Method for controllably preparing platinum-based intermetallic compound catalyst with core-shell structure based on surface segregation and application
By atomically regulating the surface enrichment and thermal annealing process of bismuth elements in Pt-M alloy catalysts, the directed segregation of Bi elements is achieved, and the core-shell structure is constructed, which solves the problems of attenuation of existing catalysts in distribution characteristics, durability and active area, and achieves efficient methanol electrooxidation and significant power density improvement.
Patent Information
- Application Number
- CN202510219745.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-26
- Publication Date
- 2025-05-23
AI Technical Summary
The existing Pt-M alloy catalysts have random distribution characteristics that lead to disorderly arrangement of active sites, making it difficult to achieve directional regulation of catalytic selectivity. At the same time, transition metal components are prone to dissolution and loss under acidic conditions, affecting the durability of the battery, and the nanoparticles surface energy is too high and prone to sintering and agglomeration, resulting in continuous attenuation of the active area.
The surface enrichment of bismuth elements is regulated by atomic precision, and the thermodynamic orientation segregation of Bi elements on the surface of intermetallic compounds is realized in the thermal annealing process, and a sub-nanoscale Bi-enriched shell is constructed to form a Pt-based catalyst with a core-shell structure.
The ultra-high intrinsic activity and anti-CO toxicity characteristics of the catalyst were achieved, the mass activity was increased by 16.2 times, and the peak power density reached 294.21mW/cm2, which significantly enhanced the kinetic properties of methanol electrooxidation and anti-polarization capabilities.
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Abstract
Description
Technical Field
[0001] The invention belongs to the field of nano-electrocatalytic material preparation, and specifically relates to a method for controllably preparing a core-shell structured platinum-based intermetallic compound catalyst based on surface segregation and its application. Background Art
[0002] Polymer electrolyte membrane fuel cells (PEMFCs) have been established as the core technology direction of mobile power and distributed energy systems due to their clean and efficient energy conversion characteristics. Although the currently commercialized Pt / C catalysts have excellent initial catalytic activity, they face three technical bottlenecks: first, the high cost of precious metal platinum seriously restricts large-scale commercial applications; second, the catalyst is prone to platinum dissolution and carbon carrier corrosion under high-potential cycle conditions; third, the anode side is easily poisoned by CO intermediates when catalyzing the electro-oxidation of small molecules, resulting in a sharp decline in catalytic activity.
[0003] In order to reduce the platinum loading and improve the catalytic activity, the academic community has proposed a solution to construct a Pt-M (M = Fe, Co, Ni and other transition metals) alloy catalyst. This type of catalyst can effectively regulate the surface electronic structure by introducing strain effect and ligand effect, and exhibits a specific activity better than pure platinum under ideal conditions. However, the existing Pt-M alloy system has significant defects: first, the metal atoms are randomly distributed in the alloy phase, resulting in disordered arrangement of active sites, making it difficult to achieve directional regulation of catalytic selectivity; second, the transition metal components are prone to dissolution and loss under acidic conditions, which not only causes the catalyst structure to collapse, but the dissolved metal ions will also poison the proton exchange membrane, seriously affecting the battery durability; in addition, in the actual working environment of the membrane electrode, nanoparticles are prone to sintering and agglomeration due to their high surface energy, resulting in continuous attenuation of the active area. In recent years, intermetallic compound nanocrystals with core-shell structures have received widespread attention due to their unique electronic structure adjustability. Theoretical studies have shown that by precisely designing the lattice matching and component gradient distribution at the core-shell interface, the dual effects of lattice strain and electronic ligands can be synergistically enhanced, thereby optimizing the adsorption / desorption kinetics of electrocatalytic reaction intermediates. Compared with traditional alloy catalysts, this type of structure can improve the utilization of precious metals to the atomic level. However, the core-shell structure catalysts reported so far have the following problems: first, the ultra-thin (<0.3nm) shell has a limited modulation range on the surface electronic state, resulting in the unclear synergistic mechanism of strain and ligand effects; second, it is difficult to achieve precise control of the shell. At present, there is a lack of effective means to construct a gradient component shell on a long-range ordered intermetallic compound matrix, which hinders the development of this new concept of high-efficiency catalysts. Therefore, the development of intermetallic compound core-shell catalysts with precise atomic arrangement and controllable shell structure has become a key technical challenge to break through the performance bottleneck of fuel cell electrocatalytic materials. Summary of the invention
[0004] In view of the shortcomings of the prior art, the present invention aims to provide a method and application of controllable preparation of core-shell structured platinum-based intermetallic compound catalysts based on surface segregation; the present invention controls the surface enrichment of bismuth elements with atomic-level precision, realizes the thermodynamically oriented segregation of Bi elements on the surface interface of intermetallic compounds under a simple thermal annealing process, and innovatively controls the surface enrichment of bismuth elements on the surface of intermetallic compounds in the long-range L1 0 The construction of a sub-nanoscale Bi-enriched shell on the PtMn ordered intermetallic compound has opened up a new way to improve the catalytic performance of core-shell nanocrystals. The catalyst exhibits the dual advantages of ultra-high intrinsic activity and resistance to CO poisoning in the anode reaction of direct methanol fuel cells.
[0005] To achieve the above object, the present invention provides the following solutions:
[0006] The present invention provides a method for controllably preparing a core-shell structured platinum-based intermetallic compound catalyst based on surface segregation, comprising the following steps:
[0007] (1) mixing and dispersing a manganese salt, a bismuth salt, a platinum-containing salt and a carbon material in a solvent, adjusting the pH to obtain a mixed solution, and drying the solution;
[0008] (2) heat-treating the precursor after the drying treatment in step (1) under a reducing atmosphere to obtain a core-shell structured platinum-based intermetallic compound catalyst.
[0009] More preferably, the solvent in step (1) is water.
[0010] Further preferably, the drying treatment in step (1) is freeze-drying.
[0011] Further preferably, the pH adjustment in step (1) is to adjust the pH to 0.5-2. 3 , HCl or one or more thereof to adjust the pH value.
[0012] Further preferably, the platinum-containing salt in step (1) is chloroplatinic acid, the manganese salt is hydrated manganese chloride, and the bismuth salt is hydrated bismuth nitrate;
[0013] Further preferably, the carbon material in step (1) is Ketjen black EC-300J or EC-600JD.
[0014] Further preferably, the mass ratio of the platinum salt, manganese salt and bismuth salt in step (1) is 15-30:5-10:0.5-5.
[0015] Further preferably, the mass ratio of the carbon material to the platinum-containing salt in step (1) is 40-60:15-30.
[0016] Further preferably, in the mixed solution described in step (1), the concentration of chloroplatinic acid is 5-20 mg / mL.
[0017] Further preferably, the temperature of the heat treatment in step (2) is 500-1000° C., and the time of the heat treatment is 1-6 h.
[0018] Further preferably, the reducing atmosphere in step (2) is a hydrogen-argon mixture, a hydrogen-helium mixture or a hydrogen-nitrogen mixture.
[0019] Preferably, the volume proportion of hydrogen in the hydrogen-argon mixed gas is 5-15%.
[0020] The present invention provides a core-shell structured platinum-based intermetallic compound catalyst (Bi-PtMn, wherein Pt represents platinum, Mn represents manganese, and Bi represents bismuth) prepared by the above method, wherein the carbon-supported PtMn intermetallic compound is the core and the bismuth atoms are enriched on the surface as the shell.
[0021] Further preferably, in the core-shell structured platinum-based intermetallic compound catalyst, the mass fraction of Pt is 7%-20%, the mass fraction of Bi is 0.5%-10%; and the mass fraction of Mn is 2%-3%.
[0022] Preferably, in the core-shell structured platinum-based intermetallic compound catalyst, the mass fraction of Pt is 10%, the mass fraction of Bi is 0.5-3%, and the mass fraction of Mn is 2.6%.
[0023] More preferably, in the core-shell structured platinum-based intermetallic compound catalyst, the mass fraction of Pt is 10%, the mass fraction of Bi is 1.25%, and the mass fraction of Mn is 2.6%.
[0024] The present invention provides the use of the core-shell structured platinum-based intermetallic compound catalyst in methanol electro-oxidation or direct methanol fuel cells.
[0025] Further preferably, the core-shell structured platinum-based intermetallic compound catalyst is used as a catalyst for a direct methanol fuel cell.
[0026] The present invention disperses soluble precursors of precious metal platinum, non-precious metal bismuth and manganese on a carbon carrier by an impregnation method, freeze-dries, and thermally anneals in an environment containing a reducing atmosphere to simultaneously achieve alloying and surface segregation of Bi in one step, thereby obtaining a Pt-based catalyst with a core-shell structure having a carbon-supported PtMn intermetallic compound as a core and a surface gradient enrichment of bismuth atoms as a shell.
[0027] The traditional synthesis method of Pt-Bi alloy catalyst has the problem of difficulty in controlling the surface enrichment of Bi, and its random distribution characteristics lead to insufficient exposure of active sites. At the same time, the existing surface modification technology (such as underpotential deposition method) is difficult to meet the needs of large-scale production due to the complexity of the process and poor batch repeatability.
[0028] The present invention innovatively introduces the Mn element to construct a Pt-Mn-Bi ternary system, and simultaneously achieves through a thermal annealing process: ① ordered construction of an inner core Pt-Mn intermetallic compound; ② precise control of the surface Bi atomic layer, and successfully develops a Bi-surface-modified PtMn intermetallic compound core-shell catalyst that can be scalable (gram-scale preparation can be achieved).
[0029] Compared with the prior art, the present invention has the following beneficial effects:
[0030] The core-shell structure catalyst with bismuth surface modified and PtMn core prepared by the present invention exhibits extremely excellent methanol oxidation performance in both electrochemical and actual fuel cell tests, and can be used as a high-performance methanol oxidation catalyst in direct methanol fuel cells.
[0031] The bismuth-modified PtMn intermetallic compound core-shell catalyst prepared by the thermal annealing process was characterized by spherical aberration-corrected transmission electron microscopy to confirm that it has a PtMn ordered intermetallic compound core and a bismuth atom-enriched surface. Electrochemical tests showed that the methanol oxidation mass activity reached 61.81A / mgPt(1M CH 3 OH+1M KOH), which is 16.2 times higher than the traditional Pt / C catalyst. In the direct methanol fuel cell test, the anode catalyst loading was 0.5mg / cm 2 The peak power density reaches 294.21mW / cm 2 The catalyst is suitable for the anode catalyst layer of direct methanol fuel cells (DMFCs), and is particularly suitable for industrial applications in portable power sources and distributed energy supply systems. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Figure 1 This is the X-ray diffraction pattern of Bi-PtMn prepared in Example 1.
[0033] Figure 2 Bi prepared in Example 2 M -X-ray diffraction pattern of PtMn.
[0034] Figure 3 Bi prepared in Example 3 E -X-ray diffraction pattern of PtMn.
[0035] Figure 4 This is the X-ray diffraction pattern of PtMn prepared in Comparative Example 1.
[0036] Figure 5 This is a spherical aberration transmission electron microscope image of Bi-PtMn prepared in Example 1, and the arrow in the image indicates the EDS line scan area.
[0037] Figure 6 This is the spherical aberration transmission electron microscope (EDS) line scan image of Bi-PtMn prepared in Example 1.
[0038] Figure 7 This is the polarization curve of the methanol electro-oxidation test of Bi-PtMn prepared in Example 1.
[0039] Figure 8 Bi prepared in Example 2 M Polarization curve of methanol electrooxidation test of -PtMn.
[0040] Fig. 9 Bi prepared in Example 3 E Polarization curve of methanol electrooxidation test of -PtMn.
[0041] Fig.10 This is the polarization curve of the methanol electro-oxidation test of PtMn prepared in Comparative Example 1.
[0042] Fig.11 Polarization curves for methanol electrooxidation tests on commercial platinum-carbon.
[0043] Fig.12 Schematic diagram of polarization curves and power density of Bi-PtMn prepared in Example 1 and commercial platinum carbon in a direct methanol fuel cell.
[0044] Fig.13 This is the electrochemical in-situ attenuated total reflection-surface enhanced infrared absorption spectrum of Bi-PtMn prepared in Example 1. DETAILED DESCRIPTION
[0045] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.
[0046] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.
[0047] Unless otherwise indicated, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described in the present invention may also be used in the implementation or testing of the present invention. All documents mentioned in the present invention are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.
[0048] Without departing from the scope or spirit of the present invention, various modifications and variations may be made to the specific embodiments of the present invention description, which will be apparent to those skilled in the art. Other embodiments obtained from the present invention description will be apparent to those skilled in the art. The present invention description and examples are merely exemplary. As used herein, "comprising", "including", "having", "containing", etc. are all open-ended terms, i.e., meaning including but not limited to.
[0049] Example 1
[0050] 50 mg of commercial carbon powder (Ketjen black EC-300J) was added to a 100 mL beaker, followed by 970 μL of 20 mg / mL H 2 PtCl 6 6H 2 O aqueous solution, 100 μL 20 mg / mL Bi(NO 3 ) 3 ·5H 2 O aqueous solution, 340 μL 20 mg / mL MnCl 2 ·4H 2 O aqueous solution, add 500 μL of deionized water, and use dilute HNO 3 The pH value of the solution was adjusted to 1 (1 mol / L), and then ultrasonic dispersion was used for 2 h, followed by freeze drying for 12 h. The resulting precursor was added to a tube furnace and heated under H 2 / Ar(H 2 The reaction mixture was heated to 830°C at a heating rate of 5°C / min in an atmosphere with a volume fraction of 8%, and calcined for 3 h. The mixture was then cooled to room temperature at a cooling rate of 3°C / min to obtain a carbon-supported moderate-density bismuth surface-modified PtMn intermetallic compound core-shell catalyst (Bi-PtMn).
[0051] Example 2
[0052] 50 mg of commercial carbon powder (Ketjen black EC-300J) was added to a 100 mL beaker, followed by 970 μL of 20 mg / mL H 2 PtCl 66H 2 O aqueous solution, 45 μL 20 mg / mL Bi(NO 3 ) 3 ·5H 2 O aqueous solution and 340 μL 20 mg / mL MnCl 2 ·4H 2 O aqueous solution, add 500 μL of deionized water, and use dilute HNO 3 The pH value of the solution was adjusted to 1 (1 mol / L), and then ultrasonic dispersion was used for 2 h, followed by freeze drying for 12 h. The resulting precursor was added to a tube furnace and heated under H 2 / Ar(H 2 The carbon-supported low-density bismuth surface-modified PtMn intermetallic compound core-shell catalyst (Bi M -PtMn).
[0053] Example 3
[0054] 50 mg of commercial carbon powder (Ketjen black EC-300J) was added to a 100 mL beaker, followed by 970 μL of 20 mg / mL H 2 PtCl 6 6H 2 O aqueous solution, 275 μL 20 mg / mL Bi(NO 3 ) 3 ·5H 2 O aqueous solution and 340 μL 20 mg / mL MnCl 2 ·4H 2 O aqueous solution, add 500 μL of deionized water, and use dilute HNO 3 The pH value of the solution was adjusted to 1 (1 mol / L), and then ultrasonic dispersion was used for 2 h, followed by freeze drying for 12 h. The resulting precursor was added to a tube furnace and heated under H 2 / Ar(H 2 The carbon-supported high-density bismuth surface-modified PtMn intermetallic compound core-shell catalyst (Bi E -PtMn).
[0055] Comparative Example 1
[0056] 50 mg of commercial carbon powder (Ketjen black EC-300J) was added to a 100 mL beaker, followed by 970 μL of 20 mg / mL H2 PtCl 6 6H 2 O aqueous solution and 340 μL 20 mg / mL MnCl 2 ·4H 2 O aqueous solution, add 500 μL of deionized water, then use ultrasonic dispersion for 2 h, and then freeze-dry for 12 h. The resulting precursor is added to a tube furnace and heated under H 2 / Ar(H 2 The volume proportion is 8%), the temperature was increased to 830°C in an atmosphere at a heating rate of 5°C / min and calcined for 3 hours, and then cooled to room temperature at a cooling rate of 3°C / min to obtain a carbon-supported PtMn intermetallic compound catalyst (PtMn).
[0057] Data analysis
[0058] (1) Comparative Examples 1-3 (corresponding to Figure 1-3 ) and Comparative Example 1 ( Figure 4 ), the characteristic peaks of the samples in Examples 1-3 are consistent with the peaks of the PtMn intermetallic compound in Comparative Example 1, which confirms that the preparation method of the present invention can induce Bi atoms to form a surface covering layer through surface segregation within different Bi / Pt molar ratios through a thermal annealing process, and Bi atoms will not penetrate into the PtMn lattice to cause lattice distortion of the core PtMn intermetallic compound.
[0059] Spherical aberration corrected transmission electron microscope image ( Figure 5 ) further confirmed the core-shell structure of the catalyst. The bright ones are Pt or Bi elements, and the darker ones are Mn elements. Further combined with EDS line scanning ( Figure 6 ) confirmed that Bi atoms are enriched in the outermost layer (shell thickness 0.6nm, corresponding to 1-2 atomic layers), while Mn elements are enriched in the inner core region.
[0060] (2) Weigh 2 mg of Bi-PtMn and Bi prepared in Example 1-3. M -PtMn、Bi E -PtMn catalyst material, the PtMn catalyst material prepared in Comparative Example 1 and 20wt.% commercial platinum carbon were dispersed in 20μL Nafion (5%) solution, 50μL deionized water and 950μL isopropanol mixed solution, ultrasonicated in an ice water bath for 1h, 4μL was taken with a pipette onto the surface of the glassy carbon electrode and dried, and the electrochemical cyclic voltammetry test method was used. 3 In OH solution, the scanning rate was 50mV / s to test the electro-oxidation performance of methanol, and the polarization curve was obtained as follows Figure 7-Figure 11 , among which Bi-PtMn, Bi M -PtMn、Bi E-The mass activities of PtMn, PtMn and Pt / C are 61.81Amg -1 Pt 、23.68Amg -1 Pt 、26.73A mg -1 Pt 、4.67Amg -1 Pt and 3.81A mg -1 Pt It can be seen that the methanol electro-oxidation performance of the catalyst is greatly improved after Bi surface segregation, and the mass activity far exceeds that of PtMn intermetallic compounds and commercial platinum-carbon catalysts. Among them, the mass activity of PtMn intermetallic compounds (Bi-PtMn) modified with moderate density bismuth surface reaches 16.2 times that of Pt / C, showing extremely excellent activity.
[0061] (3) The Bi-PtMn catalyst prepared in Example 1 and the commercial platinum-carbon catalyst (Pt / C) were respectively heated at 0.5 mg / cm 2 The loading amount was sprayed onto the anode catalyst layer of the direct methanol fuel cell, and 6M KOH+3M CH 3 OH mixed solution, pure oxygen was introduced into the cathode side, and polarization curve and power density tests were carried out at 80°C. Fig.12 As shown in Figure 2, the peak power density of the Bi-PtMn catalyst reached 294.21 mW / cm 2 , compared with commercial platinum-carbon catalyst (92.97mW / cm 2 ) increased by 216.3%, indicating that it has significantly enhanced methanol electro-oxidation kinetics and anti-polarization ability.
[0062] (4) The Bi-PtMn catalyst prepared in Example 1 was used as the working electrode to carry out attenuated total reflection-surface enhanced infrared absorption spectroscopy measurement of the methanol electrooxidation process. The results are as follows: Fig.13 As shown, the scanning potential range is 0-1.2 V vs RHE, and no linear adsorption of carbon monoxide intermediate CO on the surface is observed in the entire potential range. L signal, indicating that its methanol electrooxidation process experienced a CO-free pathway.
[0063] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should fall within the protection scope determined by the claims of the present invention.
Claims
1. A method for controllably preparing a core-shell structured platinum-based intermetallic compound catalyst based on surface segregation, characterized in that: The following steps are involved: (1) mixing and dispersing a manganese salt, a bismuth salt, a platinum-containing salt and a carbon material in a solvent, adjusting the pH to obtain a mixed solution, and drying the solution; (2) heat-treating the precursor after the drying treatment in step (1) under a reducing atmosphere to obtain a core-shell structured platinum-based intermetallic compound catalyst.
2. The method for preparing a core-shell structured platinum-based intermetallic compound catalyst based on surface segregation controllable according to claim 1, characterized in that: The solvent described in step (1) is water.
3. The method for preparing a core-shell structured platinum-based intermetallic compound catalyst based on surface segregation controllable according to claim 1, characterized in that: The pH adjustment in step (1) is to adjust the pH to 0.5-2.
4. The method for preparing a core-shell structured platinum-based intermetallic compound catalyst based on surface segregation controllable according to claim 1, characterized in that: The platinum-containing salt described in step (1) is chloroplatinic acid, the manganese salt is hydrated manganese chloride, and the bismuth salt is hydrated bismuth nitrate; The carbon material described in step (1) is Ketjen black EC-300J or EC-600JD.
5. The method for preparing a core-shell structured platinum-based intermetallic compound catalyst based on surface segregation controllable according to claim 1, characterized in that: The mass ratio of the platinum salt, manganese salt and bismuth salt in step (1) is 15-30:5-10:0.5-5; In the mixed solution described in step (1), the concentration of chloroplatinic acid is 5-20 mg / mL.
6. The method for preparing a core-shell structured platinum-based intermetallic compound catalyst based on surface segregation controllable according to claim 1, characterized in that: The heat treatment temperature in step (2) is 500-1000° C., and the heat treatment time is 1-6 hours.
7. The method for controllably preparing a core-shell structured platinum-based intermetallic compound catalyst based on surface segregation according to claim 1, characterized in that: The reducing atmosphere described in step (2) is a hydrogen-argon mixture, a hydrogen-helium mixture or a hydrogen-nitrogen mixture.
8. A core-shell structured platinum-based intermetallic compound catalyst prepared by the method according to any one of claims 1 to 7, characterized in that: The carbon-supported PtMn intermetallic compound is the core, and the bismuth atoms enriched on the surface are the shell.
9. Use of the core-shell structured platinum-based intermetallic compound catalyst according to claim 8 in methanol electro-oxidation or direct methanol fuel cells.
10. The use according to claim 9, characterized in that: The core-shell structured platinum-based intermetallic compound catalyst is used as a catalyst for a direct methanol fuel cell.