Preparation method of nitrogen-rich porous sub-micron carbon sphere anchored iron monatomic cathode catalyst for zinc-air battery

Abstract

The application discloses a preparation method of a nitrogen-rich porous sub-micron carbon sphere anchored iron monatomic cathode catalyst for a zinc-air battery, and comprises the following steps: step 1, preparing a Fe / Zn-Ad CSS precursor by one-pot method through a metal and a nitrogen source; and step 2, heating the precursor obtained in step 1 to 900-1000 DEG C in an inert gas environment and keeping the temperature for 1-3 hours to obtain the FeSA / N-PSCS catalyst. The catalyst material prepared by the application exhibits excellent ORR catalytic performance when applied in a zinc-air battery.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrocatalytic materials and new clean energy, and particularly relates to a preparation method of a nitrogen-rich porous sub-micron carbon sphere anchored iron monatomic cathode catalyst for a zinc-air battery. BACKGROUND

[0002] Electrochemical storage and conversion devices, such as zinc-air batteries (ZABs), are a promising clean energy and environmental remediation technology due to their high durability, low cost, high energy density, excellent safety and environmental friendliness. However, the zinc-air battery involves a kinetically slow oxygen reduction reaction (ORR), which seriously hinders the application of the zinc-air battery. Platinum-based catalysts with high activity have been considered as a highly efficient ORR electrocatalyst. However, they are too high in cost, poor in stability, and limited in reserves. Therefore, great efforts have been made to obtain high-performance non-noble metal catalysts. Previously, nitrogen-doped carbon-supported metal monatomic catalysts (M-N-C SACs) have been considered as the most promising substitutes for Pt-based catalysts due to the largest atomic utilization, clear and adjustable electronic structure, and superior intrinsic catalytic performance.

[0003] The performance of M-N-C SACs is mainly derived from a large number of atomically dispersed M-N x active sites. At present, the high surface area and defects of nitrogen-doped hierarchical porous carbon are considered to be an ideal carrier for loading monatomic atoms. M-N-C SACs are generally obtained by processes such as template method, acid washing and gas treatment (N2, H2). Such preparation methods not only have a complicated process and produce chemical waste, but also easily destroy the structure of M-N x active sites. Therefore, it is still a great challenge to achieve precise regulation of monatomic atoms by a template-free one-step method. In recent years, metal-organic frameworks (MOFs) have been widely considered as an ideal precursor for constructing nitrogen-doped porous carbon-based monatomic catalysts due to a large number of micropores, high surface area and periodic metal-ligand binding sites. However, the inevitable nitrogen volatilization of MOFs in the pyrolysis process seriously limits the formation of M-N x active sites, thereby affecting the electrocatalytic activity. SUMMARY

[0004] In order to overcome the above technical problems, the purpose of the present application is to provide a preparation method of a nitrogen-rich porous sub-micron carbon sphere anchored iron monatomic cathode catalyst for a zinc-air battery, which exhibits excellent ORR catalytic performance when the catalyst material prepared by the method is applied to a zinc-air battery.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is:

[0006] The preparation method of nitrogen-rich porous submicron carbon sphere anchored iron single-atom cathode catalyst for zinc-air batteries includes the following steps;

[0007] Step 1: Prepare the Fe / Zn-Ad CSS precursor by reacting the metal and nitrogen source in a one-pot process;

[0008] Step 2: The precursor obtained in Step 1 is heated to 900-1000℃ in an inert gas environment and kept at that temperature for 1-3 hours to obtain the FeSA / N-PSCS catalyst.

[0009] Preferably, the metals in step 1 are zinc nitrate hexahydrate and ferrous acetate.

[0010] Preferably, the nitrogen source in step 1 is adenine biomolecule with a nitrogen content of 51.8%. This is to increase the intrinsic nitrogen content in the precursor and avoid the need for additional nitrogen source supplementation.

[0011] Preferably, the Fe / Zn-Ad CSS precursor in step 1 is prepared by the following steps:

[0012] a) Dissolve zinc nitrate hexahydrate and ferrous acetate in DMF in a certain proportion to obtain solution A, which is then set aside.

[0013] b) At 140°C, adenine is dissolved in DMF to form a clear solution B;

[0014] c) Pour solution A into solution B, mix and stir for 2-6 hours, let it cool to room temperature, then wash and dry to obtain the final product.

[0015] In the above preparation of the Fe / Zn-Ad CSS precursor, the molar ratio of zinc nitrate hexahydrate to ferrous acetate is 1:0.001–0.05. This is because both iron and zinc ions can interact with adenine through competitive coordination, leading to a certain proportion of iron ion sites being replaced by zinc ion sites. The increased number of Zn ion sites acts as "spacers," expanding the spatial distance between adjacent Fe atoms and preventing uncontrolled aggregation of metal clusters during pyrolysis.

[0016] Preferably, the molar ratio of the metal to the nitrogen source in step 1 is 1:1 to 3. This ratio is intended to ensure complete coordination between the metal ions and the nitrogen source.

[0017] Preferably, the inert gas in step 2 is argon.

[0018] Preferably, the heating rate in step 2 is 3–5 °C / min. This is to ensure a more stable phase transition.

[0019] The FeSA / N-PSCS catalyst prepared by the above method is used in zinc-air batteries.

[0020] In this invention, the Fe / Zn-Ad CSS precursor is a uniformly sized microsphere, and the catalyst obtained after high-temperature carbonization is a uniformly sized submicron sphere with a hierarchical porous structure. Fe is distributed in single-atom form on the submicron sphere. Furthermore, according to energy-dispersive X-ray spectroscopy, the nitrogen atom loading in FeSA / N-PSCS is 14.81 at.%. The catalyst exhibits excellent ORR performance in 0.1 M KOH, and its application in zinc-air batteries results in a power density superior to that of zinc-air batteries assembled based on noble metals.

[0021] The beneficial effects of this invention are:

[0022] 1. Using adenine, a biomolecule with high nitrogen content, as a ligand effectively maintains the stability of the carbon skeleton during pyrolysis. Importantly, adenine has an extremely high nitrogen content (51.8%) and a large number of metal coordination sites, which makes it easier to coordinate and self-assemble with metal ions. Furthermore, the nitrogen content in the pyrolysis products is as high as 14.81 at.%, which is higher than most existing technologies, further improving the catalytic activity of the catalyst.

[0023] 2. By utilizing the physical confinement effect of Zn ion sites, the movement of Fe atoms is restricted, the aggregation of Fe atoms is prevented, and the dispersion of Fe atoms is enhanced, thereby improving the stability of the catalyst and the utilization rate of Fe atoms.

[0024] 3. The preparation method of the invention is simple to operate, avoids processes such as acid washing and gas treatment (N2, H2), and does not require an external nitrogen source.

[0025] 4. As a cathode material for zinc-air batteries, this invention exhibits excellent performance. Attached Figure Description

[0026] Figure 1 This is a transmission electron microscope (TEM) image of Fe / Zn-Ad CSS-1 obtained in Example 1 of the present invention.

[0027] Figure 2 This is a scanning electron microscope (SEM) image of the FeSA / N-PSCS-1 catalyst prepared in Example 1 of this invention.

[0028] Figure 3 This is a high-angle annular dark-field scanning transmission electron microscope (HADDF-STEM) image of the FeSA / N-PSCS-1 catalyst prepared in Example 1 of this invention, with double spherical aberration correction.

[0029] Figure 4The images show the X-ray diffraction (XRD) patterns of the FeSA / N-PSCS-1 catalyst prepared in Example 1 and the Fe / N-PSCS catalyst prepared in Comparative Example 2.

[0030] Figure 5 Linear sweep scalar (LSV) plots of the FeSA / N-PSCS-1 catalyst prepared in Example 1 of this invention, the N-PSCS catalyst prepared in Comparative Example 1, the Fe / N-PSCS catalyst prepared in Comparative Example 2, and a commercial Pt / C catalyst.

[0031] Figure 6 The chronoamperometry (it) measurement curves are shown for the FeSA / N-PSCS-1 catalyst prepared in Example 1 of this invention and commercial Pt / C.

[0032] Figure 7 The discharge polarization curves and power density curves of the zinc-air battery assembled with the FeSA / N-PSCS-1 catalyst prepared in Example 1 of this invention and commercial Pt / C+RuO2 as cathode materials are shown. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings.

[0034] Example 1

[0035] Step 1: Dissolve 3.996 mmol of zinc nitrate hexahydrate and 0.004 mmol of ferrous acetate in DMF to prepare solution A; at 140 °C, dissolve 8 mmol of adenine in DMF to form a transparent solution B. Pour solution A into solution B, mix and stir for 5 hours, and allow it to cool to room temperature. Then wash and dry to obtain the Fe / Zn-Ad CSS-1 precursor.

[0036] like Figure 1 As shown, the Fe / Zn-Ad CSS-1 precursor has a spherical structure with a smooth surface and uniform size of approximately 1 μm.

[0037] Step 2: Heat the Fe / Zn-Ad CSS-1 precursor to 1000℃ at 5℃ / min and hold for 2 hours to obtain the FeSA / N-PSCS-1 catalyst.

[0038] like Figure 2 As shown, FeSA / N-PSCS-1 maintains a spherical structure with a diameter of approximately 700 nm, and its surface becomes rougher after carbonization.

[0039] Figure 3 The image shows a HAADF-STEM image of the FeSA / N-PSCS-1 catalyst, indicating that Fe is uniformly distributed in atomic form (shown by white circles) on submicron spheres.

[0040] Comparative Example 1

[0041] Step 1: Dissolve 4 mmol of zinc nitrate hexahydrate in DMF to prepare solution A; at 140 °C, dissolve 8 mmol of adenine in DMF to form a transparent solution B. Pour solution A into solution B, mix and stir for 5 hours, let it cool to room temperature, then wash and dry to obtain the Zn-Ad CSS precursor.

[0042] Step 2: Heat the Zn-Ad CSS precursor to 1000℃ at 5℃ / min and hold for 2 hours to obtain the control sample N-PSCS catalyst without Fe single atoms.

[0043] Comparative Example 2

[0044] Step 1: Dissolve 4 mmol of ferrous acetate in DMF to prepare solution A; at 140 °C, dissolve 8 mmol of adenine in DMF to form a transparent solution B. Pour solution A into solution B, mix and stir for 5 hours, let it cool to room temperature, then wash and dry to obtain the Fe-Ad CSS precursor.

[0045] Step 2: Heat the Fe-Ad CSS precursor to 1000℃ at 5℃ / min and hold for 2 hours to obtain the control sample Fe / N-PSCS catalyst.

[0046] Figure 4 The X-ray diffraction patterns of the catalyst samples in Example 1 and Comparative Example 2 show that the Fe / N-PSCS sample in Comparative Example 2 contains signals corresponding to metallic iron, indicating that iron exists in the form of particles. However, no iron particle signals are found in FeSA / N-PSCS-1, consistent with other characterization results. This demonstrates that the physical confinement of Zn ion sites, restricting the movement of Fe atoms and preventing their aggregation, is crucial for the generation of Fe single-atom catalysts.

[0047] Example 2

[0048] Step 1: Dissolve 3.996 mmol of zinc nitrate hexahydrate and 0.004 mmol of ferrous acetate in DMF to prepare solution A; at 140 °C, dissolve 8 mmol of adenine in DMF to form a transparent solution B. Pour solution A into solution B, mix and stir for 5 hours, and allow it to cool to room temperature. Then wash and dry to obtain the Fe / Zn-Ad CSS-2 precursor.

[0049] Step 2: Heat the Fe / Zn-Ad CSS-2 precursor to 900℃ at 5℃ / min and hold for 2 hours to obtain the FeSA / N-PSCS-2 catalyst.

[0050] Example 3

[0051] Step 1: Dissolve 3.994 mmol of zinc nitrate hexahydrate and 0.006 mmol of ferrous acetate in DMF to prepare solution A; at 140 °C, dissolve 8 mmol of adenine in DMF to form a transparent solution B. Pour solution A into solution B, mix and stir for 5 hours, and allow it to cool to room temperature. Then wash and dry to obtain the Fe / Zn-Ad CSS-0.75 precursor.

[0052] Step 2: Heat the Fe / Zn-Ad CSS-0.75 precursor to 1000℃ at 5℃ / min and hold for 2 hours to obtain the FeSA / N-PSCS-0.75 catalyst.

[0053] Example 4

[0054] Step 1: Dissolve 3.992 mmol of zinc nitrate hexahydrate and 0.008 mmol of ferrous acetate in DMF to prepare solution A; at 140 °C, dissolve 8 mmol of adenine in DMF to form a transparent solution B. Pour solution A into solution B, mix and stir for 5 hours, and allow it to cool to room temperature. Then wash and dry to obtain the Fe / Zn-Ad CSS-0.5 precursor.

[0055] Step 2: Heat the Fe / Zn-Ad CSS-0.5 precursor to 1000℃ at 5℃ / min and hold for 2 hours to obtain the FeSA / N-PSCS-0.5 catalyst.

[0056] To demonstrate the beneficial effects of this invention, electrochemical tests were conducted on an electrochemical workstation using a three-electrode system. The test method is as follows: FeSA / N-PSCS-1 prepared in Example 1 was dispersed in an ethanol / Nafion mixture (volume ratio 49:1), followed by ultrasonic treatment until a uniform catalyst suspension was formed. Then, 10 μL of the catalyst suspension was dropped onto the working electrode (area 0.247 cm²). 2 The reference electrode is an Ag / AgCl electrode, and the counter electrode is a platinum wire. The electrolyte used for ORR and stability tests is an oxygen-saturated 0.1M potassium hydroxide solution.

[0057] Figure 5Electrocatalytic oxygen reduction performance graphs of the FeSA / N-PSCS-1 catalyst prepared in Example 1, the N-PSCS catalyst prepared in Comparative Example 1, the Fe / N-PSCS catalyst prepared in Comparative Example 2, and the commercial Pt / C catalyst are shown. The performance comparison shows that the catalyst prepared in this invention exhibits the highest half-wave potential and superior oxygen reduction catalytic activity compared to Comparative Example 1 (which does not contain Fe single atoms), Comparative Example 2 (which contains Fe particles), and the commercial Pt / C catalyst.

[0058] Figure 6 The graphs show the stability test results of FeSA / N-PSCS-1 catalyst and commercial Pt / C catalyst. It can be seen that after 10 hours of continuous operation, FeSA / N-PSCS-1 catalyst exhibits very slow degradation and current retention rate of over 97%, which is higher than that of commercial Pt / C catalyst.

[0059] Further Fe SA The FeSA / N-PSCS-1 catalyst was assembled into a zinc-air battery and tested. Carbon paper loaded with FeSA / N-PSCS-1 (2 mg catalyst loaded in 1 cm⁻¹) was used. 2 Carbon paper (any suitable material) was used as the air cathode, a polished Zn sheet as the anode, and 6.0 M KOH and 0.2 M zinc acetate as the electrolyte. A commercial Pt / C+RuO2 mixture at a mass ratio of 1:1 was used as a control sample and tested under the same conditions.

[0060] Figure 7 The discharge polarization curves and corresponding power density curves of the zinc-air battery device assembled with FeSA / N-PSCS-1 catalyst and commercial Pt / C+RuO2 show that the maximum power density of the battery assembled with FeSA / N-PSCS-1 catalyst is 164.5 mW cm⁻¹. -2 This is higher than the 117.7 mW cm⁻¹ of the Pt / C+RuO₂ catalyst. -2 .

[0061] To illustrate how high nitrogen doping of the FeSA / N-PSCS-1 catalyst enhances its catalytic activity, it was compared with existing nitrogen-doped carbon-based single-atom catalysts. As shown in Table 1, the FeSA / N-PSCS-1 catalyst exhibits superior catalytic activity compared to most existing technologies, demonstrating that using this adenine biomolecule with high nitrogen content as a ligand is highly beneficial for improving catalyst activity.

[0062] Table 1

[0063]

[0064]

Claims

1. A method for preparing a nitrogen-rich porous submicron carbon sphere-anchored iron single-atom cathode catalyst for zinc-air batteries, characterized in that, Includes the following steps; Step 1: Prepare the Fe / Zn-Ad CSS precursor by reacting the metal and nitrogen source in a one-pot process; Step 2: The precursor obtained in Step 1 is heated to 900~1000 ℃ in an inert gas environment and kept at that temperature for 1~3 hours to obtain the FeSA / N-PSCS catalyst. The Fe / Zn-Ad CSS-1 precursor has a spherical structure, a smooth surface, and uniform size of approximately 1 μm. FeSA / N-PSCS-1 maintains a spherical structure with a diameter of approximately 700 nm; HAADF-STEM images of the FeSA / N-PSCS-1 catalyst show that Fe is uniformly distributed in atomic form on submicron spheres; The metals in step 1 are zinc nitrate hexahydrate and ferrous acetate; The nitrogen source in step 1 is adenine biomolecule with a nitrogen content of 51.8%.

2. The method for preparing the nitrogen-rich porous submicron carbon sphere-anchored iron single-atom cathode catalyst for zinc-air batteries according to claim 1, characterized in that, The Fe / Zn-Ad CSS precursor in step 1 is prepared by the following steps: a) Dissolve zinc nitrate hexahydrate and ferrous acetate in DMF in a certain proportion to obtain solution A, which is then set aside. b) At 140 °C, adenine was dissolved in DMF to form a clear solution B; c) Pour solution A into solution B, mix and stir for 2-6 hours, let it cool to room temperature, then wash and dry to obtain the final product.

3. The method for preparing the nitrogen-rich porous submicron carbon sphere-anchored iron single-atom cathode catalyst for zinc-air batteries according to claim 2, characterized in that, In the above process for preparing Fe / Zn-Ad CSS precursor, the molar ratio of zinc nitrate hexahydrate to ferrous acetate is 1:0.001~0.

05.

4. The method for preparing the nitrogen-rich porous submicron carbon sphere-anchored iron single-atom cathode catalyst for zinc-air batteries according to claim 1, characterized in that, The molar ratio of the metal to the nitrogen source in step 1 is 1:1~3.

5. The method for preparing the nitrogen-rich porous submicron carbon sphere-anchored iron single-atom cathode catalyst for zinc-air batteries according to claim 1, characterized in that, The inert gas in step 2 is argon.

6. The method for preparing the nitrogen-rich porous submicron carbon sphere-anchored iron single-atom cathode catalyst for zinc-air batteries according to claim 1, characterized in that, The heating rate in step 2 is 3~5 ℃ / min.

7. The FeSA / N-PSCS catalyst prepared by the method according to any one of claims 1-6, characterized in that, The FeSA / N-PSCS catalyst is used in zinc-air batteries.

8. The FeSA / N-PSCS catalyst prepared by the method according to any one of claims 1-6, characterized in that, The Fe / Zn-Ad CSS precursor is a uniformly sized microsphere. After high-temperature carbonization, the resulting catalyst is a uniformly sized submicron sphere with a hierarchical porous structure, and Fe is distributed in the form of single atoms on the submicron sphere. Meanwhile, according to energy-dispersive X-ray spectroscopy, the nitrogen atom loading in FeSA / N-PSCS is 14.81 at.%. The catalyst exhibits excellent ORR performance in 0.1 M KOH. When applied to zinc-air batteries, its power density is superior to that of zinc-air batteries based on noble metal assemblies.

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