A core-shell structure Pd@PtRuNi nanowire and a preparation method and application thereof

Abstract

This invention relates to the field of electrocatalysis technology, specifically disclosing a core-shell structured Pd@PtRuNi nanowire, its preparation method, and its applications. This invention first uses a hydrothermal method to prepare Pd nanowires, and then utilizes the metal co-reduction effect to transform Pd... 2+ Ru 3+ and Ni 2+ Epitaxial growth was performed on the surface of Pd nanowires to obtain highly active and stable bifunctional Pd@PtRuNi core-shell nanowires. These nanowires were then used as catalysts in the oxygen reduction reaction at the cathode and the methanol oxidation reaction at the anode of fuel cells, exhibiting excellent catalytic activity in both cases. When used as a cathode catalyst, its mass activity was 5.31 times that of commercial platinum-carbon catalysts; when used as an anode catalyst, its mass activity at the peak value of the pre-scan was 3.18 times that of commercial platinum-carbon catalysts at the same potential. This provides a novel and simple approach for the research and exploration of bipolar catalysts for fuel cells.

Description

Technical Field

[0001] This invention relates to the field of electrocatalysis technology, and in particular to a core-shell structured Pd@PtRuNi nanowire, its preparation method, and its applications. Background Technology

[0002] With the escalating environmental pollution and energy crisis, the development of clean and renewable energy has become a current research hotspot. Hydrogen, as a carrier of green renewable energy, has been recognized as an ideal energy source to replace fossil fuels. Fuel cells, as a downstream industry of hydrogen energy utilization, possess numerous advantages such as high efficiency, greenness, and sustainability. The key to developing fuel cell technology lies in the selection of efficient catalysts. Pt-based catalysts are currently recognized as the best electrocatalysts for fuel cells; however, their high cost and scarce reserves severely hinder the commercial application of these precious metal catalysts. Therefore, designing a cheap, efficient, and abundant element-based electrocatalyst is crucial for the development of fuel cell technology.

[0003] In past research, scientists have investigated the impact of catalyst dimensionality on catalytic performance. One-dimensional nanomaterials, due to their high electron transport rates and resistance to Ostwald ripening, are considered a promising class of catalytic materials. Attaching platinum to the surface of other metals (M) to generate platinum-based catalysts with an M@Pt core-shell structure is the most common and effective method. However, the stability of one-dimensional core-shell catalytic materials still needs improvement. During long-term operation of fuel cells, the core supporting metal gradually dissolves and separates over time, significantly affecting the morphology and catalytic activity of the outer Pt metal. Therefore, the development of a fuel cell catalyst based on low cost, high catalytic activity, and high stability is of great significance. Summary of the Invention

[0004] To address the problems of high cost, low catalytic activity, and poor stability and recyclability of existing fuel cell catalysts, this invention provides a core-shell structured Pd@PtRuNi nanowire, its preparation method, and its applications.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the embodiments of the present invention is as follows:

[0006] In a first aspect, the present invention provides a core-shell structured Pd@PtRuNi nanowire, comprising a Pd nanowire core layer and a PtRuNi alloy layer covering the outside of the Pd nanowire.

[0007] Furthermore, the diameter of the core-shell structured Pd@PtRuNi nanowire is 7nm-17nm, and the length is 100nm-500nm.

[0008] Furthermore, the thickness of the PtRuNi alloy layer is 2.6nm-3.4nm, wherein the atomic ratio of Pt, Ru, and Ni is 4.8:3.6:1.

[0009] Compared to existing technologies, the core-shell structured Pd@PtRuNi nanowires provided by this invention, using low-cost Pd nanowires as the core and a PtRuNi alloy layer as the outer shell, significantly improves the stability of the catalyst. Furthermore, the surface of the core-shell nanowires can fully expose Pt elements, and through the coupling of the d-electron orbitals of Pt, Ru, and Ni, the electronic structure at the Pt sites can be effectively controlled, greatly enhancing the catalyst's reactivity. Simultaneously, the stress and strain effects of multiple metal elements improve the utilization rate of Pt in the material, reducing the cost of Pt-based catalysts. This provides a new approach for constructing lower-cost fuel cell electrode catalysts and has high potential for widespread application.

[0010] Secondly, the present invention provides a method for preparing core-shell structured Pd@PtRuNi nanowires, comprising the following steps:

[0011] Step a, prepare Pd nanowires;

[0012] Step b: Disperse the Pd nanowires in an organic solvent to obtain a Pd nanowire dispersion; then disperse the Pt nanowires in an organic solvent. 2+ Ru 3+ and Ni 2+ The precursor solution was mixed evenly with the Pd nanowire dispersion and reacted at 180℃-200℃ for 1-2 hours. After cooling, washing, and drying, core-shell structured Pd@PtRuNi nanowires were obtained.

[0013] This invention utilizes the metal co-reduction effect to make Pt 2+ Ru 3+ and Ni 2+ By epitaxially growing Pd@PtRuNi nanowires on the surface of Pd nanowires, uniform core-shell structured Pd@PtRuNi nanowires were obtained. These nanowires have a high specific surface area, allowing for the full exposure of Pt elements. Through the synergistic effect of Ru, Ni, and Pt, the catalytic activity of the material is significantly improved. In addition, the nanowires can act as transport channels to accelerate electron transfer in the electrochemical reaction process, thereby significantly improving the activity and efficiency of the electrocatalytic reaction. Furthermore, using a PtRuNi ternary alloy as the shell significantly improves the stability of the catalyst, making it a promising candidate for application in the field of fuel cells.

[0014] Preferably, step a specifically includes the following steps:

[0015] Polyvinylpyrrolidone and sodium iodide were dissolved in water to obtain a mixed solution; Pd salt aqueous solution was added to the mixed solution, and the mixture was subjected to hydrothermal reaction at 190℃-215℃ for 150min-160min, cooled, washed, and dried to obtain Pd nanowires.

[0016] For example, in step a, the Pd salt aqueous solution is an aqueous solution of palladium chloride or an aqueous solution of sodium tetrachloropalladate.

[0017] For example, in step a, the mass ratio of polyvinylpyrrolidone to water is 1:12-18.

[0018] Preferably, in step a, the molecular weight of the polyvinylpyrrolidone is 1,000-1,300,000.

[0019] For example, in step a, the concentration of the Pd salt aqueous solution is 25 mmol / L-33 mmol / L, and its volume ratio with the mixed solution is 3-6:12-18.

[0020] For example, in step a, a mixed solution of anhydrous ethanol and acetone in a volume ratio of 1:2 is centrifuged and washed 3-4 times at a speed of 8000 r / min-9000 r / min.

[0021] Using polyvinylpyrrolidone as a reducing agent and sodium iodide as a capping agent, Pd nanowires with uniform morphology can be prepared under specific reaction conditions.

[0022] Specifically, step b involves dispersing Pd nanowires in an organic solvent to obtain a Pd nanowire dispersion, heating it to 180℃-200℃, and then adding Pt nanowires... 2+ Ru 3+ and Ni 2+ The precursor solution was added to the Pd nanowire dispersion, and the reaction was carried out at a constant temperature for 1-2 hours. After cooling, centrifugation, washing, and drying, core-shell structured Pd@PtRuNi nanowires were obtained.

[0023] Preferably, in step b, the organic solvent is benzyl alcohol.

[0024] Benzyl alcohol can promote the reaction to proceed fully and it has reducing power, which can promote the reduction of metal ions in the precursor.

[0025] Preferably, in step b, the concentration of the Pd nanowire dispersion is 0.2-0.5 mg / mL.

[0026] Preferably, in step b, the precursor solution contains Pt 2+ Ru 3+ and Ni 2+ The molar ratio is 2:1:2-1:2:1.

[0027] Preferably, in step b, the solvent of the precursor solution is a mixture of oleylamine and oleic acid in a volume ratio of 2:1 to 5:3.

[0028] A specific ratio of oleylamine and oleic acid can effectively control the reduction rate of metal ions in the precursor solution, enabling Pt, Ru, and Ni to grow uniformly on the surface of Pd nanowires, thus obtaining Pd@PtRuNi nanowires with a uniform core-shell structure.

[0029] Preferably, in step b, the precursor solution is a mixed solution of Pt(acac)2, Ru(acac)3, and Ni(acac)2, wherein Pt 2+ The concentration was 1.7 mmol / L-2 mmol / L, Ru 3+ The concentration of Ni ranged from 0.9 mmol / L to 3.4 mmol / L. 2+ The concentration is 1.7 mmol / L-2 mmol / L.

[0030] Preferably, in step b, the volume ratio of the Pd nanowire dispersion to the precursor solution is 1:2.5-3.5.

[0031] For example, in step b, the precursor solution is added to the Pd nanowire dispersion by dropping, with a dropping rate of 0.05-0.1 mL / min.

[0032] For example, in step b, after the reaction is complete, the temperature is lowered to room temperature, and the reaction product is washed sequentially with cyclohexane and anhydrous ethanol at 3000 r / min-4000 r / min for 8-12 min to obtain core-shell structured Pd@PtRuNi nanowires.

[0033] The optimized reaction conditions facilitate the full reaction of the raw materials, resulting in the preparation of core-shell structured Pd@PtRuNi nanowires with uniform morphology, which in turn improves the catalytic activity and stability of the material.

[0034] Thirdly, the present invention also provides the application of the above-mentioned core-shell structured Pd@PtRuNi nanowires as catalysts in the catalytic oxygen reduction reaction at the cathode or the catalytic methanol oxidation reaction at the anode of a fuel cell.

[0035] The core-shell structured Pd@PtRuNi nanowires provided by this invention utilize the metal co-reduction effect to transform Pt... 2+ Ru 3+ and Ni 2+Epitaxial growth of Pd@PtRuNi nanowires on the surface of Pd nanowires yielded uniform core-shell structured Pd@PtRuNi nanowires. This not only effectively improved the catalytic activity of Pd@PtRuNi nanowires but also significantly enhanced their stability. When used as catalysts in the oxygen reduction reaction at the cathode and the methanol oxidation reaction at the anode of fuel cells, they exhibited excellent catalytic activity: when used as a cathode catalyst, their mass activity was 5.31 times that of commercial platinum-carbon catalysts; when used as an anode catalyst, their mass activity at the peak value of the pre-scan was 3.18 times that of commercial platinum-carbon catalysts at the same potential. This provides a novel and simple approach for the research and exploration of bipolar catalysts for fuel cells, with high potential application value. Attached Figure Description

[0036] Figure 1 The images show the TEM and XRD patterns of the Pd nanowires prepared in Example 1 of this invention, where (a) is the TEM image and (b) is the XRD image.

[0037] Figure 2 The images show the TEM and XRD patterns of the Pd@PtRuNi nanowires prepared in Example 2 of this invention, where (a) is the TEM image and (b) is the XRD image.

[0038] Figure 3 The images show TEM and HRTEM images of the Pd@PtRuNi nanowires prepared in Example 3 of this invention, where (a) is a TEM image and (b) is an HRTEM image; the upper right corner of image (b) is a magnified view of the area within the black frame.

[0039] Figure 4 The images show the TEM and energy dispersive spectroscopy (EDS) spectra of the Pd@PtRuNi nanowires prepared in Example 3 of this invention, where (a) is the TEM image and (b) is the EDS spectra.

[0040] Figure 5 The HAADF image and elemental linear scan analysis diagram of the Pd@PtRuNi nanowires prepared in Example 3 of this invention are shown, where (a) is the HAADF image and (b) is the elemental linear scan analysis diagram.

[0041] Figure 6 The graphs show the half-cell performance of fuel cell cathodes with Pd@PtRuNi nanowires prepared in Example 3, Pd@Ru nanowires prepared in Comparative Example 4, and Pd@Pt nanowires prepared in Comparative Example 5, compared with commercial platinum-carbon catalysts. (a) CV curve, (b) LSV curve.

[0042] Figure 7 The figures show the half-cell performance test results of the fuel cell cathodes of Pd@PtRuNi nanowires prepared in Example 3 and Comparative Examples 1-3 of this invention, where (a) is the CV curve and (b) is the LSV curve.

[0043] Figure 8 The graphs show the cycle stability test results of Pd@PtRuNi nanowires prepared in Example 3 of this invention and a commercial platinum-carbon catalyst, where (a) is the LSV curve before and after cycling, and (b) is a comparison graph of mass activity before and after cycling.

[0044] Figure 9 The images show TEM images of the Pd@PtRuNi nanowires prepared in Example 3 of this invention before and after cycling stability testing, where (a) is the TEM image before cycling and (b) is the TEM image after cycling.

[0045] Figure 10 The CV curves show the performance of the Pd@PtRuNi nanowires prepared in Example 3 of this invention, the Pd@Ru nanowires prepared in Comparative Example 4, and the fuel cell anode half-cells with commercial platinum-carbon catalysts. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0047] To better illustrate the present invention, further examples are provided below.

[0048] Example 1

[0049] This embodiment provides a method for preparing core-shell structured Pd@PtRuNi nanowires, including the following steps:

[0050] Step 1: Weigh 1g of polyvinylpyrrolidone (average molecular weight 1000-1300000), dissolve 300mg of sodium iodide in 15mL of deionized water, sonicate to dissolve, then add 3mL of 33mmol / L Na2PdCl4 aqueous solution, stir evenly, then transfer to a hydrothermal reactor lined with polytetrafluoroethylene, place in an oven at 190℃ for 155min, cool to room temperature, centrifuge and wash 4 times with a mixture of anhydrous ethanol and acetone at 9000r / min (volume ratio 1:2), dry to obtain Pd nanowires;

[0051] Step 2: Disperse Pd nanowires in benzyl alcohol to obtain a Pd nanowire dispersion with a concentration of 0.3 mg / mL.

[0052] Step 3: Heat the oil bath to 180℃, place a 100mL three-necked flask in it and preheat for 5min. Add 20mL of the prepared Pd nanowire dispersion to the flask and stir for 5min. Slowly add a precursor mixture with a molar ratio of Pt:Ru:Ni = 2:1:2 (solvent is oleylamine and oleic acid with a volume ratio of 5:3, Pt) at a rate of 0.1mL / min. 2+ The concentration was 2 mmol / L, Ru 3+ The concentration of Ni is 1 mmol / L. 2+ The concentration of 2 mmol / L was 8 mL. After the addition was completed, the mixture was kept at 180 °C and stirred for 10 min. After cooling to room temperature, the reactants were washed with cyclohexane and anhydrous ethanol at 3000 r / min for 10 min in sequence. After drying, core-shell structured Pd@PtRuNi nanowires were obtained.

[0053] The SEM and XRD characterization images of the Pd nanowires prepared in step a of this embodiment are shown in Figure 1. The average diameter is 7±1 nm, and the XRD diffraction peaks are consistent with the peak positions of the standard card (#46-1043) of metallic Pd.

[0054] Example 2

[0055] This embodiment provides a method for preparing core-shell structured Pd@PtRuNi nanowires, including the following steps:

[0056] Step 1: Weigh 1g of polyvinylpyrrolidone (average molecular weight 1000-1300000), dissolve 300mg of sodium iodide in 15mL of deionized water, sonicate to dissolve, then add 4mL of 25mmol / L PdCl2 aqueous solution, stir evenly, then transfer to a hydrothermal reactor lined with polytetrafluoroethylene, place in an oven at 190℃ for 155min, cool to room temperature, centrifuge and wash 4 times with a 1:2 volume ratio of anhydrous ethanol and acetone at 8500r / min, dry to obtain Pd nanowires;

[0057] Step 2: Disperse Pd nanowires in benzyl alcohol to obtain a Pd nanowire dispersion with a concentration of 0.3 mg / mL.

[0058] Step 3: Heat the oil bath to 200℃, place a 100mL three-necked flask in it and preheat for 5 minutes. Add 20mL of the prepared Pd nanowire dispersion to the flask and stir for 5 minutes. Slowly add a precursor mixture with a molar ratio of Pt:Ru:Ni = 1:2:1 (solvent is oleylamine and oleic acid with a volume ratio of 2:1, Pt) at a rate of 0.1mL / min. 2+ The concentration was 1.7 mmol / L, Ru 3+ The concentration was 3.4 mmol / L, Ni 2+The concentration of 1.7 mmol / L was 6 mL. After the addition was completed, the mixture was kept at 200 °C and stirred for 10 min. After cooling to room temperature, the reactants were washed with cyclohexane and anhydrous ethanol at 4000 r / min for 10 min in sequence. After drying, core-shell structured Pd@PtRuNi nanowires were obtained.

[0059] The SEM and XRD images of the Pd@PtRuNi nanowires prepared in this embodiment are shown below. Figure 2 As shown in the figure, the Pd@PtRuNi nanowires prepared in this embodiment have a smooth surface, regular morphology, and an average diameter of 9±2 nm. Their XRD diffraction peaks match those of face-centered cubic crystals, and the diffraction peak positions do not coincide with the standard cards of pure metals Pd, Pt, Ru, and Ni, indicating that the metals on the shell surface of the Pd@PtRuNi nanowires prepared in this embodiment exist as alloy phases.

[0060] Example 3

[0061] This embodiment provides a method for preparing core-shell structured Pd@PtRuNi nanowires, including the following steps:

[0062] Step 1: Weigh 1g of polyvinylpyrrolidone (average molecular weight 1000-1300000), dissolve 300mg of sodium iodide in 15mL of deionized water, sonicate to dissolve, then add 4mL of 33mmol / L PdCl2 aqueous solution, stir evenly, then transfer to a hydrothermal reactor lined with polytetrafluoroethylene, place in an oven at 205℃ for 155min, cool to room temperature, centrifuge and wash 4 times with a 1:2 volume ratio of anhydrous ethanol and acetone at 8000r / min, dry to obtain Pd nanowires;

[0063] Step 2: Disperse Pd nanowires in benzyl alcohol to obtain a Pd nanowire dispersion with a concentration of 0.3 mg / mL.

[0064] Step 3: Heat the oil bath to 180℃, place a 100mL three-necked flask in it and preheat for 5min. Add 20mL of the prepared Pd nanowire dispersion to the flask and stir for 5min. Slowly add a precursor mixture with a molar ratio of Pt:Ru:Ni = 2:1:2 (solvent is oleylamine and oleic acid with a volume ratio of 5:3, Pt) at a rate of 0.1mL / min. 2+ The concentration was 2 mmol / L, Ru 3+ The concentration of Ni is 1 mmol / L. 2+ The concentration of 2 mmol / L was 8 mL. After the addition was completed, the mixture was kept at 180 °C and stirred for 10 min. After cooling to room temperature, the reactants were washed with cyclohexane and anhydrous ethanol at 3000 r / min for 10 min in sequence. After drying, core-shell structured Pd@PtRuNi nanowires were obtained.

[0065] The TEM and HRTEM of the Pd@PtRuNi nanowires prepared in this embodiment are as follows: Figure 3 As shown in the figure, the Pd@PtRuNi nanowires prepared in this embodiment have smooth surfaces and lattice spacings of 0.217 nm and 0.133 nm, corresponding to the (111) and (220) crystal planes of Pt, respectively. The TEM and point-measured energy-dispersive X-ray (EDS) spectra of the Pd@PtRuNi nanowires prepared in this embodiment are shown in the figure. Figure 4 As shown in the EDS diagram, the ratio of each element in the shell of the Pd@PtRuNi nanowires prepared in this embodiment is Pt:Ru:Ni = 4.8:3.6:1.0.

[0066] The HAFD pattern and linear scanning energy-dispersive X-ray spectroscopy (EDS) pattern of the Pd@PtRuNi nanowires prepared in this embodiment are shown below. Figure 5 As shown in the figure, the thickness of the shell of the Pd@PtRuNi nanowire is approximately 3 ± 0.4 nm.

[0067] Example 4

[0068] This embodiment provides a method for preparing core-shell structured Pd@PtRuNi nanowires, including the following steps:

[0069] Step 1: Weigh 1g of polyvinylpyrrolidone (average molecular weight 1000-1300000), dissolve 300mg of sodium iodide in 12mL of deionized water, sonicate to dissolve, then add 4mL of 33mmol / L PdCl2 aqueous solution, stir evenly, then transfer to a hydrothermal reactor lined with polytetrafluoroethylene, place in an oven at 205℃ for 155min, cool to room temperature, centrifuge and wash 4 times with a mixture of anhydrous ethanol and acetone with a volume ratio of 1:2 at 9000r / min, dry to obtain Pd nanowires;

[0070] Step 2: Disperse Pd nanowires in benzyl alcohol to obtain a 0.2 mg / mL Pd nanowire dispersion;

[0071] Step 3: Heat the oil bath to 190℃, place a 100mL three-necked flask in it and preheat for 5min. Add 20mL of the prepared Pd nanowire dispersion to the flask and stir for 5min. Slowly add a precursor mixture with a molar ratio of Pt:Ru:Ni = 2:1:2 (solvent is oleylamine and oleic acid with a volume ratio of 5:3, Pt) at a rate of 0.1mL / min. 2+ The concentration was 1.8 mmol / L, Ru 3+ The concentration was 0.9 mmol / L, Ni 2+The concentration of 1.8 mmol / L was 8 mL. After the addition was completed, the mixture was kept at 190 °C and stirred for 10 min. After cooling to room temperature, the reactants were washed with cyclohexane and anhydrous ethanol at 3000 r / min for 10 min in sequence. After drying, core-shell structured Pd@PtRuNi nanowires were obtained.

[0072] Example 5

[0073] This embodiment provides a method for preparing core-shell structured Pd@PtRuNi nanowires, including the following steps:

[0074] Step 1: Weigh 1g of polyvinylpyrrolidone (average molecular weight 1000-1300000), dissolve 300mg of sodium iodide in 18mL of deionized water, sonicate to dissolve, then add 4mL of 33mmol / L PdCl2 aqueous solution, stir evenly, then transfer to a hydrothermal reactor lined with polytetrafluoroethylene, place in an oven at 190℃ for 160min, cool to room temperature, centrifuge and wash 4 times with a mixture of anhydrous ethanol and acetone with a volume ratio of 1:2 at 9000r / min, dry to obtain Pd nanowires;

[0075] Step 2: Disperse Pd nanowires in benzyl alcohol to obtain a 0.5 mg / mL Pd nanowire dispersion;

[0076] Step 3: Heat the oil bath to 180℃, place a 100mL three-necked flask in it and preheat for 5min. Add 20mL of the prepared Pd nanowire dispersion to the flask and stir for 5min. Slowly add a precursor mixture with a molar ratio of Pt:Ru:Ni = 2:1:2 (solvent is oleylamine and oleic acid with a volume ratio of 5:3, Pt) at a rate of 0.1mL / min. 2+ The concentration was 2 mmol / L, Ru 3+ The concentration of Ni is 1 mmol / L. 2+ The concentration of 2 mmol / L was 8 mL. After the addition was completed, the mixture was kept at 180 °C and stirred for 10 min. After cooling to room temperature, the reactants were washed with cyclohexane and anhydrous ethanol at 3000 r / min for 10 min in sequence. After drying, core-shell structured Pd@PtRuNi nanowires were obtained.

[0077] Example 6

[0078] This embodiment provides a method for preparing core-shell structured Pd@PtRuNi nanowires, including the following steps:

[0079] Step 1: Weigh 1g of polyvinylpyrrolidone (average molecular weight 1000-1300000), dissolve 300mg of sodium iodide in 15mL of deionized water, sonicate to dissolve, then add 6mL of 25mmol / L Na2PdCl4 aqueous solution, stir evenly, then transfer to a hydrothermal reactor lined with polytetrafluoroethylene, place in an oven at 215℃ for 150min, cool to room temperature, centrifuge and wash 4 times with a 1:2 volume ratio of anhydrous ethanol and acetone at 9000r / min, dry to obtain Pd nanowires;

[0080] Step 2: Disperse Pd nanowires in benzyl alcohol to obtain a Pd nanowire dispersion with a concentration of 0.4 mg / mL.

[0081] Step 3: Heat the oil bath to 180℃, place a 100mL three-necked flask in it and preheat for 5min. Add 20mL of the prepared Pd nanowire dispersion to the flask and stir for 5min. Slowly add a precursor mixture with a molar ratio of Pt:Ru:Ni = 2:1:2 (solvent is oleylamine and oleic acid with a volume ratio of 5:3, Pt) at a rate of 0.1mL / min. 2+ The concentration was 2 mmol / L, Ru 3+ The concentration of Ni is 1 mmol / L. 2+ The concentration of 2 mmol / L was 8 mL. After the addition was completed, the mixture was kept at 180 °C and stirred for 10 min. After cooling to room temperature, the reactants were washed with cyclohexane and anhydrous ethanol at 3000 r / min for 10 min in sequence. After drying, core-shell structured Pd@PtRuNi nanowires were obtained.

[0082] The precursor mixture in Examples 1-6 above is a mixed solution of Pt(acac)2, Ru(acac)3 and Ni(acac)2.

[0083] Comparative Example 1

[0084] This comparative example provides a method for preparing Pd@PtRuCu nanowires, which is exactly the same as that in Example 1, except that Ni(acac)2 in step three of Example 3 is replaced with an equimolar amount of Ni(acac)2, and the other steps are exactly the same.

[0085] Comparative Example 2

[0086] This comparative example provides a method for preparing Pd@PtRhCu nanowires, which is exactly the same as that in Example 1. The only difference is that Ni(acac)2 in step 3 of Example 3 is replaced with an equimolar amount of Ni(acac)2, and Ru(acac)3 is replaced with an equimolar amount of Rh(acac)3. The remaining steps are exactly the same.

[0087] Comparative Example 3

[0088] This comparative example provides a method for preparing Pd@PtRhNi nanowires, which is exactly the same as that in Example 1. The only difference is that Ru(acac)3 in step three of Example 3 is replaced with an equimolar amount of Rh(acac)3. The other steps are exactly the same.

[0089] Comparative Example 4

[0090] This comparative example provides a method for preparing Pd@Ru nanowires, which is exactly the same as that in Example 1. The only difference is that in step three of Example 3, Pt(acac)2, Ru(acac)3 and Ni(acac)2 are all replaced with an equimolar amount of Ru(acac)3. The other steps are exactly the same.

[0091] Comparative Example 5

[0092] This comparative example provides a method for preparing Pd@Pt nanowires, which is exactly the same as that in Example 1, except that Ru(acac)3 and Ni(acac)2 in Example 3 are replaced with equimolar amounts of Pt(acac)2, and the other steps are exactly the same.

[0093] Performance testing

[0094] The material properties were tested using a rotating disk electrode apparatus (PINECPR, USA) and an electrochemical workstation (Shanghai Chenhua CHI760E) according to conventional half-cell testing methods in the field. The specific methods are as follows:

[0095] The core-shell structured Pd@PtRuNi nanowires prepared in Example 3 of this invention were mixed with XC-72 carbon support at a mass ratio of 1:4 (metal content 20%). Then, 1 mg of the mixed sample was dispersed in 1 mL of solvent (ultrapure water: isopropanol: 5% perfluorosulfonic acid polymer solution = 1:1:0.008, v:v:v) and ultrasonically dispersed for 30 min to obtain electrode slurry.

[0096] Following the same method described above, the Pd@PtRuCu nanowires, Pd@PtRhCu nanowires, Pd@PtRhNi nanowires, Pd@Ru nanowires, and Pd@Pt nanowires prepared in Comparative Examples 1-5 were composited with XC-72 carbon support in the same proportion to prepare corresponding electrode slurries.

[0097] The corresponding electrode slurry was prepared by combining commercial platinum-carbon catalysts (20% Pt content) in the same proportion.

[0098] Take 10 μL of the uniformly dispersed electrode slurry and drop it onto a glassy carbon electrode with a diameter of 0.5 cm. Perform cyclic voltammetry and linear sweep voltammetry (scan rate 50 mV / s) in a nitrogen-saturated 0.1 mol / L KOH electrolyte, within the range of 0.05 V–1.2 V (relative to the hydrogen standard electrode). Figure 6 and Figure 7 As shown in the figure, the results demonstrate that the half-wave potential of Pd@PtRuNi nanowires is significantly positively shifted compared to Pd@Ru nanowires, Pd@Pt nanowires, and commercial platinum-carbon nanowires. Compared to Pd@PtRuCu nanowires, Pd@PtRhCu nanowires, and Pd@PtRhNi nanowires, the Pt-O reduction peak of Pd@PtRuNi nanowires is the most positive, indicating that the combination of Pt, Ru, and Ni elements can minimize the interaction between Pt sites and oxygen intermediates. Comparison of linear sweep voltammetry curves shows that the half-wave potential of Pd@PtRuNi nanowires is the most positive, indicating that the combination of Pt, Ru, and Ni elements can significantly enhance catalytic activity.

[0099] The content of each metal element in the slurry of each electrode was determined by inductively coupled plasma spectroscopy. Then, the mass activity at 0.9 V was calculated using the mass of platinum and the Koutechy-Levich equation. The results are shown in Table 1.

[0100] Koutechy-Levich equation: 1 / j m =1 / j k +1 / j l

[0101] Where: j m The current density obtained from the test; j k j is the dynamic current density; l This represents the limiting current density.

[0102] Table 1

[0103]

[0104] See Figure 8 After cycling the Pd@PtRuNi nanowires prepared in Example 3 of this invention for 15,000 and 30,000 cycles under the same conditions as described above, their mass activity at 0.9 V was 1.28 A / mg. Pt and 1.16A / mg Pt The activity level still exceeds the target parameters for fuel cell production set by the U.S. Department of Energy for 2025 (activity level greater than 0.44 A / mg). PtMeanwhile, the mass activity decay after 30,000 cycles is 15.94%, which is also higher than the US Department of Energy's 2025 target mass activity decay for fuel cell operating characteristic parameters (mass activity decay of less than 40% after 30,000 cycles).

[0105] The above results demonstrate that the Pd@PtRuNi nanowire material prepared in the embodiments of the present invention exhibits excellent catalytic activity when applied to the redox reaction of the cathode in a fuel cell. Its mass activity is 5.31 times that of commercially available platinum-carbon catalysts. After 30,000 cycles, the mass activity decreases by 15.94%, still 4.46 times that of commercial platinum-carbon catalysts. This shows that the Pd@PtRuNi nanowire material prepared in the embodiments of the present invention has extremely high utilization of Pt atoms.

[0106] See also Figure 9 The Pd@PtRuNi nanowire material prepared in Example 3 did not change its morphology after 30,000 cycles, indicating that the Pd@PtRuNi nanowire material provided by the present invention has extremely high cycling stability.

[0107] Similarly, 10 μL of the uniformly dispersed electrode slurry was drop-coated onto a glassy carbon electrode with a diameter of 0.5 cm. Cyclic voltammetry was then performed in a nitrogen-saturated KOH and methanol electrolyte solution (KOH concentration 0.1 mol / L, methanol concentration 0.5 mol / L) within the range of 0.05 V–1.2 V (relative to the hydrogen standard electrode). Figure 10 As shown in the figure, the onset potential of Pd@PtRuNi nanowires is lower than that of Pd@Ru nanowires, indicating that the construction of the Ru alloy shell can effectively reduce the potential of the methanol oxidation reaction and promote its efficient execution. Furthermore, the Pt content in each catalyst was determined by inductively coupled plasma spectroscopy, and the current density at the pre-scan peak in the methanol oxidation cyclic voltammetry curve was calculated. The results are shown in Table 2.

[0108] Table 2

[0109]

[0110] The material in Example 3 of this invention exhibited excellent catalytic activity during the methanol oxidation reaction at the anode of a fuel cell, with a mass activity of 1.46 A / mg. Pt At the same potential, the activity of commercially available platinum-carbon catalysts is 0.427 A / mg. Pt 3.18 times that of ).

[0111] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing core-shell structured Pd@PtRuNi nanowires, characterized in that, Includes the following steps: Step a, prepare Pd nanowires; Step b: Disperse the Pd nanowires in an organic solvent to obtain a Pd nanowire dispersion; then disperse the Pt nanowires in an organic solvent. 2+ Ru 3+ and Ni 2+ The precursor solution was mixed evenly with the Pd nanowire dispersion and reacted at 180℃-200℃ for 1h-2h. After cooling, washing, and drying, core-shell structured Pd@PtRuNi nanowires were obtained. In step b, the concentration of the Pd nanowire dispersion is 0.2-0.5 mg / mL; the Pt in the precursor solution... 2+ Ru 3+ and Ni 2+ The molar ratio is 2:1:2-1:2:1; the solvent of the precursor solution is a mixture of oleylamine and oleic acid with a volume ratio of 2:1-5:

3. The core-shell structured Pd@PtRuNi nanowires include a Pd nanowire core layer and a PtRuNi alloy layer covering the outside of the Pd nanowires.

2. The method for preparing core-shell structured Pd@PtRuNi nanowires as described in claim 1, characterized in that, Step a specifically includes the following steps: Polyvinylpyrrolidone and sodium iodide were dissolved in water to obtain a mixed solution; Pd salt aqueous solution was added to the mixed solution, and the mixture was subjected to hydrothermal reaction at 190℃-215℃ for 150min-160min, cooled, washed, and dried to obtain Pd nanowires.

3. The method for preparing core-shell structured Pd@PtRuNi nanowires as described in claim 2, characterized in that, The mass ratio of the polyvinylpyrrolidone to water is 1:12-18; and / or The mass ratio of sodium iodide to water is 0.3:12-18.

4. The method for preparing core-shell structured Pd@PtRuNi nanowires as described in claim 3, characterized in that, The concentration of the Pd salt aqueous solution is 25 mmol / L-33 mmol / L, and its volume ratio with the mixed solution is 3-6:12-18.

5. The method for preparing core-shell structured Pd@PtRuNi nanowires as described in claim 1, characterized in that, In step b, the organic solvent is benzyl alcohol.

6. The method for preparing core-shell structured Pd@PtRuNi nanowires as described in claim 5, characterized in that, In step b, the precursor solution is a mixed solution of Pt(acac)2, Ru(acac)3, and Ni(acac)2, wherein Pt 2+ The concentration was 1.7 mmol / L-2 mmol / L, Ru 3+ The concentration of Ni ranged from 0.9 mmol / L to 3.4 mmol / L. 2+ The concentration was 1.7 mmol / L-2 mmol / L; and / or In step b, the volume ratio of the Pd nanowire dispersion to the precursor solution is 1:2.5-3.

5.

7. A core-shell structured Pd@PtRuNi nanowire, characterized in that, The Pd@PtRuNi nanowires with a core-shell structure are prepared by the method described in any one of claims 1-6, comprising a Pd nanowire core layer and a PtRuNi alloy layer covering the outside of the Pd nanowires.

8. The core-shell structured Pd@PtRuNi nanowires as described in claim 7, characterized in that, The core-shell structured Pd@PtRuNi nanowires have a diameter of 7nm-17nm and a length of 100nm-500nm.

9. The core-shell structured Pd@PtRuNi nanowire as described in claim 7, characterized in that, The thickness of the PtRuNi alloy layer is 2.6nm-3.4nm, wherein the atomic ratio of Pt, Ru, and Ni is 4.8:3.6:

1.

10. The application of the core-shell structured Pd@PtRuNi nanowires according to any one of claims 7-8 as a catalyst in the catalytic oxygen reduction reaction at the cathode or the catalytic methanol oxidation reaction at the anode of a fuel cell.

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