Preparation method and application of Co and Fe double-metal doped graphite phase carbon nitride high-specific-area nanotube for zinc air battery

Abstract

The invention discloses a preparation method and application of a Co and Fe bimetal doped graphite phase carbon nitride high-specific-area nanotube for a zinc air battery, relates to the field of battery preparation, and aims to solve the problems of low surface area, poor conductivity and the like of graphite phase carbon nitride. The preparation method comprises the following steps: by using a simple solution and a secondary sintering method, taking hydrated salt of cobalt, urea and dicyandiamide as precursors, firstly synthesizing graphite phase carbon nitride in an air atmosphere, then carrying out low-temperature induction in an argon-hydrogen mixed atmosphere to generate graphite phase carbon nitride nanotubes, and finally modifying an iron element to obtain the bimetallic composite catalyst. The graphite phase carbon nitride nanotube is obtained. The specific surface area of the bimetallic composite Fe (at) Co / CNNTs graphite phase carbon nitride nanotube catalyst obtained by regulating and controlling components and morphology of graphite phase carbon nitride is greatly increased. Compared with precious metal, the Fe-coated Co / CNNTs catalyst shows potential advantages in the aspects of cost effectiveness and catalytic performance.

Description

Technical Field

[0001] The present invention belongs to the field of battery preparation, and in particular relates to a preparation method and application of Co, Fe bimetallic doped graphite phase carbon nitride high specific area nanotubes for zinc-air batteries. Background Art

[0002] The development of clean renewable energy has become a necessary and urgent task. Zinc-air batteries (ZABs), as an efficient and clean power generation device, have the advantages of low cost, good safety and high energy density, and have attracted widespread attention from academia and industry. However, the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on the multi-electron, multi-proton coupled cathode electrode involve many intermediates and reaction barriers, resulting in slow reaction kinetics, which greatly limits their commercial application. It is well known that precious metals (such as Pt, Ru and Ir) are the most advanced catalysts for ORR and OER reactions in zinc-air batteries (ZABs). However, their resource shortage and high price have limited their large-scale application. Therefore, it is necessary to explore cheaper alternatives with significant activity and stability for long-term use.

[0003] Over the past few decades, transition metal catalysts have garnered significant attention due to their unique electronic properties and high atomic utilization efficiency. However, isolated transition metal catalysts can suffer from morphological and structural heterogeneity, with the presence of a large number of inactive iron-based particles, which hinder the catalyst's access to active sites and reduce its stability and mass activity. Therefore, finding a suitable substrate is crucial. Inspired by the remarkable activity of cobalt in the oxygen reduction reaction (ORR), transition metal (Fe, Co, Ni, etc.) and nitrogen co-doped carbon nanomaterials (MNCs) have attracted significant attention due to their unique electronic properties and high atomic utilization efficiency. Metal and nitrogen doping has proven to be an effective method for disrupting the electroneutrality of CNCs, thereby obtaining more M-Nx active sites due to increased charge and spin density, thereby enhancing the potential electrocatalytic activity of CNCs for zinc-air batteries. However, complex, multi-step preparation methods have hindered the precise control of atomically dispersed M-Nx sites. Furthermore, little research has been conducted on how transition metal elements specifically influence the catalytic efficiency and selectivity in the ORR and OER processes. Therefore, the development of a universal method for preparing highly active MNC catalysts is highly desirable.

[0004] Currently, carbon-based heteroatom-doped non-precious metal catalysts are widely considered to be potential alternatives to Pt-based catalysts in zinc-air battery catalysts due to their advantages such as good electrical conductivity, large surface area, good durability, and adjustable composition and morphology. Among carbon-based materials, graphitic carbon nitride (g-C3N4) is a material composed of heptazine ring structural units similar to graphite. Due to its ultra-high nitrogen content (theoretically up to 60wt%), it has a high electronegativity. This allows the transfer of pyridine nitrogen atoms to adjacent carbon rings, enhancing the nucleophilic strength, thereby enhancing the adsorption of O2 and further promoting oxygen reduction reaction activity. Due to its excellent adsorption capacity, high chemical stability, controllable structure, low cost, and high nitrogen content, it has been widely used as an electrocatalyst support. Niu et al. demonstrated for the first time a universal solid-phase pyrolysis method to synthesize mixed transition metal nanocrystals embedded in graphitic carbon nitride nanosheets (M-CNNs) as efficient oxygen electrocatalysts for rechargeable zinc-air batteries (ZABs). The resulting Co-CNNs-0.7 catalyst not only exhibited comparable half-wave potentials and lower OER overpotentials than commercial catalysts, but also highlighted the synergistic effects of heterogeneous interfaces in oxygen electrocatalysis, providing a new avenue for studying metal-air cathode materials. The multi-electron, multi-proton coupled oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at ZAB cathodes involve numerous intermediates and reaction barriers, resulting in sluggish reaction kinetics and significantly limiting their commercial application. However, the current noble metal catalysts used for these reactions are limited in their large-scale application due to resource shortages and high costs. Problems such as the low surface area and poor electrical conductivity of graphitic carbon nitride limit its practical application in OER and OER. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a method for preparing Co, Fe bimetallic doped graphite phase carbon nitride high specific area nanotubes for zinc-air batteries.

[0006] The present invention provides a method for preparing Co and Fe bimetallic doped graphite phase carbon nitride high specific area nanotubes for zinc-air batteries, the preparation method being as follows:

[0007] Step 1: dissolving urea, dicyandiamide and cobalt chloride in deionized water, cooling with liquid nitrogen, and then freeze-drying;

[0008] Step 2: Place the dried sample in a muffle furnace and sinter it in an air atmosphere to obtain graphite carbon nitride;

[0009] Step 3: Secondary sintering of the graphite phase carbon nitride in an argon-hydrogen mixed atmosphere to obtain graphite phase carbon nitride nanotubes (CNNTs);

[0010] Step 4: Modify Fe on graphite phase carbon nitride nanotubes CNNTs3+ , and dried to obtain Fe@Co / CNNTs catalyst.

[0011] Furthermore, the mass volume ratio of urea, dicyandiamide, cobalt chloride and deionized water described in step 1 is (5-7) g: (3-5) g: 0.1 g: (20-40) mL.

[0012] Furthermore, the mass volume ratio of urea, dicyandiamide, cobalt chloride and deionized water described in step 1 is 6g:4g:0.1g:30mL.

[0013] Furthermore, the sintering conditions described in step 2 are: heating to 540-560° C. at a heating rate of 3-7° C. / min and keeping the temperature for 1-3 hours.

[0014] Furthermore, the sintering conditions described in step 2 are: heating to 550° C. at a heating rate of 5° C. / min and keeping the temperature for 2 h.

[0015] Furthermore, the secondary sintering conditions described in step three are: heating to 500-540° C. at a heating rate of 5-15° C. / min.

[0016] Then, the temperature was increased to 520° C. at a heating rate of 10° C. / min.

[0017] Furthermore, the Fe is modified on the graphite phase carbon nitride nanotubes CNNTs as described in step 4. 3+ Specifically, graphite phase carbon nitride nanotubes and ferric chloride were added to ethanol in a ratio of 2:1 to 1:2, stirred evenly, and freeze-dried for one day to obtain Fe@Co / CNNTs catalyst material.

[0018] The Co, Fe bimetallic doped graphite phase carbon nitride high specific area nanotubes prepared by the present invention are used as cathode catalysts of zinc-air batteries.

[0019] The present invention has the following beneficial effects:

[0020] The present invention uses a simple solution and secondary sintering method, with cobalt hydrate, urea and dicyandiamide as precursors, first synthesizing graphite phase carbon nitride in an air atmosphere, then inducing the generation of graphite phase carbon nitride nanotubes at low temperature in an argon-hydrogen mixed atmosphere, and finally modifying the iron element to obtain a bimetallic composite catalyst, the obtained graphite phase carbon nitride nanotubes. The introduction of Co acts as a catalyst for the growth of graphite phase carbon nitride nanotubes in a reducing atmosphere. At the same time, the synergistic effect of graphite phase carbon nitride nanotubes and the two metals makes the catalyst have good oxygen reduction performance (ORR) and oxygen evolution performance (OER). It is used as a cathode catalyst for zinc-air batteries and exhibits excellent activity and stability. The present invention obtains a bimetallic composite Fe@Co / CNNTs graphite phase carbon nitride nanotube catalyst by controlling the composition and morphology of graphite phase carbon nitride, and the specific surface area is greatly improved. The specific surface area of Fe@Co / CNNTs is as high as 270.652m 2 / g, greatly promoting the exposure of the active area. The synergistic effect of graphene-phase carbon nitride nanotubes and the two metals makes the catalyst have good ORR performance (E1 / 2 = 0.84V) and OER performance (Ej = 10 = 1.557V). As a cathode catalyst for zinc-air batteries, it showed 111mW·cm -2 The Fe@Co / CNNTs catalyst exhibits a high power density and long-term stability of 200 hours. Compared with precious metals, the Fe@Co / CNNTs catalyst demonstrates potential advantages in cost-effectiveness and catalytic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Structural characterization diagrams of Co / CNNs, Co / CNNTs, and Fe@Co / CNNTs samples; (A) Comparison of XRD patterns of Co / CNNs, Co / CNNTs, and Fe@Co / CNNTs samples; (B) Comparison of confocal Raman spectra of Co / CNNs and Fe@Co / CNNTs samples;

[0022] Figure 2 The adsorption and desorption curves and specific surface area diagrams of Co / CNNs and Fe@Co / CNNTs; (A) Comparison of N2 adsorption and desorption curves; (B) Comparison of BET specific surface areas;

[0023] Figure 3 The morphology of the samples is characterized; SEM images of (A) Co / CNNs, (B) Co / CNNTs, (C) (D) Fe@Co / CNNTs samples;

[0024] Figure 4The morphology characterization diagram of the Fe@Co / CNNTs sample; (A) TEM image at low magnification, (B)(C) EDS Mapping images of C, N, Co, and Fe, (D)(E)(F) HRTEM images under high-resolution transmission electron microscopy;

[0025] Figure 5 Figure 3. Ring current and disk current diagrams of the LSV curves of Co / CNNs, Co / CNNTs, Fe@Co / CNNTs, and Pt / C during the ORR process; (A) ORR ring-disk current curves of Co / CNNs, Co / CNNTs, Fe@Co / CNNTs, and Pt / C, (B) Comparison of hydrogen peroxide selectivity, (C) Comparison of electron transfer number, (D) OER curves of Co / CNNs, Co / CNNTs, Fe@Co / CNNTs, and IrO2, (E) Cdl curve, (F) ORR performance comparison before and after 5000 cycles, (G) OER performance comparison before and after 5000 cycles, (H) Comparison of methanol resistance of materials;

[0026] Figure 6 Performance test diagram of Fe@Co / CNNTs and Pt / C-IrO2 catalysts as cathode catalysts for zinc-air batteries; (A) open circuit voltage test, (B) power density test, and (C) long cycle charge and discharge test. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the embodiments of the present invention more clearly understood, the spirit of the contents disclosed in the present invention will be described in detail below. After understanding the embodiments of the contents of the present invention, any technician in the relevant technical field can change and modify the contents of the present invention based on the techniques taught by the contents of the present invention without departing from the spirit and scope of the contents of the present invention.

[0028] The exemplary embodiments of the present invention and the description thereof are used to explain the present invention but are not intended to limit the present invention.

[0029] Example

[0030] 1. Experimental Methods

[0031] 1.1 Preparation of materials

[0032] First, 6g of urea (Urea), 4g of dicyandiamide (DCDA) and 100mg of cobalt chloride were dissolved in 30mL of deionized water solution, quickly cooled with liquid nitrogen and placed in a freeze dryer for drying. The dried sample was placed in a muffle furnace and heated to 550℃ at a heating rate of 5℃ / min under air, and kept warm for two hours to obtain graphite phase carbon nitride. Then, the graphite phase carbon nitride was secondary sintered in an argon-hydrogen mixed atmosphere at a heating rate of 10℃ / min, raised to 520℃ and quickly cooled to obtain graphite phase carbon nitride nanotubes (CNNTs). Finally, Fe was modified on the obtained graphite phase carbon nitride nanotubes. 3+ The Fe@Co / CNNTs catalyst was obtained by drying. CNNs without metal addition and Co / CNNTs catalyst modified with Co alone were used as comparison samples.

[0033] 1.2 Characterization of materials

[0034] The sample morphology was characterized using a scanning electron microscope (SEM) and a transmission microscope (TEM), both Apero S and FEI Tecnai F30, respectively. Co and Fe content was analyzed using an iCAPQc inductively coupled plasma mass spectrometer (ICP-MS). X-ray diffraction (XRD) analysis of the crystal structure was performed using an X'Pert PRO diffractometer with a Cu Kα radiation source (λ = 0.154 nm). Nitrogen adsorption-desorption specific surface area of the samples was determined using a Micromeritics ASAP 2460 instrument.

[0035] 1.3 Electrochemical performance test of samples

[0036] Preparation of catalyst ink and electrode treatment for electrochemical performance testing: 2.5 mg of catalyst and 2.5 mg of conductive carbon black were added to 1000 μL of isopropanol solution and 10 μL of Nafion solution and sonicated for 120 minutes to obtain a uniformly mixed ink solution. The resulting solution was evenly pipetted onto the polished electrode surface and then dried in a 35°C oven. The catalyst loading was controlled to 0.2 mg cm -2 Electrochemical performance tests were performed on a CHI760 workstation using a three-electrode system consisting of a working electrode, a reference electrode (saturated calomel electrode), and a counter electrode (platinum sheet). The conversion rule between RHE (reversible hydrogen electrode) and test potential is as follows:

[0037] Evs RHE=Evs SCE+0.05916×pH+0.242V

[0038] The four-electron oxidation (4e - The ORR) test was carried out with a rotating disk electrode speed of 1600 rpm. The scanning speed was 5 mV / s, and the scanning interval was 0.2 V-1.1 V (vs RHE). The oxygen evolution reaction (OER) test was carried out in 1 M KOH with a scanning speed of 5 mV / s, and the scanning interval was 1.23 V-1.8 V (vs RHE). At the same time, different points were uniformly selected for CV testing within the scanning speed range of 20-180 mV / s, and the dual capacitance value of the material was calculated. In the zinc air assembly process, an air electrode was used as the cathode, and 1 mg of the catalyst was dissolved in isopropanol and 5% Nafion solution, and the sample was dropped on the carbon cloth. The loading area was guaranteed to be 1 mg cm -2 , assembled at the battery cathode. A 0.3mm zinc sheet was used as the anode. The electrolyte was 6 mol / L KOH and 0.2 mol / L zinc acetate solution.

[0039] 2. Experimental Results

[0040] like Figure 1 The following is the XRD characterization of Co / CNNs, Co / CNNTs and Fe@Co / CNNTs samples. The diffraction peaks of Co / CNNs at 13.4° and 27.5° correspond to the (100) and (002) diffraction planes of graphitic carbon nitride (PDF#87-1526), respectively, which correspond to the interplanar structure and surface graphite layer of the continuous heptane network of graphitic carbon nitride. However, after the sample was subjected to secondary sintering, the structure of the material changed. The C (002) crystal plane at 27.6° and the carbon (100) crystal plane at 42.5° illustrate the crystallinity of graphitic carbon nitride nanotubes. The appearance of the C peak, scanning electron microscopy scanning and transmission microscopy morphology all indicate the successful synthesis of graphitic carbon nitride nanotubes. The diffraction peaks at 44.3°, 51.5°, and 75.8° are attributed to the (111), (200), and (220) crystal planes of metallic Co (PDF#89-4307), respectively. The carbon nanotube-encapsulated metallic Co exhibits not only good crystallinity but also abundant structural defects in localized regions. This characteristic can expose more catalytic sites, accelerate electron transfer during electrochemical processes, and thus enhance catalytic performance. Figure 1 The Raman spectrum of B shows that the ID / IG ratio of Fe@Co / CNNTs after secondary sintering is 0.97, while the Raman spectrum of Co / CNNTs after only one sintering does not show D peak and G peak. This indicates that the graphite phase carbon nitride nanotubes exhibit a higher degree of graphitization from the graphite phase carbon nitride sintered once to the graphite phase carbon nitride nanotubes sintered twice, which makes the material have higher catalytic activity and is more conducive to the ORR and OER reactions.

[0041] like Figure 2 The specific surface area of the generated graphite phase carbon nitride nanotubes was determined by nitrogen isothermal adsorption-desorption curve. Figure 2 A It can be observed that the nitrogen adsorption and desorption curves of Co / CNNs and Fe@Co / CNNT catalysts have obvious adsorption hysteresis loops, which are typical type IV isotherms. Figure 2 As shown in B, the BET specific surface areas of Co / CNNs and Fe@Co / CNNTs are 74.472 m 2 / g and 270.652m 2 / g. This shows that the specific surface area of graphite phase carbon nitride synthesized using different precursors (in the present invention, a certain proportion of urea is introduced on the basis of dicyandiamide) is increased by nearly 15 times. At the same time, the specific surface area of graphite phase carbon nitride nanotubes formed after secondary sintering is nearly 4 times greater than that of graphite phase carbon nitride after primary sintering. The specific surface area determines the activity and rate of the electrocatalyst. The present invention obtains a graphite phase carbon nitride nanotube material with a larger specific surface area through simple morphology regulation, which has better electrochemical performance, is more conducive to the exposure of active sites, and thus accelerates the reaction rate.

[0042] The morphology of the prepared materials was characterized by SEM and TEM. Figure 3 The SEM image of the sample is shown in FIG. Figure 3 As shown in A, the morphology still shows a block structure, and no graphite phase carbon nitride nanotubes are observed. After secondary sintering in an argon-hydrogen mixed gas, the morphology is transformed from the original block to graphite phase carbon nitride nanotubes ( Figure 3 B). Fe@Co / CNNTs (e.g. Figure 3 C and D) and Co / CNNTs exhibit the same morphology. The formation of graphitic carbon nitride nanotubes is related to the addition of transition metals and reducing atmosphere. The thermal decomposition of urea and dicyandiamide alone cannot form graphitic carbon nitride nanotubes.

[0043] At the same time, in order to explore the microscopic morphology of the synthesized graphite phase carbon nitride nanotubes, we performed TEM characterization of the material. Figure 4 As shown in A, 3-8nm Co nanoparticles are encapsulated in 5-20nm graphite phase carbon nitride nanotubes with a wall thickness of 1-2nm. The HRTEM image shows the presence of Co nanoparticles. Figure 4As shown in Figures D and 4E, there are lattice fringes with lattice spacings of 0.287nm, 0.216nm, and 0.20nm, respectively, corresponding to the (200), (220), and (111) crystal planes of Co. The wrapping of metal particles by graphene-phase carbon nitride nanotubes gives them good stability and a large specific surface area, exposing more active sites, which gives the material better electrocatalytic performance. At the same time, EDSMapping analysis of graphene-phase carbon nitride nanotubes was performed, as shown in Figure 4E. Figure 4 The C, N, Co, and Fe nanoparticles shown in B and C are uniformly dispersed without agglomeration, which indicates that the graphite phase carbon nitride nanotubes synthesized by the present invention are uniform in size. At the same time, the present invention found that the order of the graphite layer is not high ( Figure 4 F), indicating that the edges of the graphite layers are more exposed on the surface of the graphitic carbon nitride nanotubes than the basal plane of the graphite layers. This allows the carbon atoms to be easily polarized and serve as active sites, thereby improving the electrocatalytic performance.

[0044] Figure 5 A shows the ring current and disk current of the LSV curves of Co / CNNs, Co / CNNTs, Fe@Co / CNNTs and Pt / C during the ORR process. It can be seen that the limiting current density of the Fe@Co / CNNTs catalyst is closer to that of commercial precious metal materials. At the same time, the half-wave potential of the Fe@Co / CNNTs material is 0.84V, which is better than the half-wave potential of Co / CNNs (0.713V), Co / CNNTs (0.828V) and Pt / C (0.83V). The hydrogen peroxide selectivity was calculated by the ring-disk current, as shown in Figure 2. Figure 5 The two-electron hydrogen peroxide selectivity of Fe@Co / CNNTs shown in B is the lowest (~18.5% at 0.6 V), which is significantly lower than that of Co / CNNTs (~22%) and Co / CNNs (36%). This indicates that Fe@Co / CNNTs prefers 4e hydrogen peroxide to Co / CNNTs and Co / CNNs. - Reaction. Figure 5 As shown in C, during the ORR process, the average electron transfer number (n) of Fe@Co / CNNTs is 3.8, that of Co / CNNTs is 3.7, and that of Co / CNNs is 3.4. The electron transfer number of Fe@Co / CNNTs is closer to 4, so it can be determined that Fe@Co / CNNs is more inclined to 4e - Catalyst for oxygen reduction reactions.

[0045] like Figure 5Figure D shows the LSV curves of the materials during the OER process. Fe@Co / CNNTs exhibited the best OER performance (1.557V) at a current density of 10mAcm-2, outperforming Co / CNNs (1.834V), Co / CNNTs (1.625V), and the precious metal IrO2 (1.654V). This indicates that Fe is a good OER reaction active site, and the introduction of Fe increases the chemical valence of Co, which is more conducive to the OER reaction. Figure 5 E shows that the Cdl values of Co / CNNs, Co / CNNTs, Fe@Co / CNNTs and IrO2 are 2.49 mF·cm -2 、26.8mF·cm -2 、26.8mF·cm -2 and 13.9 mF·cm -2 This shows that the electrochemical specific surface area of the material is increased by converting graphitic carbon nitride into graphitic carbon nitride nanotubes. Figure 5 By comparing the LSV curves before and after 5000 CV cycles, F and G show that the Fe@Co / CNNTs catalyst has better stability than precious metals during ORR and OER reactions, which provides greater possibilities for the commercial application of materials. Figure 5 H demonstrated the material's methanol resistance. Using 0.1M KOH as the electrolyte, a current-time test was first conducted. At 1000 seconds, methanol was injected into the solution to maintain a methanol concentration of 3 mol / L. The Fe@Co / CNNTs material showed no significant change after the addition of methanol, remaining stable at around 90%. However, the current of the pt / C catalyst dropped rapidly by 40% upon the instantaneous addition of methanol, then stabilized at around 60% after 100 seconds. This demonstrates that the Fe@Co / CNNTs catalyst has superior methanol resistance compared to precious metal catalysts and is more efficient in practical applications.

[0046] In order to further explore the application potential of Fe@Co / CNNTs composite materials in practical energy conversion systems, we applied them to metal-air batteries to evaluate their performance. Fe@Co / CNNTs and Pt / C-IrO2 were evenly dropped on the surface of carbon paper to ensure that the loading area was 1 mg cm -2 , and then assemble with carbon paper as the positive electrode and zinc sheet as the negative electrode. Figure 6 As shown in A, the open circuit voltage of the zinc-air battery is 1.487V, which is consistent with the theoretical voltage. Figure 6 As shown in B, the power density of the zinc-air battery assembled with Fe@Co / CNNTs catalyst reaches 111 mW·cm -2 , which is better than commercial Pt / C-IrO2 (90mW·cm -2). In addition, when conducting rigorous durability evaluation of the assembled zinc-air battery, we conducted a long-term charge-discharge cycle test. The results showed that the zinc-air battery assembled with Fe@Co / CNNTs catalyst can maintain good working condition and high energy conversion efficiency during the charge-discharge test for more than 200 hours. In contrast, the zinc-air battery assembled using commercial Pt / C-IrO2 catalyst showed significant performance degradation after about 50 hours of cycling ( Figure 6 C), and could not maintain normal operation. This indicates that the Fe@Co / CNNTs catalyst exhibits better stability in this battery system than the precious metal Fe@Co / CNNTs catalyst.

[0047] The present invention uses a secondary sintering method to manipulate the composition and morphology of graphite-phase carbon nitride to produce a bimetallic composite Fe@Co / CNNTs graphite-phase carbon nitride nanotube catalyst. The synergistic effect of the graphite-phase carbon nitride nanotubes and the two metals gives the catalyst excellent ORR performance (E1 / 2 = 0.84V) and OER performance (Ej = 10 = 1.557V), as well as extremely high stability. When used as a cathode catalyst in zinc-air batteries, it exhibited a power conversion efficiency of 111mW·cm -2 The Fe@Co / CNNTs catalyst demonstrated a power density of 1.5 GHz and long-term stability of 200 hours. Compared to precious metals, the Fe@Co / CNNTs catalyst demonstrated potential advantages in cost-effectiveness and catalytic performance. Furthermore, the identification of active sites revealed their mechanism of action, providing important experimental support for the precise control of specific reaction processes and, consequently, for improving electrochemical reaction efficiency. This provides strong data support and theoretical basis for further promoting its practical application in clean energy technologies such as metal-air batteries.

Claims

1. A method for preparing Co, Fe bimetallic doped graphite phase carbon nitride high specific area nanotubes for zinc-air batteries, characterized in that The preparation method is as follows: Step 1: dissolving urea, dicyandiamide and cobalt chloride in deionized water, cooling with liquid nitrogen, and then freeze-drying; Step 2: Place the dried sample in a muffle furnace and sinter it in an air atmosphere to obtain graphite carbon nitride; Step 3: Secondary sintering of the graphite phase carbon nitride in an argon-hydrogen mixed atmosphere to obtain graphite phase carbon nitride nanotubes (CNNTs); Step 4: Modify Fe on graphite phase carbon nitride nanotubes CNNTs 3+ , and dried to obtain Fe@Co / CNNTs catalyst.

2. The method for preparing Co and Fe bimetallic doped graphite carbon nitride high specific area nanotubes for zinc-air batteries according to claim 1, characterized in that The mass volume ratio of urea, dicyandiamide, cobalt chloride and deionized water described in step 1 is (5-7) g: (3-5) g: 0.1 g: (20-40) mL.

3. The method for preparing Co and Fe bimetallic doped graphite carbon nitride high specific area nanotubes for zinc-air batteries according to claim 1 or 2, characterized in that The mass volume ratio of urea, dicyandiamide, cobalt chloride and deionized water described in step 1 is 6g:4g:0.1g:30mL.

4. The method for preparing Co and Fe bimetallic doped graphite carbon nitride high specific area nanotubes for zinc-air batteries according to claim 1, characterized in that The sintering conditions described in step 2 are: heating to 540-560° C. at a heating rate of 3-7° C. / min and keeping at that temperature for 1-3 hours.

5. The method for preparing Co and Fe bimetallic doped graphite carbon nitride high specific area nanotubes for zinc-air batteries according to claim 1 or 4, characterized in that The sintering conditions described in step 2 were as follows: heating to 550°C at a rate of 5°C / min and holding for 2 h.

6. The method for preparing Co and Fe bimetallic doped graphite carbon nitride high specific area nanotubes for zinc-air batteries according to claim 1, characterized in that The secondary sintering conditions described in step 3 are: heating to 500-540°C at a heating rate of 5-15°C / min.

7. The method for preparing Co, Fe bimetallic doped graphite carbon nitride high specific area nanotubes for zinc-air batteries according to claim 1 or 6, characterized in that The temperature was raised to 520°C at a heating rate of 10°C / min.

8. The method for preparing Co and Fe bimetallic doped graphite carbon nitride high specific area nanotubes for zinc-air batteries according to claim 1, characterized in that The Fe-modified graphite phase carbon nitride nanotubes CNNTs described in step 4 3 + Specifically, graphite phase carbon nitride nanotubes and ferric chloride are added to ethanol in a ratio of 2:1 to 1:2, stirred evenly, and freeze-dried for one day to obtain Fe@Co / CNNTs catalyst material.

9. Application of Co, Fe bimetallic doped graphite carbon nitride high specific area nanotubes prepared as claimed in claim 1, characterized in that Co and Fe bimetallic doped graphitic carbon nitride high-area nanotubes as cathode catalysts for zinc-air batteries.

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