A platinum-lanthanide intermetallic compound catalyst with high platinum loading and a preparation method and application thereof

Abstract

The application discloses a platinum-lanthanide intermetallic compound catalyst with high platinum loading and a preparation method and application thereof. The method is characterized in that: first, p-phenylenediamine is used to modify the amino group of carbon black; then, by virtue of electrostatic adsorption between the positive charge of the amino group and the anion of a platinum precursor, nucleation sites uniformly distributed on the surface of a carbon carrier are introduced, so that platinum nanoparticles are loaded on the carrier in a highly dispersed state; in the subsequent high-temperature heat treatment process, the amino functional groups on the surface of the carbon carrier produce an anchoring effect on the metal particles through carrier-metal interaction, effectively inhibiting particle migration and agglomeration, and a platinum-lanthanide intermetallic compound catalyst with an average particle size of less than 4 nm and a platinum loading of more than 20 wt% is prepared. The obtained catalyst is suitable for a cathode oxygen reduction reaction of a proton exchange membrane fuel cell and an anode methanol oxidation reaction of a direct methanol fuel cell, and exhibits excellent catalytic activity, stability and CO poisoning resistance.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic materials technology, and more specifically, to a platinum-lanthanide intermetallic compound catalyst with high platinum loading, its preparation method, and its application. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) are considered promising clean energy technologies due to their high energy conversion efficiency and environmental friendliness. However, their commercialization is still hampered by the slow electrode reaction kinetics: PEMFCs have a high overpotential for the oxygen reduction reaction (ORR) at the cathode, while DMFCs have sluggish kinetics for the methanol oxidation reaction (MOR) at the anode and are susceptible to poisoning by CO intermediates. Currently, commercially available carbon-supported platinum (Pt / C) catalysts exhibit high activity, but platinum resources are scarce and expensive, and they are prone to particle agglomeration and activity decay during long-term operation.

[0003] Alloying platinum with 3d transition metals (such as Fe, Co, and Ni) can improve activity while reducing the amount of platinum required. However, transition metals are easily dissolved in acidic environments, leading to catalyst deactivation and poisoning of the proton exchange membrane. Intermetallic compounds formed by rare earth metals (REMs) and platinum exhibit stronger stability and corrosion resistance in acidic media. Their unique 4f electronic structure can also effectively modulate the electronic properties of platinum and optimize the adsorption energy of intermediates. However, the preparation of platinum-rare earth nanoalloys faces two major challenges: first, rare earth metals have extremely low reduction potentials and strong oxygen affinity, easily forming oxides rather than alloys under conventional conditions; second, the high-temperature (≥600℃) annealing required for atomic ordering inevitably leads to particle sintering. Therefore, currently reported platinum-rare earth alloy catalysts generally suffer from either excessively large particle size or low platinum loading, making it difficult to achieve both simultaneously and severely restricting their practical application.

[0004] In recent years, researchers have attempted to prepare platinum-lanthanide intermetallic compound catalysts through different synthetic strategies. For example, the literature (Ultra-stable Pt5La intermetallic compound towards highly efficient oxygen reduction reaction[J]. Nano Research,2023,16(2):2035-2040.) uses lanthanum-based metal-organic frameworks (La-MOF) as a precursor, and prepares Pt5La intermetallic compound catalysts through high-temperature carbonization and annealing treatment, achieving a maximum power density of 794 mW / cm³ in hydrogen / air fuel cells. 2 However, this route involves the pre-preparation of MOF precursors, which is a complex process, and the catalyst has a low platinum loading (about 7 wt%), leaving room for further reduction in particle size.

[0005] Therefore, there is an urgent need to develop a simple and universal preparation method that can achieve the controllable synthesis of small-sized, high-platinum-loaded platinum-lanthanide intermetallic compound catalysts under mild conditions. Summary of the Invention

[0006] Therefore, it is necessary to address the above-mentioned technical problems by providing a platinum-lanthanide intermetallic compound catalyst with high platinum loading, its preparation method, and its application.

[0007] The present invention provides a first aspect of a method for preparing a platinum-lanthanide intermetallic compound catalyst with high platinum loading, comprising the following steps: (1) Disperse carbon black in deionized water, add p-phenylenediamine and concentrated sulfuric acid, sonicate in a water bath and then heat in an oil bath to react, adding NaNO2 solution dropwise during the reaction. After the reaction is completed, after post-treatment, amino-modified carbon black is obtained. (2) Disperse the amino-modified carbon black obtained in step (1) in ethylene glycol solution, add chloroplatinic acid hydrate, sonicate in water bath and then heat in oil bath to react. After the reaction is completed, post-treatment is performed to obtain carbon-supported platinum. (3) Disperse the carbon-supported platinum obtained in step (2) in deionized water, add lanthanide metal chloride, heat and stir in an oil bath until dry, heat the resulting powder at 750~950℃ for 1~3 hours in a reducing atmosphere, treat the product in an acid solution, wash and dry it, and then heat treat it again in a reducing atmosphere to obtain the product.

[0008] Furthermore, the lanthanide chloride mentioned in step (3) is any one of samarium chloride hexahydrate, lanthanum chloride heptahydrate, or cerium chloride heptahydrate; the amount of lanthanide chloride added is calculated based on an atomic ratio of Pt to lanthanide metal of 4~6:1.

[0009] Furthermore, in step (1), the mass ratio of carbon black to p-phenylenediamine is 1:0.5~0.7, the concentration of the NaNO2 solution is 0.5~2.0 mg / mL, the temperature of the oil bath heating is 50~80℃, and the reaction time is 12~20 hours.

[0010] Furthermore, in step (2), the volume fraction of the ethylene glycol solution is 40% to 80%, the amount of chloroplatinic acid added is calculated as 15 to 25 wt% of platinum loading in carbon-supported platinum, the temperature of the oil bath heating is 120 to 160°C, and the reaction time is 4 to 8 hours.

[0011] Furthermore, the reducing atmosphere in step (3) is an argon-hydrogen mixed atmosphere containing 3%~10% H2; the heat treatment temperature is 850℃ and the time is 1~3 hours; the acid solution is a 0.05~0.2mol / L perchloric acid solution, the treatment temperature is 40~80℃ and the treatment time is 4~8 hours; the re-heat treatment temperature is 350~450℃ and the time is 0.5~2 hours.

[0012] Furthermore, the lanthanide chloride mentioned in step (3) is samarium chloride hexahydrate.

[0013] The present invention also provides a platinum-lanthanide intermetallic compound catalyst with high platinum loading, which is prepared by the above preparation method; in the catalyst, platinum-lanthanide intermetallic compound nanoparticles are uniformly dispersed on the surface of a carbon support, with an average particle size of less than 4 nm and a platinum loading of more than 20 wt%.

[0014] Furthermore, the platinum-lanthanide intermetallic compound has a hexagonal crystal structure and the chemical formula Pt5RE, wherein RE is any one of La, Ce or Sm.

[0015] The present invention also provides the application of the above-described catalyst in the cathode of a proton exchange membrane fuel cell.

[0016] The present invention also provides the application of the above-described catalyst in the anode of a direct methanol fuel cell.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing a platinum-lanthanide intermetallic compound catalyst with high platinum loading. First, carbon black is modified with p-phenylenediamine. Utilizing the electrostatic adsorption between the positive charge of the amino group and the platinum precursor anion, a large number of uniformly distributed nucleation sites are introduced on the carbon support surface, promoting highly dispersed platinum nanoparticles loaded onto the support. During subsequent high-temperature heat treatment, the amino functional groups on the carbon support surface anchor the metal particles through support-metal interactions, effectively inhibiting particle migration and agglomeration. This overcomes the inherent defect of severe particle sintering during high-temperature annealing in traditional platinum-rare earth alloy preparation methods, successfully obtaining a Pt5RE intermetallic compound catalyst with an average particle size of less than 4 nm and a platinum loading of more than 20 wt%, solving the long-standing technical challenge of achieving both small size and high loading. Furthermore, this method is simple to operate, operates under mild conditions, has good reproducibility, does not require a strictly anhydrous and oxygen-free environment, and is applicable to various lanthanide metals such as La, Ce, and Sm, providing a widely applicable technical route for the controllable synthesis of platinum-lanthanide intermetallic compound catalysts.

[0018] The obtained catalyst is suitable for the oxygen reduction reaction at the cathode of a proton exchange membrane fuel cell and the methanol oxidation reaction at the anode of a direct methanol fuel cell, and exhibits excellent catalytic activity, stability and resistance to CO poisoning. Attached Figure Description

[0019] Figure 1A The X-ray diffraction pattern of the Pt5Sm / C catalyst obtained in Example 1 is shown below. Figure 1B Transmission electron microscopy image of the Pt5Sm / C catalyst obtained in Example 1; Figure 1C The particle size distribution diagram of the Pt5Sm / C catalyst obtained in Example 1 is shown. Figure 2A The X-ray diffraction pattern of the Pt5La / C catalyst obtained in Example 2 is shown below. Figure 2B Transmission electron microscopy (TEM) image of the Pt5La / C catalyst obtained in Example 2; Figure 2C The particle size distribution diagram of the Pt5La / C catalyst obtained in Example 2 is shown. Figure 3A The X-ray diffraction pattern of the Pt5Ce / C catalyst obtained in Example 3; Figure 3B Transmission electron microscopy image of the Pt5Ce / C catalyst obtained in Example 3; Figure 3C The particle size distribution diagram of the Pt5Ce / C catalyst obtained in Example 3 is shown. Figure 4A Transmission electron microscopy image of the Pt5Sm / C catalyst heat-treated at 750℃ obtained in Example 4; Figure 4B The particle size distribution diagram is shown for the Pt5Sm / C catalyst heat-treated at 750℃ obtained in Example 4. Figure 5A Transmission electron microscopy image of the Pt5Sm / C catalyst heat-treated at 950℃ obtained in Example 5; Figure 5B The particle size distribution diagram is shown for the Pt5Sm / C catalyst obtained in Example 5 after heat treatment at 950℃. Figure 6A Transmission electron microscopy (TEM) image of the non-amino-modified Pt5Sm / C catalyst obtained in Comparative Example 1. Figure 6B The particle size distribution diagram of the non-amino-modified Pt5Sm / C catalyst obtained in Comparative Example 1 is shown. Figure 7A Transmission electron microscopy image of the low-load Pt seed (8wt%) Pt5Sm / C catalyst obtained in Comparative Example 2; Figure 7BThe particle size distribution of the low-load Pt seed (8wt%) Pt5Sm / C catalyst obtained in Comparative Example 2 is shown. Figure 8 To verify the ORR polarization curves of the Pt5Ce / C, Pt5Sm / C and Pt5La / C catalysts in 0.1 mol / L HClO4 solution in Example 1; Figure 9 To verify the cyclic voltammetry curves of the Pt5Ce / C, Pt5Sm / C, ​​and Pt5La / C catalysts in Example 2 in a 0.1 mol / L HClO4 solution containing 0.5 mol / L methanol; Figure 10 To verify the X-ray diffraction patterns of the Pt5Sm / C catalysts prepared at different heat treatment temperatures (750℃, 850℃, 950℃) in Example 3; Figure 11 To verify the ORR polarization curves of the Pt5Sm / C catalyst prepared at different heat treatment temperatures (750℃, 850℃, 950℃) in 0.1mol / L HClO4 solution in Example 3; Figure 12 To verify the cyclic voltammetry curves of the Pt5Sm / C catalyst prepared at different heat treatment temperatures (750℃, 850℃, 950℃) in Example 3 in a 0.1mol / L HClO4 solution containing 0.5mol / L methanol; Figure 13A To verify the ORR polarization curves of Pt5Sm / C and commercial Pt / C catalyst before and after 30,000 potential cycling tests in Example 4; Figure 13B To verify the cyclic voltammetry curves of Pt5Sm / C and commercial Pt / C catalyst before and after 30,000 potential cycles in Example 4; Figure 14A To verify the cyclic voltammetry curves of Pt5Sm / C, ​​commercial Pt / C, and commercial PtRu / C catalysts in Example 5 in a 0.1 mol / L HClO4 solution containing 0.5 mol / L methanol; Figure 14B To verify the chronoamperometric test curves of Pt5Sm / C, ​​commercial Pt / C, and commercial PtRu / C catalysts at a potential of 0.8V in Example 5; Figure 15A To verify the performance curves of hydrogen / air fuel cells using Pt5Sm / C and commercial Pt / C as cathode catalysts in Example 6; Figure 15B To verify the performance curves of hydrogen / oxygen fuel cells using Pt5Sm / C and commercial Pt / C as cathode catalysts in Example 6; Figure 16To verify the performance curves of direct methanol fuel cells using Pt5Sm / C, ​​commercial Pt / C, and commercial PtRu / C as anode catalysts in Example 7; Figure 17 To verify the performance curves of hydrogen / air fuel cells using Pt5Sm / C and commercial Pt / C as cathode catalysts in Example 8 before and after accelerated aging tests; Figure 18A To verify the transmission electron microscope image of the Pt5Sm / C catalyst in Example 8 after accelerated aging test in a battery; Figure 18B To verify the particle size distribution of the Pt5Sm / C catalyst in Example 8 after accelerated aging test in a battery. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0021] The main raw materials and their sources used in the various embodiments and comparative examples of this invention are shown in Table 1 below:

[0022] The main instruments used in the various embodiments and comparative examples of this invention are shown in Table 2 below:

[0023] Example 1

[0024] This embodiment provides a method for preparing a platinum-lanthanide intermetallic compound catalyst with high platinum loading. The specific steps are as follows: (1) Preparation of amino-modified carbon black: Take 200 mL of deionized water in a flask, add 200 mg of commercial carbon black Ketjen Black EC300J, and stir magnetically until completely dispersed. Then, add 112 mg of p-phenylenediamine and 60 µL of concentrated sulfuric acid sequentially. After sonicating in a water bath for 30 minutes, heat in an oil bath at 60 °C for 16 hours, adding 72 mL of NaNO2 solution (1.0 mg / mL) dropwise during this period. After cooling to room temperature, wash the product with ethanol and deionized water by vacuum filtration, and dry under vacuum at 65 °C for 12 hours to obtain amino-modified carbon black.

[0025] (2) Preparation of carbon-supported platinum: Take 200 mL of 60% (v / v) ethylene glycol solution in a flask, add 200 mg of the prepared amino-modified carbon black, stir magnetically until completely dispersed, and then add 0.205 mmol H2PtCl6·6H2O. After sonicating in a water bath for 30 minutes, heat the reaction in an oil bath at 140 °C for 6 hours, cool to room temperature, wash the product with ethanol and deionized water by vacuum filtration, and dry under vacuum at 65 °C for 12 hours to obtain 20 wt% Pt / C.

[0026] (3) Preparation of carbon-supported platinum-samarium catalyst: Take 50 mL of deionized water in a beaker, add 120 mg of the prepared 20 wt% Pt / C, and then add 44.87 mg of SmCl3·6H2O. Heat the beaker in an oil bath at 60 °C and stir magnetically until dry. Then place the dried powder in a tube furnace and heat-treat at 850 °C for 2 hours in a mixed atmosphere of 5% H2 / 95% Ar. Treat the product in a 0.1 mol / L perchloric acid solution at 60 °C for 6 hours to remove oxide byproducts. Then filter and wash with deionized water, dry under vacuum at 65 °C for 12 hours, and then place it in a tube furnace and heat-treat at 400 °C for 1 hour in a mixed atmosphere of 5% H2 / 95% Ar to obtain the carbon-supported platinum-samarium catalyst, denoted as Pt5Sm / C.

[0027] Characterization of Results in Example 1: The Pt5Sm / C catalyst obtained in Example 1 was characterized by XRD and TEM. The results are as follows: Figures 1A-1C As shown. Figure 1A XRD patterns showed that the main phase structure of the Pt5Sm / C catalyst was a hexagonal Pt5Sm / C intermetallic compound, and no characteristic diffraction peaks of samarium oxide were observed, indicating that acid leaching effectively removed byproducts. ICP-OES analysis showed that the Pt loading of the catalyst was 20.9 wt%, and the Pt / Sm atomic ratio was 8.6, higher than the theoretical atomic ratio (5:1) of the Pt5Sm / C intermetallic compound. This is attributed to the Pt-rich surface structure formed after acid leaching. Figure 1B TEM images show that Pt5Sm / C nanoparticles are uniformly dispersed on the carbon support surface without obvious aggregation. Figure 1C The particle size statistics show that the average particle size of the nanoparticles is 3.8±1.0 nm, realizing the controllable preparation of small-sized intermetallic compound nanoparticles.

[0028] Example 2

[0029] This embodiment provides a method for preparing a platinum-lanthanide intermetallic compound catalyst with high platinum loading. The difference between this method and Example 1 is that in step (3), 46.14 mg of LaCl3·7H2O is added instead of SmCl3·6H2O. The remaining steps are the same, and a carbon-supported platinum-lanthanum catalyst is obtained, denoted as Pt5La / C.

[0030] Characterization of Example 2: The Pt5La / C catalyst obtained in Example 2 was characterized by XRD and TEM. The results are as follows: Figures 2A-2C As shown. By Figure 2A XRD analysis revealed that the main phase of the Pt5La / C catalyst was a hexagonal Pt5La intermetallic compound structure, and no characteristic peaks of lanthanum oxide were observed. ICP-OES analysis showed that the Pt loading of this catalyst was 23.3 wt%, and the Pt / La atomic ratio was 8.2, higher than the theoretical atomic ratio of Pt5La intermetallic compounds (5:1), which is also attributed to the Pt-rich surface structure formed after acid leaching. Figure 2B The TEM images show that Pt5La nanoparticles are uniformly dispersed on the surface of the carbon support. Figure 2C The particle size statistics show that the average particle size of the nanoparticles is approximately 3.9 ± 0.8 nm.

[0031] Example 3

[0032] This embodiment provides a method for preparing a platinum-lanthanide intermetallic compound catalyst with high platinum loading. The difference between this method and Example 1 is that in step (3), 46.32 mg CeCl3·7H2O is added instead of SmCl3·6H2O. The remaining steps are the same, and a carbon-supported platinum-cerium catalyst is obtained, denoted as Pt5Ce / C.

[0033] Characterization of Results in Example 3: The Pt5Ce / C catalyst obtained in Example 3 was characterized by XRD and TEM, and the results are shown in Figure 3. Figure 3A XRD analysis revealed that the main phase of the Pt5Ce / C catalyst was a hexagonal Pt5Ce intermetallic compound structure, and no characteristic peaks of cerium oxide were observed. ICP-OES analysis showed that the Pt loading of this catalyst was 21.7 wt%, and the Pt / Ce atomic ratio was 7.4, higher than the theoretical atomic ratio of Pt5Ce intermetallic compounds (5:1), attributed to the Pt-rich surface structure formed after acid leaching. Figure 3B The TEM images show that Pt5Ce nanoparticles are uniformly dispersed on the surface of the carbon support. Figure 3C The particle size statistics show that the average particle size of the nanoparticles is 3.5 ± 0.8 nm.

[0034] Example 4

[0035] This embodiment provides a method for preparing a platinum-lanthanide intermetallic compound catalyst, which differs from Example 1 in that: in step (3), after the dry powder is placed in a tube furnace, it is heat-treated at 750°C for 2 hours in a 5% H2 / 95% Ar mixed atmosphere, and the remaining steps are the same to obtain the Pt5Sm / C catalyst.

[0036] Characterization of results in Example 4: Figure 4A and 4B Transmission electron microscopy (TEM) images and particle size distribution diagrams of the Pt5Sm / C catalyst prepared by heat treatment at 750℃ are shown. Figure 4A It can be observed that the Pt5Sm nanoparticles prepared by heat treatment at 750℃ are uniformly dispersed on the surface of the carbon support, without obvious agglomeration. Figure 4B The particle size statistics show that the average particle size of the nanoparticles is 3.5±0.8nm, which is comparable to that of the sample heat-treated at 850℃ (3.8nm), indicating that low-temperature heat treatment can also effectively inhibit particle growth.

[0037] Example 5

[0038] This embodiment provides a method for preparing a platinum-lanthanide intermetallic compound catalyst, which differs from Example 1 in that: in step (3), after the dry powder is placed in a tube furnace, it is heat-treated at 950°C for 2 hours in a 5% H2 / 95% Ar mixed atmosphere, and the remaining steps are the same to obtain the Pt5Sm / C catalyst.

[0039] Characterization of results in Example 5: Figure 5A and 5B Transmission electron microscopy (TEM) images and particle size distribution diagrams of the Pt5Sm / C catalyst prepared by heat treatment at 950℃ are shown. Figure 5A The transmission electron microscopy (TEM) images show that the Pt5Sm nanoparticles prepared by heat treatment at 950℃ exhibit obvious aggregation. Figure 5B The particle size statistics show that high-temperature heat treatment significantly increased the average particle size of nanoparticles to 6.0±1.9 nm, indicating that excessively high heat treatment temperature will intensify particle sintering and is not conducive to the preservation of small-sized nanoparticles.

[0040] Comparative Example 1 This comparative example provides a method for preparing a platinum-lanthanide intermetallic compound catalyst, which differs from Example 1 in that: in step (1), the carbon support uses original unmodified KB carbon black without amino modification treatment, and the other steps are the same, and the resulting catalyst is denoted as unmodified Pt5Sm / C.

[0041] Characterization of the results of Comparative Example 1: Figure 6A and 6B Transmission electron microscopy (TEM) images and particle size distribution diagrams of the Pt5Sm / C catalyst prepared without amino modification are shown. Figures 6A-6BIt can be seen that the Pt5Sm catalyst obtained by using unmodified raw KB carbon black exhibits significant particle agglomeration and significantly poor dispersibility, with an average particle size of 8.8±2.7 nm, which is much larger than the catalyst prepared by amino modification in Example 1 (3.8 nm). This result indicates that amino modification plays a key role in regulating the uniform deposition of platinum particles and inhibiting particle migration and sintering during high-temperature heat treatment. The mechanism is that the positive charge introduced by amino modification can anchor the metal precursor through electrostatic interaction, thereby effectively limiting particle migration and agglomeration during subsequent high-temperature treatment.

[0042] Comparative Example 2 This comparative example provides a method for preparing a platinum-lanthanide intermetallic compound catalyst, which differs from Example 1 in that: in step (2) when preparing carbon-supported platinum, the amount of chloroplatinic acid added is adjusted to be based on the platinum loading in the carbon-supported platinum being 8wt%, and the other steps are the same. The resulting catalyst is denoted as low-loading seed Pt5Sm / C.

[0043] Characterization of the results of Comparative Example 2: Figures 7A-7B Transmission electron microscopy (TEM) images and particle size distribution maps of the Pt5Sm / C catalyst prepared using 8 wt% Pt / C as a seed are shown. When using a lower loading of 8 wt% Pt / C as a seed to prepare the Pt5Sm / C catalyst, although the Pt5Sm nanoparticles are still relatively uniformly dispersed on the carbon support surface, the particle size is significantly larger than in Example 1, with an average particle size of 5.2 ± 1.5 nm, an increase of approximately 37% compared to the 20 wt% Pt seed sample (3.8 nm) in Example 1. This result indicates that a higher loading of Pt seeds helps to form sufficient nucleation sites on the carbon support surface, effectively suppressing particle sintering during subsequent high-temperature alloying, and is one of the key factors in obtaining small-sized intermetallic compound catalysts.

[0044] Verification Example 1 To verify the applicability of the amino-assisted preparation method of the present invention to different lanthanide metal elements, the ORR catalytic activity of the obtained platinum-lanthanide intermetallic compound catalysts was tested according to the following method: Pt5Sm / C obtained in Example 1, Pt5La / C obtained in Example 2, and Pt5Ce / C obtained in Example 3 were used to prepare working electrodes under the same conditions, and ORR polarization curves were tested in 0.1 mol / L HClO4 solution.

[0045] The results are as follows Figure 8As shown, the ORR mass activities of Pt5Ce / C, Pt5Sm / C, ​​and Pt5La / C catalysts at 0.9 V are 372 mA / mgPt, 410 mA / mgPt, and 300 mA / mgPt, respectively, all significantly better than the commercial Pt / C catalyst (240 mA / mgPt). Among them, the Pt5Sm / C catalyst exhibits the highest ORR mass activity, indicating that it has the best ORR catalytic activity. The excellent ORR performance of all three catalysts confirms that the amino-assisted preparation strategy described in this invention can be universally applied to the preparation of various platinum-lanthanide (La, Ce, Sm) intermetallic compound catalysts, demonstrating good versatility.

[0046] Verification Example 2 To verify the catalytic activity of the amino-assisted preparation method of the present invention for different lanthanide metal elements in the methanol oxidation reaction, the MOR catalytic activity of the obtained platinum-lanthanide intermetallic compound catalysts was tested according to the following method: working electrodes were prepared from the Pt5Sm / C catalyst obtained in Example 1, the Pt5La / C catalyst obtained in Example 2, and the Pt5Ce / C catalyst obtained in Example 3, respectively, and placed in a 0.1mol / L HClO4 solution containing 0.5mol / L methanol, and cyclic voltammetry curves were recorded.

[0047] The results are as follows Figure 9 As shown, the MOR forward scan current densities for Pt5Ce / C, Pt5Sm / C, ​​and Pt5La / C catalysts are 9.95 mA / cm², respectively. 2 11.30 mA / cm 2 and 11.15 mA / cm 2 Among them, the Pt5Sm / C catalyst exhibited the highest MOR current density, indicating that it had the best MOR catalytic activity. All three catalysts showed good catalytic activity in the MOR test, further verifying the universality of the method of this invention for different lanthanide systems.

[0048] Verification Example 3 To determine the optimal heat treatment temperature, the effects of different annealing temperatures on the structural order, particle size, and catalytic performance of the Pt5Sm / C catalyst were investigated using the following method: The Pt5Sm / C catalysts obtained in Example 1 (850℃), Example 4 (750℃), and Example 5 (950℃) were characterized by XRD, and the results are as follows: Figure 10 As shown. Further tests were conducted according to the methods described in Verification Example 1 and Verification Example 2, testing their ORR and MOR catalytic activities, respectively. The results are as follows. Figure 11 and Figure 12 As shown.

[0049] (1) XRD phase analysis results are as follows Figure 10As shown, hexagonal Pt5Sm intermetallic compounds were successfully prepared by heat treatment at 750℃, 850℃, and 950℃. With increasing heat treatment temperature, the diffraction peak intensity of Pt5Sm gradually increased while the peak width gradually narrowed, indicating that its crystallinity and order significantly improved with increasing temperature. Specifically, the Pt5Sm / C catalyst obtained by heat treatment at 750℃ exhibited a relatively broad diffraction peak and lower crystallinity; after heat treatment at 850℃, the diffraction peaks significantly increased, indicating a substantial improvement in order; and the product obtained by heat treatment at 950℃ had the highest crystallinity and order.

[0050] (2) ORR catalytic performance test ORR polarization curves of Pt5Sm / C catalysts prepared at three different heat treatment temperatures were tested according to the method described in Verification Example 1. The results are as follows: Figure 11 As shown, the ORR mass activities (at 0.9V potential) of the Pt5Sm / C catalysts obtained by heat treatment at 750℃, 850℃, and 950℃ were 297 mA / mgPt, 410 mA / mgPt, and 238 mA / mgPt, respectively. Among them, the catalyst obtained by heat treatment at 850℃ had the highest ORR mass activity, approximately 1.4 times that of the sample at 750℃ and 1.7 times that of the sample at 950℃.

[0051] Analysis of XRD and TEM results from the examples shows that while the catalyst obtained at 750℃ had the smallest particle size (3.5 nm), its low heat treatment temperature resulted in insufficient atomic mobility and a low degree of ordering in the Pt5Sm intermetallic compound. Many atoms remained in a disordered or partially ordered state, failing to form a complete hexagonal intermetallic compound structure, leading to a weakened alloying effect and insufficient ORR activity. Although the catalyst obtained at 950℃ had the highest crystallinity and order, the excessively high heat treatment temperature caused severe sintering and agglomeration of the particles, increasing the average particle size to 6.0 nm and significantly reducing the electrochemical active area, thus resulting in a substantial decrease in ORR activity. 850℃ was the optimal heat treatment temperature, providing sufficient migration energy to overcome the strain energy caused by atomic size mismatch in the Pt-Sm system, achieving a highly ordered hexagonal Pt5Sm intermetallic compound structure. Simultaneously, the amino functional groups effectively anchored the particles, inhibiting sintering, and maintaining an average particle size of 3.8 nm. This combined the advantages of high order and small size, thus exhibiting the best ORR catalytic activity.

[0052] (3) MOR catalytic performance test The MOR test was performed on the Pt5Sm / C catalysts prepared at three different heat treatment temperatures according to the method described in Verification Example 2. The results are as follows: Figure 12 As shown, the MOR current densities corresponding to the Pt5Sm / C catalysts obtained by heat treatment at 750℃, 850℃, and 950℃ are 9.87 mA / cm², respectively. 2 11.30 mA / cm2 and 11.12 mA / cm 2 Among them, the Pt5Sm / C catalyst obtained by heat treatment at 850℃ has the highest MOR current density and the best MOR catalytic activity.

[0053] The activity variation pattern is consistent with that of ORR: the 750℃ sample had the lowest MOR activity because the Pt-Sm alloy effect could not be fully utilized due to insufficient order; although the 950℃ sample had high order, the active area was greatly reduced due to severe particle sintering, and the MOR activity was also lower than that of the 850℃ sample. The 850℃ sample had the advantages of both high order and small size, providing sufficient highly active alloy catalytic sites, and thus had the best MOR activity.

[0054] Verification Example 4 To verify the stability of the Pt5Sm / C catalyst obtained in this invention in ORR, accelerated aging comparison tests were conducted on Pt5Sm / C and commercial Pt / C catalysts according to the following method.

[0055] Working electrodes were prepared using the Pt5Sm / C catalyst obtained in Example 1 and a commercial Pt / C catalyst, respectively, according to the method in Verification Example 1. Accelerated aging tests were conducted in 0.1 mol / L HClO4 solution under the following aging conditions: 30,000 cyclic scans within a potential range of 0.60–0.95 V. ORR polarization curves and cyclic voltammetry curves were recorded before and after aging to compare changes in mass activity and electrochemical surface area.

[0056] Figure 13A and Figure 13B ORR polarization curves and cyclic voltammetry curves before and after accelerated aging tests are shown. Figure 13A It can be seen that before the potential cycling test, the mass activity of Pt5Sm / C at 0.9V was 410 mA / mgPt, approximately 1.7 times that of commercial Pt / C (240 mA / mgPt). From Figure 13B It can be seen that the electrochemical surface area of ​​Pt5Sm / C is 63.3 m². 2 / gPt. In addition, compared with commercial Pt / C, the surface oxidation potential of Pt5Sm / C shows a positive shift, indicating that the oxidation resistance of Pt on its surface is enhanced.

[0057] After 30,000 potential cycles, the electrochemical specific surface area of ​​commercial Pt / C decreased by 30.9%, and its mass activity decreased by 35.1%; while the corresponding losses for Pt5Sm / C were only 11.5% and 10.3%, respectively, and its mass activity remained as high as 368 mA / mgPt, approximately 2.4 times that of aged commercial Pt / C (156 mA / mgPt). These results fully demonstrate that the Pt5Sm / C catalyst exhibits superior ORR catalytic stability.

[0058] Verification Example 5 To verify the catalytic activity and anti-poisoning stability of the Pt5Sm / C catalyst obtained in this invention in the methanol oxidation reaction, the Pt5Sm / C catalyst was compared with commercial Pt / C and commercial PtRu / C catalysts according to the following method: Working electrodes of the Pt5Sm / C catalyst obtained in Example 1, the commercial Pt / C catalyst, and the commercial PtRu / C catalyst were prepared according to the method in Verification Example 2, and cyclic voltammetry curves were tested. Furthermore, chronoamperometric tests were performed at a constant potential, and the current density change curve over time was recorded.

[0059] The results are as follows Figure 14A and Figure 14B As shown. By Figure 14A The cyclic voltammetry results show that the MOR forward scan current densities for Pt5Sm / C, ​​commercial Pt / C, and commercial PtRu / C catalysts are 11.30 mA / cm². 2 7.83 mA / cm 2 and 10.70 mA / cm 2 Among them, the MOR catalytic activity of the Pt5Sm / C catalyst is significantly better than that of commercial Pt / C and commercial PtRu / C catalysts.

[0060] Figure 14B The displayed chronoampere test results show that the Pt5Sm / C catalyst consistently exhibits superior performance throughout the entire test range, maintaining a current density retention of 63%, far exceeding that of commercial Pt / C (39%) and commercial PtRu / C catalysts (36%). Even after the chronoampere test, the current density of the Pt5Sm / C catalyst remained as high as 4.4 mA / cm². 2 These are commercial Pt / C (2.0 mA / cm²). 2 ) and commercial PtRu / C catalyst (2.5 mA / cm) 2 The 176% and 220% of the values ​​of the Pt5Sm / C catalysts confirm that the Pt5Sm / C catalyst has stronger MOR catalytic stability. This is attributed to the regulation of the electronic structure of Pt after the introduction of Sm, which weakens the adsorption strength of reaction intermediates such as CO on the Pt surface.

[0061] Verification Example 6 To verify the practical application performance of the Pt5Sm / C catalyst obtained in this invention in hydrogen / air and hydrogen / oxygen fuel cells, fuel cell performance was tested according to the following method.

[0062] The Pt5Sm / C obtained in Example 1 and commercial Pt / C were used as cathode catalysts and coated on the surface of the gas diffusion layer to assemble a single cell. The voltage-current density polarization curve and power density curve were recorded.

[0063] Figure 15A and Figure 15BTest results for hydrogen / air and hydrogen / oxygen fuel cells are shown separately. Figure 15A It can be seen that, in the hydrogen / air fuel cell test, the maximum power density of the Pt5Sm / C catalyst reached 853 mW / cm³. 2 It is significantly superior to commercial Pt / C catalysts (777mW / cm²). 2 ) and the Pt5La / C catalyst reported in the literature (794mW / cm 2 ).Depend on Figure 15B As can be seen, in the hydrogen / oxygen fuel cell test, the Pt5Sm / C catalyst achieved a maximum power density of 2450 mW / cm³. 2 It is also higher than that of commercial Pt / C catalysts (2296mW / cm). 2 This fully demonstrates the promising application prospects of the catalyst of this invention in fuel cells.

[0064] Verification Example 7 To verify the anodic catalytic performance and precious metal utilization rate of the Pt5Sm / C catalyst obtained in this invention in a direct methanol fuel cell, the performance of the direct methanol fuel cell was tested according to the following method.

[0065] The Pt5Sm / C obtained in Example 1, commercial Pt / C, and commercial PtRu / C were used as anode catalysts to assemble single cells, and voltage-current density polarization curves and power density curves were recorded.

[0066] The results are as follows Figure 16 As shown, the maximum power density of the Pt5Sm / C catalyst is 52 mW / cm³. 2 It is significantly superior to commercial Pt / C (28mW / cm²). 2 ), and compared with commercial PtRu / C (53mW / cm) 2 The results are close. After normalization by precious metal mass, the maximum power per unit mass of the Pt5Sm / C catalyst reaches 104.0 mW / mg, which is significantly higher than that of commercial Pt / C (46.7 mW / mg) and commercial PtRu / C (88.3 mW / mg). This indicates that Pt5Sm / C can maintain battery performance comparable to that of commercial PtRu / C while reducing the amount of precious metals used, achieving higher precious metal utilization and demonstrating good potential to replace traditional PtRu / C catalysts.

[0067] Verification Example 8 To verify the durability of the Pt5Sm / C catalyst obtained in this invention under actual fuel cell operating conditions, accelerated aging tests were conducted according to the following method.

[0068] Using the Pt5Sm / C obtained in Example 1 and commercially available Pt / C as cathode catalysts, hydrogen / air fuel cells were assembled according to the method in Validation Example 6. Accelerated aging tests were performed by cyclic scanning for 30,000 cycles within a potential range of 0.60–0.95 V, and the voltage-current density polarization curves and power density curves before and after aging were recorded. The aged cells were disassembled, and the cathode catalyst layer was subjected to TEM characterization to observe changes in catalyst morphology and particle size.

[0069] Figure 17 The performance curves of the fuel cell before and after accelerated aging testing are shown. Figure 17 It can be seen that after accelerated aging testing, the performance of commercial Pt / C batteries is severely degraded, down to 0.8 A / cm. 2 The voltage drop at the current density is as high as 276 mV. In contrast, Pt5Sm / C experiences a voltage drop of only 56 mV at the same current density, which is only about 1 / 5 of that of commercial Pt / C. The maximum power density of the Pt5Sm / C catalyst remains at 608 mW / cm³. 2 The ratio of Pt / C after aging is approximately 327 mW / cm². 2 1.9 times that of ).

[0070] Figure 18A and Figure 18B Transmission electron microscopy (TEM) images and particle size distribution diagrams of the Pt5Sm / C catalyst after accelerated aging tests are presented. Figures 18A-18B It is evident that after accelerated aging tests, although the average particle size of the Pt5Sm / C catalyst increased from 3.8±1.0 nm to 6.7±1.7 nm, the nanoparticles were still relatively uniformly dispersed on the carbon support surface without significant global aggregation or detachment from the support surface. The intermetallic compound structure was well preserved, which is the structural basis for its excellent battery durability.

[0071] In summary, this invention successfully prepared a series of high-platinum-load, small-size platinum-lanthanide (Pt5RE, RE = La, Ce, Sm) intermetallic compound catalysts using an amino-assisted synthesis strategy with p-phenylenediamine-modified carbon black as a support, followed by high-temperature annealing and acid washing. This method is highly versatile and can be extended to various lanthanide elements; the prepared catalysts possess the synergistic advantages of small size (<4 nm) and high platinum loading (>20 wt%); among them, Pt5Sm / C achieved a mass activity of 410 mA / mgPt in ORR and a MOR current density of 11.30 mA / cm². 2 Both significantly outperform commercial Pt / C; after 30,000 accelerated aging cycles, the mass activity loss is only 10.3%, and the fuel cell voltage drop is only about 1 / 5 of that of commercial Pt / C; the power density of the hydrogen / air fuel cell reaches 853 mW / cm³. 2The direct methanol fuel cell achieves a power output of 104.0 mW / mg. This invention provides a general and efficient technical solution for the design and controllable preparation of high-performance platinum-lanthanide intermetallic compound catalysts.

[0072] Obviously, the embodiments described above are merely some embodiments of this application, not all embodiments, and do not limit the patent scope of this application. This application can be implemented in many different forms; on the contrary, the purpose of providing these embodiments is to make the disclosure of this application more thorough and comprehensive. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing specific embodiments, or make equivalent substitutions for some of the technical features. Any equivalent structures made using the content of this application's specification, directly or indirectly applied to other related technical fields, are similarly within the patent protection scope of this application.

Claims

1. A method for preparing a platinum-lanthanide intermetallic compound catalyst with high platinum loading, characterized in that, Includes the following steps: (1) Disperse carbon black in deionized water, add p-phenylenediamine and concentrated sulfuric acid, sonicate in a water bath and then heat in an oil bath to react, adding NaNO2 solution dropwise during the reaction. After the reaction is completed, after post-treatment, amino-modified carbon black is obtained. (2) Disperse the amino-modified carbon black obtained in step (1) in ethylene glycol solution, add chloroplatinic acid hydrate, sonicate in water bath and then heat in oil bath to react. After the reaction is completed, post-treatment is performed to obtain carbon-supported platinum. (3) Disperse the carbon-supported platinum obtained in step (2) in deionized water, add lanthanide metal chloride, heat and stir in an oil bath until dry, heat the resulting powder at 750~950℃ for 1~3 hours in a reducing atmosphere, treat the product in an acid solution, wash and dry it, and then heat treat it again in a reducing atmosphere to obtain the product.

2. The preparation method according to claim 1, characterized in that, The lanthanide chloride mentioned in step (3) is any one of samarium chloride hexahydrate, lanthanum chloride heptahydrate, or cerium chloride heptahydrate; the amount of lanthanide chloride added is calculated based on an atomic ratio of Pt to lanthanide metal of 4~6:

1.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of carbon black to p-phenylenediamine is 1:0.5~0.7, the concentration of the NaNO2 solution is 0.5~2.0 mg / mL, the temperature of the oil bath heating is 50~80℃, and the reaction time is 12~20 hours.

4. The preparation method according to claim 1, characterized in that, The volume fraction of the ethylene glycol solution in step (2) is 40%~80%, the amount of chloroplatinic acid added is calculated as 15~25wt% of the platinum loading in the carbon-supported platinum, the temperature of the oil bath heating is 120~160℃, and the reaction time is 4~8 hours.

5. The preparation method according to claim 1, characterized in that, The reducing atmosphere in step (3) is an argon-hydrogen mixed atmosphere containing 3%~10% H2; the heat treatment temperature is 850℃ and the time is 1~3 hours; the acid solution is a 0.05~0.2mol / L perchloric acid solution, the treatment temperature is 40~80℃ and the treatment time is 4~8 hours; the second heat treatment temperature is 350~450℃ and the time is 0.5~2 hours.

6. The preparation method according to claim 2, characterized in that, The lanthanide chloride mentioned in step (3) is samarium chloride hexahydrate.

7. A platinum-lanthanide intermetallic compound catalyst with high platinum loading, characterized in that, The catalyst is prepared by any one of the preparation methods described in claims 1 to 6; the platinum-lanthanide intermetallic compound nanoparticles in the catalyst are uniformly dispersed on the surface of the carbon support, the average particle size is less than 4 nm, and the platinum loading is greater than 20 wt%.

8. The catalyst according to claim 7, characterized in that, The platinum-lanthanide intermetallic compound has a hexagonal crystal structure and the chemical formula Pt5RE, wherein RE is any one of La, Ce or Sm.

9. The use of the catalyst of claim 7 or 8 in the cathode of a proton exchange membrane fuel cell.

10. The use of the catalyst of claim 7 or 8 in the anode of a direct methanol fuel cell.

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