Preparation and application of AuPt ultrafine nanowires and catalysts thereof

Abstract

The application belongs to the technical field of nanometer synthesis and methanol electro-oxidation, and discloses a preparation and application of AuPt ultrafine nanowires and catalysts thereof. The obtained Au or AuPt alloy ultrafine nanowires have an ultrafine one-dimensional structure, and the diameter of the nanowires is 1-3 nm. In addition, the Au / C catalyst or the AuPt / C catalyst can be constructed based on the Au or AuPt alloy ultrafine nanowires. The size and morphology of the nanowires are improved, the diameter of the obtained Au nanowires and AuPt nanowires is 1-3 nm, and the size is ultrafine. Moreover, the AuPt alloy nanowires obtained based on the application have an ultrafine size, high activity and high stability in the alkaline methanol oxidation, are obviously superior to the existing commercial Pt / C catalyst, have good catalytic activity in the methanol electro-oxidation reaction, and have great application potential.

Description

Technical Field

[0001] This invention belongs to the technical fields of nanosynthesis and methanol electro-oxidation. More specifically, it relates to the preparation and application of AuPt ultrafine nanowires and their catalysts. The obtained AuPt ultrafine nanowires can be used to construct AuPt / C materials, and are particularly useful in methanol electro-oxidation. Background Technology

[0002] With the large-scale development of the global economy, human demand for energy is increasing, and pollutants such as SO2, NO2, and dust generated by the combustion of fossil fuels are causing serious damage to the environment. At the same time, the low efficiency of energy utilization methods such as internal combustion engines leads to a large amount of energy waste. Compared with other fuel cell technologies, methanol fuel cells have advantages such as simple fuel handling, low heat signal, and environmental friendliness. They support applications in various fields such as marine vessels, portable electronic devices, and mobile applications (such as electric vehicles). However, the low activity and low stability of the methanol electro-oxidation reaction at the anode limit its development. Currently, the catalyst for the commercially applied methanol oxidation reaction is Pt / C, but this catalyst has low stability due to the poisoning effect of CO intermediates generated by methanol oxidation. At the same time, since the (111) crystal face of the Pt catalyst is a highly active crystal face, conventional nanoparticles cannot fully expose this active crystal face. Currently, the preparation of AuPt ultrafine nanowire catalysts that mainly expose the (111) active crystal face and have high methanol oxidation stability has not been reported.

[0003] Chinese patent CN109848434A discloses a method for preparing ultrafine platinum nanowires rich in twin defects, but it mainly consists of Pt and transition metal alloy nanowires, and its synthesis method cannot be used to synthesize Au-based ultrafine nanowires. Summary of the Invention

[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide a method for preparing and applying AuPt ultrafine nanowires and their catalysts. By improving the size and morphology of the nanowires, Au and AuPt nanowires with diameters of 1–3 nm are obtained, exhibiting ultrafine dimensions. In particular, the Au or AuPt ultrafine nanowires obtained in this invention can be synthesized rapidly using specific methods. Furthermore, the AuPt alloy nanowires obtained based on this invention, in addition to their ultrafine size, exhibit high activity and high stability in alkaline methanol oxidation, significantly outperforming existing commercial Pt / C catalysts. They also demonstrate excellent catalytic activity in the electro-oxidation of methanol, showing great application potential.

[0005] To achieve the above objectives, according to one aspect of the present invention, an Au or AuPt alloy ultrafine nanowire is provided, characterized in that it has an ultrafine one-dimensional structure and the diameter of the nanowire is 1 to 3 nm.

[0006] As a further preferred embodiment of the present invention, the ultrafine nanowires are AuPt alloy ultrafine nanowires, wherein the atomic percentage content of Au element is greater than or equal to 40% and less than 100%.

[0007] The atomic percentage of Pt is greater than 0 and less than or equal to 60%.

[0008] Preferably, among the exposed crystal planes of the Au or AuPt alloy ultrafine nanowires, the main exposed crystal plane is the (111) plane;

[0009] Pt atoms are uniformly distributed in the ultrafine nanowires.

[0010] According to another aspect of the present invention, the present invention provides a method for preparing the above-mentioned Au or AuPt alloy ultrafine nanowires, characterized by comprising the following steps:

[0011] (1) According to the metal element composition of the target ultrafine nanowire, the corresponding metal salt is added to the oleylamine solution and ultrasonically treated to obtain a mixed solution; wherein, when the target ultrafine nanowire is Au ultrafine nanowire, the metal salt is gold chloride; when the target ultrafine nanowire is AuPt alloy ultrafine nanowire, the metal salt includes platinum acetylacetonate and gold chloride.

[0012] (2) After adding carbonyl molybdenum or carbonyl tungsten to the mixed solution, ultrasonic treatment is performed;

[0013] (3) Add borane-tert-butylamine and / or continuously pass hydrogen gas into the mixed solution obtained in step (2) and heat to carry out the reaction; after the reaction, wash and centrifuge the obtained solution to obtain Au ultrafine nanowires or AuPt alloy ultrafine nanowires.

[0014] As a further preferred embodiment of the present invention, in step (1), the concentration of the mixed solution satisfies:

[0015] For every 4.5–5.5 mL of oleylamine solution, the corresponding amount of gold trichloride added is 3–7.5 mg; and for every 4.5–5.5 mL of oleylamine solution, the corresponding amount of acetylacetone platinum added is 0–6 mg.

[0016] In step (2), the amount of carbonyl molybdenum or carbonyl tungsten added satisfies the following:

[0017] The amount of molybdenum carbonyl added per 4.5–5.5 mL of oleylamine solution is 9–11 mg; or the amount of tungsten carbonyl added per 4.5–5.5 mL of oleylamine solution is 12–14.6 mg.

[0018] Specifically, step (3) involves adding borane-tert-butylamine to the mixed solution obtained in step (2) and then heating it to carry out the reaction; wherein the amount of borane-tert-butylamine added satisfies the following condition: for every 4.5 to 5.5 mL of oleylamine solution, the amount of borane-tert-butylamine added is 9 to 11 mg.

[0019] Alternatively, step (3) specifically involves continuously introducing hydrogen gas into the mixed solution obtained in step (2) and then heating it to carry out the reaction; wherein the flow rate of the hydrogen gas introduced satisfies the following: the amount of hydrogen gas introduced per 4.5 to 5.5 mL of oleylamine solution is 20 to 40 mL / min.

[0020] As a further preferred embodiment of the present invention, in step (3), the reaction temperature for heating the reaction is 170-190°C, preferably 180°C; and the reaction time is 1.5h-2.5h, preferably 2h.

[0021] As a further preferred embodiment of the present invention, in both steps (1) and (2), the ultrasonic treatment time is 0.1 to 0.3 hours.

[0022] In step (3), the centrifugation speed is 4000-6000 rpm, preferably 4000 rpm; the centrifugation time is 2-3 min, preferably 2 min.

[0023] The washing process specifically involves ultrasonic washing, using hexane or acetone as the solvent, and the ultrasonic washing time is 2–3 minutes.

[0024] According to another aspect of the present invention, the present invention provides an Au / C catalyst or AuPt / C catalyst based on the above-mentioned Au or AuPt alloy ultrafine nanowires, characterized in that the Au / C catalyst or AuPt / C catalyst is formed by loading the above-mentioned Au or AuPt alloy ultrafine nanowires onto the surface of a carbon material.

[0025] Preferably, the Au or AuPt alloy ultrafine nanowires account for 18-23% of the total mass fraction of the Au / C catalyst or AuPt / C catalyst; the carbon material is carbon black.

[0026] According to another aspect of the present invention, the present invention provides a method for preparing the above-mentioned Au / C catalyst or AuPt / C catalyst, characterized in that a hexane solution containing Au ultrafine nanowires is injected into an ethanol solution of carbon black, ultrasonically loaded, and then centrifuged and dried to obtain the Au / C catalyst.

[0027] Alternatively, a hexane solution containing AuPt alloy ultrafine nanowires can be injected into an ethanol solution of carbon black, ultrasonically loaded, and then centrifuged and dried to obtain the AuPt / C catalyst.

[0028] As a further preferred embodiment of the present invention, the ultrasonic loading time is 0.5 to 2 hours, preferably 1 hour;

[0029] The centrifugation speed is 8000-9000 rpm, preferably 9000 rpm; the centrifugation time is 7-10 min, preferably 8 min;

[0030] The drying process is carried out by baking, with a baking temperature of 60-80 degrees Celsius.

[0031] According to the last aspect of the present invention, the present invention provides the application of the above-mentioned AuPt alloy ultrafine nanowires or the above-mentioned AuPt / C catalyst in the electro-oxidation of methanol at the anode of a methanol fuel cell;

[0032] Preferably, the methanol fuel cell is an alkaline methanol fuel cell.

[0033] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following results.

[0034] Beneficial effects:

[0035] (1) The Au ultrafine nanowires and AuPt ultrafine nanowires in this invention have a diameter of 1-3 nm and feature an ultrafine one-dimensional structure. Taking the AuPt alloy ultrafine nanowire as an example, Pt is uniformly doped into the Au nanowire, which greatly improves the atomic utilization rate. At the same time, the AuPt one-dimensional nanowire exposes more specific active crystal planes (111), as described later. Figure 3 As shown in the example, 2θ = 38.8° is the most dominant peak in the XRD pattern (that is, the main exposed crystal plane in Au or AuPt alloy ultrafine nanowires is the (111) plane; considering different Au:Pt ratios, the 2θ position of the XRD diffraction peak corresponding to the (111) plane often fluctuates to some extent. The larger the proportion of Au element, the closer the XRD diffraction peak corresponding to the (111) plane is to the (111) peak of pure Au, that is, 2θ = 38.2°; the larger the proportion of Pt element, the closer the (111) plane is to the (111) peak of pure Au, that is, 2θ = 38.2°; the larger the proportion of Pt element, the closer the (111) plane is to the (111) peak of pure Au, that is, 2θ = 38.2°. The closer the XRD diffraction peak corresponding to the (111) plane is to the (111) peak of pure Pt, that is, 2θ = 39.7°; that is, when the atomic percentage of Au is greater than or equal to 40% and less than or equal to 100%, the 2θ of the XRD diffraction peak corresponding to the (111) plane is in the range of 38.2° to 39.7°; at the same time, based on the high dispersion of Pt in Au and the interaction between the two, the AuPt / C catalyst has high activity and stability in the alkaline methanol electro-oxidation reaction.

[0036] (2) In particular, this invention involves first adding platinum acetylacetonate and gold chloride to an oleylamine solution to obtain a mixed solution, then adding molybdenum carbonyl or tungsten carbonyl, followed by adding borane-tert-butylamine to the mixed solution or continuously bubbling hydrogen gas and heating to carry out the reaction, thereby generating ultrafine nanowires. This invention utilizes this specific preparation method to rapidly synthesize Au ultrafine nanowires and AuPt alloy ultrafine nanowires.

[0037] (3) The AuPt ultrafine nanowires obtained in this invention, and the AuPt / C catalyst constructed based on these AuPt ultrafine nanowires, have broad application potential in the methanol electro-oxidation reaction at the anode of methanol fuel cells. Taking the examples below, the AuPt / C catalyst obtained in this invention and the commercially available Pt / C catalyst were compared experimentally in alkaline methanol electro-oxidation. The results showed that the mass activity (activity provided per unit mass of Pt) of the AuPt / C catalyst of this invention was 65 mA / mg. Pt The Pt / C mass activity of commercial catalysts is 19 mA / mg. Pt The activity of the catalyst is 3.4 times that of methanol fuel cells, with a mass activity increased by approximately 240% and stability significantly improved. Therefore, this invention has broad application prospects in the field of methanol fuel cell catalysis technology.

[0038] Au and Pt are easily reduced, and during synthesis, they tend to grow into nanoparticles in various directions, thus failing to fully expose specific crystal planes. There are reports of Au-based nanowires synthesized hydrothermally, but these exhibit poor dispersibility in polar solvents, leading to agglomeration and poor overall dispersion. This invention utilizes an organic phase synthesis strategy, employing the co-reduction of CO generated from carbonyl groups with hydrogen (hydrogen can be generated either directly or by adding borane-tert-butylamine to the reaction system; heating borane-tert-butylamine releases hydrogen), causing it to adsorb onto specific crystal planes of the seed crystals, thereby growing well-dispersed AuPt alloy nanowires along the (111) plane. Attached Figure Description

[0039] Figure 1 This is a transmission electron microscope image of the AuPt ultrafine nanowires in Example 2 of the present invention.

[0040] Figure 2 This is a transmission electron microscope image of the AuPt / C catalyst in Example 4 of the present invention.

[0041] Figure 3 This is the X-ray diffraction pattern of the AuPt / C catalyst in Example 4 of the present invention.

[0042] Figure 4 This is the cyclic voltammetric scan curve (first lap) of the Au / C catalyst in Example 3 of the present invention in a 1 mol / L KOH + 0.1 mol / L methanol solution.

[0043] Figure 5 The first loop shows the linear voltammetric scan curves (first loop) of the AuPt / C catalyst and the commercial Pt / C catalyst in 1 mol / L KOH + 0.1 mol / L methanol solution in Example 4 of this invention.

[0044] Figure 6 This is a comparison of the cyclic voltammetric scan curves of the AuPt / C catalyst in Example 4 of the present invention after the first and 2000th cycles.

[0045] Figure 7 This is a comparison of the cyclic voltammetric scan curves of a commercial Pt / C catalyst after the first and 2000th cycles.

[0046] Figure 8 This is an elemental distribution diagram of the AuPt nanowires in Embodiment 2 of the present invention obtained using a high-resolution transmission electron microscope.

[0047] Figure 9 This is a transmission electron microscope image of the AuPt nanowires in Example 5 of this invention. Detailed Implementation

[0048] 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. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0049] In the embodiments of this invention, all raw materials were purchased commercially and used directly without processing; the testing conditions of the instruments all adopted the parameters recommended by the manufacturer.

[0050] In the examples, all drugs were purchased from Innovent Biologics.

[0051] In the examples, the samples were characterized using X-ray diffraction (XRD) analysis with a DMAX-2400X.

[0052] In the examples, the transmission electron microscope (TEM) images of the samples were characterized using a FEI Tecani G2 20.

[0053] In the examples, the polarization curves and cyclic voltammetry curves of the samples were obtained by an electrochemical workstation (CHI760E) from Shanghai Chenhua Co., Ltd.

[0054] Regardless of whether it is the ultrafine Au nanowire or the ultrafine AuPt nanowire in this invention, their preparation can be carried out as follows: Platinum acetylacetonate and gold chloride are added to an oleylamine solution and ultrasonically treated to obtain a mixed solution (wherein, platinum acetylacetonate is optional; that is, it is only required when the target ultrafine nanowire is an AuPt alloy ultrafine nanowire); molybdenum carbonyl or tungsten carbonyl is added to the mixed solution and ultrasonically treated; borane-tert-butylamine is added to the mixed solution or hydrogen gas is continuously introduced, and the temperature is raised to carry out the reaction; then the resulting solution is washed and centrifuged to obtain the ultrafine nanowire.

[0055] The mass-to-volume ratio (mg / mL) of platinum acetylacetonate to oleylamine can be 0–6 mg: 4.5–5.5 mL (when the amount of platinum acetylacetonate is 0, ultrafine Au nanowires are obtained accordingly), the mass-to-volume ratio (mg / mL) of gold trichloride to oleylamine can be 3–7.5 mg: 4.5–5.5 mL, the mass-to-volume ratio (mg / mL) of molybdenum carbonyl to oleylamine can be 9–11 mg: 4.5–5.5 mL, or the mass-to-volume ratio (mg / mL) of tungsten carbonyl to oleylamine can be used. The ratio can be 12–14.6 mg: 4.5–5.5 mL; for the method of adding borane-tert-butylamine without introducing hydrogen gas, the mass-volume ratio (mg / mL) of borane-tert-butylamine to oleylamine can be 9–11 mg: 4.5–5.5 mL; for the method of continuously introducing hydrogen gas without adding borane-tert-butylamine, the hydrogen gas flow rate can be 20–40 mL / min per 4.5–5.5 mL of oleylamine (when the amount of oleylamine in the system changes proportionally, the hydrogen gas flow rate also changes proportionally).

[0056] Washing and centrifugation can be performed as follows: after the material has been cooled to room temperature, centrifuge it (e.g., differential centrifugation), and then ultrasonically wash the product obtained by centrifugation with n-hexane (acetone can also be used). Then, repeat the above centrifugation and ultrasonic washing three times.

[0057] The following are specific examples:

[0058] Example 1

[0059] This invention provides a method for preparing ultrafine Au nanowires. Gold trichloride is added to an oleylamine solution and sonicated to obtain a mixed solution, wherein the amount of gold trichloride is 7.5 mg and the amount of oleylamine is 5 mL. Then, 10 mg of molybdenum carbonyl is added to the mixed solution and sonicated again. Subsequently, 10 mg of borane-tert-butylamine is added to the mixed solution, and after ultrasonic mixing, the mixture is heated to 180 degrees Celsius and reacted for 1 h. The cooled mixed solution is then washed with n-hexane, and this process is repeated three times by differential centrifugation at 5000 rpm to obtain ultrafine Au nanowires.

[0060] Example 2

[0061] This invention provides a method for preparing ultrafine AuPt alloy nanowires. Acetylacetonate platinum and gold trichloride are added to an oleylamine solution and ultrasonically treated to obtain a mixed solution. The amount of acetylacetonate platinum is 2 mg, the amount of gold trichloride is 6 mg, and the amount of oleylamine is 5 mL. Then, 10 mg of molybdenum carbonyl is added to the mixed solution and ultrasonically treated. Subsequently, 10 mg of borane-tert-butylamine is added to the mixed solution, and after ultrasonic mixing, the solution is heated to 180 degrees Celsius and reacted for 1 h. The cooled mixed solution is then washed with n-hexane, and this process is repeated three times under differential centrifugation at 5000 rpm to obtain ultrafine AuPt nanowires.

[0062] Example 3

[0063] This invention provides a method for preparing an Au / C catalyst. Following the method described in Example 1, Au ultrafine nanowires were dispersed in n-hexane, wherein the amount of Au ultrafine nanowires was 4 mg and the amount of n-hexane was 5 mL. Then, the dispersion was slowly added dropwise to 20 mL of an ethanol dispersion of carbon black (the mass of the carbon black in the ethanol dispersion was 12 mg), ultrasonically loaded for 1 h, then centrifuged at 9000 rpm for 10 min, and subsequently dried at 60 °C for 5 h to obtain the Au / C catalyst. ICP-MS analysis of the product showed that the mass fraction of Au was 20%.

[0064] Example 4

[0065] This invention provides a method for preparing an AuPt / C catalyst. Following the method in Example 2, AuPt ultrafine nanowires were dispersed in n-hexane, wherein the amount of AuPt ultrafine nanowires was 4 mg and the amount of n-hexane was 5 mL. Then, the dispersion was slowly added dropwise to 20 mL of an ethanol dispersion of carbon black (the mass of the carbon black in the ethanol dispersion was 12 mg), ultrasonically loaded for 1 h, then centrifuged at 9000 rpm for 10 min, and subsequently dried at 60 °C for 5 h to obtain the AuPt / C catalyst. ICP-MS analysis of the product showed that the mass fraction of AuPt alloy was 20%.

[0066] Example 5

[0067] This invention provides a method for preparing ultrafine AuPt alloy nanowires. Platinum acetylacetonate and gold trichloride are added to an oleylamine solution and ultrasonically treated to obtain a mixed solution. The amount of platinum acetylacetonate is 2 mg, the amount of gold trichloride is 6 mg, and the amount of oleylamine is 5 mL. Then, 10 mg of molybdenum carbonyl is added to the mixed solution and ultrasonically treated until homogeneous. Hydrogen gas is then introduced at a flow rate of 20 mL / min, and the temperature is raised to 180 degrees Celsius for 1 h. Subsequently, the cooled mixed solution is washed with n-hexane, and this process is repeated three times under differential centrifugation at 5000 rpm to obtain ultrafine AuPt nanowires.

[0068] Example 6

[0069] This invention provides a method for preparing ultrafine AuPt alloy nanowires. Platinum acetylacetonate and gold trichloride are added to an oleylamine solution and ultrasonically treated to obtain a mixed solution. The amounts of platinum acetylacetonate are 6 mg, gold trichloride is 3 mg, and oleylamine is 5 mL. Then, 10 mg of molybdenum carbonyl is added to the mixed solution and ultrasonically treated until homogeneous. Hydrogen gas is then introduced at a flow rate of 20 mL / min, and the mixture is heated to 180°C for 1 h. The cooled mixed solution is then washed with n-hexane, and this process is repeated three times by differential centrifugation at 5000 rpm to obtain ultrafine AuPt nanowires. Transmission electron microscopy (TEM) energy dispersive spectroscopy analysis of the product revealed that the atomic percentage of Au is approximately 40%, and the atomic percentage of Pt is approximately 60%.

[0070] Electrocatalytic performance test:

[0071] The electrocatalytic performance of the Au / C and AuPt / C catalysts obtained in Examples 3 and 4 for the anode methanol electro-oxidation reaction of methanol fuel cells was tested and compared. Specifically:

[0072] Two mg of the Au / C and AuPt / C catalysts obtained in Examples 3 and 4, respectively, and a commercial Pt / C catalyst (purchased from Johnson & Mattney; Pt mass fraction 20 wt%) were dissolved in 1 mL of a water and ethanol mixture (water to ethanol volume ratio 1:3). After ultrasonic treatment for 1 h to form a paste, 20 μL of the paste was dropped onto the surface of a glassy carbon electrode. After drying, 10 μL of a 0.05% Nafion solution was added. After drying, the electrode was used as the working electrode, and its catalytic activity for methanol electro-oxidation was determined in a 1 mol / L KOH + 0.1 mol / L methanol solution.

[0073] Nitrogen gas was bubbled through a 1 mol / L KOH + 0.1 mol / L methanol solution for 20 min to purge oxygen. Cyclic voltammetric data were then collected at a scan rate of 100 mV / s, and linear voltammetric data were collected at a scan rate of 10 mV / s. The obtained catalytic data are shown below. Figures 4-5 As shown. After 2000 cyclic voltammetric scans, cyclic voltammetric scan data were collected at a scan rate of 100 mV / s. These data were compared with the curves from the first cyclic voltammetric scan, as shown in the figure. Figures 6-7 As shown.

[0074] Figure 1 The image shown is a TEM image of AuPt nanowires. It is easy to see that the synthesized AuPt alloy has the morphology of one-dimensional ultrafine nanowires with a size of 1-3 nm. The ultrafine nanowires greatly improve the atomic utilization rate.

[0075] Figure 2 The image shown is a TEM image of the AuPt / C catalyst. It is easy to see that the AuPt nanowires are uniformly loaded on the carbon black.

[0076] Figure 3 The image shows the XRD pattern of the AuPt / C catalyst. It is easy to see that the peak corresponding to the (111) crystal plane (the peak has a 2θ of 38.8° in the XRD measured pattern) is significantly shifted compared to Au and Pt, indicating that Pt has been uniformly doped into the Au lattice. At the same time, the appearance of a strong (111) crystal plane peak indicates that there are more (111) crystal planes in the catalyst.

[0077] Figure 4 The figure shows the cyclic voltammetry curves for the methanol electro-oxidation reaction of the Au / C catalyst. It can be seen that Au does not exhibit catalytic activity for the methanol oxidation reaction in this potential range, suggesting that the catalytic activity of the AuPt / C catalyst for the methanol electro-oxidation reaction is entirely provided by Pt. Based on... Figure 5 The linear voltammetric scans of the AuPt / C catalyst and the commercial Pt / C catalyst in 1 mol / L KOH + 0.1 mol / L methanol solution shown indicate that the AuPt / C catalyst exhibits high mass activity in the alkaline methanol electro-oxidation reaction, with a mass activity of 65 mA / mg. Pt Approximately commercial Pt / C (19 mA / mg) Pt The catalytic activity is 3.4 times that of Au, which is due to the synergistic effect between Au and Pt that promotes its catalytic activity.

[0078] In addition, such as Figure 6 and Figure 7The comparison of the cyclic voltammetric scans of the AuPt / C catalyst and the commercial Pt / C catalyst after 2000 cycles shows that the AuPt / C catalyst did not exhibit significant changes after 2000 cycles, while the commercial Pt / C catalyst showed significant degradation. This indicates that the AuPt / C catalyst of this invention has superior stability and activity compared to commercial Pt / C in the methanol electro-oxidation reaction, and therefore, this catalyst has broad application prospects in the field of methanol fuel cell catalysis technology.

[0079] While the ultrafine Au nanowires prepared in Example 1 and the Au / C catalyst prepared in Example 3 cannot be applied to the methanol electro-oxidation reaction, they can be used in existing known applications of Au nanowires (such as electrocatalytic carbon dioxide reduction and electronic components, etc.) because of their ultrafine structure, which allows them to function effectively. Furthermore, since the (111) crystal plane is also the dominant crystal plane in the obtained ultrafine Au nanowires, other applications of ultrafine Au nanowires can also be explored.

[0080] Figure 8 The image shows the elemental distribution of the AuPt nanowires in Example 2 of this invention using a high-resolution transmission electron microscope. As can be seen from the image, the diameter of the nanowires is approximately 2 nm, and Au and Pt are uniformly distributed on the nanowires.

[0081] Figure 9 This is a transmission electron microscope image of the AuPt nanowires in Example 5 of the present invention.

[0082] The above embodiments are merely examples. For instance, in the preparation of Au / C materials and AuPt / C catalysts, the concentration of the hexane solution containing AuPt alloy (or Au) ultrafine nanowires can be flexibly adjusted, as can the concentration of the ethanol solution containing carbon black (of course, other carbon materials can also be used besides carbon black). Furthermore, the mass percentage of AuPt ultrafine nanowires in the AuPt / C material can be flexibly adjusted according to actual conditions (for example, to benchmark against a commercially available Pt / C catalyst with a Pt content of 20 wt%, the mass percentage of AuPt ultrafine nanowires can be set around 20 wt%, such as 18-23%).

[0083] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing Au or AuPt alloy ultrafine nanowires, wherein the Au or AuPt alloy ultrafine nanowires have an ultrafine one-dimensional structure and the diameter of the nanowires is 1~3 nm, characterized in that, The preparation method includes the following steps: (1) According to the metal element composition of the target ultrafine nanowire, the corresponding metal salt is added to the oleylamine solution and ultrasonically treated to obtain a mixed solution; wherein, when the target ultrafine nanowire is Au ultrafine nanowire, the metal salt is gold chloride; when the target ultrafine nanowire is AuPt alloy ultrafine nanowire, the metal salt includes platinum acetylacetonate and gold chloride. (2) After adding carbonyl molybdenum or carbonyl tungsten to the mixed solution, ultrasonic treatment is performed; (3) Add borane-tert-butylamine to the mixed solution obtained in step (2) and heat to react; during the reaction, carbonyl groups will generate CO, and borane-tert-butylamine will release hydrogen, thereby achieving the co-reduction of CO and hydrogen; after the reaction, wash and centrifuge the obtained solution to obtain Au ultrafine nanowires or AuPt alloy ultrafine nanowires. In step (1), the concentration of the mixed solution satisfies: For every 4.5-5.5 mL of oleylamine solution, the corresponding amount of gold trichloride added is 3-7.5 mg; and for every 4.5-5.5 mL of oleylamine solution, the corresponding amount of acetylacetone platinum added is 0-6 mg. In step (2), the amount of carbonyl molybdenum or carbonyl tungsten added satisfies the following: For every 4.5–5.5 mL of oleylamine solution, the corresponding amount of added carbonyl molybdenum is 9–11 mg; or, for every 4.5–5.5 mL of oleylamine solution, the corresponding amount of added carbonyl tungsten is 12–14.6 mg. Specifically, step (3) involves adding borane-tert-butylamine to the mixed solution obtained in step (2) and then heating it to carry out the reaction; wherein, the amount of borane-tert-butylamine added is: 9-11 mg of borane-tert-butylamine is added for every 4.5-5.5 mL of oleylamine solution; and the reaction temperature for heating the reaction is 170-190℃. Among the exposed crystal planes of the Au or AuPt alloy ultrafine nanowires, the main exposed crystal plane is the (111) plane.

2. The preparation method according to claim 1, characterized in that, In step (3), the reaction time for heating is 1.5h to 2.5h.

3. The preparation method according to claim 2, characterized in that, In step (3), the reaction temperature for heating is 180°C.

4. The preparation method according to claim 2, characterized in that, In step (3), the reaction time for heating is 2 hours.

5. The preparation method according to claim 1, characterized in that, In both steps (1) and (2), the ultrasonic treatment time is 0.1 to 0.3 hours. In step (3), the centrifugation speed is 4000~6000 rpm; the centrifugation time is 2~3 min. The washing process specifically involves ultrasonic washing, using hexane or acetone as the solvent, and the ultrasonic washing time is 2–3 minutes.

6. The preparation method according to claim 5, characterized in that, In step (3), the centrifugation speed is 4000 rpm and the centrifugation time is 2 min.

7. The preparation method according to claim 1, characterized in that, The ultrafine nanowires are AuPt alloy ultrafine nanowires, with an atomic percentage of Au greater than or equal to 40% and less than 100%. The atomic percentage of Pt is greater than 0 and less than or equal to 60%.

8. The preparation method according to claim 7, characterized in that, In the AuPt alloy ultrafine nanowires, Pt atoms are uniformly distributed within the ultrafine nanowires.

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