Platinum-carbon catalyst, its preparation method and application

Abstract

The application belongs to the field of fuel cell catalysts, and particularly relates to a platinum-carbon catalyst and a preparation method and application thereof. The application preliminarily obtains high specific surface area graphene by using a PECVD method, and then obtains a nitrogen-doped, high specific surface area, highly graphitized carbon carrier by high-temperature calcination at 1200-2500 DEG C and ammonia heat treatment, so that the platinum catalyst prepared therefrom has good catalyst activity and high carrier corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell catalysts, specifically relating to a platinum-carbon catalyst, its preparation method, and its application. Background Technology

[0002] Hydrogen fuel cells, as electrochemical energy conversion devices that directly convert the chemical energy of hydrogen and oxygen into electrical energy, possess characteristics such as high energy conversion efficiency, high power density, rapid room temperature start-up, and zero pollution, making them a promising candidate for applications in the automotive fuel cell field. The catalyst is a key material, with Pt-based carbon-supported catalysts currently being the most widely used. The properties of the carbon support are crucial to the overall performance and stability of the catalyst. Carbon supports undergo electrochemical corrosion under strong acid and high potential environments, leading to the shedding and aggregation of platinum particles, ultimately resulting in reduced fuel cell performance and shortened lifespan.

[0003] Traditional high-temperature calcination graphitization methods often damage the porosity and specific surface area of ​​carbon, while also weakening the interaction between the carbon support and platinum nanoparticles. This makes it difficult for platinum nanoparticles to be uniformly dispersed on the carbon support, which will reduce the utilization rate of platinum atoms and significantly increase the oxygen transport resistance of the catalyst layer. Summary of the Invention

[0004] To address the above problems, this invention provides a method for preparing a platinum-carbon catalyst, comprising the following steps:

[0005] (1) Preparation of graphene GC: 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 was kept at a temperature under a nitrogen atmosphere to obtain HGC;

[0007] (3) Preparation of highly graphitized nitrogen-doped graphene HGNC: HGC was kept at a temperature under an ammonia atmosphere to obtain HGNC;

[0008] (4) Preparation of platinum carbon catalyst Pt / HGNC: Pt(acac)2 and HGNC powder were added to a mixture 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 the platinum carbon catalyst.

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

[0010] Furthermore, the heat preservation conditions described in step (2) are: heat preservation at 1200-2500℃ for 4 hours, with a heating rate of 10℃ / min.

[0011] Furthermore, the heat preservation conditions described in step (3) are: heat preservation at 700℃ for 0.5-2h, and heating rate of 5℃ / min.

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

[0013] Furthermore, the reaction conditions described in step (4) are as follows: after stirring for 15 minutes, heat to 150°C and react for 2 hours.

[0014] The present invention also provides a platinum-carbon catalyst, which is prepared by the above-described method.

[0015] This invention also provides the application of the above-mentioned catalyst in the preparation of hydrogen fuel cells.

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

[0017] This invention utilizes high-temperature treatment of graphene prepared by PECVD to significantly enhance its graphitization degree. Subsequent nitrogen doping via ammonia heat treatment improves the defects in the carbon support, facilitating the adhesion and uniform dispersion of platinum particles. The resulting platinum-carbon catalyst exhibits both high activity and high durability. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

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

[0020] Figure 2 The image shows a TEM image of the 50% Pt / C catalyst prepared in Example 1.

[0021] Figure 3 The image shows a comparison of CV and LSV before and after accelerated aging tests of the self-made 50% Pt / C catalyst in Example 1.

[0022] Figure 4 Comparative Example 2: CV and LSV comparison before and after accelerated aging test of the commercial catalyst. Detailed Implementation

[0023] Various exemplary embodiments of the present invention are now described in detail. Unless otherwise specified, the methods used in the embodiments are conventional methods, and the reagents used are commercially available reagents or reagents prepared using conventional methods. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics, and embodiments of the present invention.

[0024] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0025] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0026] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

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

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

[0029] Graphene preparation by PECVD (GC):

[0030] 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. The operating frequency was set to 13.56 MHz, the power to 500 W and the temperature to 800 °C for graphene growth. After the reaction was completed, the graphene GC was collected after the temperature dropped to room temperature.

[0031] Highly graphitized graphene (HGC):

[0032] The GC was kept at 1200-2500℃ for 4 hours under a nitrogen atmosphere, with a heating rate of 10℃ / min.

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

[0034] HGC was kept at 700℃ for 0.5-2h in an 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 to 600ml of a mixed liquid solution of oleylamine and oleic acid, and ultrasonically disperse for about 1 hour to prepare a black mixed solution.

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

[0038] After natural cooling, the catalyst is washed with ultrapure water and dried under vacuum to obtain the final platinum-carbon catalyst.

[0039] Example 1

[0040] The GC heat treatment temperature was 1800℃, and the HGC heat treatment time was 0.5h.

[0041] Example 2

[0042] The GC heat treatment temperature was 1800℃, and the HGC heat treatment time was 1 hour.

[0043] Comparative Example 1

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

[0045] Comparative Example 2

[0046] Commercial 50% platinum-carbon catalyst.

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

[0048] Results Analysis

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

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

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

[0052] Figure 3 The initial electrochemical active area (ECSA) and mass activity (MA) of Pt / HGNC were 63.46 and 0.32, respectively. After 5 k cycles at high potential, the ECSA and MA were 58.45 and 0.3, respectively, representing 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 5 k cycles at high potential, the ECSA and MA were 39.64 and 0.2, respectively, representing a loss of 26.32% and 25.9%.

[0054] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a platinum-carbon catalyst, characterized in that, Includes the following steps: (1) Preparation of graphene GC: 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 was kept at a temperature under a nitrogen atmosphere to obtain HGC; (3) Preparation of highly graphitized nitrogen-doped graphene HGNC: HGC was kept at a temperature under an ammonia atmosphere to obtain HGNC; (4) Preparation of platinum carbon catalyst Pt / HGNC: Pt(acac)2 and HGNC powder were added to a mixture 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 the platinum-carbon catalyst. The graphene growth conditions described in step (1) are: 13.56MHz, 500W power, and 800℃. The heat preservation conditions described in step (2) are: heat preservation at 1800℃ for 4 hours, with a heating rate of 10℃ / min; The heat preservation conditions described in step (3) are: heat preservation at 700℃ for 0.5-2h, and heating rate of 5℃ / min.

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

1.

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

4. A platinum-carbon catalyst, characterized in that, It is prepared by the preparation method described in any one of claims 1-3.

5. The application of the platinum-carbon catalyst as described in claim 4 in the preparation of hydrogen fuel cells.

Images