Triatomic FeM1M2 catalyst as well as preparation method and application thereof

Abstract

The invention aims at the field of energy electro-catalysis, and provides a three-atom FeM1M2 catalyst and a preparation method and application thereof, M is Co, Ni, Cu, Zn, Mn, Cr, V, Zr, W, Co and Re atoms, a zinc-based imidazole framework is used for packaging a FeM1M2 cluster, a core-shell structure is formed by coating a polymer, then high-temperature annealing is carried out, and nitrogen coordination FeM1M2 three atoms are obtained and anchored in an N-doped hollow carbon nanocage (FeM1M2L / NC). According to the method, the catalyst with the FeM1M2 active site is controllably synthesized, the FeM1M2 active site effectively adjusts the adsorption mode of * OOH on FeM1M2 and the electronic structure of FeM1M2, the optimal adsorption / desorption behavior of FeM1M2 and an oxygen intermediate is promoted, and the three-atom FeM1M2 has good oxygen reduction performance. The method effectively inhibits aggregation of metal atoms, synthesizes the catalyst with definite sites, is applied to oxygen reduction reaction and fuel cells and zinc-air cells, improves the oxygen reduction reaction of the catalyst and the performance of the zinc-air cells, and is expected to replace the current commercial noble metal Pt-based catalyst.

Description

Technical Field

[0001] The present invention relates to the field of energy electrocatalysis, including a synthesis method of nitrogen-coordinated FeM1M2 triatomic atoms anchored on an N-doped hollow carbon nanocage catalyst and its applications in the oxygen reduction reaction, fuel cells, and zinc-air batteries. Background Art

[0002] For environmentally friendly energy conversion technologies such as fuel cells and metal-air batteries, the development of efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) catalysts is crucial. Transition metal single atoms anchored in a nitrogen-doped carbon matrix (referred to as M-N / C SACs) show great promise in various industrial applications, including environmental protection and renewable energy conversion and storage. This is due to their unique electronic structure, high catalytic activity, maximum atomic efficiency, and their being ideal models for exploring reaction mechanisms. Among all potential SACs, Fe SACs show the highest activity in ORR and are expected to be potential substitutes for Pt-based catalysts in fuel cells and zinc-air batteries. However, in practical applications, the durability of Fe SACs is relatively poor. On the one hand, when ORR is incomplete, hydrogen peroxide (H2O2) is generated. H2O2 undergoes a Fenton reaction with the leached Fe ions to generate hydroxyl (·OH) and superoxide (·OOH) radicals. These radicals have strong oxidation properties and will further damage the structure of the catalyst, thereby reducing the stability of the catalyst. On the other hand, the excessive adsorption strength of intermediate products on Fe sites hinders their desorption, thus affecting the d-band center position of the electrocatalyst and limiting its practical application.

[0003] Triatomic catalysts not only have a high metal atom loading but also can achieve superior electronic structure modulation through the interaction of multiple metal atoms. However, due to the unique physical and chemical properties of metal atoms, synthesizing triatomic catalysts at the single-atom level remains a major challenge. Therefore, a strategy for designing an asymmetrically coordinated multi-metal atom catalyst with controllable, stable, and highly active sites is crucial. The Chinese patent application with the publication number CN116196928A discloses a "graphdiyne-based dual-atom copper-cobalt catalyst and its preparation method and application". The synthesis method is to disperse graphdiyne nanosheets and copper salt / cobalt salt in a first dispersion liquid to obtain a first mixed liquid, followed by drying and instantaneous calcination to obtain a first mixture. Subsequently, the first mixture and cobalt salt / copper salt are dispersed in a second dispersion liquid to obtain a second mixed liquid, and then dried and instantaneously calcined to obtain the graphdiyne-based dual-atom copper-cobalt catalyst. The preparation process of this catalyst has a certain degree of randomness. In addition, there has been no report on the controllable synthesis of triatomic FeM1M2 catalysts and their applications in ORR, fuel cells, and zinc-air batteries. Summary of the Invention

[0004] Based on the problems faced by current synthesis techniques, we designed a shrink-wrap thermal printing technique to synthesize triatomic FeM1M2 catalysts. This technique can effectively inhibit atomic migration and precisely synthesize target active sites. The obtained triatomic FeM1M2 / NC catalyst can effectively catalyze ORR, and when assembled as an air electrode catalyst into a zinc-air battery, it exhibits excellent stability.

[0005] In this invention, FeM1M2 / NC was successfully prepared by a stress-constrained thermal printing method. This method achieved precise structural control of triatoms through two key steps. First, FeM1M2 / NC was synthesized using FeM1M2L (M = Co, Ni, Cu, Zn, Mn, Cr, V, Zr, W, Ce, and Re) cluster ligands as precursors. Second, by encapsulating the FeM1M2L structure in ZIF-8 (ZIF-8@FeM1M2L), ZIF-8@FeM1M2L largely retained its metal framework during the subsequent pyrolysis process. Organic molecular aggregates were in-situ polymerized on the surface of the ZIF-8@FeM1M2L precursor to prepare organic molecular aggregate@ZIF-8@FeM1M2L with a coaxial structure. Finally, during the annealing process, the carbon layer derived from the first carbonized Polymer had a strong interfacial interaction with the ZIF-8 precursor, destroying the ZIF-8 core and generating an outward contraction stress, gradually forming a hollow carbon structure. At the same time, FeM1M2 was in-situ generated on the hollow carbon nanocage. Using FeM1M2L as the precursor, FeM1M2 / NC-1, FeM1M2 / NC-2, FeM1M2 / NC-3, and FeM1M2 / NC-4 were obtained by the same method. The obtained triatomic FeM1M2 / NC-1 catalyst can effectively catalyze ORR, and when assembled as an air electrode catalyst into a zinc-air battery, it exhibits excellent stability.

[0006] The technical solution is as follows:

[0007] 1), First, prepare the FeM1M2L precursor: Fe(NO3)3·9H2O (8 g) and metal (M = Co, Ni, Cu, Zn, Mn, Cr, V, Zr, W, Ce, and Re) nitrates (0.1 mol) were completely dissolved in 70 mL of H2O. Sodium salt (42 g) was also dissolved in 70 mL of H2O. The sodium salt solution was added to the nitrate solution that had been filtered and stirred. After the solution was stirred for 24 h, the precipitate was filtered and washed with a small amount of cold H2O and ethoxyacetic acid. The product was air-dried for 48 hours;

[0008] 2), 10 mg of FeM1M2L was dissolved in 20 mL of methanol and stirred for 30 minutes to form solution A. Meanwhile, 1.18 g of 2-methylimidazole was dissolved in 20 mL of methanol and stirred for 30 minutes to obtain solution B. In addition, 1.13 g of zinc nitrate hexahydrate was dissolved in 20 mL of methanol and stirred for 30 minutes to produce solution C. Solution A and solution B were mixed and stirred for 10 minutes to obtain solution D. Finally, solution D was mixed with solution C and stirred for 8 hours. The resulting powder was collected by centrifugation, washed three times with methanol, and dried in vacuo at 60 °C. The final product was named ZIF-8@FeM1M2L;

[0009] 3), 0.1 g of ZIF-8@FeM1M2L powder and 0.01 g of Polymer were added to 50 mL of alkaline buffer solution and stirred magnetically for 8 h. The precipitate was collected by centrifugation and dried at 60 °C to obtain a black sample named Polymer@ZIF-8@FeM1M2L;

[0010] 4), The Polymer@ZIF-8@FeM1M2L powder was placed in a porcelain boat and pyrolyzed at a heating rate of 10 °C min -1 −1 in an inert gas atmosphere at 700–1500 °C for 2 h to obtain FeM1M2 / NC.

[0011] The present invention also discloses the application of the trimetallic FeM1M2 catalyst in the oxygen reduction reaction and zinc-air batteries. The beneficial effects of the present invention are as follows: The present invention uses the synthesized trinuclear FeM1M2L cluster precursor as a precursor to controllably synthesize the target catalyst, which greatly improves its performance in the oxygen reduction reaction. The preparation process is simple, and the prepared trimetallic FeM1M2 / NC-1 catalyst has a half-wave potential of E 1 / 2 = 0.971 in the oxygen reduction reaction. The zinc-air battery assembled with it as the air cathode exhibits excellent stability. This has important practical significance for the wide application of zinc-air battery energy storage devices in actual production and life. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will describe the drawings required for use in the description of the embodiments or the prior art;

[0013] Figure 1 is a flow chart of the method for forming trimetallic FeM1M2 / NC in the embodiments of the present invention;

[0014] Figure 2 is the X-ray diffraction patterns of Comparative Examples 1, 2, 3 and Example 1;

[0015] Figure 3 is the transmission electron microscope image of Example 1;

[0016] Figure 4 is the spherical aberration corrected transmission electron microscope image of Example 1;

[0017] Figure 5 is the linear sweep voltammogram of the catalysts prepared in Example 1 and Comparative Examples 1, 2, and 3;

[0018] Figure 6 is the stability comparison curve between Example 1 and commercial 20 wt% Pt / C; Detailed implementation manners

[0019] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to examples. It should be understood that the specific examples described herein are only used to explain the present invention and are not used to limit the present invention.

[0020] The following describes the specific implementation manners of the present invention so as to make the objectives, technical solutions and advantages of the present invention clearer. The present invention can be implemented in various different forms and is not limited to the examples described herein.

[0021] Comparative Example 1

[0022] 1), First, prepare the Fe3L precursor: Fe(NO3)3·9H2O (8 g) and Fe(NO3)2·9H2O (0.1 mol) are completely dissolved in 70 mL of H2O. Sodium salt (42 g) is also dissolved in 70 mL of H2O. The sodium salt solution is added to the nitrate solution which is stirred after filtration. After the solution is stirred for 24 h, the precipitate is filtered and washed with a small amount of cold H2O and ethoxyacetic acid. The product is air-dried for 48 hours;

[0023] 2), 10 mg of Fe3L is dissolved in 20 mL of methanol and stirred for 30 minutes to form Solution A. At the same time, 1.18 g of 2-methylimidazole is dissolved in 20 mL of methanol and stirred for 30 minutes to obtain Solution B. In addition, 1.13 g of zinc nitrate hexahydrate is dissolved in 20 mL of methanol and stirred for 30 minutes to produce Solution C. Solution A and Solution B are mixed and stirred for 10 minutes to obtain Solution D. Finally, Solution D is mixed with Solution C and stirred for 8 hours. The obtained powder is collected by centrifugation, washed three times with methanol, and dried in vacuum at 60 °C. The final product is named ZIF-8@Fe3L;

[0024] 3), 0.1 g of ZIF-8@Fe3L powder and 0.01 Polymer are added to 50 mL of alkaline buffer solution and magnetically stirred for 8 h. The precipitate is collected by centrifugation and dried at 60 °C to obtain a black sample named Polymer@ZIF-8@Fe3L;

[0025] 4), The Polymer@ZIF-8@Fe3L powders were respectively placed in porcelain boats and pyrolyzed at a heating rate of 10 °C / min in an inert gas atmosphere at 1200 °C for 2 hours to obtain Fe3 / NC. -1 The heating rate of 10 °C / min was used for pyrolysis for 2 hours to obtain Fe3 / NC.

[0026] Comparative Example 2

[0027] 1), First, prepare the FeNiZnL precursor: Fe(NO3)3·9H2O (4 g), Zn(NO3)2·9H2O (0.1 mol) and Ni(NO3)2·9H2O (0.1 mol) were completely dissolved in 70 mL of H2O. The sodium salt (42 g) was also dissolved in 70 mL of H2O. The sodium salt solution was added to the nitrate solution that had been filtered and stirred. After the solution was stirred for 24 h, the precipitate was filtered and washed with a small amount of cold H2O and ethoxyacetic acid. The product was air-dried for 48 hours;

[0028] 2), 10 mg of FeNiZnL was dissolved in 20 mL of methanol and stirred for 30 minutes to form Solution A. Meanwhile, 1.18 g of 2-methylimidazole was dissolved in 20 mL of methanol and stirred for 30 minutes to obtain Solution B. In addition, 1.13 g of zinc nitrate hexahydrate was dissolved in 20 mL of methanol and stirred for 30 minutes to produce Solution C. Solution A and Solution B were mixed and stirred for 10 minutes to obtain Solution D. Finally, Solution D was mixed with Solution C and stirred for 8 hours. The resulting powder was collected by centrifugation, washed three times with methanol, and dried in vacuo at 60 °C. The final product was named ZIF-8@Fe2NiL;

[0029] 3), 0.1 g of ZIF-8@FeNiZnL powder and 0.01 g of Polymer were added to 50 mL of alkaline buffer solution and magnetically stirred for 8 h. The precipitate was collected by centrifugation and dried at 60 °C to obtain a black sample named Polymer@ZIF-8@FeNiZnL;

[0030] 4), The Polymer@ZIF-8@FeNiZnL powders were respectively placed in porcelain boats and pyrolyzed at a heating rate of 10 °C / min in an N2 atmosphere at 1000 °C for 2 hours to obtain FeNiZn / NC. -1 The heating rate of 10 °C / min was used for pyrolysis for 2 hours to obtain FeNiZn / NC.

[0031] Comparative Example 3

[0032] 1), First, prepare the FeMnCoL precursor: Fe(NO3)3·9H2O (4 g), Mn(NO3)2·9H2O (0.1 mol) and Co(NO3)2·9H2O (0.1 mol) are completely dissolved in 70 mL of H2O. Sodium salt (42 g) is also dissolved in 70 mL of H2O. The sodium salt solution is added to the nitrate solution that has been filtered and stirred. After the solution is stirred for 24 h, the precipitate is filtered and washed with a small amount of cold H2O and ethoxyacetic acid. The product is air-dried for 48 hours;

[0033] 2), 10 mg of FeMnCoL is dissolved in 20 mL of methanol and stirred for 30 minutes to form solution A. Meanwhile, 1.18 g of 2-methylimidazole is dissolved in 20 mL of methanol and stirred for 30 minutes to obtain solution B. In addition, 1.13 g of zinc nitrate hexahydrate is dissolved in 20 mL of methanol and stirred for 30 minutes to produce solution C. Solution A and solution B are mixed and stirred for 10 minutes to obtain solution D. Finally, solution D is mixed with solution C and stirred for 8 hours. The resulting powder is collected by centrifugation, washed three times with methanol, and dried in vacuo at 60 °C. The final product is named ZIF-8@FeMnCoL;

[0034] 3), 0.1 g of ZIF-8@FeMnCoL powder and 0.01 g of Polymer are added to 50 mL of t basic buffer solution and magnetically stirred for 8 h. The precipitate is collected by centrifugation and dried at 60 °C to obtain a black sample, named Polymer@ZIF-8@FeMnCoL;

[0035] 4), The Polymer@ZIF-8@FeMnCoL powder is placed in a porcelain boat and pyrolyzed in an inert gas atmosphere at 1000 °C at a heating rate of 5 °C min -1 to obtain FeMnCo / NC.

[0036] Example 1

[0037] 1), First, prepare the FeCoFeL precursor: Fe(NO3)3·9H2O (8 g) and Co(NO3)2·9H2O (0.1 mol) are completely dissolved in 70 mL of H2O. Sodium salt (42 g) is also dissolved in 70 mL of H2O. The sodium salt solution is added to the nitrate solution that has been filtered and stirred. After the solution is stirred for 24 h, the precipitate is filtered and washed with a small amount of cold H2O and ethoxyacetic acid. The product is air-dried for 48 hours;

[0038] 2), 10 mg of FeCoFeL was dissolved in 20 mL of methanol and stirred for 30 minutes to form Solution A. Meanwhile, 1.18 g of 2-methylimidazole was dissolved in 20 mL of methanol and stirred for 30 minutes to obtain Solution B. In addition, 1.13 g of zinc nitrate hexahydrate was dissolved in 20 mL of methanol and stirred for 30 minutes to produce Solution C. Solution A and Solution B were mixed and stirred for 10 minutes to obtain Solution D. Finally, Solution D was mixed with Solution C and stirred for 8 hours. The resulting powder was collected by centrifugation, washed three times with methanol, and dried in vacuo at 60 °C. The final product was named ZIF-8@Fe2CoL;

[0039] 3), 0.1 g of ZIF-8@FeCoFeL powder and 0.01 g of Polymer were added to 50 mL of alkaline buffer and magnetically stirred for 8 h. The precipitate was collected by centrifugation and dried at 60 °C to obtain a black sample named Polymer@ZIF-8@FeCoFeL;

[0040] 4), The Polymer@ZIF-8@FeCoFeL powder was placed in a porcelain boat and pyrolyzed in an N2 atmosphere at 1500 °C at a heating rate of 10 °C min -1 for 2 hours to obtain FeCoFe / NC.

[0041] Structure detection

[0042] Figure 1 The synthesis process of the triatomic FeM1M2 / HNC catalyst was described.

[0043] Figure 2 The XRD results showed that there were no diffraction peaks of metal nanoparticles in the samples of Example 1 and Comparative Examples 1, 2, and 3, indicating that the above samples did not aggregate to form metal nanoparticles at high temperatures.

[0044] According to Figure 3 and Figure 4 the high-resolution transmission electron microscopy images and spherical aberration-corrected transmission electron microscopy images, there were no metal nanoparticles in the sample of Example 1 synthesized by the above method, and three atoms with a triangular shape could be seen in the spherical aberration-corrected transmission electron microscopy image, which were considered to be triatomic sites. This indicated that the method could effectively synthesize triatomic catalysts and effectively inhibit atomic aggregation.

[0045] Performance detection

[0046] To evaluate the catalytic activity of the samples of Comparative Examples 1, 2, 3 and Example 1 towards ORR, we conducted performance evaluations in 0.1 M KOH saturated with oxygen, and the specific steps are as follows: Mix 2 mg of the sample with 200 μL of 0.25 wt% Nafion solution and ultrasonicate for 1 h to obtain the resulting ink. Drop the ink onto a rotating ring-disk electrode and let it dry naturally to form a film to obtain the working electrode, where the reference electrode is Hg / Hg2Cl2 and the counter electrode is a platinum sheet.

[0047] The ORR activity of Example 1 is superior to that of the samples of Comparative Examples 1, 2, 3 and commercial 20 wt% Pt / C, and Example 1 exhibits excellent stability.

[0048] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. Preparation method of triatomic FeM1M2 catalyst, characterized in that It includes the following steps: 1). First, prepare the FeM1M2L precursor: 8 g of Fe(NO3)3·9H2O and 0.1 mol of metal nitrate are completely dissolved in 70 mL of H2O; 42 g of sodium salt is also dissolved in 70 mL of H2O; the sodium salt solution is added to the nitrate solution after filtration and stirring; after the solution is stirred for 24 h, the precipitate is filtered and washed with a small amount of cold H2O and ethanol; the product is air-dried for 48 hours; 2). 10 mg of FeM1M2L is dissolved in 20 mL of methanol and stirred for 30 minutes to form solution A; meanwhile, 1.18 g of dimethylimidazole is dissolved in 20 mL of methanol and stirred for 30 minutes to obtain solution B; in addition, 1.13 g of zinc nitrate hexahydrate is dissolved in 20 mL of methanol and stirred for 30 minutes to produce solution C; solution A and solution B are mixed and stirred for 10 minutes to obtain solution D; finally, solution D is mixed with solution C and stirred for 8 hours; the obtained powder is collected by centrifugation, washed three times with methanol, and dried in vacuum at 60 °C; the final product is named ZIF-8@FeM1M2L; 3). 0.1 g of ZIF-8@FeM1M2L powder and 0.01 g of organic polymer are added to 50 mL of alkaline buffer solution and magnetically stirred for 8 h, the precipitate is collected by centrifugation, and dried at 60 °C to obtain a black sample named Polymer@ZIF-8@FeM1M2L; 4), The Polymer@ZIF-8@FeM1M2L powder is respectively placed in a porcelain boat and annealed for 2 hours in an inert gas atmosphere at 700 - 1500 °C with a heating rate of 10 °C min -1 to obtain FeM1M2L / NC.

2. The preparation method of the three-atom FeM1M2 catalyst according to claim 1, wherein, In step 1), ensure the synthesis of the FeM1M2L precursor.

3. The preparation method of the three-atom FeM1M2 catalyst according to claim 1, wherein, In step 2), the FeM1M2L precursor, ZIF-8, and dimethylimidazole should be evenly dispersed in 20 mL of methanol respectively.

4. The preparation method of the three-atom FeM1M2 catalyst according to claim 1, characterized in that, Solution A and solution B are mixed and stirred for 10 minutes to obtain solution D; finally, solution D is mixed with solution C and stirred for 8 hours to achieve the precise encapsulation of FeM1M2L in ZIF-8.

5. The preparation method of the triatomic FeM1M2 catalyst according to claim 1, characterized in that, In step 3), 0.1 g of ZIF-8@FeM1M2L powder and 0.01 g of organic molecular aggregate are added to 50 mL of alkaline buffer solution and magnetically stirred for 8 h.

6. The preparation method of the three-atom FeM1M2 catalyst according to claim 1, characterized in that, In step 4), the Polymer@ZIF-8@FeM1M2L powder material needs to be calcined in an inert gas atmosphere.

7. The triatomic FeM1M2 catalyst prepared by the preparation method of the triatomic FeM1M2 catalyst according to any one of claims 1-6 is applied in the electrocatalytic oxygen reduction reaction, fuel cells, and zinc-air batteries.

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