Metal-loaded roll paper type graphene oxide as well as preparation method and application thereof

Abstract

The invention provides metal-loaded roll paper type graphene oxide as well as a preparation method and application thereof. The metal-loaded roll paper type graphene oxide has a hollow cylindrical roll paper type structure formed by curling a single-layer graphene oxide sheet; precious metal is loaded on the roll paper type graphene oxide; wherein the specific surface area of the metal-loaded roll paper type graphene oxide is more than 500m < 2 > / g. According to the preparation method, the winding drum type graphene / Pt-based catalyst with uniformly distributed platinum particles and controllable particle size is prepared by utilizing the characteristics of the graphene oxide, so that the winding drum type graphene / Pt-based catalyst not only has high electrochemical active area and mass ratio activity, but also reduces the loss of platinum and the platinum load per unit area due to the protection effect of the bent graphene; the service life of the catalyst is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of proton exchange membrane fuel cells, and in particular to a metal-loaded rolled paper-type graphene oxide and a preparation method and application thereof. Background Art

[0002] As a highly efficient energy conversion device, the proton exchange membrane fuel cell (PEMFC) can directly convert the chemical energy in hydrogen and oxygen into electrical energy through electrochemical reactions, and only produces water as a product. As an important component of the fuel cell, the fuel cell membrane electrode assembly (MEA) consists of a cathode, an anode catalyst layer, a proton exchange membrane, a cathode, and an anode gas diffusion layer.

[0003] The catalyst layer is a key component of the membrane electrode as the place where the electrochemical reaction occurs. Hydrogen and oxygen diffuse to the catalyst surface and generate water at the same time. The catalysts commonly used in PEMFC are mainly platinum-based catalysts, such as platinum carbon or platinum alloy carbon. Platinum catalysts provide good hydrogen electrochemical activity and good durability in strong acid media. The high cost of platinum makes people want to minimize its use in fuel cells and reduce the platinum loading per unit area.

[0004] Platinum-carbon catalysts for hydrogen fuel cells require platinum nanoparticles with a particle size of 2 to 5 nm, a narrow particle size distribution, uniform distribution on the carbon carrier, and no harmful substances (such as Cl elements). However, due to the very large surface energy of 2 to 5 nm platinum nanoparticles, they are easy to agglomerate. Therefore, it is very difficult to prepare platinum carbon catalysts with a particle size of 2 to 5 nm and a narrow particle size distribution, which are evenly dispersed on the carbon carrier. This is also the reason why they are currently mainly dependent on imports. In traditional platinum-carbon catalysts, nano-platinum particles are directly loaded on the surface of the carbon carrier or in the pores inside. Due to the weak binding force between the carbon carrier and the platinum particles, it is easy to cause the platinum particles to fall off during use.

[0005] CN115986151A discloses a modified graphene nanoscroll and its preparation method and application. The preparation method of the modified graphene nanoscroll comprises the following steps: a mixed solution containing a reducing organic solvent, a noble metal source and a graphite-like carbon material is sequentially subjected to liquid nitrogen cooling and microwave treatment to obtain a graphene nanoscroll loaded with noble metal nanoparticles; wherein the graphite-like carbon material is selected from one or more of graphite oxide and doped graphite oxide. The above preparation method can effectively prevent the graphene carrier from forming an agglomerated structure and enhance the catalytic activity of the catalyst. It obtains a graphene nanoscroll loaded with noble metal nanoparticles by liquid nitrogen cooling and microwave treatment. However, this graphene nanoscroll is not a single-layer structure, and can only form a slightly curled structure, and its flexibility and other properties are not enough to make it curl into a multi-layer paper roll structure, or it will break when it curls into a cylindrical layer; in addition, the maximum specific surface area of ​​the graphene nanoscroll prepared by this method is only 400m in Example 1. 2 / g, other embodiments are all at 400m 2 / g or less, while the platinum loading is between 10 and 70 wt%. It is obvious that the nanoscrolls prepared by this method have a low specific surface area and a high platinum loading, which does not meet the desired purpose of minimizing the use of platinum in fuel cells and reducing the platinum loading per unit area.

[0006] CN113877614A discloses a method for preparing a modified graphene roll, comprising the following steps: mixing MXene material, graphene and water to obtain a MXene-graphene mixed solution, the ratio of the sum of the mass of the MXene material and graphene to the volume of water is (0.1mg~1mg): 1mL; the MXene-graphene mixed solution is heated, liquid nitrogen cooled and freeze-dried in sequence to obtain a MXene-graphene roll; metal particles are loaded on the surface of the MXene-graphene roll. The method uses MXene composite graphene to improve the conductivity of the material, and its flexibility and other properties are not enough to make it curled into a multi-layer paper roll structure, or it will break when it is curled into a cylindrical layer; in addition, this method is similar to the preparation method of the previous graphene roll, using heat, liquid nitrogen cooling and freeze drying, the specific surface area of ​​the graphene material is low, the platinum loading is high, and platinum is easily lost.

[0007] Therefore, it is urgent to develop graphene catalysts that have high electrochemical active area and mass specific activity, reduce the loss of platinum due to the protective effect of curved graphene, and reduce the platinum loading per unit area.

[0008] In view of this, the present invention is proposed. Summary of the invention

[0009] One of the purposes of the present invention is to provide a metal-loaded rolled graphene oxide, wherein the metal-loaded rolled graphene oxide has a rolled structure of a hollow cylinder formed by rolling a single-layer graphene oxide sheet; and the rolled graphene oxide is loaded with a precious metal. The method utilizes the characteristics of graphene to prepare a rolled graphene / Pt-based catalyst with uniform distribution of platinum particles and controllable particle size, which has a high electrochemical active area (ECSA, Electrochemical Surface Area) and mass specific activity (MA, mass activity), and due to the protective effect of the curved graphene, reduces the loss of platinum, and can also reduce the platinum loading per unit area, thereby increasing the service life of the catalyst.

[0010] The second object of the present invention is to provide a method for preparing a metal-loaded paper-curled graphene oxide. The preparation method comprises the following steps: preparing graphene oxide by Hummers redox method; separating a single-layer graphene oxide sheet by centrifugation; loading a noble metal on a single-layer graphene oxide sheet by aniline polymerization, and causing the single-layer graphene oxide sheet to curl, thereby obtaining the metal-loaded paper-curled graphene oxide. The preparation method can prepare a single-layer graphene oxide with an ultra-high specific surface area; and there are a large number of hydroxyl groups and carboxyl groups on the surface of graphene oxide, which is easy for platinum particles to grow on the surface of graphene oxide and increase the binding force; finally, aniline is used to adjust the pH value of the solution on the one hand, and on the other hand, its polymerization is used to cause the graphene oxide nanosheet to curl, so that under the protection of the curved graphene, the loss of platinum is reduced, and the platinum loading per unit area can be reduced, thereby increasing the service life of the catalyst.

[0011] The third object of the present invention is to provide an application of the metal-loaded paper-wrapped graphene oxide in the preparation of a catalyst for a fuel cell.

[0012] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0013] In a first aspect, the present invention provides a metal-loaded scroll-type graphene oxide, wherein the metal-loaded scroll-type graphene oxide has a hollow cylindrical scroll-type structure formed by curling a single-layer graphene oxide sheet; and the scroll-type graphene oxide is loaded with a precious metal.

[0014] The specific surface area of ​​the metal-loaded rolled graphene oxide is 500 m 2 / g or more, for example, 500m 2 / g, 520m 2 / g, 540m 2 / g, 560m 2 / g, 580m 2 / g、600m 2 / g, 620m 2 / g, 640m 2 / g, 680m 2 / g、700m 2 / g、800m 2 / g、1000m 2 / g, etc.

[0015] In the present invention, the paper-wrapped graphene oxide is a single-layer graphene oxide with an ultra-high specific surface area, the specific surface area of ​​which is at least 500 m 2 / g or more, and there are a large number of hydroxyl groups and carboxyl groups on the surface of the graphene oxide of the present application, which makes it easy for precious metal particles to grow on the surface of the graphene oxide and increase the binding force; and the hollow cylindrical paper-roll structure formed by curling a single-layer graphene oxide sheet is more conducive to reducing the platinum loading per unit area and can reduce the loss of platinum, thereby further improving the service life of the catalyst.

[0016] Preferably, the number of curled overlapping layers is at least 2 layers, for example, 2 layers, 3 layers, 4 layers, 5 layers, 6 layers, 7 layers, 8 layers, 9 layers, 10 layers, etc., preferably 3 to 5 layers.

[0017] Preferably, the outer diameter of the scroll-shaped graphene oxide is 100-200 nm, for example, it can be 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, etc., and the inner diameter of the scroll-shaped graphene oxide is 50-100 nm, for example, it can be 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, etc.

[0018] Preferably, the length of the scroll-shaped graphene oxide is 2 to 3 μm, for example, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, etc.

[0019] Preferably, the specific surface area of ​​the single-layer graphene oxide sheet before curling is 1100-1300m 2 / g, for example, it can be 1100m 2 / g, 1150m 2 / g、1200m 2 / g, 1250m 2 / g、1300m 2 / g, etc.

[0020] Preferably, the specific surface area of ​​the metal-loaded rolled graphene oxide is 500 to 600 m 2 / g, for example, it can be 500m 2 / g, 510m 2 / g, 520m 2 / g, 530m 2 / g, 540m 2 / g, 550m 2 / g, 560m 2 / g, 570m 2 / g, 580m 2 / g, 590m 2 / g、600m 2 / g, etc.

[0021] Preferably, the noble metal is platinum particles.

[0022] Preferably, the particle size of the platinum particles is 2 to 5 nm, for example, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, etc.

[0023] Preferably, the loading amount of the platinum particles is 20-60wt%, for example, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt% and the like.

[0024] In a second aspect, the present invention provides a method for preparing the metal-loaded rolled paper-type graphene oxide according to the first aspect, the preparation method comprising the following steps:

[0025] Preparation of graphene oxide using Hummers redox method;

[0026] The single-layer graphene oxide sheets were separated by centrifugation;

[0027] The noble metal is loaded on the single-layer graphene oxide sheet by aniline polymerization, and the single-layer graphene oxide sheet is curled to obtain the metal-loaded rolled-paper graphene oxide.

[0028] In the present invention, the preparation method prepares a single-layer graphene oxide sheet with a large specific surface area by the Hummers redox method and centrifugal separation, and a large number of hydroxyl groups and carboxyl groups are present on the surface, which facilitates the growth of precious metal particles on the surface of the graphene oxide and increases the binding force during the polymerization process; and then aniline is added to adjust the pH value of the solution on the one hand, and on the other hand, the polymerization effect of aniline is utilized to cause the graphene oxide nanosheet to curl, thereby reducing the precious metal loading per unit area, and allowing the protective effect of the bent graphene to reduce metal loss, thereby increasing the service life of the catalyst.

[0029] Preferably, the preparation of graphene oxide using the Hummers redox method specifically comprises the following steps:

[0030] After graphite and sodium nitrate are mixed, concentrated sulfuric acid is added and stirred for the first time; potassium permanganate is added and stirred for the second time; the temperature is increased and stirred for the third time; water is added and stirred for the fourth time; hydrogen peroxide is added, and then suction filtration and washing are performed to obtain the graphene oxide.

[0031] Preferably, the graphite is flaky graphite powder.

[0032] Preferably, the mass ratio of the graphite, sodium nitrate, concentrated sulfuric acid, potassium permanganate, water and hydrogen peroxide is 1:(0.4-0.6):(10-15):(2-4):(80-100):(70-90);

[0033] Here, “0.4-0.6” may be, for example, 0.4, 0.45, 0.5, 0.55, 0.6, etc.;

[0034] Here, “10-15” can be, for example, 10, 11, 12, 13, 14, 15, etc.;

[0035] Here, “2-4” can be, for example, 2, 2.5, 3, 3.5, 4, etc.;

[0036] Among them, "80-100" can be, for example, 80, 85, 90, 95, 100, etc.;

[0037] Here, “70-90” can be, for example, 70, 75, 80, 85, 90, etc.

[0038] Preferably, the mass concentration of hydrogen peroxide in the hydrogen peroxide is 25-30%, for example, 25%, 26%, 27%, 28%, 29%, 30%, etc.

[0039] Preferably, the temperature of the first stirring is -5 to 5°C, for example, -5°C, -4°C, -2°C, 0°C, 2°C, 4°C, 5°C, etc., and the time is 20 to 40 min, for example, 20 min, 25 min, 30 min, 35 min, 40 min, etc.

[0040] Preferably, the temperature of the second stirring is below 10°C, for example, 10°C, 8°C, 6°C, 5°C, 4°C, 2°C, 1°C, 0°C, -5°C, etc., and the time is 20 to 40 min, for example, 20 min, 25 min, 30 min, 35 min, 40 min, etc.

[0041] Preferably, the temperature of the third stirring is 30-40°C, for example, 30°C, 32°C, 34°C, 36°C, 38°C, 40°C, etc., and the time is 20-40min, for example, 20min, 25min, 30min, 35min, 40min, etc.

[0042] Preferably, the temperature of the fourth stirring is 95-100°C, for example, 95°C, 96°C, 97°C, 98°C, 100°C, etc., and the time is 10-20min, for example, 10min, 12min, 14min, 16min, 18min, 20min, etc.

[0043] Preferably, the separation of the single-layer graphene oxide sheet by centrifugation specifically comprises the following steps:

[0044] The graphene oxide prepared by the Hummers redox method is mixed with water and oscillated at a constant speed, and then a single-layer graphene oxide sheet is separated by step-by-step centrifugation.

[0045] Preferably, the mass ratio of the graphene oxide to water is 1:(100-200), for example, it can be 1:100, 1:120, 1:140, 1:160, 1:180, 1:200, etc.

[0046] Preferably, the uniform oscillation speed is 100-400r / min, for example, it can be 100r / min, 150r / min, 200r / min, 250r / min, 300r / min, 350r / min, 400r / min, etc., and the time is 13-15 days, for example, it can be 13 days, 13.5 days, 14 days, 14.5 days, 15 days, etc.

[0047] Preferably, the stepwise centrifugation is specifically carried out in the following manner:

[0048] First, centrifuge for 10 to 30 minutes (for example, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, etc.) at a centrifugal speed of 1000 to 2000 r / min (for example, 1000 r / min, 1200 r / min, 1400 r / min, 1600 r / min, 1800 r / min, 2000 r / min, etc.) to separate the unpeeled graphene oxide; then centrifuge for 10 to 30 minutes (for example, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, etc.) at a centrifugal speed of 10000 to 12000 r / min (for example, 10000 r / min, 10500 r / min, 11000 r / min, 11500 r / min, 12000 r / min, etc.), remove the supernatant, collect the precipitate, obtain the single-layer graphene oxide sheet, and disperse it again for standby use.

[0049] Preferably, the method of polymerizing aniline specifically comprises the following steps:

[0050] A solution containing a single-layer graphene oxide sheet, a noble metal salt, aniline and a solvent are mixed, a polymerization reaction is carried out, and then washing and drying are carried out to obtain the metal-loaded rolled paper-type graphene oxide.

[0051] Preferably, the solid content of the solution containing a single-layer graphene oxide sheet is 1 to 10 wt%, for example, it can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, etc.

[0052] Preferably, the noble metal salt is a tetravalent platinum salt, preferably chloroplatinic acid.

[0053] Preferably, the solvent is ethylene glycol.

[0054] Preferably, the mass ratio of the solution containing a single-layer graphene oxide sheet, the noble metal salt, the aniline and the solvent is (10-50):(0.1-0.5):(5-20):(200-300);

[0055] Here, “10-50” may be, for example, 10, 15, 20, 25, 30, 35, 40, 45, 50, etc.;

[0056] Here, “0.1-0.5” can be, for example, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, etc.;

[0057] Here, “5-20” can be, for example, 5, 6, 8, 10, 12, 14, 16, 18, 20, etc.;

[0058] Here, “200-300” can be, for example, 200, 220, 240, 260, 280, 300, etc.

[0059] Preferably, the polymerization reaction temperature is 75-85°C, for example, 75°C, 76°C, 78°C, 80°C, 82°C, 84°C, 85°C, etc., and the time is 18-30h, for example, 18h, 20h, 22h, 24h, 26h, 28h, 30h, etc.

[0060] Preferably, the polymerization reaction is carried out in a high pressure reactor.

[0061] Preferably, the washing uses ethanol and / or ultrapure water.

[0062] Preferably, the drying is performed by freeze drying.

[0063] Preferably, the freeze-drying temperature is -70 to -20°C, for example, -70°C, -60°C, -50°C, -40°C, -30°C, -20°C, etc., and the time is 6 to 24h, for example, 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, etc.

[0064] In a third aspect, the present invention provides a use of the metal-loaded rolled graphene oxide as described in the first aspect in preparing a catalyst for a fuel cell.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] (1) The single-layer graphene oxide sheet and the metal-loaded rolled graphene oxide prepared by the present invention both have a high specific surface area. The specific surface area of ​​the single-layer graphene oxide sheet before rolling is 1100 m 2 / g or more, the specific surface area of ​​metal-loaded paper-type graphene oxide is 500m 2 / g or more;

[0067] (2) There are a large number of hydroxyl groups and carboxyl groups on the surface of the graphene oxide prepared by the present invention, which facilitates the growth of platinum particles on the surface of the graphene oxide and increases the binding force;

[0068] (3) The preparation of the present invention causes the graphene oxide nanosheets to curl, so that the protection of the bent graphene reduces the loss of platinum and reduces the platinum loading per unit area, thereby increasing the service life of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0070] Figure 1 This is a schematic diagram of the structure of the metal-loaded rolled graphene oxide of the present invention.

[0071] Figure 2 This is a scanning electron microscope image of the metal-loaded rolled graphene oxide provided in Example 1 at 20K.

[0072] Figure 3 This is a scanning electron microscope image of the metal-loaded rolled graphene oxide provided in Example 1 at 40K. DETAILED DESCRIPTION

[0073] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear, however, in the case of any potential ambiguity, the definitions provided herein take precedence over any dictionary or external definitions. In this application, unless otherwise stated, the use of "or" means "and / or". In addition, the use of the term "including" and other forms is non-limiting.

[0074] It should be noted that specific details are described in the following description to facilitate a full understanding of the present invention. However, the present invention can be implemented in a variety of other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0075] Figure 1 Schematic diagram of the structure of the metal-loaded paper-wrapped graphene oxide of the present invention, as shown in Figure 1 As shown, the metal-loaded rolled graphene oxide has a rolled-paper structure of a hollow cylinder formed by rolling a single-layer graphene oxide sheet; and the rolled-paper graphene oxide is loaded with a precious metal.

[0076] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0077] The present invention is further described below by way of examples. Unless otherwise specified, the materials in the examples are prepared according to existing methods or directly purchased from the market.

[0078] Example 1

[0079] This embodiment provides a metal-loaded rolled graphene oxide, wherein the metal-loaded rolled graphene oxide is prepared by the following method:

[0080] S1. Preparation of graphene oxide using Hummers redox method

[0081] ① Add 2g of flaky graphite powder and 1g of sodium nitrate into a 250mL three-necked flask;

[0082] ② In an ice-water bath, use magnetic stirring to slowly add 46 mL of concentrated sulfuric acid. The speed of adding concentrated sulfuric acid should ensure that the solution temperature does not exceed 10°C during the whole process. Continue stirring for 30 minutes after the addition.

[0083] ③ Slowly add 6g of potassium permanganate. The speed of adding potassium permanganate should ensure that the solution temperature does not exceed 10°C during the whole process. Continue stirring for 30 minutes after the addition is completed;

[0084] ④Raise the temperature to 35°C, insert a stirring paddle, and perform mechanical stirring for 30 minutes;

[0085] ⑤ Quickly add 92 mL of ultrapure water, the reaction temperature will rise to 98°C, and continue stirring for 15 minutes;

[0086] ⑥ Continue to add 80mL of 3wt% hydrogen peroxide, and the solution turns brown;

[0087] ⑦ Filter while hot, the filtrate is golden yellow, and wash with 80℃ pure water for several times until there is no SO4 in the solution 2- So far (tested with BaCl2).

[0088] S2. Exfoliation of single-layer graphene oxide

[0089] ① Take 5 g of the viscous graphene oxide after filtration and add it into a 1000 mL three-necked flask;

[0090] ②Add 800mL ultrapure water;

[0091] ③ Place on a shaker and shake at 100 r / min for 14 days;

[0092] ④ Separate the desired single-layer graphene oxide by centrifuge step-by-step centrifugation;

[0093] The stepwise centrifugation specifically adopts the following method:

[0094] First, centrifuge at a centrifugal speed of 1000 r / min for 10 minutes to separate; then centrifuge at a centrifugal speed of 10000 r / min for 20 minutes to separate a single layer of graphene oxide.

[0095] S3. Preparation of Curled Pt / Graphene

[0096] ① Take 50g of graphene oxide solution (solid content is 5wt%), 0.1g of chloroplatinic acid, 300mL of ethylene glycol, and 5g of aniline and add them into a 500mL polytetrafluoroethylene-lined stainless steel autoclave;

[0097] ②Raise the temperature to 80℃ and keep the reaction at constant temperature for 24h;

[0098] ③ The precipitate was washed with 100 mL of ethanol and 500 mL of ultrapure water, and freeze-dried at -45°C for 24 h to obtain the metal-loaded scroll-shaped graphene oxide.

[0099] Example 2

[0100] This embodiment provides a metal-loaded rolled graphene oxide, wherein the metal-loaded rolled graphene oxide is prepared by the following method:

[0101] S1. Preparation of graphene oxide using Hummers redox method

[0102] ① Add 2g of flaky graphite powder and 1g of sodium nitrate into a 250mL three-necked flask;

[0103] ② In an ice-water bath, use magnetic stirring to slowly add 46 mL of concentrated sulfuric acid. The speed of adding concentrated sulfuric acid should ensure that the solution temperature does not exceed 10°C during the whole process. Continue stirring for 30 minutes after the addition.

[0104] ③ Slowly add 6g of potassium permanganate. The speed of adding potassium permanganate should ensure that the solution temperature does not exceed 10°C during the whole process. Continue stirring for 30 minutes after the addition is completed;

[0105] ④Raise the temperature to 35°C, insert a stirring paddle, and perform mechanical stirring for 30 minutes;

[0106] ⑤ Quickly add 92 mL of ultrapure water, the reaction temperature will rise to 98°C, and continue stirring for 15 minutes;

[0107] ⑥ Continue to add 80mL of 3wt% hydrogen peroxide, and the solution turns brown;

[0108] ⑦ Filter while hot, the filtrate is golden yellow, and wash with 80℃ pure water for several times until there is no SO4 in the solution 2- So far (tested with BaCl2).

[0109] S2. Exfoliation of single-layer graphene oxide

[0110] ① Take 5 g of the viscous graphene oxide after filtration and add it into a 1000 mL three-necked flask;

[0111] ②Add 800mL ultrapure water;

[0112] ③ Place on a shaker and shake at 250 r / min for 14 days;

[0113] ④ Separate the desired single-layer graphene oxide by centrifuge step-by-step centrifugation;

[0114] The stepwise centrifugation specifically adopts the following method:

[0115] First, centrifuge at a centrifugal speed of 1500 r / min for 10 minutes to separate; then centrifuge at a centrifugal speed of 11000 r / min for 15 minutes to separate a single layer of graphene oxide.

[0116] S3. Preparation of Curled Pt / Graphene

[0117] ① Take 30g of graphene oxide solution (solid content is 3wt%), 0.2g of chloroplatinic acid, 300mL of ethylene glycol, and 15g of aniline and add them into a 500mL polytetrafluoroethylene-lined stainless steel autoclave;

[0118] ②Raise the temperature to 80℃ and keep the reaction at constant temperature for 24h;

[0119] ③ The precipitate was washed with 300 mL of ethanol and 400 mL of ultrapure water, and freeze-dried at -65°C for 18 h to obtain the metal-loaded scroll-shaped graphene oxide.

[0120] Example 3

[0121] This embodiment provides a metal-loaded rolled graphene oxide, wherein the metal-loaded rolled graphene oxide is prepared by the following method:

[0122] S1. Preparation of graphene oxide using Hummers redox method

[0123] ① Add 2g of flaky graphite powder and 1g of sodium nitrate into a 250mL three-necked flask;

[0124] ② In an ice-water bath, use magnetic stirring to slowly add 46 mL of concentrated sulfuric acid. The speed of adding concentrated sulfuric acid should ensure that the solution temperature does not exceed 10°C during the whole process. Continue stirring for 30 minutes after the addition.

[0125] ③ Slowly add 6g of potassium permanganate. The speed of adding potassium permanganate should ensure that the solution temperature does not exceed 10°C during the whole process. Continue stirring for 30 minutes after the addition is completed;

[0126] ④Raise the temperature to 35°C, insert a stirring paddle, and perform mechanical stirring for 30 minutes;

[0127] ⑤ Quickly add 92 mL of ultrapure water, the reaction temperature will rise to 98°C, and continue stirring for 15 minutes;

[0128] ⑥ Continue to add 80mL of 3wt% hydrogen peroxide, and the solution turns brown;

[0129] ⑦ Filter while hot, the filtrate is golden yellow, and wash with 80℃ pure water for several times until there is no SO4 in the solution 2- So far (tested with BaCl2).

[0130] S2. Exfoliation of single-layer graphene oxide

[0131] ① Take 5 g of the viscous graphene oxide after filtration and add it into a 1000 mL three-necked flask;

[0132] ②Add 800mL ultrapure water;

[0133] ③ Place on a shaker and shake at 300 r / min for 14 days;

[0134] ④ Separate the desired single-layer graphene oxide by centrifuge step-by-step centrifugation;

[0135] The stepwise centrifugation specifically adopts the following method:

[0136] First, centrifuge at a centrifugal speed of 2000 r / min for 30 minutes to separate; then centrifuge at a centrifugal speed of 12000 r / min for 30 minutes to separate a single layer of graphene oxide.

[0137] S3. Preparation of Curled Pt / Graphene

[0138] ① Take 30g of graphene oxide solution (solid content is 2wt%), 0.1g of chloroplatinic acid, 300mL of ethylene glycol, and 10g of aniline and add them into a 500mL polytetrafluoroethylene-lined stainless steel autoclave;

[0139] ②Raise the temperature to 80℃ and keep the reaction at constant temperature for 24h;

[0140] ③ The precipitate was washed with 300 mL of ethanol and 400 mL of ultrapure water, and freeze-dried at -75°C for 12 h to obtain the metal-loaded scroll-shaped graphene oxide.

[0141] Example 4

[0142] This embodiment provides a metal-loaded rolled-paper graphene oxide, which is different from Embodiment 1 only in that the exfoliation method of the single-layer graphene oxide is different from that of Embodiment 1, and no longer adopts the step-by-step centrifugation method, but adopts the ultrasonic oscillation method: the ultrasonic power is 200W for 5 minutes to separate the single-layer graphene oxide sheet.

[0143] Example 5

[0144] This embodiment provides a metal-loaded rolled paper-type graphene oxide, which is different from Example 1 only in that the reaction temperature and time for the preparation of the rolled Pt / graphene are different, specifically 70° C. and the reaction time is 36 hours.

[0145] Example 6

[0146] This embodiment provides a metal-loaded rolled paper-type graphene oxide, which is different from Example 1 only in that the reaction temperature and time for preparing the rolled Pt / graphene are different, specifically 90° C. and the reaction time is 18 hours.

[0147] Comparative Example 1

[0148] This comparative example provides a graphene nanoscroll, which is prepared by the following method:

[0149] (1) preparing a reaction solution: dispersing 20 mg of chloroplatinic acid and 100 mg of graphite oxide in 100 mL of ethylene glycol solution to prepare an ethylene glycol solution of chloroplatinic acid and graphite oxide;

[0150] (2) Liquid nitrogen cooling: pour the ethylene glycol solution of chloroplatinic acid and graphite oxide prepared in step (1) into 100 mL of liquid nitrogen and cool for 2 seconds to obtain a chloroplatinic acid-graphite oxide-ethylene glycol-liquid nitrogen solid-liquid mixed component;

[0151] (3) Microwave treatment: The chloroplatinic acid-graphite oxide-ethylene glycol-liquid nitrogen solid-liquid mixed component prepared in step (2) is placed in a microwave reactor and treated at 5 kW microwave for 2 min to obtain a graphene nanoscroll-Pt nanoparticle precursor. The graphene nanoscroll-Pt nanoparticle precursor is then filtered and washed 5 times, and freeze-dried at -70°C for 1 h to obtain a modified graphene nanoscroll.

[0152] Comparative Example 2

[0153] This comparative example provides a graphene oxide, which is prepared by the following method:

[0154] S1. Preparation of graphene oxide using Hummers redox method

[0155] ① Add 2g of flaky graphite powder and 1g of sodium nitrate into a 250mL three-necked flask;

[0156] ② In an ice-water bath, use magnetic stirring to slowly add 46 mL of concentrated sulfuric acid. The speed of adding concentrated sulfuric acid should ensure that the solution temperature does not exceed 10°C during the whole process. Continue stirring for 30 minutes after the addition.

[0157] ③ Slowly add 6g of potassium permanganate. The speed of adding potassium permanganate should ensure that the solution temperature does not exceed 10°C during the whole process. Continue stirring for 30 minutes after the addition is completed;

[0158] ④Raise the temperature to 35°C, insert a stirring paddle, and perform mechanical stirring for 30 minutes;

[0159] ⑤ Quickly add 92 mL of ultrapure water, the reaction temperature will rise to 98°C, and continue stirring for 15 minutes;

[0160] ⑥ Continue to add 80mL of 3wt% hydrogen peroxide, and the solution turns brown;

[0161] ⑦ Filter while hot, the filtrate is golden yellow, and wash with 80℃ pure water for several times until there is no SO4 in the solution 2-So far (tested with BaCl2).

[0162] S2. Preparation of Curled Pt / Graphene

[0163] ① Take 1g of viscous graphite oxide solution (solid content 40wt%), 0.1g of chloroplatinic acid, 200mL of ethylene glycol, and 10g of aniline and add them into a 500mL polytetrafluoroethylene-lined stainless steel autoclave;

[0164] ②Raise the temperature to 80℃ and keep the reaction at constant temperature for 24h;

[0165] ③ The precipitate was washed with 300 mL of ethanol and 500 mL of ultrapure water, and freeze-dried at -65°C for 18 h to obtain the curled Pt / graphene.

[0166] Comparative Example 3

[0167] This comparative example provides a graphene oxide, which is prepared by the following method:

[0168] S1. Preparation of graphene oxide using Hummers redox method

[0169] ① Add 2g of flaky graphite powder and 1g of sodium nitrate into a 250mL three-necked flask;

[0170] ② In an ice-water bath, use magnetic stirring to slowly add 46 mL of concentrated sulfuric acid. The speed of adding concentrated sulfuric acid should ensure that the solution temperature does not exceed 10°C during the whole process. Continue stirring for 30 minutes after the addition.

[0171] ③ Slowly add 6g of potassium permanganate. The speed of adding potassium permanganate should ensure that the solution temperature does not exceed 10°C during the whole process. Continue stirring for 30 minutes after the addition is completed;

[0172] ④Raise the temperature to 35°C, insert a stirring paddle, and perform mechanical stirring for 30 minutes;

[0173] ⑤ Quickly add 92 mL of ultrapure water, the reaction temperature will rise to 98°C, and continue stirring for 15 minutes;

[0174] ⑥ Continue to add 80mL of 3wt% hydrogen peroxide, and the solution turns brown;

[0175] ⑦ Filter while hot, the filtrate is golden yellow, and wash with 80℃ pure water for several times until there is no SO4 in the solution 2- So far (tested with BaCl2).

[0176] S2. Exfoliation of single-layer graphene oxide

[0177] ① Take 5 g of the viscous graphene oxide after filtration and add it into a 1000 mL three-necked flask;

[0178] ②Add 800mL ultrapure water;

[0179] ③ Place on a shaker and shake at 250 r / min for 14 days;

[0180] ④ Separate the desired single-layer graphene oxide by centrifuge step-by-step centrifugation;

[0181] The stepwise centrifugation specifically adopts the following method:

[0182] First, centrifuge at a centrifugal speed of 1500 r / min for 10 minutes to separate; then centrifuge at a centrifugal speed of 11000 r / min for 15 minutes to separate a single layer of graphene oxide.

[0183] S3. Preparation of Curled Pt / Graphene

[0184] ① Take 30g of graphene oxide solution (solid content is 3wt%), 0.2g of chloroplatinic acid, and 300mL of ethylene glycol and add them into a 500mL polytetrafluoroethylene-lined stainless steel autoclave;

[0185] ②Raise the temperature to 80℃ and keep the reaction at constant temperature for 24h;

[0186] ③ The precipitate was washed with 300 mL of ethanol and 400 mL of ultrapure water, and freeze-dried at -65°C for 12 h to obtain the metal-loaded scroll-shaped graphene oxide.

[0187] Comparative Example 4

[0188] This comparative example provides a graphene oxide, which is prepared by the following method:

[0189] S1. Preparation of graphene oxide using Hummers redox method

[0190] ① Add 2g of flaky graphite powder and 1g of sodium nitrate into a 250mL three-necked flask;

[0191] ② In an ice-water bath, use magnetic stirring to slowly add 46 mL of concentrated sulfuric acid. The speed of adding concentrated sulfuric acid should ensure that the solution temperature does not exceed 10°C during the whole process. Continue stirring for 30 minutes after the addition.

[0192] ③ Slowly add 6g of potassium permanganate. The speed of adding potassium permanganate should ensure that the solution temperature does not exceed 10°C during the whole process. Continue stirring for 30 minutes after the addition is completed;

[0193] ④Raise the temperature to 35°C, insert a stirring paddle, and perform mechanical stirring for 30 minutes;

[0194] ⑤ Quickly add 92 mL of ultrapure water, the reaction temperature will rise to 98°C, and continue stirring for 15 minutes;

[0195] ⑥ Continue to add 80mL of 3wt% hydrogen peroxide, and the solution turns brown;

[0196] ⑦ Filter while hot, the filtrate is golden yellow, and wash with 80℃ pure water for several times until there is no SO4 in the solution 2- So far (tested with BaCl2).

[0197] S2. Exfoliation of single-layer graphene oxide

[0198] ① Take 5 g of the viscous graphene oxide after filtration and add it into a 1000 mL three-necked flask;

[0199] ②Add 800mL ultrapure water;

[0200] ③ Place on a shaker and shake at 250 r / min for 14 days;

[0201] ④ Separate the desired single-layer graphene oxide by centrifuge step-by-step centrifugation;

[0202] The stepwise centrifugation specifically adopts the following method:

[0203] First, centrifuge at a centrifugal speed of 1500 r / min for 10 minutes to separate; then centrifuge at a centrifugal speed of 11000 r / min for 15 minutes to separate a single layer of graphene oxide.

[0204] S3. Preparation of Curled Pt / Graphene

[0205] ① Take 30g of graphene oxide solution (solid content is 3wt%), 0.2g of chloroplatinic acid, 300mL of ethylene glycol, and 5g of phenol into a 500mL polytetrafluoroethylene-lined stainless steel autoclave;

[0206] ②Raise the temperature to 80℃ and keep the reaction at constant temperature for 24h;

[0207] ③ The precipitate was washed with 300 mL of ethanol and 400 mL of ultrapure water, and freeze-dried at -65°C for 24 h to obtain the metal-loaded scroll-shaped graphene oxide.

[0208] Comparative Example 5

[0209] This comparative example provides a graphene oxide, which is prepared by the following method:

[0210] S1. Preparation of graphene oxide using Hummers redox method

[0211] ① Add 2g of flaky graphite powder and 1g of sodium nitrate into a 250mL three-necked flask;

[0212] ② In an ice-water bath, use magnetic stirring to slowly add 46 mL of concentrated sulfuric acid. The speed of adding concentrated sulfuric acid should ensure that the solution temperature does not exceed 10°C during the whole process. Continue stirring for 30 minutes after the addition.

[0213] ③ Slowly add 6g of potassium permanganate. The speed of adding potassium permanganate should ensure that the solution temperature does not exceed 10°C during the whole process. Continue stirring for 30 minutes after the addition is completed;

[0214] ④Raise the temperature to 35°C, insert a stirring paddle, and perform mechanical stirring for 30 minutes;

[0215] ⑤ Quickly add 92 mL of ultrapure water, the reaction temperature will rise to 98°C, and continue stirring for 15 minutes;

[0216] ⑥ Continue to add 80mL of 3wt% hydrogen peroxide, and the solution turns brown;

[0217] ⑦ Filter while hot, the filtrate is golden yellow, and wash with 80℃ pure water for several times until there is no SO4 in the solution 2- So far (tested with BaCl2).

[0218] S2. Exfoliation of single-layer graphene oxide

[0219] ① Take 5 g of the viscous graphene oxide after filtration and add it into a 1000 mL three-necked flask;

[0220] ②Add 800mL ultrapure water;

[0221] ③ Place on a shaker and shake at 250 r / min for 14 days;

[0222] ④ Separate the desired single-layer graphene oxide by centrifuge step-by-step centrifugation;

[0223] The stepwise centrifugation specifically adopts the following method:

[0224] First, centrifuge at a centrifugal speed of 1500 r / min for 10 minutes to separate; then centrifuge at a centrifugal speed of 11000 r / min for 15 minutes to separate a single layer of graphene oxide.

[0225] S3. Preparation of Curled Pt / Graphene

[0226] ① Take 30g of graphene oxide solution (solid content is 3wt%), 0.2g of chloroplatinic acid, 300mL of ethylene glycol, and 5g of triethylamine into a 500mL polytetrafluoroethylene-lined stainless steel autoclave;

[0227] ②Raise the temperature to 80℃ and keep the reaction at constant temperature for 24h;

[0228] ③ The precipitate was washed with 300 mL of ethanol and 400 mL of ultrapure water, and freeze-dried at -65°C for 18 h to obtain the metal-loaded scroll-shaped graphene oxide.

[0229] Test Example 1

[0230] Basic performance test

[0231] Test samples: metal-loaded rolled paper-type graphene oxide provided in Examples 1 to 6, and graphene oxide materials provided in Comparative Examples 1 to 5;

[0232] Test method: Hitachi scanning electron microscope SU8100 UD in secondary electron mode, 50k times 100~200nm, inner diameter 50~100nm.

[0233] The specific test results are shown in Table 1 below:

[0234] Table 1

[0235]

[0236] As shown in Table 1, the platinum loading amount of the metal-loaded paper-type graphene oxide prepared by the present invention is 46-50wt%, the platinum particle size is 2-5nm, and the specific surface area before curling loading is 1100-1300m 2 / g, the specific surface area after curling loading is 500~600m 2 / g, length 2-3μm, outer diameter 100-200nm, inner diameter 50-100nm, and curling number 2-5 layers. This method uses the characteristics of graphene to prepare a rolled graphene / Pt-based catalyst with uniform distribution of platinum particles and controllable particle size. It has high electrochemical active area (ECSA, Electrochemical Surface Area) and mass specific activity (MA, mass activity), and due to the protective effect of the curved graphene, it reduces the loss of platinum, reduces the platinum loading per unit area, and increases the service life of the catalyst.

[0237] From the comparison between Example 1 and Example 4, it can be seen that the single-layer graphene oxide peeled off by the preferred step-by-step centrifugation method of the present application has a higher specific surface area, a better curling effect, and is more conducive to reducing the loss of platinum.

[0238] From the comparison between Example 1 and Examples 5 to 6, it can be seen that the temperature of the S3 polymerization reaction is preferably 75 to 85° C. and the time is in the range of 18 to 30 hours.

[0239] However, the graphene oxide prepared by the methods disclosed in Comparative Examples 1 to 5 has insufficient flexibility and other properties to be curled into a multi-layer paper roll structure, or will break when curled into a single cylindrical structure, and therefore does not have parameters such as length, outer diameter, inner diameter, and number of curling layers.

[0240] Test Example 2

[0241] Electrochemical catalytic performance test

[0242] Test samples: metal-loaded rolled paper-type graphene oxide provided in Examples 1 to 6, and graphene oxide materials provided in Comparative Examples 1 to 5;

[0243] Test method: Take 4 mg of the catalyst prepared in the examples and comparative examples, add 760 μL of deionized water, 20 μL of anhydrous ethanol and 40 μL (5wt%) of Nafion solution, and ultrasonically disperse for 30 minutes to make it ink-like. Then take 20 μL of ink and drop it on the glassy carbon electrode and dry it. The three-electrode system uses 0.1M perchloric acid solution as the electrolyte, the catalyst-loaded electrode as the working electrode, silver / silver chloride as the reference electrode, and the graphite electrode as the counter electrode. Subsequently, use a test instrument (electrochemical workstation) with a scanning range of (-0.1-1) v, a scanning rate of 10 mV / s, and a rotation speed of 1600 r / min to perform LSV curve testing;

[0244] The specific test results are shown in Table 2 below:

[0245] Table 2

[0246]

[0247]

[0248] From the test data in Table 2, it can be seen that the metal-loaded paper-type graphene oxide provided by Examples 1 to 6 of the present invention has a limiting current density of 5.7 to 5.9 mA / cm2 obtained by linear sweep voltammetry. 2 The half-wave potential and half-wave potential are 0.92-0.98 V respectively. After 5000 cycles of cycle stability test, the limiting current density is 5.50-5.80 mA / cm 2 The performance temperature shows that the protective effect of the bent graphene of the present invention can effectively reduce the loss of platinum and increase the service life of the catalyst.

[0249] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A metal-loaded scroll-type graphene oxide, characterized in that: The metal-loaded scroll-shaped graphene oxide has a scroll-shaped structure of a hollow cylinder formed by rolling a single-layer graphene oxide sheet; and the scroll-shaped graphene oxide is loaded with a precious metal; The specific surface area of ​​the metal-loaded rolled graphene oxide is 500 m 2 / g or above.

2. The metal-loaded scroll-shaped graphene oxide according to claim 1, characterized in that: The number of the curled overlapping layers is at least 2 layers, preferably 3 to 5 layers; Preferably, the outer diameter of the scroll-shaped graphene oxide is 100 to 200 nm, and the inner diameter of the scroll-shaped graphene oxide is 50 to 100 nm; Preferably, the length of the rolled graphene oxide is 2 to 3 μm; Preferably, the specific surface area of ​​the single-layer graphene oxide sheet before curling is 1100-1300m 2 / g; Preferably, the specific surface area of ​​the metal-loaded rolled graphene oxide is 500 to 600 m 2 / g.

3. The metal-loaded scroll-shaped graphene oxide according to claim 1 or 2, characterized in that: The precious metal is platinum particles; Preferably, the particle size of the platinum particles is 2 to 5 nm; Preferably, the loading amount of the platinum particles is 20 to 60 wt %.

4. A method for preparing metal-loaded scroll-shaped graphene oxide according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: Preparation of graphene oxide using Hummers redox method; The single-layer graphene oxide sheets were separated by centrifugation; The noble metal is loaded on the single-layer graphene oxide sheet by aniline polymerization, and the single-layer graphene oxide sheet is curled to obtain the metal-loaded rolled-paper graphene oxide.

5. The preparation method according to claim 4, characterized in that: The method for preparing graphene oxide by Hummers redox method specifically comprises the following steps: After mixing graphite and sodium nitrate, adding concentrated sulfuric acid and stirring for the first time; adding potassium permanganate and stirring for the second time; heating and stirring for the third time; adding water and stirring for the fourth time; adding hydrogen peroxide, and then filtering and washing to obtain the graphene oxide; Preferably, the graphite is flaky graphite powder; Preferably, the mass ratio of the graphite, sodium nitrate, concentrated sulfuric acid, potassium permanganate, water and hydrogen peroxide is 1:(0.4-0.6):(10-15):(2-4):(80-100):(70-90); Preferably, the mass concentration of hydrogen peroxide in the hydrogen peroxide is 25-30%; Preferably, the temperature of the first stirring is -5 to 5°C and the time is 20 to 40 minutes; Preferably, the temperature of the second stirring is below 10°C and the time is 20 to 40 minutes; Preferably, the temperature of the third stirring is 30-40°C and the time is 20-40min; Preferably, the temperature of the fourth stirring is 95-100° C., and the time is 10-20 min.

6. The preparation method according to claim 4, characterized in that: The method of separating the single-layer graphene oxide sheet by centrifugation specifically comprises the following steps: The graphene oxide prepared by the Hummers redox method is mixed with water and oscillated at a constant speed, and then a single-layer graphene oxide sheet is separated by step-by-step centrifugation.

7. The preparation method according to claim 6, characterized in that: The mass ratio of graphene oxide to water is 1:(100-200); Preferably, the uniform oscillation speed is 100-400 r / min, and the time is 13-15 days; Preferably, the stepwise centrifugation is specifically carried out in the following manner: First, centrifuge at a centrifugal speed of 1000-2000 r / min for 10-30 minutes to separate the unpeeled graphene oxide; then centrifuge at a centrifugal speed of 10000-12000 r / min for 10-30 minutes to collect the precipitate to obtain the single-layer graphene oxide sheet.

8. The preparation method according to claim 4, characterized in that: The method of aniline polymerization specifically comprises the following steps: A solution containing a single-layer graphene oxide sheet, a noble metal salt, aniline and a solvent are mixed, a polymerization reaction is carried out, and then washing and drying are carried out to obtain the metal-loaded rolled paper-type graphene oxide.

9. The preparation method according to claim 8, characterized in that: The solid content of the solution containing the single-layer graphene oxide sheet is 1 to 10 wt %; Preferably, the noble metal salt is a tetravalent platinum salt, preferably chloroplatinic acid; Preferably, the solvent is ethylene glycol; Preferably, the mass ratio of the solution containing a single-layer graphene oxide sheet, the noble metal salt, the aniline and the solvent is (10-50):(0.1-0.5):(5-20):(200-300); Preferably, the polymerization reaction temperature is 75-85°C and the time is 18-30h; Preferably, the polymerization reaction is carried out in a high pressure reactor; Preferably, the washing is carried out using ethanol and / or ultrapure water; Preferably, the drying is freeze-drying; Preferably, the freeze-drying temperature is -70 to -20°C and the time is 6 to 24 hours.

10. Use of the metal-loaded scroll-shaped graphene oxide according to any one of claims 1 to 3 in preparing a catalyst for a fuel cell.

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