A preparation method of an Au / Pt nanowire catalyst for ammonia oxidation

Abstract

This invention discloses a method for preparing an Au / Pt nanowire catalyst for ammonia oxidation. The method includes: firstly, dissolving chloroauric acid and 1-naphthol in a mixed solvent of ultrapure water and ethanol to obtain a golden solution; reacting the obtained golden solution under constant temperature conditions, and obtaining a black precipitate after centrifugation and washing; adding the black precipitate to n-hexane for ultrasonic dispersion, centrifuging and washing again, and then adding oleylamine and dodecylamine for ultrasonic treatment to obtain a black solution; adding hexadecyltrimethylammonium chloride, 1,2-butanediol, platinum acetylacetonate, and oleylamine to the black solution, and mixing evenly to obtain a light yellow solution; ultrasonicating the light yellow solution and reacting it under constant temperature conditions, followed by centrifugation and washing to obtain the black precipitate, which is the Au / Pt nanowire catalyst. This catalyst has a one-dimensional chain-like Au-supported structure with uniformly grown Pt-based nanodendrons on its surface, forming a typical epitaxial growth structure. This structure not only has high atomic utilization and excellent structural stability, but also abundant active sites and good electron transfer efficiency, which is beneficial to mass transfer and charge transfer during the ammonia oxidation reaction. The Au / Pt nanowire catalyst prepared by this invention not only has significant ammonia oxidation catalytic performance, but also has good stability, a controllable preparation process, and is easy to prepare on a large scale.

Description

Technical Field

[0001] This invention relates to a method for preparing Au / Pt nanowire catalysts for ammonia oxidation, belonging to the field of novel functional nanomaterials. Background Technology

[0002] Driven by the goals of a hydrogen economy and carbon neutrality, ammonia (NH3), a carbon-free fuel, is considered a highly promising clean energy carrier due to its abundant reserves, safe storage and transportation, and high energy density. It can be directly used as an anode fuel in ammonia fuel cells. The core reaction occurring at the anode with NH3 is the ammonia oxidation reaction (AOR), which involves multiple electron transfers and complex intermediate evolution processes. This slow kinetic reaction rate requires a high overpotential to drive the reaction, a limitation that has become a key bottleneck restricting the large-scale application of ammonia fuel cells. Therefore, developing high-performance electrocatalysts to accelerate AOR kinetics is a current research focus in this field.

[0003] Platinum (Pt)-based materials are widely recognized as the most promising catalysts in ammonia resorption / desorption (AOR) catalysis systems due to their excellent adsorption and activation capabilities for ammonia molecules. However, single-metal Pt catalysts face challenges such as low atom utilization, insufficient active sites, and limited control over the adsorption / desorption free energy of key intermediates, making it difficult to meet practical application requirements in terms of catalytic activity and stability. Therefore, introducing a second metal to construct a bimetallic system has become an important strategy for improving AOR performance. Gold (Au) possesses excellent electrical conductivity, stable physicochemical properties, and good intermetallic interface compatibility. Epitaxially growing Pt on the surface of Au nanowires not only allows for the control of Pt's electronic configuration through a tight two-phase interface, optimizing the adsorption / desorption behavior of reaction intermediates, but also leverages the excellent electrical conductivity of Au nanowires to further enhance catalytic reaction efficiency. However, Au / Pt nanowires prepared by traditional methods are mostly dense structures with small specific surface areas, insufficient exposure of active sites, and hindered mass transfer, making it difficult to fully utilize interfacial synergistic effects. In contrast, dendritic Au / Pt nanowires possess an open morphology, exposing numerous active sites and broadening diffusion channels, effectively compensating for the shortcomings of traditional dense structures. Therefore, there is an urgent need to develop a simple and controllable method for designing and constructing dendritic Au / Pt nanowire catalysts.

[0004] Current methods for preparing Au / Pt nanowire catalysts still suffer from drawbacks such as poor controllability of microstructure and poor AOR performance, making large-scale production difficult. Furthermore, research on Au / Pt nanowire catalysts is limited to a few specific morphologies or compositions. Therefore, novel preparation strategies are needed to construct Au / Pt nanowire catalysts that combine high activity, high stability, and high platinum utilization, providing a new technological pathway for AOR catalysis. Summary of the Invention

[0005] To avoid the shortcomings of the prior art, the present invention provides a method for preparing Au / Pt nanowire catalysts.

[0006] One of the objectives of this invention is to provide a novel Au / Pt nanowire catalyst.

[0007] The second objective of this invention is to provide a two-step seed growth method.

[0008] The third objective of this invention is to provide a catalyst with significantly high AOR catalytic activity.

[0009] The Au / Pt nanowire catalyst prepared in this invention is synthesized from chloroauric acid (HAuCl4), 1-naphthol, n-hexane, oleylamine, dodecylamine, hexadecyltrimethylammonium chloride (CTAC), 1,2-butanediol, and platinum acetylacetonate (Pt(acac)2) via a two-step synthesis method. The preparation process includes the following specific steps: 1. First, dissolve 10-15 mg of HAuCl4 and 70-80 mg of 1-naphthol in 4-5 mL of ultrapure water and 3-4 mL of ethanol to obtain a golden solution. 2. Place the gold solution obtained in step 1 at 70-80 ℃ for 10-12 hours to obtain a light pink solution. Centrifuge at 11000 rpm for 10 minutes using a high-speed centrifuge. Remove the supernatant from the centrifuge tube and wash with water and ethanol several times to obtain a black precipitate. 3. Add 7-9 mL of n-hexane to the black precipitate obtained in step 2, and sonicate to obtain a black solution; 4. Take 0.5-1 mL of the black solution obtained in step 3 and centrifuge it at 10,000 rpm for 5 minutes using a high-speed centrifuge. Remove the supernatant from the centrifuge tube and wash it several times with water and ethanol to obtain the black precipitate. 5. Add 100-200 μL of oleylamine and 200-300 μL of dodecylamine to the black precipitate obtained in step 4, and sonicate for 1-2 hours to obtain a black solution. 6. Add 0.1-0.3 mg of CTAC, 600-700 μL of 1,2-butanediol, 3-6 mg of Pt(acac)2 and 2 mL of oleylamine to the black solution obtained in step 5, and mix well to obtain a light yellow solution. 7. After sonicating the light yellow solution obtained in step 6 for 1-2 hours, place the entire solution system at 130-150 ℃ for 1-2 hours to obtain a black solution; 8. The black solution obtained in step 7 is centrifuged at 10,000 rpm for 5 minutes using a high-speed centrifuge. The supernatant in the centrifuge tube is removed, and the solution is washed with cyclohexane multiple times to obtain a black precipitate, which is the Au / Pt nanowire catalyst.

[0010] The beneficial effects of this invention are: 1. This invention provides a method for preparing Au / Pt nanowire catalysts for ammonia oxidation reaction, characterized by using HAuCl4, 1-naphthol, n-hexane, oleylamine, dodecylamine, CTAC, 1,2-butanediol and Pt(acac)2 as raw materials, and preparing them through a two-step seed growth method. It only requires conventional laboratory equipment and does not require special equipment. The process is controllable and easy to operate. 2. This method provides a novel Au / Pt nanowire catalyst that can be used as a highly efficient electrocatalyst for ammonia oxidation reaction; 3. The Au / Pt nanowire catalyst obtained by this method exhibits performance at 5 mV s⁻¹. -1 Under CV testing, the peak current density was 12.5 mA cm⁻¹. -2 It is significantly higher than that of commercial Pt / C catalysts; 4. The catalyst prepared by this invention has a stable structure, abundant active sites, and good reproducibility in the preparation process. The process route is mature and controllable, and it has the potential for large-scale preparation, making it suitable for subsequent industrial application and promotion. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings will be briefly introduced in the description of the embodiments or the prior art below. However, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 Transmission electron microscope image of the Au / Pt nanowire catalyst prepared in this invention.

[0013] Figure 2 This is a high-resolution transmission electron microscope image of the Au / Pt nanowire catalyst prepared in this invention.

[0014] Figure 3 High-angle annular dark-field transmission electron microscope image and corresponding elemental analysis diagram of the Au / Pt nanowire catalyst prepared for this invention.

[0015] Figure 4 The AOR performance test results are shown for the Au / Pt nanowire catalyst prepared in this invention and the commercial Pt / C catalyst.

[0016] Figure 5The stability test results are shown for the Au / Pt nanowire catalyst prepared in this invention and the commercial Pt / C catalyst. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0019] Unless otherwise specified, the experimental methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials are commercially available.

[0020] Example 1: First, 13 mg of HAuCl4 and 75 mg of 1-naphthol were fully dissolved in 4 mL of ultrapure water and 3.5 mL of ethanol. The entire solution system was reacted at 75 °C for 12 hours to obtain a light pink solution. After centrifugation and washing, a black precipitate was obtained. 8 mL of n-hexane was added to the black precipitate for dispersion treatment to obtain a black solution. 0.75 mL of the black solution was centrifuged, and 150 μL of oleylamine and 250 μL of dodecylamine were added. The mixture was sonicated for 1 hour to obtain a black solution. 0.2 mg of CTAC, 650 μL of 1,2-butanediol, 4 mg of Pt(acac)2 and 2 mL of oleylamine were added to the black solution to obtain a light yellow solution. The entire solution system was sonicated for 1.5 hours and then reacted at 140 °C for 2 hours to obtain a black solution. After centrifugation and washing, a black precipitate was obtained, which is the Au / Pt nanowire catalyst.

[0021] Example 2: First, 10 mg of HAuCl4 and 80 mg of 1-naphthol were fully dissolved in 4.5 mL of ultrapure water and 4 mL of ethanol. The entire solution system was reacted at 80 °C for 10 hours to obtain a light pink solution. After centrifugation and washing, a black precipitate was obtained. 9 mL of n-hexane was added to the black precipitate for dispersion treatment to obtain a black solution. 0.5 mL of the black solution was centrifuged and 100 μL of oleylamine and 300 μL of dodecylamine were added. The mixture was sonicated for 1.5 hours to obtain a black solution. 0.1 mg of CTAC, 600 μL of 1,2-butanediol, 3 mg of Pt(acac)2 and 2 mL of oleylamine were added to the black solution to obtain a light yellow solution. The entire solution system was sonicated for 2 hours and then reacted at 130 °C for 1.5 hours to obtain a black solution. After centrifugation and washing, a black precipitate was obtained, which is the Au / Pt nanowire catalyst.

[0022] Example 3: First, 15 mg of HAuCl4 and 70 mg of 1-naphthol were fully dissolved in 5 mL of ultrapure water and 3 mL of ethanol. The entire solution system was reacted at 70 °C for 11 hours to obtain a light pink solution. After centrifugation and washing, a black precipitate was obtained. 7 mL of n-hexane was added to the black precipitate for dispersion treatment to obtain a black solution. 1 mL of the black solution was centrifuged and 200 μL of oleylamine and 200 μL of dodecylamine were added. The mixture was sonicated for 2 hours to obtain a black solution. 0.3 mg of CTAC, 700 μL of 1,2-butanediol, 6 mg of Pt(acac)2 and 2 mL of oleylamine were added to the black solution to obtain a light yellow solution. The entire solution system was sonicated for 1 hour and then reacted at 150 °C for 1 hour to obtain a black solution. After centrifugation and washing, a black precipitate was obtained, which is the Au / Pt nanowire catalyst.

[0023] Figure 1 Transmission electron microscopy (TEM) image of the Au / Pt nanowire catalyst prepared in Example 1. From Figure 1 It can be seen that the synthesized Au / Pt nanowire catalyst has a clear dendritic structure on its surface, and the whole exhibits a one-dimensional nanowire morphology with uniform structure and good dispersion.

[0024] Figure 2 High-resolution transmission electron microscopy image of the Au / Pt nanowire catalyst prepared in Example 1. From... Figure 2 It can be seen that the lattice fringes of the Au / Pt nanowire catalyst are clear and continuous, indicating that the sample has good crystallinity. The interplanar spacing of the region was measured to be about 0.23 nm, corresponding to the (111) crystal plane of face-centered cubic Pt, which confirms the successful growth of the outer Pt layer, and that the structure is intact and has good crystallinity.

[0025] Figure 3 High-angle annular dark-field transmission electron microscope image and corresponding elemental analysis diagram of the Au / Pt nanowire catalyst prepared in Example 1. Figure 3 It can be seen that Au and Pt elements are distributed in the Au / Pt nanowire catalyst. Notably, most of the Au element is concentrated in the central region, while the Pt element is uniformly distributed throughout the entire nanowire surface.

[0026] Figure 4 The AOR performance test graphs for the Au / Pt nanowire catalysts prepared in Examples 1-3 and the commercial Pt / C catalysts are shown. From... Figure 4 It can be seen that at 5 mV s -1 Under the test conditions, the peak current density of the Au / Pt nanowire catalyst prepared in Example 1 was 12.5 mA cm⁻¹. -2 The AOR performance was significantly higher than that of the Au / Pt nanowire catalysts prepared in Examples 2 and 3 and the commercial Pt / C catalyst, indicating that the Au / Pt nanowire catalyst prepared in Example 1 has excellent AOR performance.

[0027] Figure 5 The graphs show the stability test results of the Au / Pt nanowire catalysts prepared in Examples 1-3 and the commercial Pt / C catalyst. From... Figure 5 It can be seen that, under the constant voltage test condition of 0.7 V, after 500 s, the current density of the Au / Pt nanowire catalyst prepared in Example 1 is still significantly higher than that of the Au / Pt nanowire catalysts prepared in Examples 2 and 3 and the commercial Pt / C catalyst, indicating that the Au / Pt nanowire catalyst prepared in Example 1 has excellent stability.

[0028] Obviously, those skilled in the art can make various modifications and variations to the method for preparing the Au / Pt nanowire catalyst for ammonia oxidation described in this invention without departing from the spirit and scope of this invention. Therefore, if these modifications and variations of this invention fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing an Au / Pt nanowire catalyst for ammonia oxidation, comprising the following steps: First, 10-15 mg of HAuCl4 and 70-80 mg of 1-naphthol were fully dissolved in 4-5 mL of ultrapure water and 3-4 mL of ethanol to obtain a gold solution. The gold solution was reacted at 70-80 °C for 10-12 hours, and after centrifugation and washing, a black precipitate was obtained. The black precipitate was added to 7-9 mL of n-hexane and ultrasonically dispersed. After centrifugation and washing, 100-200 μL of oleylamine and 200-300 μL of dodecylamine were added and ultrasonically treated to obtain a black solution. Add 0.1-0.3 mg of CTAC, 600-700 μL of 1,2-butanediol, 3-6 mg of Pt(acac)2 and 2 mL of oleylamine to a black solution, mix well to obtain a light yellow solution; after sonicating the light yellow solution, react it at 130-150 ℃ for 1-2 hours, and then centrifuge and wash to obtain a black precipitate, which is the Au / Pt nanowire catalyst.

2. The method for preparing the Au / Pt nanowire catalyst according to claim 1, characterized in that, The dosage of HAuCl4 was 13 mg, the dosage of 1-naphthol was 75 mg, and the dosage of n-hexane was 8 mL.

3. The method for preparing the Au / Pt nanowire catalyst according to claim 1, characterized in that, The dosage of oleylamine was 150 μL, the dosage of dodecylamine was 250 μL, the dosage of CTAC was 0.2 mg, the dosage of 1,2-butanediol was 650 μL, and the dosage of Pt(acac)2 was 4 mg.

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