channels and one outlet channel which are respectively marked as a channel E, a channel F and a channel G, the cross sectional areas of the three channels are circular, and the central axes are on the same plane; the channels E and F are symmetrically distributed on two sides of the channel G, and the included angle between the channels E and F and the channel G is 90-150 degrees; the diameters and the lengths of the three channels are equal, the diameter is 0.5-1.0mm, and the length is 6-24 mm; and the water solution C and the reaction liquid from the reaction tube I respectively enter a micro mixer II through a channel E and a channel F, the micro mixer II is connected with the reaction tube II through a channel G, the diameter of the reaction tube II is 0.6-1.0mm, and the length of the reaction tube II is 1-4 m.
8. The method of claim 1, wherein the alloy nanoparticles in the noble metal alloy/reduced graphene oxide composite have a particle size of 1-5 nm.
9. A precious metal alloy/reduced graphene oxide composite material prepared by the method of any one of claims 1 to 8.
10. The use of the precious metal alloy/reduced graphene oxide composite material prepared according to claim 9 in catalyzing the reduction of p-nitrophenol.
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