Preparation method of platinum nanoparticles, through-type carbon-based catalyst and preparation method of through-type carbon-based catalyst

Abstract

The invention provides a preparation method of platinum nanoparticles, a penetrating type carbon-based catalyst and a preparation method of the penetrating type carbon-based catalyst. In the preparation of the platinum nanoparticles, high-concentration chloroplatinic acid and ethylene glycol are subjected to heteronuclear crystallization to grow platinum seed crystals; and mixing low-concentration chloroplatinic acid with ethylene glycol for homonuclear growth to obtain platinum particles with uniform distribution and uniform size. In the preparation of the penetrating type carbon-based catalyst, single-layer graphene oxide with a micropore structure is added; the through-type platinum / graphene catalyst is prepared by performing nano mixing with platinum particles and adding hydrazine hydrate for reaction, and platinum grows bidirectionally on a carbon carrier, so that the platinum particles are prevented from being wrapped by the carbon carrier.

Description

Technical Field

[0001] The present application relates to the technical field of proton exchange membrane fuel cells, and more specifically to a method for preparing platinum nanoparticles, a through-type carbon-based catalyst and a method for preparing the same. 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 a fuel cell, the membrane electrode assembly (MEA) of the fuel cell is composed of a cathode, an anode catalyst layer, a proton exchange membrane, a cathode, and an anode gas diffusion layer. The catalyst layer is the place where the electrochemical reaction occurs. Hydrogen and oxygen diffuse to the catalyst surface and generate water at the same time. It is a key component of the membrane electrode. 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. Low platinum loading platinum may lead to insufficient hydrogen adsorption and precipitation in the catalyst layer, which will reduce the efficiency and energy utilization of the hydrogen reaction in the system. In the prior art, platinum ions are usually reduced to metallic platinum form. This is because metallic platinum has better catalytic activity and stability, while platinum ions are relatively poor. If the reduced platinum particles are unevenly distributed, it may cause problems in catalyst activity, loading effect, stability and electronic conduction.

[0003] Therefore, it is necessary to provide a method for preparing platinum nanoparticles, a perforated carbon-based catalyst and a preparation method thereof, so as to at least partially solve the above problems. Summary of the invention

[0004] A series of simplified concepts are introduced in the Summary of the Invention section, which will be further described in detail in the Detailed Description of the Invention section. The Summary of the Invention section of this application does not mean to attempt to define the key features and essential technical features of the claimed technical solution, nor does it mean to attempt to determine the scope of protection of the claimed technical solution.

[0005] In order to at least partially solve the above problems, the present application provides a first aspect of a method for preparing platinum nanoparticles, comprising the following steps:

[0006] S11, mixing high concentration chloroplatinic acid and ethylene glycol, reacting under ultrasonic conditions, and taking a precipitate;

[0007] S12, mixing the precipitate in step S1 with low concentration chloroplatinic acid and ethylene glycol to obtain platinum nanoparticles;

[0008] The mass concentration of the high concentration chloroplatinic acid is 5-10%;

[0009] The mass concentration of the low-concentration chloroplatinic acid is 0.5-2%.

[0010] According to the preparation method of platinum nanoparticles provided in the first aspect of the present application, heteronuclear crystallization is performed in step S11 to grow platinum seed crystals; step S12 is mainly homonuclear growth, and platinum particles grow in stage S11. Through the distributed growth method provided in the present application, the generated platinum particles are evenly distributed and uniform in size.

[0011] Optionally, the reaction in step S11 satisfies at least one of the following conditions:

[0012] (1) The reaction temperature is 70-90°C;

[0013] (2) The reaction is carried out under mechanical stirring conditions;

[0014] (3) The ultrasound duration is 0.5 to 1.5 hours;

[0015] (4) After the reaction, let it stand for 5 to 7 hours;

[0016] (5) The volume ratio of high concentration chloroplatinic acid to ethylene glycol is 100:1.

[0017] Optionally, the reaction in step S12 satisfies at least one of the following conditions:

[0018] (1) The reaction temperature is 30 to 50°C;

[0019] (2) The reaction is carried out under mechanical stirring conditions;

[0020] (3) The reaction time is 22 to 26 hours;

[0021] (4) After the reaction, let it stand for 5-7 hours;

[0022] (5) The volume ratio of low concentration chloroplatinic acid to ethylene glycol is 100:1.

[0023] The second aspect of the present application provides a method for preparing a through-type carbon-based catalyst, comprising the following steps:

[0024] S21, etching the single-layer graphene oxide to obtain a single-layer graphene oxide with a microporous structure;

[0025] S22, mixing the single-layer graphene oxide with a microporous structure in step S21 with the platinum nanoparticles according to any one of claims 1 to 3, adding hydrazine hydrate to react, and preparing a through-type platinum / graphene catalyst.

[0026] According to the preparation method of the through-type carbon-based catalyst provided in the second aspect of the present application, a monolayer graphene oxide with a microporous structure is reacted with nano-platinum particles in hydrazine hydrate, and the growth of platinum on the carbon carrier is bidirectional growth, which avoids the wrapping and shielding of the platinum particles by the carbon carrier. And in the use of fuel cells, the upper and lower surfaces of the platinum particles increase the probability of contact with the ionomer, and can better form a three-phase interface. In this application, the sheet structure of graphene is utilized, which has a higher specific surface area than the general mesoporous carbon carrier. Since the diameter of the platinum particles is greater than the thickness of the monolayer graphene oxide, the platinum can be exposed up and down in the monolayer graphene oxide, and is less blocked by the carbon carrier, so the catalyst under the same platinum loading has a higher electrochemical active area.

[0027] Optionally, the single-layer graphene in step S21 is graphene oxide prepared by step-by-step centrifugation.

[0028] Optionally, the graphene oxide is prepared by Hummers redox method.

[0029] Optionally, the etching process in step S21 is physical etching and / or chemical etching.

[0030] Optionally, the etching in step S21 includes the following steps:

[0031] S211, placing the single-layer graphene oxide in sodium hydroxide, and etching at a temperature of 60 to 90° C. for 1 to 48 hours;

[0032] S212, cleaning the etched single-layer graphene oxide.

[0033] Optionally, the reaction temperature in step S22 is 70-90° C., and the reaction time is 5-7 h.

[0034] The third aspect of the present application provides a through-type carbon-based catalyst prepared according to the above-mentioned preparation method.

[0035] According to the through-type carbon-based catalyst provided in the third aspect of the present application, the use of a microporous monolayer graphene oxide as a carbon carrier can reduce the shielding of platinum particles, so that more platinum particles are exposed and directly participate in the catalytic reaction. This can increase the electrochemical active area of ​​platinum, thereby improving the electrochemical activity and response speed of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above and / or additional aspects and advantages of the present invention will become apparent from the description of the embodiments in conjunction with the following drawings. Obvious and easy to understand, where:

[0037] Figure 1 This is a SEM image of the through-type platinum / graphene catalyst prepared in Example 2 of the present invention;

[0038] Figure 2 This is a SEM image of the through-type platinum / graphene catalyst prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0039] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present application. However, it is obvious to those skilled in the art that the present application embodiments can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present application embodiments, some technical features well known in the art are not described.

[0040] Herein, ordinal numbers such as “first” and “second” cited in the present application are merely identifications and do not have any other meanings, such as a specific order, etc. Moreover, for example, the term “first component” itself does not imply the existence of the “second component”, and the term “second component” itself does not imply the existence of the “first component”.

[0041] In this document, “upper”, “lower”, “front”, “back”, “left”, “right”, etc. are only used to indicate the relative position relationship between related parts, rather than to limit the absolute positions of these related parts.

[0042] In this document, “equal”, “same”, etc. are not strictly limited in a mathematical and / or geometric sense, but also include errors that can be understood by those skilled in the art and are allowed in manufacturing or use.

[0043] Unless otherwise stated, the numerical ranges herein include not only the entire range within its two endpoints but also include several sub-ranges contained therein.

[0044] The present application provides a method for preparing platinum nanoparticles, comprising the following steps:

[0045] S11, mixing high concentration chloroplatinic acid and ethylene glycol, reacting under ultrasonic conditions, and taking a precipitate;

[0046] S12, mixing the precipitate in step S1 with low concentration chloroplatinic acid and ethylene glycol to obtain platinum nanoparticles;

[0047] The mass concentration of the high concentration chloroplatinic acid is 5-10%;

[0048] The mass concentration of the low-concentration chloroplatinic acid is 0.5-2%.

[0049] In some embodiments of the present application, the reaction in step S11 satisfies at least one of the following conditions:

[0050] (1) The reaction temperature is 70-90°C;

[0051] (2) The reaction is carried out under mechanical stirring conditions;

[0052] (3) The ultrasound duration is 0.5 to 1.5 hours;

[0053] (4) After the reaction, let it stand for 5 to 7 hours;

[0054] (5) The volume ratio of high concentration chloroplatinic acid to ethylene glycol is 100:1.

[0055] In some embodiments of the present application, the reaction in step S12 satisfies at least one of the following conditions:

[0056] (1) The reaction temperature is 30 to 50°C;

[0057] (2) The reaction is carried out under mechanical stirring conditions;

[0058] (3) The reaction time is 22 to 26 hours;

[0059] (4) After the reaction, let it stand for 5-7 hours;

[0060] (5) The volume ratio of low concentration chloroplatinic acid to ethylene glycol is 100:1.

[0061] The present application also provides a method for preparing a through-type carbon-based catalyst, comprising the following steps:

[0062] S21, etching the monolayer graphene oxide to obtain a monolayer graphene oxide having a microporous structure; optionally, the micropores of the monolayer graphene oxide have a pore size of 0.5 nm to 2.0 nm;

[0063] S22, mixing the single-layer graphene oxide with a microporous structure in step S21 with the platinum particles described in any one of claims 1 to 3, adding hydrazine hydrate to react, and obtaining a through-type platinum / graphene catalyst after separation.

[0064] In this embodiment, the separation in S22 is specifically: centrifuging at a centrifugal speed of 5000r-8000r / min for 10-30min, and the obtained precipitate is the through-type platinum / graphene catalyst.

[0065] In this embodiment, the pore size of the micropores of the single-layer graphene oxide is 0.5 nm to 2.0 nm. If the pore size is too small, the generated platinum particles cannot penetrate, and if the pore size is too large, the penetration effect cannot be achieved.

[0066] In some embodiments of the present application, the single-layer graphene in step S21 is graphene oxide prepared by step-by-step centrifugation.

[0067] Optionally, a step of graphene separation:

[0068] S211, centrifuging at a centrifugal speed of 1000 to 2000 r / min for 10 to 30 min to separate the unexfoliated graphene oxide;

[0069] S212, centrifuging at a centrifugal speed of 10000-12000 r / min for 10-30 min, removing the supernatant, and the precipitate is a single-layer graphene oxide sheet;

[0070] S213, disperse again and set aside.

[0071] Preferably, the graphene oxide is prepared by Hummers redox method.

[0072] In some embodiments of the present application, the etching process in step S21 is physical etching and / or chemical etching.

[0073] Preferably, the etching in step S21 includes the following steps:

[0074] S211, placing the single-layer graphene oxide in sodium hydroxide with a mass fraction of 10-40%, and etching at a temperature of 60-90° C. for 1-48 hours;

[0075] S212, cleaning the etched single-layer graphene oxide.

[0076] In some embodiments of the present application, the reaction temperature in step S22 is 70-90° C., and the reaction time is 5-7 h.

[0077] The present application also provides a through-type carbon-based catalyst, which is prepared according to the above-mentioned preparation method.

[0078] Example 1

[0079] (1) preparing graphene oxide by Hummers redox method, and separating the desired single-layer graphene oxide by step-by-step centrifugation;

[0080] (2) 5 g of graphene oxide was etched with 40% NaOH at 90° C. for 6 h to produce 0.5 nm micropores, and then washed with ultrapure water to remove NaOH;

[0081] (3) Pt particle reduction

[0082] Step 1: 500ml 5% chloroplatinic acid, 5ml ethylene glycol; 80℃ high-speed mechanical stirring and ultrasonic for 1h; let stand for 6h, centrifuge, and recover the supernatant for later use.

[0083] Step 2: 500 ml 0.5% chloroplatinic acid; 5 ml ethylene glycol; low-speed magnetic stirring at 40°C for 24 hours; standing for 6 hours to obtain nano-platinum particles;

[0084] (4) The single-layer graphene oxide with a microporous structure prepared in step (2), the nano-platinum particles prepared in step (3), and hydrazine hydrate are mixed and reacted at 80° C. for 6 hours to obtain a through-type platinum / graphene catalyst.

[0085] Example 2

[0086] (1) preparing graphene oxide by Hummers redox method, and separating the desired single-layer graphene oxide by step-by-step centrifugation;

[0087] (2) 3 g of graphene oxide was etched at 90° C. for 16 h using 30% NaOH to produce nanopores, and then washed with ultrapure water to remove NaOH;

[0088] (3) Pt particle reduction

[0089] Step 1: 500ml 8% chloroplatinic acid, 5ml ethylene glycol; 70℃ high-speed mechanical stirring and ultrasonic for 0.5h; let stand for 6h, centrifuge, and recover the supernatant for later use.

[0090] Step 2: 500 ml 1% chloroplatinic acid; 5 ml ethylene glycol; 30°C low speed magnetic stirring for 22 hours; let stand for 5 hours to obtain nano-platinum particles;

[0091] (4) Mixing the single-layer graphene oxide with a microporous structure prepared in step (2), the nano-platinum particles prepared in step (3), and hydrazine hydrate, and reacting at 70° C. for 5 h to obtain Figure 1-2 The through-type platinum / graphene catalyst shown. Figure 1 As shown in Figure 1, nano-platinum particles are uniformly loaded on graphene oxide. Figure 2 As shown, the platinum particles are exposed above and below in the monolayer graphene oxide and are less blocked by the carbon support.

[0092] Example 3

[0093] (1) preparing graphene oxide by Hummers redox method, and separating the desired single-layer graphene oxide by step-by-step centrifugation;

[0094] (2) Etching 1 g of graphene oxide with 30% NaOH at 80°C for 20 h to produce nanopores, and then washing with ultrapure water to remove NaOH;

[0095] (3) Pt particle reduction

[0096] Step 1: 500ml 10% chloroplatinic acid, 5ml ethylene glycol; 90℃ high-speed mechanical stirring and ultrasonic for 1.5h; let stand for 7h, centrifuge, and recover the supernatant for later use.

[0097] Step 2: 500 ml 2% chloroplatinic acid; 5 ml ethylene glycol; 50°C low speed magnetic stirring for 26 hours; let stand for 7 hours to obtain nano-platinum particles;

[0098] (4) The single-layer graphene oxide with a microporous structure prepared in step (2), the nano-platinum particles prepared in step (3), and hydrazine hydrate are mixed and reacted at 90° C. for 7 hours to obtain a through-type platinum / graphene catalyst.

[0099] Comparative Example 1

[0100] (1) preparing graphene oxide by Hummers redox method, and separating the desired single-layer graphene oxide by step-by-step centrifugation;

[0101] (2) 3 g of graphene oxide was etched with 40% NaOH at 90° C. for 6 h to produce nanopores, and then washed with ultrapure water to remove NaOH;

[0102] (3) Pt particle reduction

[0103] The Pt particles to be reduced are added to a sodium sulfite solution, and the reaction is usually carried out at a temperature of 70° C. for 2 hours to obtain platinum particles;

[0104] (4) The single-layer graphene oxide with a microporous structure prepared in step (2), the platinum particles prepared in step (3), and hydrazine hydrate are mixed and reacted at 80° C. for 6 hours to obtain a platinum / graphene catalyst.

[0105] Comparative Example 2

[0106] (1) preparing graphene oxide by Hummers redox method, and separating the desired single-layer graphene oxide by step-by-step centrifugation;

[0107] (2) Pt particle reduction

[0108] Step 1: 500ml 5% chloroplatinic acid, 5ml ethylene glycol; 80℃ high-speed mechanical stirring and ultrasonic for 1h; let stand for 6h, centrifuge, and recover the supernatant for later use.

[0109] Step 2: 500 ml 0.5% chloroplatinic acid; 5 ml ethylene glycol; low-speed magnetic stirring at 40°C for 24 hours; standing for 6 hours to obtain nano-platinum particles;

[0110] (3) The single-layer graphene oxide prepared in step (1), the nano-platinum particles prepared in step (2), and hydrazine hydrate are mixed and reacted at 80° C. for 6 hours to obtain a platinum / graphene catalyst.

[0111] Comparative Example 3

[0112] (1) preparing graphene oxide by Hummers redox method, and separating the desired single-layer graphene oxide by step-by-step centrifugation;

[0113] (2) 5 g of graphene oxide was etched with 30% NaOH at 80° C. for 12 h to produce nanopores, and then washed with ultrapure water to remove NaOH;

[0114] (3) Pt particle reduction

[0115] 500ml 10% chloroplatinic acid, 5ml ethylene glycol; 90℃ high-speed mechanical stirring and ultrasonic for 1.5h; let stand for 7h, centrifuge, and recover the supernatant for later use.

[0116] (4) The single-layer graphene oxide with a microporous structure prepared in step (2), the nano-platinum particles prepared in step (3), and hydrazine hydrate are mixed and reacted at 90° C. for 7 hours to obtain a through-type platinum / graphene catalyst.

[0117] Comparative Example 4

[0118] (1) preparing graphene oxide by Hummers redox method, and separating the desired single-layer graphene oxide by step-by-step centrifugation;

[0119] (2) Etching 1 g of graphene oxide with 30% NaOH at 80°C for 20 h to produce nanopores, and then washing with ultrapure water to remove NaOH;

[0120] (3) Pt particle reduction

[0121] 500ml 2% chloroplatinic acid; 5ml ethylene glycol; 50℃ low speed magnetic stirring for 26h; let stand for 7h to obtain nano-platinum particles;

[0122] (4) The single-layer graphene oxide with a microporous structure prepared in step (2), the nano-platinum particles prepared in step (3), and hydrazine hydrate are mixed and reacted at 90° C. for 7 hours to obtain a through-type platinum / graphene catalyst.

[0123] The average particle size and particle size range of the nano-platinum particles prepared in the above examples and comparative examples are shown in Table 1:

[0124] name Average particle size / nm Particle size range / nm Example 1 2.2 1.8～2.8 Example 2 3.2 2.7～3.6 Example 3 6.2 5.3～8.4 Comparative Example 1 1.5 0.7～3.0 Comparative Example 2 2.8 2.3～2.9 Comparative Example 3 4.2 1.2～8.1 Comparative Example 4 2.1 0.9～3.5

[0125] The catalysts prepared in the above examples and comparative examples were subjected to BET test to obtain specific surface area, and RDE test to obtain electrochemical active area. The test results are shown in Table 2:

[0126] Table 2:

[0127] name Specific surface area Electrochemically active area Example 1 <![CDATA[521cm 2 / mg]]> <![CDATA[112cm 2 / mg]]> Example 2 <![CDATA[845cm 2 / mg]]> <![CDATA[130cm 2 / mg]]> Example 3 <![CDATA[823cm 2 / mg]]> <![CDATA[106cm 2 / mg]]> Comparative Example 1 <![CDATA[812cm 2 / mg]]> <![CDATA[70cm 2 / mg]]> Comparative Example 2 <![CDATA[450cm 2 / mg]]> <![CDATA[63cm 2 / mg]]> Comparative Example 3 <![CDATA[682cm 2 / mg]]> <![CDATA[89cm 2 / mg]]> Comparative Example 4 <![CDATA[657cm 2 / mg]]> <![CDATA[86cm 2 / mg]]>

[0128] Unless otherwise defined, the technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art in the technical field of this application. The terms used herein are only for describing specific implementation purposes and are not intended to limit this application. Terms such as "setting" appearing in this article can mean that one component is directly attached to another component, or that one component is attached to another component through an intermediate. Features described in this article in one embodiment may be applied to another embodiment alone or in combination with other features, unless the feature is not applicable in the other embodiment or otherwise specified.

[0129] The present application has been described through the above-mentioned embodiments, but it should be understood that the above-mentioned embodiments are only for the purpose of example and description, and are not intended to limit the present application to the described embodiments. It can be understood by those skilled in the art that more variations and modifications can be made according to the teachings of the present application, and these variations and modifications all fall within the scope of protection claimed in the present application.

Claims

1. A method for preparing platinum nanoparticles, It is characterized in that The following steps are involved: S11, mixing high concentration chloroplatinic acid and ethylene glycol, reacting under ultrasonic conditions, and taking a precipitate; S12, mixing the precipitate in step S1 with low concentration chloroplatinic acid and ethylene glycol to obtain platinum nanoparticles; The mass concentration of the high concentration chloroplatinic acid is 5-10%; The mass concentration of the low-concentration chloroplatinic acid is 0.5-2%.

2. The method for preparing platinum nanoparticles according to claim 1, It is characterized in that The reaction in step S11 satisfies at least one of the following conditions: (1) The reaction temperature is 70-90°C; (2) The reaction is carried out under mechanical stirring conditions; (3) The ultrasound duration is 0.5 to 1.5 hours; (4) After the reaction, let it stand for 5 to 7 hours; (5) The volume ratio of high concentration chloroplatinic acid to ethylene glycol is 100:

1.

3. The method for preparing platinum nanoparticles according to claim 1, It is characterized in that The reaction in step S12 satisfies at least one of the following conditions: (1) The reaction temperature is 30 to 50°C; (2) The reaction is carried out under mechanical stirring conditions; (3) The reaction time is 22 to 26 hours; (4) After the reaction, let it stand for 5-7 hours; (5) The volume ratio of low concentration chloroplatinic acid to ethylene glycol is 100:

1.

4. A method for preparing a through-type carbon-based catalyst, It is characterized in that The following steps are involved: S21, etching the single-layer graphene oxide to obtain a single-layer graphene oxide with a microporous structure; S22, mixing the single-layer graphene oxide with a microporous structure in step S21 with the platinum nanoparticles according to any one of claims 1 to 3, adding hydrazine hydrate to react, and preparing a through-type platinum / graphene catalyst.

5. The method for preparing the through-type carbon-based catalyst according to claim 4, It is characterized in that The single-layer graphene in step S21 is graphene oxide prepared by step-by-step centrifugation.

6. The method for preparing the through-type carbon-based catalyst according to claim 5, It is characterized in that The graphene oxide is prepared by Hummers redox method.

7. The method for preparing the through-type carbon-based catalyst according to claim 4, It is characterized in that The etching process in step S21 is physical etching and / or chemical etching.

8. The method for preparing the through-type carbon-based catalyst according to claim 4, It is characterized in that The etching in step S21 includes the following steps: S211, placing the single-layer graphene oxide in sodium hydroxide with a mass fraction of 10-40%, and etching at a temperature of 60-90° C. for 1-48 hours; S212, cleaning the etched single-layer graphene oxide.

9. The method for preparing the through-type carbon-based catalyst according to claim 4, It is characterized in that The reaction temperature in step S22 is 70-90° C., and the reaction time is 5-7 hours.

10. A through-type carbon-based catalyst, It is characterized in that Prepared according to the preparation method described in any one of claims 4 to 9.

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