A method for preparing a low platinum content silver platinum monoatomic surface catalyst

Abstract

The present application belongs to the field of advanced material technology, and relates to the preparation of metal catalysts, and relates to a preparation method of a low-platinum-content silver-platinum monatomic surface catalyst. Platinum and silver are prepared into a uniformly dispersed silver-platinum alloy, and the obtained silver-platinum alloy is subjected to heat treatment under the condition of an atmosphere containing carbon monoxide, and after cooling, the low-platinum-content silver-platinum monatomic surface catalyst is obtained. The present application can form a more strongly reactive monatomic catalytic site on the surface of a silver substrate, can not only reduce the use amount of platinum, but also can realize the improvement of reactivity while maintaining high selectivity.

Description

Technical Field

[0001] This invention belongs to the field of advanced materials technology, and relates to the preparation of metal catalysts, specifically a method for preparing a low-platinum-content silver-platinum single-atom surface catalyst. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] Platinum-based catalysts are among the most widely used metal catalysts, exhibiting excellent performance in catalytic reactions such as oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and hydrogen oxidation reaction (HOR). However, the high price of platinum itself significantly increases the cost of catalysis; therefore, it is necessary to minimize the amount of platinum used without reducing catalytic activity. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing a low-platinum-content silver-platinum single-atom surface catalyst. This invention can form more reactive single-atom catalytic sites on the surface of a silver substrate, which not only reduces the amount of platinum used, but also improves reactivity while maintaining high selectivity.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] On the one hand, a method for preparing a low-platinum-content silver-platinum single-atom surface catalyst involves preparing a uniformly dispersed silver-platinum alloy from platinum and silver, heat-treating the obtained silver-platinum alloy under an atmosphere containing carbon monoxide, and then cooling it to obtain the final product.

[0007] This invention first selects silver and platinum to form an alloy catalyst, which can reduce the amount of platinum used to a certain extent. At the same time, by heat-treating the silver-platinum alloy with CO, platinum can form a surface single-atom alloy with excellent dispersion on the silver matrix, thereby greatly reducing the amount of platinum used. In addition, the formation of platinum atoms in single-atom form on the silver matrix surface can greatly increase its catalytic performance, thereby improving reactivity.

[0008] On the other hand, a low-platinum-content silver-platinum single-atom surface catalyst was obtained by the above preparation method.

[0009] Thirdly, the application of the aforementioned low-platinum-content silver-platinum single-atom surface catalyst in the catalytic oxygen reduction reaction.

[0010] The beneficial effects of this invention are as follows:

[0011] 1. This invention can reduce the amount of platinum used to a certain extent by selecting a silver matrix to form a silver-platinum bialloy, and by using CO heat treatment, it is possible to form single-atom catalytic sites with stronger reactivity on the surface of the silver matrix, which may achieve the goal of improving reactivity while maintaining high selectivity.

[0012] 2. Studies have shown that the overpotential of the low-platinum-content silver-platinum single-atom surface catalyst prepared by this invention is lower than that of pure platinum, which fully demonstrates that the catalyst prepared by this invention has higher reactivity than pure platinum. Attached Figure Description

[0013] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0014] Figure 1 The diagram shows the silver-platinum dual alloy single-atom catalyst prepared in Example 1 of this invention and its reaction activity. A is a schematic diagram of the structure, and B is a reaction activity diagram.

[0015] Figure 2 CO-FTIR experimental characterization of the silver-platinum dual alloy single-atom catalyst prepared in Example 1 of this invention;

[0016] Figure 3 The results of the linear sweep voltammetry test of the silver-platinum dual alloy single-atom catalyst prepared in Example 1 of this invention are shown.

[0017] Figure 4 This is a schematic diagram of the structure of the silver-platinum dual alloy single-atom catalyst prepared in Example 3 of the present invention;

[0018] Figure 5 This is a schematic diagram of the structure of the silver-platinum dual-alloy single-atom catalyst prepared in Example 6 of the present invention; Detailed Implementation

[0019] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0020] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0021] As described in the background section, existing technologies suffer from problems such as extremely high cost of platinum catalysts. To address these technical issues, this invention proposes a method for preparing a low-platinum-content silver-platinum single-atom surface catalyst.

[0022] A typical embodiment of the present invention provides a method for preparing a low-platinum-content silver-platinum single-atom surface catalyst, wherein platinum and silver are prepared into a uniformly dispersed silver-platinum alloy, and the obtained silver-platinum alloy is heat-treated under an atmosphere containing carbon monoxide, and then cooled to obtain the catalyst.

[0023] This invention first selects silver and platinum to form an alloy catalyst, which can reduce the amount of platinum used to a certain extent. At the same time, by heat-treating the silver-platinum alloy with CO, platinum can form a surface single-atom alloy with excellent dispersion on the silver matrix, thereby greatly reducing the amount of platinum used. In addition, the formation of platinum atoms in single-atom form on the silver matrix surface can greatly increase its catalytic performance, thereby improving reactivity.

[0024] In some embodiments, the atomic percentage of platinum in the silver-platinum alloy is 1–15%. The catalytic performance is better when the atomic percentage of platinum in the silver-platinum alloy is 7–9%.

[0025] In some embodiments, the silver-platinum alloy is porous, thin-film, bulk, or granular.

[0026] In some embodiments, the silver-platinum alloy is prepared by chemical methods or physical melting.

[0027] In some embodiments, the prepared silver-platinum alloy is heat-treated in an atmosphere containing carbon monoxide after surface impurities are removed.

[0028] In one or more embodiments, the method for removing surface impurities involves immersing the surface in hydrochloric acid, followed by washing with water and drying. This method is more effective at removing impurities from the surface of the silver-platinum alloy. Specifically, the immersion time is 5–15 minutes; ultrasonic treatment is performed during the water washing process.

[0029] In some embodiments, the carbon monoxide volume concentration in the atmosphere is greater than 50%. The heat treatment effect is better when the carbon monoxide volume concentration is greater than 50% compared to when it is less than 50%.

[0030] In some embodiments, the heat treatment temperature is 700–1000 K. The heat treatment time is 2–10 h.

[0031] Cooling methods can include air cooling, furnace cooling, water cooling, etc. In some embodiments, water cooling to room temperature is performed after heat treatment. Catalysts obtained by this method have better performance.

[0032] Another embodiment of the present invention provides a low-platinum-content silver-platinum single-atom surface catalyst, obtained by the above preparation method.

[0033] A third embodiment of the present invention provides an application of the above-mentioned low-platinum-content silver-platinum single-atom surface catalyst in catalytic oxygen reduction reaction.

[0034] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0035] Example 1

[0036] A method for preparing a low-platinum-content silver-platinum single-atom surface catalyst, comprising the following steps:

[0037] (1) A uniformly dispersed silver-platinum alloy was prepared by mixing platinum (8% atomic percentage) with silver in a certain proportion. The preparation method was a chemical method, the process of which was as follows: silver nanoparticles were dispersed in n-hexane. After mixing and standing for 15 minutes, an H2PtCl6 precursor solution (0.4 mg / mL) was injected into the reaction mixture. -1 Electrochemical displacement of Pt was performed to obtain the desired silver-platinum molar ratio, the reaction was carried out for 15 minutes and then cooled. The solid catalyst was collected under vacuum filtration, washed with excess water, and dried in an oven at 80°C for 1 hour to remove residual water.

[0038] (2) The silver-platinum alloy prepared in step (1) is added to 8 mol / L dilute hydrochloric acid and soaked for 10 minutes, ultrasonically cleaned three times with deionized water, and thoroughly dried at 60℃ for 3 hours.

[0039] (3) Place the silver-platinum alloy processed in step (2) into a quartz tube and pass argon gas through it for ten minutes. Then pass carbon monoxide gas through it until the carbon monoxide concentration in the tube reaches 80%. Seal the quartz tube.

[0040] (4) The quartz tube is heat-treated at 700℃ for 3 hours. After the heat treatment, the quartz tube is immersed in water and cooled to room temperature. The resulting silver-platinum alloy is the target low-platinum-content silver-platinum bi-alloy single-atom catalyst.

[0041] The low-platinum-content silver-platinum dual-alloy single-atom catalyst prepared in this embodiment, such as Figure 1 As shown in Figure A, a well-dispersed surface monoatomic alloy is formed on the surface, with the vast majority of platinum atoms in the bulk phase migrating to the surface after post-treatment. The majority of platinum atoms on the surface exist in monoatomic form, with only a small portion existing in diatomic or triatomic forms. No further platinum segregation was observed, and the number of surface monoatoms almost reaches the theoretical maximum. Figure 1Based on the structure of A, first-principles calculations and simulations were performed. Taking the oxygen reduction reaction (ORR) as an example, the reaction activity of the catalyst prepared in this embodiment is shown in the following reaction equation:

[0042] O2+*+(H + +e - →*OOH

[0043] *OOH+(H + +e - → O + H₂O

[0044] *O+(H + +e - )→*OH

[0045] *OH+(H + +e - → *+H2O

[0046] The results are as follows Figure 1 As shown in Figure B, the study indicates that its overpotential is 0.41V, which is lower than that of pure platinum (0.43V), fully demonstrating that its reactivity is higher than that of pure platinum. Simulated two-electron catalysis (product is hydrogen peroxide) (the reactants are both oxygen, but the products are different, used for comparison to study catalyst selectivity), the adsorption energy of its -OOH functional group indicates that a two-electron reaction is essentially impossible, meaning that this catalyst has good selectivity. The specific steps of the catalytic experiment are as follows:

[0047] 5 μL of catalyst ink was dropped onto the polished working electrode of the rotating ring disk electrode and then dried in air. A solution containing 0.1 mol L⁻¹ KOH was used as the electrolyte. The electrolyte solution was purged with O₂ for at least 30 minutes before electrochemical testing.

[0048] The finished product was characterized by CO-FTIR, and the results are as follows: Figure 2 As shown, this fully demonstrates the formation of single-atom alloys on its surface. Figure 2 The results show that when carbon monoxide is introduced into the sample (for 10 minutes), a peak in the single-atom region is clearly visible (the blue area represents the region where CO is adsorbed on platinum single atoms). This fully demonstrates that the sample surface contains a large number of platinum single atoms. The silver-platinum dual-alloy single-atom catalyst can be successfully prepared using the above method.

[0049] The catalytic performance of this catalyst was characterized electrochemically. Linear sweep voltammetry clearly showed that its half-wave potential was 0.83 V, slightly higher than that of commercial platinum-carbon catalysts (0.8 V). Figure 3 As shown, this catalyst exhibits excellent catalytic performance and has practical potential.

[0050] Example 2

[0051] This embodiment is the same as Embodiment 1, except that in step (1), a physical melting method is used to prepare the silver-platinum bialloy. The process is as follows:

[0052] Aluminum, silver, and platinum were melted in a medium-frequency furnace at a ratio of 90:9:1. After melting, the mixture was kept cool for 5 minutes, then reheated until melted and kept cool for another 5 minutes. This process was repeated three times. The cooled alloy was then placed in a saturated sodium hydroxide solution until no more bubbles appeared. After ultrasonic cleaning three times with deionized water, the alloy was thoroughly dried at 60 degrees Celsius for 3 hours to obtain a 10% platinum silver-platinum bialloy powder.

[0053] Example 3

[0054] This embodiment is the same as Embodiment 1, except that in step (1), the atomic percentage of platinum is 3%. When the atomic percentage of platinum is less than the optimal ratio of 8%, studies have shown that platinum single atoms will still form on the catalyst surface, but the number of single atoms is much less than 8%. Figure 4 With a surface structure of 3%, the number of platinum single atoms on the surface decreases by about 60 percent compared to the optimal ratio of 8%.

[0055] Example 4

[0056] This embodiment is the same as Example 1, except that in step (1), the atomic percentage of platinum is 15%. Studies have shown that increasing the proportion of platinum atoms reduces the number of single platinum atoms on the surface to a certain extent, forming more platinum dimers / polymers, which reduces the reactivity of the catalyst to some extent.

[0057] Example 5

[0058] This embodiment is the same as that of embodiment 1, except that in step (3), the carbon monoxide concentration is 90% and the time is 1.5 hours.

[0059] Example 6

[0060] This embodiment is the same as that in embodiment 1, except that in step (3), the carbon monoxide concentration is 70% and the time is 5 hours.

[0061] Studies have shown that if the carbon monoxide concentration is less than 50%, the number of platinum single atoms on the surface will decrease significantly. Taking Example 1 as an example, when the carbon monoxide concentration in the heat treatment atmosphere is 25%, the number of platinum single atoms on the surface decreases by about 36%, and its surface structure is as follows. Figure 5 .

[0062] Example 7

[0063] This embodiment is the same as Embodiment 1, except that in step (3), the carbon monoxide concentration is 60% and the time is 10 hours. Studies of Embodiments 1, 5, 6, and 7 show that the lower the carbon monoxide concentration, the longer the heat treatment time is required to achieve the same effect.

[0064] Example 8

[0065] This embodiment is the same as Embodiment 1, except that in step (4), the heat treatment temperature is 500℃ and the time is 10 hours. Studies have shown that the lower the heat treatment temperature, the longer it takes to achieve the desired effect.

[0066] Example 9

[0067] This embodiment is the same as embodiment 1, except that in step (4), water cooling is replaced by air cooling.

[0068] Replacing water cooling with air cooling significantly reduces the cooling rate, which in turn reduces the number of platinum single atoms on the surface, resulting in fewer catalytic sites and consequently lower catalytic performance.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. The application of a low-platinum-content silver-platinum single-atom surface catalyst in catalytic oxygen reduction reaction; the preparation method of the low-platinum-content silver-platinum single-atom surface catalyst is to prepare a uniformly dispersed silver-platinum alloy by preparing platinum and silver, and heat-treating the obtained silver-platinum alloy under an atmosphere containing carbon monoxide, and then cooling it to obtain the catalyst. In an atmosphere containing carbon monoxide, the volume concentration of carbon monoxide is greater than 50%; the heat treatment temperature is 700~1000 K, and the heat treatment time is 2~10 h; after heat treatment, the mixture is cooled to room temperature by water. The atomic percentage of platinum in silver-platinum alloys is 7-9%.

2. The application of the low platinum content silver-platinum single-atom surface catalyst as described in claim 1 in the catalytic oxygen reduction reaction, characterized in that the silver-platinum alloy is porous, thin film, bulk or granular.

3. Use of a low platinum content silver platinum monoatomic surface catalyst according to claim 1 for catalyzing oxygen reduction reactions, characterized in that, The silver-platinum alloy can be prepared by chemical methods or physical melting.

4. The application of the low-platinum-content silver-platinum single-atom surface catalyst as described in claim 1 in the catalytic oxygen reduction reaction, characterized in that, After removing surface impurities, the prepared silver-platinum alloy was heat-treated in an atmosphere containing carbon monoxide.

5. The application of the low-platinum-content silver-platinum single-atom surface catalyst as described in claim 4 in the catalytic oxygen reduction reaction, characterized in that, The method to remove surface impurities is to soak in hydrochloric acid, then wash with water and dry.

6. The application of the low-platinum-content silver-platinum single-atom surface catalyst as described in claim 5 in the catalytic oxygen reduction reaction, characterized in that, Soaking time is 5-15 minutes.

7. The application of the low-platinum-content silver-platinum single-atom surface catalyst as described in claim 5 in the catalytic oxygen reduction reaction, characterized in that, Ultrasonic treatment is performed during the water washing process.

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