A method for preparing FeNi nanoparticles and Fe-N x Methods for single-atom co-modification of single-walled carbon nanotube catalytic thin films

Abstract

The application relates to the field of preparation of high-efficiency metal-air battery air electrode catalytic films, in particular to a preparation method of FeNi nano-particles and Fe-N x The application relates to a method for preparing a single-atom co-modified single-walled carbon nanotube catalytic film. The single-walled carbon nanotube film is grown by using ferrocene and nickelocene as catalyst precursors and adopting an FCCVD method; the grown single-walled carbon nanotube film and FePc are vacuum sealed in a quartz tube and heated to load high-concentration Fe-N x Single-atom active sites. The application integrates OER and ORR active sites into a high-quality single-walled carbon nanotube film network structure without damaging the intrinsic structure of the carbon nanotube film, so that the carbon nanotube film becomes a high-efficiency and stable integrated dual-function catalytic film which can be directly used as an air electrode catalytic layer of a rechargeable zinc air battery. The zinc air battery assembled from the film has a high and stable open-circuit voltage, a high power density and excellent cyclic charging and discharging performance.

Description

Technical Field

[0001] This invention relates to the field of preparing high-efficiency air electrode catalytic thin films, such as those used in metal-air batteries, specifically a method for preparing FeNi nanoparticles and Fe-N nanoparticles. x A method for single-atom co-modification of single-walled carbon nanotube catalytic thin films. Background Technology

[0002] With the development of portable and wearable electronic devices, the development of flexible energy storage and conversion devices to power such devices has attracted increasing attention. Among them, rechargeable zinc-air batteries (Zn-Air batteries, ZABs) have advantages such as ultra-high theoretical energy density, low cost, environmental friendliness, stability and safety. Furthermore, combined with flexible solid electrolytes, they can be fabricated into all-solid-state flexible ZABs, making them ideal candidates for next-generation clean energy devices and flexible portable power supply devices (Reference 1, Jing Fu et al, "Electrically Rechargeable Zinc-Air Batteries: Progress, Challenges, and Perspectives", Advanced Materials (2017) 29.7). However, due to the slow kinetics of oxygen evolution and oxygen reduction reactions (OER and ORR) occurring on the air electrode during charging and discharging, it is difficult to achieve its high theoretical energy density. Therefore, expensive noble metal catalysts (Pt, Ru, Ir) are required to reduce the reaction overpotential (Reference 2, Shuangshuang Ren et al, “Bifunctional electrocatalysts for Zn–airbatteries: recent developments and future perspectives”, Journal of Materials Chemistry A (2020) 8.13. 6144-6182). To reduce costs and meet the flexible and portable requirements of portable electronic devices, there is an urgent need to develop inexpensive, high-performance flexible integrated air electrodes. Integrated catalytic films based on carbon materials have attracted much attention due to their low cost, easy availability, and high stability. At the same time, compared with traditional powder catalysts, integrated catalytic films have better mass diffusion capabilities and conductive networks. Furthermore, the thin film itself serves as the catalyst carrier, avoiding the use of organic binders that were previously used when powdered catalysts were loaded onto gas diffusion layers such as carbon fibers. This not only avoids micropore blockage caused by organic additives but also effectively improves the stability of the catalyst itself.Reference 3, Yijie Wang et al,“Recent Advances on Self-Supported Arrayed Bifunctional Oxygen Electrocatalysts for Flexible Solid-State Zn-Air Batteries,” Small (2020) 16.33.e2002902. Reference 4, TianYi Ma et al,“Self-supported electrocatalysts for advanced energy conversion processes,” Materials Today (2016) 19.5.265-273.

[0003] Among a wide variety of carbon materials, carbon nanotubes (CNTs) are often used as carrier materials for electrocatalysts due to their stable physicochemical properties, ultra-high specific surface area, excellent electrical conductivity and functionalizable surface (Reference 5, JingCheng Li et al, "Heteroatom-Doped Carbon Nanotube and Graphene-Based Electrocatalysts for Oxygen Reduction Reaction", Small (2017) 13.45). In particular, the high-quality single-walled carbon nanotube (SWCNT) films prepared by floating catalytic chemical vapor deposition (FCCVD) are themselves self-supporting flexible films; and microscopically, they are composed of a large number of SWCNT bundles with large aspect ratios that overlap each other, forming porous material transport channels and highly crystalline conductive networks, making them ideal precursors for integrated electrode catalytic layers (Reference 6, ZeyuanCao et al, “A perspective: carbon nanotube macro-films for energy storage” Energy & Environmental Science (2013) 6.11.3183-3201). However, while SWCNT films have significant advantages as electrocatalytic thin film electrodes, the following problems still need to be addressed: (1) Carbon nanotube films themselves do not possess high catalytic performance and need to be endowed with catalytic active sites through doping, composite and other methods; (2) Since ORR and OER have different reaction mechanisms, different catalytic active sites are usually required. This requires the effective integration of active sites with different catalytic performances on carbon nanotube films to achieve bifunctional catalysis; (3) Due to their ultra-high crystallinity, carbon nanotubes often require complex and time-consuming pretreatment processes when composited or doped with other materials. Furthermore, the pretreatment and subsequent active site anchoring processes are usually carried out in solution, making it difficult to maintain the structural integrity and uniformity of the film after liquid phase treatment.

[0004] Therefore, the main challenge is how to simply and effectively anchor highly efficient ORR and OER catalytic active sites on carbon nanotubes while maintaining the advantages of their flexible, integrated structure. Fe-N / C co-doped carbon catalysts can form Fe-N... x (x=1~6) Single-atom catalytic active sites have attracted widespread attention due to their high catalytic performance and stable structure. Summary of the Invention

[0005] The purpose of this invention is to provide a simple, non-destructive, and rapid method for preparing FeNi nanoparticles and Fe-N nanoparticles. xA method for creating high-performance oxygen reduction / oxygen evolution bifunctional single-walled carbon nanotube catalytic films through single-atom co-modification enables the tight binding of oxygen reduction and oxygen evolution active sites onto single-walled carbon nanotubes without damaging the macroscopic and microscopic structure of the films, resulting in thin-film catalytic electrodes with highly efficient catalytic activity for both oxygen reduction and oxygen evolution reactions.

[0006] The technical solution of the present invention:

[0007] A method for preparing FeNi nanoparticles and Fe-N x A method for single-atom co-modification of single-walled carbon nanotube catalytic films was developed. Ferrocene and nickel-ceramene were used as catalyst precursors, and a highly crystalline, highly conductive integrated single-walled carbon nanotube film was prepared using a floating catalyst chemical vapor deposition method. The FeNi nanoparticle catalyst remaining in the single-walled carbon nanotube film exhibited excellent oxygen evolution catalytic performance. By heat-treating this film with iron phthalocyanine under sealed conditions, the π-bond coupling between the iron phthalocyanine and the single-walled carbon nanotubes was utilized, allowing the iron phthalocyanine to be loaded onto the surface of the carbon nanotube film and transformed into abundant single-atom Fe-N. x The active site, as a highly efficient oxygen reduction catalytic active site, makes it a stable integrated bifunctional catalytic film.

[0008] The preparation of FeNi nanoparticles and Fe-N x The method of single-atom co-modification of single-walled carbon nanotube catalytic films produces single-walled carbon nanotube films with high aspect ratio, high crystallinity, porosity, and self-supporting properties. The film thickness is controlled by changing the collection time.

[0009] The preparation of FeNi nanoparticles and Fe-N x A method for single-atom co-modification of single-walled carbon nanotube catalytic films, wherein the mass ratio of ferrocene to nickel dicene is 1:2 to 2:1, produces high-quality single-walled carbon nanotube films with a large aspect ratio, which is greater than 5000.

[0010] The preparation of FeNi nanoparticles and Fe-N x A method for single-atom co-modification of single-walled carbon nanotube catalytic films is proposed. The FeNi nanoparticle catalyst remaining in the single-walled carbon nanotube film serves as an active site for the oxygen evolution reaction (OER), enabling the grown film to directly possess OER catalytic activity. These in-situ grown nanoparticles are tightly bonded to the single-walled carbon nanotubes, exhibiting significantly higher stability than active nanoparticles supported by post-treatment methods. The concentration of the FeNi nanoparticle catalyst is controlled by altering the growth parameters, namely hydrogen flow rate and catalyst addition amount. Simultaneously, the phase composition of the FeNi nanoparticle catalyst is modified through post-treatment processes such as oxidation and ammoniation, thereby adjusting its OER performance.

[0011] The preparation of FeNi nanoparticles and Fe-N x A method for single-atom co-modification of single-walled carbon nanotube catalytic films involves, in order to enable the single-walled carbon nanotube catalytic film to simultaneously possess oxygen reduction catalytic activity and thus serve as a bifunctional catalytic film, sealing the single-walled carbon nanotube catalytic film and phthalocyanine iron powder in a quartz tube at a mass ratio of 1:5 to 1:20 and evacuating the tube to 100°C. -2 ~10 - 4 Pa, then place the quartz tube into a tube furnace for heat treatment at a temperature of 300–600℃ for 30–150 min.

[0012] The preparation of FeNi nanoparticles and Fe-N x A method for preparing bifunctional catalytic films by single-atom co-modification of single-walled carbon nanotubes was used. The oxygen reduction and oxygen evolution catalytic performance of the prepared films was tested in a 0.1 M potassium hydroxide aqueous solution: at -3 mA / cm². 2 At the oxygen reduction current density, the oxygen reduction potential relative to the standard reversible hydrogen electrode is greater than 0.88 V; at 10 mA / cm², 2 At the oxygen evolution current density, the oxygen evolution potential of the film is less than 1.65V relative to the standard reversible hydrogen electrode; and after 5000 cycles of potential scanning at the oxygen reduction and oxygen evolution potentials, the reaction potential of the film decreases by no more than 20mV.

[0013] The preparation of FeNi nanoparticles and Fe-N x A method for single-atom co-modification of single-walled carbon nanotube catalytic films was developed. The prepared catalytic films were used as the air electrode catalytic layer in a zinc-air battery. The open-circuit voltage of the assembled aqueous electrolyte zinc-air battery was 1.35–1.45 V, and the power density was 150–220 mW / cm³. 2 The actual energy density is 600–750 mAh / g; under alkaline conditions, it has an energy density of 20 mA / cm². 2 After cycling at current density for more than 80 hours, the voltage difference fluctuation during charging and discharging is less than 50mV.

[0014] The preparation of FeNi nanoparticles and Fe-N x A method for single-atom co-modification of single-walled carbon nanotube catalytic films was developed, and the prepared catalytic films were used as the air electrode catalytic layer in a solid-state flexible zinc-air battery. The assembled flexible solid-state zinc-air battery achieved a power density greater than 50 mW / cm². 2 After 20 hours of charge-discharge cycles, the voltage difference fluctuation of the battery is less than 50mV.

[0015] The preparation of FeNi nanoparticles and Fe-N xThe method of single-atom co-modification of single-walled carbon nanotube catalytic films produces films with oxygen reduction and oxygen evolution performance superior to those of commercial noble metals Pt / C and Ir / C, respectively. Zinc-air batteries and solid-state flexible zinc-air batteries assembled from these films outperform batteries assembled from commercial noble metals Pt / C and Ir / C, respectively.

[0016] The preparation of FeNi nanoparticles and Fe-N x A method for single-atom co-modification of single-walled carbon nanotube catalytic films was used, employing a Raman shift of 1600 cm⁻¹. -1 Peak intensity at G and Raman shift at 1350 cm⁻¹ -1 The ratio of the D peak intensity at point I G / I D To determine the crystallinity of carbon materials, I G / I D =80~120, thus exhibiting good electrical conductivity and structural stability.

[0017] The design concept of this invention:

[0018] This invention uses Fe-Ni bimetallic catalysts and employs FCCVD to grow flexible, self-supporting SWCNT films as the catalytic film substrate. Simultaneously, FeNi catalyst particles remaining after carbon nanotube growth serve as active sites for the OER reaction. To achieve ORR catalytic performance, the SWCNT film is vacuum-sealed with iron phthalocyanine (FePc) and heat-treated; utilizing the π-bond coupling between FePc and carbon nanotubes, the Fe-Ni film exhibits excellent ORR catalytic activity. x Active sites are loaded onto the surface of carbon nanotubes. This method is simple and convenient, avoiding complex pretreatment and liquid-phase processing, maintaining the flexible porous structure of the carbon nanotube film, and the resulting flexible integrated thin-film electrode exhibits excellent bifunctional electrocatalytic performance.

[0019] This invention utilizes the self-supporting, porous, and interconnected network structure of SWCNT thin films grown by FCCVD, using residual nano-FeNi particles from carbon nanotube growth as OER active sites; simultaneously, it leverages the π-bond coupling between FePc and carbon nanotubes to enhance the high ORR catalytic activity of Fe-N x Single-atom active sites can be easily and efficiently loaded onto the surface of flexible SWCNT films. This allows for the excellent ORR / OER bifunctional electrocatalytic performance of the self-supporting carbon nanotube film while maintaining its macroscopic and microscopic structure, thus solving the bottleneck problem in the preparation of carbon nanotube-based electrocatalytic film electrodes.

[0020] Advantages and beneficial effects of the present invention:

[0021] 1. This invention uses high-quality SWCNT thin films as precursors for the integrated membrane electrode catalytic layer, which have good conductivity, rich microstructure and excellent flexibility.

[0022] 2. In this invention, FeNi nanoparticles remaining during the catalytic growth of carbon nanotubes are directly used as active sites for the OER reaction.

[0023] 3. This invention achieves the processing of high-concentration single-atom Fe-N x The active sites are loaded onto SWCNTs, giving them extremely high ORR catalytic activity.

[0024] 4. The method of the present invention effectively avoids the complicated pretreatment process of carbon nanotubes before they are combined with other materials.

[0025] 5. The entire thin film preparation process of this invention does not involve any liquid phase treatment process, and completely maintains the macroscopic structure, flexibility, porosity, and self-supporting integrated structure characteristics of the SWCNT thin film. Therefore, in the subsequent assembly process of rechargeable zinc-air batteries, the composite integrated thin film structure can be directly used as the air electrode catalytic layer of ZAB without the assistance of any organic adhesives, thus avoiding the use of organic adhesives and conductive additives, and also avoiding the performance and stability loss caused by the use of additives.

[0026] 6. This invention utilizes FeNi nanoparticles and Fe-N x Single-atom modified SWCNT films, used as the catalyst layer for the ZAB air electrode in an aqueous electrolyte, resulted in ZABs with high power density and good stability (20 mA / cm²). 2 (At current density, charge-discharge cycles exceed 80 hours, and the charge-discharge voltage difference fluctuation is less than 50mV).

[0027] 7. FeNi nanoparticles and Fe-N nanoparticles prepared by this invention x Single-atom modified SWCNT films can be directly used as the catalytic layer of flexible solid-state ZAB air electrodes; the assembled ZAB exhibits good flexibility and high power density (greater than 50 mW / cm²). 2 ) and excellent stability (2mA / cm 2 (After more than 20 hours of charge-discharge cycling at current density, the fluctuation of the charge-discharge voltage difference is less than 50mV).

[0028] In summary, the method of this invention simply and efficiently integrates OER and ORR active sites into a high-quality SWCNT thin film network structure without destroying the intrinsic structure of the carbon nanotube film, making it a highly efficient and stable integrated bifunctional catalytic film. This film can be directly used as the air electrode catalytic layer of a rechargeable zinc-air battery. The rechargeable zinc-air battery assembled from this film has a high and stable open-circuit voltage, high power density, and excellent cycle charge-discharge performance. Attached Figure Description

[0029] Figure 1 Preparation of FeNi nanoparticles and Fe-N x A schematic diagram of the process for a single-atom co-modified single-walled carbon nanotube catalytic thin film electrode. In the diagram, 1 is a tube furnace, 2 is a self-supporting SWCNT thin film, 3 is a stainless steel mesh, 4 is iron phthalocyanine, 5 is FeNi nanoparticle catalyst, and 6 is an SWCNT bundle.

[0030] Figure 2 Optical photographs of the actual objects. (a) Carbon nanotube film collected directly on a stainless steel mesh, (b) Carbon nanotube film transferred to a hollow quartz frame and then vacuum-sealed with FePc, (c) SWCNT film after vacuum sealing and heat treatment with FePc, i.e. Fe / Ni-SAFe-SWCNT film, (d) Working electrode for testing prepared by cutting the Fe / Ni-SAFe-SWCNT film into appropriate sizes and adhering it to glassy carbon.

[0031] Figure 3 Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of Fe / Ni-SAFe-SWCNT thin films. (a) Scanning electron microscope (SEM) image; (b) Low-magnification transmission electron microscope (TEM) image; (c) High-magnification TEM image; (d) Elemental energy dispersive spectroscopy (EDS) mapping.

[0032] Figure 4 : Single-atom Fe-N x TEM images of the Fe / Ni-SAFe-SWCNT thin film. (a) High-angle annular dark-field scanning transmission electron microscope (HADDF-STEM) image (particle-free region); (b) HADDF-STEM image (particle-containing region); (c) High-magnification TEM image and (d) HADDF-STEM image at the corresponding location. The dashed box indicates FePc coupled to the tube wall, and the circles mark single-atom Fe-N. x Active site.

[0033] Figure 5 (a) X-ray diffraction (XRD) spectrum, with the x-axis representing the diffraction angle (degree) and the y-axis representing the normalized relative intensity (au); (b) Raman spectrum, with the x-axis representing the Raman shift (cm). -1 The vertical axis Intensity represents the normalized relative intensity (au).

[0034] Figure 6The ORR / OER catalytic performance and stability of Fe / Ni-SAFe-SWCNT films and control samples under alkaline conditions. (a) ORR polarization curve; (b) OER polarization curve; (c) ORR polarization curve and (d) OER polarization curve before and after 5000 cyclic potential scans (CV). Wherein, the horizontal axis Potential represents the potential relative to the standard hydrogen electrode (V versus RHE), and the vertical axis J represents the current density (mA / cm²). 2 ).

[0035] Figure 7 (a) Schematic diagram of a chargeable ZAB assembled using Fe / Ni-SAFe-SWCNT thin film as the air electrode catalyst layer; (b) Power density, and a comparison with the performance of a ZAB assembled using a noble metal Pt / C-Ir / C catalyst. The vertical axis (left) represents potential (V), and the vertical axis (right) represents power density (mW / cm²). -2 The horizontal axis J represents the current density (mA / cm²). -2 (c) Energy density, and a comparison with the performance of ZAB assembled with noble metal Pt / C-Ir / C catalysts. The vertical axis, Voltage, represents the discharge voltage (V), and the horizontal axis, J, represents the current density (mA / cm²). -2 (d) Cyclic charge-discharge test curves, with the horizontal axis Time representing the cycle time (h) and the vertical axis Voltage representing the battery charge-discharge voltage (V).

[0036] Figure 8 (a) Schematic diagram of the flexible solid-state ZAB assembled using Fe / Ni-SAFe-SWCNT thin film as the air electrode catalyst layer; (b) Power density, and a comparison with the performance of ZAB assembled using noble metal Pt / C-Ir / C catalyst. The vertical axis (left) represents potential (V), and the vertical axis (right) represents power density (mW / cm²). -2 The horizontal axis J represents the current density (mA / cm²). -2 (c) Cyclic charge-discharge test curve, with the horizontal axis Time representing the cycle time (h) and the vertical axis Voltage representing the battery charge-discharge voltage (V). Detailed Implementation

[0037] In its specific implementation, this invention proposes a method for preparing FeNi nanoparticles and Fe-N nanoparticles. x The method for creating high-performance oxygen reduction / oxygen evolution bifunctional single-walled carbon nanotube catalytic films with single-atom co-modification mainly consists of the following steps ( Figure 1 ):

[0038] (1) Using ferrocene and nickel ferrocene as catalyst precursors, self-supporting SWCNT films with residual FeNi nanoparticles were grown and collected by FCCVD method; the grown carbon nanotubes were high-quality SWCNT films with large aspect ratio, rather than large-diameter, low-crystallinity multi-walled carbon nanotubes, so as to ensure that the film has a flexible and stable macrostructure and a porous, high specific surface area microstructure.

[0039] (2) The grown SWCNT film and FePc were vacuum sealed together in a quartz tube;

[0040] (3) Heat treatment of the quartz tube containing SWCNT film and FePc powder.

[0041] Among them, the FeNi particles, which are catalyst residues and tightly bound to SWCNTs, can serve as stable catalytic active sites for the OER reaction. To enable the film to simultaneously possess bifunctional ORR reaction catalytic performance, the FeNi particle-modified SWCNT film was sealed with FePc powder and heat-treated. Utilizing the π-bond coupling effect, FePc was loaded onto the carbon nanotube surface to form abundant single-atom Fe-N bonds. x Active sites, serving as highly efficient ORR catalytic active sites.

[0042] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention is described in detail below with reference to embodiments and accompanying drawings, but this is not intended to limit the scope of protection of this application.

[0043] Example 1

[0044] like Figure 1 As shown, this embodiment prepares FeNi nanoparticles and Fe-N nanoparticles. x A method for producing high-performance oxygen reduction / oxygen evolution bifunctional single-walled carbon nanotube catalytic films co-modified with single atoms includes the following steps:

[0045] (1) Ferrocene and nickel dicene were used as catalyst precursors to grow and collect high-quality self-supporting SWCNT films 2 using FCCVD. Ferrocene and nickel dicene were dissolved in toluene, and thiophene was used as a growth promoter. The mass ratio of the catalyst toluene:ferrocene:nickel dicene:thiophene was 9.1:0.25:0.5:0.067. The catalyst precursor was injected into the tube furnace 1 for SWCNT growth using a syringe and atomized. The growth temperature of SWCNTs was 1100℃, the carrier gas was hydrogen (H2), and the gaseous carbon source was ethylene (C2H4). A stainless steel mesh 3 was placed downstream of the tube furnace 1 to collect the self-supporting SWCNT film 2. The thickness of the self-supporting SWCNT film 2 deposited on the stainless steel mesh 3 could be adjusted by changing the collection time. In this embodiment, SWCNTs collected after 1 hour of growth were used, and FeNi nanoparticle catalyst 5 remained on the grown self-supporting SWCNT film 2.

[0046] like Figure 2 As shown in (a), the collected SWCNT thin films exhibit a good flexible integrated structure, making them a good substrate material for flexible electrodes.

[0047] (2) Cut the self-supporting SWCNT film 2 to a size of 4cm × 2cm and a mass of 1.28mg, and transfer it to a hollow quartz substrate to prevent the film from curling and breaking during the sealing process (the quartz substrate is 4cm × 2cm × 2mm in size, with a 3cm × 1.5cm hole in the middle). Figure 2 As shown in (b), the self-supporting SWCNT film 2, together with the quartz substrate, is placed in a quartz tube. 30 mg of FePc powder 4 is then placed in the quartz tube, and the quartz tube is evacuated to a pressure of 10. -3 Pa and seal.

[0048] (3) The sealed quartz tube is pushed into tube furnace 1 for heating treatment, with the temperature increased to 500℃ at a rate of 10℃ / min, and held for 2 hours. During the heating process, FePc powder sublimates. Due to the π-bond coupling between FePc molecules and SWCNTs, free FePc molecules are coupled onto the SWCNT surface, thus obtaining FeNi nanoparticles and Fe-N nanoparticles. x A high-performance ORR / OER bifunctional SWCNT catalytic film co-modified with single atoms, wherein FeNi nanoparticle catalyst 5 is supported on SWCNT tube bundle 6 and iron phthalocyanine 4 is supported on the surface of SWCNT tube bundle 6.

[0049] like Figure 2 As shown in (c), the heat-treated Fe / Ni-SAFe-SWCNT catalytic film, without any liquid-phase treatment, completely preserves the flexible, integrated structure of the SWCNT film. Figure 2 As shown in (d), the catalytic film can be directly used as the air electrode catalytic layer of the Zn-air battery. When testing its ORR and OER performance in a three-electrode system, it can be directly attached to the glassy carbon electrode for testing.

[0050] (4) Figure 3 The microstructure characterization of the Fe / Ni-SAFe-SWCNT thin film is shown. Figure 3 The SEM image in (a) shows that the film consists of numerous intertwined and overlapping SWCNT bundles, forming effective conductive pathways. The intertwined SWCNTs provide a large specific surface area for FePc coupling. The overlapping SWCNT bundles create a rich pore structure, which is beneficial for mass transport during the catalytic reaction. Figure 3(b) Low-magnification TEM images show that the SWCNT bundles are loaded with abundant nano-metal particles. These abundant nano-metal particles are FeNi metal particles remaining from the SWCNT growth process. These nanoparticles possess good OER catalytic performance and can therefore be directly used as catalytic active sites for the OER reaction. Figure 3 (c) High-magnification TEM images of the thin film show that a distinct amorphous carbon layer is attached to the outer surface of the SWCNT bundle, which may be FePc coupled to the SWCNT surface. Figure 3 (d) The elemental energy distribution diagram of the thin film shows that nitrogen (N) is uniformly distributed on the surface of the SWCNT bundle, and since N originates only from FePc, it is inferred that FePc was successfully coupled to the SWCNT surface. Furthermore, aggregation of Fe and Ni elements can be observed at the particle locations, proving that the nano-metal particles on the tube wall are FeNi nanoparticles.

[0051] (5) To more intuitively demonstrate the successful coupling of FePc and the anchoring of single-atom Fe-Nx active sites, the Fe / Ni-SAFe-SWCNT thin film was characterized using aberration-corrected electron microscopy. In the HADDF-STEM images of the film, Fe and Ni atoms exhibit brighter contrast due to their larger atomic numbers. Figure 4 (a) Regions without metal nanoparticles, and Figure 4 (b) In the regions where nanoparticles are present, the SWCNT tube walls exhibit abundant bright spots, indicating that they are rich single-atom Fe-N coupled with FePc. x Active site. (By...) Figure 4 (c) High-magnification TEM image (within the dashed box) and corresponding location Figure 4 (d) HADDF-STEM image shows bright spots (circles) of single-atom Fe-Nx loaded on the tube wall, further proving the successful coupling of FePc.

[0052] (6) The Fe / Ni-SAFe-SWCNT thin film was characterized by Raman spectroscopy and XRD, and compared with FePc powder. Figure 5 As shown in (a), XRD characterization reveals that the two peaks near 44.3° and 51.5° correspond to the

[111] and

[200] crystal planes of the FeNi3 alloy, respectively. The presence of a peak near 7°, identical to that of FePc powder, indirectly indicates the successful coupling of FePc onto SWCNTs. Figure 5 (b) shows the Raman spectrum of the thin film, which researchers typically use at 1600 cm⁻¹. -1 The intensity of peak G at 1350 cm⁻¹ -1 The ratio of the D peak intensity at position (I) G / I DThe crystallinity of carbon materials can be determined by using a high-intensity G peak. It can be seen that the film possesses a high-intensity G peak, indicating extremely high crystallinity, which in turn leads to good electrical conductivity and structural stability. Meanwhile, at 500–1000 cm⁻¹... -1 and 1500cm -1 The presence of characteristic peaks of FePc at all locations indicates the successful coupling of FePc onto SWCNT.

[0053] (7) Cut the treated carbon nanotube film into 0.7cm × 0.7cm squares, place them on a rotating disk electrode, and add a drop of ethanol to make it adhere to the electrode surface. Figure 6 As shown in (a), its oxygen reduction catalytic performance was tested under a three-electrode system, and the obtained current density-voltage curve was obtained; when the current density reached -3 mA / cm², the catalytic performance was tested. 2 Its potential is E j＝-3mA / cm2 =0.92V. Compared to traditional Pt / C catalysts supported on glassy carbon electrodes (E j＝-3mA / cm2 =0.87V), offering higher performance. For example... Figure 6 As shown in (b), its oxygen evolution performance was also tested at a current density of 10 mA / cm². 2 At that time, the potential was 1.55 V, higher than that of noble metal Ir / C catalysts (1.60 V). For example... Figure 6 (c) and Figure 6 As shown in (d), to investigate the stability of the catalytic film, the film was subjected to 5000 CV cycles within the respective reaction potential ranges of ORR and OER, and the polarization curves before and after the cycles were obtained. The ORR potential of the catalytic film decreased by 5 mV, while the OER potential remained stable, which is significantly better than that of noble metal Pt / C and Ir / C catalysts.

[0054] (8) Figure 7 As shown in (a), the Fe / Ni-SAFe-SWCNT film can be directly used as the catalyst layer for the air electrode of a Zn-air battery, forming an assembled aqueous electrolyte Zn-air battery structure. The catalyst film, along with a nickel foam current collector and a carbon fiber gas diffusion layer, is pressed to form the air electrode. A polished zinc sheet is used as the negative electrode. The electrolyte filling chamber is located between the air electrode and the negative electrode. The electrolyte is a mixed electrolyte solution of 6 mol / L potassium hydroxide aqueous solution and 0.2 mol / L zinc acetate aqueous solution. Figure 7 As shown in (b), the power density of the assembled zinc-air battery was tested, and its peak power density reached 204 mW / cm². 2 This is superior to cells assembled using traditional Pt / C and Ir / C loaded on carbon cloth as electrodes (170mW / cm). 2 At the same time, such as Figure 7As shown in (c), the Zn-air battery assembled from Fe / Ni-SAFe-SWCNT thin films exhibits a higher practical energy density (787 mAh / g). Figure 7 As shown in (d), the long-term charge-discharge cycle stability of the Zn-air battery was tested. After 100 hours of long-term charge-discharge potential cycling, the charge-discharge voltage difference remained basically unchanged, indicating that it has excellent stability.

[0055] (9) Due to the flexible structure of the Fe / Ni-SAFe-SWCNT film, this film can also serve as a catalyst layer for flexible solid-state Zn-air batteries, providing power for potential future flexible electronic devices. For example... Figure 8 As shown in (a), the structure of a flexible solid-state Zn-air battery is as follows: the solid electrolyte is composed of polyvinyl alcohol mixed with 6 mol / L potassium hydroxide and 0.2 mol / L zinc acetate, dissolved at 90°C, and then cooled and solidified to form a solid gel electrolyte. A flexible solid-state Zn-air battery can be fabricated by using a polished, flexible Zn sheet as the negative electrode and a catalytic film as the positive electrode. Figure 8 As shown in (b), the power density of this battery can reach 78 mW / cm². 2 The performance of flexible solid-state Zn-air cells equipped with precious metal Pt / C and Ir / C catalysts is higher than that of the Zn-air cells (67mW / cm²). 2 ).like Figure 8 As shown in (c), the long-term charge-discharge cycle stability of the solid-state battery was also tested. After 24 hours of charge-discharge cycles, the charge-discharge potential of the battery remained basically unchanged, indicating that it has excellent stability.

[0056] Example 2

[0057] (1) Step (1) is exactly the same as step (1) in Example 1.

[0058] (2) Step (2) Using the method and process of step (2) in Example 1, 10 mg FePc and SWCNT film are sealed together.

[0059] (3) Step (3) adopts the method and process of step (3) in Example 1, and the heat treatment temperature is 400℃.

[0060] (4) Step (4) adopts the characterization and testing methods of Step (4-7) in Example 1. For ORR performance, when the current density reaches -3mA / cm 2 Its potential is E j＝-3mA / cm2 =0.88V. For OER performance, when the current density is 10mA / cm² 2 When, its potential is E j＝10mA / cm2 =1.58V.

[0061] (5) Step (5) is exactly the same as step (8) in Example 1, and the peak power density of the assembled zinc-air battery can reach 176 mW / cm². 2 Its actual energy density can reach 720mAh / g.

[0062] Example 3

[0063] (1) Step (1) is exactly the same as step (1) in Example 1.

[0064] (2) Step (2) Using the method and process of step (2) in Example 1, 50 mg FePc and SWCNT film are sealed together.

[0065] (3) Step (3) adopts the method and process of step (3) in Example 1. The heat treatment temperature is 600℃.

[0066] (4) Step (4) adopts the characterization and testing methods of Step (4-7) in Example 1. For ORR performance, when the current density reaches -3mA / cm 2 Its potential is E j＝-3mA / cm2 =0.74V. For OER performance, when the current density is 10mA / cm² 2 When, its potential is E j＝10mA / cm2 =1.72V

[0067] (5) Step (5) is exactly the same as step (8) in Example 1, and the peak power density of the assembled zinc-air battery can reach 134 mW / cm². 2 Its actual energy density can reach 530 mAh g. -1 .

[0068] Comparative Example 1

[0069] In this comparative example, only ferrocene was used as a catalyst precursor to grow carbon nanotubes, and FePc was coupled onto the carbon nanotubes grown only with ferrocene to study the effect of Ni introduction on the catalytic performance of the thin film. The specific steps are as follows:

[0070] (1) Step (1) adopts the method and process of step (1) in Example 1, and the mass ratio of catalyst toluene: ferrocene: thiophene is 0.91: 0.25: 0.067.

[0071] (2) Step (2) is exactly the same as step (2) in Example 1.

[0072] (3) Step (3) is exactly the same as step (3) in Example 1.

[0073] (4) Step (4) adopts the characterization and testing methods of Step (4-7) in Example 1. The ORR and OER performance of the SWCNT thin film directly grown with ferrocene and coupled with FePc were tested as the working electrode. The results are as follows: Figure 6 As shown in (a) and (b). For ORR performance, when the current density reaches -3 mA cm⁻¹ -2 Its potential is E j＝-3mA / cm2 =0.89V; For OER performance, when the current density is 10mA / cm 2 When, its potential is E j＝10mA / cm2 =1.67V.

[0074] Compared with Example 1, this comparative example demonstrates that the OER performance of the thin film decreases significantly in the absence of Ni. This illustrates that using Fe / Ni bimetallic catalysts to grow carbon nanotubes is crucial for achieving the desired OER catalytic performance of the thin film.

[0075] Comparative Example 2

[0076] In this comparative example, ferrocene and nickel-cerocene were used as catalyst precursors to grow carbon nanotubes. No FePc was added in subsequent treatments to investigate the role of FePc in the catalytic reaction. The specific steps are as follows:

[0077] (1) Step (1) is exactly the same as step (1) in Example 1.

[0078] (2) The ORR and OER performance of the grown carbon nanotube film were directly tested. Step (2) adopted the same testing method and process as step (4) in Example 1. The ORR and OER performance of the Fe and Ni bimetallic grown SWCNT film were directly tested as the working electrode. The results are as follows: Figure 6 As shown in (a) and (b). For ORR performance, when the current density reaches -3 mA / cm² 2 Its potential is E j＝-3mA / cm2 =0.56V; For OER performance, when the current density is 10mA / cm 2 When, its potential is E j＝10mA / cm2 =1.57V.

[0079] Comparing Example 1 with Comparative Examples 1 and 2, this comparative example demonstrates that the addition of Ni is crucial for improving the OER of the catalytic film, and FeNi alloy particles are the main active sites for the OER reaction; the addition of FePc is crucial for improving the ORR performance of the film, and single-atom Fe-N x It is the main active site of the ORR reaction.

[0080] The results of the examples and comparative examples show that the present invention provides a method for preparing FeNi nanoparticles and Fe-N nanoparticles. xA method for preparing high-performance oxygen reduction / oxygen evolution bifunctional single-walled carbon nanotube catalytic films with single-atom co-modification is presented. This method is not only simple but also preserves the microscopic and macroscopic structure of the carbon nanotube film. Furthermore, it achieves the complementary advantages of high OER catalytic activity FeNi nanoparticles and high ORR activity single-atom Fe active sites, overcoming the current bottleneck in the controllable preparation of high-performance carbon nanotube-based film electrodes. The prepared FeNi nanoparticles and Fe-N... x The single-atom co-modified SWCNT catalytic film exhibits excellent ORR and OER catalytic performance and stability, and can be directly used as the air electrode catalytic layer for rechargeable Zn-air batteries and flexible solid-state Zn-air batteries.

Claims

1. A method for preparing FeNi nanoparticles and Fe-N x A method for single-atom co-modification of single-walled carbon nanotube catalytic thin films, characterized in that, Using ferrocene and nickel ferrocene as catalyst precursors, highly crystalline and highly conductive integrated single-walled carbon nanotube films were prepared by floating catalyst chemical vapor deposition. The FeNi nanoparticle catalyst remaining in the single-walled carbon nanotube film exhibited good oxygen evolution catalytic performance. By heat-treating the film with ferrophthalocyanine under sealed conditions, the π-bond coupling between ferrophthalocyanine and single-walled carbon nanotubes was utilized to load ferrophthalocyanine onto the surface of the carbon nanotube film, transforming it into abundant single-atom Fe-N. x The active site, as a highly efficient oxygen reduction catalytic active site, makes it a stable integrated bifunctional catalytic film.

2. Preparation of FeNi nanoparticles and Fe-N according to claim 1 x A method for single-atom co-modification of single-walled carbon nanotube catalytic thin films, characterized in that, The grown single-walled carbon nanotube films are characterized by high aspect ratio, high crystallinity, porosity, and self-supporting properties. The film thickness is controlled by changing the collection time.

3. Preparation of FeNi nanoparticles and Fe-N according to claim 1 x A method for single-atom co-modification of single-walled carbon nanotube catalytic thin films, characterized in that, The mass ratio of ferrocene to nickel ferrocene is 1:2 to 2:1, resulting in high-quality single-walled carbon nanotube films with a large aspect ratio, which is greater than 5000.

4. Preparation of FeNi nanoparticles and Fe-N according to claim 1 x A method for single-atom co-modification of single-walled carbon nanotube catalytic thin films, characterized in that, The FeNi nanoparticle catalyst remaining in the single-walled carbon nanotube film serves as an active site for the oxygen evolution reaction, enabling the grown film to directly possess oxygen evolution catalytic activity. This in-situ grown nanoparticle is tightly bound to the single-walled carbon nanotube, exhibiting significantly higher stability than active nanoparticles supported by post-treatment methods. The concentration of the FeNi nanoparticle catalyst is controlled by altering the growth parameters, namely, the hydrogen flow rate and the amount of catalyst added. Simultaneously, the phase composition of the FeNi nanoparticle catalyst is modified through post-treatment processes such as oxidation and ammoniation, thereby adjusting its oxygen evolution performance.

5. Preparation of FeNi nanoparticles and Fe-N according to claim 1 x A method for single-atom co-modification of single-walled carbon nanotube catalytic thin films, characterized in that, To enable the single-walled carbon nanotube catalytic film to simultaneously possess oxygen reduction catalytic activity and thus serve as a bifunctional catalytic film, the single-walled carbon nanotube catalytic film and phthalocyanine iron powder were sealed in a quartz tube at a mass ratio of 1:5 to 1:20 and the tube was evacuated to 10°C. -2 ~10 -4 Pa, then place the quartz tube into a tube furnace for heat treatment at a temperature of 300–600℃ for 30–150 min.

6. Preparation of FeNi nanoparticles and Fe-N according to claim 1 x A method for single-atom co-modification of single-walled carbon nanotube catalytic thin films, characterized in that, The prepared bifunctional catalytic film was tested for its oxygen reduction and oxygen evolution catalytic performance in a 0.1 M potassium hydroxide aqueous solution: at -3 mA / cm 2 At the oxygen reduction current density, the oxygen reduction potential relative to the standard reversible hydrogen electrode is greater than 0.88 V; at 10 mA / cm², 2 At the oxygen evolution current density, the oxygen evolution potential of the film is less than 1.65V relative to the standard reversible hydrogen electrode; and after 5000 cycles of potential scanning at the oxygen reduction and oxygen evolution potentials, the reaction potential of the film decreases by no more than 20mV.

7. Preparation of FeNi nanoparticles and Fe-N according to claim 1 x A method for single-atom co-modification of single-walled carbon nanotube catalytic thin films, characterized in that, The prepared catalytic film was used as the air electrode catalytic layer of a zinc-air battery. The open-circuit voltage of the assembled aqueous electrolyte zinc-air battery was 1.35–1.45 V, and the power density of the zinc-air battery was 150–220 mW / cm³. 2 The actual energy density is 600–750 mAh / g; under alkaline conditions, it has an energy density of 20 mA / cm². 2 After cycling at current density for more than 80 hours, the voltage difference fluctuation during charging and discharging is less than 50mV.

8. Preparation of FeNi nanoparticles and Fe-N according to claim 1 x A method for single-atom co-modification of single-walled carbon nanotube catalytic thin films, characterized in that, The prepared catalytic film was used as the air electrode catalytic layer in a solid-state flexible zinc-air battery, and the assembled flexible solid-state zinc-air battery had a power density greater than 50 mW / cm². 2 After 20 hours of charge-discharge cycles, the voltage difference fluctuation of the battery is less than 50mV.

9. Preparation of FeNi nanoparticles and Fe-N according to claim 1 x A method for single-atom co-modification of single-walled carbon nanotube catalytic thin films, characterized in that, The oxygen reduction and oxygen evolution properties of the prepared thin film are superior to those of commercial precious metals Pt / C and Ir / C, respectively. The performance of zinc-air batteries and solid-state flexible zinc-air batteries assembled with the film is superior to that of batteries assembled with commercial precious metals Pt / C and Ir / C, respectively.

10. Preparation of FeNi nanoparticles and Fe-N according to claim 1 x A method for single-atom co-modification of single-walled carbon nanotube catalytic thin films, characterized in that, Used in Raman shift 1600cm -1 Peak intensity at G and Raman shift at 1350 cm⁻¹ -1 The ratio of the D peak intensity at point I G / I D To determine the crystallinity of carbon materials, I G / I D =80~120, thus exhibiting good electrical conductivity and structural stability.

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