Platinum-carbon catalyst as well as preparation method and application thereof

Abstract

The invention belongs to the field of fuel cell catalysts, and particularly relates to a platinum-carbon catalyst and a preparation method and application thereof. Graphene with a high specific surface area is preliminarily obtained through a PECVD method, then high-temperature calcination at the temperature of 1200-2500 DEG C and ammonia gas heat treatment are carried out, the nitrogen-doped carbon carrier with the high specific surface area and high graphitization is finally obtained, and the platinum catalyst prepared through the method has good catalyst activity and high carrier corrosion resistance.

Description

Technical Field

[0001] The present invention belongs to the field of fuel cell catalysts, and in particular relates to a platinum-carbon catalyst and a preparation method and application thereof. Background Art

[0002] As an electrochemical energy conversion device that directly converts the chemical energy of hydrogen and oxygen into electrical energy, hydrogen fuel cells have the characteristics of high energy conversion efficiency, high power density, fast room temperature start-up and zero pollution, and have great application prospects in the field of automotive fuel cells. Catalysts are key materials, and the most widely used ones are still Pt-based carbon-supported catalysts. The properties of carbon supports are crucial to the overall performance and stability of the catalyst. Carbon supports will undergo electrochemical corrosion in strong acidic and high potential environments, which will lead to the shedding and agglomeration of platinum particles, and ultimately reduce the performance and life of the fuel cell.

[0003] The traditional high-temperature calcination graphitization method often damages the porosity and specific surface area of ​​carbon, and also weakens the effect of the carbon carrier on the platinum nanoparticles, making it difficult for the platinum nanoparticles to be evenly dispersed on the carbon carrier, which will reduce the utilization rate of platinum atoms and significantly increase the oxygen transmission resistance of the catalytic layer. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for preparing a platinum-carbon catalyst, comprising the following steps:

[0005] (1) Preparation of graphene GC: The reaction gases CH4, H2 and Ar were introduced into the reaction system at flow rates of 10 sccm, 40 sccm and 5 sccm, respectively, to grow graphene. After the reaction was completed, the temperature was lowered and the obtained graphene GC was collected;

[0006] (2) Preparation of highly graphitized graphene HGC: GC is kept warm under a nitrogen atmosphere to obtain HGC;

[0007] (3) Preparation of highly graphitized nitrogen-doped graphene HGNC: HGC is kept warm in an ammonia atmosphere to obtain HGNC;

[0008] (4) Preparation of platinum-carbon catalyst Pt / HGNC: Pt(acac)2 and HGNC powders were added to a mixed liquid of oleylamine and oleic acid, and ultrasonically dispersed to prepare a black mixed solution; the black mixed solution was reacted under N2 protection; after natural cooling, it was washed with ultrapure water and vacuum dried to finally obtain a platinum-carbon catalyst.

[0009] Furthermore, the graphene growth conditions in step (1) are: 13.56 MHz, 500 W power, and 800° C. temperature.

[0010] Furthermore, the insulation conditions in step (2) are: 1200-2500°C for 4 hours, and a heating rate of 10°C / min.

[0011] Furthermore, the insulation conditions in step (3) are: 700° C. for 0.5-2 h, and a heating rate of 5° C. / min.

[0012] Furthermore, the mass ratio of Pt(acac)2 and HGNC in step (4) is 2:1.

[0013] Furthermore, the reaction conditions in step (4) are: stirring for 15 minutes, heating to 150° C., and reacting for 2 hours.

[0014] The present invention also provides a platinum-carbon catalyst prepared by the above preparation method.

[0015] The present invention also provides application of the catalyst in preparing hydrogen fuel cells.

[0016] The present invention has the following beneficial effects:

[0017] The present invention treats graphene prepared by the PECVD method at high temperature to significantly improve its graphitization degree, and then performs nitrogen doping by ammonia heat treatment to increase carbon carrier defects, which is conducive to the attachment and uniform dispersion of platinum particles. The platinum-carbon catalyst prepared by the carrier has both high activity and high durability. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1 TEM images of the carbon supports in Comparative Example 1 and Example 1.

[0020] Figure 2 This is the TEM image of the homemade 50% Pt / C catalyst in Example 1.

[0021] Figure 3 This is a comparison chart of CV and LSV of the homemade 50% Pt / C catalyst in Example 1 before and after accelerated aging test.

[0022] Figure 4 This is a comparison chart of CV and LSV of the commercial catalyst of Comparative Example 2 before and after the accelerated aging test. DETAILED DESCRIPTION

[0023] Now, various exemplary embodiments of the present invention are described in detail. The methods in the examples are conventional methods unless otherwise specified, and the reagents used are conventional commercially available reagents or reagents prepared by conventional methods unless otherwise specified. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features and embodiments of the present invention.

[0024] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0025] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0026] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0027] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0028] The preparation method of 50% platinum carbon catalyst (Pt / HGNC) in this embodiment is as follows:

[0029] Preparation of graphene (GC) by PECVD:

[0030] The reaction gases CH4, H2 and Ar were introduced into the reaction system at flow rates of 10sccm, 40sccm and 5sccm respectively, and the operation was set to 13.56MHz, the power was 500W, and the temperature was 800℃ to grow graphene. After the reaction was completed, the temperature was lowered to room temperature and the obtained graphene GC was collected;

[0031] Highly Graphitized Graphene (HGC):

[0032] The GC was kept at 1200-2500°C for 4 h under nitrogen atmosphere, with a heating rate of 10°C / min;

[0033] Highly graphitized nitrogen-doped graphene (HGNC):

[0034] Keep HGC at 700℃ for 0.5-2h under ammonia atmosphere, with a heating rate of 5℃ / min;

[0035] 50% platinum carbon catalyst (Pt / HGNC):

[0036] Take 2g of Pt(acac)2 and 1g of HGNC powder, add them into 600ml of the mixed liquid solution of oleylamine and oleic acid, and disperse them by ultrasonic for about 1h to prepare a black mixed solution;

[0037] Add the prepared black mixed solution into container A, stir for 15 minutes under N2 protection, heat the mixed solution to 150°C, and react for 2 hours;

[0038] After natural cooling, the product was washed with ultrapure water and dried in vacuum to finally obtain a platinum-carbon catalyst.

[0039] Example 1

[0040] The GC heat treatment temperature is 1800°C and the HGC heat treatment time is 0.5h.

[0041] Example 2

[0042] The GC heat treatment temperature is 1800°C, and the HGC heat treatment time is 1 h.

[0043] Comparative Example 1

[0044] No high temperature and ammonia heat treatment: GC.

[0045] Comparative Example 2

[0046] Commercialization of 50% platinum-carbon catalyst.

[0047] The above samples were subjected to accelerated aging tests under the following test conditions: 0.1 mol / L HClO4, 5000 scans, 500 mV / s scan speed, and a scan voltage range of 1-1.5 V.

[0048] Results Analysis

[0049] The results are as follows Figure 1-4 shown.

[0050] from Figure 1 It can be seen that the graphitization degree of HGNC is significantly improved compared with GC;

[0051] from Figure 2It can be seen that the Pt nanoparticles are uniformly dispersed throughout the support;

[0052] Figure 3 :The initial electrochemical active area (ECSA) and mass activity (MA) of Pt / HGNC were 63.46 and 0.32, respectively. After 5k cycles of high potential, the ECSA and MA were 58.45 and 0.3, respectively, with a loss of 7.9% and 6.25%;

[0053] Figure 4 The initial electrochemical active area (ECSA) and mass activity (MA) of commercial Pt / C were 53.8 and 0.27, respectively. After 5k cycles of high potential, the ECSA and MA were 39.64 and 0.2, respectively, with a loss of 26.32% and 25.9%, respectively.

[0054] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a platinum-carbon catalyst, characterized in that: The following steps are involved: (1) Preparation of graphene GC: The reaction gases CH4, H2 and Ar were introduced into the reaction system at flow rates of 10 sccm, 40 sccm and 5 sccm, respectively, to grow graphene. After the reaction was completed, the temperature was lowered and the obtained graphene GC was collected; (2) Preparation of highly graphitized graphene HGC: GC is kept warm under a nitrogen atmosphere to obtain HGC; (3) Preparation of highly graphitized nitrogen-doped graphene HGNC: HGC is kept warm in an ammonia atmosphere to obtain HGNC; (4) Preparation of platinum carbon catalyst Pt / HGNC: Pt(acac)2 and HGNC powders were added to a mixed liquid of oleylamine and oleic acid, and ultrasonically dispersed to prepare a black mixed solution; The black mixed solution was reacted under the protection of N2; after natural cooling, it was washed with ultrapure water and vacuum dried to finally obtain a platinum-carbon catalyst.

2. The preparation method according to claim 1, characterized in that: The graphene growth conditions in step (1) are: 13.56 MHz, power 500 W, temperature 800°C.

3. The preparation method according to claim 1, characterized in that: The insulation conditions in step (2) are: 1200-2500° C. for 4 hours, and a heating rate of 10° C. / min.

4. The preparation method according to claim 1, characterized in that: The insulation conditions in step (3) are: 700° C. for 0.5-2 h, and a heating rate of 5° C. / min.

5. The preparation method according to claim 1, characterized in that: The mass ratio of Pt(acac)2 and HGNC in step (4) is 2:

1.

6. The preparation method according to claim 1, characterized in that: The reaction conditions in step (4) are: stirring for 15 minutes, heating to 150° C., and reacting for 2 hours.

7. A platinum-carbon catalyst, characterized in that Prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the catalyst as claimed in claim 7 in the preparation of hydrogen fuel cells.

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