Mesoporous platinum@platinum nickel core-shell framework nanowires and methods of making the same

Abstract

This invention relates to a mesoporous platinum@platinum-nickel core-shell framework nanowire and its preparation method, comprising the following steps: (1) uniformly mixing platinum precursor, nickel precursor, structure directing agent, and reducing agent with a first solvent, and performing a hydrothermal reaction to obtain Pt@Pt-Ni core-shell nanowires; (2) uniformly mixing the Pt@Pt-Ni core-shell nanowires with a second solvent and acetic acid, and performing an etching reaction to obtain etched mesoporous platinum@platinum-nickel core-shell framework nanowires. This invention employs a hydrothermal method, which is simple, reproducible, and allows for batch production with safety. Compared with traditional commercial platinum-carbon catalysts, the catalytic activity is greatly improved, the stability is greatly enhanced, and the production cost is reduced.

Description

Technical Field

[0001] This invention belongs to the field of fuel cell cathode materials, specifically relating to a mesoporous platinum@platinum-nickel core-shell framework nanowire and its preparation method. Background Technology

[0002] Fuel cells achieve a degree of resource renewability, with the cathode reaction primarily driven by the oxygen reduction reaction (ORR). However, the sluggish kinetics of ORR and its reliance on high-load Pt-based noble metal catalysts have become key factors hindering the large-scale commercial production of these advanced electrochemical energy conversion technologies. A 2020 research report on the estimated costs of large-scale fuel cell production indicated that 54% of the cost of the fuel cell stack comes from the Pt-based noble metal catalyst layer. Therefore, developing low-cost and highly active catalysts is particularly urgent to reduce or even eliminate dependence on Pt-based noble metals. Furthermore, the reactants in the oxygen reduction reaction are typically air, and impurities in the air (such as CO and SO2) strongly adsorb onto Pt, occupying active sites and poisoning it. Additionally, at the high potential of the cathode, the platinum catalyst and the carbon support are easily oxidized, causing catalyst deactivation and severely affecting cell performance and lifespan. Therefore, improving catalyst stability is also one of the key issues that urgently needs to be addressed in the fuel cell field.

[0003] To address the aforementioned problems, optimization efforts are currently focused on two main aspects. Firstly, optimizing the catalyst's composition. Due to the scarcity and high cost of precious metal Pt, production costs are significantly increased. To reduce these costs, non-precious metals (such as nickel, iron, and copper) are incorporated to decrease Pt usage. Secondly, controlling the catalyst's morphology. Compared to solid catalysts, hollow, porous catalysts (e.g., nanocages, nanoframeworks) have a higher specific surface area, facilitating electron transport during the reaction and resulting in superior catalytic performance. However, after prolonged use and cycling, this structure is prone to collapse, leading to catalyst deactivation. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a mesoporous platinum@platinum-nickel core-shell framework nanowire and its preparation method, thereby solving the technical problem of deactivation caused by catalyst structural instability in the prior art.

[0005] To achieve the above-mentioned technical objectives, the present invention provides a method for preparing mesoporous platinum@platinum-nickel core-shell framework nanowires:

[0006] Includes the following steps:

[0007] (1) Take platinum precursor, nickel precursor, structure directing agent and reducing agent and mix them evenly with the first solvent, and carry out hydrothermal reaction to obtain Pt@Pt-Ni core-shell nanowires;

[0008] (2) Pt@Pt-Ni core-shell nanowires are mixed evenly with the second solvent and acetic acid, and then etched to obtain etched mesoporous platinum@platinum-nickel core-shell framework nanowires.

[0009] Further, in step (1), the platinum precursor is platinum acetylacetonate, the nickel precursor is nickel acetylacetonate, the structure directing agent is CTAB, the reducing agent is glucose, and the first solvent is a mixture of oleylamine and octadecene.

[0010] Furthermore, the ratio between acetylacetonate platinum, oleylamine and octadecene is (0.005-0.015) g : (10-40) mL : (10-40) mL.

[0011] Further, in step (1), the mass ratio of platinum precursor, nickel precursor, structure directing agent and reducing agent is (0.005~0.015):(0.005~0.015):(0.04~0.06):(0.05~0.1).

[0012] Furthermore, in step (1), the hydrothermal reaction is carried out at 160–200 °C for 4–24 h.

[0013] Furthermore, the ratio of the platinum precursor in step (1) to the acetic acid in step (2) is (0.005~0.015) g: (1~5) mL.

[0014] Furthermore, in step (2), the second solvent is a mixture of toluene and oleylamine.

[0015] Furthermore, the ratio of platinum precursor, toluene and oleylamine is (0.005-0.015) g: (1-5) mL: (5-15) uL.

[0016] Furthermore, in step (2), the reaction is carried out by stirring at 60–90 °C for 1–4 h.

[0017] Furthermore, it also includes the following steps:

[0018] (3) Take the etched mesoporous platinum@platinum-nickel core-shell framework nanowires and heat treat them under mixed gas protection to obtain heat-treated mesoporous platinum@platinum-nickel core-shell framework nanowires.

[0019] Furthermore, the heat treatment involves holding the temperature at 250–350℃ for 3–5 hours.

[0020] Furthermore, the mixed gas is a hydrogen-argon mixture with a volume ratio of 3:97; the heating and cooling rates of the heat treatment are both 2–3 °C / min.

[0021] Mesoporous platinum@platinum-nickel core-shell framework nanowires prepared by the above method.

[0022] Compared with the prior art, the beneficial effects of the present invention include:

[0023] 1. Compared with other nanowire preparation processes, this invention uses a hydrothermal method, which is very simple, highly reproducible, and can be mass-produced. The preparation process is also very safe.

[0024] 2. Compared with traditional commercial platinum-carbon catalysts, the catalytic activity is greatly improved and the stability is greatly enhanced; by doping with non-precious metals, the production cost is greatly reduced.

[0025] 3. Structural advantages: The anisotropic structure of one-dimensional nanowires prevents catalysts from migrating and agglomerating and becoming deactivated during long-term reactions; the porous structure increases the specific surface area of ​​the material, providing more active sites for the reaction and facilitating electron transport during the reaction process, thereby increasing the reaction kinetics.

[0026] Furthermore, the heat-treated mesoporous platinum@platinum-nickel core-shell framework nanowires prepared in this invention form a platinum layer several atomic layers thick on the outer surface, based on the etched mesoporous platinum@platinum-nickel core-shell framework nanowires. This surface Pt atomic layer increases the utilization rate of Pt atoms, and the lattice distortion leads to a change in the center of the platinum d-band, reducing the adsorption between Pt and oxide species and improving the catalyst activity. Simultaneously, heat treatment removes organic matter from the sample surface, further increasing catalytic activity. In summary, this structure combines the high activity of nanoparticle catalysts with the high stability of nanowires, providing a better pathway for the synthesis of highly efficient Pt-based catalysts. Attached Figure Description

[0027] Figure 1 The diagram shown is a reaction mechanism diagram of the present invention. a is a theoretical model diagram, and be are transmission electron microscope (TEM) images of actual test samples at different stages of Example 1.

[0028] Figure 2 The images are TEM images of pure Pt nanowires at different resolutions in Comparative Example 1.

[0029] Figure 3 The images show the high-resolution transmission electron microscope (HRTEM) image and energy-dispersive X-ray spectroscopy (EDS) image of the pure Pt nanowires in Comparative Example 1.

[0030] Figure 4 The images shown are TEM images of samples at different reaction stages in Example 1, where a is a TEM image of the sample collected after 30 min of reaction; b is a TEM image of the sample collected after 24 h of reaction; and c is a TEM image of the sample after acetic acid etching.

[0031] Figure 5 These are HRTEM images of the sample at different resolutions after acetic acid etching.

[0032] Figure 6 X-ray diffraction (XRD) patterns of pure Pt nanowires, Pt@Pt-Ni core-shell nanowires, mesoporous Pt@Pt3Ni core-shell framework nanowires, and mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires.

[0033] Figure 7 This is an EDS image of the mesoporous Pt@Pt3Ni core-shell framework nanowires after acetic acid etching in Example 1 of this invention.

[0034] Figure 8 This is a magnified HRTEM image of a mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowire after heat treatment in Example 1 of the present invention.

[0035] Figure 9 TEM images of Pt@Pt-Ni core-shell nanowires with different glucose concentrations, where a is 30 mg, b is 60 mg, and c is 90 mg.

[0036] Figure 10 TEM images of Pt@Pt-Ni core-shell nanowires with different CTAB concentrations, where a is 20 mg, b is 40 mg, and c is 60 mg.

[0037] Figure 11 TEM images of mesoporous Pt@Pt3Ni core-shell framework nanowires under different acidic systems are shown. Image a shows acetic acid with a mass fraction of 99.5%, image b shows acetic acid with a mass concentration of 0.5 M, and image c shows nitric acid with a mass concentration of 0.5 M.

[0038] Figure 12 In the figure, (a) is the linear sweep voltammetry (LSV) plot, and (b) is the mass activity (MA) and area ratio activity (SA) plot. In plots (a) and (b), from left to right, they are commercial PtC, pure Pt nanowires, mesoporous Pt@Pt3Ni core-shell framework nanowires, and mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the following is combined with...

[0040] The accompanying drawings and embodiments provide a more detailed description of the present invention. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0041] The main objective of this invention is to prepare a mesoporous platinum@platinum-nickel core-shell framework nanowire with high electrocatalytic activity. The porous structure provides a larger specific surface area, offering more active sites for the reaction; furthermore, it enhances electron transport between the catalyst and the support, resulting in higher catalytic activity. The sample surface is coated with several atomic layers of platinum, increasing platinum utilization. The nanowires prepared by this invention have a one-dimensional structure, ensuring that the sample does not migrate or aggregate during long-term reactions, thus increasing catalyst stability.

[0042] Specifically, the preparation method of the present invention includes the following steps:

[0043] (1) First, 0.005–0.015 g of platinum acetylacetonate, 0.005–0.015 g of nickel acetylacetonate, 0.04–0.06 g of cetyltrimethylammonium bromide (CTAB) and 0.05–0.1 g of glucose were mixed with 10–40 mL of oleylamine and 10–40 mL of octadecene solution. The mixture was then subjected to ultrasonic treatment for 0.5–1 h to ensure that the solid particles were fully and uniformly dissolved in the solution, resulting in a clear and transparent mixed solution. The solution was then transferred to the lining of a hydrothermal reactor and kept at 160–200 °C for 4–24 h. The product was collected by centrifugation and washed 2–3 times with a mixed solvent of ethanol / cyclohexane (volume ratio of 3:1). Finally, the product was dried at room temperature to obtain Pt@Pt-Ni core-shell nanowires for subsequent characterization tests.

[0044] (2) To further obtain the etched mesoporous platinum@platinum-nickel core-shell framework nanowire structure, the product obtained in the previous step was dispersed in a mixed solvent of 1–5 mL acetic acid (AR, 99.5%), 1–5 mL toluene, and 5–15 μL oleylamine. The mixture was kept in an oil bath at 60–90 °C with appropriate stirring for 1–4 h. Acetic acid was used to etch away the nickel oxide component in the Pt@Pt-Ni core-shell nanowires, thus obtaining a porous structure. The etched product was collected by centrifugation, washed 2–3 times with ethanol / cyclohexane (volume ratio 3:1), and finally dried at room temperature to obtain the etched mesoporous platinum@platinum-nickel core-shell framework nanowires (mesoporous Pt@Pt3Ni core-shell framework nanowires), ready for subsequent testing and characterization.

[0045] (3) Finally, take a small amount of the etched mesoporous platinum@platinum-nickel core-shell framework nanowires onto a ceramic boat, place it in a tube furnace, and anneal it for a certain time under protective gas at a certain temperature to obtain heat-treated mesoporous platinum@platinum-nickel core-shell framework nanowires with Pt atomic layer coverage.

[0046] Mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires.

[0047] Preferably, the mixed gas is a hydrogen-argon mixture with a volume ratio of 3:97, which can effectively prevent the oxidation of the mesoporous Pt@Pt3Ni core-shell framework nanowires at high temperatures after etching.

[0048] Preferably, step (3) involves maintaining the temperature at 250–350°C for 3–5 hours. The heating and cooling rates are 2–3°C / min.

[0049] The etched mesoporous platinum@platinum-nickel core-shell framework nanowires obtained in step (2) and the heat-treated mesoporous platinum@platinum-nickel core-shell framework nanowires obtained in step (3) both show varying degrees of performance improvement compared to commercial platinum-carbon nanowires. Based on their structural characteristics, the mesoporous Pt@Pt3Ni core-shell framework nanowires mentioned below refer to the heat-treated mesoporous platinum@platinum-nickel core-shell framework nanowires, and the mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires refer to the heat-treated mesoporous platinum@platinum-nickel core-shell framework nanowires.

[0050] See Figure 1 The main reaction mechanism of this invention includes:

[0051] Figure 1In the diagram, 'a' represents the mechanism of the entire reaction, and 'be' represents the transmission electron microscope (TEM) images of the products at each stage. Because platinum ions have a stronger reducing power than nickel ions, platinum is first reduced from the platinum precursor to form platinum nanocrystals. Under the action of the structure directing agent, pure platinum nanowires with abundant surface atomic steps are formed (Figure b), providing more nucleation sites for the subsequently reduced grains. As Pt ions are gradually depleted, the reduction and deposition of Pt ions is greatly suppressed, and the Pt-Ni alloy phase begins to selectively deposit on the defect surface of the platinum nanowires (Figure c), until uniform Pt@Pt-Ni core-shell nanowires are formed (Figure d). After treatment under acidic conditions (acetic acid), the nickel-rich phase in the platinum-nickel alloy shell of the nanowires is selectively etched, leaving well-defined mesopores and forming mesoporous Pt@Pt3Ni core-shell framework nanowires. Finally, the mesoporous Pt@Pt3Ni core-shell framework nanowires are annealed at high temperature, and the platinum atoms in the interior will segregate to the surface to form a platinum layer several atomic layers thick. At the same time, organic matter on the sample surface is removed, improving the activity of the catalyst. The mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowire catalyst can be prepared through the above series of preparation processes (Figure e).

[0052] The mesoporous platinum@platinum-nickel core-shell framework nanowires prepared in this invention are one-dimensional metallic nanowires.

[0053] The structure can effectively address the catalyst stability issue. Due to its inherent anisotropy, the one-dimensional nanostructure can achieve close contact with the carbon support surface. This close contact enhances electron transfer between the reactants and the Pt surface and promotes the bonding between the nanowires and the carbon support, thereby achieving high stability.

[0054] This invention presents mesoporous platinum@platinum-nickel core-shell framework nanowires as a catalyst exhibiting high electrocatalytic activity. The catalyst's cost is reduced by doping with non-noble metal nickel (Ni) to decrease the platinum (Pt) loading. Simultaneously, the porous framework structure facilitates contact between the reaction solution and more Pt catalytically active sites, improving reaction kinetics. Furthermore, the surface Pt atomic layer of the mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires undergoes lattice distortion, altering its electronic structure and weakening the adsorption of oxygen-containing species, which is also the main reason for its improved electrocatalytic activity. The one-dimensional mesoporous platinum@platinum-nickel core-shell framework nanowires prepared in this invention have strong interfacial contact with the carbon support, preventing catalyst migration and agglomeration leading to deactivation during prolonged reactions, thus demonstrating high stability.

[0055] The present invention will be further explained and illustrated by specific examples below:

[0056] Comparative Example 1: Preparation of pure platinum nanowires

[0057] Weigh 0.01 g of platinum acetylacetonate (Pt(acac)2), 0.06 g of glucose, and 0.04 g of hexadecyltrimethylammonium bromide (CTAB) using an electronic balance and place them into a 20 mL glass bottle. Then, pipette 5 mL of oleylamine (OAm) and 5 mL of octadecene (ODE) and pour them into the previously weighed sample bottle. Sonicate the weighed reagents for 1 h to ensure homogeneity. Finally, transfer the mixture to a 50 mL hydrothermal reactor liner and heat at 200°C for 24 h. Collect the obtained product by centrifugation, wash it three times with a 3:1 (v / v) mixture of ethanol and cyclohexane, and finally dry it at room temperature to obtain pure platinum nanowires for subsequent characterization tests.

[0058] The morphology of the pure platinum nanowire sample prepared in this comparative example is as follows: Figure 2 As shown in Figures a and b at different magnifications, the nanowires have a diameter of approximately 3–5 nm and their surface has abundant atomic steps. This structure can provide more nucleation sites for subsequent platinum-nickel alloying.

[0059] The EDS spectra of the pure platinum nanowires prepared in this comparative example are as follows: Figure 3 (a) to (c)

[0060] This indicates that the nanowires contain only Pt; at the same time Figure 6 The XRD patterns show that the diffraction peaks of the pure platinum nanowire sample in this comparative example correspond one-to-one with the standard Pt diffraction peaks. These results demonstrate that pure Pt nanowires were successfully prepared in this comparative example.

[0061] Example 1: Preparation of mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires

[0062] (1) Preparation of Pt@Pt-Ni core-shell nanowires: 0.01 g of platinum acetylacetonate (Pt(acac)2), 0.008 g of nickel acetylacetonate (Ni(acac)2), 0.06 g of glucose, and 0.04 g of hexadecyltrimethylammonium bromide (CTAB) were weighed using an electronic balance and placed into a 20 mL glass bottle; then, 5 mL of oleylamine (OAm) and 5 mL of octadecene (ODE) were measured using a pipette and added to the previously weighed sample glass bottle. The weighed reagents were sonicated for 1 h to ensure uniform mixing. Finally, the mixture was transferred to a 50 mL hydrothermal reactor liner and heated in an oven at 200 °C for 24 h. The obtained product was collected by centrifugation and washed three times with a mixed solvent of ethanol / cyclohexane (volume ratio 3:1). Finally, it was dried at room temperature for subsequent characterization tests.

[0063] The morphology of the prepared sample is as follows Figure 4As shown in a and b Figure 4 Image a shows the TEM morphology of the sample after 30 min of hydrothermal reaction. The image reveals that uniform nanowires with a diameter of approximately 3 nm and a length of 200–500 nm are formed at the beginning of the reaction. EDX elemental analysis indicates that the main component of these nanowires is Pt. HRTEM further reveals that the Pt nanowires exhibit typical (111) interplanar spacing (0.23 nm) and high-density, low-coordination surface atomic steps. The formation of Pt nanowires is mainly due to the stronger reducing power of platinum ions compared to nickel ions. In the initial stage of the reaction, Pt ions are reduced first, forming Pt nanowires with abundant surface defects under the action of a structure-directing agent. This provides new sites for subsequent co-reduction nucleation growth of platinum and nickel ions. After a period of continued reaction, as Pt ions are gradually depleted, Pt ion deposition is greatly suppressed, and the Pt-Ni alloy phase begins to selectively deposit on the surface defect sites of the Pt nanowires. When the reaction time is extended to 24 hours, stable Pt@Pt-Ni core-shell nanowires are formed, such as… Figure 4 As shown in b, the overall morphology of the sample resembles a "candied hawthorn skewer" and is uniform. HRTEM and EDS analyses indicate that the sample has 0.23 nm lattice fringes at the shell edge and 0.21 nm lattice fringes on the shell surface, corresponding to the (111) planes of the platinum-rich and nickel-rich phases, respectively. These characterization data demonstrate the Pt@Pt-Ni core...

[0064] The surface composition of the shell of the Pt@Pt-Ni core-shell nanowire is mainly platinum-rich, while the interior composition is mainly nickel-rich. Experiments show that Pt atoms (Pt = 1.39 Å, Ni = 1.24 Å) inside the shell of the Pt@Pt-Ni core-shell nanowire tend to migrate outward to the edge to reduce the large lattice strain energy under solvothermal conditions.

[0065] (2) Preparation of mesoporous Pt@Pt3Ni core-shell framework nanowires: A small amount of the sample prepared in step (1) was weighed and added to a 20 mL glass bottle. Then, 2 mL of toluene, 2 mL of acetic acid, and 10 μL of oleylamine were measured by pipette and added to the previously weighed sample glass bottle. Finally, the mixture was stirred in an oil bath at 90 °C for 2 h. The resulting product was collected by centrifugation and washed three times with a mixed solvent of ethanol / cyclohexane (volume ratio of 3:1). Finally, the product was dried at room temperature for subsequent characterization tests.

[0066] The morphology of the prepared sample is as follows Figure 4 As shown in c, after acetic acid treatment, the nickel-rich phase in the shell of the Pt@Pt-Ni core-shell nanowire is selectively etched, and finally a well-defined three-dimensional open mesoporous Pt@Pt3Ni core-shell framework nanowire is formed, while the entire hollow framework structure is connected by a thin Pt nanowire.

[0067] To further characterize the pore structure, HRTEM tests were performed on mesoporous Pt@Pt3Ni core-shell framework nanowire samples. Figure 5 a and b are HRTEM images of the sample at different resolutions. The HRTEM image of a single mesoporous Pt@Pt3Ni core-shell framework nanowire clearly shows the ultrafine (~3 nm) platinum nanowire core and the three-dimensional open mesoporous (2~5 nm) shell structure.

[0068] Compared to the sample before acetic acid etching, the XRD pattern ( Figure 6 The results indicate that the diffraction peaks of the sample shifted to higher angles after etching. This is mainly due to the shrinkage of the platinum lattice caused by the incorporation of nickel, which also proves the formation of the PtNi alloy phase.

[0069] The EDS spectrum of the catalyst obtained in step (2) Figure 7 (a) to (c) show that Ni is mainly distributed on the mesoporous hollow framework shell, while platinum is mainly distributed on the 3 nm core nanowires and the surface of the PtNi alloy framework shell; through Figure 7 (d) The distribution area of ​​the elements in both determines that the platinum-nickel alloy is Pt3Ni.

[0070] (3) Preparation of mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires: Weigh a small amount of the sample prepared in step (2) and pour it into a ceramic boat. Then place the ceramic boat in a tube furnace and add...

[0071] Before heating, a hydrogen-argon mixed gas was purged for 30 minutes to purge the air from the tube furnace and prevent sample oxidation at high temperatures. Then, a programmed temperature control was used to raise the temperature from room temperature (25 °C) to 300 °C (heating time 120 minutes), followed by holding at 300 °C for 4 hours. Finally, the temperature was cooled back to room temperature (25 °C) using a programmed temperature control method (cooling time 120 minutes). Gas protection was essential throughout the entire heating process to prevent oxidation of the metal alloy. Through this heat treatment, platinum atoms from the alloy partially segregated to the sample surface, forming a Pt layer several atomic layers thick. This Pt atomic layer not only effectively improved the utilization rate of platinum atoms but also significantly enhanced the catalytic activity of the sample.

[0072] To characterize the Pt atomic layer structure on the surface, this invention performed local HRTEM characterization on the heat-treated sample, such as... Figure 8As shown, the thickness of the Pt atomic layer is approximately 0.6 nm, equivalent to the size of four Pt atoms. This ultrathin Pt atomic layer encapsulated on Pt3Ni maximizes Pt utilization and significantly enhances its electrocatalytic (e.g., ORR) activity. Compared to the (111) interplanar spacing (2.27 Å) of the Pt nanowire core, the (111) interplanar spacing of the surface Pt atomic layer is 2.19 Å. This invention proposes that the ultrathin curved framework wall in the heat-treated mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowire not only imparts a high electrochemically active surface area but also induces compressive strain, ultimately altering the catalytic activity by changing the electronic structure of the catalyst surface and affecting the d-band centers of Pt atoms.

[0073] Example 2: Pt@Pt-Ni core-shell nanowires prepared with different amounts of glucose

[0074] To investigate the effect of different glucose contents on the morphology of Pt@Pt-Ni core-shell nanowires and to achieve the most ideal preparation conditions, the following experiments were conducted in this invention:

[0075] Group 21: Weigh 0.01 g of platinum acetylacetonate (Pt(acac)2), 0.008 g of nickel acetylacetonate (Ni(acac)2), 0.03 g of glucose, and 0.04 g of hexadecyltrimethylammonium bromide (CTAB) using an electronic balance and place them into a 20 mL glass bottle. Then, use a pipette to measure 5 mL of oleylamine (OAm) and 5 mL of octadecene (ODE) and add them to the previously weighed sample glass bottle. Sonicate the weighed reagents for 1 h to ensure homogeneity. Finally, transfer the mixture to a 50 mL hydrothermal reactor liner and heat in an oven at 200°C for 24 h. Collect the obtained product by centrifugation, wash three times with a 3:1 (volume ratio) ethanol / cyclohexane mixture, and finally dry at room temperature for subsequent characterization tests.

[0076] Group 22: The steps and conditions are the same as in Group 21, except that the amount of glucose is changed to 0.06 g.

[0077] Group 23: The steps and conditions are the same as in Group 21, except that the amount of glucose is changed to 0.09 g.

[0078] Figure 9TEM images of samples prepared with different amounts of glucose. Glucose acts as a reducing agent to reduce platinum-nickel from the precursor. As shown in Figure a (30 mg), when the amount of glucose is very small, the sample mainly exists in the form of nanoparticles; as the amount increases to 60 mg (Figure b), uniform core-shell nanowires are formed; further increasing to 90 mg (Figure c), the morphology of the sample does not change significantly compared to Figure b. Therefore, the preferred amount of glucose in this invention is 0.05–0.1 g, and more preferably 0.06–0.09 g.

[0079] Example 3: Pt@Pt-Ni core-shell nanowires prepared with different amounts of CTAB

[0080] Group 31: Weigh 0.01 g of platinum acetylacetonate (Pt(acac)2), 0.008 g of nickel acetylacetonate (Ni(acac)2), 0.06 g of glucose, and 0.02 g of hexadecyltrimethylammonium bromide (CTAB) using an electronic balance and place them into a 20 mL glass bottle. Then, use a pipette to measure 5 mL of oleylamine (OAm) and 5 mL of octadecene (ODE) and add them to the previously weighed sample glass bottle. Sonicate the weighed reagents for 1 h to ensure homogeneity. Finally, transfer the mixture to a 50 mL hydrothermal reactor liner and heat in an oven at 200°C for 24 h. Collect the obtained product by centrifugation, wash three times with a 3:1 (volume ratio) ethanol / cyclohexane mixture, and finally dry at room temperature for subsequent characterization tests.

[0081] Group 32: The steps and conditions are the same as in Group 31, except that the amount of glucose is changed to 0.04 g.

[0082] Group 33: The steps and conditions are the same as in Group 31, except that the amount of glucose is changed to 0.06 g.

[0083] Figure 10 TEM images of samples prepared with different amounts of CTAB. Figure a shows 20 mg CTAB. When the amount is too low, the sample forms nanorods of varying lengths and is very disordered. When the amount of CTAB increases to 40 mg, the sample exists in the form of core-shell nanowires. Further increases in the amount of CTAB do not significantly change the morphology compared to Figure b. CTAB, as a surfactant, coats the specific surface of the sample, guiding the formation of regular shapes.

[0084] When the amount of surfactant is too small, some samples will not be fully covered, resulting in a messy morphology. However, too much surfactant is not beneficial to the sample either, as it will cover the surface and affect subsequent activity tests. Therefore, the preferred amount of CTAB in this invention is 0.04–0.06 g.

[0085] Example 4: Mesoporous Pt@Pt3Ni core-shell framework nanowires prepared under different acidic systems

[0086] Group 41: (1) Weigh 0.01 g of platinum acetylacetonate (Pt(acac)2), 0.008 g of nickel acetylacetonate (Ni(acac)2), 0.06 g of glucose, and 0.04 g of hexadecyltrimethylammonium bromide (CTAB) using an electronic balance and place them into a 20 mL glass bottle; then use a pipette to measure 5 mL of oleylamine (OAm) and 5 mL of octadecene (ODE) and add them to the previously weighed sample glass bottle. Sonicate the weighed reagents for 1 h to mix them evenly. Finally, transfer them to a 50 mL hydrothermal reactor liner and heat them in an oven at 200 degrees Celsius for 24 h. Collect the obtained product by centrifugation and wash it three times with a mixed solvent of ethanol / cyclohexane (volume ratio of 3:1). Finally, dry it at room temperature for subsequent characterization tests.

[0087] (2) Weigh a small amount of the sample prepared in step (1) and add it to a 20 mL glass bottle. Then, use a pipette to measure 2 mL of toluene, 2 mL of 99.5% acetic acid, and 10 μL of oleylamine, and add them to the previously weighed sample glass bottle. Finally, stir the reaction in an oil bath at 90 °C for 2 h. Collect the obtained product by centrifugation and wash it three times with a mixed solvent of ethanol / cyclohexane (volume ratio of 3:1). Finally, dry it at room temperature for subsequent characterization tests.

[0088] Group 42: The steps and conditions are the same as those in Group 41, except that the 2 mL of 99.5% acetic acid in step (2) is replaced with 2 mL of 0.5 M acetic acid.

[0089] Group 43: The steps and conditions are the same as those in Group 41, except that the 2 mL of 99.5% acetic acid in step (2) is replaced with 2 mL of 0.5 M nitric acid.

[0090] Figure 11 TEM images of mesoporous Pt@Pt3Ni core-shell framework nanowires prepared under different acidic systems. Figure a shows the surface of the sample treated with 2 mL of 99.5% acetic acid. It can be seen that very obvious pores appeared on the surface of the acid-treated sample, with pore sizes of approximately 2–5 nm. When the acetic acid concentration was reduced to 0.5 M, the morphology of the sample treated under the same conditions is shown in Figure b, which shows no significant change compared to the sample before acid treatment.

[0091] No obvious pores appeared on the nanowires. After changing the acid to 0.5 M nitric acid, the morphology of the prepared samples is shown in Figure c. Compared to the samples before acid treatment, some samples showed obvious pores. The above experiments show that the concentration and strength of the acid are very important for the formation of porous structures. Higher concentrations of acetic acid solution are more likely to react with Ni to form porous nanowire structures; while strong acids tend to cause inhomogeneity in the porous structure.

[0092] Application examples

[0093] This invention compares the ORR catalytic performance of three samples—pure Pt nanowires prepared in Comparative Example 1, mesoporous Pt@Pt3Ni core-shell framework nanowires prepared in Example 1 after acetic acid etching, and heat-treated mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires—with that of a commercial platinum-carbon (PtC) catalyst. Before electrochemical testing, the prepared catalysts were first loaded onto a commercial carbon support (XC-72R) to obtain good dispersibility, with the loading amount controlled at 20 wt%. The catalysts were then prepared as ink droplets and coated onto the surface of the working electrode for subsequent testing. Subsequently, the catalysts were tested at 50 mV s⁻¹. -1 The catalysts were characterized by linear cyclic voltammetry (CV) at scan rates within a potential range of 0.03–1.1 V. Further processing of the test data yielded the mass activity (MA) and surface area activity (SA) for each catalyst. Finally, linear sweep voltammetry (LSV) tests were performed in an O2-saturated 0.1 M HClO4 electrolyte, with scan ranges and rates of 0.2–1.2 V and 10 mV s, respectively. -1 The rotational speed was 1600 rpm. All tests were conducted at room temperature.

[0094] Figure 12 The performance data for each catalyst are shown in Table 1 below.

[0095] Table 1 Performance test results of different catalysts

[0096]

[0097] From Table 1 and Figure 12 As can be seen from the LSV in Figure a, it is a mesoporous Pt@Pt3Ni core-shell framework.

[0098] The half-wave potential of the nanowires is 0.94 V (vs. RHE), while the half-wave potential of the mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires is 0.96 V (vs. RHE), which is more positive than that of commercial PtC (0.812 V (vs. RHE)), indicating better performance. Figure b shows the MA and SA of each catalyst, with the mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowires exhibiting the highest MA and SA, which are 28 times and 26 times higher than those of commercial PtC, respectively. Based on the above analysis, the mesoporous platinum@platinum-nickel core-shell framework nanowires of this invention exhibit better catalytic performance, with a half-wave potential of 0.94–0.96 V and an MA of 2.1–6.2 A / mg. pt SA can reach 3.2–8.1 mA / cm 2 Among them, the mesoporous Pt@Pt-skin Pt3Ni core-shell framework nanowire catalyst exhibits the best performance.

[0099] This invention discloses a method for preparing mesoporous platinum@platinum-nickel core-shell framework nanowires. A solvothermal synthesis method is employed, where reactants are placed in a hydrothermal reactor liner and reacted in an oven at 160–200 °C for 4–24 h to obtain Pt@Pt-Ni core-shell nanowires. Then, nickel oxide in the alloy is etched into porous mesoporous Pt@Pt3Ni core-shell framework nanowires using acetic acid. Finally, the etched sample undergoes high-temperature heat treatment to obtain mesoporous Pt@Pt-skinPt3Ni core-shell framework nanowires with a surface coating of several platinum atoms. This invention reduces production costs by doping with nickel atoms and improving the utilization rate of platinum atoms, thereby reducing the amount of platinum atoms used in the catalyst. The prepared one-dimensional mesoporous platinum@platinum-nickel core-shell framework nanowires exhibit strong interactions with the carbon support and maintain good stability after long-term cyclic use. The ultrathin surface platinum atom layer and porous structure provide more catalytic active sites, accelerate electron transport during the reaction process, increase reaction kinetics, and improve catalytic activity.

[0100] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing mesoporous platinum@platinum-nickel core-shell framework nanowires, characterized in that, Includes the following steps: (1) Take platinum precursor, nickel precursor, structure directing agent and reducing agent and mix them evenly with the first solvent, and carry out hydrothermal reaction to obtain Pt@Pt-Ni core-shell nanowires; (2) Pt@Pt-Ni core-shell nanowires are mixed evenly with the second solvent and acetic acid, and then etched to obtain etched mesoporous platinum@platinum-nickel core-shell framework nanowires. (3) Take the etched mesoporous platinum@platinum-nickel core-shell framework nanowires and heat treat them under mixed gas protection to obtain heat-treated mesoporous platinum@platinum-nickel core-shell framework nanowires; the heat treatment is carried out at 250-350℃ for 3-5 hours. In step (1), the platinum precursor is platinum acetylacetonate, the nickel precursor is nickel acetylacetonate, the structure directing agent is CTAB, the reducing agent is glucose, and the first solvent is a mixture of oleylamine and octadecene. In step (1), the mass ratio of platinum precursor, nickel precursor, structure directing agent, and reducing agent is (0.005~0.015):(0.005~0.015):(0.04~0.06):(0.05~0.1). The ratio of platinum precursor in step (1) to acetic acid in step (2) is (0.005~0.015) g : (1~5) mL.

2. The method for preparing mesoporous platinum@platinum-nickel core-shell framework nanowires according to claim 1, characterized in that, In step (1), the hydrothermal reaction is carried out at 160-200 °C for 4-24 h.

3. The method for preparing mesoporous platinum@platinum-nickel core-shell framework nanowires according to claim 1, characterized in that, In step (2), the second solvent is a mixture of toluene and oleylamine.

4. The method for preparing mesoporous platinum@platinum-nickel core-shell framework nanowires according to claim 1, characterized in that, In step (2), the reaction is carried out by stirring at 60-90 °C for 1-4 h.

5. The method for preparing mesoporous platinum@platinum-nickel core-shell framework nanowires according to claim 1, characterized in that, The mixed gas is a hydrogen-argon mixture with a volume ratio of 3:97; the heating and cooling rates of the heat treatment are both 2-3 °C / min.

6. Mesoporous platinum@platinum-nickel core-shell framework nanowires prepared by the preparation method according to any one of claims 1-5.

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