Cobalt-platinum intermetallic compounds confined on nitrogen-doped carbon scaffolds, methods of making and applications thereof
Patent Information
- Application Number
- CN202610448469.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-04-07
- Publication Date
- 2026-06-26
AI Technical Summary
Cobalt-platinum alloy catalysts are prone to agglomeration and dissolution, resulting in low activity stability in the ethanol oxidation reaction (EOR).
Cobalt-platinum intermetallic compounds confined to a nitrogen-doped carbon framework were prepared by adding chloroplatinic acid hexahydrate and 2-methylimidazole to a cobalt salt solution to form Pt/ZIF-67, which was then mixed with melamine and calcined at high temperature to form CoPt3-NC.
This improved the structural stability of the catalyst and the stability of EOR, reduced the amount of precious metal platinum used, enhanced catalytic activity and reaction kinetics, and lowered costs.
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Figure CN122291553A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to cobalt-platinum intermetallic compounds confined to a nitrogen-doped carbon framework, their preparation methods, and applications, belonging to the field of ethanol electrocatalytic oxidation reactions. Background Technology
[0002] Ethanol is a recognized green chemical and energy carrier, and direct ethanol fuel cells have attracted much attention due to their high theoretical energy density, low fuel toxicity, and renewability. Direct ethanol fuel cells benefit from the wide availability of fuel sources and high energy density (8 kWh / kg⁻¹). -1 Ethanol fuel cells (EFCs) are considered a promising sustainable energy conversion technology due to their safe storage and transportation, environmental friendliness, and ease of use. However, the complexity and slow kinetics of the anodic ethanol oxidation (EOR) reaction severely restrict the commercialization of direct ethanol fuel cells. Platinum-based materials are currently recognized as the most active catalysts for EOR. However, the scarcity and high cost of platinum significantly limit their large-scale commercial application.
[0003] To reduce platinum usage and improve its catalytic efficiency, researchers have developed various strategies, one of the most effective being alloying platinum with 3d transition metals (such as iron, cobalt, and nickel) to form platinum-based bimetallic nanomaterials. This alloying strategy not only reduces the amount of platinum atoms used, but more importantly, it modulates the electronic structure of platinum through ligand and strain effects, optimizing the adsorption energy of key reaction intermediates, thereby significantly improving intrinsic activity and stability. Simultaneously, cobalt sites can adsorb and activate water molecules at lower potentials to generate oxygen-containing species (OH-). ads Cobalt-platinum alloys (CPAs) promote the oxidative removal of CO, a poisoned species, from adjacent platinum sites, thus achieving bifunctional synergistic catalysis. Therefore, CPAs stand out among many platinum-based catalysts due to their excellent activity and durability. However, CPAs often suffer from agglomeration and dissolution, leading to low catalytic activity. Researchers have found that loading CPAs onto nitrogen-doped carbon supports can effectively limit the particle size of the alloy and reduce agglomeration. However, disordered solid solution alloys are far less stable than intermetallic compounds. Therefore, developing a cobalt-platinum intermetallic compound catalyst that is less prone to agglomeration is of great significance for EOR (Extraction-Oriented Reduction). Summary of the Invention
[0004] The purpose of this invention is to solve the problem that cobalt-platinum alloy catalysts are prone to agglomeration and dissolution, resulting in low activity and stability in EOR. This invention provides a method for preparing cobalt-platinum intermetallic compounds confined to a nitrogen-doped carbon framework, which exhibit good catalytic performance in EOR.
[0005] The technical solution adopted by this invention to solve its technical problem is: a method for preparing a cobalt-platinum intermetallic compound confined on a nitrogen-doped carbon framework, comprising the following steps:
[0006] (1) Add chloroplatinic acid hexahydrate to the cobalt salt solution and stir to obtain solution A; dissolve 2-methylimidazole in the solvent to form a homogeneous solution, which is solution B; add solution B to solution A and stir continuously, then precipitate; wash and dry to obtain purple powder, which is Pt / ZIF-67;
[0007] (2) Pt / ZIF-67 was mixed and ground with melamine and placed in a ceramic boat in a tube furnace. Under a protective atmosphere, the temperature was raised to 400 ℃-500 ℃ at a heating rate of 2-6 ℃ / min and held for 1-3 h. Then, the temperature was raised to 700 ℃-1000 ℃ at a heating rate of 1-4 ℃ / min and calcined at high temperature for 2-5 h to obtain black powder. CoPt3-NC was obtained after grinding and acid washing.
[0008] Furthermore, in step (1), the molar ratio of cobalt salt, chloroplatinic acid hexahydrate and 2-methylimidazole is 100:(2-4):(1-3); preferably, this ratio is 100:3:2.
[0009] The mass ratio of Pt / ZIF-67 to melamine is 10:(2-5), preferably 10:3.
[0010] Furthermore, in step (1), the cobalt salt is one of cobalt sulfate heptahydrate, cobalt nitrate hexahydrate, and cobalt chloride hexahydrate.
[0011] Furthermore, in step (1), the solvent of the cobalt salt solution is the same as the solvent used for imidazole, and is selected from at least one of methanol, ethanol, and water.
[0012] Furthermore, in step (1), the stirring time after mixing solution A and solution B is 10-24 h, and the sedimentation time is 5-24 h.
[0013] Furthermore, in step (2), the protective atmosphere used is one of N2, Ar, N2 containing 5-10 Vol% H2, or Ar containing 5-10 Vol% H2.
[0014] Furthermore, in step (2), the solution used for pickling is one of 1-2 M nitric acid, sulfuric acid, or perchloric acid solution.
[0015] The cobalt-platinum intermetallic compound supported on a nitrogen-doped carbon framework was prepared using the method described above.
[0016] Application of cobalt-platinum intermetallic compounds supported on nitrogen-doped carbon frameworks in the electrocatalytic oxidation of ethanol.
[0017] Specifically, the preparation method of the cobalt-platinum intermetallic compound catalyst confined on a nitrogen-doped carbon framework includes the following steps:
[0018] (1) Dissolve the cobalt salt in a solvent to form a homogeneous solution, and add chloroplatinic acid hexahydrate. Stir at room temperature for 10 minutes to obtain solution A;
[0019] (2) Dissolve 2-methylimidazole in a solvent to form a homogeneous solution, which is solution B;
[0020] (3) Add solution B to solution A and stir continuously, then precipitate; wash the precipitate with methanol and dry it, and the resulting purple powder is Pt / ZIF-67.
[0021] (4) Pt / ZIF-67 and melamine were mixed and ground and placed in a ceramic boat in a tube furnace. Under a protective atmosphere, the temperature was raised to a suitable temperature at a rate of 3 °C / min and held for 2 h. Then the temperature was raised at a rate of 2 °C / min and the temperature was continued to rise. After high-temperature calcination, black powder was obtained. CoPt3-NC was obtained after grinding and acid washing.
[0022] In step (2), the solution used for pickling is one of 1-2 M nitric acid, sulfuric acid, or perchloric acid solution, preferably 1 M nitric acid.
[0023] In step (1), the cobalt salt used is one of cobalt sulfate heptahydrate, cobalt nitrate hexahydrate, and cobalt chloride hexahydrate, preferably cobalt nitrate hexahydrate.
[0024] In step (2), the heat preservation temperature is 400-500 ℃, the calcination temperature is 700-1000 ℃, and the calcination time is 2-5 h. Preferably, the heat preservation temperature is 500 ℃, the calcination temperature is 900 ℃, and the calcination time is 2 h.
[0025] In step (1), the solvent used is one of methanol, ethanol, or water, preferably methanol.
[0026] In step (2), the atmosphere used is one of N2, Ar, N2 containing 5-10 vol% H2, or Ar containing 5-10 vol% H2, preferably Ar containing 10 vol% H2.
[0027] In step (1), the stirring time is 10-24 h, preferably 12 h, and the sedimentation time is 5-24 h, preferably 12 h.
[0028] The beneficial effects of this invention are as follows: This invention provides a method for preparing a cobalt-platinum intermetallic compound (CoPt3) confined on a dodecahedral nitrogen-doped carbon (NC) framework. Platinum salts are added during the synthesis of ZIF-67, encapsulating it within the dodecahedrons of ZIF-67 to obtain Pt / ZIF-67, which is then annealed at high temperature in a mixed gas atmosphere to obtain CoPt3-NC. The cobalt-platinum intermetallic compound prepared by this invention has a more stable structure and better EOR stability than disordered cobalt-platinum alloys. Furthermore, electron microscopy reveals that the CoPt3 particles are uniformly dispersed, with a size of approximately 12 nm, due to confinement on the nitrogen-doped carbon framework. ICP-OES results show that the platinum content in the sample is 3.44%. Both the electrochemical active area and EOR catalytic activity are superior to commercial platinum-carbon catalysts with a platinum content of 20%. Furthermore, compared to commercial Pt / C, CoPt3-NC exhibits a 57 mV lower onset potential, an 8.69 Ω lower charge transfer resistance, a 1.23-fold higher oxidation peak current density, and a 13.1% lower Tafel slope. The preparation method described in this invention reduces the use of the precious metal platinum by exposing more active sites, thereby lowering the cost of the EOR catalyst and facilitating the commercialization of direct ethanol fuel cells.
[0029] Compared with existing technologies, the solvents and washing solutions used in this invention do not involve toxic and difficult-to-remove reaction reagents, are green and environmentally friendly, are simple to operate and have low preparation costs, and can be extended to the preparation of other intermetallic compounds. Attached Figure Description
[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments.
[0031] Figure 1 This is a schematic diagram of the synthesis of CoPt3-NC.
[0032] Figure 2 This is a SEM image of CoPt3-NC.
[0033] Figure 3 It shows HAADF-STEM and elemental distribution diagrams.
[0034] Figure 4 These are TEM images and particle size distribution diagrams of CoPt3-NC.
[0035] Figure 5 This is the XRD pattern of CoPt3-NC.
[0036] Figure 6 This is the N2 adsorption-desorption isotherm of CoPt3-NC.
[0037] Figure 7 These are the LSV curves of EOR for CoPt3-NC and Pt / C under acidic conditions.
[0038] Figure 8 It is the Tafel slope of EOR for CoPt3-NC and Pt / C under acidic conditions.
[0039] Figure 9 These are the EIS curves of EOR for CoPt3-NC and Pt / C under acidic conditions. Detailed Implementation
[0040] Example 1:
[0041] (1) Dissolve 291 mg of cobalt nitrate hexahydrate in 25 ml of methanol to form a homogeneous solution, and add 15.5 mg of chloroplatinic acid hexahydrate. Stir at room temperature for 10 minutes to obtain solution A.
[0042] (2) Dissolve 164.2 mg of 2-methylimidazole in 25 ml of methanol to form a homogeneous solution, which is solution B;
[0043] (3) Add solution B to solution A and stir continuously for 12 h, then precipitate for 12 h; wash the precipitate three times with methanol and dry it in a drying oven at 60 ℃ for 12 h. The purple powder obtained is Pt / ZIF-67.
[0044] (4) 100 mg Pt / ZIF-67 and 30 mg melamine were mixed and ground and placed in a ceramic boat in a tube furnace. Under the protective atmosphere of Ar containing 10 Vol% H2, the temperature was raised to 500 ℃ at a heating rate of 3 ℃ / min and held for 2 h. Then the temperature was raised to 900 ℃ at a heating rate of 2 ℃ / min and calcined at high temperature for 2 h to obtain black powder. CoPt3-NC was obtained after grinding and acid washing.
[0045] Example 2:
[0046] (1) Dissolve 291 mg of cobalt nitrate hexahydrate in 25 ml of deionized water to form a homogeneous solution, and add 15.5 mg of chloroplatinic acid hexahydrate. Stir at room temperature for 10 minutes to obtain solution A.
[0047] (2) Dissolve 164.2 mg of 2-methylimidazole in 25 ml of deionized water to form a homogeneous solution, which is solution B;
[0048] (3) Add solution B to solution A and stir continuously for 12 h, then precipitate for 12 h; wash the precipitate three times with deionized water and dry it in a drying oven at 60 ℃ for 12 h. The purple powder obtained is Pt / ZIF-67.
[0049] (4) 100 mg Pt / ZIF-67 and 30 mg melamine were mixed and ground and placed in a ceramic boat in a tube furnace. Under the protective atmosphere of Ar containing 10 Vol% H2, the temperature was raised to 500 ℃ at a heating rate of 3 ℃ / min and held for 2 h. Then the temperature was raised to 900 ℃ at a heating rate of 2 ℃ / min and calcined at high temperature for 2 h to obtain black powder. CoPt3-NC was obtained after grinding and acid washing.
[0050] Example 3:
[0051] (1) Dissolve 2.91 g of cobalt nitrate hexahydrate in 100 ml of methanol to form a homogeneous solution, and add 155 mg of chloroplatinic acid hexahydrate. Stir at room temperature for 10 minutes to obtain solution A.
[0052] (2) Dissolve 1.64 g of 2-methylimidazole in 100 ml of methanol to form a homogeneous solution, which is solution B;
[0053] (3) Add solution B to solution A and stir continuously for 12 h, then precipitate for 12 h; wash the precipitate three times with methanol and dry it in a drying oven at 60 ℃ for 12 h. The purple powder obtained is Pt / ZIF-67.
[0054] (4) 100 mg Pt / ZIF-67 and 30 mg melamine were mixed and ground and placed in a ceramic boat in a tube furnace. Under the protective atmosphere of Ar containing 10 Vol% H2, the temperature was raised to 500 ℃ at a heating rate of 3 ℃ / min and held for 2 h. Then the temperature was raised to 900 ℃ at a heating rate of 2 ℃ / min and calcined at high temperature for 2 h to obtain black powder. CoPt3-NC was obtained after grinding and acid washing.
[0055] Example 4:
[0056] (1) Dissolve 291 mg of cobalt nitrate hexahydrate in 25 ml of methanol to form a homogeneous solution, and add 15.5 mg of chloroplatinic acid hexahydrate. Stir at room temperature for 10 minutes to obtain solution A.
[0057] (2) Dissolve 164.2 mg of 2-methylimidazole in 25 ml of methanol to form a homogeneous solution, which is solution B;
[0058] (3) Add solution B to solution A and stir continuously for 12 h, then precipitate for 12 h; wash the precipitate three times with methanol and dry it in a drying oven at 60 ℃ for 12 h. The purple powder obtained is Pt / ZIF-67.
[0059] (4) Mix 100 mg Pt / ZIF-67 with 30 mg melamine, grind them together, place them in a ceramic boat in a tube furnace, heat them to 500 °C at a heating rate of 3 °C / min and hold for 2 h under an Ar protective atmosphere, then heat them to 900 °C at a heating rate of 2 °C / min and calcine them at high temperature for 2 h to obtain a black powder. After grinding and acid washing, CoPt3-NC is obtained.
[0060] Example 5:
[0061] (1) Dissolve 291 mg of cobalt nitrate hexahydrate in 25 ml of methanol to form a homogeneous solution, and add 15.5 mg of chloroplatinic acid hexahydrate. Stir at room temperature for 10 minutes to obtain solution A.
[0062] (2) Dissolve 164.2 mg of 2-methylimidazole in 25 ml of methanol to form a homogeneous solution, which is solution B;
[0063] (3) Add solution B to solution A and stir continuously for 12 h, then precipitate for 12 h; wash the precipitate three times with methanol and dry it in a drying oven at 60 ℃ for 12 h. The purple powder obtained is Pt / ZIF-67.
[0064] (4) 100 mg Pt / ZIF-67 and 30 mg melamine were mixed and ground and placed in a ceramic boat in a tube furnace. Under the protective atmosphere of Ar containing 10 Vol% H2, the temperature was raised to 500 ℃ at a heating rate of 3 ℃ / min and held for 2 h. Then the temperature was raised to 900 ℃ at a heating rate of 2 ℃ / min and calcined at high temperature for 5 h to obtain black powder. CoPt3-NC was obtained after grinding and acid washing.
[0065] Comparative Example 1:
[0066] Commercial platinum-carbon catalyst with 20% platinum content.
[0067] The catalyst prepared in Example 1 was characterized and analyzed as follows:
[0068] Figure 2 The scanning electron microscope image shows that the sample still retains its dodecahedral shape, with uniformly sized metal particles dispersed on it.
[0069] Figure 3 The HAADF-STEM image shows uniformly distributed bright spots, indicating the presence of a large number of metallic nanoparticles. Energy-dispersive X-ray spectroscopy (EDS) elemental distribution confirms that these nanoparticles are composed of Co and Pt and are uniformly distributed on a nitrogen-doped carbon support.
[0070] Figure 4The transmission electron microscope image shows that the size of the metal particles is about 12 nm.
[0071] Figure 5 The XRD pattern shows diffraction peaks at 40.5° and 41.7° that correspond to the (110) and (111) crystal planes (PDF#29-0499) of the intermetallic compound CoPt3. This indicates the presence of CoPt3 in the sample. Furthermore, the peaks near 43° and 77.5° can be attributed to CoO, likely due to oxidation from exposure to air. No significant Co characteristic peaks were observed in CoPt3-NC, indicating successful removal of agglomerated cobalt particles through acid washing.
[0072] Figure 6 The N2 adsorption-desorption isotherm indicates that the specific surface area of CoPt3-NC is 93.3 m². 2 / g.
[0073] Furthermore, the platinum content of the sample in Example 1 was determined to be 3.44% by ICP-OES.
[0074] The EOR performance of the catalysts in Example 1 and Comparative Example 1 was tested under a three-electrode system. The specific test conditions are as follows:
[0075] The working electrode is a carbon cloth electrode, the counter electrode is a platinum sheet electrode, and the reference electrode is a saturated calomel electrode.
[0076] The test environment was a mixed solution of 0.5 M H2SO4 and 0.5 M CH3CH2OH, the scan potential was 0-1.5 V, and the scan rate was 0.5 mV.
[0077] Ink composition: 5 mg catalyst powder (the catalyst prepared in Example 1 and a commercial platinum-carbon catalyst with 20% platinum content, respectively), 500 μL ethanol, 500 μL deionized water, mixed evenly, and ultrasonicated in a water bath for 30 min to disperse it into a uniform catalyst ink with a concentration of 5 mg / mL.
[0078] Using a pipette with a volume of 10 μL, draw up 10 μL of catalyst ink and evenly drop it onto the carbon cloth, making its effective area 1 × 1 cm. 2 The electrode was dried by placing it in the weak light at the edge of the infrared lamp, repeating this process ten times. Finally, 20 μL of Nafion solution was evenly applied, and the electrode was allowed to air dry naturally to obtain the working electrode.
[0079] Figure 7The LSV curve of its application in EOR shows that, compared with commercial Pt / C, the onset potential is reduced by 57 mV and the oxidation peak current density is increased by 1.23 times. This result indicates that the CoPt3-NC catalyst optimizes the electronic structure of Pt through the alloying effect of Co and Pt. Combined with the dispersion and confinement effect of the nitrogen-carbon support, it effectively improves the intrinsic activity, reaction kinetics and structural stability of the electrocatalytic reaction, exhibiting electrocatalytic performance superior to commercial Pt / C.
[0080] Figure 8 For its Tafel slope used in EOR, the Tafel slope of CoPt3-NC (106 mV dec) -1 ) lower than Pt / C (119 mV dec -1 The smaller the Tafel slope, the lower the charge transfer resistance and the faster the reaction kinetics of the electrocatalytic reaction. This result indicates that the CoPt3-NC catalyst prepared in this invention effectively optimizes the electronic structure of the active sites, lowers the energy barrier of the electrocatalytic reaction, and significantly improves the kinetic rate of the catalytic reaction through the synergistic effect of Co and Pt alloying.
[0081] Figure 9 The EIS plots for its application in EOR show that the charge transfer resistance of Pt / C is 35.66 Ω, while that of CoPt3-NC is 32.88 Ω. This is because the charge transfer rate on CoPt3-NC is faster, resulting in higher intrinsic catalytic activity than commercial platinum-carbon.
[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for preparing a cobalt-platinum intermetallic compound confined to a nitrogen-doped carbon framework, characterized in that, Includes the following steps: (1) Add chloroplatinic acid hexahydrate to the cobalt salt solution and stir to obtain solution A; dissolve 2-methylimidazole in the solvent to form a homogeneous solution, which is solution B; add solution B to solution A and stir continuously, then precipitate; wash and dry to obtain purple powder, which is Pt / ZIF-67; (2) Pt / ZIF-67 and melamine were mixed and ground and placed in a ceramic boat in a tube furnace. Under a protective atmosphere, the temperature was raised to 400℃-500℃ at a heating rate of 2-6℃ / min and held for 1-3 h. Then the temperature was raised to 700℃-1000℃ at a heating rate of 1-4℃ / min and calcined at high temperature for 2-5 h to obtain black powder. CoPt3-NC was obtained after grinding and acid washing.
2. The method for preparing the cobalt-platinum intermetallic compound confined on a nitrogen-doped carbon framework according to claim 1, characterized in that: In step (1), the molar ratio of cobalt salt, chloroplatinic acid hexahydrate and 2-methylimidazole is 100:(2-4):(1-3); the mass ratio of Pt / ZIF-67 to melamine is 10:(2-5).
3. The method for preparing the cobalt-platinum intermetallic compound confined on a nitrogen-doped carbon framework according to claim 1, characterized in that: In step (1), the cobalt salt is one of cobalt sulfate heptahydrate, cobalt nitrate hexahydrate, and cobalt chloride hexahydrate.
4. The method for preparing the cobalt-platinum intermetallic compound confined on a nitrogen-doped carbon framework according to claim 1, characterized in that: In step (1), the solvent of the cobalt salt solution is the same as the solvent used for imidazole, and is selected from at least one of methanol, ethanol, and water.
5. The method of claim 1, wherein: In step (1), the stirring time after mixing solution A and solution B is 10-24 h, and the sedimentation time is 5-24 h.
6. The method for preparing the cobalt-platinum intermetallic compound confined on a nitrogen-doped carbon framework according to claim 1, characterized in that: In step (2), the protective atmosphere used is one of N2, Ar, N2 containing 5-10 vol% H2, or Ar containing 5-10 vol% H2.
7. The method for preparing the cobalt-platinum intermetallic compound confined on a nitrogen-doped carbon framework according to claim 1, characterized in that: In step (2), the solution used for pickling is one of 1-2 M nitric acid, sulfuric acid, or perchloric acid solution.
8. A cobalt-platinum intermetallic compound confined to a nitrogen-doped carbon framework, characterized in that: The cobalt-platinum intermetallic compound is prepared by the preparation method according to any one of claims 1-7.
9. The application of the cobalt-platinum intermetallic compound confined on a nitrogen-doped carbon framework as described in claim 8 in the electrocatalytic oxidation of ethanol.