Preparation method and application of phthalocyanine iron catalyst supported on defect nitrogen-doped hollow carbon spheres

Abstract

This invention discloses a method for preparing and applying an iron phthalocyanine catalyst supported on defect-doped nitrogen-filled hollow carbon spheres. The method involves precisely controlling the ratio of ammonia to tetraethyl silicate to prepare nitrogen-doped hollow carbon spheres with an average diameter of 50-60 nm. Subsequently, the nitrogen-doped hollow carbon spheres undergo a second high-temperature calcination treatment, causing some nitrogen atoms that do not contribute to catalytic activity to escape, thereby increasing the ratio of graphitic N and pyridine N and improving the stability of the hollow carbon spheres. Simultaneously, defect structures are constructed in the material, resulting in a carbon support material. Then, utilizing the π-π interaction between iron phthalocyanine molecules and the carbon support, iron phthalocyanine is successfully loaded onto the surface of the carbon support, thus obtaining a composite catalyst of iron phthalocyanine supported on defect-doped nitrogen-filled hollow carbon spheres. The material obtained by this invention is used as a catalyst host in the field of electrocatalytic oxygen reduction, achieving efficient and directional conversion in zinc-air batteries.

Description

Technical Field

[0001] This invention relates to a method for preparing a single-atom catalyst of iron phthalocyanine supported on defect-doped nitrogen-filled hollow carbon spheres and its application in the field of electrocatalysis. Specifically, the method uses defect-doped nitrogen-filled hollow carbon spheres with an average diameter between 50 and 60 nm as a carbon substrate, and loads iron phthalocyanine onto the surface of the hollow carbon spheres. Through defect engineering and optimization of the electronic structure of the Fe active center, the number of active sites is effectively increased, promoting the desorption of reaction intermediates, thereby designing and successfully preparing a highly efficient oxygen reduction catalyst. Background Technology

[0002] Under the dual pressures of surging global energy demand and the existential threat posed by climate change, the pursuit of sustainable energy solutions has reached a critical juncture. Zinc-air batteries have attracted considerable attention due to their high theoretical energy density, environmental friendliness, and low cost; however, their commercial development is limited by the slow kinetics of the oxygen reduction reaction (ORR) at the cathode, requiring high-performance electrocatalysts to promote the ORR. Although commonly used noble metal electrocatalysts (such as Pt / C, RuO2, and IrO2) exhibit excellent ORR / OER activity, their high cost, scarcity, and dependence on intermediates (such as CO and SO2) remain significant challenges. x Its susceptibility to poisoning makes it unsuitable for large-scale deployment [Adv. Mater. 2021, 33, 2006494]. Therefore, there is an urgent need to develop non-precious metal catalysts that combine high activity and stability to replace scarce platinum-based materials.

[0003] Among numerous non-noble metal catalysts, phthalocyanine metal complexes have attracted considerable attention due to their unique molecular structure advantages. Since Jasinski first discovered the ORR catalytic activity of cobalt phthalocyanine (CoPc), phthalocyanine compounds with planar macrocyclic M-N4 coordination structures (where M is Fe, Co, Ni, etc.) have gradually become a paradigm for molecular catalyst design due to their well-defined active sites and tunable electronic structures [Nature, 1964, 201(4925): 1212-1213]. Among these, iron phthalocyanine, due to its central Fe... 2+ The Fe-N4 coordination structure formed with four pyrrole nitrogen atoms exhibits excellent oxygen adsorption and activation capabilities [Journal of Colloid and Interface Science, 2023, 650(PB): 2056-2064]. However, the poor conductivity and easy aggregation of iron phthalocyanine itself severely limit its catalytic performance. Therefore, it is necessary to find a support with excellent conductivity that promotes molecular dispersion and synergistic effect with iron phthalocyanine to achieve highly efficient oxygen reduction activity.

[0004] In recent years, carbon-based nanomaterials (such as graphene, carbon nanotubes, and carbon nanospheres) have become ideal supports for enhancing the performance of molecular catalysts due to their high specific surface area, excellent electrical conductivity, and chemical stability. However, unlike other carbon nanotubes (such as carbon nanotubes and graphene), hollow carbon nanospheres (NHC) are made from sp... 2 The hollow interior of the carbon shell provides a thin-walled, open hollow framework that effectively exposes and utilizes active sites. Furthermore, the defective microchannels (or custom-designed mesopores) on the carbon shell significantly increase the catalyst contact area, promoting O2 diffusion. In addition, the high graphitization of the hollow carbon spheres enhances electrical conductivity and promotes electron transfer; the high content of pyridine N and graphitic N also promotes O2 adsorption. These structural and morphological features make NHC a novel platform for advanced electrochemical energy storage and conversion [Environ. Res., 201, 111603 (2021)]. However, most previously reported hollow carbon structures exhibit poor catalytic activity and stability in oxygen reduction reactions, and their reaction mechanisms and active sites remain controversial. Simultaneously, the large internal cavity of hollow carbon spheres (typically exceeding 100 nm) leads to low space utilization and insufficient volumetric performance in electrocatalytic applications, hindering their further large-scale development [Adv. Sci. 2023,10, 2206605]. Therefore, there is an urgent need to explore an effective strategy that can both improve the stability and catalytic activity of hollow carbon structures and precisely control the size of their internal cavities. Summary of the Invention

[0005] This invention addresses the challenges encountered in the development of phthalocyanine iron and hollow carbon spheres, providing a method for preparing and applying a single-atom catalyst supported on defect-doped nitrogen-rich hollow carbon spheres. The method involves precisely controlling the ratio of ammonia to tetraethyl silicate to prepare nitrogen-doped hollow carbon spheres with an average diameter of 50-60 nm. Subsequently, the nitrogen-doped hollow carbon spheres undergo a second high-temperature calcination treatment, causing some nitrogen atoms that do not contribute to catalytic activity to escape, thereby increasing the ratio of graphitic N and pyridine N and improving the stability of the hollow carbon spheres. Simultaneously, defect structures are constructed within the material, resulting in a structurally stable carbon support material with high loading and dense active sites. Then, utilizing the π-π interaction between phthalocyanine iron molecules and the carbon support, phthalocyanine iron is successfully loaded onto the surface of the carbon support, thus obtaining a composite catalyst of phthalocyanine iron supported on defect-doped nitrogen-rich hollow carbon spheres. The material obtained in this invention is used as a catalyst host in the field of electrocatalytic oxygen reduction, achieving efficient and directional conversion in zinc-air batteries.

[0006] The technical solution of this invention is as follows: A method for preparing an iron phthalocyanine catalyst supported on defect-doped nitrogen-filled hollow carbon spheres, comprising the following steps: (1) Add ammonia water to the mixed solution, stir at 30~80 ℃ for 10~30 min, then add tetraethyl silicate and continue stirring at 30~80 ℃ for 1~3 h, then centrifuge, wash, and finally vacuum dry to obtain silica nanospheres with an average diameter of 40~70 nm. The mixed solution is composed of deionized water and anhydrous ethanol; the volume ratio of anhydrous ethanol to deionized water is 300~400:10~30. Add 310-430 ml of mixed solution and 10-25 ml of tetraethyl silicate to every 10-25 ml of ammonia solution; The mass fraction of ammonia in the solution is 25%~28%. (2) Add 0.5 g to 2 g of silica nanospheres to deionized water and sonicate for 0.5 to 2 h to disperse them. Then add anhydrous ethanol and ammonia and stir at 20 to 30 °C for 20 to 60 min. Then add hydrochloric acid dopamine aqueous solution and continue stirring at 20 to 30 °C for 20 to 30 h. Collect silica nanospheres loaded with hydrochloric acid by centrifugation, washing and drying. Add 500-1500 mg of silica nanospheres, 10-50 ml of anhydrous ethanol, and 2-5 ml of ammonia to every 50-100 ml of deionized water. The mass ratio of dopamine hydrochloride to silica nanospheres is 1:2 to 1:4; Add 300-800 mg of dopamine hydrochloride to every 10-20 ml of deionized water; (3) The silica spheres loaded with dopamine hydrochloride obtained in step (2) are first calcined at 300~400℃ for 2~3 h under argon atmosphere, and then carbonized at 800~1000℃ for 2~3 h; then stirred and washed with sodium hydroxide solution for 5~12 h, washed with deionized water, dried and collected to obtain nitrogen-doped hollow carbon spheres; During alkaline washing, 300-500 mg of material is added to every 300-500 ml of sodium hydroxide solution; The concentration of the sodium hydroxide solution is 1~4 M; (4) The nitrogen-doped hollow carbon spheres obtained in step (3) are placed in an argon atmosphere and calcined at a high temperature of 900~1100 ℃ for 2~4 h to obtain nitrogen-doped hollow carbon spheres with defects; then, phthalocyanine iron solution is added to the defect nitrogen-doped hollow carbon sphere solution and stirred at 20~30 ℃ for 15~30 h; finally, after washing and drying, the catalyst with phthalocyanine iron supported on the defect hollow carbon spheres is obtained. In both the phthalocyanine iron solution and the nitrogen-doped hollow carbon sphere solution with defects, the solvent is DMF. Each 10-40 ml solution of phthalocyanine iron contains 10-40 mg of phthalocyanine iron; each 10-40 ml solution of nitrogen-doped hollow carbon spheres with defects contains 10-40 mg of nitrogen-doped hollow carbon spheres with defects. The mass ratio of iron phthalocyanine to defect nitrogen-doped hollow carbon spheres is 1:1 to 1:3; In step (1), the stirring speed is 300~800 rpm; the centrifugation speed is 10000~12000 rpm; In step (2), the ultrasonic power is 100 W to 500 W; the stirring speed is 300 to 800 rpm; and the centrifugation speed is 8000 to 1200 rpm. In step (3), the stirring speed is 300~800 rpm; In step (4), the ultrasonic power is 100 W to 500 W; the stirring speed is 300 to 800 rpm.

[0007] The application of the defect nitrogen-doped hollow carbon sphere supported phthalocyanine iron catalyst prepared by the method is characterized by its use as a catalyst layer material in the cathode material of a zinc-air battery for the oxygen reduction reaction.

[0008] In a zinc-air battery, the anode is a zinc plate, and the cathode is the working electrode; a stainless steel mesh is used as a current collector; and a solution containing 3.0–10 M KOH and 0.1–0.5 M ZnCl2 is used as the electrolyte. The working electrode is prepared as follows: Phthalocyanine iron catalyst and carbon black loaded on defect nitrogen-doped hollow carbon spheres are added to a mixed solution and ultrasonically dispersed for 20-60 min to obtain a dispersion. The dispersion is then dropped onto carbon cloth and allowed to dry naturally at room temperature to obtain the working electrode. Among them, every 50~90 mm 2 Add 700-900 μL of dispersion to the carbon cloth; The mixed solution is composed of Nafion and anhydrous ethanol, and the volume ratio of Nafion to anhydrous ethanol solution is 1:9 to 1:20. Add 3–5 mg of defect nitrogen-doped hollow carbon spheres loaded with phthalocyanine iron catalyst and 1–4 mg of carbon black to every 900–1100 μL of mixed solution.

[0009] The essential features of this invention are: In current technologies, iron phthalocyanine molecules are widely used in electrocatalysis due to their well-defined Fe-N4 active centers. However, the π-π interactions between iron phthalocyanine molecules lead to strong aggregation, burying most of the Fe-N4 active centers and significantly reducing catalyst accessibility. Carbon-supported single-atom catalysts, as an extension of this approach, leverage the strong electronic synergy between iron phthalocyanine and the carbon substrate to enhance catalyst activity and stability. However, due to their poor configuration, they exhibit weak O2 adsorption and O-O bond breaking capabilities, thus slowing down the oxygen reduction reaction. Therefore, adjusting the configuration of the carbon support and strengthening the electronic coupling between the metal and the support have a decisive impact on catalytic performance.

[0010] This invention synthesizes silica nanospheres with an average diameter of 50-60 nm using the Stöber method. Dopamine hydrochloride is then loaded onto the surface of the silica nanospheres and subjected to high-temperature carbonization to form a carbon layer. After removing the silica template with alkali, hollow carbon spheres are obtained. A second high-temperature calcination process releases non-active nitrogen atoms from the hollow carbon spheres, creating nitrogen vacancies and increasing the number of active sites. This also increases the ratio of graphitic nitrogen to pyridine nitrogen, thereby improving the stability of the hollow carbon spheres. This control over the carbon support structure not only reduces excess macropores and mesopores through the defects and small size of the hollow carbon spheres, thus overcoming their disadvantages of low space utilization and insufficient performance, but also, combined with the high specific surface area and excellent conductivity of the hollow carbon spheres themselves, overcomes the development obstacles such as the agglomeration and poor conductivity of phthalocyanine iron. Ultimately, a carbon support material with stable structure, high loading capacity, and dense active sites is obtained. This oxygen reduction catalyst, designed and prepared through the synergistic effect of iron phthalocyanine and defective hollow carbon spheres, not only optimizes the electronic structure of the active sites to enhance catalytic activity, but also strengthens the π-π interaction between the metal and the support, thereby improving its stability.

[0011] The beneficial effects of this invention are: (1) This invention provides a carbon support for nitrogen-doped hollow carbon spheres with defects. By calcining the nitrogen-doped hollow carbon spheres a second time, some N atoms escape, forming N vacancies, thereby introducing more structural defects. This provides more active sites, a better electronic structure, and more stable coordination for the Fe active center. Simultaneously, the escape of some N atoms increases the ratio of graphitic N to pyridine N, thus increasing its stability and resolving the controversy surrounding the stability of hollow carbon structures in the prior art. This support, in synergy with iron phthalocyanine, overcomes the developmental obstacle of iron phthalocyanine's tendency to aggregate and promotes the desorption of oxygen-hydrogen intermediates in the oxygen reduction reaction, accelerating oxygen reduction kinetics, improving oxygen reduction activity, and achieving efficient conversion in zinc-air batteries.

[0012] (2) The single-atom catalyst of iron phthalocyanine supported on defective nitrogen-doped hollow carbon spheres obtained in this invention exhibits excellent electrochemical performance under alkaline conditions for electrocatalytic oxygen reduction. The half-wave potential of the nitrogen-doped hollow carbon sphere catalyst under 0.1 M potassium hydroxide conditions is 0.760 V; the half-wave potential of the defective nitrogen-doped hollow carbon sphere catalyst under 0.1 M potassium hydroxide conditions is 0.820 V; the half-wave potential of the nitrogen-doped hollow carbon sphere supported iron phthalocyanine catalyst under 0.1 M potassium hydroxide conditions is 0.894 V; while the single-atom catalyst of iron phthalocyanine supported on defective nitrogen-doped hollow carbon spheres obtained in this invention greatly increases the activity of the catalyst through high specific surface area, multiple active sites and metal-support interaction, so that its half-wave potential can reach 0.918 V, which is better than the 0.860 V of the traditional platinum-carbon catalyst, and its stability is also better than that of the traditional platinum-carbon catalyst due to the high proportion of graphite N and pyridine N. Attached Figure Description

[0013] Figure 1 The image shows a transmission electron microscope (TEM) image of FePc-NHCS obtained in Example 1.

[0014] Figure 2 Linear voltammetric scan curves of the FePc-NHCS and Pt / C catalysts obtained in Example 1 in oxygen-saturated 0.1 mol / L KOH solution (scan rate 10 mV / s, rotation speed 1600 rpm).

[0015] Figure 3 Stability tests were conducted on the FePc-NHCS and Pt / C catalysts obtained in Example 1.

[0016] Figure 4 The methanol resistance performance of the FePc-NHCS and Pt / C catalysts obtained in Example 1 was tested.

[0017] Figure 5 The open-circuit voltage test curves of the zinc-air battery using the FePc-NHCS and Pt / C catalysts obtained in Example 1 are shown.

[0018] Figure 6 The specific capacity test curves of the zinc-air battery obtained by FePc-NHCS and Pt / C catalysts in Example 1 are shown. Detailed Implementation

[0019] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0020] Example 1: 16 ml of ammonia solution with a mass fraction of 25%–28% was added to a mixed solution of 15 ml of deionized water and 360 ml of anhydrous ethanol. The mixture was stirred at 50 °C and 500 rpm for 10 min. Then, 16 ml of tetraethyl silicate was quickly added, and the mixture was stirred for another 2 h under the same conditions. The mixture was then centrifuged at 12,000 rpm and washed three times with deionized water and anhydrous ethanol, respectively. Finally, the mixture was vacuum dried at 60 °C to obtain silica nanospheres with an average diameter of 50–60 nm.

[0021] Weigh 1 g of the obtained silica nanospheres and dissolve them in 70 ml of deionized water. Disperse the nanospheres by sonication at 400 W for 1 h. Add 20 ml of anhydrous ethanol and 3 ml of ammonia solution with a mass fraction of 25%~28%. Stir at 500 rpm for 30 min at 30 °C. Then add 10 ml of aqueous solution containing 300 mg of dopamine hydrochloride. Continue stirring at 500 rpm for 24 h at 25 °C. Centrifuge at 12000 rpm. Wash the nanospheres with deionized water until the supernatant is clear, then wash with anhydrous ethanol. Finally, vacuum dry at 60 °C to obtain silica nanospheres loaded with dopamine hydrochloride.

[0022] The silica nanospheres loaded with dopamine hydrochloride obtained above were ground for 5 min, and then calcined at 350 °C for 3 h under argon atmosphere, followed by high-temperature carbonization at 800 °C for 2 h at a heating rate of 5 °C / min. Afterwards, they were cooled to room temperature to obtain a powder. The high-temperature carbonization process involved carbonizing the dopamine hydrochloride loaded on the surface of the silica nanospheres to form a carbon layer. Weigh 550 mg of the powder obtained above and add it to 550 ml of 2 M sodium hydroxide solution. Stir at 500 rpm for 8 h at 60 °C, then centrifuge at 12000 rpm and wash with deionized water until neutral. Finally, vacuum dry at 60 °C to obtain nitrogen-doped hollow carbon spheres.

[0023] The nitrogen-doped hollow carbon spheres obtained above were ground for 5 min, calcined at 1000 ℃ for 3 h under an argon atmosphere at a heating rate of 5 ℃ / min, and then cooled to room temperature to obtain defect-laden nitrogen-doped hollow carbon spheres. The high-temperature calcination of the hollow carbon spheres after removing the silica template allowed some N atoms to escape from the hollow carbon spheres, forming N vacancies and thus creating more defects.

[0024] 30 mg of defect nitrogen-doped hollow carbon spheres were weighed and added to 30 ml of DMF solvent. Then, 30 mg of iron phthalocyanine was weighed and added to 30 ml of DMF solvent. The mixture was then sonicated at 400 W for 1 h to disperse the spheres. The iron phthalocyanine solution was then added to the solution of defect nitrogen-doped hollow carbon spheres. The mixture was stirred at 500 rpm at 25 °C for 24 h and centrifuged at 12000 rpm. The spheres were washed with DMF solution until the supernatant became colorless and transparent. Finally, the mixture was vacuum dried at 60 °C to obtain FePc-NHCS.

[0025] Weigh 4 mg of FePc-NHCS and 2 mg of carbon black, add 950 μL of anhydrous ethanol and 50 μL of 0.5 wt.% Nafion solution, and sonicate for 30 min to form a uniform dispersion.

[0026] The 10 μL of the uniformly dispersed catalyst suspension was coated onto the polished glassy carbon electrode surface with a diameter of 5 mm and allowed to air dry at room temperature.

[0027] The electrochemical tests of this invention were performed using a CHI 760E electrochemical workstation and an RRDE-type rotating ring-disc electrode apparatus from Shanghai Chenhua Co., Ltd., under ambient temperature conditions. All tests employed a standard three-electrode system in an alkaline electrolyte (0.1 M KOH). The working electrode was a circular (ring) disk glassy carbon electrode (GCE), the reference electrode was a saturated calomel electrode (Hg / HgCl, SCE), and the auxiliary electrode was a platinum wire (Pt). All test potentials were converted according to the standard hydrogen electrode (RHE), and the conversion formula is as follows:

[0028] When tested in 0.1 M KOH electrolyte:

[0029] We conducted systematic electrochemical oxygen reduction (ORR) performance tests in an oxygen (O2)-saturated 0.1 M KOH electrolyte. First, under conditions of 0 rpm (i.e., no rotation), the ORR was tested at 10 mV / s. -1The potential was cyclically scanned from 1.21 V (relative to the reversible hydrogen electrode, RHE) to 0.00 V at a high scan rate, and cyclic voltammetry (CV) scans were continuously performed until the obtained CV curves stabilized and no longer showed significant changes, thus achieving sufficient electrochemical activation. Subsequently, the electrode rotation speed was increased to 1600 rpm, and linear sweep voltammetry (LSV) tests were performed on the activated catalyst in the same electrolyte system to evaluate its steady-state oxygen reduction performance. The test results showed that the prepared FePc-NHCS (i.e., iron phthalocyanine supported on defect nitrogen-doped hollow carbon spheres) material exhibited excellent oxygen reduction activity, with a half-wave potential (E) of... 1 / 2 The V reached 0.918. This data fully demonstrates that the nitrogen-doped hollow carbon sphere-supported phthalocyanine iron catalyst with abundant defect structures, prepared by a specific method in this invention, exhibits high catalytic activity and efficiency in the electrochemical oxygen reduction reaction in alkaline media.

[0030] To evaluate the actual performance of the catalyst in the oxygen reduction reaction, it was assembled and tested in a zinc-air battery device. First, 4 mg of ground catalyst and 2 mg of carbon black were weighed and placed in a centrifuge tube. 50 μL of 5 wt.% Nafion solution and 950 μL of anhydrous ethanol were added, and the mixture was ultrasonically treated to form a homogeneous catalyst slurry. Then, 750 μL of this slurry was uniformly coated five times onto a clean carbon cloth (model HCP020) with a diameter of 1 cm. The anode and cathode of the battery were polished zinc sheets and catalyst-supported carbon cloth, respectively, with a stainless steel mesh as the current collector. The electrolyte was a mixed solution containing 6.0 M potassium hydroxide and 0.2 M zinc chloride. Actual battery performance tests were performed using a Shanghai Chenhua CHI-760E electrochemical workstation.

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of Embodiment 1 will be briefly introduced below.

[0032] Figure 1 Transmission electron microscopy (TEM) images of the FePc-NHCS prepared in Example 1 are shown. The images reveal that the catalyst maintains the spherical morphology of hollow spheres, with an average diameter of 50–60 nm. Furthermore, defect structures are observed at the edge regions of the spheres.

[0033] Figure 2The test results for the FePc-NHCS obtained in Example 1 and the commercial platinum-carbon catalyst are shown. Onset potential and half-wave potential are important indicators for evaluating the performance of oxygen reduction catalysts, while platinum-carbon catalysts are the standard for evaluating superior catalysts. In the LSV curve, the platinum-carbon catalyst has an onset potential of 0.979 V and a half-wave potential of 0.860 V. The defect nitrogen-doped hollow carbon sphere-supported phthalocyanine iron catalyst prepared in this patent has an onset potential of 1.015 V and a half-wave potential of 0.918 V, which is superior to the commercial platinum-carbon catalyst, and its production cost is significantly lower.

[0034] Figure 3 The figure shows the stability test results of FePc-NHCS obtained in Example 1 and the commercial platinum-carbon catalyst. After a stability test of 40,000 s, the FePc-NHCS catalyst still maintained 93% of its current density, which is superior to the 84% of the platinum-carbon catalyst. This indicates that the FePc-NHCS catalyst has good stability.

[0035] Figure 4 The graph shows the methanol poisoning resistance test results of FePc-NHCS obtained in Example 1 and the commercial platinum-carbon catalyst. In the graph, 3 mL of methanol was injected into an oxygen-saturated 0.1 mol / L KOH solution at 700 s. It can be seen that the current of the platinum-carbon catalyst drops very little after methanol injection, with a large fluctuation range; while the FePc-NHCS prepared in this patent maintains good performance even after slight fluctuations, indicating that the prepared catalyst has good oxygen reduction catalytic performance.

[0036] Figure 5 The graph shows the open-circuit voltage test results of the FePc-NHCS obtained in Example 1 and the commercial platinum-carbon catalyst in a zinc-air battery. The graph shows that FePc-NHCS has an open-circuit voltage of 1.49 V, which is closer to the theoretical value of 1.65 V than the 1.45 V of the platinum-carbon catalyst. This indicates that FePc-NHCS has good catalytic performance in zinc-air batteries.

[0037] Figure 6 The graph shows the specific capacity of the zinc-air battery using FePc-NHCS obtained in Example 1 and a commercial platinum-carbon catalyst. The graph shows that the specific capacity of FePc-NHCS is 773 mA hg. -1 694 mA hg higher than platinum carbon -1 The theoretical maximum specific capacity of zinc-air batteries is approximately 820 mA hg. -1 The coulombic efficiency of FePc-NHCS can reach 94.27%, which is higher than the 84.63% of commercial platinum-carbon catalysts. This indicates that FePc-NHCS has good catalytic performance in zinc-air batteries.

[0038] Example 2: 16 ml of ammonia solution was added to a mixture of 15 ml of deionized water and 360 ml of anhydrous ethanol. The mixture was stirred at 50 °C and 500 rpm for 10 min. Then, 16 ml of tetraethyl silicate was quickly added, and the mixture was stirred for another 2 h under the same conditions. The mixture was then centrifuged at 12000 rpm and washed three times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 60 °C to obtain silica nanospheres with an average diameter of 50-60 nm.

[0039] Weigh 1 g of the obtained silica nanospheres and dissolve them in 70 ml of deionized water. Disperse the nanospheres by sonication at 400 W for 1 h. Add 20 ml of anhydrous ethanol and 3 ml of ammonia water and stir at 500 rpm for 30 min at 30 °C. Then add an aqueous solution containing 300 mg of dopamine hydrochloride and continue stirring at 500 rpm for 24 h at 25 °C. Centrifuge at 12000 rpm, wash with deionized water until the supernatant is clear, then wash with anhydrous ethanol, and finally vacuum dry at 60 °C to obtain silica nanospheres loaded with dopamine hydrochloride.

[0040] The silica nanospheres loaded with dopamine hydrochloride obtained above were ground for 5 min, and then calcined at 350 °C for 3 h under argon atmosphere, followed by high-temperature carbonization at 800 °C for 2 h at a heating rate of 5 °C / min. After cooling to room temperature, the powder material was obtained.

[0041] Weigh 550 mg of the powder obtained above and add it to 550 ml of 2 M sodium hydroxide solution. Stir at 500 rpm for 8 h at 60 °C, then centrifuge at 12000 rpm and wash with deionized water until neutral. Finally, vacuum dry at 60 °C to obtain nitrogen-doped hollow carbon spheres.

[0042] 30 mg of NHC was weighed and added to 30 ml of DMF solution, and then 30 mg of iron phthalocyanine was weighed and added to 30 ml of DMF solution. Both were ultrasonicated at 400 W for 1 h to disperse them. Then the iron phthalocyanine solution was added to the nitrogen-doped hollow carbon sphere solution, and stirred at 500 rpm for 24 h at 25 °C. After centrifugation at 12000 rpm, the supernatant was washed with DMF solution until clear. Finally, the solution was vacuum dried at 60 °C to obtain FePc-NHC.

[0043] The same electrochemical testing method as in Example 1 was used.

[0044] Half-wave potential (E) of FePc-NHC catalyst1 / 2 The value is 0.894 V.

[0045] Example 3: 16 ml of ammonia solution was added to a mixture of 15 ml of deionized water and 360 ml of anhydrous ethanol. The mixture was stirred at 50 °C and 500 rpm for 10 min. Then, 16 ml of tetraethyl silicate was quickly added, and the mixture was stirred for another 2 h under the same conditions. The mixture was then centrifuged at 12000 rpm and washed three times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 60 °C to obtain silica nanospheres with an average diameter of 50-60 nm.

[0046] Weigh 1 g of the obtained silica nanospheres and dissolve them in 70 ml of deionized water. Disperse the nanospheres by sonication at 400 W for 1 h. Add 20 ml of anhydrous ethanol and 3 ml of ammonia water and stir at 500 rpm for 30 min at 30 °C. Then add an aqueous solution containing 300 mg of dopamine hydrochloride and continue stirring at 500 rpm for 24 h at 25 °C. Centrifuge at 12000 rpm, wash with deionized water until the supernatant is clear, then wash with anhydrous ethanol, and finally vacuum dry at 60 °C to obtain silica nanospheres loaded with dopamine hydrochloride.

[0047] The silica nanospheres loaded with dopamine hydrochloride obtained above were ground for 5 min, and then calcined at 350 °C for 3 h under argon atmosphere, followed by high-temperature carbonization at 800 °C for 2 h at a heating rate of 5 °C / min. After cooling to room temperature, the powder material was obtained.

[0048] Weigh 550 mg of the powder obtained above and add it to 550 ml of 2 M sodium hydroxide solution. Stir at 500 rpm for 8 h at 60 °C, then centrifuge at 12000 rpm and wash with deionized water until neutral. Finally, vacuum dry at 60 °C to obtain nitrogen-doped hollow carbon spheres NHC.

[0049] The same electrochemical testing method as in Example 1 was used.

[0050] The half-wave potential (E) of NHC catalysts 1 / 2 The value is 0.760 V.

[0051] Example 4: 16 ml of ammonia solution was added to a mixture of 15 ml of deionized water and 360 ml of anhydrous ethanol. The mixture was stirred at 50 °C and 500 rpm for 10 min. Then, 16 ml of tetraethyl silicate was quickly added, and the mixture was stirred for another 2 h under the same conditions. The mixture was then centrifuged at 12000 rpm and washed three times with deionized water and anhydrous ethanol, respectively. The mixture was then vacuum dried at 60 °C to obtain silica nanospheres with an average diameter of 50-60 nm.

[0052] Weigh 1 g of the obtained silica nanospheres and dissolve them in 70 ml of deionized water. Disperse the nanospheres by sonication at 400 W for 1 h. Add 20 ml of anhydrous ethanol and 3 ml of ammonia water and stir at 500 rpm for 30 min at 30 °C. Then add an aqueous solution containing 300 mg of dopamine hydrochloride and continue stirring at 500 rpm for 24 h at 25 °C. Centrifuge at 12000 rpm, wash with deionized water until the supernatant is clear, then wash with anhydrous ethanol, and finally vacuum dry at 60 °C to obtain silica nanospheres loaded with dopamine hydrochloride.

[0053] The silica nanospheres loaded with dopamine hydrochloride obtained above were ground for 5 min, and then calcined at 350 °C for 3 h under argon atmosphere, followed by high-temperature carbonization at 800 °C for 2 h at a heating rate of 5 °C / min. After cooling to room temperature, the powder material was obtained.

[0054] Weigh 550 mg of the powder obtained above and add it to 550 ml of 2 M sodium hydroxide solution. Stir at 500 rpm for 8 h at 60 °C, then centrifuge at 12000 rpm and wash with deionized water until neutral. Finally, vacuum dry at 60 °C to obtain nitrogen-doped hollow carbon spheres.

[0055] The nitrogen-doped hollow carbon spheres obtained above were ground for 5 min, calcined at 1000 ℃ for 3 h under an argon atmosphere with a heating rate of 5 ℃ / min, and cooled to room temperature to obtain defect nitrogen-doped hollow carbon spheres NHCS.

[0056] The same electrochemical testing method as in Example 1 was used.

[0057] Half-wave potential (E) of NHCS catalyst 1 / 2 The value is 0.820 V.

[0058] Examples 2-4 involve altering the construction of defects and the loading of iron phthalocyanine. Comparison with Example 1 shows that loading iron phthalocyanine on defect-doped nitrogen-coated hollow carbon spheres exhibits higher performance than loading iron phthalocyanine on intact nitrogen-doped hollow carbon spheres in Example 2; defect-doped nitrogen-coated hollow carbon spheres have higher performance than hollow carbon spheres; the construction of defects can optimize the structure of carbon spheres, improve the performance of carbon spheres as a support, increase active sites, enhance the interaction between metal and support, and adjust the adsorption capacity for oxygen intermediates, thereby further improving the performance of the catalyst.

[0059] As can be seen from the above embodiments, the defect-doped nitrogen-coated hollow carbon sphere-supported phthalocyanine iron catalyst FePc-NHCS prepared by the present invention, using defect-doped nitrogen-coated hollow carbon spheres as a support, not only utilizes the advantages of hollow carbon spheres such as large specific surface area, good conductivity, and strong stability, but also successfully solves the development limitations of low space utilization and poor performance of hollow carbon spheres as a support by constructing defects on small-sized hollow carbon spheres. This increases the number of active sites and enhances the binding stability between defect-doped nitrogen-coated hollow carbon spheres and phthalocyanine iron, resulting in a uniformly distributed transition metal catalyst. This provides a valuable reference for the rational design of oxygen reduction electrocatalysts with high-performance active centers.

[0060] Matters not covered in this invention are common knowledge.

Claims

1. A method for preparing a phthalocyanine iron catalyst supported on defect nitrogen-doped hollow carbon spheres, characterized in that, The method includes the following steps: (1) Add ammonia water to the mixed solution, stir at 30~80 ℃ for 10~30 min, then add tetraethyl silicate and continue stirring at 30~80 ℃ for 1~3 h, then centrifuge, wash, and finally vacuum dry to obtain silica nanospheres with an average diameter of 50~60 nm. The mixed solution is composed of deionized water and anhydrous ethanol; the volume ratio of anhydrous ethanol to deionized water is 300~400:10~30. Add 310-430 ml of mixed solution and 10-25 ml of tetraethyl silicate to every 10-25 ml of ammonia solution; (2) Add 0.5 g to 2 g of silica nanospheres to deionized water and sonicate for 0.5 to 2 h to disperse them. Then add anhydrous ethanol and ammonia and stir at 20 to 30 °C for 20 to 60 min. Then add hydrochloric acid dopamine aqueous solution and continue stirring at 20 to 30 °C for 20 to 30 h. Collect silica nanospheres loaded with hydrochloric acid by centrifugation, washing and drying. For every 50-100 ml of deionized water, add 50-100 mg of silica nanospheres, 10-50 ml of anhydrous ethanol, and 2-5 ml of ammonia. The mass ratio of dopamine hydrochloride to silica nanospheres is 1:2 to 1:4; (3) The silica spheres loaded with dopamine hydrochloride obtained in step (2) are first calcined at 300~400 ℃ for 2~3 h under argon atmosphere, and then carbonized at 800~1000 ℃ for 2~3 h; then stirred and washed with sodium hydroxide solution for 5~12 h, washed with deionized water, dried and collected to obtain nitrogen-doped hollow carbon spheres; During alkaline washing, 300-500 mg of material is added to every 300-500 ml of sodium hydroxide solution; (4) The nitrogen-doped hollow carbon spheres obtained in step (3) are placed in an argon atmosphere and calcined at a high temperature of 900~1100 ℃ for 2~4h to obtain nitrogen-doped hollow carbon spheres with defects; then the phthalocyanine iron solution is added to the defect nitrogen-doped hollow carbon sphere solution and stirred at 20~30 ℃ for 15~30h; finally, after washing and drying, the catalyst with phthalocyanine iron supported on the defect hollow carbon spheres is obtained. The mass ratio of phthalocyanine iron to defect nitrogen-doped hollow carbon spheres is 1:1 to 1:

3.

2. The preparation method of the phthalocyanine iron catalyst supported on defect nitrogen-doped hollow carbon spheres as described in claim 1, characterized in that, The mass fraction of ammonia in steps (1) and (2) is 25%~28%; In step (3), the concentration of the sodium hydroxide solution is 1~4 M.

3. The method for preparing the phthalocyanine iron catalyst supported on defect nitrogen-doped hollow carbon spheres as described in claim 1, characterized in that, In step (1), the stirring speed is 300~800 rpm; the centrifugation speed is 10000~12000 rpm; In step (2), the ultrasonic power is 100 W to 500 W; the stirring speed is 300 to 800 rpm; and the centrifugation speed is 8000 to 1200 rpm. In step (3), the stirring speed is 300~800 rpm; In step (4), the ultrasonic power is 100 W to 500 W; the stirring speed is 300 to 800 rpm.

4. The method for preparing the phthalocyanine iron catalyst supported on defect nitrogen-doped hollow carbon spheres as described in claim 1, characterized in that, Add 300-800 mg of dopamine hydrochloride to every 10-20 ml of deionized water; Each 10-40 ml solution of phthalocyanine iron contains 10-40 mg of phthalocyanine iron; each 10-40 ml solution of defective nitrogen-doped hollow carbon spheres contains 10-40 mg of defective nitrogen-doped hollow carbon spheres; the solvent for both the phthalocyanine iron solution and the solution of defective nitrogen-doped hollow carbon spheres is DMF.

5. The application of the phthalocyanine iron catalyst supported on defect nitrogen-doped hollow carbon spheres prepared by the method of claim 1, characterized in that, It is used as a catalyst for oxygen reduction reaction and as a catalyst layer material in the cathode material of zinc-air batteries.

6. The application as described in claim 5, characterized in that, In a zinc-air battery, the anode is a zinc plate, and the cathode is the working electrode; a stainless steel mesh is used as a current collector; and a solution containing 3.0–10 M KOH and 0.1–0.5 M ZnCl2 is used as the electrolyte. The working electrode is prepared by adding phthalocyanine iron catalyst and carbon black loaded on defect nitrogen-doped hollow carbon spheres into a mixed solution, ultrasonically dispersing for 20-60 min to obtain a dispersion, dropping the dispersion onto carbon cloth, and allowing it to dry naturally at room temperature. The working electrode is obtained; Among them, every 50~90 mm 2 Add 700-900 μL of dispersion to the carbon cloth; The mixed solution is composed of Nafion and anhydrous ethanol, and the volume ratio of Nafion to anhydrous ethanol solution is 1:9 to 1:

20. Add 3–5 mg of defect nitrogen-doped hollow carbon spheres loaded with phthalocyanine iron catalyst and 1–4 mg of carbon black to every 900–1100 μL of mixed solution.

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