Low noble metal heterojunction fuel cell catalysts, methods of making and using the same

Abstract

The application discloses a preparation method of a low-noble-metal heterojunction fuel cell catalyst, which comprises the following steps: (1) preparing Pt-Co alloy nanoparticles; (2) preparing a cobalt acetate ethanol solution, placing the Pt-Co alloy nanoparticles in the cobalt acetate ethanol solution, stirring, growing a cobalt acetate film layer on the outer surface of the Pt-Co alloy nanoparticles, and obtaining the low-noble-metal heterojunction fuel cell catalyst. The preparation method can effectively reduce the use of Pt, reduce the preparation cost of the catalyst, and is suitable for large-scale application. The low-noble-metal heterojunction fuel cell catalyst has high oxygen reduction activity and can effectively improve the catalytic reaction efficiency.

Description

Technical Field

[0001] This invention relates to the field of fuel cell technology, and in particular to a low-noble-metal heterojunction fuel cell catalyst and its preparation method. Background Technology

[0002] With the rapid depletion of fossil fuels and ever-increasing energy demand, the development of efficient, clean, and sustainable energy storage and conversion technologies is imperative. Electrochemical energy, especially fuel cells, has attracted much attention due to its advantages such as high efficiency, low cost, abundant fuel, and environmentally friendly operation. Fuel cells can directly convert the chemical energy of fuel into electrical energy through electrochemical reactions, making them an important low-carbon energy conversion device. Based on the type of fuel, they can be classified into hydrogen fuel cells, direct methanol fuel cells, microbial fuel cells, etc.

[0003] The oxygen reduction reaction (ORR) at the cathode is a crucial half-reaction determining the reaction kinetics of these fuel cells. However, the slow kinetics of the ORR at the cathode significantly limit the commercial application of various fuel cells. Therefore, developing high-performance ORR catalysts is essential for the development of these new energy devices. Currently, noble metal Pt-based catalysts, such as commercially available Pt / C, are considered the most advanced ORR electrocatalysts. However, Pt-based catalysts are prone to poisoning, deformation leading to deactivation, and poor stability during operation, and their scarcity and high cost hinder their large-scale application. Therefore, designing and developing efficient and inexpensive non-noble metal electrocatalysts to replace purely Pt-based catalysts is imperative. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a low-precious-metal heterojunction fuel cell catalyst and its preparation method, which can effectively reduce the use of precious metals, reduce the catalyst preparation cost, and is suitable for its large-scale application.

[0005] The technical problem to be solved by the invention is to provide a low-noble-metal heterojunction fuel cell catalyst and its preparation method, which has high oxygen reduction activity, good cycle stability, high resistance to poisoning, and can effectively improve the catalytic reaction efficiency.

[0006] The technical problem to be solved by the invention is to provide a low-precious-metal heterojunction fuel cell catalyst for the application of fuel cells, thereby reducing the cost of the battery and improving its performance and stability.

[0007] To address the aforementioned technical problems, this invention provides a method for preparing a low-noble-metal heterojunction fuel cell catalyst, comprising the following steps:

[0008] (1) Preparation of Pt-Co alloy nanoparticles;

[0009] (2) Prepare a cobalt acetate ethanol solution, place the Pt-Co alloy nanoparticles in the cobalt acetate ethanol solution, stir, and grow a cobalt acetate thin film layer on the outer edge of the surface of the Pt-Co alloy nanoparticles to obtain a low-noble metal heterojunction fuel cell catalyst.

[0010] In one embodiment, step (1) is performed by the following method:

[0011] Benzoic acid was added to a benzyl alcohol solution containing polyvinylpyrrolidone, and after stirring until homogeneous, platinum acetylacetonate and cobalt acetylacetonate were added. The mixture was stirred and reacted at a preset temperature to obtain Pt-Co alloy nanoparticles.

[0012] In one embodiment, the ratio of the amount of benzoic acid added to the sum of the amounts of platinum acetylacetonate and cobalt acetylacetonate added is (6-12):(4-10) by weight.

[0013] The ratio of the amount of platinum acetylacetone to cobalt acetylacetone added is (1-2):(1-2).

[0014] In one embodiment, the amount of benzoic acid added is 60 mg to 120 mg;

[0015] The amount of platinum acetylacetone added is 20 mg to 50 mg, and the amount of cobalt acetylacetone added is 20 mg to 50 mg;

[0016] The concentration of the benzyl alcohol solution containing polyvinylpyrrolidone is 5 mg / ml to 20 mg / ml;

[0017] The amount of benzyl alcohol solution containing polyvinylpyrrolidone added is 18 ml to 25 ml.

[0018] In one embodiment, the preset temperature is 150℃~200℃, and the reaction time is 8h~24h.

[0019] In one embodiment, in step (2), the concentration of the cobalt acetate ethanol solution is 5 mg / ml to 20 mg / ml;

[0020] The amount of cobalt acetate ethanol solution added is 18 ml to 25 ml, and the amount of Pt-Co alloy nanoparticles added is 50 mg to 100 mg.

[0021] In one embodiment, the stirring time in step (2) is 12h to 24h.

[0022] In one embodiment, the particle size of the Pt-Co alloy nanoparticles is 5 nm to 20 nm;

[0023] The particle size of the low-noble-metal heterojunction fuel cell catalyst is 5nm to 20nm.

[0024] To address the aforementioned problems, this invention provides a low-noble-metal heterojunction fuel cell catalyst, which is prepared by the above-described method for preparing low-noble-metal heterojunction fuel cell catalysts.

[0025] Accordingly, the present invention also provides the application of the above-mentioned low-noble-metal heterojunction fuel cell catalyst in fuel cells.

[0026] Implementing this invention has the following beneficial effects:

[0027] This invention provides a low-noble-metal heterojunction fuel cell catalyst. It involves preparing Pt-Co alloy nanoparticles, then placing these nanoparticles in a cobalt acetate ethanol solution to grow a cobalt acetate thin film layer along the outer edge of the Pt-Co alloy nanoparticle surface, thus obtaining the final product. The catalyst prepared using this method has the following advantages:

[0028] (1) It effectively reduces the use of precious metal Pt, lowers the cost of catalyst preparation, and facilitates its large-scale application. At the same time, the morphology design of nanoparticles can provide a large number of reactive sites for oxygen reduction reaction, thereby improving the efficiency of catalytic reaction.

[0029] (2) The low-noble-metal heterojunction fuel cell catalyst designed in this invention is a Pt-Co alloy nanoparticle / basic cobalt acetate heterojunction. Due to its unique epitaxial growth, it can form an atomic-level contact interface. Through this interface design, the adsorption energy of oxygen-containing substances can be effectively adjusted, catalyzing the conversion of intermediate substances in the reaction and realizing a highly efficient four-electron catalytic process for the oxygen reduction reaction. At the same time, in addition to its interface design, the individual Pt-Co alloy nanoparticles and basic cobalt acetate can also effectively adsorb oxygen, improving the kinetics of the oxygen reduction reaction.

[0030] Therefore, the catalyst of this invention can effectively reduce the use of precious metals, lower costs, and possesses high oxygen reduction activity, good cycle stability, and high resistance to poisoning, thus effectively improving catalytic reaction efficiency. When used in the manufacture of fuel cells, it can reduce battery costs, improve battery performance and stability, and greatly broaden the commercial application scope of fuel cells. Attached Figure Description

[0031] Figure 1 This is a transmission electron microscope image of the low-noble metal heterojunction fuel cell catalyst prepared in Example 1 of the present invention.

[0032] Figure 2 The LSV curve shows the oxygen reduction activity of the low-noble-metal heterojunction fuel cell catalyst obtained in Example 1 of this invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in further detail below.

[0034] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings:

[0035] In this invention, the terms "combinations thereof", "any combination thereof", and "any combination thereof" include all suitable combinations of any two or more of the listed items.

[0036] In this invention, "preferred" is merely a description of a more effective implementation method or embodiment, and should be understood as not constituting a limitation on the scope of protection of this invention.

[0037] In this invention, the technical features described in an open-ended manner include both closed-ended technical solutions composed of the listed features and open-ended technical solutions that include the listed features.

[0038] In this invention, numerical ranges are involved, and unless otherwise specified, they include the two endpoints of the numerical range.

[0039] To address the shortcomings of existing fuel cell electrocatalysts, such as poor oxygen reduction reaction kinetics, insufficient cycle stability, low resistance to poisoning, and high cost, this invention provides a low-cost, high-performance fuel cell catalyst and its preparation method, comprising the following steps:

[0040] (1) Preparation of Pt-Co alloy nanoparticles;

[0041] In one embodiment, the preparation of Pt-Co alloy nanoparticles is accomplished by the following method:

[0042] Benzoic acid was added to a benzyl alcohol solution containing polyvinylpyrrolidone, and after stirring until homogeneous, platinum acetylacetonate and cobalt acetylacetonate were added. The mixture was stirred and reacted at a preset temperature to obtain Pt-Co alloy nanoparticles.

[0043] In one embodiment, the ratio of the amount of benzoic acid added to the sum of the amounts of platinum acetylacetonate and cobalt acetylacetonate added is (6-12):(4-10). Excessive addition of benzoic acid will prevent the Pt-Co elements from effectively combining to form Pt-Co alloy nanoparticles; insufficient addition of benzoic acid will lead to an increase in the size of the Pt-Co alloy nanoparticles and the formation of interparticle agglomeration.

[0044] In one embodiment, the ratio of platinum acetylacetonate to cobalt acetylacetonate is (1-2):(1-2). Excessive addition of platinum acetylacetonate will result in an excessive amount of Pt component in the Pt-Co alloy nanoparticles, increasing the catalyst preparation cost; excessive addition of cobalt acetylacetonate will result in an excessive amount of Co component in the Pt-Co alloy nanoparticles, failing to effectively achieve a uniform Pt-Co distribution. Preferably, the ratio of platinum acetylacetonate to cobalt acetylacetonate is 1:1. In one embodiment, both platinum acetylacetonate and cobalt acetylacetonate are added in powder form.

[0045] Preferably, the amount of benzoic acid added is 60mg to 120mg; the amount of acetylacetone platinum added is 20mg to 50mg; the amount of acetylacetone cobalt added is 20mg to 50mg; and the amount of benzyl alcohol solution containing polyvinylpyrrolidone added is 20ml to 25ml.

[0046] Furthermore, if the concentration of the benzyl alcohol solution containing polyvinylpyrrolidone is too high, the Pt-Co element will not be able to effectively form an alloy structure; if the concentration of the benzyl alcohol solution containing polyvinylpyrrolidone is too low, the Pt-Co alloy nanoparticles will grow rapidly through nucleation, resulting in larger particles that cannot effectively form a monodisperse nanoparticle morphology. Preferably, the concentration of the benzyl alcohol solution containing polyvinylpyrrolidone is 5 mg / ml to 20 mg / ml.

[0047] Finally, this invention prepares Pt-Co alloy nanoparticles via a hydrothermal method. During the hydrothermal reaction, excessively high preset temperatures will lead to increased thermal collisions, resulting in larger Pt-Co alloy particles and even agglomeration; excessively low preset temperatures will prevent the precursor from effectively decomposing and reacting to form Pt-Co alloy nanoparticles. In one embodiment, the preset temperature is 150℃~200℃. After reacting at 150℃~200℃ for 8h~24h, Pt-Co alloy nanoparticles are obtained.

[0048] The Pt-Co alloy nanoparticles prepared in this invention have a particle size range of 5 nm to 20 nm, and exhibit high purity, uniform and narrow particle size distribution, good dispersibility, and no agglomeration. This is beneficial for subsequent growth of a cobalt acetate thin film layer on their surface, resulting in a high-performance low-noble-metal heterojunction fuel cell catalyst. Furthermore, it effectively reduces the use of the precious metal Pt, lowering the catalyst preparation cost and facilitating large-scale production and application. Simultaneously, the morphology design of the nanoparticles provides a large number of reactive sites for the oxygen reduction reaction, improving catalytic efficiency.

[0049] (2) Prepare a cobalt acetate ethanol solution, place the Pt-Co alloy nanoparticles in the cobalt acetate ethanol solution, stir, and grow a cobalt acetate thin film layer on the outer edge of the surface of the Pt-Co alloy nanoparticles to obtain a low-noble metal heterojunction fuel cell catalyst.

[0050] This invention involves the epitaxial growth of a cobalt acetate thin film on the surface of Pt-Co alloy nanoparticles, forming an atomic-level contact interface. This interface design effectively modulates the adsorption energy of oxygen-containing substances and the conversion of intermediate substances in the catalytic reaction, achieving a highly efficient four-electron catalytic process for the oxygen reduction reaction. Simultaneously, the individual Pt-Co alloy nanoparticle / cobalt acetate heterostructure can also effectively adsorb oxygen, enhancing the kinetics of the oxygen reduction reaction.

[0051] In one embodiment, in step (2), the concentration of the cobalt acetate ethanol solution is 5 mg / ml to 20 mg / ml; the amount of cobalt acetate ethanol solution added is 18 ml to 25 ml; and the amount of Pt-Co alloy nanoparticles added is 50 mg to 100 mg. If the amount of Pt-Co alloy nanoparticles added to the cobalt acetate ethanol solution is too high, the content of basic cobalt acetate formed will be too low, failing to effectively form a heterojunction structure; if the amount of Pt-Co alloy nanoparticles added to the cobalt acetate ethanol solution is too low, the content of basic cobalt acetate formed will be too high, completely coating the Pt-Co alloy nanoparticles.

[0052] Furthermore, if the concentration of the cobalt acetate-ethanol mixed solution is too high, it will result in an excessive amount of basic cobalt acetate, completely coating the Pt-Co alloy nanoparticles; if the concentration of the cobalt acetate-ethanol mixed solution is too low, it will result in a insufficient amount of basic cobalt acetate, failing to effectively form a heterojunction structure. Preferably, the concentration of the cobalt acetate-ethanol mixed solution is 10 mg / ml to 15 mg / ml.

[0053] Furthermore, after mixing the Pt-Co alloy nanoparticles with the cobalt acetate-ethanol mixed solution and stirring continuously for a preset time, a low-noble-metal heterojunction fuel cell catalyst is obtained. If the preset time is too long, the cobalt acetate film layer on the surface of the Pt-Co alloy nanoparticles will be too thick, resulting in an excessively large size of the prepared low-noble-metal heterojunction fuel cell catalyst. This ultimately fails to provide a sufficient number of reactive sites for the oxygen reduction reaction, thus failing to effectively improve the catalytic reaction efficiency. Conversely, if the preset time is too short, the cobalt acetate film layer on the surface of the Pt-Co alloy nanoparticles will be too thin, leading to a reduced oxygen adsorption capacity and ultimately failing to effectively improve the catalytic reaction efficiency. Preferably, the preset time is 12h to 24h.

[0054] Accordingly, the present invention also provides a low-noble-metal heterojunction fuel cell catalyst prepared according to the above-described method. Preferably, the low-noble-metal heterojunction fuel cell catalyst has a size range of 5 nm to 20 nm. The morphology design of the nanoparticles can provide a large number of reactive sites for the oxygen reduction reaction, thereby improving the catalytic reaction efficiency. The low-noble-metal heterojunction fuel cell catalyst can be used in the preparation of fuel cells. When used in the fabrication of fuel cells, it can reduce the cost of the cells, improve their performance and stability, and greatly broaden the commercial application scope of fuel cells.

[0055] The present invention is further illustrated below with specific embodiments:

[0056] Example 1

[0057] This embodiment provides a method for preparing a low-noble-metal heterojunction fuel cell catalyst, including the following steps:

[0058] (1) Preparation of Pt-Co alloy nanoparticles

[0059] Take 20 ml of benzyl alcohol solution containing polyvinylpyrrolidone with a concentration of 10 mg / ml, add 100 mg of benzoic acid, stir well, then add 30 mg of platinum acetylacetonate and 30 mg of cobalt acetylacetonate powder, stir continuously and react at 180 °C for 12 h, centrifuge to collect the product, and wash it with deionized water several times to obtain Pt-Co alloy nanoparticles.

[0060] (2) Prepare a cobalt acetate ethanol solution with a concentration of 10 mg / ml, take 80 mg of the Pt-Co alloy nanoparticles obtained in step (1) and place them in 20 ml of the cobalt acetate ethanol solution, stir continuously for 18 h, and grow a cobalt acetate thin film layer on the outer edge of the surface of the Pt-Co alloy nanoparticles. Then, centrifuge to collect the product and obtain a low-noble metal heterojunction fuel cell catalyst.

[0061] Example 2

[0062] This embodiment provides a method for preparing a low-noble-metal heterojunction fuel cell catalyst, including the following steps:

[0063] (1) Preparation of Pt-Co alloy nanoparticles

[0064] Take 20 ml of benzyl alcohol solution containing polyvinylpyrrolidone with a concentration of 20 mg / ml, add 120 mg of benzoic acid, stir well, then add 50 mg of platinum acetylacetonate and 50 mg of cobalt acetylacetonate powder, stir continuously and react at 200 °C for 24 h, centrifuge to collect the product, and wash it with deionized water several times to obtain Pt-Co alloy nanoparticles.

[0065] (2) Prepare a cobalt acetate ethanol solution with a concentration of 20 mg / ml, take 100 mg of the Pt-Co alloy nanoparticles obtained in step (1) and place them in 20 ml of the cobalt acetate ethanol solution, stir continuously for 24 h, and grow a cobalt acetate thin film layer on the outer edge of the surface of the Pt-Co alloy nanoparticles. Then, centrifuge to collect the product and obtain a low-noble metal heterojunction fuel cell catalyst.

[0066] Example 3

[0067] This embodiment provides a method for preparing a low-noble-metal heterojunction fuel cell catalyst, including the following steps:

[0068] (1) Preparation of Pt-Co alloy nanoparticles

[0069] Take 20 ml of benzyl alcohol solution containing polyvinylpyrrolidone with a concentration of 5 mg / ml, add 60 mg of benzoic acid, stir well, then add 20 mg of platinum acetylacetonate and 20 mg of cobalt acetylacetonate powder, stir continuously and react at 150 °C for 8 h, centrifuge to collect the product, and wash it with deionized water several times to obtain Pt-Co alloy nanoparticles.

[0070] (2) Prepare a cobalt acetate ethanol solution with a concentration of 5 mg / ml, take 50 mg of the Pt-Co alloy nanoparticles obtained in step (1) and place them in 20 ml of the cobalt acetate ethanol solution, stir continuously for 12 h, and grow a cobalt acetate thin film layer on the outer edge of the surface of the Pt-Co alloy nanoparticles. Then, centrifuge to collect the product and obtain a low-noble metal heterojunction fuel cell catalyst.

[0071] The morphology of the low-noble metal heterojunction fuel cell catalysts prepared in Examples 1-3 was observed, and the size range of the low-noble metal heterojunction fuel cell catalysts prepared in Examples 1-3 was measured. The results are shown in Table 1. Figure 1 The image shown is a transmission electron microscope (TEM) image of the low-noble-metal heterojunction fuel cell catalyst prepared in Example 1. Figure 1 It can be seen that the catalyst prepared in the examples has a uniform and narrow particle size distribution, good dispersibility, and no severe agglomeration. This morphology can provide a large number of reactive sites for the oxygen reduction reaction and improve the catalytic reaction efficiency.

[0072] Table 1. Size range of low-noble-metal heterojunction fuel cell catalysts prepared in Examples 1-3

[0073]

[0074] Subsequently, the oxygen reduction activity of the low-noble-metal heterojunction fuel cell catalyst prepared in Example 1 was tested. The test results were obtained by positive sweep in an O2-saturated 0.1M HClO4 solution at a scan rate of 50 mV / s and a rotation speed of 1600 r / min. The results are as follows: Figure 2 As shown. By Figure 2 It is evident that the low-noble-metal heterojunction fuel cell catalyst prepared by this invention has high oxygen reduction activity, which can effectively improve the oxygen reduction reaction kinetics and increase the catalytic reaction efficiency.

[0075] The above description is a preferred embodiment of the invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the invention, and these improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A method for preparing a low-noble-metal heterojunction fuel cell catalyst, characterized in that, Includes the following steps: (1) Preparation of Pt-Co alloy nanoparticles; (2) Prepare a cobalt acetate ethanol solution, place the Pt-Co alloy nanoparticles in the cobalt acetate ethanol solution, stir, and grow a cobalt acetate thin film layer on the outer edge of the surface of the Pt-Co alloy nanoparticles to obtain a low-noble metal heterojunction fuel cell catalyst. In step (1), the preparation of Pt-Co alloy nanoparticles is carried out by the following method: Benzoic acid was added to a benzyl alcohol solution containing polyvinylpyrrolidone, and after stirring until homogeneous, platinum acetylacetonate and cobalt acetylacetonate were added. The mixture was stirred and reacted at a preset temperature to obtain Pt-Co alloy nanoparticles.

2. The preparation method of the low-noble-metal heterojunction fuel cell catalyst as described in claim 1, characterized in that, The ratio by weight of the amount of benzoic acid added to the sum of the amounts of platinum acetylacetonate and cobalt acetylacetonate is (6~12):(4~10). The ratio of the amount of platinum acetylacetonate to cobalt acetylacetonate added is (1~2):(1~2).

3. The preparation method of the low-noble-metal heterojunction fuel cell catalyst as described in claim 1, characterized in that, The amount of benzoic acid added is 60mg~120mg; The amount of platinum acetylacetone added is 20mg~50mg, and the amount of cobalt acetylacetone added is 20mg~50mg; The concentration of the benzyl alcohol solution containing polyvinylpyrrolidone is 5 mg / ml to 20 mg / ml; The amount of benzyl alcohol solution containing polyvinylpyrrolidone added is 18 ml to 25 ml.

4. The preparation method of the low-noble-metal heterojunction fuel cell catalyst as described in claim 1, characterized in that, The preset temperature is 150℃~200℃, and the reaction time is 8h~24h.

5. The method for preparing a low-noble-metal heterojunction fuel cell catalyst as described in claim 1, characterized in that, In step (2), the concentration of the cobalt acetate ethanol solution is 5 mg / ml to 20 mg / ml; The amount of cobalt acetate ethanol solution added is 18 ml to 25 ml, and the amount of Pt-Co alloy nanoparticles added is 50 mg to 100 mg.

6. The method for preparing a low-noble-metal heterojunction fuel cell catalyst as described in claim 1, characterized in that, In step (2), the stirring time is 12h~24h.

7. The method for preparing a low-noble-metal heterojunction fuel cell catalyst as described in claim 1, characterized in that, The particle size of the Pt-Co alloy nanoparticles is 5nm~20nm; The particle size of the low-noble-metal heterojunction fuel cell catalyst is 5nm~20nm.

8. A low-noble-metal heterojunction fuel cell catalyst, characterized in that, It is prepared by the method for preparing a low-noble metal heterojunction fuel cell catalyst as described in any one of claims 1 to 7.

9. The application of a low-noble-metal heterojunction fuel cell catalyst as described in claim 8 in a fuel cell.

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