A FeN x- (OH) y Composite nanomaterials, their preparation methods, and applications

Abstract

The application belongs to the field of energy storage and materials, and particularly relates to a FeN x -(OH) y Composite nanomaterial, preparation method and application. The application develops a method for etching carbon material by gamma rays, and directional manufacturing of defect sites on the surface of the carbon material and inducing formation of hydroxyl coordinated FeN x structure, and a carbon-based FeN x -(OH) y composite nanocatalyst is prepared. When the catalyst is loaded on a conductive substrate as an air positive electrode, a zinc sheet is used as an anode, and an alkaline seawater electrolyte is used to assemble a zinc-air battery, the discharge capacity of the battery can reach 797.3 mAh g ‑1 . The application prepares a carbon-based FeN x -(OH) y composite nanomaterial. The composite nanomaterial has excellent catalytic activity and seawater anti-interference characteristics, and when the composite nanomaterial is applied to a seawater-based zinc-air battery positive electrode, oxygen reduction reaction can be promoted to be efficiently performed, active component dissolution can be effectively inhibited, and the discharge specific capacity and stability of the battery can be further improved.

Description

Technical Field

[0001] This invention belongs to the field of chemical battery technology, specifically relating to a FeN x -(OH) y Composite nanomaterials, their preparation methods, and applications. Background Technology

[0002] The theoretical energy density of zinc-air batteries based on aqueous electrolytes is 1350 Wh / kg, but the actual energy density is only about 200-400 Wh / kg, which is insufficient to meet the requirements of high-energy-density and long-cycle-life batteries in emerging fields such as portable energy storage and marine equipment power supply. Therefore, high-performance zinc-air batteries with highly active oxygen reduction catalysts as the core, especially systems adapted to seawater-based electrolytes, have become the focus of researchers. Among various seawater-based zinc-air battery catalysts, Fe single atoms, with their unique electronic orbital arrangement, exhibit excellent orbital matching between their 3d orbital electrons and oxygen reduction reaction intermediates. This allows for precise control of the electron transfer efficiency and interfacial adsorption barrier, achieving a highly efficient improvement in oxygen reduction reaction kinetics (YRLiu et al.). Adv. Funct. Mater (2025, 35, 2422874). Compared to single-atom noble metals such as Pt and Ru, Fe single-atom resources are abundant and inexpensive, making them more suitable for industrial applications. Furthermore, compared to other transition metal single-atom metals such as Co and Ni, Fe's electronegativity and atomic radius are better suited to the interfacial electron transfer and reaction site bonding characteristics of the oxygen reduction reaction. This allows it to effectively lower the energy barrier of the rate-determining step in the catalytic process, making Fe single-atom catalysts considered one of the key materials for overcoming the performance bottleneck of seawater-based zinc-air batteries (X. Liu et al.). Appl. Catal. B Environ. Energy (2025, 365, 124990). However, the complex ionic environment of seawater can easily lead to blockage of catalyst active sites and dissolution of metal centers, resulting in rapid capacity decay and a decrease in coulombic efficiency (P. Rao et al.). Adv. Funct. Mater. 2024, 34, 2407121).

[0003] Therefore, how to construct Fe single-atom catalysts with high oxygen reduction activity, strong seawater anti-interference ability and stable interface structure through atomic-level control is crucial to promoting the practical application of seawater-based zinc-air batteries. Summary of the Invention

[0004] The purpose of this invention is to provide a FeN x -(OH) y Composite nanomaterials, their preparation methods, and applications. This catalyst, prepared via radiation, exhibits superior Tafel kinetics and excellent resistance to chloride ion corrosion, effectively improving the energy density and cycle stability of batteries.

[0005] The technical solution adopted in this invention is as follows: In a first aspect, the present invention provides a FeN x -(OH) y The preparation method of composite nanomaterials, where Fe represents iron, N represents nitrogen, O represents oxygen, and H represents hydrogen, and x and y represent the elemental ratios, specifically includes the following steps: S1. Raw material dispersion: The carbon material is dispersed in N,N-dimethylformamide solvent, and the macrocyclic iron complex is dispersed in DMF solvent, ensuring thorough dispersion; The macrocyclic iron complex is at least one of phthalocyanine iron, naphthalocyanine iron, anthracene phthalocyanine iron, iron porphyrin, tetramethoxyphenyl porphyrin iron, and tetracarboxyphenyl porphyrin iron. S2. Mixing reaction: Mix the two dispersions obtained in step S1 and disperse them thoroughly to obtain a mixed dispersion system; S3. Adding alkaline solution dropwise: Add alkaline solution dropwise to the mixed dispersion system obtained in step S2, controlling the molar ratio of iron atoms to hydroxide ions to be 1:1.1~1:1.3, and continue stirring; S4. Irradiation treatment: The reaction system obtained in step S3 is placed in a γ-ray or high-energy ray radiation field for irradiation treatment. S5. Post-processing: The product irradiated in step S4 is filtered, washed, and freeze-dried to obtain the FeN. x -(OH) y Composite nanomaterials.

[0006] Preferably, in step S1, the carbon material is at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers, carbon nanowires, graphene, fullerene, and carbon nanotube arrays.

[0007] Furthermore, in step S1, dispersion is achieved through ultrasonic treatment, wherein the power of the ultrasonic treatment is 80~100 W and the ultrasonic frequency is 30~50 kHz.

[0008] Preferably, in step S2, dispersion is carried out by stirring at a speed of 400-500 r / min and at room temperature.

[0009] Preferably, in step S3, the alkaline solution is either NaOH or KOH at a concentration of 0.02-0.5M, the dropping rate of the alkaline solution is 20-30 μL / min, and stirring is continued after the dropping is completed to ensure that the reaction proceeds fully.

[0010] Preferably, in step S4, the radiation source of the γ-rays is... 60Co source or high-energy ray radiation field, with an absorbed dose rate of 5-15 Gy / min and an absorbed dose of 0.2-5 kGy.

[0011] Preferably, in step S5, the washing process involves alternating between deionized water and ethanol for 3 to 5 times; the freeze-drying temperature is -40 to -60 ℃, the vacuum degree is no more than 20 Pa, and the drying time is 23 to 24 h.

[0012] Preferably, the irradiation conditions and raw material ratios are controlled such that 3 ≤ x < 6, 0 <y<2。

[0013] Secondly, the present invention provides FeN synthesized by the method described in the first aspect. x -(OH) y Composite nanomaterials.

[0014] Thirdly, the present invention provides FeN synthesized by the method described in the second aspect. x -(OH) y Application of composite nanomaterials as cathode catalyst materials for seawater-based zinc-air batteries.

[0015] Fourthly, the present invention provides a seawater-based zinc-air battery, wherein the battery is loaded with FeN x -(OH) y The composite nanomaterials use nickel foam carbon paper as the positive electrode, zinc foil as the negative electrode, and potassium hydroxide and zinc acetate dihydrate with seawater as the electrolyte to assemble the battery.

[0016] Preferably, the concentration of potassium hydroxide is 3-9 M and the concentration of zinc acetate dihydrate is 0.1-0.3 M.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes a precise method for controlling gamma-ray etching of a carbon substrate to directionally create defect sites on the substrate surface. Simultaneously, it induces the formation of stable coordination structures between hydroxyl groups and FeN4 in macrocyclic iron complexes, thereby preparing highly active FeN4. x -(OH) y Composite nanomaterials were developed and used as the core material for air cathodes in high-stability seawater-based zinc-air batteries. This catalyst demonstrates significant advantages and industrialization prospects in the field of seawater-based zinc-air batteries, specifically in the γ-ray etched FeN... x -(OH) yThe coordination structure optimizes electron configuration, significantly enhancing the catalytic activity and kinetic rate of the oxygen reduction reaction. It also strengthens the bonding between the active component and the carbon matrix, inhibits metal center dissolution, and improves the catalyst's resistance to interference and structural stability in high-salinity seawater environments. The modified carbon nanotubes retain high conductivity and a porous structure, accelerating charge transport and oxygen diffusion, synergistically improving battery performance. Applying this technology to seawater-based zinc-air batteries effectively alleviates electrode degradation in seawater environments, significantly improves the battery's discharge specific capacity and long-cycle stability, and provides key technological support for the practical application of this type of battery. Attached Figure Description

[0018] Figure 1 It is FeN 3.98 -OH 1.17 High-resolution transmission electron microscopy image.

[0019] Figure 2 It is FeN 3.98 -OH 1.17 Linear scan element distribution map.

[0020] The horizontal axis represents the length of the scan path in μm, and the vertical axis represents the characteristic signal intensity of the target element.

[0021] Figure 3 It is FeN 3.98 -OH 1.17 The fine structure fitting curve of extended X-ray absorption in R space.

[0022] The horizontal axis represents the apparent radial distance between the central absorbing atom and the surrounding coordinating atoms, in Å, and the vertical axis represents the magnitude of the EXAFS oscillation function χ(k) after Fourier transform.

[0023] Figure 4 It is FeN 3.98 -OH 1.17 X-ray photoelectron spectra of other samples.

[0024] The horizontal axis represents the binding energy in eV, and the vertical axis represents the photoelectron count intensity.

[0025] Figure 5 It is FeN 3.98 -OH 1.17 Linear voltammetric scan curves of other samples.

[0026] The horizontal axis represents voltage in volts (V), and the vertical axis represents current density in mA / cm². -2 .

[0027] Figure 6 It is FeN 3.98 -OH 1.17And the constant current discharge curves of other samples at different discharge current densities.

[0028] The horizontal axis represents time in seconds (s), and the vertical axis represents voltage in volts (V). Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0031] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0032] Example 1 A seawater-based zinc-air battery FeN 3.98 -OH 1.17 The preparation method of the composite nanomaterial is as follows: 1) 80 mg of single-walled carbon nanotubes (SWCNT) and 20 mg of iron phthalocyanine (FePc) were dispersed in 70 mL and 30 mL of DMF solution, respectively, and each was sonicated for 1 h. After sonication, the two dispersions were mixed and sonicated for another 1 h, followed by stirring for 48 h.

[0033] 2) Slowly add 414 μL of 0.1 M NaOH solution dropwise to the mixed dispersion system obtained in step 1), stirring continuously during the addition. After sealing the solution, send it into the cobalt source chamber for γ-irradiation at a dose rate of 10 Gy / min and an absorbed dose of 2 kGy.

[0034] 3) After the reaction system obtained in step 2) is irradiated with gamma rays in a cobalt source chamber, the product is filtered and washed several times alternately with distilled water and ethanol. After washing, it is freeze-dried to obtain the FeN sample. x -(OH) y Composite nanomaterials, where x=3.98, y=1.17.

[0035] Figure 1 FeN prepared in this embodiment 3.98 -OH 1.17Transmission electron microscopy (TEM) image of the composite nanomaterial. After gamma-ray irradiation, the graphitized carbon layer on the outer side of the single-walled carbon nanotubes is etched, forming a defect structure. This defect structure can facilitate subsequent anchoring of hydroxyl groups to coordinate FeN. x The active site provides ample spatial space, providing a structural basis for the stable loading of the active site. Figure 2 For the present invention FeN 3.98 -OH 1.17 Linear scanning elemental distribution map of the composite nanomaterial. The characteristic signal of oxygen can be clearly observed from the image, confirming that the hydroxyl group has been successfully introduced into the material system, becoming OH. - Coordination with Fe provides direct elemental evidence. Figure 3 FeN 3.98 -OH 1.17 Extended X-ray absorption fine structure fitting curve in R space. After γ-ray irradiation, the best fitting results indicate that FeN 3.98 -OH 1.17 The Fe atom in the sample is coordinated with approximately four N atoms and one O atom, confirming the successful construction of axial O atoms at isolated Fe sites. Figure 4 For the present invention FeN 3.98 -OH 1.17 X-ray photoelectron spectroscopy (XPS) of the composite nanomaterials, showing the Fe 2p3 / 2 orbital, reveals Fe² + The characteristic peak binding energy shifted from 723.21 eV to 722.27 eV (shift: -0.94 eV), Fe³ + The characteristic peak binding energy shifted from 727.19 eV to 726.82 eV (shift: -0.37 eV), both shifting towards lower binding energies, and Fe² + The offset is larger; at the same time, Fe³ + The relative content increased from 9.2% to 15.0%. These results confirm that γ-ray irradiation can successfully achieve OH... - Coordination with Fe. OH - As an electron donor, it injects electrons into the Fe d orbitals through coordinate bonds, increasing the electron cloud density at Fe sites. Macroscopically, this manifests as a general lower shift in the binding energy of the Fe characteristic peak, and the Fe³⁺ ionization energy increases. + More sensitive to electron injection, with a more significant shift. The fine XPS spectrum of the O 1s orbital shows that the area of ​​the Fe-OH characteristic peak (binding energy: 533.34 eV) increased from 13.8% in the unirradiated sample to 20.2%, without any shift in binding energy. This phenomenon stems from the effect of γ-irradiation on OH... - Dual activation of coordination reaction: On the one hand, the hydroxyl radicals generated by irradiation are FeN 3.98 -OH 1.17The formation of FeN provides sufficient precursors; on the other hand, irradiation lowers the coordination reaction energy barrier, allowing more FeN to form. x Sites converted to FeN x -OH y Active structure. Figure 5 It is FeN 3.98 -OH 1.17 Linear voltammetric scan curves of other samples show that the irradiation atmosphere significantly affects the etching degree of the carbon support, and thus affects the etching of OH groups. - The anchoring and regulation of Fe electronic valence states. FeN under three-electrode testing. 3.98 -OH 1.17 The ORR activity was the highest, with a half-wave potential of 0.911 V.

[0036] respectively loaded with FeN x -OH y The composite nanomaterial carbon paper foam nickel is used as the positive electrode, zinc foil is used as the negative electrode, and the electrolyte is 6M potassium hydroxide and 0.2M zinc acetate dihydrate in seawater. The battery is assembled and its electrochemical performance is tested using Shanghai Chenhua 760e and Blue Electric charging / discharging system.

[0037] Figure 6 For the FeN prepared in this invention 3.98 -OH 1.17 The galvanostatic discharge curves of a seawater-based zinc-air battery driven by composite nanomaterials at different discharge current densities are shown. The battery exhibits a stable discharge plateau at all current densities, with a peak discharge of 25 mA cm⁻¹. - ² The plateau potential reaches as high as 1.26 V, and when the current density increases to 100 mAcm², the potential increases further. - At 20°C, the plateau potential remained above 1.15 V, with a decay rate of only 8%, significantly better than commercial Pt / C catalysts (decay rate of 17%). This result confirms that FeN… 3.98 -OH 1.17 The hydroxyl coordination structure can effectively enhance ORR catalytic activity and resistance to seawater Cl. - It has excellent corrosion resistance and also mitigates polarization effects under high current density, giving the battery superior rate performance and discharge stability.

[0038] Example 2 The absorbed dose in step 2) of Example 1 was changed to 0.2 kGy, while other conditions remained the same as in Example 1, to obtain the FeN sample. x -(OH) y A composite nanomaterial with x=4.19, y=0.65 and a half-wave potential of 0.872 V.

[0039] Example 3 The absorbed dose in step 2) of Example 1 was changed to 0.5 kGy, while other conditions remained the same as in Example 1, to obtain the FeN sample. x -(OH) y A composite nanomaterial with x=4.12, y=0.78 and a half-wave potential of 0.877 V.

[0040] Example 4 The absorbed dose in step 2) of Example 1 was changed to 1 kGy, and other conditions remained the same as in Example 1, to obtain the FeN sample. x -(OH) y A composite nanomaterial with x=4.04, y=0.92 and a half-wave potential of 0.889 V.

[0041] Example 5 The absorbed dose in step 2) of Example 1 was changed to 1.5 kGy, while other conditions remained the same as in Example 1, to obtain the FeN sample. x -(OH) y A composite nanomaterial with x=4.02, y=1.05 and a half-wave potential of 0.903 V.

[0042] Example 6 The absorbed dose in step 2) of Example 1 was changed to 2.5 kGy, while other conditions remained the same as in Example 1, to obtain the FeN sample. x -(OH) y A composite nanomaterial with x=3.95, y=1.17 and a half-wave potential of 0.906 V.

[0043] Example 7 The absorbed dose in step 2) of Example 1 was changed to 3 kGy, and other conditions remained the same as in Example 1, to obtain the FeN sample. x -(OH) y A composite nanomaterial with x=3.91, y=1.29 and a half-wave potential of 0.898 V.

[0044] Example 8 The absorbed dose in step 2) of Example 1 was changed to 3.5 kGy, while other conditions remained the same as in Example 1, to obtain the FeN sample. x -(OH) y A composite nanomaterial with x=3.85, y=1.41 and a half-wave potential of 0.885 V.

[0045] Example 9 The absorbed dose in step 2) of Example 1 was changed to 4 kGy, and other conditions remained the same as in Example 1, to obtain the FeN sample. x -(OH) yA composite nanomaterial with x=3.81, y=1.53 and a half-wave potential of 0.874 V.

[0046] Example 10 The absorbed dose in step 2) of Example 1 was changed to 4.5 kGy, while other conditions remained the same as in Example 1, to obtain the FeN sample. x -(OH) y A composite nanomaterial with x=3.76, y=1.61 and a half-wave potential of 0.866 V.

[0047] Example 11 The absorbed dose in step 2) of Example 1 was changed to 5 kGy, and other conditions remained the same as in Example 1, to obtain the FeN sample. x -(OH) y A composite nanomaterial with x=3.72, y=1.69 and a half-wave potential of 0.861 V.

[0048] Example 12 Add 20 mL of isopropanol to the mixed dispersion system in step 2) of Example 1, and keep other conditions the same as in Example 1 to obtain sample FeN. x -(OH) y A composite nanomaterial with x=3.98, y=1.03 and a half-wave potential of 0.902 V.

[0049] Example 13 Nitrogen gas was introduced into the mixed dispersion system in step 2) of Example 1 until saturation, and other conditions were the same as in Example 1 to obtain the FeN sample. x -(OH) y A composite nanomaterial with x=3.98, y=0.75 and a half-wave potential of 0.891 V.

[0050] Example 14 Add 20 mL of isopropanol to the mixed dispersion system in step 2) of Example 1 and purge with nitrogen until saturated. Other conditions are the same as in Example 1 to obtain the FeN sample. x -(OH) y A composite nanomaterial with x=3.98, y=0.88 and a half-wave potential of 0.897V.

[0051] Example 15 In Example 1, step 1) was modified by changing the mass of FePc to 5 mg, and step 2) by changing the amount of NaOH added to 104 μL. Other conditions remained the same as in Example 1, resulting in a FeN sample. x -(OH) y A composite nanomaterial with x=4.12, y=1.17 and a half-wave potential of 0.902 V.

[0052] Example 16 In Example 1, step 1) was modified by changing the mass of FePc to 10 mg, and step 2) by changing the amount of NaOH added to 207 μL. Other conditions remained the same as in Example 1, resulting in a FeN sample. x -(OH) y A composite nanomaterial with x=4.05, y=1.17 and a half-wave potential of 0.898 V.

[0053] Example 17 In Example 1, step 2) was modified by changing the mass of FePc to 30 mg and the amount of NaOH added in step 2) to 621 μL, while keeping other conditions the same as in Example 1, to obtain the FeN sample. x -(OH) y A composite nanomaterial with x=3.93, y=1.17 and a half-wave potential of 0.891 V.

[0054] Example 18 In Example 1, step 2) was modified by changing the mass of FePc to 40 mg and the amount of NaOH added to 828 μL, while keeping other conditions the same as in Example 1, to obtain the FeN sample. x -(OH) y A composite nanomaterial with x=3.89, y=1.17 and a half-wave potential of 0.888 V.

[0055] Example 19 In Example 1, step 2) was modified by changing the mass of FePc to 50 mg and the amount of NaOH added in step 2) to 1035 μL, while keeping other conditions the same as in Example 1, to obtain sample FeN. x -(OH) y A composite nanomaterial with x=3.82, y=1.17 and a half-wave potential of 0.881 V.

[0056] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Those skilled in the art can make various modifications to the technical solutions in the embodiments based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations. Any modifications, variations, substitutions, etc., made based on the technical content disclosed in this invention are equivalent to equivalent implementations and should be included within the protection scope of this invention.

Claims

1. A FeN x -(OH) y The method for preparing composite nanomaterials is characterized by, Specifically, the steps include the following: S1. Raw material dispersion: The carbon material is dispersed in N,N-dimethylformamide solvent, and the macrocyclic iron complex is dispersed in DMF solvent, ensuring thorough dispersion; The macrocyclic iron complex is at least one of phthalocyanine iron, naphthalocyanine iron, anthracene phthalocyanine iron, iron porphyrin, tetramethoxyphenyl porphyrin iron, and tetracarboxyphenyl porphyrin iron. S2. Mixing reaction: Mix the two dispersions obtained in step S1 and disperse them thoroughly to obtain a mixed dispersion system; S3. Alkaline solution addition: Add an alkaline solution to the mixed dispersion system obtained in step S2, and control the molar ratio of iron atoms to hydroxide ions to be 1:1.1~1:1.

3. S4. Irradiation treatment: The reaction system obtained in step S3 is placed in a γ-ray or high-energy ray radiation field for irradiation treatment. S5. Post-processing: The product irradiated in step S4 is filtered, washed, and freeze-dried to obtain the FeN. x -(OH) y Composite nanomaterials.

2. The FeN according to claim 1 x -(OH) y The method for preparing composite nanomaterials is characterized by, In step S1, the carbon material is at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers, carbon nanowires, graphene, fullerene, and carbon nanotube arrays.

3. The FeN according to claim 2 x -(OH) y The method for preparing composite nanomaterials is characterized by, In step S1, dispersion is achieved through ultrasonic treatment, wherein the power of the ultrasonic treatment is 80~100 W and the ultrasonic frequency is 30~50 kHz.

4. The FeN according to claim 1 x -(OH) y The method for preparing composite nanomaterials is characterized by, In step S2, dispersion is carried out by stirring at a speed of 400-500 r / min and at room temperature.

5. The FeN according to claim 1 x -(OH) y The method for preparing composite nanomaterials is characterized by, In step S3, the alkaline solution is either NaOH or KOH at a concentration of 0.02-0.5M, and the dropping rate of the alkaline solution is 20-30 μL / min.

6. The FeN according to claim 1 x -(OH) y The method for preparing composite nanomaterials is characterized by, In step S4, the radiation source for γ rays is a 60Co source or a high-energy ray radiation field, the absorbed dose rate is 5-15 Gy / min, and the absorbed dose is 0.2-3 kGy.

7. The FeN according to claim 1 x -(OH) y The method for preparing composite nanomaterials is characterized by, In step S5, the washing process involves alternating between deionized water and ethanol for 3 to 5 times; the freeze-drying temperature is -40 to -60 ℃, the vacuum degree is no more than 20 Pa, and the drying time is 23 to 24 h.

8. The FeN according to claim 1 x -(OH) y The method for preparing composite nanomaterials is characterized by, Control the raw material ratio so that 3 ≤ x < 6, 0 <y<2。 9. A FeN synthesized by the method described in claims 1 to 8 x -(OH) y Composite nanomaterials.

10. A seawater-based zinc-air battery, characterized in that, The battery is loaded with the FeN as described in claim 9. x -(OH) y The composite nanomaterials use nickel foam in carbon paper as the positive electrode and zinc foil as the negative electrode. The electrolyte consists of potassium hydroxide and zinc acetate dihydrate with seawater as the solvent, and the cells are assembled into a battery.

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