WO2014042259A1

WO2014042259A1 - Method for carrying metal on graphene oxide and metal-graphene oxide composite created with said method

Info

Publication number: WO2014042259A1
Application number: PCT/JP2013/074937
Authority: WO
Inventors: 勇太仁科
Original assignee: 国立大学法人岡山大学
Priority date: 2012-09-13
Filing date: 2013-09-13
Publication date: 2014-03-20
Also published as: JP6116016B2; JPWO2014042259A1

Abstract

Provided are: a method for carrying a metal on graphene oxide, in which a desired metal is carried on graphene oxide while suppressing the occurrence of graphene aggregation in a graphene oxide dispersion in which graphene oxide is dispersed; and a metal-graphene oxide composite created with this method. A solution containing a metal salt or metal ions is added to a graphene oxide dispersion solution in which graphene oxide is dispersed. At least one of alcohol (except tertiary alcohols), N,N-dimethylformamide, tetrahydrofuran, and 1,4-dioxane is added as a reducing agent. The reducing action of the reducing agent causes the graphene oxide to carry the metal of the metal salt or metal that has become the metal ions.

Description

Method of supporting metal on graphene oxide and metal-graphene oxide composite prepared by this method

The present invention relates to a method of supporting a metal on graphene oxide and a metal-graphene oxide composite prepared by this method. In particular, by reducing graphene oxide, the metal is supported on graphene oxide. At that time, the graphene oxide is reduced to graphene, which suppresses the decrease in dispersibility and maintains the dispersibility of graphene oxide. The metal-graphene oxide composite can be produced and used as a catalyst or a metal scavenger.

Conventionally, a catalyst comprising a palladium-graphene complex is known as one of the catalysts (see, for example, Patent Document 1).

This catalyst is prepared by adding palladium nitrate and hydrazine to a graphene oxide dispersion liquid in which graphene oxide is dispersed, and irradiating with microwaves, thereby supporting graphene oxide on palladium.

However, when hydrazine is used as the reducing agent, not only palladium is supported on graphene oxide by the reduction reaction, but also graphene oxide is reduced to graphene, and graphene aggregation is likely to occur. There was a problem.

In particular, the agglomerated graphene is less likely to exhibit a function as a catalyst, and the dispersibility in the solution is reduced, so that it is necessary to remove the agglomerated graphene. Was also a cause of high costs.

International Publication No. 2011-119961

The present inventor considers that the use of a reducing agent having a strong reducing action such as hydrazine as a reducing agent is a cause of causing graphene aggregation, and a reducing agent having a mild reducing action that does not cause graphene aggregation. By using it, it was thought that a metal can be supported without impairing the dispersibility of graphene oxide as much as possible, and the present invention has been achieved by conducting research and development.

In particular, it has been found that it can be used not only as a catalyst having high dispersibility of the original purpose but also as a metal scavenger for capturing and recovering metal by graphene oxide.

In the method for supporting a metal on graphene oxide of the present invention, a first step of preparing a mixed solution by adding a solution containing a metal salt or metal ion to a graphene oxide dispersion solution in which graphene oxide is dispersed And adding at least one of alcohol (excluding tertiary alcohol), N, N-dimethylformamide, tetrahydrofuran, and 1,4-dioxane to the mixed solution and stirring the graphene oxide in the graphene oxide dispersion solution. And a second step of supporting a metal that is a metal salt or a metal ion.

Furthermore, in the method of supporting a metal on graphene oxide according to the present invention, the graphene oxide dispersion solution is irradiated with microwaves on graphite, which is a laminate of carbon sheets composed of carbon atoms arranged in a hexagonal lattice. Also characterized in that it is made by peeling off into one or more carbon sheets by adding sulfuric acid, sodium nitrate and potassium permanganate to graphite irradiated with microwaves and oxidizing it It is.

In the metal-graphene oxide composite of the present invention, a solution containing a metal salt or a metal ion is added to a graphene oxide dispersion solution in which graphene oxide is dispersed, and alcohol (except tertiary alcohol), N , N-dimethylformamide, tetrahydrofuran, 1,4-dioxane is added as a reducing agent, and the metal that is a metal salt or metal ion is supported on graphene oxide by the reducing action of the reducing agent It is what is letting.

Further, in the metal-graphene oxide composite of the present invention, after irradiating the graphite, which is a carbon sheet laminate composed of carbon atoms arranged in a hexagonal lattice, as a graphene oxide dispersion solution, Using a dispersion solution of graphene oxide prepared by peeling off to one or more carbon sheets by adding sulfuric acid, sodium nitrate and potassium permanganate to graphite irradiated with waves and oxidizing It has characteristics and is also characterized by being used as a catalyst.

According to the present invention, by using an alcohol or the like having a weak reducing action as a reducing agent, it is possible to support graphene oxide while suppressing the reduction of graphene oxide itself, without generating aggregated graphene. Metal-graphene oxide composites can be produced.

In the metal-graphene oxide composite produced in this way, when the supported metal has catalytic activity such as platinum, it can be used as a highly dispersible catalyst, and in particular, an inexpensive catalyst can be provided. be able to. In addition, the metal-graphene oxide complex used as the catalyst can be easily separated and recovered by filtration of graphene oxide and the like and can be easily reused.

In addition, when graphene oxide is used as a metal scavenger by utilizing the support of metal, the specific surface area of graphene oxide is extremely large, so that the capture efficiency is high, and the metal is captured and metal-graphene oxide is captured. By forming the composite, it is easy to separate and recover the metal-graphene oxide composite by a filtration process or the like, so that the metal recovery rate can be improved. Furthermore, since the carbon component can be removed by heat treatment of the recovered metal-graphene oxide composite, the metal captured by the graphene oxide can be easily recovered.

4 is an electron micrograph of a metal-graphene oxide composite according to Example 4.

In the present invention, by using a reducing agent having a relatively weak reducing action instead of a reducing agent having a strong reducing action such as hydrazine as the reducing agent, while supporting the metal ions in the solution on the graphene oxide, The metal is supported while maintaining the dispersibility of graphene oxide by suppressing the reduction reaction more than necessary from occurring on the surface.

It was found that alcohols (excluding tertiary alcohols), N, N-dimethylformamide (DMF), tetrahydrofuran (THF), and 1,4-dioxane are suitable as reducing agents that meet this purpose. In addition, since tertiary alcohol does not have a hydrogen atom on the carbon to which the hydroxyl group is bonded, it is not suitable for use as a reducing agent.

Further, the graphene oxide dispersion solution in which graphene oxide is dispersed is not prepared from graphite by a known Hummers method or the like, but after graphite is pretreated by irradiating microwaves, In addition, sulfuric acid, sodium nitrate, and potassium permanganate are added to oxidize, thereby greatly reducing the manufacturing cost of the graphene oxide dispersion solution itself.

The metal-graphene oxide composite in which a metal having catalytic activity is supported on the graphene oxide of the graphene oxide dispersion solution thus produced can be used as a highly dispersible catalyst and can be manufactured at a lower cost. Therefore, an inexpensive catalyst can be provided.

In addition, the catalyst composed of the metal-graphene oxide complex can be reduced in cost because the metal-graphene oxide complex can be easily separated and recovered by filtration or the like and can be reused.

Also, it can be used for metal removal as a metal scavenger by utilizing the fact that graphene oxide carries a metal.

As such a metal removal method, a dissolved palladium removal method described in Japanese Patent Application Laid-Open No. 2011-41919 is known. This method for removing dissolved palladium provides a method for efficiently removing dissolved palladium from a solution after an organometallic reaction using a palladium catalyst. Specifically, by bringing the solution after the organometallic reaction using a palladium catalyst into contact with an adsorbent composed of an amide-containing cyclic sulfide compound or an adsorbent obtained by immobilizing an amide-containing cyclic sulfide compound on a carrier, the palladium concentration is adjusted. It is reduced to 15ppm.

Alternatively, Japanese Patent Publication No. 2008-535645 proposes a metal scavenger prepared by functionalizing a silicate material such as silica or SBA-15 with a thiol or amine, or other functionalizing agent in a sol-gel method. ing. In this case, when capturing palladium, it has been proposed to use thiol as a functionalizing agent for capturing.

Alternatively, Japanese Patent Application Laid-Open No. 06-227813 proposes a noble metal scavenger in which a chitosan molecule having a crosslinked structure is bound to a pyridine ring or thiophene ring having a chelate-forming ability. This chitosan molecule is obtained from chitin, which is a waste product from the fishery processing industry, and is described to exhibit high adsorptivity to noble metal ions such as gold, platinum, and palladium.

With such known metal scavengers or precious metal scavengers, it is possible to recover the target metal, but it is difficult to separate and recover only the target metal after recovery, and only the target metal is separated. The collection required an even greater processing cost.

However, in the metal scavenger using graphene oxide supporting metal as in the present invention, the carbon component of graphene oxide can be removed by heat treatment, so that the metal supported on graphene oxide can be easily recovered. You can also.

In addition, graphene oxide is prepared by adding sulfuric acid, sodium nitrate, and potassium permanganate to graphite that has been subjected to microwave pretreatment and then oxidizing the graphite. It can be supplied at a relatively low cost and has sufficient utility in terms of cost.

<Preparation of graphene oxide dispersion>
First, the method for preparing the graphene oxide dispersion solution used in each example described later will be described in detail. Graphene oxide is formed by peeling a carbon sheet from graphite, which is a laminate of carbon sheets composed of carbon atoms arranged in a hexagonal lattice.

The raw material graphite is desirably powdered by appropriate pulverization treatment or the like, and by making the powder as fine as possible, it is possible to easily cause peeling of the carbon sheet in the main treatment described later. This time, graphite powder sold by Wako Pure Chemical Industries, Ltd. was used. This graphite powder had an average particle size of about 45 μm.

As a pretreatment, the graphite was subjected to microwave irradiation treatment. Specifically, microwave irradiation treatment was performed using a 230 W microwave oven.

That is, graphite was put in a mortar and lightly stirred, and the mortar was put in a microwave oven in a state where there was no graphite that was agglomerated with the graphite.

When the microwave oven was turned on, sparks started to fly in the microwave oven within a few seconds. The microwave oven was forcibly stopped when the sparks began to fly.

This microwave oven switch was turned on and off (forced stop) three times, and the irradiation was performed for a total of about 10 seconds. The microwave irradiation time may be up to about 1 minute in total, and it is desirable to repeat the microwave irradiation processing a plurality of times as necessary, but depending on the irradiation time, it may be only once. In particular, when the particle size of graphite is large, it is better to lengthen the microwave irradiation time. Conversely, when the particle size of graphite is small, the microwave irradiation time may be short. In addition, when irradiating microwaves, it is desirable to use an inert atmosphere. For example, the microwave oven may be filled with nitrogen gas and the microwave oven switch may be turned on and off.

The graphite that has been subjected to the microwave irradiation treatment is referred to as “pretreated graphite” for convenience of explanation.

Next, the main treatment for producing a graphene oxide dispersion solution by causing the carbon sheet to peel from the pretreated graphite was performed according to the following procedure.

(Process 1)
3.6 g of pretreated graphite was put in a beaker, and 92 mL of sulfuric acid was further added and cooled to 4 ° C. to prepare the primary treatment liquid.

(Process 2)
4 g of sodium nitrate (NaNO ₃ ) was added little by little to this treatment primary solution to prepare this treatment secondary solution.

(Process 3)
12 g of potassium permanganate (KMnO ₄ ) was added to the treated secondary solution and stirred for 10 minutes to prepare the treated tertiary solution.

(Process 4)
The temperature of the treated tertiary solution is 35 ° C., and the mixture is stirred for 2 hours while maintaining the temperature. Then, the beaker is cooled with water, and a predetermined amount of 184 mL of water is added dropwise while stirring the treated tertiary solution. Thus, this treatment quaternary liquid was prepared.

(Process 5)
The treated quaternary liquid was stirred for 30 minutes, 100 mL of water was added, and 20 mL of hydrogen peroxide (H ₂ O ₂ ) was further added little by little to prepare the treated quaternary liquid.

(Process 6)
The treated quinary solution was stirred at 90 ° C. for 30 minutes, and centrifuged while diluting by adding 300 mL of water. Centrifugation was repeated until the supernatant became neutral, and it was completed when the supernatant became neutral.

In this way, the carbon sheet constituting the graphite was oxidized using sulfuric acid, sodium nitrate, and potassium permanganate to cause peeling of the carbon sheet, thereby preparing a graphene oxide dispersion solution.

When the carbon sheet is peeled from the graphite while being oxidized, the carbon sheet may be peeled off by only one layer, or it may be peeled off while a plurality of carbon sheets are laminated. In the present invention, the state in which the carbon sheets of the layers are laminated is not `` graphene '' in the strict sense, but in the present invention, for convenience, it is called graphene including those in the state in which a plurality of carbon sheets are laminated. To do.

Hereinafter, examples using the graphene oxide dispersion prepared by the above-described method will be described. The graphene oxide dispersion used was adjusted so that the graphene oxide had a concentration of 10 mg / mL.

<Preparation of catalyst dispersion by supporting palladium on graphene oxide>
A dispersion of a catalyst in which palladium was supported on graphene oxide to form a palladium-graphene oxide composite was prepared by the following method.

First, as a first step, 5 mg of palladium acetate was added to 3 mL of graphene oxide dispersion to prepare a mixed solution.

Next, as the second step, 20 mL of ethanol and 20 mL of distilled water are added to the mixed solution of the first step, and the mixture is sufficiently dispersed by irradiating with ultrasonic waves for about 2 minutes, and then at 60 ° C. for about 1 hour. Then, the mixture was heated and stirred to prepare a dispersion of a palladium-graphene oxide composite in which palladium particles were supported on graphene oxide. Here, the palladium-graphene oxide complex is a catalyst.

In this example, ethanol was used as the reducing agent, but DMF, THF, 1,4-dioxane, propanol, butanol, hexanol, or the like may be used. Although the heating temperature is 60 ° C., it may be 25 to 150 ° C., preferably 25 to 80 ° C. The heating time may be 0.1 to 24 hours, preferably 0.2 to 5 hours. The heating time can be shortened by increasing the time.

The palladium-graphene oxide complex dispersion prepared as described above with ethanol: distilled water = 1: 1 is referred to as a Pd / GO dispersion for convenience.

<Confirmation of catalyst function (1-1): Suzuki-Miyaura reaction>
Under a 1 atm argon atmosphere, add 1 mL of Pd / GO dispersion, 0.22 mmol of phenylboronic acid (1) and 0.2 mmol of bromobenzene (2) to the test tube, seal, and seal at 40 ° C. for 3 hours. After stirring with heating, the reaction mixture was analyzed by gas chromatography to determine the yield of biphenyl (3). The reaction formula is shown below.

The concentration of the catalyst in the Pd / GO dispersion was 0.005 mol%, and the yield of biphenyl (3) was 99% or more. A comparative test was conducted with an existing palladium-carbon catalyst. In this case, the reaction hardly proceeded, and the yield of biphenyl (3) was 5% or less when the concentration of the catalyst was 0.005 mol%. In particular, it was confirmed that the palladium-graphene oxide composite catalyst can obtain the target product with an absorptivity even when the catalyst amount of the palladium-carbon catalyst is 1/10.

<Confirmation of catalyst function (1-2): Hydrogenation reaction>
Under a hydrogen atmosphere of 1 atm with a balloon, 1 mL of Pd / GO dispersion and 0.20 mmol of chalcone (4) were added to a test tube and stirred at room temperature for 10 hours, and then the reaction mixture was subjected to gas chromatography analysis. The yield of 1,3-diphenylpropan-1-one (5) was determined. The reaction formula is shown below.

The concentration of the catalyst in the Pd / GO dispersion was 0.005 mol%, and the yield of 1,3-diphenylpropan-1-one (5) was 95% or more.

<Confirmation of catalyst function (1-3): Confirmation of catalyst rotation speed>
Under a 1 atm argon atmosphere, add 1 mL of Pd / GO dispersion, 1.65 mmol of phenylboronic acid (1) and 1.5 mmol of 4-acetyliodobenzene (6) to a test tube, seal, and 135 ° C. Then, the reaction mixture was analyzed by gas chromatography to determine the yield of biphenyl (7). The reaction formula is shown below.

The concentration of the catalyst in the Pd / GO dispersion was 0.005 mol%, and the yield of biphenyl (7) was 44%.

When the catalyst rotation speed per palladium atom was calculated, TOF (Turn Over Frequency, 回転 Catalyst rotation rate per hour) and TON (Turn Over Number, total catalyst rotation number) were 237,000, which is a very high value. It was confirmed to be a catalyst.

<Functional confirmation of catalyst (1-4): Heck reaction>
Under a 1 atm argon atmosphere, add 1 mL of Pd / GO dispersion, 0.25 mmol hexadecyltrimethylammonium bromide, 0.75 mmol iodobenzene (8), and 0.5 mmol styrene (9) to a test tube. After sealing and heating and stirring at 100 ° C. for 24 hours, the reaction mixture was analyzed by gas chromatography to determine the yield of stilbene (10). The reaction formula is shown below.

The concentration of the catalyst in the Pd / GO dispersion was 0.005 mol%, and the yield of stilbene (10) was 93%. It seems that hexadecyltrimethylammonium bromide acts as a surfactant and suppresses aggregation of the graphene layer.

<Preparation of dispersion of catalyst in which platinum is supported on graphene oxide>
A catalyst dispersion liquid in which platinum was supported on graphene oxide to form a platinum-graphene oxide composite was prepared by the following method.

First, as a first step, 50 mg of platinum chloride was added to 3 mL of graphene oxide dispersion solution to prepare a mixed solution.

Next, as the second step, 20 mL of ethanol and 20 mL of distilled water are added to the mixed solution of the first step, and the mixture is sufficiently dispersed by irradiation with ultrasonic waves for about 2 minutes, and then at 80 ° C. for about 15 hours. Then, the mixture was heated and stirred to prepare a primary dispersion in which platinum nanoparticles were supported on graphene oxide.

Centrifugation of 1.5 mL of this primary dispersion at 5,000 rpm for 5 minutes, decant the supernatant, add water and centrifuge twice, then add t-BuOH and centrifuge Then, 1.5 mL of t-BuOH was added to the remaining solid to prepare a secondary dispersion. This secondary dispersion is a catalyst dispersion, and a platinum-graphene oxide complex is a catalyst.

In this example, ethanol was used as the reducing agent, but DMF, THF, 1,4-dioxane, propanol, butanol, hexanol, or the like may be used. The heating temperature is 80 ° C., but it may be 25 to 150 ° C., preferably 25 to 100 ° C. The heating time may be 0.5 to 48 hours, preferably 1 to 20 hours. The heating time can be shortened by increasing the time.

The platinum-graphene oxide composite dispersion prepared as described above with ethanol: distilled water = 1: 1 is referred to as a Pt / GO dispersion for convenience.

<Catalyst function check (2-1)>
In air, 1 mL of Pt / GO dispersion and 0.20 mmol of benzyl alcohol (11) were added to a test tube in the air, and the mixture was stirred for 12 hours at room temperature. After that, the reaction mixture was analyzed by gas chromatography, and benzaldehyde was analyzed. The yield of (12) was determined, and the reaction formula is shown below.

The concentration of the catalyst in the catalyst dispersion was 5 mol%, and the yield of benzaldehyde (12) was 91%.

<Confirmation of catalyst function (2-2)>
In air, 1 mL of the above catalyst dispersion, 0.50 mmol of triethylsilane (13), and 5 mmol of water were added to a test tube, and after irradiation with ultrasonic waves for 3 hours, the reaction mixture was analyzed by gas chromatography. The yield of triethylsilanol (14) was determined. The reaction formula is shown below.

The catalyst concentration in the catalyst dispersion was 0.2 mol%, and the yield of triethylsilanol (14) was 90%. A comparative test was conducted using an existing platinum-carbon catalyst. The yield of triethylsilanol (14) was 55% when the concentration of the catalyst was 0.2 mol%, which is a more efficient catalyst than the existing platinum-carbon catalyst. It was confirmed that there was.

<Size control of platinum nanoparticles on platinum-graphene oxide composite>
It has been found that the size of platinum as nano-sized particles can be controlled in the above-described dispersion of platinum-graphene oxide composite.

First, as a first step, 1 mg of platinum chloride was added to 1 mL of graphene oxide dispersion to prepare a mixed solution.

Next, as the second step, 20 mL of ethanol and 20 mL of distilled water are added to the mixed solution of the first step, and after stirring for 5 minutes at room temperature and sufficiently dispersed, 0.6 mL of triethylsilane is added dropwise. Was stirred for 1 hour to prepare a primary dispersion in which platinum nanoparticles were supported on graphene oxide.

Centrifugation of 1.5 mL of this primary dispersion at 5,000 rpm for 5 minutes, decant the supernatant, add water and centrifuge twice, then add 1,4-dioxane and centrifuge Separation was performed, and 1.5 mL of 1,4-dioxane was added to the remaining solid to prepare a secondary dispersion. This secondary dispersion is a catalyst dispersion, and a platinum-graphene oxide complex is a catalyst.

In this example, ethanol was used as the reducing agent, but DMF, THF, 1,4-dioxane, propanol, butanol, hexanol, or the like may be used.

Further, in the above-described embodiment, the loading of the metal on the graphene oxide is promoted by the heat treatment, but in this embodiment, the loading of the metal on the graphene oxide at room temperature by using triethylsilane as an auxiliary reducing agent. Urged. Instead of triethylsilane, a compound having a Si—H bond such as polydimethylsiloxane, triphenylsilane, t-butyldimethylsilane, 1,1,3,3-tetramethyldisiloxane may be used. The addition amount of this auxiliary reducing agent is 0.01 to 10 mL, preferably 60 to 600 mL.

In this embodiment, the temperature at the time of loading is room temperature, but it may be 0 to 150 ° C., preferably 10 to 80 ° C. The heating time is 0.5 to 48 hours, preferably 1 to 10 hours. As long as the temperature is high, the processing time can be shorter.

Here, the particle size of platinum supported on graphene oxide can be adjusted by the amount of triethylsilane added as an auxiliary reducing agent. FIG. 1 shows an electron micrograph of a metal-graphene oxide composite. FIG. 1a shows a case where 0.06 mL of triethylsilane is added, and FIG. 1B shows a case where 0.2 mL of triethylsilane is added. FIG. 1c shows a case where 0.4 mL of triethylsilane is added, and FIG. 1d shows a case where 0.6 mL of triethylsilane is added. It can be seen that 1-2 nm particles are produced when 0.06 to 0.2 mL, and 1 nm platinum nanoparticles are produced when 0.2 mL or more.

Further, e in FIG. 1 is a case where 0.6 mL of triethylsilane is added, and when palladium is supported instead of platinum, f in FIG. 1 is a case where 0.6 mL of triethylsilane is added. In the case where iridium is supported instead of platinum, g in FIG. 1 shows the case where 0.6 mL of triethylsilane is added and rhodium is supported instead of platinum. It can be seen that nanoparticles of palladium, iridium, and rhodium can also be formed.

<Catalyst function check (3)>
In air, 1.5 mL of the catalyst dispersion of this example, 0.50 mmol of triethylsilane (13), and 5 mmol of water were added to a test tube and stirred at room temperature for 1 hour, and then the reaction mixture was subjected to gas chromatography. The yield of triethylsilanol (14) was determined by analysis, and the reaction formula is shown below.

The concentration of the catalyst in the catalyst dispersion was 0.03 mol%, and the yield of triethylsilanol (14) was 99% or more. It was confirmed that the catalyst was more efficient than the catalyst of platinum-supported graphene oxide prepared without adding an existing platinum-carbon catalyst or triethylsilane.

<Functional confirmation as a metal scavenger (1)>
Examples of metal scavengers that collect metal by reducing graphene oxide are shown below. In addition, palladium acetate was used as a metal source to be collected.

First, 0.0003 mmol of palladium acetate and 1 mL of water are added to the test tube, and 0.3 mmol of bromobenzene and 0.3 mmol of phenylboronic acid are added to sufficiently dissolve the palladium acetate. 30 mg of graphene oxide and 1 mL of Ethanol was added and stirred at room temperature for 2 hours to create a reaction mixture. Note that the graphene oxide used here is graphene oxide obtained from the graphene oxide dispersion prepared by the method of Example 1.

Separate the solvent from the reaction mixture using an evaporator, add 1 mol / L nitric acid to the separated solvent, filter through a membrane filter to make the reaction solution, and adjust the palladium concentration in this reaction solution with ICP-MS. It was measured.

As a result, palladium eluted in the reaction solution was 1.2% of the added palladium. In other words, 98.8% of palladium was captured by graphene oxide.

<Functional confirmation as a metal scavenger (2)>
Examples of metal scavengers that collect metal by reducing graphene oxide are shown below. In addition, palladium acetate was used as a metal source to be collected.

First, 0.003 mmol of palladium acetate and 1 mL of water are added to a test tube, 0.3 mmol of chalcone is added to fully dissolve the palladium acetate, 30 mg of graphene oxide and 1 mL of ethanol are added, and the mixture is added at room temperature. Stir for hours to make a reaction mixture. Note that the graphene oxide used here is graphene oxide obtained from the graphene oxide dispersion prepared by the method of Example 1.

As a result, palladium eluted in the reaction solution was 0.2% of the added palladium. In other words, 99.8% of palladium was captured by graphene oxide.

Utilizing the fact that graphene oxide reduced with a reducing agent carries metal, it can be used as a metal scavenger by setting a graphene oxide dispersion solution and a reducing agent such as alcohol, or consists of graphene oxide carrying a catalyst metal A metal-graphene oxide composite can be used as a catalyst.

Claims

A first step of preparing a mixed solution by adding a solution containing a metal salt or metal ion to a graphene oxide dispersion solution in which graphene oxide is dispersed;
At least one of alcohol (excluding tertiary alcohol), N, N-dimethylformamide, tetrahydrofuran, and 1,4-dioxane is added to the mixed solution and stirred to add a metal salt to the graphene oxide in the graphene oxide dispersion solution. The method of carrying | supporting a metal on the graphene oxide which consists of the 2nd process of carrying | supporting the metal or metal which becomes metal ion.
The graphene oxide dispersion solution of the first step is
Irradiating the graphite, which is a laminate of carbon sheets composed of carbon atoms arranged in a hexagonal lattice, with microwaves;
By adding sulfuric acid, sodium nitrate, and potassium permanganate to graphite irradiated with microwaves and oxidizing the graphite, the graphene oxide composed of one or more carbon sheets is separated from the graphite. The method to carry | support a metal on the graphene oxide of Claim 1 currently produced.
A solution containing a metal salt or metal ion is added to a graphene oxide dispersion solution in which graphene oxide is dispersed, and alcohol (except tertiary alcohol), N, N-dimethylformamide, tetrahydrofuran, 1,4 -Metal-graphene oxide composite comprising at least one of dioxane added as a reducing agent, and the graphene oxide supported on the metal salt or a metal ion by the reducing action of the reducing agent body.
The graphene oxide dispersion solution is
Graphite, which is a laminate of carbon sheets composed of hexagonal lattices of carbon atoms, is irradiated with microwaves, and then the graphite irradiated with microwaves is mixed with sulfuric acid, sodium nitrate, and potassium permanganate. 4. The metal-graphene oxide composite according to claim 3, wherein the metal-graphene oxide composite is a dispersed solution of graphene oxide prepared by peeling off into one or more carbon sheets by oxidation.
A catalyst comprising the metal-graphene oxide composite according to claim 3 or 4.