A multi-heteroatom doped co / pd nano-catalyst based on cobalt-nitrogen pre-coordinated carbon precursor and a preparation method and application thereof

Abstract

The application discloses a kind of based on cobalt-nitrogen pre-coordination carbon precursor derived polyatomic heteroatom doped Co / Pt nano catalyst and its preparation method and application, belong to fuel cell catalyst and its preparation technical field.The application solves the problem of expensive anode catalyst Pt / C of existing PEMFCs.The application is based on cobalt-nitrogen pre-coordination carbon precursor, solvent assisted metal-organic framework self-assembly technology is used, with methanol as solvent medium, by doping S or Br, the dispersibility of material and its morphology feature are improved, metal-organic framework precursor is obtained, further using the method that physical suction filter and high-temperature heat treatment are combined, make the uniform loading of platinum particles in MOF derived material, based on cobalt-nitrogen pre-coordination carbon precursor derived polyatomic heteroatom doped Co / Pt nano catalyst is obtained.The catalyst improves noble metal atom utilization rate under the premise of guaranteeing excellent activity, realizes the purpose of reducing the amount of noble metal.

Description

Technical Field

[0001] This invention relates to a multi-component heteroatom-doped Co / Pt nanocatalyst derived from a cobalt-nitrogen pre-coordinated carbon precursor, its preparation method, and its application, belonging to the technical field of catalysts for fuel cells and their preparation. Background Technology

[0002] Hydrogen (H2) is considered an ideal energy carrier to replace fossil fuels. Proton exchange membrane fuel cells (PEMFCs) can directly convert the chemical energy in hydrogen into electrical energy through the hydrogen oxidation reaction, and have the characteristics of high energy utilization and clean and pollution-free operation, thus showing great promise for commercial applications.

[0003] However, the anodic HOR reaction of PEMFCs faces serious challenges. It is well known that Pt / C catalysts are currently one of the best choices for the anodic HOR reaction of PEMFCs, but Pt / C catalysts are expensive. Therefore, developing highly active, highly stable, and low-cost low-platinum HOR catalysts is a critical problem that urgently needs to be solved. Summary of the Invention

[0004] In order to solve the above-mentioned technical problems of existing anode catalysts of PEMFCs, this invention provides a multi-component heteroatom-doped Co / Pt nanocatalyst derived from a cobalt-nitrogen pre-coordinated carbon precursor, its preparation method and application.

[0005] The technical solution of the present invention:

[0006] One objective of this invention is to provide a method for preparing multi-component heteroatom-doped Co / Pt nanocatalysts, the method comprising the following steps:

[0007] (1) Mix the bromine source or sulfur source, cobalt salt, zinc salt and solvent, and ultrasonically stir to obtain a precursor solution;

[0008] (2) Under stirring conditions, the ligand solution was added to the precursor solution, dispersed at room temperature and then precipitated to obtain a metal-organic framework precursor solution;

[0009] (3) The metal-organic framework precursor solution was centrifuged, the precipitate was washed and dried under vacuum to obtain purple cobalt-nitrogen coordinated carbon source powder.

[0010] (4) The cobalt-nitrogen coordinated carbon source powder was heat-treated under a reducing atmosphere to obtain a coordination polymer catalyst powder with nitrogen lone pair electron anchoring cobalt.

[0011] (5) Mix the nitrogen lone pair electron anchoring cobalt coordination polymer catalyst powder, chloroplatinic acid solution and water, and stir magnetically until uniform to obtain Pt-loaded nitrogen lone pair electron anchoring cobalt coordination polymer aqueous solution.

[0012] (6) The aqueous solution of the nitrogen lone pair electron anchored cobalt loaded with Pt was filtered by vacuum filtration using a microporous filter membrane, washed with deionized water, and vacuum dried. The dried black powder was then pyrolyzed under a reducing atmosphere to obtain a multi-component heteroatom-doped Co / Pt nanocatalyst.

[0013] Further specifying, (1) the bromine source is sodium bromide, potassium bromide, hexadecyltrimethylammonium bromide or benzalkonium bromide; the sulfur source is nickel disulfide, cobalt disulfide, sodium dodecyl sulfate or sodium dodecylbenzene sulfonate; the cobalt salt is cobalt acetylacetonate, cobalt dichloride, cobalt nitrate or cobalt carbonate; the zinc salt is zinc acetate, zinc chloride, zinc nitrate or zinc sulfide; the solvent is methanol.

[0014] Further specified, (1) the ratio of bromine source or sulfur source, cobalt salt and zinc salt is (0.01~0.4)g:(1~10)mmol:1mmol, and the solvent volume is 110~130mL.

[0015] Further specifying, (1) the ratio of bromine source, sulfur source, cobalt salt and zinc salt is (0.05~0.3)g: (0.05~0.3)g: (2~8)mmol:1mmol.

[0016] Further specifying, (1) the ratio of bromine source, sulfur source, cobalt salt and zinc salt is (0.1~0.2)g:(0.1~0.2)g:(3~5)mmol:1mmol.

[0017] Further, the ultrasonic stirring time in (1) is 0.5 to 1.5 h.

[0018] Further specified, (2) the ligand concentration in the obtained metal-organic framework precursor solution is 1.02 mol / L.

[0019] Further, in (2), the dispersion time at room temperature is 18-20 h; the precipitation time is 6-8 h.

[0020] Further specifying, the dispersion treatment in (2) includes ultrasonication and stirring, with ultrasonic power of 60-100W and time of 15-30min; stirring speed of 300-400rpm and time of 18-20h.

[0021] Further specified, in (3) the centrifugation speed is 6000-11000 rpm and the time is 30-60 min.

[0022] Furthermore, in (3), the centrifugal speed is 7000 to 10000 rpm.

[0023] Furthermore, in (3), the centrifugal speed is 8000-9000 rpm.

[0024] Further specified, (3) the drying temperature is 30 to 100°C and the time is 12 to 24 hours.

[0025] Furthermore, the drying temperature in (3) is 40-90℃h.

[0026] Furthermore, the drying temperature in (3) is 60-80℃h.

[0027] Further specified, (4) the heat treatment temperature is 600~1000℃ and the time is 8~12h.

[0028] Further specified, the heating rate of the heat treatment process in (4) is 2 to 5 °C / min.

[0029] Furthermore, the heat treatment temperature in (4) is 750 to 950°C.

[0030] Furthermore, the heat treatment temperature in (4) is 800-900℃.

[0031] Further specifying, the reducing atmosphere in (4) is a mixture of H2 and Ar.

[0032] Further specified, in (5) the concentration of chloroplatinic acid solution is 0.0244 mol / L, and the mass-volume ratio of nitrogen lone pair electron anchoring cobalt coordination polymer catalyst powder, chloroplatinic acid solution and water is 1 g: (1~100) mL: (100~1000) mL.

[0033] Furthermore, in (5), the mass-to-volume ratio of the nitrogen lone pair electron-anchored cobalt coordination polymer catalyst powder, chloroplatinic acid solution, and water is 1 g: (5-50) mL: (500-1000) mL.

[0034] Furthermore, in (5), the mass-to-volume ratio of the nitrogen lone pair electron-anchored cobalt coordination polymer catalyst powder, chloroplatinic acid solution, and water is 1 g: (8-30) mL: (800-1000) mL.

[0035] Further specified, in (5) the magnetic stirring speed is 300-400 rpm and the time is 2-4 h.

[0036] Further specified, (6) the pore size of the microporous filter membrane is 20μm and the diameter is 50mm.

[0037] Further specified, (6) the drying temperature is 30 to 100°C and the time is 6 to 12 hours.

[0038] Furthermore, the drying temperature in (6) is 40–90°C.

[0039] Furthermore, the drying temperature in (6) is 60-80℃.

[0040] Further, in (6), the pyrolysis temperature is 100-700℃ and the time is 6-8h.

[0041] Furthermore, the pyrolysis temperature in (6) is 300–600 °C.

[0042] Furthermore, the pyrolysis temperature in (6) is 400-500℃.

[0043] Further, the heating rate during the pyrolysis process in (6) is 2 to 5 °C / min.

[0044] Further specifying, the reducing atmosphere in (6) is a mixture of H2 and Ar.

[0045] The second objective of this invention is to provide a multi-component heteroatom-doped Co / Pt nanocatalyst prepared by the above-described method.

[0046] The third objective of this invention is to provide an application of the above-mentioned multi-component heteroatom-doped Co / Pt nanocatalyst, specifically as an anode catalyst for PEMFCs.

[0047] Further defining the beneficial effects of using HOR anode electrocatalyst material in PEMFCs for catalytic anode hydrogenation reaction:

[0048] This invention, based on a cobalt-nitrogen pre-coordinated carbon precursor, employs solvent-assisted metal-organic framework (SOMF) self-assembly technology with methanol as the solvent medium. By doping with S or Br to improve the material's dispersibility and morphology, a metal-organic framework (MOF) precursor is obtained. Furthermore, a combination of physical filtration and high-temperature heat treatment is used to uniformly load platinum (Pt) particles into the MOF-derived material, resulting in a multi-component heteroatom-doped Co / Pt nanocatalyst derived from the cobalt-nitrogen pre-coordinated carbon precursor. This catalyst improves the utilization rate of noble metal atoms while maintaining excellent activity, thus reducing the amount of noble metal required. Experimental results show that the current density of the three samples (Pt@Co-BrNC, Pt@Co-SNC, and Pt@Co-NC) in 0.1M HClO4 reaches 2.354 mA / cm². 2 2.133 mA / cm 2 and 1.782 mA / cm 2 It is a promising PEMFC anode catalyst. Attached Figure Description

[0049] Figure 1 The image shows a scanning electron microscope (SEM) image of Pt@Co-BrNC prepared in Example 1.

[0050] Figure 2The image shows a scanning electron microscope (SEM) image of the Pt@Co-SNC prepared in Example 2.

[0051] Figure 3 The image shows a scanning electron microscope image of the Pt@Co-NC prepared in Comparative Example 1.

[0052] Figure 4 The X-ray diffraction peaks of Co-BrNC, Co-SNC and Co-NC prepared in Examples 1-2 and Comparative Example 1 are shown.

[0053] Figure 5 The X-ray diffraction peaks of Pt@Co-BrNC, Pt@Co-SNC and Pt@Co-NC prepared in Examples 1-2 and Comparative Example 1 are shown.

[0054] Figure 6 Linear sweep voltammetry plots of the Pt@Co-BrNC catalyst prepared in Example 1 were measured under acidic conditions at different rotation speeds.

[0055] Figure 7 Linear sweep voltammetry plots of the Pt@Co-SNC catalyst prepared in Example 1 were measured under acidic conditions at different rotation speeds.

[0056] Figure 8 Linear sweep voltammetry (LSV) plots of the Pt@Co-NC catalyst prepared in Comparative Example 1 were obtained under acidic conditions and at different rotation speeds. Detailed Implementation

[0057] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0058] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0059] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0060] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0061] Example 1

[0062] (1) Dissolve 3 mmol cobalt nitrate and 1 mmol zinc nitrate in 30 mL methanol, stir well to obtain a metal solution, and set aside.

[0063] Dissolve 0.15 g of hexadecyltrimethylammonium bromide in 10 mL of methanol, stir until homogeneous, mix with the metal solution, and sonicate at room temperature for 20 min to obtain a homogeneous precursor solution.

[0064] (2) Dissolve 1.96g of dimethylimidazole in 20mL of methanol solution, stir well to obtain ligand solution, and set aside for later use;

[0065] The precursor solution was slowly added to the ligand solution at a rotation speed of 300–400 rpm, resulting in a deep purple solution. The solution was first ultrasonically dispersed at room temperature (80 W for 30 min), followed by stirring at 320 rpm for 19 h, and finally settled for 7 h. The purpose of mixing the metal solution and ligand solution to obtain a homogeneous dispersion is to create a uniform reaction environment, allowing for sufficient coordination reactions between the metal ions and the organic ligands, thereby reducing crystal defects.

[0066] (3) After precipitation, the powder was centrifuged at 8000 rpm / min, washed 5 times with anhydrous ethanol, and dried under vacuum at 70°C for 12 h to obtain purple powder.

[0067] (4) The purple powder obtained in step (3) is heat-treated in a reducing atmosphere. Specifically, the temperature is raised to 900℃ at a heating rate of 5℃ / min, held for 2h, and then naturally cooled to room temperature to obtain a nitrogen lone pair electron anchored cobalt coordination polymer catalyst powder, named Co-BrNC.

[0068] (5) Take 50 mg of Co-BrNC and add it to 50 mL of deionized water. After stirring evenly, add 0.5 mL of chloroplatinic acid solution with a concentration of 0.20244 mol / L. Stir magnetically at room temperature for 2 h to obtain a uniformly dispersed Co-BrNC aqueous solution loaded with Pt.

[0069] (6) The Pt-loaded Co-BrNC aqueous solution obtained in step (5) was filtered using a microporous filter membrane with a pore size of 20 μm and a diameter of 50 mm. The solution was washed with deionized water and dried in a vacuum drying oven at 70 °C for 12 h to obtain a black powder.

[0070] (7) The black powder obtained in step (6) is subjected to pyrolysis treatment in a mixed atmosphere of H2 / Ar. The specific pyrolysis temperature is 500℃ and the time is 6-8h. After natural cooling to room temperature, a multi-component heteroatom-doped Co / Pt nanocatalyst based on cobalt-nitrogen pre-coordinated carbon precursor is obtained and named Pt@Co-BrNC.

[0071] Example 2

[0072] The difference between this embodiment and Example 1 is that 0.15g of sodium dodecyl sulfate is used to replace 0.15g of hexadecyltrimethylammonium bromide in step (1), while the remaining process steps and parameter settings are the same as in Example 1.

[0073] The nitrogen lone pair electron-anchored cobalt coordination polymer catalyst powder obtained in step (4) of this embodiment is named Co-SNC, and the multi-component heteroatom-doped Co / Pt nanocatalyst derived from the cobalt-nitrogen pre-coordinated carbon precursor obtained in step (7) is named Pt@Co-SNC.

[0074] Comparative Example 1

[0075] The difference between this comparative example and Example 1 is that the amount of hexadecyltrimethylammonium bromide used in step (1) is 0g, while the remaining process steps and parameter settings are the same as in Example 1.

[0076] The nitrogen lone pair electron-anchored cobalt coordination polymer catalyst powder obtained in step (4) of this embodiment is named Co-NC, and the multi-component heteroatom-doped Co / Pt nanocatalyst derived from the cobalt-nitrogen pre-coordinated carbon precursor obtained in step (7) is named Pt@Co-NC.

[0077] Example of effect

[0078] (1) The microstructures of Pt@Co-BrNC, Pt@Co-SNC, and Pt@Co-NC prepared in Examples 1-2 and Comparative Example 1 were characterized, and the results are as follows: Figures 1-3As shown in the figure, Pt@Co-BrNC exhibits excellent dispersibility and high specific surface area due to its regular cubic structure, clear metallic framework, uniform particle size, and reasonable interstitial distribution. These characteristics provide Pt@Co-BrNC with a large number of accessible active sites, thereby enhancing its performance. In contrast, although Pt@Co-SNC also has good dispersibility, it is slightly inferior in terms of shape regularity and particle uniformity, resulting in a relatively smaller number of active sites. As for Pt@Co-NC, obvious particle aggregation is observed, with poor dispersibility and irregular shape, thus the exposed active sites are relatively limited.

[0079] (2) The X-ray diffraction peak comparison spectra of Co-BrNC, Co-SNC and Co-NC prepared in Examples 1-2 and Comparative Example 1 are shown below. Figure 4 As shown in the figure, the diffraction peak positions of Co-BrNC and Co-SNC are slightly shifted compared to Co-NC, indicating that Br and S atoms are incorporated into the lattice instead of Br and S atoms. The slight strain caused by the incorporation of Br and S also leads to different degrees of shift in the diffraction peaks of Co-BrNC and Co-SNC.

[0080] (3) The X-ray diffraction peak comparison spectra of Pt@Co-BrNC, Pt@Co-SNC and Pt@Co-NC prepared in Examples 1-2 and Comparative Example 1 are shown below. Figure 5 As shown in the figure, the diffraction peak positions of Pt@Co-BrNC and Pt@Co-SNC are shifted to smaller angles compared to Pt@Co-NC. This indicates that the introduction of Pt helps to release the original stress and lattice structure, thereby further changing its lattice distortion state.

[0081] (4) Electrodes were prepared using Pt@Co-BrNC, Pt@Co-SNC, and Pt@Co-NC as catalysts, and linear sweep voltammetry (LSV) tests were performed. The specific procedure was as follows: 5 mg of Pt@Co-BrNC, 5 mg of Pt@Co-SNC, and 5 mg of Pt@Co-NC were weighed, mixed with 2 mg of carbon black, and dissolved in 1.5 mL of anhydrous ethanol. The mixture was ultrasonically dispersed until homogeneous. Then, 0.5 mL of 0.5% Nafion solution was added, and the mixture was ultrasonically dispersed for 2 h to obtain a homogeneous catalyst slurry. The catalyst slurry was then uniformly coated onto a glassy carbon electrode, and linear sweep voltammetry (LSV) tests were performed under an H2 atmosphere.

[0082] The linear sweep voltammograms of Pt@Co-BrNC, Pt@Co-SNC, and Pt@Co-NC catalysts measured at different rotation speeds in 0.1M HClO4 are shown below. Figures 6-8As shown in the figure, the current densities of the three catalysts, Pt@Co-BrNC, Pt@Co-SNC, and Pt@Co-NC, measured at 1600 rpm in 0.1 M HClO4 reached 2.354 mA / cm². 2 2.133 mA / cm 2 and 1.782 mA / cm 2 This demonstrates that the catalyst prepared in the above examples has excellent activity in catalyzing the hydrogenation reaction.

[0083] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing a multi-component heteroatom-doped Co / Pt nanocatalyst, characterized in that, include: (1) Mix the bromine source or sulfur source, cobalt salt, zinc salt and solvent, and ultrasonically stir to obtain a precursor solution; (2) Under stirring conditions, the ligand solution was added to the precursor solution, dispersed at room temperature and aged to obtain a metal-organic framework precursor solution; (3) The metal-organic framework precursor solution was centrifuged, the precipitate was washed and dried under vacuum to obtain purple cobalt-nitrogen coordinated carbon source powder. (4) The cobalt-nitrogen coordinated carbon source powder was heat-treated under a reducing atmosphere to obtain a coordination polymer catalyst powder with nitrogen lone pair electron anchoring cobalt. (5) Mix the nitrogen lone pair electron anchoring cobalt coordination polymer catalyst powder, chloroplatinic acid solution and water, and stir magnetically until uniform to obtain Pt-loaded nitrogen lone pair electron anchoring cobalt coordination polymer aqueous solution. (6) The aqueous solution of the nitrogen lone pair electron anchored cobalt loaded with Pt was filtered by microporous filter membrane, washed with deionized water, and vacuum dried. The dried black powder was pyrolyzed under a reducing atmosphere to obtain multi-component heteroatom doped Co / Pt nanocatalyst. The sulfur source in (1) is nickel disulfide, cobalt disulfide, sodium dodecyl sulfate or sodium dodecylbenzene sulfonate; The concentration of chloroplatinic acid solution in (5) is 0.0244 mol / L, and the mass-volume ratio of nitrogen lone pair electron anchoring cobalt coordination polymer catalyst powder, chloroplatinic acid solution and water is 1 g: (1~100) mL: (100~1000) mL; The multi-component heteroatom-doped Co / Pt nanocatalyst is used as an HOR anode electrocatalyst material in PEMFCs to catalyze the hydrogenation reaction at the anode.

2. The preparation method according to claim 1, characterized in that, (1) The bromine source is sodium bromide, potassium bromide, hexadecyltrimethylammonium bromide or benzalkonium bromide; the cobalt salt is cobalt acetylacetonate, cobalt dichloride, cobalt nitrate or cobalt carbonate; the zinc salt is zinc acetate, zinc chloride, zinc nitrate or zinc sulfide; the ligand is benzimidazole, 2-methylimidazole, 3,5-dimethylpyridine or 1,2,4-triazole; the solvent is methanol.

3. The preparation method according to claim 1, characterized in that, (1) The ratio of bromine source or sulfur source, cobalt salt and zinc salt is (0.01~0.4)g: (1~10)mmol:1mmol.

4. The preparation method according to claim 1, characterized in that, (2) The ligand concentration in the obtained metal-organic framework precursor solution is 1.02 mol / L.

5. The preparation method according to claim 1, characterized in that, (2) The dispersion time at room temperature is 18~20h; the aging time is 6~8h.

6. The preparation method according to claim 1, characterized in that, (4) The heat treatment temperature is 600~1000℃ and the time is 8~12h.

7. The preparation method according to claim 1, characterized in that, (6) The pyrolysis temperature is 100~700℃ and the time is 6~8h.

8. A multi-component heteroatom-doped Co / Pt nanocatalyst prepared by the method according to any one of claims 1 to 7.

9. An application of the multi-component heteroatom-doped Co / Pt nanocatalyst according to claim 8, characterized in that, Used as an anode catalyst for PEMFCs.

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