Preparation and application of high-loading Pt-based intermetallic compound catalyst

Abstract

The invention discloses preparation and application of a high-loading-capacity Pt-based intermetallic compound catalyst, non-noble metal M is introduced as a precursor Pt / C-M disordered alloy on the basis of an existing Pt / C catalyst through low-temperature reduction, the Pt / C-M disordered alloy can still keep small size when the total metal content is 40-70%, metal M atoms can be effectively anchored on Pt particles, and the Pt / C-M disordered alloy can be used for preparing a high-loading-capacity Pt-based intermetallic compound catalyst. And a stoichiometric ratio beneficial to alloying of Pt and metal M atoms is locally formed. The non-noble metal is added on the basis of the Pt / C catalyst, the Pt / C-M disordered alloy is firstly formed at a low temperature, high-temperature heat treatment is performed after SiO2 coating, conversion from the Pt / C-M disordered alloy to the PtM ordered alloy is achieved, atom migration can be kept while overgrowth of particles can be further controlled, ordering is achieved, the prepared catalyst PtM alloy particles are small in particle size, the particle size is small, and the particle size is uniform. The catalyst prepared by the method has the advantages of simple preparation process, narrow particle size distribution and high order degree, so that good activity and stability are obtained, and the catalyst prepared by the method has a wide application prospect in cathode reaction of fuel cells.

Description

Technical Field

[0001] The present invention relates to the technical field of fuel cell catalysts, and in particular to the preparation and application of a high-loaded Pt-based intermetallic compound catalyst. Background Art

[0002] Proton exchange membrane fuel cells have broad application prospects, among which catalysts are crucial as key components. Existing platinum-carbon catalysts have disadvantages such as low activity, short life and high catalyst cost. Therefore, introducing a second metal M to form an alloy with the precious metal Pt to reduce the cost of the catalyst has gradually become the current trend. The disordered-ordered phase transition of alloy catalysts can bring higher activity, but the problem of catalyst particle sintering caused by high-temperature heat treatment during the preparation process is very prominent. In addition, most researchers focus on the preparation of low-load Pt-based catalysts, ignoring the mass transfer problem caused by the thickness of the catalyst layer when preparing membrane electrodes. Summary of the invention

[0003] In view of the deficiencies of the prior art, the present invention aims to provide a preparation method and application of a high-loaded Pt-based intermetallic compound catalyst.

[0004] In order to achieve the above object, the present invention adopts the following technical solution:

[0005] A method for preparing a high-loaded Pt-based intermetallic compound catalyst comprises the following steps:

[0006] S1, mixing the Pt / C catalyst, deionized water and the precursor solution containing metal M by ultrasonication, freezing them into a solid in liquid nitrogen, and drying them in a vacuum freeze dryer, and then performing a low-temperature heat treatment at 300-400° C. in a reducing atmosphere to obtain powder A, which is a Pt / CM alloy;

[0007] S2, after moistening the powder A obtained in step S1 with deionized water, adding an alkaline solution and a silicon source to the powder A for reaction, filtering to obtain a solid reaction product, washing and drying to obtain a powder B;

[0008] S3, subjecting the powder B obtained in step S2 to a high temperature heat treatment at 600-800° C. in a non-oxidizing atmosphere to achieve a transformation of the Pt / CM disordered alloy into an ordered alloy, thereby obtaining powder C;

[0009] S4, adding the powder C obtained in step S3 into a sodium hydroxide solution for reaction, filtering to obtain a solid reactant, washing and drying the solid reactant to obtain a powder D;

[0010] S5. The powder D obtained in step S4 is sequentially pickled, washed with water and dried to finally obtain an O-PtM / C ordered alloy catalyst, that is, a high-loaded Pt-based intermetallic compound catalyst.

[0011] Furthermore, in step S1, the metal M is one or more of Co, Cu, Ni and Fe.

[0012] Furthermore, in step S1, the precursor solution containing the metal M is one or more of a cobalt nitrate hexahydrate solution, a copper nitrate solution, a nickel nitrate solution, and a ferric nitrate solution.

[0013] Furthermore, in step S1, the reducing atmosphere is 5-10 vol% H2 / Ar gas, and the low temperature heat treatment time is 2-6 h.

[0014] Furthermore, in step S2, the alkaline solution is one of ammonia water, sodium hydroxide solution, and sodium carbonate solution, the silicon source is one of tetraethyl orthosilicate, tetraethoxysilane, and tetramethoxysilane, and the reaction time is 4-10 hours.

[0015] Furthermore, in step S3, the high temperature heat treatment time is 2-8 hours.

[0016] Furthermore, in step S4, the temperature of the reaction between powder C and sodium hydroxide solution is 60-100° C., and the reaction time is 4-12 h.

[0017] Furthermore, in step S5, the powder D is pickled with one of 0.5-2 mol / L sulfuric acid solution, perchloric acid solution or nitric acid solution, the pickling temperature is 60-120° C., and the pickling time is 2-8 h.

[0018] The present invention also provides a high-load Pt-based intermetallic compound catalyst prepared by the preparation method.

[0019] The present invention also provides an application of a high-load Pt-based intermetallic compound catalyst prepared by the above preparation method in a cathode oxygen reduction reaction in a fuel cell.

[0020] The beneficial effects of the present invention are:

[0021] 1. The present invention introduces non-precious metal M as a precursor Pt / CM disordered alloy by low-temperature reduction on the basis of the existing Pt / C catalyst. The Pt / CM disordered alloy can not only maintain a small size at a total metal content of 40-70%, but also effectively anchor the metal M atoms on the Pt particles, forming a stoichiometric ratio that is conducive to the alloying of Pt and metal M atoms locally;

[0022] 2. The method of the present invention adds non-precious metals to the Pt / C catalyst, first forms a Pt / CM disordered alloy at low temperature, and then performs high-temperature heat treatment after SiO2 coating to achieve the transformation of the Pt / CM disordered alloy to the PtM ordered alloy, which can further control the excessive growth of particles while maintaining atomic migration to achieve ordering. The obtained catalyst PtM alloy particles have small particle size, narrow particle size distribution, and high order, thereby obtaining good activity and stability. Therefore, the catalyst prepared by the present invention has broad application prospects in the cathode reaction of fuel cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 TEM image of the catalyst O-PtCo / C prepared in Example 1 of the present invention;

[0024] Figure 2 The XRD pattern of the catalyst O-PtCo / C prepared in Example 1 of the present invention;

[0025] Figure 3 TEM image of the catalyst O-PtCo / Ca prepared in Comparative Example 1;

[0026] Figure 4 The XRD pattern of the catalyst O-PtCo / Ca prepared in Comparative Example 1;

[0027] Figure 5 CV graphs of the catalyst O-PtCo / C prepared in Example 1 and the catalyst O-PtCo / Ca prepared in Comparative Example 1;

[0028] Figure 6 LSV diagrams of the catalyst O-PtCo / C prepared in Example 1 and the catalyst O-PtCo / Ca prepared in Comparative Example 1;

[0029] Figure 7 This is a graph showing the actual application performance data of the catalyst prepared in Example 1 in a fuel cell. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0031] Example 1

[0032] This embodiment provides a method for preparing a high-loaded Pt-based intermetallic compound catalyst, comprising the following steps:

[0033] (1) Accurately weigh 300 mg of Pt / C catalyst (platinum-carbon catalyst), add 56 mL of deionized water and 4 mL of 0.18 mol / L cobalt nitrate hexahydrate solution in sequence, stir for 10 min, and then ultrasonically disperse for 30 min. After the ultrasonic dispersion is completed, the obtained mixture is immediately placed in liquid nitrogen to freeze into a solid, and then the frozen solid is placed in a vacuum freeze dryer for freeze drying for 72 h. Thereafter, the dried solid is placed in a tube furnace, 5 vol% H2 / Ar gas is introduced, the temperature is raised to 400°C, and low-temperature heat treatment is performed for 2 h to obtain powder A;

[0034] (2) 100 mg of powder A was first moistened with 1 mL of deionized water, and then 100 mL of ethanol was added and ultrasonically mixed for 10 min. Then, 4.5 mL of ammonia water and 0.9 mL of tetraethyl orthosilicate were added in sequence and stirred at room temperature for 6 h. After the reaction was completed, the obtained mixture was filtered, washed, vacuum dried at 60°C, and ground to obtain powder B.

[0035] (3) Powder B was placed in a tube furnace and introduced with 5 vol% H2 / Ar. The temperature was raised to 700°C and heat treated for 2 h to obtain powder C.

[0036] (4) Powder C was dispersed in a 2 mol / L NaOH solution, stirred in a 60°C water bath for 6 h, and filtered, washed, dried and ground to obtain powder D.

[0037] (5) The obtained powder D was ultrasonically dispersed in a 0.5 mol / L H2SO4 solution, acid-washed at 80°C for 2 h, filtered, washed, dried and then ground to prepare a high-loading Pt-based intermetallic compound catalyst O-PtCo / C.

[0038] Example 2

[0039] The method of this embodiment is basically the same as that of embodiment 1, except that the temperature in step (1) is changed to 300°C.

[0040] Example 3

[0041] The method of this embodiment is basically the same as that of embodiment 1, except that the temperature in step (3) is changed to 600°C.

[0042] Example 4

[0043] The method of this embodiment is basically the same as that of embodiment 1, except that the temperature in step (3) is changed to 800°C.

[0044] Example 5

[0045] The method of this embodiment is basically the same as that of embodiment 1, except that the temperature in step (4) is changed to 100°C.

[0046] Example 6

[0047] The method of this embodiment is basically the same as that of embodiment 1, except that the pickling temperature in step (5) is changed to 60°C.

[0048] Example 7

[0049] The method of this embodiment is basically the same as that of embodiment 1, except that the pickling temperature in step (5) is changed to 120°C.

[0050] Example 8

[0051] The method of this embodiment is basically the same as that of Example 1, except that the cobalt nitrate hexahydrate solution in step (1) is replaced with copper nitrate trihydrate solution, and the catalyst finally obtained is denoted as O-PtCu / C.

[0052] Example 9

[0053] The method of this embodiment is basically the same as that of Example 1, except that the cobalt nitrate hexahydrate solution in step (1) is replaced with a nickel nitrate hexahydrate solution, and the catalyst finally obtained is denoted as O-PtNi / C.

[0054] Example 10

[0055] The method of this embodiment is basically the same as that of embodiment 1, except that the cobalt nitrate hexahydrate solution in step (1) is replaced with ferric nitrate nonahydrate solution, and the catalyst finally obtained is denoted as O-PtFe / C.

[0056] Comparative Example 1

[0057] Compared with the method of Example 1, the step (3) is omitted in Comparative Example 1, and the catalyst finally obtained is recorded as O-PtCo / Ca.

[0058] Figure 1 TEM image of the catalyst O-PtCo / C prepared in Example 1, Figure 2 is the XRD pattern of the catalyst O-PtCo / C prepared in Example 1, Figure 3 TEM image of the catalyst O-PtCo / Ca prepared in Comparative Example 1, Figure 4 is the XRD pattern of the catalyst O-PtCo / Ca prepared in Comparative Example 1, Figure 5 CV graphs of the catalyst O-PtCo / C prepared in Example 1 and the catalyst O-PtCo / Ca prepared in Comparative Example 1, Figure 6 : are LSV diagrams of the catalyst O-PtCo / C prepared in Example 1 and the catalyst O-PtCo / Ca prepared in Comparative Example 1, Figure 7The actual application performance data of the catalyst of Example 1 in a fuel cell, Table 1 is a comparison of the element contents of Example 1 and Comparative Example 1, and Table 2 is a comparison of the experimental parameters and performances of Examples 1-7.

[0059] Table 1 Comparison of element contents between Example 1 and Comparative Example 1

[0060] sample Pt wt.% Co wt.% Pt / Co molar ratio Total metal loading% Comparative Example 1 55.23 9.82 1.7 65.05 Example 1 58.78 9.55 1.86 68.33

[0061] Table 2 Experimental parameters and performance comparison of Examples 1-7

[0062]

[0063]

[0064] Comparison of TEM images of Example 1 and Comparative Example 1 ( Figure 1 and Figure 3 ), the results show that the method of Example 1 is effective for preparing catalyst particles with smaller particle size and narrower distribution; Figure 2 The XRD pattern of shows that it matches the ordered alloy corresponding to the standard PDF card, and the element contents in Table 1 prove that the catalyst in Example 1 has a reasonable atomic stoichiometric ratio. Figure 7 The performance data in Table 2 indicate that the methods of Examples 1-7 prepare a Pt-based intermetallic compound catalyst with high loading, small particle size, narrow distribution, high order and excellent performance, which has application value in the field of fuel cells.

[0065] For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and concepts, and all of these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing a high-loaded Pt-based intermetallic compound catalyst, characterized in that: The steps include: S1, mixing the Pt / C catalyst, deionized water and the precursor solution containing metal M by ultrasonication, freezing them into a solid in liquid nitrogen, and drying them in a vacuum freeze dryer, and then performing a low-temperature heat treatment at 300-400° C. in a reducing atmosphere to obtain powder A, which is a Pt / CM alloy; S2, after moistening the powder A obtained in step S1 with deionized water, adding an alkaline solution and a silicon source to the powder A for reaction, filtering to obtain a solid reaction product, washing and drying to obtain a powder B; S3, subjecting the powder B obtained in step S2 to a high temperature heat treatment at 600-800° C. in a non-oxidizing atmosphere to achieve a transformation of the Pt / CM disordered alloy into an ordered alloy, thereby obtaining powder C; S4, adding the powder C obtained in step S3 into a sodium hydroxide solution for reaction, filtering to obtain a solid reactant, washing and drying the solid reactant to obtain a powder D; S5. The powder D obtained in step S4 is sequentially pickled, washed with water and dried to finally obtain an O-PtM / C ordered alloy catalyst, that is, a high-loaded Pt-based intermetallic compound catalyst.

2. The preparation method according to claim 1, characterized in that: In step S1, the metal M is one or more of Co, Cu, Ni and Fe.

3. The preparation method according to claim 1 or 2, characterized in that: In step S1, the precursor solution containing the metal M is one or more of a cobalt nitrate hexahydrate solution, a copper nitrate solution, a nickel nitrate solution, and a ferric nitrate solution.

4. The preparation method according to claim 1, characterized in that: In step S1, the reducing atmosphere is 5-10 vol% H2 / Ar gas, and the low temperature heat treatment time is 2-6 hours.

5. The preparation method according to claim 1, characterized in that: In step S2, the alkaline solution is one of ammonia water, sodium hydroxide solution, and sodium carbonate solution, the silicon source is one of tetraethyl orthosilicate, tetraethoxysilane, and tetramethoxysilane, and the reaction time is 4-10 hours.

6. The preparation method according to claim 1, characterized in that: In step S3, the high temperature heat treatment time is 2-8 hours.

7. The preparation method according to claim 1, characterized in that: In step S4, the temperature for the reaction of powder C with the sodium hydroxide solution is 60-100° C., and the reaction time is 4-12 hours.

8. The preparation method according to claim 1, characterized in that: In step S5, the powder D is pickled with one of 0.5-2 mol / L sulfuric acid solution, perchloric acid solution or nitric acid solution, the pickling temperature is 60-120° C., and the pickling time is 2-8 h.

9. A high-loaded Pt-based intermetallic compound catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. Use of a high-load Pt-based intermetallic compound catalyst prepared by the preparation method according to any one of claims 1 to 8 in a cathode oxygen reduction reaction in a fuel cell.

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