Preparation and application of template-assisted derived electrocatalyst

Abstract

The invention belongs to the technical field of polymer electrolyte membrane fuel cells, and provides preparation and application of a template-assisted derived electrocatalyst, metal macrocyclic compound self-assembly is performed on the surface of a metal organic framework material to form an ordered aggregate, and then high-temperature heat treatment is performed on the composite to prepare the corresponding electrocatalyst. The electrocatalyst prepared by the method does not form metal-based particles after being subjected to high-temperature heat treatment, so that metal aggregation is effectively avoided, the metal-nitrogen-carbon oxygen reduction active site density is improved, and the electrocatalyst has better oxygen reduction activity and stability in acidic and alkaline electrolytes. The preparation process of the catalyst adopted in the method does not need any acid treatment, the raw materials are rich in source, resources are saved, the cost is reduced, meanwhile, the preparation process of the non-noble metal electrocatalyst is simplified, and the prepared electrocatalyst has high oxygen reduction activity and durability and can be used in the field of polymer electrolyte membrane fuel cells.

Description

Technical Field

[0001] This invention belongs to the field of polymer electrolyte membrane fuel cell technology, specifically relating to the preparation and application of a template-assisted derivatized electrocatalyst. Background Technology

[0002] Polymer electrolyte membrane fuel cells (MEFCs) are efficient and clean energy conversion devices with significant application value in the field of new energy battery vehicles. Currently, the oxygen reduction reaction at the cathode of hydrogen fuel cells still relies on precious metal platinum group electrocatalysts. However, the limited resources, low global annual production, and high price of platinum restrict its large-scale production. Therefore, researching low-cost, highly active, and long-life non-precious metal electrocatalysts to promote the large-scale commercialization of fuel cells is of great significance. Macrocyclic metal compounds, due to their high density of M-N4 active centers, are often used in combination with other template materials to prepare efficient non-precious metal electrocatalysts. However, traditional synthesis methods often involve the disordered mixing of various carbon, nitrogen, and metal sources, using trial and error to find the optimal synthesis conditions. This not only consumes a large amount of resources but also fails to fundamentally improve the density of oxygen reduction active sites.

[0003] In summary, the preparation methods for non-precious metal electrocatalysts still need to be developed from the perspectives of precursor design and increasing the density of oxygen reduction active sites. Summary of the Invention

[0004] This invention addresses the shortcomings of existing technologies by providing a template-assisted derivatization method for preparing electrocatalysts. The method involves the self-assembly of macrocyclic metal compounds on the surface of a metal-organic framework material to form ordered aggregates, followed by high-temperature heat treatment of these aggregates to obtain the corresponding electrocatalyst. The electrocatalyst prepared by this method does not form metal-based particles after high-temperature heat treatment, effectively avoiding metal aggregation and increasing the density of metal-nitrogen-carbon-oxygen reduction active sites. It exhibits good oxygen reduction activity and stability in both acidic and alkaline electrolytes. This catalyst preparation process requires no acid treatment, utilizes abundant raw materials, saves resources, reduces costs, and simplifies the preparation process of non-precious metal electrocatalysts.

[0005] The technical solution of this invention: A template-assisted derivatization method for preparing electrocatalysts comprises the following steps: 1) Self-assembly of metal macrocyclic compounds: A metal-organic framework material was dispersed in deionized water, and then a cationic surfactant was added and ultrasonically homogenized as solution A; a negatively charged metal macrocyclic compound was dissolved in deionized water and ultrasonically homogenized as solution B; at 25 °C, solution B was poured into solution A under constant stirring, stirred for a period of time, and then the precipitate was filtered and dried to obtain the self-assembled metal macrocyclic compound and metal-organic framework composite precursor, denoted as MOF@Por; 2) Preparation of electrocatalysts derived from self-assembled macrocyclic metal compounds and metal-organic framework composite precursors: The MOF@Por composite precursor was heat-treated at 600-900℃ for 2h in an inert atmosphere to obtain the template-assisted derivatized electrocatalyst MOF@Por-H.

[0006] The cationic surfactant is one of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, dioctadecyldimethylammonium chloride, and benzalkonium bromide.

[0007] The negatively charged macrocyclic metal compound is one of the following: tetrasodium tetrasulfonate iron phthalocyanine, tetrasodium tetrasulfonate cobalt phthalocyanine, tetrasodium tetrasulfonate manganese phthalocyanine, tetrasodium tetrasulfonate copper phthalocyanine, iron phthalocyanine (III)-(III)-(III)-4,4′,4′′,4′′′-monosodium salt hydrate of a mixture of tetrasulfonic acid and oxygen, meso-tetra(4-benzenesulfonic acid)porphyrin iron, meso-tetra(4-benzenesulfonic acid)porphyrin cobalt, meso-tetra(4-benzenesulfonic acid)porphyrin manganese, meso-tetra(4-benzenesulfonic acid) phthalocyanine iron, meso-tetra(4-benzenesulfonic acid) phthalocyanine cobalt, and meso-tetra(4-benzenesulfonic acid) phthalocyanine manganese.

[0008] The metal-organic framework material includes one of MOF-5, MIL-101, ZIF-8, and ZIF-67.

[0009] In step 1), the concentration of the surfactant is 0.1-0.5 mM.

[0010] In step 1), the concentration of the macrocyclic metal compound is 0.1-0.5 mM.

[0011] In step 1), the mass of the metal-organic framework material is 20-100 mg.

[0012] In step 1), the volumes of A and B are equal.

[0013] In step 1), the stirring time is more than 12 hours.

[0014] Template-assisted derivation of electrocatalysts for use in polymer membrane fuel cells.

[0015] The beneficial effects of this invention are: (1) The preparation method is simple, the raw materials are abundant, and the preparation cost is low; (2) By utilizing the attraction between positive and negative charges and introducing a soft template cationic surfactant, the dispersion of metal macrocyclic compounds can be designed and controlled at the molecular level, and the density of oxygen reduction active sites on the surface of the metal-organic framework template can be adjusted. The self-assembled metal macrocyclic compound aggregates prepared by the template-assisted method have highly ordered nanostructures. The assemblies inherit the characteristics of single molecules and also have unique electronic and energy transfer characteristics, as well as high chemical stability. (3) The assembly between the metal macrocyclic compound and the metal-organic framework may effectively promote the increase of the bond strength of the metal-nitrogen bond, improve the thermal stability of the self-assembled aggregate, avoid the formation of metal-based nanoparticles after high temperature heat treatment, effectively improve the density of metal-nitrogen-carbon oxygen reduction active sites, and be beneficial to the improvement of oxygen reduction activity and stability. Attached Figure Description

[0016] Figure 1 (a) is a transmission electron microscope image of the electrocatalyst before pyrolysis in Example 1 of the present invention; Figure 1 (b) is a transmission electron microscope image of the electrocatalyst in Example 1 of the present invention; Figure 2 (a) is the oxygen reduction polarization curve of the electrocatalyst and commercial 20% Pt / C in acidic electrolyte in Example 1 of the present invention; Figure 2 (b) is a graph showing the oxygen reduction polarization curves of the electrocatalyst in Example 1 of the present invention and commercial 20% Pt / C in alkaline electrolyte; Figure 3 (a) is a graph showing the oxygen reduction polarization curves of the electrocatalyst in Comparative Example 1 and the electrocatalyst in Example 1 in alkaline electrolyte; Figure 3 (b) is a graph showing the oxygen reduction polarization curves of the electrocatalyst in Comparative Example 1 and the electrocatalyst in Example 1 in an acidic electrolyte. Detailed Implementation

[0017] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions. Example 1

[0018] At 25 °C, 50 mg ZIF-8 was dispersed in 50 ml of deionized water, and 14 mg dodecyltrimethylammonium bromide was added and ultrasonically homogenized to obtain catalyst A. 50 ml of 0.1 mM meso-tetra(4-benzenesulfonic acid)porphyrin iron aqueous solution was poured into catalyst A and stirred continuously for 12 h. The precipitate was then filtered, dried, and heat-treated at 900 °C under an argon atmosphere for 2 h to obtain the final electrocatalyst MOF-PorFe-900. Example 2

[0019] At 25 °C, 50 mg ZIF-67 was dispersed in 50 ml of deionized water, and 14 mg dodecyltrimethylammonium bromide was added and ultrasonically homogenized to obtain catalyst A. 50 ml of 0.1 mM meso-tetra(4-benzenesulfonic acid)porphyrin cobalt aqueous solution was poured into catalyst A and stirred continuously for 12 h. The precipitate was then filtered, dried, and heat-treated at 800 °C under an argon atmosphere for 2 h to obtain the final electrocatalyst MOF-PorCo-800. Example 3

[0020] At 25 °C, 20 mg MOF-5 was dispersed in 50 ml of deionized water, and 9 mg of cetyltrimethylammonium bromide was added and sonicated to obtain catalyst A. 50 ml of 0.1 mM meso-tetra(4-benzenesulfonic acid)porphyrin manganese aqueous solution was poured into catalyst A and stirred continuously for 12 h. The precipitate was then filtered, dried, and heat-treated at 900 °C under an argon atmosphere for 2 h to obtain the final electrocatalyst MOF-PorMn-900.

[0021] Comparative Example 1: (Different stirring times) At 25 °C, 50 mg ZIF-8 was dispersed in 50 ml of deionized water, and then 14 mg dodecyltrimethylammonium bromide was added and ultrasonically homogenized to obtain catalyst A. 50 ml of 0.1 mM meso-tetra(4-benzenesulfonic acid)porphyrin cobalt aqueous solution was poured into catalyst A and stirred continuously for 6 h. The precipitate was then filtered, dried, and heat-treated at 900 °C under an argon atmosphere for 2 h to obtain the final electrocatalyst MOF-PorCo-900.

[0022] Comparative Example 2: (Different surfactant concentrations) At 25 °C, 100 mg MIL-01 was dispersed in 50 ml of deionized water, and then 30 mg of dodecyltrimethylammonium bromide was added and ultrasonically homogenized to obtain catalyst A. 50 ml of 0.1 mM tetrasodium tetrasulfonate copper phthalocyanine aqueous solution was poured into catalyst A and stirred continuously for 12 h. The precipitate was then filtered, dried, and heat-treated at 800 °C under an argon atmosphere for 2 h to obtain the final electrocatalyst MOF-PorCu-900.

Claims

1. A method for preparing a template-assisted derivatized electrocatalyst, characterized in that, The steps are as follows: 1) Self-assembly of metal macrocyclic compounds: A metal-organic framework material was dispersed in deionized water, and then a cationic surfactant was added and ultrasonically homogenized as solution A; a negatively charged metal macrocyclic compound was dissolved in deionized water and ultrasonically homogenized as solution B; at 25 °C, solution B was poured into solution A under constant stirring, stirred for a period of time, and then the precipitate was filtered and dried to obtain the self-assembled metal macrocyclic compound and metal-organic framework composite precursor, denoted as MOF@Por; 2) Preparation of electrocatalysts derived from self-assembled macrocyclic metal compounds and metal-organic framework composite precursors: The MOF@Por composite precursor was heat-treated at 600-900℃ for 2h in an inert atmosphere to obtain the template-assisted derivatized electrocatalyst MOF@Por-H.

2. The preparation method according to claim 1, characterized in that, The cationic surfactant is one of dodecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, dioctadecyldimethylammonium chloride, and benzalkonium bromide.

3. The preparation method according to claim 1 or 2, characterized in that, The negatively charged macrocyclic metal compound is one of the following: tetrasodium tetrasulfonate iron phthalocyanine, tetrasodium tetrasulfonate cobalt phthalocyanine, tetrasodium tetrasulfonate manganese phthalocyanine, tetrasodium tetrasulfonate copper phthalocyanine, iron phthalocyanine (III)-(III)-(III)-4,4′,4′′,4′′′-monosodium salt hydrate of a mixture of tetrasulfonic acid and oxygen, meso-tetra(4-benzenesulfonic acid)porphyrin iron, meso-tetra(4-benzenesulfonic acid)porphyrin cobalt, meso-tetra(4-benzenesulfonic acid)porphyrin manganese, meso-tetra(4-benzenesulfonic acid) phthalocyanine iron, meso-tetra(4-benzenesulfonic acid) phthalocyanine cobalt, and meso-tetra(4-benzenesulfonic acid) phthalocyanine manganese.

4. The preparation method according to claim 3, characterized in that, The metal-organic framework material includes one of MOF-5, MIL-101, ZIF-8, and ZIF-67.

5. The preparation method according to claim 1, 2 or 3, characterized in that, The concentration of the surfactant is 0.1-0.5 mM.

6. The preparation method according to claim 1 or 5, characterized in that, The concentration of the macrocyclic metal compound is 0.1-0.5 mM.

7. The preparation method according to claim 1, characterized in that, The mass of the metal-organic framework material is 20-100 mg.

8. The preparation method according to claim 5, characterized in that, The volumes of A and B are equal.

9. The preparation method according to claim 7, characterized in that, The stirring time is 12 hours or more.

10. Electrocatalysts derived using template-assisted method for use in polymer membrane fuel cells.

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