Oxygen reduction reaction catalyst with axial nitrogen coordination iron monatomic structure and low-temperature preparation method thereof

Abstract

The invention discloses an oxygen reduction reaction catalyst with an axial nitrogen coordination iron monatomic structure and a low-temperature preparation method thereof.The low-temperature preparation method comprises the steps that benzoic anhydride derivatives, iron salt, other non-iron metal salts, a nitrogen source, a carbon source and ammonium salt are added into a mortar and ground and mixed uniformly, and a precursor is obtained; putting the obtained precursor into a muffle furnace, carrying out heat treatment at 140-250 DEG C for 0.5-3 hours, and taking out and cooling after the heat treatment is finished; grinding into powder, washing the powder, and drying in vacuum to obtain the oxygen reduction reaction catalyst with the axial nitrogen coordination iron monatomic structure. The catalyst has excellent ORR performance in an alkaline medium, and the catalytic activity of the catalyst is superior to that of a commercial Pt / C catalyst; and the catalyst has good stability, and is suitable for being used as a catalyst in proton exchange membrane fuel cells and metal-air cells. The catalyst disclosed by the invention is prepared by adopting a low-temperature solid-phase synthesis method, reaction in a protective atmosphere is not needed, and high-temperature heat treatment is also not needed, so that the preparation method is simple, and the energy consumption is remarkably reduced.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of electrocatalysis, and particularly relates to an oxygen reduction reaction catalyst with an axial nitrogen-coordinated iron monatomic structure and a low-temperature preparation method thereof. BACKGROUND

[0002] The oxygen reduction reaction (ORR) is a key reaction in proton exchange membrane fuel cells (PEMFCs) and metal-air batteries, and the reaction kinetics is slow, usually requiring a noble metal catalyst (such as Pt / C) to accelerate. However, the high cost and limited resources of the noble metal catalyst limit its large-scale application. Therefore, developing high-efficiency, low-cost non-noble metal catalysts has become a research hotspot.

[0003] Monatomic catalysts (SACs) have attracted extensive attention due to their high activity, high selectivity and high atomic utilization, and in particular, iron monatomic catalysts (Fe-SACs) are considered to be an ideal choice to replace noble metal catalysts due to their abundant active sites and low cost. However, the traditional FeN4 active site in Fe-SACs still has problems such as poor adsorption performance of intermediates and easy occurrence of demetallization in the ORR process, which will simultaneously reduce the catalytic activity and stability.

[0004] Introducing additional axial nitrogen ligands to the central Fe monatomic atom is expected to regulate its electronic structure and geometric structure, and at the same time improve the catalytic performance and stability, so as to obtain a more excellent ORR catalyst. To realize this design, a key bottleneck in the synthesis process needs to be solved first. In the synthesis of carbon-based ORR catalysts, existing methods usually rely on harsh conditions, such as pyrolysis under an inert atmosphere at a temperature above 600 DEG C.

[0005] For example, Chinese patent document CN 116031415 A (application number 202211621782.1) discloses a preparation method of a nitrogen-doped graphene supported iron monatomic catalyst, which comprises the following steps: selecting carbon nitride, tannic acid, an iron source, 4-diethylamino-salicylaldehyde, an ethanol solution and deionized water; dispersing the carbon nitride in the deionized water through ultrasonic waves; adding the iron source to the deionized water containing the tannic acid; adding the 4-diethylamino-salicylaldehyde to the ethanol solution; mixing solution one, solution two and solution three and stirring to obtain a uniformly dispersed solution; performing hydrothermal treatment on the uniformly dispersed solution through a hydrothermal kettle; performing centrifugal drying on the solution after hydrothermal treatment to obtain a Fe / C3N4@TA-salicylaldehyde precursor; and performing high-temperature calcination on the Fe / C3N4@TA-salicylaldehyde precursor in a nitrogen atmosphere to obtain the nitrogen-doped graphene supported iron monatomic catalyst.

[0006] For example, Chinese patent document CN 113054210 A (application number 202110302758.0) discloses an oxygen reduction iron-nitrided tetracarbonyl@single-atom iron and nitrogen co-doped amorphous carbon-carbon black composite catalyst, and a preparation method thereof. The preparation method comprises the following steps: mixing iron salt, nitrogen-containing organic small molecule compound and carbon black, placing them in a protective atmosphere, and then performing two-stage calcination treatment to obtain the catalyst.

[0007] The above synthesis method needs to be carried out in an inert atmosphere to prevent oxidation of metal atoms and the carrier carbon. At the same time, these catalysts often need to use high-temperature heat treatment (usually more than 800℃) in the preparation process. Since the metastable axial nitrogen coordination structure is highly sensitive to synthesis conditions, severe reaction environment can easily lead to irreversible agglomeration of active components, serious corrosion of carbon carriers, and random formation of active sites. These problems directly conflict with the precise preparation requirements of the target axial nitrogen coordination structure, making it a challenge to develop a scalable, mild and selective synthesis strategy for constructing axial nitrogen coordination M-N5 active sites. SUMMARY

[0008] The technical problem to be solved by the present application is to provide an oxygen reduction reaction catalyst with an axial nitrogen coordination iron monatomic structure, which has a simple synthesis method, low energy consumption, high activity and stability, and a low-temperature preparation method thereof.

[0009] The technical solution for realizing the first object of the present application is a low-temperature preparation method of an oxygen reduction reaction catalyst with an axial nitrogen coordination iron monatomic structure, comprising the following steps: ① 0.1-1 parts of benzoic anhydride derivative, 0.1-1 parts of iron salt, 0-1 parts of other non-iron metal salt, 2-10 parts of nitrogen source, 1-10 parts of carbon source and 0-0.5 parts of ammonium salt are weighed according to the weight parts, and then mixed and ground uniformly in a mortar to obtain a precursor.

[0010] ② The precursor obtained in step ① is placed in a muffle furnace and heated at a heating rate of 1-20℃ / min to 140-250℃, and then heat-treated at this temperature for 0.5-3 h. After heat treatment, the solid is taken out and cooled.

[0011] ③ The cooled solid in step ② is ground into powder, and the powder is post-treated and vacuum dried to obtain the oxygen reduction reaction catalyst with an axial nitrogen coordination iron monatomic structure.

[0012] The benzoic anhydride derivative is at least one of phthalic anhydride, pyromellitic anhydride, 2,3-naphthalene dicarboxylic anhydride and benzene hexacarboxylic anhydride.

[0013] The iron salt is at least one of ferric chloride, ferric sulfate, ferric nitrate and ferric acetate.

[0014] The other non-ferrous metal salts are at least one of the chlorides, sulfates, nitrates, and acetates of metals such as cobalt, nickel, copper, zinc, manganese, zirconium, and neodymium.

[0015] The nitrogen source is at least one of cyanamide, melamine, and urea.

[0016] The carbon source is at least one of the following: surface-modified or unmodified carbon powder, carbon nanotubes, graphene, graphene oxide, and mesoporous carbon.

[0017] The ammonium salt is at least one of ammonium molybdate, ammonium tungstate, and ammonium phosphomolybdate.

[0018] In step ②, the precursor obtained in step ① is placed in a muffle furnace and heat-treated at 180~250℃ for 1~3 h.

[0019] In step ③, during the post-treatment of the powder, it is first soaked in hydrochloric acid solution, and then cleaned with deionized water and anhydrous ethanol.

[0020] The technical solution to achieve the second objective of this invention is an oxygen reduction reaction catalyst with an axial nitrogen-coordinated iron single-atom structure prepared by the above preparation method.

[0021] This invention has positive effects: (1) The catalyst of the present invention has excellent ORR performance in alkaline media and its catalytic activity is better than that of commercial Pt / C catalysts; and the catalyst of the present invention has good stability and is suitable for use as a catalyst in proton exchange membrane fuel cells and metal-air batteries.

[0022] (2) The catalyst of the present invention is prepared by low temperature solid phase synthesis method, which does not require reaction in protective atmosphere or high temperature heat treatment. Therefore, the preparation method is simple and significantly reduces energy consumption. Attached Figure Description

[0023] Figure 1 This is an aberration-corrected transmission electron microscope image of the axial nitrogen-coordinated iron single-atom catalyst prepared in Example 1.

[0024] Figure 2 The XANES fitting results are for the axial nitrogen-coordinated iron single-atom catalyst prepared in Example 1.

[0025] Figure 3 The linear sweep voltammetry curve of the axial nitrogen-coordinated iron single-atom catalyst prepared in Example 1 of this invention in 0.1 M KOH solution is shown.

[0026] Figure 4 The linear sweep voltammetry curve of the axial nitrogen-coordinated iron single-atom catalyst prepared in Example 2 of this invention in 0.1 M KOH solution is shown.

[0027] Figure 5 The linear sweep voltammetry curve of the axial nitrogen-coordinated iron single-atom catalyst prepared in Example 3 of this invention in 0.1 M KOH solution is shown.

[0028] Figure 6 The results show the stability test results of the axial nitrogen-coordinated iron single-atom catalyst prepared in Example 1. Detailed Implementation

[0029] The following describes some of the possible embodiments of the present invention, intended to provide a basic understanding of the invention, and is not intended to identify the key or decisive elements of the invention or limit the scope of protection. It is readily understood that, based on the technical solutions of the present invention, those skilled in the art can propose other interchangeable implementations without altering the essential spirit of the invention. Therefore, the following specific embodiments are merely illustrative examples of the technical solutions of the present invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solutions of the present invention.

[0030] The oxygen reduction reaction catalyst of the present invention having an axially nitrogen-coordinated iron single-atom structure is prepared according to the following steps: ① Add 0.1-1 parts by weight of benzoic anhydride derivative, 0.1-1 parts of iron salt, 0-1 parts of other non-ferrous metal salt, 2-10 parts of nitrogen source, 1-10 parts of carbon source and 0-0.5 parts of ammonium salt to a mortar and grind and mix evenly to obtain the precursor.

[0031] The benzoic anhydride derivative is at least one of phthalic anhydride (PA), pyromellitic anhydride (PMDA), 2,3-naphthalenedicarboxylic anhydride, and benzohexacarboxylic trihydride.

[0032] The iron salt is at least one of ferric chloride, ferric sulfate, ferric nitrate, and ferric acetate.

[0033] Other non-ferrous metal salts are at least one of the chlorides, sulfates, nitrates, and acetates of metals such as cobalt, nickel, copper, zinc, manganese, zirconium, and neodymium.

[0034] The nitrogen source is at least one of cyanamide, melamine, urea.

[0035] The carbon source is at least one of the following: surface-modified or unmodified carbon powder, carbon nanotubes, graphene, graphene oxide, and mesoporous carbon.

[0036] The ammonium salt is at least one of ammonium molybdate, ammonium tungstate, and ammonium phosphomolybdate.

[0037] ② Place the precursor obtained in step ① in a muffle furnace and heat it to 140~250℃ at a heating rate of 1℃~20 ℃ / min. Heat treat it at this temperature for 0.5~3 h. After the heat treatment is completed, remove it and let it cool naturally to room temperature (10℃~35℃).

[0038] ③ Grind the solid cooled in step ② into powder, soak it in hydrochloric acid solution for 20-60 minutes, wash it with deionized water and anhydrous ethanol, and then vacuum dry it to obtain the oxygen reduction reaction catalyst with an axial nitrogen-coordinated iron single-atom structure.

[0039] Specific preparation examples are as follows.

[0040] (Example 1) The oxygen reduction catalyst with an axially nitrogen-coordinated iron single-atom structure in this embodiment was prepared according to the following steps: ① Add 0.65g phthalic anhydride, 0.125g pyromellitic anhydride, 0.2g ferrous chloride, 9.47g urea, 1g carbon powder and 0.05g ammonium molybdate to a mortar and grind and mix evenly to obtain the precursor.

[0041] ② Place the precursor obtained in step ① in a muffle furnace and heat it to 180℃ at a heating rate of 10℃ / min. Maintain the temperature at this temperature for 1 hour. After the heat treatment is completed, remove the product and allow it to cool naturally to room temperature.

[0042] ③ Grind the solid cooled in step ② into powder, add it to 2M hydrochloric acid solution, sonicate for 30 minutes, and then wash it three times each with deionized water and anhydrous ethanol. After drying the powder, obtain the catalyst sample.

[0043] In the post-processing, the amounts of hydrochloric acid solution, deionized water, and anhydrous ethanol were sufficient to completely submerge the powder, and vacuum drying yielded the oxygen reduction reaction catalyst with an axially nitrogen-coordinated iron single-atom structure.

[0044] Aberration-corrected transmission electron microscopy (TEM) image of the oxygen reduction reaction catalyst with an axially nitrogen-coordinated iron single-atom structure prepared in this embodiment is shown below. Figure 1 ,Depend on Figure 1 It is evident that the catalyst contains numerous white bright spots belonging to axially nitrogen-coordinated iron single atoms, indicating that iron exists in the catalyst in the form of single atoms.

[0045] Depend on Figure 2 It can be seen that the peak positions of the characteristic peaks in the XANES fitting results of the catalyst are consistent with the characteristic peak positions of the theoretically simulated FeN5 structure, indicating that iron exists in the catalyst as the FeN5 structure, which is an oxygen reduction reaction catalyst with an axially nitrogen-coordinated iron single-atom structure.

[0046] (Example 2) The preparation method of the oxygen reduction reaction catalyst with an axially nitrogen-coordinated iron single-atom structure in this embodiment is the same as that in Example 1, except that: In step ②, the precursor obtained in step ① is placed in a muffle furnace and heated to 210°C at a heating rate of 10°C / min, and reacted at this temperature for 3 hours. After the heat treatment is completed, it is removed and allowed to cool naturally to room temperature.

[0047] (Example 3) The preparation method of the oxygen reduction reaction catalyst with an axially nitrogen-coordinated iron single-atom structure in this embodiment is the same as that in Example 1, except that: In step ②, the precursor obtained in step ① is placed in a muffle furnace and heated to 240°C at a heating rate of 10°C / min, and reacted at this temperature for 3 hours. After the heat treatment is completed, it is removed and allowed to cool naturally to room temperature.

[0048] (Examples 4 to 10) The formulations of the oxygen reduction reaction catalysts with axial nitrogen-coordinated iron single-atom structures in Examples 4 to 10 are shown in the table below. The raw materials with axial nitrogen-coordinated iron single-atom structures were prepared by weighing the raw materials according to the formulations in the table below and following the method in Example 1.

[0049] (Experimental Example 1: Electrocatalytic ORR Catalytic Performance Test) Experimental group: catalyst prepared in Example 1, catalyst prepared in Example 2, and catalyst prepared in Example 3.

[0050] Control group: Commercial Pt / C catalyst, purchased from Johnson Metthey, catalog number JM hispec 3000 20%.

[0051] Experimental methods: A three-electrode system was adopted, with a graphite carbon rod as the counter electrode, Hg / HgO as the reference electrode, and a glassy carbon electrode modified with the catalyst as the working electrode.

[0052] In a 0.1 M KOH solution at 20 °C, at 10 mV s -1 The linear sweep voltammetry curve of the catalyst in Example 1 is shown below. Figure 3 The linear sweep voltammetry curve of the catalyst in Example 2 is shown below. Figure 4 The linear sweep voltammetry curve of the catalyst in Example 3 is shown in [reference needed]. Figure 5 The test results show that the catalyst of the present invention has excellent ORR performance in alkaline media.

[0053] (Experimental Example 2: Electrocatalytic ORR Stability Test) The stability of the catalyst in Example 1 was tested in an oxygen-saturated 0.1 M KOH solution at a potential of 0.7 V. The results are shown in [Figure number missing]. Figure 6 .

[0054] The test results show that the material's performance did not show significant degradation after 50,000 seconds of continuous testing, indicating that the material has very good stability.

[0055] The catalysts of Examples 2 and 3 also showed no significant performance degradation after continuous testing for 50,000 s.

Claims

1. A low-temperature preparation method of an oxygen reduction reaction catalyst having an axial nitrogen-coordinated iron monatomic structure, characterized by The preparation method comprises the following steps: 1) 0.1-1 parts of benzoic anhydride derivative, 0.1-1 parts of iron salt, 0-1 parts of other non-iron metal salt, 2-10 parts of nitrogen source, 1-10 parts of carbon source and 0-0.5 parts of ammonium salt are weighed according to weight parts, and are added into a mortar, and are ground to be uniformly mixed to obtain a precursor; 2) the precursor obtained in step 1) is placed in a muffle furnace, and is heated at a heating rate of 1-20 ℃ / min to 140-250 ℃, and is heat-treated at the temperature for 0.5-3 h, and after the heat treatment is finished, the solid is taken out and cooled; 3) the solid cooled in step 2) is ground into powder, and the powder is post-treated and vacuum dried to obtain the oxygen reduction reaction catalyst with the axial nitrogen-coordinated iron monatomic structure.

2. The method of claim 1, wherein the catalyst is prepared at a temperature of 0°C or lower. The benzoic anhydride derivative is at least one of phthalic anhydride, pyromellitic anhydride, 2,3-naphthalene dicarboxylic anhydride and benzene hexacarboxylic anhydride.

3. The method of claim 1, wherein the catalyst is prepared at a temperature of 0°C or lower. The iron salt is at least one of ferric chloride, ferric sulfate, ferric nitrate and ferric acetate.

4. The method of claim 1, wherein the catalyst is prepared at a temperature of 0°C or lower. The other non-iron metal salt is at least one of chlorides, sulfates, nitrates and acetates of cobalt, nickel, copper, zinc, manganese, zirconium and neodymium.

5. The method for preparing the oxygen reduction reaction catalyst with an axially nitrogen-coordinated iron single-atom structure according to claim 1, characterized in that: The nitrogen source is at least one of cyanamide, double cyanamide, melamine and urea.

6. The method of claim 1, wherein the catalyst is prepared at a temperature of 0°C or lower. The carbon source is at least one of surface-modified or unmodified carbon powder, carbon nanotube, graphene, oxidized graphite and mesoporous carbon.

7. The method of claim 1, wherein the catalyst is prepared at a temperature of about - 20°C to about 20°C. The ammonium salt is at least one of ammonium molybdate, ammonium tungstate and ammonium phosphomolybdate.

8. The process for the low-temperature preparation of an oxygen reduction reaction catalyst having an axial nitrogen-coordinated iron monatomic structure according to claim 1, characterized by: In step 2), the precursor obtained in step 1) is placed in a muffle furnace, and is heat-treated at 180-250 ℃ for 1-3 h.

9. The method of claim 1, wherein the catalyst is prepared at a temperature of about 0°C to about 100°C. In step 3), when the powder is post-treated, the powder is first soaked in a hydrochloric acid solution, and then is cleaned with deionized water and anhydrous ethanol.

10. An oxygen reduction reaction catalyst with the axial nitrogen-coordinated iron monatomic structure, which is prepared by the preparation method in any one of claims 1-9.

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