Preparation method and application of Mn-Co ZIF-11-950 oxygen reduction electrocatalyst

Abstract

The invention relates to an electrocatalyst, in particular to a preparation method of a Mn-Co ZIF-11-950 oxygen reduction electrocatalyst. The preparation method comprises the following steps: dissolving benzimidazole and phthalocyanine with negative charges in a solvent I, and then adding a structure-directing agent and ammonia water to obtain a solution A; dissolving zinc salt and phthalocyanine with positive charges in a solvent II to obtain a solution B; mixing the solution B with the solution A to obtain a Mn-Co ZIF-11 precursor; and carrying out pyrolysis on the Mn-Co-coated ZIF-11 precursor in an inert atmosphere, so as to obtain the Mn-Co-coated ZIF-11-950 oxygen reduction electrocatalyst. The electrocatalyst prepared by the invention has excellent oxygen reduction activity and durability.

Description

Technical Field

[0001] The invention relates to an electrocatalyst, and in particular to a method for preparing a Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst. Background Art

[0002] Under the dual challenges of the global energy crisis and environmental pollution, my country, as one of the world's largest energy consumers, is facing the important task of energy structure transformation and green and low-carbon development. Polymer electrolyte membrane fuel cells (PEMFCs) have been widely studied as an environmentally friendly and efficient energy conversion device. The development of low-cost, widely applicable, and highly active non-precious metal electrocatalysts for oxygen reduction reaction (ORR) is of key significance for the large-scale commercialization of PEMFCs. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide an electrocatalyst with high oxygen reduction activity.

[0004] The invention provides a method for preparing a Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst. The preparation method comprises the following steps: dissolving benzimidazole and negatively charged phthalocyanine in a solvent I, and then adding a structure directing agent and ammonia water to obtain a solution A; dissolving a zinc salt and positively charged phthalocyanine in a solvent II to obtain a solution B; mixing the solution B with the solution A to obtain a Mn-Co@ZIF-11 precursor; and pyrolyzing the Mn-Co@ZIF-11 precursor under an inert atmosphere to obtain the Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst.

[0005] Furthermore, the concentration of the benzimidazole is 3-9M.

[0006] Furthermore, the negatively charged phthalocyanine is tetracarboxylic phthalocyanine manganese or tetracarboxylic phthalocyanine cobalt, and the concentration of the negatively charged phthalocyanine is 0.4-0.8M.

[0007] Furthermore, the volume ratio of the solvent I, the structure directing agent and the ammonia water is 105-180:150-200:1.

[0008] Furthermore, the concentration of the zinc salt is 2-5M.

[0009] Furthermore, the positively charged phthalocyanine is tetraaminophthalocyanine cobalt or tetraaminophthalocyanine manganese, and the concentration of the positively charged phthalocyanine is 0.4-0.8M.

[0010] Furthermore, the mixing and stirring time of the solution B and the solution A is 12-24 hours.

[0011] Furthermore, the pyrolysis condition is 700-1000° C. for 2-4 hours.

[0012] Another object of the present invention is to provide a Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst prepared by the above preparation method.

[0013] Another object of the present invention is to provide an application of the above-mentioned Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst in a proton exchange membrane fuel cell.

[0014] The beneficial effects of the present invention are:

[0015] The present invention introduces two metal phthalocyanine molecules with electrostatic interaction into the ZIF-11 matrix by means of the large pore size of the RHO-type ZIF-11 and the self-assembly interaction between the RHO-type ZIF-11 and the metal macrocyclic compound, uses ZIF-11 as an intermediate template, adjusts the distribution of metal-nitrogen 4 active centers, promotes their uniform dispersion, avoids large-scale aggregation of metal centers, forms composite nanocrystals rich in manganese-nitrogen 4 and cobalt-nitrogen 4 active center sources, fully improves the oxygen reduction active site density, realizes the regulation of the precursor structure, and is beneficial to the improvement of oxygen reduction activity and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention is attached Figure 8 width,

[0017] Figure 1 X-ray diffraction (XRD) patterns of the Mn-Co@ZIF-11 precursor and the simulated ZIF-11 obtained in Example 1;

[0018] Figure 2 The XRD pattern of the Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst obtained in Example 1;

[0019] Figure 3 This is the oxygen reduction polarization curve of the Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst obtained in Example 1 under alkaline conditions;

[0020] Figure 4 The oxygen reduction polarization curve of the Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst obtained in Example 1 before and after the durability test under alkaline conditions;

[0021] Figure 5 This is a comparison chart of the ORR activity of the electrocatalysts obtained in Comparative Example 2 and Example 1;

[0022] Figure 6 This is a comparison chart of the ORR activity of the electrocatalysts obtained in Comparative Example 3 and Example 1;

[0023] Figure 7 This is a comparison chart of the ORR activity of the electrocatalysts obtained in Comparative Example 4 and Example 1;

[0024] Figure 8 This is the XRD pattern of the electrocatalyst obtained in Comparative Example 4. DETAILED DESCRIPTION

[0025] The following non-limiting embodiments may enable a person skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0026] Example 1

[0027] 3M benzimidazole and 0.4M tetracarboxylic manganese phthalocyanine were dissolved in 20mL of anhydrous methanol, and then 36mL of toluene and 0.2mL of ammonia water were added to obtain solution A; 2M zinc acetate and 0.4M tetraaminophthalocyanine cobalt were dissolved in 6mL of anhydrous methanol to obtain solution B; solution B was poured into solution A and stirred for 12h to fully crystallize to obtain a brown precipitate, which was centrifuged, washed, and dried at 80°C for 24h to obtain a Mn-Co@ZIF-11 precursor; the Mn-Co@ZIF-11 precursor was pyrolyzed at 950°C under Ar atmosphere for 2h to obtain a Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst.

[0028] like Figure 1 As shown, the XRD results show that the structure of the prepared Mn-Co@ZIF-11 precursor is RHO-type ZIF-11.

[0029] like Figure 2 As shown, the XRD results show that the prepared Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst is mainly amorphous carbon accompanied by CoO, CoMnO, and Mn elements.

[0030] In an O2-saturated 0.1M KOH solution, the oxygen reduction polarization curve was tested with a scanning voltage range of 0-1.2V (vs. RHE), Hg / HgO as the reference electrode, glassy carbon as the working electrode, and graphite rod as the counter electrode. The results are shown in Figure 3 The results showed that the prepared Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst had excellent oxygen reduction activity with a half-wave potential of 0.868 V (vs. RHE).

[0031] In an O2-saturated 0.1M KOH solution, the oxygen reduction polarization curve was tested with a scanning voltage range of 0-1.2V (vs. RHE), Hg / HgO as the reference electrode, glassy carbon as the working electrode, and graphite rod as the counter electrode. The results are shown in Figure 4The results showed that the prepared Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst had excellent durability, and the half-wave potential only decayed by 13 mV after 3000 cycles of dynamic potential scanning.

[0032] Example 2

[0033] 6M benzimidazole and 0.4M tetracarboxylic manganese phthalocyanine were dissolved in 20mL of anhydrous methanol, and then 36mL of toluene and 0.2mL of ammonia water were added to obtain solution A; 4M zinc acetate and 0.4M tetraaminophthalocyanine cobalt were dissolved in 6mL of anhydrous methanol to obtain solution B; solution B was poured into solution A and stirred for 24h to fully crystallize to obtain a brown precipitate, which was centrifuged, washed, and dried at 80°C for 24h to obtain a Mn-Co@ZIF-11 precursor; the Mn-Co@ZIF-11 precursor was pyrolyzed at 950°C for 2h under Ar atmosphere to obtain a Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst.

[0034] Example 3

[0035] 9M benzimidazole and 0.8M tetracarboxylic manganese phthalocyanine were dissolved in 20mL of anhydrous methanol, and then 36mL of toluene and 0.2mL of ammonia water were added to obtain solution A; 6M zinc acetate and 0.8M tetraaminophthalocyanine cobalt were dissolved in 6mL of anhydrous methanol to obtain solution B; solution B was poured into solution A and stirred for 12h to fully crystallize to obtain a brown precipitate, which was centrifuged, washed, and dried at 80°C for 24h to obtain a Mn-Co@ZIF-11 precursor; the Mn-Co@ZIF-11 precursor was pyrolyzed at 950°C for 2h under Ar atmosphere to obtain a Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst.

[0036] Example 4

[0037] 3M benzimidazole and 0.4M tetracarboxyphthalocyanine cobalt were dissolved in 20mL of anhydrous methanol, and then 36mL of toluene and 0.2mL of ammonia water were added to obtain solution A; 3M zinc acetate and 0.4M tetraaminophthalocyanine manganese were dissolved in 6mL of anhydrous methanol to obtain solution B; solution B was poured into solution A and stirred for 18h to fully crystallize to obtain a brown precipitate, which was centrifuged, washed, and dried at 80°C for 24h to obtain a Mn-Co@ZIF-11 precursor; the Mn-Co@ZIF-11 precursor was pyrolyzed at 950°C for 2h under Ar atmosphere to obtain a Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst.

[0038] Comparative Example 1 (different stirring time)

[0039] 3M benzimidazole and 0.4M tetracarboxylic manganese phthalocyanine were dissolved in 20mL of anhydrous methanol, and then 36mL of toluene and 0.2mL of ammonia water were added to obtain solution A; 2M zinc acetate and 0.4M tetraaminophthalocyanine cobalt were dissolved in 6mL of anhydrous methanol to obtain solution B; solution B was poured into solution A, stirred for 6h to obtain a white precipitate, which was centrifuged, washed, and dried at 80°C for 24h to obtain a white powder precursor; the white powder precursor was pyrolyzed at 950°C under Ar atmosphere for 2h to obtain Mn / Co@ZIF-11-950 electrocatalyst.

[0040] The stirring time of Comparative Example 1 was too short, and a white precipitate was formed instead of the brown precipitate of the embodiment. The white precipitate was a ZIF-11 structure, did not react with phthalocyanine, and had a low oxygen reduction activity.

[0041] Comparative Example 2 (Different Types of Phthalocyanine Metal Centers)

[0042] 3M benzimidazole and 0.4M tetracarboxylic manganese phthalocyanine were dissolved in 20mL of anhydrous methanol, and then 36mL of toluene and 0.2mL of ammonia water were added to obtain solution A; 2M zinc acetate and 0.4M tetraaminophthalocyanine iron were dissolved in 6mL of anhydrous methanol to obtain solution B; solution B was poured into solution A and stirred for 12h to fully crystallize to obtain a brown precipitate, which was centrifuged, washed, and dried at 80℃ for 24h to obtain a Mn-Fe@ZIF-11 precursor; the Mn-Fe@ZIF-11 precursor was pyrolyzed at 950℃ for 2h under Ar atmosphere to obtain a Mn-Fe@ZIF-11-950 electrocatalyst.

[0043] In an O2-saturated 0.1M KOH solution, the oxygen reduction polarization curve was tested with a scanning voltage range of 0-1.2V (vs. RHE), Hg / HgO as the reference electrode, glassy carbon as the working electrode, and graphite rod as the counter electrode. The results are shown in Figure 5 The results showed that the half-wave potential of the prepared Mn-Fe@ZIF-11-950 electrocatalyst was 0.825 V (vs. RHE), which was 43 mV lower than that in Example 1.

[0044] Comparative Example 3 (Different Phthalocyanine Functional Group Types)

[0045] 3M benzimidazole and 0.4M tetrasulfonate manganese phthalocyanine were dissolved in 20mL of anhydrous methanol, and then 36mL of toluene and 0.2mL of ammonia water were added to obtain solution A; 2M zinc acetate and 0.4M cobalt tetraaminophthalocyanine were dissolved in 6mL of anhydrous methanol to obtain solution B; solution B was poured into solution A and stirred for 12h to fully crystallize to obtain a brown precipitate, which was centrifuged, washed, and dried at 80℃ for 24h to obtain a Mn-Co@ZIF-11 precursor; the Mn-Co@ZIF-11 precursor was pyrolyzed at 950℃ for 2h under Ar atmosphere to obtain a 1-Mn-Co@ZIF-11-950 electrocatalyst.

[0046] In an O2-saturated 0.1M KOH solution, the oxygen reduction polarization curve was tested with a scanning voltage range of 0-1.2V (vs. RHE), Hg / HgO as the reference electrode, glassy carbon as the working electrode, and graphite rod as the counter electrode. The results are shown in Figure 6 The results showed that the half-wave potential of the prepared 1-Mn-Co@ZIF-11-950 electrocatalyst was 0.827 V (vs. RHE), which was 41 mV lower than that in Example 1.

[0047] Comparative Example 4 (Different Catalyst Structures)

[0048] 9M benzimidazole and 0.8M tetracarboxylic manganese phthalocyanine were dissolved in 20mL of anhydrous methanol, and then 36mL of toluene and 0.2mL of ammonia water were added to obtain solution A; 6M zinc acetate and 0.8M tetraaminophthalocyanine cobalt were dissolved in 6mL of anhydrous methanol to obtain solution B; solution B was poured into solution A and stirred for 12h to fully crystallize to obtain a brown precipitate, which was centrifuged, washed, and dried at 80℃ for 24h to obtain a Mn-Co@ZIF-11 precursor; the Mn-Co@ZIF-11 precursor was pyrolyzed at 950℃ for 2h under Ar atmosphere, and then placed in 0.5M H2SO4 and refluxed at 85℃ for 2h to obtain a 2-Mn-Co@ZIF-11-950 electrocatalyst.

[0049] In an O2-saturated 0.1M KOH solution, the oxygen reduction polarization curve was tested with a scanning voltage range of 0-1.2V (vs. RHE), Hg / HgO as the reference electrode, glassy carbon as the working electrode, and graphite rod as the counter electrode. The results are shown in Figure 7 The results showed that the half-wave potential of the prepared 2-Mn-Co@ZIF-11-950 electrocatalyst was 0.811 V (vs. RHE), which was 57 mV lower than that in Example 1.

[0050] like Figure 8 As shown, the XRD results show that the prepared 2-Mn-Co@ZIF-11-950 electrocatalyst does not contain CoO, CoMnO, and Mn elements, but only an amorphous carbon structure.

Claims

1. A method for preparing a Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst, characterized in that: The preparation method comprises the following steps: Benzimidazole and negatively charged phthalocyanine are dissolved in solvent I, and then a structure directing agent and ammonia water are added to obtain solution A; Dissolve the zinc salt and the positively charged phthalocyanine in solvent II to obtain solution B; Solution B was mixed with solution A to obtain the Mn-Co@ZIF-11 precursor; The Mn-Co@ZIF-11 precursor was pyrolyzed under an inert atmosphere to obtain the Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst.

2. The preparation method according to claim 1, characterized in that: The concentration of the benzimidazole is 3-9M.

3. The preparation method according to claim 1, characterized in that: The negatively charged phthalocyanine is tetracarboxyl phthalocyanine manganese or tetracarboxyl phthalocyanine cobalt, and the concentration of the negatively charged phthalocyanine is 0.4-0.8M.

4. The preparation method according to claim 1, characterized in that: The volume ratio of the solvent I, the structure directing agent and the ammonia water is 105-180:150-200:

1.

5. The preparation method according to claim 1, characterized in that: The concentration of the zinc salt is 2-5M.

6. The preparation method according to claim 1, characterized in that: The positively charged phthalocyanine is tetraaminophthalocyanine cobalt or tetraaminophthalocyanine manganese, and the concentration of the positively charged phthalocyanine is 0.4-0.8M.

7. The preparation method according to claim 1, characterized in that: The mixing and stirring time of the solution B and the solution A is 12-24 hours.

8. The preparation method according to claim 1, characterized in that: The pyrolysis condition is 700-1000° C. for 2-4 hours.

9. A Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the Mn-Co@ZIF-11-950 oxygen reduction electrocatalyst according to claim 9 in a proton exchange membrane fuel cell.

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