A PtCo@PtIr octahedral core-shell nanoparticle and its preparation method and application

Abstract

The present invention proposes PtCo@PtIr octahedral core-shell nanoparticles, their preparation method, and applications. The PtCo@PtIr octahedral core-shell nanoparticles have a core-shell structure formed by epitaxially growing a PtIr shell on PtCo intermetallic compound nanoparticles. As electrocatalysts, the PtCo@PtIr octahedral core-shell nanoparticles of the present invention exhibit superior oxygen reduction reaction (ORR) performance compared to commercial Pt / C, with higher catalytic activity and resistance to poisoning, enabling the catalyst to maintain high ORR performance over a long period of time. The addition of the PtIr bimetallic shell imparts dual functionality to the catalyst for both the oxygen reduction reaction and the oxygen evolution reaction (OER). Compared to commercial Pt / C, the atomically ordered PtCo core and compressively strained PtIr shell structure in these nanoparticles offer excellent electrocatalytic performance and stability.

Description

Technical Field

[0001] The present invention relates to the field of electrocatalysts, and in particular to PtCo@PtIr octahedral core-shell nanoparticles and a preparation method and application thereof. Background Art

[0002] Platinum-based nanomaterials are the most mature electrocatalysts, having been demonstrated in several key reactions in industrial energy conversion devices. However, their scarce reserves and high price have been obstacles to their large-scale use in practical applications. Alloying platinum with relatively inexpensive transition metal elements is a simple and effective strategy that can both reduce catalyst material cost and enhance catalytic performance through ligand and strain effects.

[0003] The core-shell structure is an excellent electrocatalyst design. By concentrating the active metal and reaction sites in the structural shell, it greatly improves the utilization rate of precious metals. At the same time, the strain effect based on the lattice mismatch between the core and shell is also an important way to regulate catalytic performance. However, the current common core-shell structure uses disordered nanoalloys as the core material, which makes the catalyst suffer from transition metal dissolution in acidic environments, greatly limiting the catalyst's high catalytic efficiency and reaction durability. Therefore, nanocrystalline catalytic materials based on intermetallic compounds (IMCs) have been proposed.

[0004] In IMC nanocrystals, the orderly arrangement strengthens the bonding of atoms, making the core-shell structure exhibit excellent durability. As the site directly involved in the catalytic reaction, the adjustment of the shell's composition can help achieve specific catalytic functions. For example, the participation of OER active species in the composition of the shell can improve the OER performance of platinum metal, which does not have an advantage. In this way, the catalyst will exhibit the dual functions of ORR-OER (oxygen reduction reaction-oxygen evolution reaction), which will be conducive to its leap in application.

[0005] In core-shell structures, the diversification of catalytic functions through fine-tuning of shell composition has not yet been studied. Most studies have only used core-shell structure design to enhance the performance of a single oxygen reduction, oxygen evolution, or hydrogen evolution reaction (for example, Pd@Pt, PtCo@Pt, PtCo@PtSn, etc., all have good catalytic performance for a single function). Therefore, using intermetallic compounds to complete the precise construction of nanomaterials and obtain nanocatalysts with excellent activity, durability, and multifunctionality is a very urgent research issue. Summary of the Invention

[0006] The present invention provides a PtCo@PtIr octahedral core-shell nanoparticle and a preparation method and application thereof. The prepared PtCo@PtIr octahedral core-shell nanoparticle has excellent ORR and OER catalytic activity as an electrocatalyst, and has excellent electrochemical stability.

[0007] The technical solution of the present invention is achieved as follows: a PtCo@PtIr octahedral core-shell nanoparticle, wherein the PtCo@PtIr octahedral core-shell nanoparticle has a PtCo intermetallic compound nanoparticle as a core and a bimetallic PtIr as a shell.

[0008] Furthermore, the size of PtCo@PtIr octahedral core-shell nanoparticles is 8-10 nm.

[0009] Furthermore, the thickness of the PtIr shell is 2 to 4 atomic layers.

[0010] A method for preparing PtCo@PtIr octahedral core-shell nanoparticles. The PtCo@PtIr octahedral core-shell nanoparticles are prepared by epitaxially growing a PtIr shell layer on PtCo intermetallic compound nanoparticles.

[0011] Furthermore, the preparation method comprises the following steps:

[0012] (1) dispersing a metal precursor, a capping agent, and a reducing agent I in a solvent I to obtain a solution A, wherein the metal precursor includes a platinum source and a cobalt source;

[0013] (2) heating solution A under argon gas to react, and then naturally cooling to room temperature to obtain solution B;

[0014] (3) Centrifuging solution B to obtain an intermediate product, washing the intermediate product, and dispersing it in n-hexane to obtain solution C;

[0015] (4) mixing carbon black, n-hexane, and solution C with ultrasonication, washing, and drying under vacuum to obtain PtCo alloy nanoparticles;

[0016] (5) annealing the PtCo alloy nanoparticles and naturally cooling them to room temperature to obtain PtCo intermetallic compound nanoparticles;

[0017] (6) PtCo intermetallic compound nanoparticles and reducing agent II are dispersed in solvent II, and a shell metal precursor is slowly added. After centrifugation and washing, the mixture is dried in a vacuum environment to obtain PtCo@PtIr octahedral core-shell nanoparticles. The shell metal precursor includes a platinum source and an iridium source.

[0018] Furthermore, in step (1), the metal precursor includes platinum acetylacetonate and cobalt acetylacetonate, the capping agent is tungsten hexacarbonyl, the reducing agent I is oleylamine, and the solvent I is benzyl alcohol; the amount of platinum acetylacetonate is 10-20 mg, the amount of cobalt acetylacetonate is 10-20 mg, the amount of the capping agent is 75-150 mg, the amount of the reducing agent I is 3-6 mL, and the volume of the solvent I is 7-14 mL.

[0019] Furthermore, in step (6), the reducing agent II is citric acid, the solvent II is deionized water, the shell metal precursor includes a platinum source and an iridium source, the platinum source is sodium hexachloroplatinate (IV) or potassium hexachloroplatinate (IV), and the iridium source is sodium hexachloroiridate (III) or potassium hexachloroiridate (III); the amount of PtCo intermetallic compound nanoparticles is 10-20 mg, the amount of reducing agent II is 30-60 mg, the amount of solvent II is 5-10 mL, the amount of platinum source is 1-3.5 mg, and the amount of iridium source is 1-3.5 mg. The platinum source and the iridium source are dissolved in deionized water, such as the total mass of the platinum source and the iridium source is 4.5 mg, which is dissolved in 1.5 mL of deionized water, and then injected at an injection rate of 0.1 mL / h.

[0020] Furthermore, in step (2), the heating reaction temperature is 60-200° C., and the reaction time is 40-120 minutes.

[0021] Furthermore, in step (1), dispersion is performed by ultrasound, and the ultrasound time is not less than 5 minutes; in step (3), the specific method for washing the intermediate product is: the intermediate product is dispersed in ethanol and acetone by ultrasound, and then centrifuged and precipitated, and repeated 1-2 times.

[0022] PtCo@PtIr octahedral core-shell nanoparticles are prepared by the method.

[0023] Application of PtCo@PtIr octahedral core-shell nanoparticles as electrocatalysts.

[0024] Beneficial effects of the present invention:

[0025] The PtCo@PtIr octahedral core-shell nanoparticles of the present invention are core-shell structures formed by epitaxially growing a PtIr shell on PtCo intermetallic compound nanoparticles. The size of the PtCo@PtIr octahedral core-shell nanoparticles is 8-10 nanometers. The atomically ordered PtCo core and the compressively strained PtIr shell structure in the PtCo@PtIr octahedral core-shell nanoparticles can provide abundant active sites in electrocatalytic reactions and have very good ORR and OER catalytic performance.

[0026] The preparation method of the present invention is an oil bath method, which is simple to operate, has good repeatability and high yield; in the same system, changing the reaction conditions can achieve controllable regulation of catalyst components, etc., which is a simple and efficient preparation method.

[0027] The PtCo@PtIr octahedral core-shell nanoparticles of the present invention are used in catalyzing the cathode reaction - oxygen reduction reaction (ORR) in zinc-air batteries. The ORR performance of the nanoparticles is better than that of commercial Pt / C, and the half-wave potential is 63mV higher than that of commercial Pt / C. The nanoparticles have higher catalytic activity and anti-poisoning ability, and can maintain high ORR performance for a long time. At the same time, the OER performance of the nanoparticles in catalyzing the anode reaction - oxygen evolution reaction in zinc-air batteries is better than that of PtCo@Pt core-shell nanoparticles. At 10mAcm -2 The overpotential at 100 nm is reduced by more than 144 mV compared to PtCo@Pt core-shell nanoparticles, demonstrating higher OER catalytic activity. Compared to commercial Pt / C nanoparticles, the bimetallic PtIr shell structure of these nanoparticles provides excellent electrocatalytic performance and stability. Furthermore, the PtCo@PtIr octahedral core-shell nanoparticles of this invention also perform well in catalyzing other electrochemical reactions, such as methanol oxidation, ethanol oxidation, ethylene glycol oxidation, hydrogen evolution reaction, and perhydrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 Schematic diagram of the preparation process of PtCo@PtIr octahedral core-shell nanoparticles of the present invention;

[0030] Figure 2 The morphology of PtCo@PtIr octahedral core-shell nanoparticles;

[0031] Figure 3 The structural diagram of PtCo@PtIr octahedral core-shell nanoparticles;

[0032] Figure 4 The test curves for oxygen reduction reaction catalyzed by PtCo@PtIr octahedral core-shell nanoparticles (fct-PtCo@PtIr / C), PtCo intermetallic compound nanoparticles (fct-PtCo / C), PtCo alloy nanoparticles (fcc-PtCo / C) and commercial Pt / C;

[0033] Figure 5 The test curves of oxygen evolution reaction catalyzed by PtCo@PtIr octahedral core-shell nanoparticles (fct-PtCo@PtIr / C) and PtCo@Pt core-shell nanoparticles (fct-PtCo@Pt / C);

[0034] Figure 6 Linear sweep voltammetry curves of PtCo@PtIr octahedral core-shell nanoparticles before and after 10,000 cycles of catalytic oxygen reduction reaction. DETAILED DESCRIPTION

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] like Figure 1 As shown, a method for preparing PtCo@PtIr octahedral core-shell nanoparticles comprises the following steps:

[0038] (1) 20 mg of platinum acetylacetonate, 20 mg of cobalt acetylacetonate, and 150 mg of tungsten hexacarbonyl were weighed and placed in a flask. 6 mL of oleylamine and 14 mL of benzyl alcohol were then added to the flask. The mixture was magnetically stirred under an argon atmosphere for 5 minutes to obtain solution A.

[0039] (2) heating solution A to 60°C and maintaining it for 30 minutes, then rapidly heating it to 200°C and maintaining it for 40 minutes to obtain solution B;

[0040] (3) Solution B was centrifuged to obtain an intermediate product, which was washed with ethanol and acetone and then dispersed in 10 mL of n-hexane to obtain solution C;

[0041] (4) 40 mg of carbon black, 40 mL of n-hexane, and solution C were mixed by ultrasonication, centrifuged, and then dried in a vacuum drying oven to obtain PtCo alloy nanoparticles;

[0042] (5) annealing the PtCo alloy nanoparticles at 600°C for 4 hours in a tube furnace filled with 96% argon and 4% hydrogen, and then naturally cooling to room temperature to obtain PtCo intermetallic compound nanoparticles;

[0043] (6) 10 mg of PtCo intermetallic compound nanoparticles and 30 mg of citric acid were dispersed in 5 mL of deionized water. 1.5 mL of the shell metal precursor (3 mg / mL) was injected at a rate of 0.1 mL / h using a syringe pump. The reaction was continued for 9 hours after the injection. The mixture was naturally cooled, centrifuged, and washed to obtain PtCo@PtIr octahedral core-shell nanoparticles. The shell metal precursor was 1 mg of sodium hexachloroplatinate (IV) and 3.5 mg of sodium hexachloroiridate (III) dissolved in 1.5 mL of deionized water. The PtCo@PtIr octahedral core-shell nanoparticles were placed in a vacuum drying oven and stored at room temperature.

[0044] Figure 2 The morphology of the PtCo@PtIr octahedral core-shell nanoparticles prepared in this example (transmission electron micrograph). Figure 2 As can be seen in (a), the PtCo@PtIr octahedral core-shell nanoparticles are well dispersed on the carbon support and the particle size is 8-10 nm. Figure 2 As can be seen from (b) and (c), the PtCo@PtIr core-shell nanoparticles have an octahedral shape with exposed {111} crystal faces. At the same time, Fourier transform also confirms that the core-shell nanoparticles are face-centered tetragonal structures ( Figure 2 (c) Upper right illustration). Figure 2 As can be seen in (d-g), Pt is uniformly distributed, Co is relatively concentrated in the center, and Ir is primarily distributed on the surface, confirming that the PtCo@PtIr octahedral core-shell nanoparticles are composed of an intermetallic PtCo core and a bimetallic PtIr shell. The atomically ordered PtCo core and compressively strained PtIr shell structure in the PtCo@PtIr octahedral core-shell nanoparticles enhance the catalytic activity and stability during the reaction.

[0045] Figure 3 This is the structural spectrum (X-ray diffraction spectrum) of the PtCo@PtIr octahedral core-shell nanoparticles prepared in this embodiment. Compared with pure Pt, the diffraction peak of the PtCo alloy nanoparticles (fcc-PtCo / C) shifts to a larger angle, which is due to the doping of Co atoms into the face-centered cubic Pt lattice. After the fcc-PtCo / C nanoparticles were treated at 600°C, the diffraction peak was significantly shifted to the right, matching the standard fct-PtCo (JCPDS#65-8969), indicating that PtCo was transformed from a random alloy into a PtCo intermetallic compound (fct-PtCo / C). The subsequent co-deposition of a platinum-iridium shell on the fct-PtCo nanoparticles caused the diffraction peak to shift slightly to the left, which was mainly attributed to the addition of the platinum-iridium shell.

[0046] Comparative Example 1

[0047] The preparation method of fcc-PtCo / C comprises the following steps: 20 mg of platinum acetylacetonate, 20 mg of cobalt acetylacetonate, and 100 mg of tungsten hexacarbonyl are weighed and placed in a flask, 6 mL of oleylamine and 14 mL of benzyl alcohol are added to the flask, the temperature is raised to 60°C and maintained for 20 minutes, and then the temperature is adjusted to 10°C min -1 The temperature was raised to 200°C and maintained for 40 minutes, naturally cooled, centrifuged, and washed. The washed PtCo nanoparticles and carbon black were dispersed in n-hexane and ultrasonicated for 3 hours to obtain fcc-PtCo / C.

[0048] Comparative Example 2

[0049] The preparation method of fct-PtCo / C comprises the following steps: weighing fcc-PtCo / C and placing it in a quartz boat, then placing it in a tube furnace filled with 96% argon and 4% hydrogen, maintaining it at 600°C for 4 hours, and naturally cooling it to obtain fct-PtCo / C.

[0050] Comparative Example 3

[0051] The preparation method of Wct-PtCo@Pt / C includes the following steps: taking 5 mL of Wct-PtCo / C suspension (0.2 mg mL - 1 Pt) and 30 mg of citric acid were mixed and ultrasonicated for 5 minutes, then placed in an 80°C oil bath for preheating for 10 minutes, and 1.5 mL of shell metal precursor (3 mg / mL) was injected at a rate of 0.1 mL / h using a syringe pump. After the injection, the reaction was continued for 9 hours, naturally cooled, centrifuged, and washed to obtain PtCo@Pt core-shell nanoparticles. The shell metal precursor was a platinum source, and the platinum source was potassium hexachloroplatinate (IV) with a mass of 4.5 mg, which was dissolved in 1.5 ml of deionized water.

[0052] Figure 4 The results are shown for the oxygen reduction reaction (ORR) catalyzed by the PtCo@PtIr octahedral core-shell nanoparticles (fct-PtCo@PtIr / C) prepared in this example, the fct-PtCo / C of Comparative Example 2, the fcc-PtCo / C of Comparative Example 1, and commercial Pt / C electrocatalysts. The commercial Pt / C was purchased from Shanghai Hesen Electric Co., Ltd., model: HPT040. The test environment was based on a three-electrode system of an electrochemical workstation. Figure 4 (a) Cyclic voltammetry was used to test the electrolyte solution with a concentration of 0.1 M HClO4. Figure 4(b) Using linear sweep voltammetry, the test was carried out in an O2-saturated, 0.1M HClO4 electrolyte solution, with the electrode rotation speed maintained at 1600 rpm. From the test results, it can be seen that the half-wave potentials of fct-PtCo@PtIr / C, fct-PtCo / C, fcc-PtCo / C and commercial Pt / C are 0.835V, 0.816V, 0.796V, and 0.772V (vs.RHE), respectively. The half-wave potential of PtCo@PtIr octahedral core-shell nanoparticles is significantly improved compared to PtCo intermetallic compound nanoparticles and PtCo alloy nanoparticles, and is 63mV higher than that of commercial Pt / C.

[0053] Figure 5 The test results of the oxygen evolution reaction catalyzed by the PtCo@PtIr octahedral core-shell nanoparticles (wct-PtCo@PtIr / C) prepared in this embodiment and the wct-PtCo@Pt / C electrocatalyst of comparative example 3 were obtained. The test environment was based on a three-electrode system of an electrochemical workstation, using linear sweep voltammetry technology. The test was carried out in an electrolyte solution saturated with O2 and having a concentration of 0.1M HClO4, and the electrode speed was maintained at 1600 rpm. As can be seen from the test results, the PtCo@PtIr octahedral core-shell nanoparticles have a high conductivity at 10mA cm -2 The overpotential at 144 mV is reduced compared with that of PtCo@Pt core-shell nanoparticles, indicating a higher OER catalytic activity. This indicates that the PtCo@PtIr octahedral core-shell nanoparticles prepared by this method have excellent dual functionality for oxygen reduction and oxygen evolution.

[0054] like Figure 6 Shown are the polarization curves of the PtCo@PtIr octahedral core-shell nanoparticles prepared in this example before and after 10,000 electrochemical cycles. After 10,000 cycles, the half-wave potential of the prepared PtCo@PtIr octahedral core-shell nanoparticles only decreased by 12 mV, indicating that the PtCo@PtIr octahedral core-shell nanoparticles prepared by this method have excellent electrochemical stability.

[0055] Example 2

[0056] like Figure 1 As shown, a method for preparing PtCo@PtIr octahedral core-shell nanoparticles comprises the following steps:

[0057] (1) Weigh 20 mg of platinum acetylacetonate, 20 mg of cobalt acetylacetonate, and 100 mg of tungsten hexacarbonyl into a flask, then add 6 mL of oleylamine and 14 mL of benzyl alcohol to the flask to obtain solution A;

[0058] (2) heating solution A to 60°C and maintaining it for 30 minutes, then rapidly heating it to 200°C and maintaining it for 40 minutes to obtain solution B;

[0059] (3) Solution B was centrifuged to obtain an intermediate product, which was washed with ethanol and acetone and then dispersed in 10 mL of n-hexane to obtain solution C;

[0060] (4) 40 mg of carbon black, 40 mL of n-hexane, and solution C were mixed by ultrasonication, centrifuged, and then dried in a vacuum drying oven to obtain PtCo alloy nanoparticles;

[0061] (5) annealing the PtCo alloy nanoparticles at 600°C for 4 hours in a tube furnace filled with 96% argon and 4% hydrogen, and then naturally cooling to room temperature to obtain PtCo intermetallic compound nanoparticles;

[0062] (6) 10 mg of PtCo intermetallic compound nanoparticles and 30 mg of citric acid were dispersed in 5 mL of deionized water. 1.5 mL of the shell metal precursor (3 mg / mL) was injected at a rate of 0.1 mL / h using a syringe pump. After the injection, the reaction was continued for 9 hours. The mixture was naturally cooled, centrifuged, and washed to obtain PtCo@PtIr octahedral core-shell nanoparticles. The shell metal precursors were sodium hexachloroplatinate (IV) and sodium hexachloroiridate (III). Sodium hexachloroplatinate (IV) was 1 mg, and sodium hexachloroiridate (III) was 3.5 mg. They were dissolved in 1.5 mL of deionized water for injection. The PtCo@PtIr octahedral core-shell nanoparticles were placed in a vacuum drying oven and stored at room temperature.

[0063] Example 3

[0064] like Figure 1 As shown, a method for preparing PtCo@PtIr octahedral core-shell nanoparticles comprises the following steps:

[0065] (1) 20 mg of platinum acetylacetonate, 20 mg of cobalt acetylacetonate, and 150 mg of tungsten hexacarbonyl were weighed and placed in a flask. 6 mL of oleylamine and 14 mL of benzyl alcohol were then added to the flask. The mixture was magnetically stirred under an argon atmosphere for 5 minutes to obtain solution A.

[0066] (2) heating solution A to 70°C and maintaining it for 30 minutes, then rapidly heating it to 200°C and maintaining it for 30 minutes to obtain solution B;

[0067] (3) Solution B was centrifuged to obtain an intermediate product, which was washed with ethanol and acetone and then dispersed in 10 mL of n-hexane to obtain solution C;

[0068] (4) 40 mg of carbon black, 40 mL of n-hexane, and solution C were mixed by ultrasonication, centrifuged, and then dried in a vacuum drying oven to obtain PtCo alloy nanoparticles;

[0069] (5) annealing the PtCo alloy nanoparticles at 600°C for 4 hours in a tube furnace filled with 96% argon and 4% hydrogen, and then naturally cooling to room temperature to obtain PtCo intermetallic compound nanoparticles;

[0070] (6) 10 mg of PtCo intermetallic compound nanoparticles and 30 mg of citric acid were dispersed in 5 mL of deionized water. 1.5 mL of the shell metal precursor (3 mg / mL) was injected at a rate of 0.1 mL / h using a syringe pump. After the injection, the reaction was continued for 9 hours. The mixture was naturally cooled, centrifuged, and washed to obtain PtCo@PtIr octahedral core-shell nanoparticles. The shell metal precursors were potassium hexachloroplatinate (IV) and potassium hexachloroiridate (III). Potassium hexachloroplatinate (IV) was 2.3 mg, and potassium hexachloroiridate (III) was 2.2 mg. They were dissolved in 1.5 mL of deionized water for injection. The PtCo@PtIr octahedral core-shell nanoparticles were placed in a vacuum drying oven and stored at room temperature.

[0071] Example 4

[0072] like Figure 1 As shown, a method for preparing PtCo@PtIr octahedral core-shell nanoparticles comprises the following steps:

[0073] (1) Weigh 10 mg of platinum acetylacetonate, 10 mg of cobalt acetylacetonate, and 75 mg of tungsten hexacarbonyl into a flask, then add 3 mL of oleylamine and 7 mL of benzyl alcohol to the flask to obtain solution A;

[0074] (2) heating solution A to 60°C and maintaining it for 30 minutes, then rapidly heating it to 200°C and maintaining it for 40 minutes to obtain solution B;

[0075] (3) Solution B was centrifuged to obtain an intermediate product, which was washed with ethanol and acetone and then dispersed in 5 mL of n-hexane to obtain solution C;

[0076] (4) 20 mg of carbon black, 20 mL of n-hexane, and solution C were mixed by ultrasonication, centrifuged, and then dried in a vacuum drying oven to obtain PtCo alloy nanoparticles;

[0077] (5) annealing the PtCo alloy nanoparticles at 600°C for 4 hours in a tube furnace filled with 96% argon and 4% hydrogen, and then naturally cooling to room temperature to obtain PtCo intermetallic compound nanoparticles;

[0078] (6) 10 mg of PtCo intermetallic compound nanoparticles and 30 mg of citric acid were dispersed in 5 mL of deionized water. 1.5 mL of shell metal precursor (3 mg / mL) was injected at a rate of 0.1 mL / h using a syringe pump. After the injection, the reaction was continued for 9 hours. The mixture was naturally cooled, centrifuged, and washed to obtain PtCo@PtIr octahedral core-shell nanoparticles. The shell metal precursors included potassium hexachloroplatinate (IV) and potassium hexachloroiridate (III). Potassium hexachloroplatinate (IV) was 1 mg, and potassium hexachloroiridate (III) was 3.5 mg. They were dissolved in 1.5 mL of deionized water for injection. The PtCo@PtIr octahedral core-shell nanoparticles were placed in a vacuum drying oven and stored at room temperature.

[0079] Example 5

[0080] like Figure 1 As shown, a method for preparing PtCo@PtIr octahedral core-shell nanoparticles comprises the following steps:

[0081] (1) Weigh 15 mg of platinum acetylacetonate, 15 mg of cobalt acetylacetonate, and 115 mg of tungsten hexacarbonyl into a flask, then add 4 mL of oleylamine and 10 mL of benzyl alcohol to the flask to obtain solution A;

[0082] (2) heating solution A to 60°C and maintaining it for 30 minutes, then rapidly heating it to 200°C and maintaining it for 40 minutes to obtain solution B;

[0083] (3) Solution B was centrifuged to obtain an intermediate product, which was washed with ethanol and acetone and then dispersed in 8 mL of n-hexane to obtain solution C;

[0084] (4) 30 mg of carbon black, 20 mL of n-hexane, and solution C were mixed by ultrasonication, centrifuged, and then dried in a vacuum drying oven to obtain PtCo alloy nanoparticles;

[0085] (5) annealing the PtCo alloy nanoparticles at 600°C for 4 hours in a tube furnace filled with 96% argon and 4% hydrogen, and then naturally cooling to room temperature to obtain PtCo intermetallic compound nanoparticles;

[0086] (6) 10 mg of PtCo intermetallic compound nanoparticles and 30 mg of citric acid were dispersed in 5 mL of deionized water. 1.5 mL of the shell metal precursor (3 mg / mL) was injected at a rate of 0.1 mL / h using a syringe pump. After the injection, the reaction was continued for 9 hours. The mixture was naturally cooled, centrifuged, and washed to obtain PtCo@PtIr octahedral core-shell nanoparticles. The shell metal precursors included sodium hexachloroplatinate (IV) and sodium hexachloroiridate (III). Sodium hexachloroplatinate (IV) was 1 mg, and sodium hexachloroiridate (III) was 3.5 mg. They were dissolved in 1.5 mL of deionized water for injection. The PtCo@PtIr octahedral core-shell nanoparticles were placed in a vacuum drying oven and stored at room temperature.

[0087] 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, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Application of PtCo@PtIr octahedral core-shell nanoparticles as bifunctional electrocatalysts for ORR and OER, characterized by: The PtCo@PtIr octahedral core-shell nanoparticles have PtCo intermetallic compound nanoparticles as the core and bimetallic PtIr as the shell.

2. The use according to claim 1, characterized in that: The size of PtCo@PtIr octahedral core-shell nanoparticles is 8-10 nm.

3. The use according to claim 1 or 2, characterized in that: The thickness of the PtIr shell is 2 to 4 atomic layers.

4. The use according to claim 1, characterized in that The PtCo@PtIr octahedral core-shell nanoparticles are prepared by epitaxially growing a PtIr shell layer on PtCo intermetallic compound nanoparticles.

5. The use according to claim 4, characterized in that The preparation method of the PtCo@PtIr octahedral core-shell nanoparticles comprises the following steps: (1) dispersing a metal precursor, a capping agent, and a reducing agent I in a solvent I to obtain a solution A, wherein the metal precursor includes a platinum source and a cobalt source; (2) Solution A was heated under argon and then naturally cooled to room temperature to obtain solution B; (3) Centrifuging solution B to obtain an intermediate product, washing the intermediate product, and dispersing it in n-hexane to obtain solution C; (4) The carbon black, n-hexane and solution C were mixed and ultrasonicated, and then centrifuged, washed and dried under vacuum to obtain PtCo alloy nanoparticles; (5) annealing the PtCo alloy nanoparticles and naturally cooling them to room temperature to obtain PtCo intermetallic compound nanoparticles; (6) PtCo intermetallic compound nanoparticles and reducing agent II are dispersed in solvent II, and then the shell metal precursor is slowly added. After centrifugation and washing, the mixture is dried in a vacuum environment to obtain PtCo@PtIr octahedral core-shell nanoparticles. The shell metal precursor includes a platinum source and an iridium source.

6. The use according to claim 5, characterized in that In step (1), the metal precursor includes platinum acetylacetonate and cobalt acetylacetonate, the capping agent is tungsten hexacarbonyl, the reducing agent I is oleylamine, and the solvent I is benzyl alcohol; the amount of platinum acetylacetonate is 10-20 mg, the amount of cobalt acetylacetonate is 10-20 mg, the amount of the capping agent is 75-150 mg, the amount of the reducing agent I is 3-6 mL, and the volume of the solvent I is 7-14 mL.

7. The use according to claim 5 or 6, characterized in that In step (6), the reducing agent II is citric acid, the solvent II is deionized water, the shell metal precursor includes a platinum source and an iridium source, the platinum source is sodium hexachloroplatinate (IV) or potassium hexachloroplatinate (IV), and the iridium source is sodium hexachloroiridate (III) or potassium hexachloroiridate (III); the amount of PtCo intermetallic compound nanoparticles is 10-20 mg, the amount of reducing agent II is 30-60 mg, the amount of solvent II is 5-10 mL, the amount of platinum source is 1-3.5 mg, and the amount of iridium source is 1-3.5 mg. The platinum source and iridium source are dissolved in deionized water and then injected at an injection rate of 0.1 mL / h.

8. The use according to claim 5, characterized in that In step (2), the heating reaction temperature is 60-200° C., and the reaction time is 40-120 minutes. In step (3), the specific method for washing the intermediate product is: ultrasonically dispersing the intermediate product in ethanol and acetone, and then centrifugally precipitating, and repeating 1-2 times.

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