Preparation method and application of a PtM-based intermetallic compound composite catalyst

Abstract

The application discloses a preparation method and application of a PtM intermetallic compound composite catalyst. The method uses carbon-supported Pt nanoparticles as a carrier, loads a nitrogen-containing complex containing a non-noble metal element (M), and performs heat treatment in a reducing atmosphere, so as to obtain a composite structure (PtM / M-N-C) of M / N co-doped carbon modified PtM intermetallic compound nanoparticles. The composite catalyst prepared by the two-step method can obtain an ultra-small particle size, high dispersity and perfect intermetallic compound structure. Compared with a common binary PtM intermetallic compound, the PtM intermetallic compound composite material has the advantages of higher activity and better stability. The catalyst is used for oxygen reduction reaction and methanol oxidation reaction of a fuel cell, and shows good catalytic performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of new energy materials, and particularly relates to a synthesis method and application of a PtM intermetallic compound composite catalyst. BACKGROUND

[0002] Low-temperature fuel cells (including hydrogen fuel cells and direct methanol fuel cells) have the advantages of high energy conversion efficiency, environmental protection and no pollution, and are known as the most important new energy technology in the 21st century. However, due to the limitations of cost and durability, the commercialization of low-temperature fuel cells still faces severe challenges. Among them, the fuel cell catalyst is one of the main factors affecting the performance and cost of fuel cells. Therefore, it is of great significance to develop new high-performance low-platinum electrocatalysts.

[0003] In the past few decades, Pt-based alloy catalysts have been widely studied because they show higher catalytic activity. However, since most of the reported Pt-based alloys are still chemically disordered structures, they will undergo severe structural degradation under long-term operating conditions, leading to catalyst failure. Therefore, such alloy catalysts have not been practically applied to fuel cells.

[0004] Pt-based intermetallic compounds are a new type of low-platinum catalyst developed in recent years. Compared with disordered alloys, Pt-based intermetallic compounds have an atomic ordered structure and can exhibit more excellent activity and stability, and are therefore considered to be a low-platinum catalyst with good application prospects. To achieve the phase transition from disordered alloy to intermetallic compound, the most commonly used method is high-temperature treatment. Therefore, how to effectively control the particle size becomes a key element in the preparation of Pt-based intermetallic compound catalysts.

[0005] At present, researchers have adopted various methods to effectively control the synthesis particle size of Pt-based intermetallic compound catalysts at high temperatures. Chinese invention patent CN 115842136A reports a method for preparing Pt-based intermetallic compound catalysts based on metal nitride confinement. By controlling the deposition step to deposit a controllable metal nitride protective layer around the Pt alloy particles, the confinement effect generated can inhibit the sintering of particles at high temperatures, and the average particle size of the synthesized Pt-based intermetallic compound is less than 4 nm. Chinese invention patent CN 115275233A reports a method for preparing Pt-based intermetallic compound catalysts based on MOF-derived carbon confinement. This method can significantly inhibit the sintering of particles during the pyrolysis process in an inert atmosphere or NH3 atmosphere. The average particle size of the synthesized Pt-based intermetallic compound is only 3 nm. However, such particle size control methods are energy-consuming, time-consuming and tedious, greatly hindering the development of Pt-based intermetallic compound catalysts.

[0006] On the other hand, although the catalytic activity and durability of Pt-based intermetallic compound catalysts have been improved compared to disordered alloys, there is still much room for improvement. Introducing multiple active sites is an effective optimization strategy. For example, Qiao et al. (Qiao Z, et al., Energy Environ. Sci., 2021, 14, 4948) reported a composite electrocatalyst that loaded Pt3Co intermetallic compounds on single-atom Fe-N-C catalysts. Whether in mass activity or durability, it has been significantly improved compared to the corresponding Pt or Pt3Co intermetallic compounds. Xiao et al. (Xiao F, et al., Nat. Catal., 2022, 5, 503) reported a composite electrocatalyst composed of single-atom Pt / Fe and PtFe intermetallic compounds, which has significantly improved mass activity compared to ordinary PtFe intermetallic compounds. Although this optimization strategy has been proven to be effective in improving the performance of catalysts, they often require the use of specific carriers to achieve the effective combination of multiple active components. At the same time, the synthesis method based on M / N-doped carbon carriers often results in a limited variety of Pt-based intermetallic compounds, which is not conducive to the development of Pt-based intermetallic compound catalysts.

[0007] Reasonably designing the synthesis process of Pt-based intermetallic compounds and appropriately introducing multiple active sites to enhance the performance of low-Pt electrocatalysts is a key element to realize the commercialization of Pt-based intermetallic compound catalysts. In view of the above problems, the present application systematically studies the PtM intermetallic compound composite catalyst and its preparation technology, and prepares a variety of high-performance Pt-based intermetallic compound composite catalysts, and successfully applies them to fuel cell reactions. SUMMARY

[0008] The present application overcomes the above-mentioned defects and provides a preparation method and application of a PtM intermetallic compound composite catalyst.

[0009] The object of the present application is achieved by the following technical solutions.

[0010] A preparation method of a PtM intermetallic compound composite catalyst, which loads Pt nanoparticles on common commercial carbon black or directly uses a treated commercial Pt / C catalyst, then mixes with a complex precursor containing non-noble metal elements (M), and forms a composite structure composed of M / N co-doped carbon layers and PtM intermetallic compound nanoparticles through co-reduction heat treatment, to effectively improve the catalytic performance; the catalyst material is a carbon-supported PtM intermetallic compound composite material;

[0011] Specifically includes the following steps:

[0012] (1) Pretreatment of carbon support: Commercial carbon materials XC-72R, Black pearl 2000, Ketjen 300J, etc. are calcined, acid washed, washed with water, and dried for standby use.

[0013] (2) The noble metal precursor, complexing agent, dispersing agent, etc. are added into the same solvent, and then ultrasonic dissolution is performed to mix them uniformly.

[0014] The noble metal precursor includes an acid or salt containing Pt; and the solvent includes one or a combination of two or more of water, alcohol, amide, etc.

[0015] (3) The product obtained in step (1) is impregnated with the solution obtained in step (2), and ultrasonic treatment is performed to make the solution penetrate into the mesoporous channels of the carbon material, and then freeze drying or vacuum drying is performed.

[0016] (4) The dried product obtained in step (3) is reduced by low-temperature calcination in a reducing atmosphere to obtain carbon-supported Pt nanoparticles.

[0017] (5) Pretreatment of commercial Pt / C catalyst: Commercial Pt / C materials (JM 20wt% Pt / C, JM 60wt% Pt / C, etc.) are alcohol washed, water washed, and dried for standby use.

[0018] (6) The non-noble metal precursor, complexing agent, etc. are added into the same solvent, and then ultrasonic dissolution is performed to mix them uniformly; the non-noble metal precursor includes Mn salt, Fe salt, Co salt, Cu salt, or Zn salt; the complexing agent includes 2,2'-dipyridyl, 1,10-phenanthroline, and amino acid; and the solvent includes one or a combination of two or more of water, alcohol, amide, etc.

[0019] (7) The product obtained in step (4) or (5) is impregnated with the solution obtained in step (6), and ultrasonic treatment is performed to make the solution penetrate into the mesoporous channels of the carbon material, and then freeze drying or vacuum drying is performed.

[0020] (8) The dried product obtained in step (6) is calcined at high temperature in a reducing atmosphere to obtain carbon-supported PtM intermetallic compound composite material (PtM / M-N-C).

[0021] In the above method, in step (1), the carbon support includes commercial carbon support (such as XC-72R, Black pearl 2000, Ketjen 300J, etc.), and the calcination process is performed at 800-1000℃ for 1-3 hours in an inert gas atmosphere.

[0022] In the above method, in step (1), the acid washing uses an aqueous solution of HNO3, H2SO4, or HCl with a concentration of 0.5-2 mol / L.

[0023] In the above method, in step (1), the pickling temperature is 60-80℃, and the time is 12-24 hours.

[0024] In the above method, in step (2), the solvent is one or a mixture of two or more of deionized water, anhydrous ethanol, isopropanol, ethylene glycol, and dimethylformamide. The complexing agent includes sodium citrate, ethylenediaminetetraacetic acid, ascorbic acid, and the like; the molar ratio of the noble metal Pt precursor to the complexing agent is 1:5 to 1:3; and the dispersant includes sodium dodecyl sulfonate, cetyl ammonium bromide, polyvinylpyrrolidone, and the like. The addition amount of the dispersant is 0.01-0.1wt%.

[0025] In the above method, in step (3), the impregnation process is to mix the carbon carrier and the noble metal precursor solution sufficiently, the ultrasonic mixing time is 0.5-1.5 hours, and the temperature is 0-5℃, preferably 0℃.

[0026] In the above method, in step (4), the high-temperature calcination has a temperature rising rate of 2-10℃ / min, the calcination temperature is 150-300℃, the calcination time is 1-3 hours, and the atmosphere is a mixed gas of 10% hydrogen and 90% argon.

[0027] In the above method, in step (5), the commercial Pt / C material includes JM 20% Pt / C, JM 60% Pt / C, and the like, and the alcohol washing and water washing include removing impurities such as oil and inorganic salts at low temperature by using isopropanol and deionized water.

[0028] In the above method, in step (6), the solvent is one or a mixture of two or more of deionized water, anhydrous ethanol, isopropanol, ethylene glycol, and dimethylformamide. The complexing agent includes 2,2'-bipyridine, 1,10-phenanthroline, and amino acids.

[0029] In the above method, in step (7), the impregnation process is to mix the carbon carrier and the noble metal precursor solution sufficiently, the ultrasonic mixing time is 0.5-1.5 hours, and the temperature is 0-5℃, preferably 0℃.

[0030] In the above method, in step (8), the high-temperature calcination has a temperature rising rate of 2-10℃ / min, the calcination temperature is 600-900℃, the calcination time is 2-5 hours, and the atmosphere is a mixed gas of 10% hydrogen and 90% argon.

[0031] The composite catalyst prepared by the above method can be applied in a fuel cell catalyst.

[0032] Compared with the prior art, the advantages of the present application are that:

[0033] The application shows a synthesis method of a PtM-based intermetallic compound composite catalyst, which has the advantages of simple method, high efficiency, universality and easy large-scale preparation. The prepared active material shows good catalytic performance in oxygen reduction reaction and methanol oxidation reaction performance test. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 XRD pattern of PtCo / Co-N-C prepared for Example 1.

[0035] Figure 2 TEM pattern of PtCo / Co-N-C prepared for Example 1.

[0036] Figure 3 Oxygen reduction performance curve of PtCo / Co-N-C prepared for Example 1.

[0037] Figure 4 Methanol oxidation performance curve of PtCo / Co-N-C prepared for Example 1.

[0038] Figure 5 XRD pattern of PtZn / Zn-N-C prepared for Example 2.

[0039] Figure 6 XRD pattern of JM 20-PtCo / Co-N-C prepared for Example 3.

[0040] Figure 7 Oxygen reduction performance curve of JM 20-PtCo / Co-N-C prepared for Example 3.

[0041] Figure 8 XRD pattern of JM 60-PtCo / Co-N-C prepared for Example 4.

[0042] Figure 9 Oxygen reduction performance curve of JM 60-PtCo / Co-N-C prepared for Example 4. DETAILED DESCRIPTION

[0043] The application will be further specifically and specifically described in combination with specific examples, but the embodiments of the application are not limited thereto. For the process parameters not specifically indicated, the conventional technology can be referred to.

[0044] The application will be further specifically and specifically described in combination with specific examples, but the embodiments of the application are not limited thereto. For the process parameters not specifically indicated, the conventional technology can be referred to.

[0045] Example 1

[0046] Ketjen 300J (Sionix Japan) was pyrolyzed at 800 °C for 2 h in Ar atmosphere. The carbon powder was acid washed in 2 M HC1 at 80 °C for 12 h, washed with water to neutral pH, and vacuum dried at 60 °C. Chloroplatinic acid, sodium citrate, and sodium dodecylsulfate were dissolved in deionized water and ultrasonically mixed to form a uniform metal precursor solution. The concentration of chloroplatinic acid was 0.08 mol / L, the concentration of sodium citrate was 0.016 mol / L, and the amount of sodium dodecylsulfate added was 0.01 wt%. 200 uL of the metal precursor solution was mixed with 20 mg of the treated Ketjen 300J, the mixture was ultrasonically mixed at 0 °C for 1.5 h, and then freeze-dried. The dried powder product was calcined at 300 °C for 2 h in a 10% H2 / 90% Ar atmosphere. The calcined product was co-impregnated with an aqueous solution containing 0.02 mmol of cobalt chloride and 10 mg of 1,10-phenanthroline, the mixture was ultrasonically mixed at 0 °C for 1.5 h, and then freeze-dried. The dried powder product was calcined at 750 °C for 2.5 h in a 10% H2 / 90% Ar atmosphere. A fuel cell catalyst was obtained.

[0047] Example 2

[0048] Ketjen 300J (Sionix Japan) was pyrolyzed at 800 °C for 2 h in Ar atmosphere. The carbon powder was acid washed in 2 M HC1 at 80 °C for 12 h, washed with water to neutral pH, and vacuum dried at 60 °C. Chloroplatinic acid, sodium citrate, and sodium dodecylsulfate were dissolved in deionized water and ultrasonically mixed to form a uniform metal precursor solution. The concentration of chloroplatinic acid was 0.08 mol / L, the concentration of sodium citrate was 0.016 mol / L, and the amount of sodium dodecylsulfate added was 0.01 wt%. 200 uL of the metal precursor solution was mixed with 20 mg of the treated Ketjen 300J, the mixture was ultrasonically mixed at 0 °C for 1.5 h, and then freeze-dried. The dried powder product was calcined at 300 °C for 2 h in a 10% H2 / 90% Ar atmosphere. The calcined product was co-impregnated with an aqueous solution containing 0.02 mmol of zinc chloride and 10 mg of 1,10-phenanthroline, the mixture was ultrasonically mixed at 0 °C for 1.5 h, and then freeze-dried. The dried powder product was calcined at 750 °C for 2.5 h in a 10% H2 / 90% Ar atmosphere. A fuel cell catalyst was obtained.

[0049] Example 3

[0050] A 20 mg commercial JM 20 wt% Pt / C catalyst (J. M. Huber) was dispersed in a mixture of isopropanol and deionized water, stirred at room temperature for 4 h, filtered by suction, washed with deionized water three times, and vacuum dried at 40 °C. The dried powder was co-impregnated with an aqueous solution containing 0.02 mmol cobalt chloride, 10 mg 1,10-phenanthroline, and the mixture was sonicated at 0 °C for 1.5 h, and freeze-dried. The dried powder product was calcined at 750 °C for 2.5 h under a 10% H2 / 90% Ar atmosphere. A fuel cell catalyst was obtained.

[0051] Example 4

[0052] A 20 mg commercial JM 60 wt% Pt / C catalyst (J. M. Huber) was dispersed in a mixture of isopropanol and deionized water, stirred at room temperature for 4 h, filtered by suction, washed with deionized water three times, and vacuum dried at 40 °C. The dried powder was co-impregnated with an aqueous solution containing 0.06 mmol cobalt chloride, 10 mg 1,10-phenanthroline, and the mixture was sonicated at 0 °C for 1.5 h, and freeze-dried. The dried powder product was calcined at 750 °C for 2.5 h under a 10% H2 / 90% Ar atmosphere. A fuel cell catalyst was obtained.

[0053] Example 5

[0054] A 5 mg of the active material prepared in Examples 1-4 was weighed into a mixture of 25 μL Nafion (5%) solution, 475 μL ethanol, and 500 μL deionized water, and 5 μL of the mixture was dropped onto the surface of a glassy carbon electrode after uniform dispersion. The glassy carbon electrode was dried and tested for oxygen reduction catalytic activity in a 0.1 M HCIO4 solution and for methanol oxidation catalytic activity in a mixture of 0.1 M HCIO4 and 0.5 M methanol. The oxygen reduction polarization curve and the methanol oxidation voltammogram of the PtCo intermetallic compound composite catalyst prepared in Example 1 are shown in Figs. 1 and 2, respectively, and show much better oxygen reduction and methanol oxidation activity than the corresponding PtCo intermetallic compound and commercial carbon-supported platinum. The oxygen reduction polarization curves of the PtCo intermetallic compound composite catalysts prepared in Example 3 and Example 4 are shown in Figs. 3 and 4, respectively, and show better oxygen reduction activity than the corresponding PtCo intermetallic compound and commercial carbon-supported platinum. Figure 3 、 4 Figure 7 、 9

[0055] ​​The above embodiments of the present application are merely used for clearly illustrating the present application, but not for limiting the present application. Based on the above description, any modification, equivalent replacement and improvement made by those skilled in the art should be included in the protection scope of the present application.

Claims

1. A method for preparing a PtM intermetallic compound composite catalyst, characterized by, The two-step method is used to prepare: first, Pt nanoparticles are loaded on carbon black, or a treated Pt / C catalyst is directly used; then, a complex precursor containing a non-noble metal element M is mixed, and a composite structure composed of M / N co-doped carbon layers and PtM intermetallic compound nanoparticles is formed through co-reduction heat treatment; the non-noble metal M is Mn, Fe, Co, Cu or Zn; and the complexing agent in the complex precursor is 2,2'-dipyridyl, 1,10-phenanthroline or an amino acid; Specifically comprising the following steps: (1) Pretreatment of the carbon carrier: the carbon material is calcined, acid washed, washed with water, and dried for standby; the carbon material includes XC-72R, Black pearl 2000 or Ketjen 300J; the calcination process is carried out in an inert gas atmosphere at 800-1000℃ for 1-3 hours; The acid washing uses an aqueous solution of HNO3, H2SO4 or HCl with a concentration of 0.5-2 mol / L; The acid washing temperature is 60-80℃, and the time is 12-24 hours; (2) The noble metal Pt precursor, a complexing agent and a dispersing agent are added to the same solvent, and then ultrasonic dissolution is performed to mix them uniformly; the noble metal Pt precursor includes an acid or a salt containing Pt; the solvent is one or more of deionized water, anhydrous ethanol, isopropanol, ethylene glycol and dimethylformamide (DMF); the complexing agent includes sodium citrate, ethylenediaminetetraacetic acid or ascorbic acid; the molar ratio of the noble metal Pt precursor to the complexing agent is 1:5 to 1:3; and the dispersing agent includes sodium dodecyl sulfonate, cetyl ammonium bromide or polyvinylpyrrolidone; the addition amount of the dispersing agent is 0.01-0.1 wt%; (3) The product obtained in step (1) is impregnated with the solution obtained in step (2), and ultrasonic is used to make the solution enter the mesoporous channels of the carbon material, and then freeze drying or vacuum drying is adopted; the impregnation process is to mix the carbon carrier and the noble metal Pt precursor solution sufficiently, and the ultrasonic mixing time is 0.5-1.5 hours at a temperature of 0-5℃; (4) The dried product obtained in step (3) is subjected to low-temperature calcination and reduction treatment in a reducing atmosphere to obtain carbon-supported Pt nanoparticles; the low-temperature calcination has a heating rate of 2-10℃ / min; the calcination temperature is 150-300℃, and the calcination time is 1-3 hours; and the atmosphere is a mixed gas of 10% hydrogen and 90% argon by volume percentage; (5) Pretreatment of the commercial Pt / C catalyst: the Pt / C material is subjected to alcohol washing, water washing and drying for standby; (6) adding non-noble metal precursors and complexing agents into the same solvent, and then ultrasonic dissolving and mixing uniformly; the non-noble metal precursors include Mn salt, Fe salt, Co salt, Cu salt or Zn salt; the complexing agents include 2,2'-dipyridyl, 1,10-phenanthroline or amino acid; the solvent includes one or more of water, alcohol and amide; the molar ratio of the non-noble metal precursors added to the noble metal Pt precursors added in step (2) is 1.2:1 to 1:1, and the mass ratio of the added complexing agent to the carbon material is 1:4 to 1:1; (7) immersing the product obtained in step (4) or (5) in the solution obtained in step (6) by ultrasonic, and then using freeze drying or vacuum drying; (8) calcining the dried product obtained in step (7) at high temperature in a reducing atmosphere to obtain a carbon-supported PtM intermetallic compound composite material PtM / M-N-C.

2. The method of claim 1, wherein the PtM intermetallic compound composite catalyst is prepared by the steps of: In step (5), the Pt / C material includes JM 20% Pt / C or JM 60% Pt / C, and the alcohol washing and water washing include removing oil and inorganic salt impurities at low temperature by using isopropyl alcohol and deionized water.

3. The method for preparing the PtM-based intermetallic compound composite catalyst according to claim 1, characterized in that, In step (7), the immersion process is to mix the carbon carrier and the noble metal Pt precursor solution sufficiently, and the ultrasonic mixing time is 0.5-1.5 hours and the temperature is 0-5℃.

4. The method for preparing the PtM-based intermetallic compound composite catalyst according to claim 1, characterized in that, In step (8), the heating rate of the high-temperature calcination is 2-10℃ / min; the calcination temperature is 600-900℃, the calcination time is 2-5 hours; and the atmosphere is a mixed gas of 10% hydrogen and 90% argon by volume percentage.

Images