Preparation method and application of a supported coralline dendrite alloy catalyst

Abstract

The present invention relates to the field of alloy catalysts, and discloses a preparation method and application of a supported coralline alloy catalyst. The method comprises the following steps: S1, adding platinum acetylacetonate to a mixed solution of iron acetylacetonate and manganese acetylacetonate in oleylamine, adding a reducing agent borane tert-butylamine complex for reflux reaction, cooling and washing the product, ultrasonically treating it under ethanol and n-hexane, centrifuging and washing it, and ultrasonicating it together with a n-hexane dispersion of carbon black, and magnetically stirring it to prepare a coralline PtFeMn alloy supported on carbon black; S2, adding the obtained carbon black dispersion of the coralline PtFeMn alloy to an ethanol solution for ultrasonic cleaning, vacuum drying the product obtained by centrifugation, and preparing a supported catalyst of a specific structure under different annealing conditions under a hydrogen-argon mixed protective gas. The present invention prepares a coralline platinum-iron-manganese nanoalloy catalyst with uniform dispersion and consistent morphology by a one-pot synthesis method, and the obtained catalyst exhibits good oxygen reduction activity in an acidic environment.

Description

Technical Field

[0001] The present invention relates to the field of PtFeMn coralline dendrite nano alloys, and in particular to a preparation method and application of a supported coralline dendrite alloy catalyst. Background Art

[0002] Hydrogen fuel cells can use hydrogen as fuel to convert it into high-energy-density electricity, but there are still many problems in its practical application, such as the slow kinetic rate of the oxygen reduction reaction (ORR) at the cathode. Therefore, there is an urgent need to develop low-cost, high-energy conversion efficiency, and long-life catalyst materials.

[0003] Currently, the existing commercial proton exchange membrane fuel cell cathode oxygen reduction electrocatalyst is mainly platinum-carbon (Pt / C) catalyst, which mainly uses the precious metal Pt. It is expensive and its activity and long-term stability still need to be further improved. By introducing a third metal, the morphology and size of the alloy can also be regulated. Compared with regular polyhedral alloy nanoparticles, coral-like nanostructures sometimes have unique advantages in electrocatalysis. Due to the presence of special branched branches, grain boundaries and atomic steps, they often have abundant active centers and high activity per unit mass. Designing platinum-based multi-metal nanocrystals with coral-like morphology as electrocatalysts is expected to reduce the amount of precious metals while further solving problems such as low specific activity and poor stability. Summary of the Invention

[0004] In order to address the deficiencies mentioned in the above-mentioned background technology, the purpose of the present invention is to provide a preparation method and application of a supported coralline dendrite alloy catalyst. Under the combined action of multi-element interactions and crystal surface defects, the Pt-based nanocrystals have a special highly active surface and interface structure, and maintain a small size and a stable special morphology. The alloy catalyst exhibits excellent oxygen reduction activity in an acidic environment.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] The present invention provides a method for preparing a supported coralline dendrite alloy catalyst, comprising the following steps:

[0007] S1. Add platinum acetylacetonate to a mixed solution of iron acetylacetonate and manganese acetylacetonate in oleylamine, add a reducing agent, borane tert-butylamine complex, and stir the mixture in a circulating reflux heating environment under argon protection for a period of time. The product is naturally cooled to room temperature. The washed colloid is ultrasonically treated in ethanol and n-hexane, and centrifuged and washed until the solution is free of surfactant. The product obtained by centrifugation is ultrasonically treated with a n-hexane dispersion of carbon black, and magnetically stirred for 4-8 hours to obtain PtFeMn coralline dendrite nanocrystals supported on carbon black;

[0008] S2. The obtained carbon black dispersion of PtFeMn coral dendrite nanocrystals is added to an ethanol solution for ultrasonic cleaning, the product obtained by centrifugation is vacuum dried, and high-temperature annealing is performed under a hydrogen-argon mixed protective gas to obtain a supported coral dendrite alloy catalyst.

[0009] Preferably, in step S1, the molar ratio of platinum acetylacetonate to iron acetylacetonate and manganese acetylacetonate is 2:1:1, and the molar ratio of the reducing agent borane tert-butylamine complex to platinum acetylacetonate is 1:1.

[0010] Preferably, in step S1, the dispersion of the precursor and the reducing agent is circulated and refluxed and heated under argon protection, with a heating temperature of 300° C., a heating rate of 5° C. / min, and an oil bath time of 2 h.

[0011] Preferably, the product obtained by centrifugation in step S1 and the n-hexane dispersion of carbon black are ultrasonically treated for 30 minutes, and then magnetically stirred for 24 hours.

[0012] Preferably, in step S1, the loading amount of PtFeMn coralline dendrite nanocrystals on carbon black is 20 wt %, and the carbon black is carbon powder XC-72.

[0013] Preferably, in step S4, the volume ratio of hydrogen to argon in the mixed protective gas is 1:19, and the high temperature annealing is performed by heating the temperature to 400° C. at a heating rate of 5° C. / min and then keeping the temperature for 4 hours.

[0014] The invention discloses an application of a supported coralline dendrite alloy catalyst in an acidic oxygen reduction reaction. The supported coralline dendrite alloy catalyst is prepared according to the above method. The PtFeMn coralline dendrite nanocrystals have high acidic oxygen reduction reaction activity.

[0015] Beneficial effects of the present invention:

[0016] The present invention provides a method for preparing a supported coralline-dendritic alloy catalyst with high ORR activity. The coralline-dendritic PtFeMn nanocrystal catalyst prepared by the one-pot reduction method of the present invention exhibits high acidic oxygen reduction reaction activity. The size effect significantly enhances the catalyst activity. The coralline-dendritic PtFeMn nanocrystals not only improve the utilization rate of platinum atoms but also reduce the cost of the catalyst. Furthermore, the nanocatalyst with a multi-component special morphology exhibits even higher activity, making it a promising alternative to electrocatalytic oxygen reduction catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below with reference to the accompanying drawings.

[0018] Figure 1 is a comparison of the X-ray diffraction patterns of Examples 1, 2, and 3;

[0019] Figure 2The morphology and crystal structure of Examples 1, 2, and 3 are shown under low-magnification electron microscopy (ac) and high-resolution electron microscopy (df);

[0020] Figure 3 This is the EDS-Mapping spectrum comparison of Example 3;

[0021] Figure 4 is a comparison of EXAFS spectra of Examples 1, 2, and 3;

[0022] Figure 5 (a) is the LSV curve of acidic oxygen reduction of Example 3 at different rotation speeds; (b) is the comparison of the LSV curves of acidic oxygen reduction of Examples 1, 2, and 3 at a rotation speed of 1600 rpm; (c) is the mass activity and half-wave potential of Example 3 and PtC, and (d) is the performance comparison of the PtFeMn alloy catalyst in Example 3 and the commercial PtC catalyst under acidic conditions. DETAILED DESCRIPTION

[0023] 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. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] Example 1

[0025] 1 mmol of iron acetylacetonate, 0.5 mmol of manganese acetylacetonate, and 1 mmol of platinum acetylacetonate were dispersed in 30 ml of oleylamine. The precursors were then mixed and ultrasonicated for 20 minutes. 1 mmol of tert-butyl amine borane (TBAB) was added to dissolve and disperse the precursors. Next, the precursor solution was poured into a round flask, stirred vigorously, and evacuated. The solution was heated to 120°C in reflux condensing mode for 30 minutes. Argon was then introduced, and the temperature was increased to 300°C at a rate of 5°C / min under a protective atmosphere and maintained for 1 hour.

[0026] After the brown colloidal solution cools to room temperature, it is centrifuged and washed. First, 30 ml of n-hexane is added to disperse the product, followed by 60 ml of ethanol to precipitate the product. The solution is shaken and sonicated for 5 minutes to better separate the product from the oleylamine. The solution is then centrifuged and washed for 10 minutes at 8000 rpm. The product is washed three times using the above method, and the supernatant is removed to obtain the product precipitate.

[0027] The cleaned product was loaded onto a carbon powder XC-72 support at a 20 wt% ratio. The product and a predetermined amount of carbon powder XC-72 were co-dispersed in n-butylamine and ultrasonically treated for 30 minutes. The loading was then magnetically stirred for 24 hours to allow for ligand exchange and nanoparticle deposition on the support. Finally, the carbon black-loaded sample was centrifuged and cleaned three times with ethanol at 6000 rpm and vacuum-dried overnight. The dried sample was heated to 400°C at a rate of 5°C / min in a 5% H2 / 95% Ar atmosphere, held for 4 hours, and then cooled in the furnace.

[0028] Example 2

[0029] 0.5 mmol of iron acetylacetonate, 1 mmol of manganese acetylacetonate, and 1 mmol of platinum acetylacetonate were dispersed in 30 ml of oleylamine. The precursors were then mixed and ultrasonicated for 20 minutes. 1 mmol of tert-butyl amine borane (TBAB) was added to dissolve and disperse the precursors. Next, the precursor solution was poured into a round flask, stirred vigorously, and evacuated. The solution was heated to 120°C in reflux condensing mode for 30 minutes. Argon was then introduced and the temperature was increased to 300°C at a rate of 5°C / min under a protective atmosphere, where it was held for 1 hour.

[0030] After the brown colloidal solution cools to room temperature, it is centrifuged and washed. First, 30 ml of n-hexane is added to disperse the product, followed by 60 ml of ethanol to precipitate the product. The solution is shaken and sonicated for 5 minutes to better separate the product from the oleylamine. The solution is then centrifuged and washed for 10 minutes at 8000 rpm. The product is washed three times using the above method, and the supernatant is removed to obtain the product precipitate.

[0031] The cleaned product was loaded onto a carbon powder XC-72 support at a 20 wt% ratio. The product and a predetermined amount of carbon powder XC-72 were co-dispersed in n-butylamine and ultrasonically treated for 30 minutes. The loading was then magnetically stirred for 24 hours to allow for ligand exchange and nanoparticle deposition on the support. Finally, the carbon black-loaded sample was centrifuged and cleaned three times with ethanol at 6000 rpm and vacuum-dried overnight. The dried sample was heated to 400°C at a rate of 5°C / min in a 5% H2 / 95% Ar atmosphere, held for 4 hours, and then cooled in the furnace.

[0032] Example 3

[0033] 0.5 mmol of iron acetylacetonate, 0.5 mmol of manganese acetylacetonate, and 1 mmol of platinum acetylacetonate were dispersed in 30 ml of oleylamine. The precursor and oleylamine were then mixed and ultrasonicated for 20 minutes. 1 mmol of tert-butyl amine borane (TBAB) was added to dissolve and disperse the precursor. Next, the precursor solution was poured into a round flask, stirred vigorously, and evacuated. The solution was heated to 120°C in reflux condensing mode for 30 minutes. Argon was then introduced and the temperature was increased to 300°C at a rate of 5°C / min under a protective atmosphere and maintained for 1 hour.

[0034] After the brown colloidal solution cools to room temperature, it is centrifuged and washed. First, 30 ml of n-hexane is added to disperse the product, followed by 60 ml of ethanol to precipitate the product. The solution is shaken and sonicated for 5 minutes to better separate the product from the oleylamine. The solution is then centrifuged and washed for 10 minutes at 8000 rpm. The product is washed three times using the above method, and the supernatant is removed to obtain the product precipitate.

[0035] The cleaned product was loaded onto a carbon powder XC-72 support at a 20 wt% ratio. The product and a predetermined amount of carbon powder XC-72 were co-dispersed in n-butylamine and ultrasonically treated for 30 minutes. The loading was then magnetically stirred for 24 hours to allow for ligand exchange and nanoparticle deposition on the support. Finally, the carbon black-loaded sample was centrifuged and cleaned three times with ethanol at 6000 rpm and vacuum-dried overnight. The dried sample was heated to 400°C at a rate of 5°C / min in a 5% H2 / 95% Ar atmosphere, held for 4 hours, and then cooled in the furnace.

[0036] Comparative Example 1

[0037] 1 mmol of platinum acetylacetonate was dispersed in 30 ml of oleylamine. The precursor and oleylamine were then mixed and ultrasonicated for 20 minutes. 1 mmol of tert-butyl borane (TBAB) was then added to dissolve and disperse the precursor. Next, the precursor solution was poured into a round flask, stirred vigorously, and evacuated. The solution was heated to 120°C in reflux condensing mode for 30 minutes. Argon was then introduced, and the temperature was increased to 280°C at a rate of 5°C / min under a protective atmosphere and held for 1 hour.

[0038] After the purple-red colloidal solution cools to room temperature, it undergoes a centrifugal washing step. First, 30 ml of n-hexane is added to disperse the product, followed by 60 ml of ethanol to precipitate the product. The solution is shaken and sonicated for 5 minutes to better separate the product from the oleylamine. The solution is then centrifuged at 8,000 rpm for 10 minutes. The product is washed three times using the above method, and the supernatant is discarded to obtain the product precipitate.

[0039] The cleaned product was loaded onto a carbon powder XC-72 support at a 20 wt% ratio. The product and a predetermined amount of carbon powder XC-72 were co-dispersed in n-butylamine and ultrasonically treated for 30 minutes. The loading was then magnetically stirred for 24 hours to allow for ligand exchange and nanoparticle deposition on the support. Finally, the carbon black-loaded sample was centrifuged and cleaned three times with ethanol at 6000 rpm and vacuum-dried overnight. The dried sample was heated to 400°C at a rate of 5°C / min in a 5% H2 / 95% Ar atmosphere, held for 4 hours, and then cooled in the furnace.

[0040] Comparative Example 2

[0041] 0.5 mmol of iron acetylacetonate and 1 mmol of platinum acetylacetonate were dispersed in 30 ml of oleylamine. The precursor and oleylamine were then mixed and ultrasonicated for 20 minutes. 1 mmol of tert-butyl borane (TBAB) was added to dissolve and disperse the precursor. Next, the precursor solution was poured into a round flask, stirred vigorously, and evacuated. The solution was heated to 120°C in reflux condensing mode for 30 minutes. Argon was then introduced and the temperature was increased to 300°C at a rate of 5°C / min under a protective atmosphere and maintained for 1 hour.

[0042] After the brown colloidal solution cools to room temperature, it is centrifuged and washed. First, 30 ml of n-hexane is added to disperse the product, followed by 60 ml of ethanol to precipitate the product. The solution is shaken and sonicated for 5 minutes to better separate the product from the oleylamine. The solution is then centrifuged and washed for 10 minutes at 8000 rpm. The product is washed three times using the above method, and the supernatant is removed to obtain the product precipitate.

[0043] The cleaned product was loaded onto a carbon powder XC-72 support at a 20 wt% ratio. The product and a predetermined amount of carbon powder XC-72 were co-dispersed in n-butylamine and ultrasonically treated for 30 minutes. The loading was then magnetically stirred for 24 hours to allow for ligand exchange and nanoparticle deposition on the support. Finally, the carbon black-loaded sample was centrifuged and cleaned three times with ethanol at 6000 rpm and vacuum-dried overnight. The dried sample was heated to 400°C at a rate of 5°C / min in a 5% H2 / 95% Ar atmosphere, held for 4 hours, and then cooled in the furnace.

[0044] Structural inspection

[0045] Depend on Figure 1The XRD results show that the annealed PtFeMn alloy catalyst supported on the carbon black substrate still maintains the Pt fcc structure. The broadening of the diffraction peak indicates that the coral branch structure has a smaller nanocrystal size. In the sample of Example 3, no diffraction peaks of any single oxide species appear, indicating that the transition metal atoms are incorporated into the Pt lattice and do not form separate elements or oxides. Figure 2 TEM( Figure 2 ) Figure 3 shows that with the addition of transition metal elements, the morphology difference between the comparative example PtNP, PtFe and the example PtFMn nanocrystals gradually becomes larger, evolving from nanoparticles with larger diameters to small-sized coral-like nanocrystals. TEM image of the sample in Example 3 ( Figure 2 (f)) shows that the sample surface has abundant crystal plane defects and has many step-like surface structural features, which indicates that the sample has a special multi-oriented coral-like morphology and a special crystal plane structure. Figure 3 ) analysis showed that the elements in the sample were distributed evenly, without element segregation or the formation of core-shell structure.

[0046] In order to further confirm that PtFeMn in Example 3 exists in the form of an alloy, we used Fourier transform X-ray fine structure absorption spectroscopy (FT-EXAFS, Figure 3 ) characterized the material. Example 2 shows a primary peak, MO, representing a non-metallic coordination peak, and secondary peaks, M1-M2, representing metal coordination peaks (M = Pt\Fe\Mn). This indicates that M forms a bond with O on the alloy surface and has a specific oxidation state, confirming the formation of PtFe and PtFeMn alloys. The results of Example 3, on the other hand, show an increase in the height of the PtFeMn metal coordination peak, indicating a higher degree of alloying. Finally, these analytical results correspond to those from electron microscopy and XRD, demonstrating the successful synthesis of a coral-like PtFeMn alloy catalyst supported on a carbon black substrate in Example 3.

[0047] Performance testing

[0048] In order to evaluate the ORR activity of the PtNP catalyst in Comparative Example 1, the PtFe catalyst in Comparative Example 2, and the PtFeMn alloy catalyst in Example 3 under acidic conditions, we used a commercial PtC (20%) catalyst as a reference for the performance of the PtFeMn alloy. The specific test steps and results are as follows:

[0049] (1) 2 mg of PtNP from Comparative Example 1, PtFe from Comparative Example 2, PtFeMn alloy catalyst from Example 3, and commercial PtC catalyst were selected, 700 μL of isopropanol, 180 μL of ultrapure water, and 20 μL of perfluorosulfonic acid (5 wt%) as a binder were added, and the mixture was uniformly mixed and ultrasonicated for 1 h to obtain a uniformly mixed catalyst ink. 20 ml of the catalyst ink was accurately pipetted with a pipette and evenly dropped onto a 5 mm diameter, 0.196 cm area. 2 Place the sample on a rotating disk electrode and allow it to dry naturally before testing.

[0050] (2) In 0.1M HClO4 solution, Ag / AgCl was used as the reference electrode and a platinum wire electrode was used as the counter electrode. The three-electrode mode was used for measurement and all potentials were converted to reversible hydrogen electrode potentials (RHE). The scan rate was 10mV / s and ORR polarization curves were collected at different rotation speeds. The test results of Comparative Examples 1 and 2 were compared with those of Example 3 at a rotation speed of 1600rpm. Figure 5 As shown in (a), it can be clearly seen that the PtFeMn catalyst of Example 3 has the best ORR activity, with a half-wave potential of 0.89mV, which is much higher than the 0.84mV of the PtFe catalyst and the 0.81mV of the commercial PtC catalyst. Figure 5 As shown in (b), the PtFeMn sample in Example 3 has the best performance. ORR tests were performed on it at different scan rates, and it was found that it has a higher half-wave current and a larger current density. Figure 5 (d) shows the performance comparison of the PtFeMn alloy catalyst in Example 3 and the commercial PtC catalyst under acidic conditions. The mass activities at 0.9 V are 0.92 A / mg and 0.73 A / mg, respectively. The coralline PtFeMn alloy catalyst has a better mass activity than the commercial PtC.

[0051] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0052] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A method for preparing a supported coralline dendrite alloy catalyst, characterized in that: The following steps are involved: S1. Add platinum acetylacetonate to a mixed solution of iron acetylacetonate and manganese acetylacetonate in oleylamine, add a reducing agent, borane tert-butylamine complex, place the mixture in a circulating reflux heating environment under argon protection, and stir the reaction for a period of time. The product is naturally cooled to room temperature. The washed colloid is ultrasonically treated in ethanol and n-hexane, and centrifuged and washed until the solution is free of surfactant. The product obtained by centrifugation is ultrasonically treated with a n-hexane dispersion of carbon black, and the mixture is loaded by magnetic stirring to obtain PtFeMn coralline dendrite nanocrystals loaded on carbon black; S2, adding the obtained carbon black dispersion of PtFeMn coral dendrite nanocrystals to an ethanol solution for ultrasonic cleaning, vacuum drying the obtained product by centrifugation, and annealing at a high temperature under a hydrogen-argon mixed protective gas to obtain a supported coral dendrite alloy catalyst; In step S1, the molar ratio of platinum acetylacetonate to iron acetylacetonate and manganese acetylacetonate is 2:1:1, and the molar ratio of the reducing agent borane tert-butylamine complex to platinum acetylacetonate is 1:1; Step S1: The dispersion of the precursor and the reducing agent is refluxed and heated under argon protection at a temperature of 300°C, a heating rate of 5°C / min, and an oil bath time of 2 hours; In step S2, the volume ratio of hydrogen to argon in the mixed protective gas is 1:19, and the high temperature annealing is performed by heating the temperature to 400° C. at a heating rate of 5° C. / min and then keeping the temperature for 4 hours.

2. The method for preparing the supported coralline dendrite alloy catalyst according to claim 1, wherein: The product obtained by centrifugation in step S1 and the n-hexane dispersion of carbon black were ultrasonically treated for 30 minutes, and then magnetically stirred for 24 hours.

3. The method for preparing the supported coralline dendrite alloy catalyst according to claim 1, wherein: In step S1, the loading amount of PtFeMn coralline dendrite nanocrystals on carbon black is 20 wt %, and the carbon black is carbon powder XC-72.

4. Application of a supported coralline dendrite alloy catalyst in an acidic oxygen reduction reaction, characterized in that: The supported coralline dendrite alloy catalyst is prepared according to the method according to any one of claims 1-3.

Images