CN108837827B - Double-layer core-shell structure platinum catalyst and preparation method and application thereof - Google Patents

Double-layer core-shell structure platinum catalyst and preparation method and application thereof Download PDF

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CN108837827B
CN108837827B CN201810778894.5A CN201810778894A CN108837827B CN 108837827 B CN108837827 B CN 108837827B CN 201810778894 A CN201810778894 A CN 201810778894A CN 108837827 B CN108837827 B CN 108837827B
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layer core
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CN108837827A (en
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张雁冰
刘宝仓
李常艳
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Inner Mongolia University
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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
    • 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
    • B01J23/42—Platinum
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    • B01J35/397—
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
    • C01B3/02—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen
    • C01B3/04—Production of hydrogen or of gaseous mixtures containing a substantial proportion of hydrogen by decomposition of inorganic compounds, e.g. ammonia
    • C01B3/042—Decomposition of water
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/36—Hydrogen production from non-carbon containing sources, e.g. by water electrolysis

Abstract

The invention belongs to the technical field of photocatalysis, and particularly relates to a platinum catalyst with a double-layer core-shell structure, and a preparation method and application thereof. The double-layer core-shell structure platinum catalyst provided by the invention comprises a core body and a shell layer, wherein the core body is a silicon dioxide microsphere; the shell layer sequentially comprises a titanium dioxide layer and a graphene oxide layer from inside to outside, and the titanium dioxide layer comprises anatase titanium dioxide; the graphene oxide layer is loaded with Pt. When the double-layer core-shell structure platinum catalyst provided by the invention is used for water catalytic decomposition, the hydrogen yield reaches 39.26mmol/g after 6h of reaction.

Description

Double-layer core-shell structure platinum catalyst and preparation method and application thereof
Technical Field
The invention belongs to the technical field of photocatalysis, and particularly relates to a platinum catalyst with a double-layer core-shell structure, and a preparation method and application thereof.
Background
TiO2Has the advantages of strong photocatalytic performance, large specific surface area, long-term stability and the like, and is always paid attention by researchers, but TiO2The forbidden band width of the reaction kettle is only 3.2 electron volts, and only ultraviolet light which is 3-5% of sunlight can be absorbed to participate in the reaction, so that TiO is influenced2The photocatalytic performance of (a). For increasing TiO content2The researchers made TiO into the catalyst2By complexing with noble metals, e.g. Au, Ag and Pt, using noble metals in combination with TiO2The difference of Fermi energy levels promotes the transfer of current carriers in the composite material, improves the rate of oxidation-reduction reaction, and further achieves the purpose of improving TiO2The photocatalytic activity of the compound.
The above-mentioned composite material is comparable to pure TiO2In other words, the photocatalytic performance is improved, but if the photocatalyst is used for water catalytic decomposition reaction, the rate of hydrogen generation through water catalytic decomposition is still not ideal.
Disclosure of Invention
The invention aims to provide a double-layer core-shell structure platinum catalyst, and a preparation method and application thereof.
In order to achieve the above purpose, the invention provides the following technical scheme:
a double-layer core-shell structure platinum catalyst comprises a core body and a shell layer, wherein the core body is a silicon dioxide microsphere; the shell layer sequentially comprises a titanium dioxide layer and a graphene oxide layer from inside to outside, and the titanium dioxide layer comprises anatase titanium dioxide; the graphene oxide layer is loaded with Pt.
Preferably, the diameter of the silicon dioxide microspheres is 100-150 nm, the thickness of the titanium dioxide layer is 45-50 nm, and the thickness of the graphene oxide layer is 3-5 nm.
Preferably, the loading amount of the Pt in the graphene oxide is 0.01-0.1 wt.%; the particle size of the Pt is 5-7 nm.
The invention provides a preparation method of a double-layer core-shell structure platinum catalyst, which comprises the following steps:
(1) providing an alkaline silica microsphere dispersion as an alkaline core dispersion;
(2) dropwise adding an organic titanium source solution into the alkaline core dispersion liquid, and performing hydrolysis reaction to obtain a single-layer core-shell structure carrier;
(3) sequentially grinding and roasting the single-layer core-shell structure carrier to obtain a crystalline single-layer core-shell structure carrier;
(4) carrying out amino modification on the crystalline single-layer core-shell structure carrier to obtain a modified single-layer core-shell structure carrier;
(5) dropwise adding the graphene oxide aqueous dispersion into the aqueous dispersion of the modified single-layer core-shell structure carrier for coating reaction, and then washing a solid material in a reaction liquid to obtain a double-layer core-shell structure carrier;
(6) dipping the double-layer core-shell structure carrier into a platinic acid aqueous solution, and carrying out Pt loading to obtain a double-layer core-shell structure platinum catalyst; the platinic acid aqueous solution comprises platinic acid, a reducing agent and polyvinyl alcohol.
Preferably, the concentration of the silica microspheres in the silica microsphere dispersion liquid in the step (1) is 0.1-0.2 g/100 mL;
the pH value of the alkaline nuclear body dispersion liquid is 8-9.
Preferably, the organic titanium source in the organic titanium source solution in the step (2) comprises tetrabutyl titanate; in the organic titanium source solution, the volume fraction of tetrabutyl titanate is 18-24%;
the dropping speed of the organic titanium source solution is 0.4-0.6 mL/min.
Preferably, the roasting temperature in the step (3) is 480-550 ℃, and the roasting time is 1.5-3 h.
Preferably, the concentration of the aqueous dispersion of the modified single-layer core-shell structure carrier in the step (5) is 0.2-0.3 g/100 mL;
the concentration of the graphene oxide aqueous dispersion is 4-6 mg/mL;
the volume ratio of the aqueous dispersion of the modified single-layer core-shell structure carrier to the aqueous dispersion of graphene oxide is 100: (15-30).
Preferably, the reducing agent of step (6) comprises sodium borohydride.
The invention also provides the application of the double-layer core-shell structure platinum catalyst in the technical scheme or the double-layer core-shell structure platinum catalyst prepared by the preparation method in the technical scheme in water catalytic decomposition.
The double-layer core-shell structure platinum catalyst provided by the invention comprises a core body and a shell layer, wherein the core body is a silicon dioxide microsphere; the shell layer sequentially comprises a titanium dioxide layer and a graphene oxide layer from inside to outside, and the titanium dioxide layer comprises anatase titanium dioxide; the graphene oxide layer is loaded with Pt. According to the preparation method, a silicon dioxide microsphere is used as a core body, anatase type titanium dioxide and graphene oxide are used as shell layers, and a core-shell structure coated by a titanium dioxide layer and a graphene oxide layer is formed, wherein the anatase type titanium dioxide layer and the graphene oxide layer are bonded through chemical bonds, so that charges are transferred from the titanium dioxide layer to the graphene oxide layer, the electron transfer rate is improved, and electron-hole recombination is inhibited to improve the photocatalysis efficiency of the catalyst; in addition, the present invention also utilizes the graphene oxide layer ratioThe structural characteristic of large surface area loads the active component Pt, and the catalytic activity of the catalyst is further improved. The results of the examples show that when the double-layer core-shell structure platinum catalyst provided by the invention is used for water catalytic decomposition, the hydrogen yield reaches 39.26mmol.g after 6h of reaction-1。
Drawings
FIG. 1 is a schematic flow chart of the present invention for preparing a platinum catalyst with a double-layer core-shell structure; in the figure, 1 is a silicon dioxide microsphere, 2 is a titanium dioxide layer, 3 is a graphene oxide layer, and 4 is Pt;
FIG. 2 is a scanning electron micrograph of the silica microspheres obtained in example 1;
FIG. 3 is an X-ray powder diffraction pattern of the platinum catalyst with a double-layer core-shell structure obtained in example 1;
FIG. 4 is a scanning electron microscope image of the platinum catalyst with a double-layer core-shell structure obtained in example 1;
FIG. 5 is a transmission electron microscope image of the platinum catalyst with a double-layer core-shell structure obtained in example 1;
FIG. 6 is a graph showing the relationship between time and hydrogen production in the photocatalytic water splitting reaction of the platinum catalyst with the double-layer core-shell structure obtained in example 1;
FIG. 7 is a graph showing a hydrogen production per hour distribution in a photocatalytic water splitting reaction of the platinum catalyst having the double-layer core-shell structure obtained in example 1.
Detailed Description
The invention provides a double-layer core-shell structure platinum catalyst, which comprises a core body and a shell layer, wherein the core body is a silicon dioxide microsphere; the shell layer sequentially comprises a titanium dioxide layer and a graphene oxide layer from inside to outside, and the titanium dioxide layer comprises anatase titanium dioxide; the graphene oxide layer is loaded with Pt.
The double-layer core-shell structure platinum catalyst provided by the invention comprises a core body, wherein the core body is a silicon dioxide microsphere, the diameter of the silicon dioxide microsphere is preferably 100-150 nm, more preferably 110-140 nm, and even more preferably 120-130 nm; the specific surface area of the silicon dioxide microspheres is preferably 27-30 m2·g-1More preferably 28 to 29m2·g-1(ii) a The pore diameter of the silicon dioxide microspheres is preferably 23-26 nm, and more preferably 23-26 nmIs 24 to 25 nm. In the present invention, the silica microspheres are preferably used
Figure BDA0001732078850000031
The preparation method preferably comprises the following steps:
mixing ethanol, water and ammonia water to obtain a mixed solvent;
and (3) dropwise adding a liquid-phase organic silicon source into the mixed solvent, and after hydrolysis reaction, sequentially carrying out solid-liquid separation, washing and drying on the reacted materials to obtain the silicon dioxide microspheres.
In the present invention, ethanol, water and ammonia water are preferably mixed to obtain a mixed solvent. The invention preferably utilizes ammonia water to promote the hydrolysis of the liquid-phase organic silicon source. According to the invention, ethanol and water are preferably used in combination to promote the solubility of the liquid-phase organic silicon source in the mixed solvent and provide a basis for obtaining the silica microspheres with proper pore diameters. In the present invention, the water is preferably deionized water.
In the invention, the volume ratio of ethanol to water to ammonia water is preferably (35-40): (60-70): 1. In the present invention, the mass concentration of the ammonia water is preferably 25 to 28%, and more preferably 26 to 27%. The ethanol is more preferably 36 to 38 parts, and the water is more preferably 62 to 69 parts, and more preferably 63 to 68.5 parts, based on 1 part by volume of the ammonia water. The mixing mode of the ethanol, the water and the ammonia water is not particularly required, and the method is well known by the technical personnel in the field.
After the mixed solvent is obtained, the method preferably drops a liquid-phase organic silicon source into the mixed solvent to perform a hydrolysis reaction of the liquid-phase organic silicon source, and then sequentially performs solid-liquid separation, washing and drying on the reacted materials to obtain the silicon dioxide microspheres. In the invention, the liquid-phase organic silicon source preferably comprises tetraethyl orthosilicate (TEOS), and the volume ratio of the liquid-phase organic silicon source to the mixed solvent is preferably 1: 28-35, and more preferably 1: 29-32.
The invention preferably drops the liquid-phase organic silicon source into the mixed solvent, and controls the hydrolysis speed of the liquid-phase organic silicon source to obtain the silicon dioxide microspheres with single dispersion phase. In the invention, the dropping speed of the liquid-phase organic silicon source is preferably 0.4-0.6 mL/min, and more preferably 0.45-0.55 mL/min.
And (3) after the liquid-phase organic silicon source is dropwise added, hydrolyzing the liquid-phase organic silicon source in the mixed solvent to generate the silicon dioxide microspheres. In the invention, the temperature of the liquid-phase organic silicon source hydrolysis reaction is preferably 15-30 ℃, and more preferably 20-25 ℃; the time of the hydrolysis reaction of the liquid-phase organic silicon source is preferably 25-40 min, and more preferably 28-35 min. In the invention, the liquid-phase organic silicon source hydrolysis reaction is preferably carried out under the condition of stirring, and the stirring speed is preferably 200-300 r/min, and more preferably 240-280 r/min; the stirring time is preferably the same as the time of the liquid-phase organic silicon source hydrolysis reaction in the technical scheme, and is not repeated here. The present invention does not require special embodiments of the stirring, as will be familiar to those skilled in the art.
After the liquid-phase organic silicon source hydrolysis reaction, the invention preferably performs solid-liquid separation on the reacted materials to obtain solid-phase silicon dioxide. In the invention, the solid-liquid separation preferably comprises centrifugal separation, and the rotating speed of the centrifugal separation is preferably 8000-9000 r/min, and further preferably 8400-8500 r/min; the time for centrifugal separation is preferably 4-6 min, and more preferably 5 min. The present invention does not require any particular implementation of the solid-liquid separation, and can be practiced in a manner well known to those skilled in the art.
After obtaining the solid phase silica, the present invention preferably washes the solid phase silica. In the invention, the washing preferably comprises deionized water washing and ethanol washing, and the times of the deionized water washing and the ethanol washing are independently preferably 2-4 times, and further preferably 3 times. In the present invention, the ethanol is preferably anhydrous ethanol.
After washing, the present invention preferably dries the washed material to remove the solvent from the washed material. The drying is preferably vacuum drying, and the pressure of the vacuum drying is preferably 0.07-0.08 MPa, and further preferably 0.075-0.078 MPa; the temperature of the vacuum drying is preferably 55-65 ℃, and further preferably 58-62 ℃; the drying time is preferably 12-24 hours, and more preferably 15-18 hours.
After drying, the invention grinds the dried material to obtain the silicon dioxide microspheres. The invention does not require the specific embodiment of the milling to obtain uniformly dispersed silica microspheres.
The double-layer core-shell structure platinum catalyst comprises a shell layer, wherein the shell layer sequentially comprises a titanium dioxide layer and a graphene oxide layer from inside to outside; the component of the titanium dioxide layer comprises anatase titanium dioxide; the thickness of the titanium dioxide layer is preferably 45-50 nm, and more preferably 46-48 nm; the thickness of the graphene oxide layer is preferably 3-5 nm, and more preferably 3.5-4.5 nm.
In the invention, the graphene oxide layer is loaded with Pt, and the catalytic performance of the catalyst is improved by utilizing the Pt. The supported amount (%) of Pt in the present invention is preferably 0.01 to 0.1%, more preferably 0.03 to 0.08%, and still more preferably 0.04 to 0.06%, in terms of (mass of catalyst after loading-mass before loading)/mass of catalyst after loading. In the present invention, the particle size of Pt is preferably 5 to 7nm, and more preferably 5.5 to 6.5 nm.
The double-layer core-shell structure platinum catalyst has a mesoporous structure, and the aperture of the double-layer core-shell structure platinum catalyst is less than or equal to 3.90 nm; the specific surface area of the double-layer core-shell structure platinum catalyst is 25.44m2(ii)/g; the average particle size of the double-layer core-shell structure platinum catalyst is 350-450 nm; the average pore volume of the double-layer core-shell structure platinum catalyst is 0.05cm3/g。
The invention provides a preparation method of a double-layer core-shell structure platinum catalyst, which comprises the following steps:
(1) providing an alkaline silica microsphere dispersion as an alkaline core dispersion;
(2) dropwise adding an organic titanium source solution into the alkaline core dispersion liquid, and performing hydrolysis reaction to obtain a single-layer core-shell structure carrier;
(3) sequentially grinding and roasting the single-layer core-shell structure carrier to obtain a crystalline single-layer core-shell structure carrier;
(4) carrying out amino modification on the crystalline single-layer core-shell structure carrier to obtain a modified single-layer core-shell structure carrier;
(5) dropwise adding the graphene oxide aqueous dispersion into the aqueous dispersion of the modified single-layer core-shell structure carrier, and carrying out a coating reaction to obtain a double-layer core-shell structure carrier;
(6) dipping the double-layer core-shell structure carrier into a platinic acid aqueous solution, and carrying out Pt loading to obtain a double-layer core-shell structure platinum catalyst; the platinic acid aqueous solution comprises platinic acid, a reducing agent and polyvinyl alcohol.
The invention provides an alkaline silica microsphere dispersion as an alkaline core dispersion. In the present invention, the silica microspheres in the alkaline silica microsphere dispersion are preferably identical to the silica microspheres in the above technical solution, and are not repeated here.
In the invention, the solvent in the silica microsphere dispersion liquid is preferably a mixed solvent, the mixed solvent preferably comprises ethanol and water, and the volume ratio of the ethanol to the water is preferably 100: 0.4-0.8, and more preferably 100: 0.4-0.6. In the invention, the mixed solution of ethanol and water is preferably used for dispersing the silicon dioxide microspheres, and the ethanol is used for controlling the decomposition rate of the organic titanium source so as to obtain the titanium dioxide coated silicon dioxide particles (SiO)2@TiO2)。
In the invention, the concentration of the silica microspheres in the silica microsphere dispersion liquid is preferably 0.1-0.2 g/100mL, and more preferably 0.12-0.19 g/100 mL.
In the invention, the pH value of the alkaline silicon dioxide microsphere dispersion liquid is preferably 8-9, and more preferably 8.5-9. The invention has no special requirements on the forming mode of the silicon dioxide microsphere dispersion liquid, and the mode known by the technical personnel in the field can be adopted.
In the present invention, the forming manner of the alkali silica microsphere dispersion preferably includes: mixing the silica microspheres with a solvent to obtain a silica microsphere dispersion liquid; the silica microsphere dispersion is then adjusted to be alkaline.
In the invention, the silicon dioxide microspheres are preferably mixed with the solvent, and further preferably, the silicon dioxide microspheres are firstly mixed with water in the solvent and then mixed with ethanol to obtain the silicon dioxide microsphere dispersion liquid.
After the silica microspheres are obtained, the silica microsphere dispersion is preferably adjusted to be alkaline in the invention. In the present invention, the regulator for regulating the pH of the silica microsphere dispersion preferably comprises hydroxypropyl cellulose (HPC). The invention has no special requirements on the adding mode and the adding amount of the hydroxypropyl cellulose, and can realize the control of the pH value of the alkaline nucleus dispersion liquid. In the invention, the hydroxypropyl cellulose can provide a needed alkaline environment for hydrolysis of an organic titanium source, and can also perform hydroxyl modification on the silicon dioxide microspheres to promote coating of titanium dioxide on the surfaces of the silicon dioxide microspheres.
After obtaining the alkaline core dispersion liquid, dropwise adding an organic titanium source solution into the alkaline core dispersion liquid, and performing hydrolysis reaction to obtain the single-layer core-shell structure carrier. According to the invention, the organic titanium source is added in a solution form, so that the organic titanium source can be coated on the surface of the silicon dioxide microspheres, and the titanium dioxide microspheres are prevented from being generated by the independent nucleation of the organic titanium source. In the present invention, the organic titanium source in the organic titanium source solution preferably includes n-tetrabutyl titanate (TBOT); the solvent in the organic titanium source solution is preferably the same as the solvent in the silica microsphere dispersion according to the above technical scheme, and is not repeated here. The organic titanium source solution is formed in a mode without special requirements, and is preferably obtained by dispersing under an ultrasonic condition. The invention has no requirement on the specific parameters of the ultrasonic dispersion, so that the organic titanium source can be uniformly dispersed in the solvent. In the invention, the volume fraction of n-tetrabutyl titanate in the organic titanium source solution is preferably 18 to 24%, more preferably 19 to 23%, and even more preferably 20 to 22%.
Dropwise adding an organic titanium source solution into a titanium dioxide microsphere dispersion solution; the dropping speed of the organic titanium source solution is preferably 0.4-0.6 mL/min, and more preferably 0.45-0.52 mL/min. According to the invention, the organic titanium source solution is added in a dropwise manner, so that the organic titanium source solution can be uniformly coated on the surface of the silicon dioxide microspheres, and agglomeration is avoided to form a non-uniform titanium dioxide coating layer.
In the invention, an organic titanium source in the organic titanium source solution is subjected to hydrolysis reaction under an alkaline condition to generate titanium dioxide, and particles of titanium dioxide coated silicon dioxide, namely a single-layer core-shell structure carrier, are obtained. In the present invention, the hydrolysis reaction temperature of the organic titanium source is preferably room temperature; the time of the hydrolysis reaction is preferably 2.5-4 h, and more preferably 3-3.5 h; the hydrolysis reaction is preferably carried out under stirring conditions, the stirring time is the same as that of the hydrolysis reaction in the technical scheme, and the stirring is not repeated.
After the single-layer core-shell structure carrier is obtained, the single-layer core-shell structure carrier is sequentially ground and roasted to obtain the crystalline single-layer core-shell structure carrier. The invention has no special requirements on the specific implementation mode of grinding, and only needs to obtain the single-layer core-shell structure carrier with small particles and uniform dispersion. In the invention, the roasting temperature is preferably 480-550 ℃, more preferably 495-540 ℃, and more preferably 500-520 ℃; the roasting time is preferably 1.5-3 h, more preferably 1.5-2.5 h, and even more preferably 2-2.5 h. In the invention, the roasting temperature is preferably reached by a heating mode, and the heating rate is preferably 3-8 ℃/min, more preferably 4-7 ℃/min, and even more preferably 5-6 ℃/min. In the present invention, the calcination is preferably performed in a muffle furnace.
The invention can convert the amorphous titanium dioxide into anatase phase titanium dioxide by roasting the single-layer core-shell structure carrier, thereby improving the catalytic activity of the catalyst.
After the crystalline single-layer core-shell structure carrier is obtained, amino modification is carried out on the crystalline single-layer core-shell structure carrier to obtain the modified single-layer core-shell structure carrier. In the present invention, the amino group-modifying agent preferably includes aminosilane, more preferably 3-Aminopropyltriethoxysilane (APTES). In the present invention, the method of amino modification preferably comprises:
and mixing the alcohol dispersion liquid of the crystalline single-layer core-shell structure carrier with an amino modification reagent, and carrying out solid-liquid separation after amino modification to obtain a solid, namely the modified single-layer core-shell structure carrier.
In the invention, the concentration of the crystalline state single-layer core-shell structure carrier in the alcohol dispersion liquid is preferably 0.25-0.4 g/100mL, and more preferably 0.3-0.35 g/100 mL; the solvent in the alcohol dispersion liquid preferably includes ethanol, and more preferably anhydrous ethanol. The invention does not require any particular way of forming the alcohol dispersion, and can be carried out in a manner known to those skilled in the art. In the present invention, the volume ratio of the amino modifier to the crystalline monolayer core-shell structure carrier alcohol dispersion is preferably 100: 0.8 to 1.2, and more preferably 100:1 to 1.1.
According to the invention, the amino modification is carried out on the crystalline single-layer core-shell structure carrier, so that graphene oxide can be coated on the outer surface of the crystalline single-layer core-shell structure carrier to form a graphene oxide layer. In the invention, the modification of the crystalline single-layer core-shell structure carrier by the amino modifier is preferably carried out under the stirring condition, and the stirring speed is preferably 200-300 r/min, and more preferably 240-260 r/min; the stirring time is preferably 20-25 h, and more preferably 23-24 h.
After amino modification, solid-liquid separation is preferably carried out on the material subjected to amino modification to obtain the modified single-layer core-shell structure carrier. In the present invention, the solid-liquid separation is preferably performed by centrifugal separation, and the present invention does not require any particular embodiment of the centrifugal separation, and may be performed by methods well known to those skilled in the art. After centrifugation, the solid material obtained by centrifugation is washed by the method, and the washing detergent preferably comprises ethanol. After washing, the washed modified single-layer core-shell structure carrier is soaked in ethanol so as to keep the wettability of the modified single-layer core-shell structure carrier, and favorable conditions are provided for the subsequent coating reaction of the graphene oxide layer.
After the modified single-layer core-shell structure carrier is obtained, dropwise adding graphene oxide aqueous dispersion into the aqueous dispersion of the modified single-layer core-shell structure carrier for coating reaction, and then washing solid materials in reaction liquid to obtain the double-layer core-shell structure carrier.
In the present invention, the graphene oxide in the graphene oxide aqueous dispersion is preferably obtained by self-control, and the preparation method of the graphene oxide preferably includes the following steps:
(a) mixing graphite, concentrated sulfuric acid, phosphoric acid and potassium permanganate under the condition of ice-water bath to obtain reaction feed liquid;
(b) heating the reaction liquid in the step (a) to an oxidation reaction temperature, and then carrying out oxidation reaction to obtain an oxidation product mixture; the temperature of the oxidation reaction is 45-60 ℃;
(c) and (c) mixing the oxidation product mixture obtained in the step (b) with hydrogen peroxide to perform an oxidation-reduction reaction, and then sequentially performing solid-liquid separation, washing and drying on the obtained reaction mixture to obtain the graphene oxide.
The invention preferably mixes graphite, concentrated sulfuric acid, phosphoric acid and potassium permanganate under the ice-water bath condition to obtain reaction feed liquid. In the invention, the graphite is preferably graphite powder, and the particle size of the graphite powder is preferably 30-50 nm, and more preferably 40-45 nm; the mass concentration of the concentrated sulfuric acid is preferably 96-98%, and more preferably 98%; the mass concentration of the phosphoric acid is preferably 82-85%, and more preferably 85%. The preferable dosage ratio of the graphite, the concentrated sulfuric acid, the phosphoric acid and the potassium permanganate is 1 g: (100-130) mL, (10-15) mL, (5-8) g, more preferably 1 g: 120-125 mL, (13-14) mL, (6-7) g.
In the invention, graphite, concentrated sulfuric acid and phosphoric acid are preferably mixed firstly, and then potassium permanganate is added into the mixed solution of the graphite, the concentrated sulfuric acid and the phosphoric acid. In the invention, the addition rate of the potassium permanganate is preferably 0.20-0.35 g/min, and more preferably 0.25-0.30 g/min. In the invention, the reaction of potassium permanganate, concentrated sulfuric acid and phosphoric acid with graphite is a violent oxidation reaction, a large amount of heat can be released in the reaction process, and the potassium permanganate is added under the condition of ice-water bath, so that the temperature can be rapidly reduced, and explosion caused by heat release is prevented.
After the potassium permanganate is added, the mixture of graphite, concentrated sulfuric acid, phosphoric acid and potassium permanganate is preferably stirred so as to uniformly mix the mixture, and the reaction material liquid is obtained. In the invention, the mixture of graphite, concentrated sulfuric acid, phosphoric acid and potassium permanganate is preferably stirred under the condition of oil bath, and the temperature of the oil bath is preferably 30-36 ℃, and more preferably 32-35 ℃.
After the reaction liquid is obtained, the reaction liquid is preferably heated to the oxidation reaction temperature, so that graphite, potassium permanganate, sulfuric acid and phosphoric acid are mixed to obtain an oxidation product mixture. In the invention, the temperature of the oxidation reaction is preferably 45-60 ℃, and more preferably 48-55 ℃; the time of the oxidation reaction is preferably 10-15 hours, and more preferably 12-13 hours. The present invention has no special requirement for the specific implementation mode of the temperature rise, and the mode known by the technical personnel in the field can be adopted. In the invention, the oxidation product mixture comprises oxidized graphene generated by oxidation, unreacted potassium permanganate and reduction products of potassium permanganate, sulfuric acid and phosphoric acid.
After obtaining the oxidation product mixture, the invention preferably mixes the oxidation product mixture with hydrogen peroxide, and then sequentially performs solid-liquid separation, washing and drying on the obtained mixture to obtain the graphene oxide. Preferably, the temperature of the oxidation product mixture is reduced to room temperature, and then the oxidation product mixture is mixed with hydrogen peroxide; the cooling mode of the oxidation product mixture is preferably natural cooling. According to the invention, the cooled oxidation product mixture is mixed with hydrogen peroxide, and the hydrogen peroxide and potassium permanganate perform oxidation-reduction reaction, so that unreacted potassium permanganate in the oxidation product mixture can be removed, and the influence of the potassium permanganate on the color of the graphene oxide is avoided; and the product generated by oxidizing the hydrogen peroxide is oxygen which is easy to remove, so that the generation of new impurities is avoided. In the present invention, the hydrogen peroxide solution preferably has a mass concentration of 30%. The invention has no special requirement on the dosage of the hydrogen peroxide, and is suitable for fully removing the unreacted potassium permanganate.
After the redox reaction, the invention preferably performs solid-liquid separation on the mixture after the reaction to obtain a solid phase; the solid-liquid separation is preferably performed by centrifugation, which is preferably performed by means well known to those skilled in the art. After obtaining the solid phase, the present invention preferably washes the solid phase; the washing preferably comprises acid washing, alcohol washing and water washing in sequence; the washing liquid for acid washing preferably comprises dilute hydrochloric acid, the dilute hydrochloric acid is preferably prepared from concentrated hydrochloric acid and deionized water according to the volume ratio of 1:1, and the concentrated hydrochloric acid is 12 mol/L. In the present invention, the alcohol washing detergent is preferably ethanol, and is more preferably absolute ethanol; the water-washing detergent preferably comprises deionized water. The present invention does not require special embodiments of the washing, and can be used as is well known to those skilled in the art.
After washing, the washed materials are preferably dried to obtain graphene oxide; the drying mode is preferably freeze drying, so that the uniformly dispersed graphene oxide is obtained, and agglomeration is avoided. The present invention does not require any particular embodiment of the freeze-drying process, and can be practiced in a manner well known to those skilled in the art.
According to the invention, the graphene oxide is preferably prepared according to the method, the graphene oxide with a large specific surface area can be obtained, and a proper graphene oxide layer is provided for loading Pt.
In the invention, the concentration of the graphene oxide aqueous dispersion liquid is preferably 4-6 mg/mL, and more preferably 4.3-5.8 mg/mL; the mass concentration of the modified single-layer core-shell structure carrier aqueous dispersion is preferably 0.2-0.3 g/100mL, and more preferably 0.24-0.28 g/100 mL; in the invention, the water in the modified single-layer core-shell structure carrier aqueous dispersion and the water in the graphene oxide aqueous dispersion are independently preferably deionized water. In the invention, the volume ratio of the modified single-layer core-shell structure carrier aqueous dispersion to the graphene oxide aqueous dispersion is preferably 100: (15-30), more preferably 100: (18-26).
According to the invention, the graphene oxide aqueous dispersion is mixed with the modified single-layer core-shell structure carrier in a dropwise manner, so that graphene oxide can be uniformly dispersed and coated on the surface of the modified single-layer core-shell structure carrier, and a uniform graphene oxide layer is further formed. In the invention, the dropping speed of the graphene oxide aqueous dispersion liquid is preferably 0.45-0.6 mL/min, and more preferably 0.5-0.55 mL/min.
In the invention, after the graphene oxide aqueous dispersion is dripped, the anionic groups on the surface of the graphene oxide in the mixture are bonded with the amino groups on the outer surface of the modified single-layer core-shell structure carrier, so that the coating reaction of the graphene oxide layer on the outer surface of the modified single-layer core-shell structure carrier is completed. In the invention, the coating reaction is preferably carried out under the condition of stirring, and the stirring speed is preferably 200-400 r/min, and more preferably 240-320 r/min; the stirring time is preferably 3-5 h, and more preferably 4-4.5 h. The stirring time of the invention is the coating reaction time.
After the coating reaction, the invention preferably carries out solid-liquid separation on the materials after the coating reaction to obtain solid materials; the solid-liquid separation is preferably performed by centrifugal separation. The present invention does not require special embodiments of the centrifugation, and can be carried out in a manner well known to those skilled in the art. After the solid material is obtained, the solid material is preferably washed, and the washing detergent is preferably water, and is further preferably deionized water; the number of washing is preferably 2 to 5, and more preferably 3 to 4. The present invention does not require any particular manner of washing, and may be carried out in a manner known to those skilled in the art. According to the invention, the solid material is washed, and the amino modifier between the graphene oxide and the modified monolayer core-shell structure carrier can be removed.
After washing, the washed materials are preferably dried to obtain the double-layer core-shell structure carrier (SiO)2@TiO2@ GO); the drying temperature is preferably 50-65 ℃, and more preferably 55-60 ℃; the drying time is preferably 12-15 hours, and more preferably 13-14 hours. The present invention does not require special embodiments of the drying process, and can be carried out in a manner known to those skilled in the art.
After the double-layer core-shell structure carrier is obtained, the double-layer core-shell structure carrier is soaked into a platinic acid aqueous solution for PtAnd loading to obtain the double-layer core-shell structure platinum catalyst. In the present invention, the aqueous platinic acid solution includes platinic acid, a reducing agent, and polyvinyl alcohol; the platinic acid preferably comprises chloroplatinic acid (HPtCl)2) (ii) a The reducing agent preferably comprises sodium borohydride. In the invention, the mass concentration of the platinic acid in the platinic acid aqueous solution is preferably 0.046-0.23 g/L, and more preferably 0.05-0.2 g/L; the mass concentration of the reducing agent is preferably 0.05-0.25 g/L, and more preferably 0.07-0.20 g/L; the mass concentration of the polyvinyl alcohol is preferably 0.036 to 0.18g/L, and more preferably 0.04 to 0.16 g/L.
The preparation method of the platinic acid aqueous solution preferably comprises the following steps:
mixing a platinic acid aqueous solution with a polyvinyl alcohol aqueous solution to obtain a mixed solution; and then mixing the mixed solution with a reducing agent aqueous solution to obtain a platinic acid aqueous solution.
According to the invention, the platinic acid aqueous solution and the polyvinyl alcohol aqueous solution are preferably mixed, and the platinum ions ionized from the platinic acid are effectively isolated by utilizing the high molecular polymer polyvinyl alcohol, so that the reduction speed of the platinum ions is reduced, and further the platinum simple substance with smaller particles is obtained. In the invention, the concentration of the platinic acid aqueous solution is preferably 0.045-0.055 g/L, and more preferably 0.05-0.052 g/L; the mass concentration of the polyvinyl alcohol aqueous solution is preferably 0.8 to 1.2%, and more preferably 1 to 1.1%. The mixing according to the invention is preferably carried out under stirring.
After the mixed solution is obtained, the mixed solution is mixed with the reducing agent aqueous solution to obtain the platinum acid aqueous solution. In the present invention, the concentration of the reducing agent aqueous solution is preferably 0.1 to 0.15mol/L, and more preferably 0.1 to 0.12 mol/L. The invention has no special requirement on the mixing mode of the mixed solution and the aqueous solution of the reducing agent, and the mixing mode which is well known by the technical personnel in the field can be adopted.
The method comprises the steps of dipping a double-layer core-shell structure carrier into a platinic acid aqueous solution, wherein in the dipping process, a reducing agent in the platinic acid aqueous solution and platinum ions generate an oxidation-reduction reaction to generate metal Pt; the polyvinyl alcohol can improve the dispersibility of platinum ions in the solution, so that the generated Pt simple substance particles are fine and can be uniformly loaded on the graphene oxide layer, and the double-layer core-shell structure platinum catalyst is further obtained. In the present invention, the ratio of the mass of the bilayer structure carrier to the volume of the aqueous platinic acid solution is preferably 0.25g to 0.3 g: 100mL, more preferably 0.027 to 0.28 g: 100 mL. The Pt loading process of the present invention is preferably carried out under agitation in a manner well known to those skilled in the art to allow sufficient contact of the components.
After the Pt loading is completed, the present invention preferably performs solid-liquid separation on the reacted material, and the solid-liquid separation is preferably performed by centrifugal separation, and the specific implementation of the centrifugal separation can be performed by a method well known to those skilled in the art. After solid-liquid separation, the solid material obtained after the separation is preferably washed, and more preferably washed by deionized water; the washing mode is a washing mode which is well known to those skilled in the art, so that the impurities on the surface of the solid material can be removed. After washing, the invention preferably dries the washed material to obtain the double-layer core-shell structure platinum catalyst. In the invention, the drying temperature is preferably 50-65 ℃, and more preferably 60-62 ℃; the drying time is preferably 20-25 h, and more preferably 22-24 h.
In the process of preparing the double-layer core-shell structure platinum catalyst by the preparation method according to the technical scheme of the invention, except for the existing description, other raw materials are all commercial products well known to those skilled in the art. In the invention, in each step of preparing the platinum catalyst with the double-layer core-shell structure by the preparation method in the technical scheme, the preparation is preferably carried out under a sealed condition so as to avoid the interference of external impurities. The preparation methods described in the above technical schemes are not mentioned, and are all methods well known to those skilled in the art.
The invention also provides the application of the double-layer core-shell structure platinum catalyst in the technical scheme or the double-layer core-shell structure platinum catalyst prepared by the preparation method in the technical scheme in water catalytic decomposition. In the present invention, the application preferably includes:
under the vacuum condition, mixing a double-layer core-shell structure platinum catalyst, methanol and deionized water to obtain reaction mixed feed liquid; and carrying out ultraviolet irradiation on the reaction mixed material liquid to carry out water catalytic decomposition reaction to obtain hydrogen.
According to the invention, the double-layer core-shell structure platinum catalyst, methanol and deionized water are preferably mixed under a vacuum condition to obtain the reaction mixed feed liquid. In the present invention, the pressure of the vacuum is preferably 0.4 MPa. The invention preferably carries out the water catalytic decomposition reaction under the vacuum condition, can eliminate the interference of oxygen in the air and promote the water catalytic decomposition reaction. In the invention, the dosage ratio of the double-layer core-shell structure platinum catalyst, methanol and deionized water is preferably 25 mg: (18-24) mL: (70-90) mL, more preferably 25 mg: (20-21) mL: (75-85) mL. The invention takes methanol as an electron donor to promote the water catalytic decomposition reaction. The mixing of the double-layer core-shell structure platinum catalyst, methanol and deionized water is preferably carried out by ultrasonic dispersion, and the invention has no special requirements on the specific implementation mode of the ultrasonic dispersion and adopts a mode which is well known by the technical personnel in the field.
After the reaction mixed material liquid is obtained, the invention preferably carries out ultraviolet irradiation on the reaction mixed material liquid, and water in the reaction mixed material is subjected to water catalytic decomposition reaction under the action of the double-layer core-shell structure platinum catalyst to obtain the hydrogen. In the present invention, the wavelength of the ultraviolet light for ultraviolet irradiation is preferably 365 to 400nm, and more preferably 365 to 370 nm. The time of the ultraviolet irradiation is not particularly required in the present invention, and those skilled in the art can use the ultraviolet irradiation. The hydrogen yield of the water catalytic decomposition reaction is 39.26mmol.g when the hydrogen yield of the water catalytic decomposition reaction is measured by ultraviolet irradiation for 6h-1。
In order to further illustrate the present invention, the following detailed description of the platinum catalyst with a double-layer core-shell structure, the preparation method and the application thereof are provided with reference to the accompanying drawings and examples, which should not be construed as limiting the scope of the present invention.
Example 1
By classic
Figure BDA0001732078850000141
MethodPreparation of nano SiO2And (3) microspheres. 368mL of absolute ethyl alcohol (EtOH), 68.8mL of deionized water and 10.0mL of 25% ammonia water are added into a 500mL clean beaker, and the mixture is stirred at normal temperature for 30min to obtain a core dispersion liquid with the pH value of 9;
14.0mL of tetraethyl orthosilicate (TEOS) was added dropwise to the obtained core dispersion, and the hydrolysis of tetraethyl orthosilicate was carried out by placing a beaker in an oil bath pan at 25 ℃ and stirring with a magnet at a rate of 260r/min for 4 hours. And (4) after the hydrolysis reaction is finished, centrifuging the product for 5min under the condition of 8500 r/min. And then washing the sample with deionized water for three times, then washing the sample with absolute ethyl alcohol for three times, drying the sample in a vacuum oven at 60 ℃ and 0.075MPa, and grinding the dried sample to obtain the silicon dioxide microspheres which are white as a whole and have purple luster when spread.
1g of graphite powder and 120mL of concentrated sulfuric acid (H) are added into a three-neck flask2SO4) 13.3mL phosphoric acid (H)3PO4) Stirring in ice-water bath, and weighing 6g potassium permanganate (KMnO)4) Slowly adding into flask within 20min, adding KMnO4After stirring in an ice-water bath, the flask with the added reactants was stirred in an oil bath at 35 ℃ for 30min, and the temperature of the oil bath was raised to 50 ℃ for 12 h. After the reaction is finished, the mixture is cooled to room temperature, and 10mL of 30% hydrogen peroxide (H) is slowly poured into the reaction product2O2) And 150mL of deionized water were stirred until no gas was generated, and then the mixture was centrifuged. Washing the product with a mixed solution of concentrated hydrochloric acid (HCl) and deionized water in a volume ratio of 1:1 for three times, washing with deionized water for three times, washing with absolute ethyl alcohol for three times, washing with deionized water for one more time finally, transferring the product onto a watch glass, and drying with a freeze dryer to obtain the graphene oxide.
Preparing a platinum catalyst with a double-layer core-shell structure according to a flow schematic diagram shown in FIG. 1:
100ml of absolute ethanol was added to a 250ml round bottom flask, and 0.4g of hydroxypropyl cellulose (HPC) was weighed into the flask and dissolved by stirring. Then add the dispersed 0.2g SiO2The microspheres were stirred with 0.4mL of distilled water for 30 minutes.Then 4mL of tetra-n-butyl titanate (TBOT) was added to 20mL of absolute ethanol and stirred well. Then, TBOT solution was added dropwise to the flask at a rate of 0.5mL/min, and the solution became further white in color during the addition. Stirring for 30min after the solution is added dropwise, and placing the mixture into a constant-temperature oil bath at 85 ℃ for reaction for 100 min. After the reaction is finished, centrifugally separating the product (the condition is 8000r/min), washing the product for 5 times by using ethanol, and drying the product for 6 hours at the temperature of 65 ℃ to obtain the single-layer core-shell structure carrier (SiO)2@TiO2)；
Prepared SiO2@TiO2Fully grinding, heating the temperature to 500 ℃ by using a muffle furnace for sample sintering at the heating rate of 5 ℃/min, roasting for 2h, and naturally cooling to room temperature to obtain the crystalline titanium single-layer core-shell structure carrier;
0.6g of calcined SiO are weighed2@TiO2Dispersing in 200mL absolute ethyl alcohol, dropwise adding APTES4mL, stirring and reacting for 24h, performing amino modification, centrifuging to separate the product, washing with EtOH for 5 times, and dropwise adding 20mL (concentration of 100mg/20mL) Graphene Oxide (GO) aqueous dispersion to amino-modified SiO2@TiO2And stirring the dispersion liquid for reaction for 4 hours, centrifugally separating a reaction product, washing the separated solid with water for three times, and drying the solid at the temperature of 60 ℃ for 12 hours to obtain the double-layer core-shell structure carrier. (SiO)2@TiO2@GO)。
52.5mL of 1g/L chloroplatinic acid (HPtCl) was measured2) The solution is diluted to 200mL, 3.6mL of 1% polyvinyl alcohol (PVA) solution is added, after stirring for 30min, 15mL of fresh 0.1mol/L sodium borohydride (NaBH)4) The solution is stirred for 30min and then 0.2g of carrier SiO is added2@TiO2@ GO (C), sealing the beaker by using a preservative film, and continuously stirring for reaction for 4 hours. And after the reaction is finished, centrifugally separating out a product, washing with water for 3 times, and drying at 60 ℃ for 24 hours to obtain the double-layer core-shell structure platinum catalyst with the Pt loading amount of 0.06%.
Comparative example 1
A platinum catalyst having a double-layer core-shell structure was prepared in the same manner as in example 1, except that after preparing a single-layer core-shell structure carrier, the sample was not calcined in a muffle furnace, and TiO in the carrier was not oxidized2Is in an amorphous state.
0.6g of SiO are weighed2@TiO2Dispersing in 200mL of absolute ethyl alcohol, dropwise adding APTES4mL, stirring for reaction for 24h, modifying amino group, then centrifugally separating the product, washing with EtOH for 5 times, and directly dropwise adding 20mL (concentration is 100mg/20mL) of Graphene Oxide (GO) aqueous dispersion to amino group-modified SiO2@TiO2And stirring the dispersion liquid for reaction for 4 hours, then centrifugally separating a reaction product, washing the obtained solid material with water for three times, and drying the solid material at the temperature of 60 ℃ for 12 hours to obtain the double-layer core-shell structure carrier. (SiO)2@TiO2@GO)。
52.5mL of 1g/L chloroplatinic acid (HPtCl) was measured2) The solution is diluted to 200mL, 3.6mL of 1% polyvinyl alcohol (PVA) solution is added, after stirring for 30min, 15mL of fresh 0.1mol/L sodium borohydride (NaBH)4) The solution is stirred for 30min and then 0.2g of carrier SiO is added2@TiO2@ GO (C), sealing the beaker by using a preservative film, and continuously stirring for reaction for 4 hours. And after the reaction is finished, centrifugally separating out a product, washing with water for 3 times, and drying at 60 ℃ for 24 hours to obtain the double-layer core-shell structure platinum catalyst with the Pt loading amount of 0.06%.
Comparative example 2
A double-layer core-shell structure support was prepared according to the method of example 1, except that the step of supporting Pt was not included.
Characterization of Performance and results
The morphology of the silica microspheres obtained in example 1 is characterized by a scanning electron microscope, and fig. 2 is an SEM image at 5000 and 250000 magnifications, and it can be seen from fig. 2 that the silica microspheres prepared by the present invention have good sphericity and monodispersity. The obtained silicon dioxide microspheres have the particle size distribution range of 100-150 nm and the specific surface area of about 29m2Per g, pore size 24.6 nm.
The chemical composition of the platinum catalyst with a double-layer core-shell structure obtained in example 1 was characterized by X-ray powder diffraction technique, and FIG. 3 is the characterization result of example 1, consisting of Pt/SiO2@TiO2The XRD spectrum of/GO (C) can obviously see sharp diffraction peaks with 2 theta of 25.4 degrees, 37.8 degrees, 48.1 degrees, 55.2 degrees and 60.0 degrees, which respectively correspond to anatase TiO2(JCPDS No.21-1272) The (101), (004), (200), (105) and (211) planes of (A) indicate that the TiO with anatase phase on the surface is formed after the calcination treatment at 500 DEG C2And (4) shell layer.
The morphology of the double-layer core-shell platinum catalyst obtained in example 1 was characterized by a scanning electron microscope and a transmission electron microscope, and the result is shown in fig. 4. FIG. 4 is an SEM picture of a catalyst product obtained in example 1, and FIG. 5 is a TEM picture of a catalyst obtained in example 1; from FIG. 4, it can be seen that the catalyst is monodisperse, uniform-sized particles; the rough filaments on the surface of the catalyst are graphene oxide and have no obvious metal particles. As can be seen from fig. 5, the catalyst exhibited lattice fringes, and the measurement of the lattice fringes revealed that d ═ 0.326nm was the lattice fringe of the Pt (220) crystal plane, indicating that the catalyst surface supported metallic Pt particles.
By using N2The isothermal adsorption-desorption method of (1) is characterized by the structure of the platinum catalyst with the double-layer core-shell structure obtained in example 1 by using Brunauer-Emmett-teller (bet) model ASAP2010, produced by Micromeritics, usa, and test results show that the platinum catalyst with the double-layer core-shell structure obtained in example 1 has a mesoporous structure and has a large specific surface area and a large pore volume, and specific test results are listed in table 1.
The structural characteristics of comparative examples 1 to 2 were characterized in the same manner, and the results are shown in Table 1.
The photocatalytic performance of the products obtained in example 1 and comparative examples 1 and 2 was tested by catalyzing the reaction of photolyzing water, and the test results are shown in fig. 6 and 7. Fig. 6 is a graph showing a relationship between time and hydrogen production in a photocatalytic water splitting reaction of the platinum catalyst with the double-layer core-shell structure obtained in example 1, and fig. 7 is a distribution diagram showing a hydrogen production per hour in the photocatalytic water splitting reaction of the platinum catalyst with the double-layer core-shell structure obtained in example 1. As can be seen from FIGS. 6 and 7, the double-layer core-shell structure platinum catalyst provided by the invention has good catalytic activity, 39.26mmol/g in 6h, and the specific test results are shown in Table 1.
Table 1 results of structural and catalytic performance characterization of the products obtained in example 1, comparative examples 1 and 2
Figure BDA0001732078850000171
As can be seen from table 1, compared with the catalyst with an amorphous titania layer (comparative example 1), the platinum catalyst with a double-layer core-shell structure provided by the invention has the advantages that although the specific surface area is reduced, the catalytic performance is improved by nearly 50%; compared with a product without Pt (comparative example 2), the catalytic performance is improved by more than 40 times.
According to the embodiment, the double-layer core-shell structure platinum catalyst provided by the invention takes titanium dioxide and graphene oxide as composite carriers, and after precious metal Pt is loaded on the surface of the graphene oxide, the catalyst can be used for water catalytic decomposition reaction under the condition that the loading amount is only 0.01-0.1%, and the catalytic rate can reach 39.26mmol/g after 6 hours of reaction.
Although the present invention has been described in detail with reference to the above embodiments, it is only a part of the embodiments of the present invention, not all of the embodiments, and other embodiments can be obtained without inventive step according to the embodiments, and the embodiments are within the scope of the present invention.

Claims (8)

1. A double-layer core-shell structure platinum catalyst comprises a core body and a shell layer, wherein the core body is a silicon dioxide microsphere; the shell layer sequentially comprises a titanium dioxide layer and a graphene oxide layer from inside to outside, and the titanium dioxide layer comprises anatase titanium dioxide; the graphene oxide layer is loaded with Pt; the preparation method of the double-layer core-shell structure platinum catalyst comprises the following steps:
(1) providing an alkaline silica microsphere dispersion as an alkaline core dispersion;
(2) dropwise adding an organic titanium source solution into the alkaline core dispersion liquid, and performing hydrolysis reaction to obtain a single-layer core-shell structure carrier;
(3) sequentially grinding and roasting the single-layer core-shell structure carrier to obtain a crystalline single-layer core-shell structure carrier;
(4) carrying out amino modification on the crystalline single-layer core-shell structure carrier to obtain a modified single-layer core-shell structure carrier;
(5) dropwise adding the graphene oxide aqueous dispersion into the aqueous dispersion of the modified single-layer core-shell structure carrier for coating reaction, and then washing a solid material in a reaction liquid to obtain a double-layer core-shell structure carrier;
(6) dipping the double-layer core-shell structure carrier into a platinic acid aqueous solution, and carrying out Pt loading to obtain a double-layer core-shell structure platinum catalyst; the platinic acid aqueous solution comprises platinic acid, a reducing agent and polyvinyl alcohol;
the organic titanium source in the organic titanium source solution in the step (2) comprises tetrabutyl titanate; in the organic titanium source solution, the volume fraction of tetrabutyl titanate is 18-24%;
the dropping speed of the organic titanium source solution is 0.4-0.6 mL/min;
the roasting temperature in the step (3) is 480-550 ℃, and the roasting time is 1.5-3 h.
2. The double-layer core-shell structure platinum catalyst as claimed in claim 1, wherein the diameter of the silica microspheres is 100-150 nm, the thickness of the titanium dioxide layer is 45-50 nm, and the thickness of the graphene oxide layer is 3-5 nm.
3. The double-layer core-shell structure platinum catalyst according to claim 1, wherein the loading amount of Pt in graphene oxide is 0.01-0.1 wt.%; the particle size of the Pt is 5-7 nm.
4. The preparation method of the double-layer core-shell structure platinum catalyst as claimed in any one of claims 1 to 3, comprising the following steps:
(1) providing an alkaline silica microsphere dispersion as an alkaline core dispersion;
(2) dropwise adding an organic titanium source solution into the alkaline core dispersion liquid, and performing hydrolysis reaction to obtain a single-layer core-shell structure carrier;
(3) sequentially grinding and roasting the single-layer core-shell structure carrier to obtain a crystalline single-layer core-shell structure carrier;
(4) carrying out amino modification on the crystalline single-layer core-shell structure carrier to obtain a modified single-layer core-shell structure carrier;
(5) dropwise adding the graphene oxide aqueous dispersion into the aqueous dispersion of the modified single-layer core-shell structure carrier for coating reaction, and then washing a solid material in a reaction liquid to obtain a double-layer core-shell structure carrier;
(6) dipping the double-layer core-shell structure carrier into a platinic acid aqueous solution, and carrying out Pt loading to obtain a double-layer core-shell structure platinum catalyst; the platinic acid aqueous solution comprises platinic acid, a reducing agent and polyvinyl alcohol; the organic titanium source in the organic titanium source solution in the step (2) comprises tetrabutyl titanate; in the organic titanium source solution, the volume fraction of tetrabutyl titanate is 18-24%; the dropping speed of the organic titanium source solution is 0.4-0.6 mL/min;
the roasting temperature in the step (3) is 480-550 ℃, and the roasting time is 1.5-3 h.
5. The preparation method according to claim 4, wherein the concentration of the silica microspheres in the silica microsphere dispersion in the step (1) is 0.1 to 0.2g/100 mL;
the pH value of the alkaline nuclear body dispersion liquid is 8-9.
6. The preparation method according to claim 4, wherein the concentration of the aqueous dispersion of the modified single-layer core-shell structure carrier in the step (5) is 0.2-0.3 g/100 mL;
the concentration of the graphene oxide aqueous dispersion is 4-6 mg/mL;
the volume ratio of the aqueous dispersion of the modified single-layer core-shell structure carrier to the aqueous dispersion of graphene oxide is 100: (15-30).
7. The method of claim 4, wherein the reducing agent of step (6) comprises sodium borohydride.
8. The application of the double-layer core-shell structure platinum catalyst according to any one of claims 1 to 3 or the double-layer core-shell structure platinum catalyst prepared by the preparation method according to any one of claims 4 to 7 in water catalytic decomposition.
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