Self-supporting electrode and preparation method and application thereof

Abstract

The invention belongs to the field of air electrode materials of zinc-air batteries, and particularly relates to a self-supporting electrode and a preparation method and application thereof. The invention discloses a self-supporting electrode. The self-supporting electrode comprises a conductive substrate, a nitrogen-doped carbon nanotube and FeNi3 particles distributed in the nanotube, the nitrogen-doped carbon nanotubes grow on the surface of the conductive substrate. According to the self-supporting electrode provided by the invention, nickel has high OER catalytic activity, meanwhile, iron shows high ORR catalytic activity, and an efficient bifunctional catalyst is obtained by adding heteroatom iron into a nickel-based material under a synergistic effect; ferronickel metal is distributed in the nitrogen-doped carbon nanotube, so that metal particle aggregation in a high-temperature synthesis process or decomposition failure under an extreme working condition is effectively prevented; the self-supporting electrode is high in electrochemical activity, good in cycle performance, good in flexibility and portability, stable and excellent in battery performance and excellent in mechanical performance.

Description

Technical Field

[0001] The invention belongs to the field of air electrode materials for zinc-air batteries, and in particular relates to a self-supporting electrode and a preparation method and application thereof. Background Art

[0002] Renewable energy is becoming an important alternative to traditional fossil fuels, but it also causes a mismatch between energy demand and energy demand. The most effective and feasible solution is to develop new energy storage devices and efficient conversion technologies. Lithium-ion batteries are widely used in various electronic products. However, due to the high energy density of rechargeable lithium-ion batteries (200–250Wh·kg -1 ) has insufficient energy density, high cost, limited lithium ore resources, and battery morphology, which restrict its further development and application. Therefore, energy storage devices with high mechanical flexibility, light weight, safety and reliability are the rigid needs of the next generation of electronic devices. Among them, zinc-air batteries (ZABs) have high zinc abundance, environmental friendliness, and excellent theoretical energy density (up to 1084Wh kg -1 ), low price, recyclability and environmental protection have attracted much attention from researchers. Metallic zinc has good compatibility with aqueous electrolytes. Compared with non-aqueous organic electrolytes, it not only provides higher ionic conductivity but is also safer.

[0003] So far, flexible ZABs have been plagued by problems such as low power density, poor cycling stability, and unsatisfactory mechanical stability due to the slow oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) on the air electrode. Commercial ZAB air electrodes mostly use precious metals such as Pt and Ru as catalysts. Although they exhibit excellent catalytic performance, they have problems such as poor bifunctional catalytic performance and high cost. Therefore, it is very necessary to explore bifunctional flexible oxygen electrodes with high catalytic activity and excellent stability. In recent years, efficient transition metal (cobalt, nickel, iron, copper, etc.)-based catalysts are one of the best candidates to replace precious metal catalysts to achieve ideal oxygen electrocatalytic reactions. Among them, bimetallic iron-nickel (FeNi) alloys have shown great potential as bifunctional oxygen catalysts. Generally speaking, Ni species have high OER catalytic activity, while Fe species exhibit high ORR catalytic activity. Due to the synergistic effect between metals and the asymmetric electron distribution between metal alloys, the adsorption and desorption characteristics of key oxygen-containing intermediates at the catalytic active center can be significantly improved. Moreover, if the transition metals can be effectively dispersed on suitable nitrogen-doped porous conductive carbon supports, that is, the M–N–C type catalyst can be constructed, the M–N–C type catalyst based on metal clusters will be further strengthened. xThe electron interaction between M–N–C and the bond of M–N–C can be rationally adjusted to reasonably adjust the local coordination environment of the M–N–C active site, promote the electron transfer and charge transport on the surface / interface, and enhance the oxygen catalytic activity. On the other hand, carbon nanotubes (CNTs) doped with transition metals and heteroatoms (such as nitrogen, oxygen, sulfur, etc.) are considered to be an effective electrocatalyst for catalyzing ORR / OER. However, since metal@CNT catalysts are prone to metal particle aggregation during high-temperature synthesis or decomposition failure under extreme working conditions, the challenge lies in efficiently dispersing high-density active metal catalyst particles in the CNT matrix. On the other hand, polymer binders and conductive additives are used in conventional oxygen electrodes prepared by slurry coating. These electrochemically inert substances not only cover the reaction active sites to a certain extent, but also reduce the close contact between the catalyst particles and the current collector, thereby increasing the internal resistance of the electrode reaction. In order to avoid the use of binders and additional conductive additives and further enhance the interfacial contact between the catalyst and the conductive support, in situ growth of highly active catalysts on flexible conductive substrates to construct self-supporting oxygen electrodes and extremely high-performance flexible zinc-air batteries is a promising solution. Therefore, developing, designing and synthesizing bifunctional self-supporting catalysts / electrodes for efficient OER / ORR catalysis and studying their actual performance in zinc-air batteries is one of the important ways to improve the performance and application value of zinc-air batteries and solve the current mismatch in energy demand. Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned deficiencies and provide a self-supporting electrode and a preparation method and application thereof.

[0005] In a first aspect, a self-supporting electrode adopts the following technical solution:

[0006] A self-supporting electrode comprises a conductive substrate and nitrogen-doped carbon nanotubes and FeNi3 particles distributed inside the nanotubes; the nitrogen-doped carbon nanotubes grow on the surface of the conductive substrate.

[0007] Furthermore, the conductive substrate is any one of carbon paper, carbon cloth, nickel foam, and copper foam.

[0008] Furthermore, the diameter of the nitrogen-doped carbon nanotubes is 20 nm to 90 nm, and the wall thickness is 2 nm to 4 nm.

[0009] Furthermore, the particle size of the FeNi3 particles is 10nm to 30nm.

[0010] In a second aspect, a method for preparing a self-supporting electrode adopts the following technical solution:

[0011] A method for preparing a self-supporting electrode comprises the following steps:

[0012] Dissolving iron salt, nickel salt, ammonium fluoride and urea in water to form an iron-nickel precursor solution; subjecting a conductive substrate to a solvothermal reaction in the iron-nickel precursor solution to obtain a FeNi-OH electrode;

[0013] Mixing a nickel salt solution with a ferrocyanate solution to form a Prussian blue analog precursor solution; subjecting the FeNi-OH electrode to chemical deposition self-assembly in the Prussian blue analog precursor solution to obtain a FeNiPBA / FeNi-OH electrode;

[0014] The FeNiPBA / FeNi-OH electrode is carbonized at high temperature in an inert atmosphere using a nitrogen source as an evaporation source to obtain the self-supporting electrode.

[0015] Furthermore, in the iron-nickel precursor solution, the molar ratio of nickel salt, iron salt, urea and ammonium fluoride is 1:0.5-1.5:3-8:1-3.

[0016] Furthermore, in the Prussian blue precursor solution, the mixing volume ratio of the nickel salt solution to the ferricyanide solution is 1:0.8-1.2;

[0017] The nickel salt solution also includes citrate, and the molar ratio of the nickel salt to the citrate is 1:1.5-3.0.

[0018] Further, the iron salt and nickel salt include one or more of nitrate, sulfate, and acetate;

[0019] The citrate includes one of potassium citrate and sodium citrate;

[0020] The ferrocyanide includes one of potassium ferrocyanate and sodium ferrocyanate;

[0021] The nitrogen source includes one or more of dicyandiamide, urea, melamine, and cyano derivatives.

[0022] Furthermore, the temperature of the solvent thermal reaction is 100°C to 150°C, and the reaction time is 6h to 10h;

[0023] The chemical deposition self-assembly time is 12h to 36h;

[0024] The high temperature carbonization is carried out at 600° C. to 900° C. for 0.5 h to 3 h.

[0025] In a third aspect, an application of a self-supporting electrode adopts the following technical solution:

[0026] An application of a self-supporting electrode, wherein the self-supporting electrode is applied to electrode materials of liquid zinc-air batteries, all-solid-state zinc-air batteries, and flexible wearable batteries.

[0027] Technical effects of the present invention:

[0028] The present invention provides a self-supporting electrode, wherein nickel has high OER catalytic activity, and iron exhibits high ORR catalytic activity. Under synergistic effect, heteroatom iron is added to the nickel-based material to obtain a highly efficient bifunctional catalyst; nickel-iron metal is distributed inside nitrogen-doped carbon nanotubes, which effectively prevents metal particle aggregation during high-temperature synthesis or decomposition failure under extreme working conditions; the self-supporting electrode has high electrochemical activity, good cycle performance, good flexibility and portability, and has stable and excellent battery performance and excellent mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Electrode OER performance test diagram provided for Example 1 and Comparative Examples 1-3;

[0030] Figure 2 The electrode ORR performance test diagram provided for Example 1 and Comparative Examples 1-3;

[0031] Figure 3 XRD spectra of the electrodes provided for Example 1 and Comparative Examples 1-2;

[0032] Figure 4 SEM images of the electrodes provided for Example 1 and Comparative Examples 1-2;

[0033] Figure 5 TEM images of the electrodes provided for Example 1 and Comparative Example 1;

[0034] Figure 6 The electrode cyclic scanning voltammetry test diagram provided for Example 1 and Comparative Examples 1-2;

[0035] Figure 7 Liquid zinc-air battery charge and discharge cycle performance test diagram provided for Application Example 1;

[0036] Figure 8 The voltage-specific capacity curve of the liquid zinc-air battery charge and discharge provided in Application Example 1;

[0037] Fig. 9 Test diagram of the solid-state zinc-air battery lighting the LED light board provided for Application Example 2. DETAILED DESCRIPTION

[0038] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present application will be further described in detail below in conjunction with the accompanying drawings. The described embodiments should not be regarded as limiting the present invention. All other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention.

[0039] In the following description, reference is made to "some embodiments", which describe a subset of all possible embodiments, but it is understood that "some embodiments" may be the same subset or different subsets of all possible embodiments, and may be combined with each other without conflict. Unless otherwise defined, all technical and scientific terms used in the embodiments of the present invention have the same meaning as those commonly understood by those skilled in the art to which the embodiments of the present invention pertain. The terms used in the embodiments of the present invention are only for the purpose of describing the embodiments of the present invention and are not intended to limit the present invention.

[0040] Those skilled in the art should understand that in the following description of the embodiments of the present invention, the order of serial numbers does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0041] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "an" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0042] It will be appreciated by those skilled in the art that the numerical ranges in the embodiments of the present invention are to be understood as also specifically disclosing each intermediate value between the upper and lower limits of the range. Each smaller range between the intermediate values ​​in any stated value and stated range and any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded in the range.

[0043] Unless otherwise specified, the technical / scientific terms used herein have the same meanings as those generally understood by those skilled in the art in the art. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the embodiments or test cases of the present invention. All documents mentioned in this specification are generally incorporated by reference to disclose and describe methods and / or materials related to the documents. In the event of a conflict with any incorporated document, the content of this application shall prevail.

[0044] It should be noted that all raw materials and / or reagents in the examples of the present invention are purchased on the market or prepared according to conventional methods well known to those skilled in the art.

[0045] This embodiment provides a self-supporting electrode, which includes a conductive substrate and nitrogen-doped carbon nanotubes and FeNi3 particles distributed inside the nanotubes; the nitrogen-doped carbon nanotubes grow on the surface of the conductive substrate.

[0046] Through the introduction of nitrogen-doped carbon nanotubes and the embedding of FeNi3 particles, the electrode material exhibits excellent electrocatalytic performance and good conductivity. Nitrogen doping not only increases the specific surface area and active sites of carbon nanotubes, but also improves the electrocatalytic efficiency by changing the electronic structure; at the same time, FeNi3 particles are distributed inside the carbon nanotubes, preventing particle agglomeration and improving the utilization rate of the catalyst. In addition, the self-supporting structure avoids the use of adhesives, reduces interfacial resistance, and enhances structural stability, making the electrode lighter and more flexible, suitable for a variety of electrochemical application scenarios. Overall, this electrode material achieves efficient electrocatalytic performance and long-term stable operation through the optimization of materials and structures.

[0047] In some embodiments, the conductive substrate is any one of carbon paper, carbon cloth, nickel foam, and copper foam.

[0048] These conductive substrate materials each have their own advantages and can provide good conductivity and mechanical support, further improving the overall performance of the self-supporting electrode. Carbon paper and carbon cloth have high conductivity and flexibility, which help to form a stable electrode structure; nickel foam and copper foam have a large specific surface area and good mechanical strength, which are suitable for efficient electrochemical reactions. By rationally selecting conductive substrate materials, the performance of the electrode can be further optimized to meet the needs of different electrochemical applications.

[0049] In some embodiments, the diameter of the nitrogen-doped carbon nanotubes is 20 nm to 90 nm, and the wall thickness is 2 nm to 4 nm.

[0050] Controlling the diameter and wall thickness of nitrogen-doped carbon nanotubes gives carbon nanotubes a high specific surface area and ideal electrochemical performance. Smaller diameters help increase surface active sites, thereby improving catalytic efficiency; moderate wall thickness ensures the structural strength and conductivity of carbon nanotubes, while effectively avoiding material waste caused by excessive wall thickness. Precise structural design further enhances the overall performance of the self-supporting electrode and meets the needs of efficient electrochemical applications.

[0051] In some embodiments, the FeNi3 particles have a particle size of 10 nm to 30 nm.

[0052] The particle size range of FeNi3 particles helps to evenly distribute inside the nitrogen-doped carbon nanotubes, thereby maximizing the provision of active sites and improving the catalytic performance of the electrode. The fine particle size not only improves the catalytic activity of the material, but also effectively prevents particle agglomeration, ensuring the long-term stability and high efficiency of the electrode. This nanoscale structural design further optimizes the performance of the self-supporting electrode, making it more efficient and reliable in electrochemical applications.

[0053] This embodiment provides a method for preparing a self-supporting electrode, comprising the steps of:

[0054] Dissolving iron salt, nickel salt, ammonium fluoride and urea in water to form an iron-nickel precursor solution; subjecting a conductive substrate to a solvothermal reaction in the iron-nickel precursor solution to obtain a FeNi-OH electrode;

[0055] Mixing a nickel salt solution with a ferrocyanate solution to form a Prussian blue analog precursor solution; subjecting the FeNi-OH electrode to chemical deposition self-assembly in the Prussian blue analog precursor solution to obtain a FeNiPBA / FeNi-OH electrode;

[0056] The FeNiPBA / FeNi-OH electrode is carbonized at high temperature in an inert atmosphere using a nitrogen source as an evaporation source to obtain the self-supporting electrode.

[0057] By immersing the conductive substrate in an iron-nickel precursor solution for a solvothermal reaction, the hydroxides of Fe and Ni are uniformly deposited on the surface of the conductive substrate to form a preliminary electrode material, which provides an ideal conductive substrate for the subsequent PBA self-assembly.

[0058] FeNiPBA is self-assembled on the FeNi-OH electrode by chemical deposition to form a multilayer structure, which provides more active sites for the electrode material, increases its specific surface area, and improves the electrocatalytic performance.

[0059] When nitrogen source is used as evaporation source, high-temperature carbonization not only converts PBA into nitrogen-doped carbon nanotubes, but also promotes the uniform distribution of FeNi3 particles inside the nanotubes, forming a self-supporting electrode with good conductivity and catalytic activity.

[0060] Through solvothermal reaction and chemical deposition self-assembly steps, a uniform Prussian blue analogue (FeNiPBA) was formed on the surface of the FeNi-OH electrode, providing a rich precursor for the subsequent high-temperature carbonization of nitrogen-doped carbon nanotubes and FeNi3 particles.

[0061] During the high-temperature carbonization process, FeNiPBA is converted into FeNi3 particles embedded inside nitrogen-doped carbon nanotubes; this not only improves the conductivity of the electrode, but also prevents particle agglomeration by embedding the particles inside the carbon nanotubes, thus ensuring the long-term stability of the electrode.

[0062] In some embodiments, in the iron-nickel precursor solution, the molar ratio of nickel salt, iron salt, urea and ammonium fluoride is 1:0.5-1.5:3-8:1-3.

[0063] The molar ratio of nickel salt, iron salt, urea and ammonium fluoride in the iron-nickel precursor solution is 1:0.5~1.5:3~8:1~3, which enables the formation of a uniform and stable FeNi-OH electrode during the reaction and provides an ideal precursor for the subsequent chemical deposition and carbonization process. In addition, it can ensure the full reaction of nickel and iron ions in the solution, avoid incomplete reaction or uneven material caused by too high or too low concentration, and further optimize the structure and performance of the electrode.

[0064] Precise ratio and concentration control ensures the controllability of the reaction and the uniformity of the material, laying the foundation for the preparation of efficient and stable self-supporting electrodes. The resulting electrodes have excellent electrocatalytic properties and conductivity, and can perform well in a variety of electrochemical applications.

[0065] In some embodiments, in the Prussian blue precursor solution, the mixing volume ratio of the nickel salt solution to the ferricyanide solution is 1:0.8-1.2;

[0066] The nickel salt solution also includes citrate, and the molar ratio of the nickel salt to the citrate is 1:1.5-3.0.

[0067] The mixing volume ratio of the nickel salt solution and the ferricyanide solution in the Prussian blue analog precursor solution is 1:0.8-1.2. This helps to ensure that the two solutions are fully mixed, thereby promoting the uniform deposition of FeNiPBA. At the same time, citrate is also added to the nickel salt solution, and the molar ratio of nickel salt to citrate is 1:1.5-3.0. The addition of citrate can chelate nickel ions and adjust the pH value of the solution, thereby stabilizing the solution and promoting the formation of PBA.

[0068] The amount of ferrocyanate and nickel salt is matched to ensure the uniformity and sufficiency of the reaction. Through the control of ratio and concentration, the Prussian blue analogues are uniformly self-assembled on the surface of the FeNi-OH electrode to form a dense FeNiPBA layer, which lays a good foundation for the subsequent carbonization process.

[0069] Not only does it ensure the structural uniformity of the material and the controllability of the reaction, but it also optimizes the formation conditions of FeNiPBA through the introduction of citrate, ultimately improving the electrocatalytic performance and conductivity of the electrode material, ensuring its excellent performance in a variety of electrochemical applications.

[0070] In some embodiments, the iron salt and nickel salt include one or more of nitrate, sulfate, and acetate;

[0071] The citrate includes one of potassium citrate and sodium citrate;

[0072] The ferrocyanide includes one of potassium ferrocyanate and sodium ferrocyanate;

[0073] The nitrogen source includes one or more of dicyandiamide, urea, melamine, and cyano derivatives.

[0074] The nitrogen source will decompose and release nitrogen-containing compounds during the high-temperature carbonization process, which will further react with the carbon nanotube precursor to achieve nitrogen doping; nitrogen-doped carbon nanotubes not only improve the conductivity of the electrode, but also enhance the electrocatalytic performance of the electrode by introducing abundant active sites.

[0075] By selecting different nitrogen sources or their combinations, adjusting the degree and morphology of nitrogen doping, the final properties of the electrode material can be precisely controlled. This process ensures that the self-supporting electrode is structurally stable and functionally has efficient electrocatalytic activity and conductivity, enabling it to exhibit excellent performance in various electrochemical applications.

[0076] In some embodiments, the temperature of the solvothermal reaction is 100°C to 150°C, and the reaction time is 6h to 10h;

[0077] The chemical deposition self-assembly time is 12h to 36h;

[0078] The high temperature carbonization is carried out at 600° C. to 900° C. for 0.5 h to 3 h.

[0079] The solvent thermal reaction temperature is 100°C to 150°C, and the reaction time is 6h to 10h, which is conducive to the in-situ growth of FeNi hydroxide (FeNi-OH) nanostructures on the carbon cloth conductive substrate, providing a good foundation for subsequent chemical deposition self-assembly.

[0080] The chemical deposition self-assembly time is 12h to 36h, which can make FeNi Prussian blue analogue (FeNiPBA) adsorbed regularly on the FeNi-OH surface to form a good composite structure.

[0081] The high-temperature carbonization temperature is 600℃~900℃ and the holding time is 0.5h~3h, which is conducive to the in-situ growth of highly nitrogen-doped and oxygen-defective carbon nanotubes (NCNTs) on the FeNi-OH / FeNiPBA composite structure and encapsulating the FeNi3 nanoparticles therein to form a FeNi3@NCNTs self-supporting electrode.

[0082] Through solvothermal reaction, chemical deposition self-assembly and high-temperature carbonization process, a self-supporting structure of FeNi3@NCNTs with high nitrogen doping and rich oxygen defects was in situ grown on a carbon cloth conductive substrate, giving the electrode excellent bifunctional catalytic activity, outstanding stability and good mechanical flexibility, thus showing broad application prospects in fields such as flexible zinc-air batteries.

[0083] This embodiment provides an application of a self-supporting electrode, which is applied to electrode materials of liquid zinc-air batteries, all-solid-state zinc-air batteries, and flexible wearable batteries.

[0084] The self-supporting structure design avoids the use of binders and conductive additives and can be used directly as an electrode, improving conductivity and catalytic performance.

[0085] The self-supporting electrode material has a carbon nanotube structure with high nitrogen doping and oxygen defects, which endows it with excellent bifunctional catalytic activity.

[0086] The self-supporting electrode material is grown in situ on a flexible conductive substrate and has good mechanical flexibility. It can be used to prepare flexible zinc-air batteries with stable and excellent battery performance.

[0087] In summary, the self-supporting electrode material has broad application prospects in the fields of liquid zinc-air batteries, all-solid-state zinc-air batteries, and flexible wearable batteries, providing a high-performance, high-mechanically flexible bifunctional oxygen catalyst solution.

[0088] Example

[0089] The conductive substrate used in the following embodiments is carbon cloth, and the carbon cloth pretreatment steps are as follows:

[0090] Cut the carbon cloth into 5×3cm 2 The cut carbon cloth was ultrasonically cleaned in acetone for 20 minutes to remove organic residues on the surface of the carbon cloth, and then the acetone was poured out and anhydrous ethanol was added for ultrasonic cleaning for 20 minutes. During this period, fresh ethanol needs to be constantly replaced to clean the residual acetone. Finally, the carbon cloth was dried in an oven overnight.

[0091] Place the dried carbon cloth into a mixed solution of sulfuric acid and nitric acid in a volume ratio of 1:1 and stir. Treat it at a temperature of 60℃~100℃ for 2~10h. After the solution cools to room temperature, take out the carbon cloth and wash it repeatedly with deionized water and anhydrous ethanol until it is neutral. Finally, dry it overnight and it can be used.

[0092] The electrochemical catalytic activities of the electrodes in the following examples were evaluated using a typical three-electrode system, and all potentials mentioned were calibrated to the standard hydrogen potential (RHE).

[0093] Example 1

[0094] Embodiment 1 provides a self-supporting electrode, which includes a carbon cloth substrate and nitrogen-doped carbon nanotubes and FeNi3 particles distributed inside the nanotubes; the nitrogen-doped carbon nanotubes grow on the surface of the carbon cloth conductive substrate.

[0095] The diameter of the nitrogen-doped carbon nanotubes is 20nm to 90nm, and the wall thickness is 2nm to 4nm; the particle size of the FeNi3 particles is 10nm to 30nm.

[0096] Embodiment 1 also provides a method for preparing a self-supporting electrode, comprising the following steps:

[0097] (1) Preparation of FeNi-OH: 1 mmol nickel nitrate hexahydrate, 1 mmol ferric nitrate nonahydrate, 6 mmol urea and 2 mmol ammonium fluoride were dissolved in 35 mL deionized water to obtain a light green uniform solution; the mixed solution was poured into a 50 mL reactor, and the pretreated carbon cloth was tilted into the reactor to carry out a solvothermal reaction at 120°C for 8 h. After the reaction was completed and the carbon cloth was naturally cooled to room temperature, the carbon cloth was taken out, ultrasonically cleaned in deionized water for 1 min, and then rinsed with deionized water and anhydrous ethanol, placed flat in a culture dish, and dried in an oven at 60°C overnight to obtain a FeNi-OH electrode.

[0098] (2) Preparation of FeNiPBA / FeNi-OH: 0.7 mmol of nickel nitrate hexahydrate and 1.4 mmol of sodium citrate were dissolved in 30 mL of deionized water to obtain a blue-green solution, which was labeled as solution A; 0.6 mmol of potassium ferrocyanide was dissolved in 30 mL of deionized water to obtain a yellow-red solution, which was labeled as solution B. While solution A was being stirred, solution B was slowly poured into the solution and stirred rapidly for 5 min to obtain a yellow-green solution. The FeNi-OH electrode was then placed in the yellow-green mixed solution. After standing for 24 h, the electrode was taken out and cleaned with deionized water, and dried in an oven at 60°C to obtain a FeNiPBA / FeNi-OH electrode.

[0099] (3) Preparation of FeNi3@NCNTs: The FeNiPBA / FeNi-OH electrode obtained above was placed flat on a plate containing 2 The carbon cloth was placed in a porcelain boat containing 0.13 g of dicyandiamide and placed in the center of a tube furnace at 5 °C min -1 At a heating rate of , the temperature was raised to 750 °C in a nitrogen atmosphere for high-temperature carbonization and insulation for 1 h. After the reaction was completed, it was naturally cooled to room temperature, and the sample was taken out to obtain a FeNi3@NCNTs electrode.

[0100] Example 2

[0101] Embodiment 2 provides a self-supporting electrode, which includes a carbon cloth substrate and nitrogen-doped carbon nanotubes and FeNi3 particles distributed inside the nanotubes; the nitrogen-doped carbon nanotubes grow on the surface of the carbon cloth conductive substrate.

[0102] The diameter of the nitrogen-doped carbon nanotubes is 30 to 90 nm, and the wall thickness is 2 to 3 nm; the particle size of the FeNi3 particles is 10 to 20 nm.

[0103] Embodiment 2 also provides a method for preparing a self-supporting electrode, comprising the following steps:

[0104] (1) Preparation of FeNi-OH: 1 mmol nickel nitrate hexahydrate, 0.5 mmol ferric nitrate nonahydrate, 3 mmol urea and 1 mmol ammonium fluoride were dissolved in 35 mL deionized water to obtain a light green uniform solution; the above solution was poured into a 50 mL reactor, and the pretreated carbon cloth was tilted into the reactor to carry out a solvothermal reaction at 100°C for 6 h. After the reaction was completed and naturally cooled to room temperature, the carbon cloth was taken out and ultrasonically cleaned in deionized water for 1 min, then rinsed with deionized water and anhydrous ethanol, placed flat in a culture dish, and dried in an oven at 60°C overnight to obtain a FeNi-OH electrode.

[0105] (2) Preparation of FeNiPBA / FeNi-OH: Dissolve 0.7mmol nickel nitrate hexahydrate and 1.5mmol potassium citrate in 30mL deionized water to obtain a blue-green solution, labeled as solution A; dissolve 0.6mmol sodium ferrocyanide in 30mL deionized water to obtain a yellow-red solution, labeled as solution B. While stirring solution A, slowly pour solution B into it and stir rapidly for 5min to obtain a yellow-green solution; place the FeNi-OH electrode in the solution and let it stand for 12h, take out the electrode and clean it with deionized water, and dry it in a 60℃ oven to obtain a FeNiPBA / FeNi-OH electrode.

[0106] Preparation of FeNi3@NCNTs: The FeNiPBA / FeNi-OH electrode was placed flat on a plate containing 2 The carbon cloth was placed in a porcelain boat containing 0.05 g of dicyandiamide and placed in the center of a tube furnace at 5 °C min -1 At a heating rate of , the temperature was raised to 600 °C in a nitrogen atmosphere for high-temperature carbonization and kept warm for 0.5 h. After the reaction was completed, it was naturally cooled to room temperature and the sample was taken out to obtain a FeNi3@NCNTs electrode.

[0107] Example 3

[0108] Embodiment 3 provides a self-supporting electrode, which includes a carbon cloth substrate and nitrogen-doped carbon nanotubes and FeNi3 particles distributed inside the nanotubes; the nitrogen-doped carbon nanotubes grow on the surface of the carbon cloth conductive substrate.

[0109] The diameter of the nitrogen-doped carbon nanotubes is 30 to 90 nm, and the wall thickness is 3 to 4 nm; the particle size of the FeNi3 particles is 20 to 30 nm.

[0110] Embodiment 3 also provides a method for preparing a self-supporting electrode, comprising the following steps:

[0111] Preparation of FeNi-OH: 1mmol nickel nitrate hexahydrate, 1mmol ferric nitrate nonahydrate, 5mmol urea and 2mmol ammonium fluoride were dissolved in 35mL deionized water to obtain a light green uniform solution; the above solution was poured into a 50mL reactor, the pretreated carbon cloth was tilted into the reactor, and a solvent thermal reaction was carried out at 120°C for 8h. After the reaction was completed and naturally cooled to room temperature, the carbon cloth was taken out, ultrasonically cleaned in deionized water for 1min, and then rinsed with deionized water and anhydrous ethanol, placed flat in a culture dish, and dried in a 60°C oven overnight to obtain a FeNi-OH electrode.

[0112] Preparation of FeNiPBA / FeNi-OH: Dissolve 1mmol of nickel nitrate hexahydrate and 2mmol of sodium citrate in 30mL of deionized water to obtain a blue-green solution, labeled as solution A; dissolve 0.8mmol of potassium ferrocyanide in 30mL of deionized water to obtain a yellow-red solution, labeled as solution B. While stirring solution A, slowly pour solution B into it and stir rapidly for 5min to obtain a yellow-green solution; place the FeNi-OH electrode in the solution and let it stand for 24h, take out the electrode and clean it with deionized water, and dry it in a 60℃ oven to obtain a FeNiPBA / FeNi-OH electrode.

[0113] Preparation of FeNi3@NCNTs: The FeNiPBA / FeNi-OH electrode was placed flat on a plate containing 2 The carbon cloth was placed in a porcelain boat containing 0.50 g urea and placed in the center of a tube furnace at 5 °C min -1 At a heating rate of , the temperature was raised to 750 °C in a nitrogen atmosphere for high-temperature carbonization and kept warm for 1 h. After the reaction was completed, it was naturally cooled to room temperature and the sample was taken out to obtain a FeNi3@NCNTs electrode.

[0114] Example 4

[0115] Embodiment 4 provides a self-supporting electrode, which includes a carbon cloth substrate and nitrogen-doped carbon nanotubes and FeNi3 particles distributed inside the nanotubes; the nitrogen-doped carbon nanotubes grow on the surface of the carbon cloth conductive substrate.

[0116] The diameter of the nitrogen-doped carbon nanotubes is 40 to 90 nm, and the wall thickness is 3 to 4 nm; the particle size of the FeNi3 particles is 20 to 30 nm.

[0117] Embodiment 4 also provides a method for preparing a self-supporting electrode, comprising the following steps:

[0118] Preparation of FeNi-OH: 1mmol nickel nitrate hexahydrate, 1.5mmol ferric nitrate nonahydrate, 8mmol urea and 3mmol ammonium fluoride were dissolved in 35mL deionized water to obtain a light green uniform solution; the above solution was poured into a 50mL reactor, the pretreated carbon cloth was tilted into the reactor, and a solvent thermal reaction was carried out at 150°C for 10h. After the reaction was completed and naturally cooled to room temperature, the carbon cloth was taken out, ultrasonically cleaned in deionized water for 1min, and then rinsed with deionized water and anhydrous ethanol, placed flat in a culture dish, and dried in a 60°C oven overnight to obtain a FeNi-OH electrode.

[0119] Preparation of FeNiPBA / FeNi-OH: Dissolve 1mmol of nickel nitrate hexahydrate and 3mmol of sodium citrate in 30mL of deionized water to obtain a blue-green solution, labeled as solution A; dissolve 1.2mmol of potassium ferrocyanide in 30mL of deionized water to obtain a yellow-red solution, labeled as solution B. While stirring solution A, slowly pour solution B into it and stir rapidly for 5min to obtain a yellow-green solution; place the FeNi-OH electrode in the solution and let it stand for 36h, take out the electrode and clean it with deionized water, and dry it in a 60℃ oven to obtain a FeNiPBA / FeNi-OH electrode.

[0120] Preparation of FeNi3@NCNTs: The FeNiPBA / FeNi-OH electrode was placed flat on a plate containing 2 The carbon cloth was placed in a porcelain boat containing a mixture of 0.30 g of dicyandiamide and urea. The porcelain boat was placed in the center of a tube furnace and heated at 5 °C min -1 At a heating rate of , the temperature was raised to 900 °C in a nitrogen atmosphere for high-temperature carbonization and kept warm for 3 h. After the reaction was completed, it was naturally cooled to room temperature and the sample was taken out to obtain a FeNi3@NCNTs electrode.

[0121] Example 5

[0122] Embodiment 5 provides a self-supporting electrode, which includes a carbon cloth substrate and nitrogen-doped carbon nanotubes and FeNi3 particles distributed inside the nanotubes; the nitrogen-doped carbon nanotubes grow on the surface of the carbon cloth conductive substrate.

[0123] The diameter of the nitrogen-doped carbon nanotubes is 20 to 80 nm, and the wall thickness is 2 to 3 nm; the particle size of the FeNi3 particles is 10 to 20 nm.

[0124] Embodiment 5 also provides a method for preparing a self-supporting electrode, comprising the following steps:

[0125] Preparation of FeNi-OH: 1 mmol nickel nitrate hexahydrate, 0.8 mmol ferric nitrate nonahydrate, 4 mmol urea and 1.5 mmol ammonium fluoride were dissolved in 35 mL deionized water to obtain a light green uniform solution; the above solution was poured into a 50 mL reactor, the pretreated carbon cloth was tilted into the reactor, and a solvent thermal reaction was carried out at 110°C for 7 hours. After the reaction was completed and naturally cooled to room temperature, the carbon cloth was taken out, ultrasonically cleaned in deionized water for 1 minute, and then rinsed with deionized water and anhydrous ethanol, placed flat in a culture dish, and dried in a 60°C oven overnight to obtain a FeNi-OH electrode.

[0126] Preparation of FeNiPBA / FeNi-OH: Dissolve 0.8mmol of nickel nitrate hexahydrate and 1.8mmol of sodium citrate in 30mL of deionized water to obtain a blue-green solution marked as solution A; dissolve 0.7mmol of potassium ferrocyanide in 30mL of deionized water to obtain a yellow-red solution marked as solution B. While stirring solution A, slowly pour solution B into it and stir rapidly for 5min to obtain a yellow-green solution; place the FeNi-OH electrode in the solution and let it stand for 18h, take out the electrode and clean it with deionized water, and dry it in a 60℃ oven to obtain a FeNiPBA / FeNi-OH electrode.

[0127] Preparation of FeNi3@NCNTs: The FeNiPBA / FeNi-OH electrode was placed flat on a plate containing 2 The carbon cloth was placed in a porcelain boat containing 0.10 g of urea mixture, and the porcelain boat was placed in the center of a tube furnace at 5 °C min -1 At a heating rate of , the temperature was raised to 650 °C in a nitrogen atmosphere for high-temperature carbonization and kept warm for 1.5 h. After the reaction was completed, it was naturally cooled to room temperature and the sample was taken out to obtain a FeNi3@NCNTs electrode.

[0128] Example 6

[0129] Embodiment 6 provides a self-supporting electrode, which includes a carbon cloth substrate and nitrogen-doped carbon nanotubes and FeNi3 particles distributed inside the nanotubes; the nitrogen-doped carbon nanotubes grow on the surface of the carbon cloth conductive substrate.

[0130] The diameter of the nitrogen-doped carbon nanotubes is 30 to 80 nm, and the wall thickness is 3 to 4 nm; the particle size of the FeNi3 particles is 10 to 30 nm.

[0131] Embodiment 6 also provides a method for preparing a self-supporting electrode, comprising the following steps:

[0132] Preparation of FeNi-OH: 1mmol nickel nitrate hexahydrate, 1.2mmol ferric nitrate nonahydrate, 6mmol urea and 2.5mmol ammonium fluoride were dissolved in 35mL deionized water to obtain a light green uniform solution; the above solution was poured into a 50mL reactor, the pretreated carbon cloth was tilted into the reactor, and a solvent thermal reaction was carried out at 130°C for 9h. After the reaction was completed and naturally cooled to room temperature, the carbon cloth was taken out, ultrasonically cleaned in deionized water for 1 minute, and then rinsed with deionized water and anhydrous ethanol, placed flat in a culture dish, and dried in a 60°C oven overnight to obtain a FeNi-OH electrode.

[0133] Preparation of FeNiPBA / FeNi-OH: Dissolve 0.9mmol nickel nitrate hexahydrate and 2.2mmol sodium citrate in 30mL deionized water to obtain a blue-green solution marked as solution A; dissolve 0.9mmol potassium ferrocyanide in 30mL deionized water to obtain a yellow-red solution marked as solution B. While stirring solution A, slowly pour solution B into it and stir rapidly for 5min to obtain a yellow-green solution; place the FeNi-OH electrode in the solution and let it stand for 30h, take out the electrode and clean it with deionized water, and dry it in a 60℃ oven to obtain a FeNiPBA / FeNi-OH electrode.

[0134] Preparation of FeNi3@NCNTs: The FeNiPBA / FeNi-OH electrode was placed flat on a plate containing 2 The carbon cloth was placed in a porcelain boat containing 0.45 g of dicyandiamide and placed in the center of a tube furnace at 5 °C min -1 At a heating rate of , the temperature was raised to 850 °C in a nitrogen atmosphere for high-temperature carbonization and kept warm for 2 h. After the reaction was completed, it was naturally cooled to room temperature and the sample was taken out to obtain a FeNi3@NCNTs electrode.

[0135] Comparative Example

[0136] Comparative Example 1

[0137] Comparative Example 1 provides a FeNi3@NCNTs-1 electrode. Compared with the preparation method provided in Example 1, FeNi-OH and dicyandiamide are directly used for high-temperature carbonization and annealing, including the following steps:

[0138] (1) Preparation of FeNi-OH: 1mmol nickel nitrate hexahydrate, 1mmol iron nitrate nonahydrate, 6mmol urea and 2mmol ammonium fluoride were dissolved in 35mL deionized water to obtain a light green uniform solution. The mixed solution was poured into a 50mL reactor, and the pretreated carbon cloth was tilted into the reactor. The solvent thermal reaction was carried out at 120°C for 8h. After the reaction was completed and naturally cooled to room temperature, the carbon cloth was taken out and ultrasonically cleaned in deionized water for 1min, then rinsed with deionized water and anhydrous ethanol, placed flat in a culture dish, and dried in an oven at 60°C overnight to obtain a FeNi-OH electrode.

[0139] (2) Preparation of FeNi3@NCNTs-1: The FeNi-OH electrode obtained above was placed flat in a porcelain boat containing 0.6 g of dicyandiamide. The porcelain boat was placed in the center of a tube furnace and heated at 5 °C min -1 At a heating rate of , the temperature was raised to 750 °C and annealed for 1 h. After the reaction was completed, it was naturally cooled to room temperature and the sample was taken out to obtain a FeNi3@NCNTs-1 electrode.

[0140] Comparative Example 2

[0141] Comparative Example 2 provides a FeNi3@NC electrode. Compared with the preparation method provided in Example 1, the FeNiPBA / FeNi-OH electrode is directly used for high-temperature carbonization and annealing, including the following steps:

[0142] (1) Preparation of FeNi-OH: 1mmol nickel nitrate hexahydrate, 1mmol iron nitrate nonahydrate, 6mmol urea and 2mmol ammonium fluoride were dissolved in 35mL deionized water to obtain a light green uniform solution. The mixed solution was poured into a 50mL reactor, and the pretreated carbon cloth was tilted into the reactor. The solvent thermal reaction was carried out at 120°C for 8h. After the reaction was completed and naturally cooled to room temperature, the carbon cloth was taken out and ultrasonically cleaned in deionized water for 1min, then rinsed with deionized water and anhydrous ethanol, placed flat in a culture dish, and dried in an oven at 60°C overnight to obtain a FeNi-OH electrode.

[0143] (2) Preparation of FeNiPBA / FeNi-OH: 0.7 mmol of nickel nitrate hexahydrate and 1.5 mmol of sodium citrate were dissolved in 30 mL of deionized water to obtain a blue-green solution, which was labeled as solution A; 0.6 mmol of potassium ferrocyanide was dissolved in 30 mL of deionized water to obtain a yellow-red solution, which was labeled as solution B. While solution A was being stirred, solution B was slowly poured into the solution and stirred rapidly for 5 min to obtain a yellow-green solution. The FeNi-OH electrode was then placed in the yellow-green mixed solution. After standing for 24 h, the electrode was taken out and cleaned with deionized water, and dried in an oven at 60°C to obtain a FeNiPBA / FeNi-OH electrode.

[0144] (3) Preparation of FeNi3@NC: The FeNiPBA / FeNi-OH electrode obtained above was placed flat in a porcelain boat, which was placed in the center of a tube furnace and heated at 5°C min -1 At a heating rate of , the temperature was raised to 750 °C and annealed for 1 h. After the reaction was completed, it was naturally cooled to room temperature and the sample was taken out to obtain a FeNi3@NC electrode.

[0145] Comparative Example 3

[0146] Comparative Example 3 provides a Pt / C and RuO2 catalyst carbon cloth electrode with the same loading amount as the FeNi3@NCNTs electrode provided in Example 1, which is used as the ORR and OER benchmarks, respectively, and the preparation method is as follows:

[0147] (1) Preparation of RuO2 catalyst carbon cloth electrode: 3 mg of RuO2 was added to a mixture containing 100 μL Nafion (0.5 wt%) and 900 μL ethanol, and then ultrasonically dispersed for 1 h to obtain a uniform ink. The uniformly dispersed ink was then drop-coated onto the pretreated carbon cloth substrate to obtain a RuO2 electrode.

[0148] (2) Preparation of Pt / C catalyst carbon cloth electrode: 3 mg of Pt / C was added to a mixture containing 100 μL Nafion (0.5 wt%) and 900 μL ethanol, and then ultrasonically dispersed for 1 h to obtain a uniform ink. The uniformly dispersed ink was then drop-coated onto the pretreated carbon cloth substrate to obtain a Pt / C electrode.

[0149] Comparative Example 4

[0150] Comparative Example 4 provides a method for preparing a self-supporting electrode, which is different from Example 1 in that the order of steps is changed, as follows:

[0151] Comparative Example 4 provides a method for preparing a self-supporting electrode, comprising the following steps:

[0152] (1) Preparation of FeNi-OH: 1 mmol nickel nitrate hexahydrate, 1 mmol ferric nitrate nonahydrate, 6 mmol urea and 2 mmol ammonium fluoride were dissolved in 35 mL deionized water to obtain a light green uniform solution; the mixed solution was poured into a 50 mL reactor, and the pretreated carbon cloth was tilted into the reactor to carry out a solvothermal reaction at 120°C for 8 h. After the reaction was completed and the carbon cloth was naturally cooled to room temperature, the carbon cloth was taken out, ultrasonically cleaned in deionized water for 1 min, and then rinsed with deionized water and anhydrous ethanol, placed flat in a culture dish, and dried in an oven at 60°C overnight to obtain a FeNi-OH electrode.

[0153] (2) Preparation of FeNi3@NCNTs-1: The FeNi-OH electrode obtained above was placed flat on a plate containing 2 The carbon cloth was placed in a porcelain boat containing 0.13 g of dicyandiamide and placed in the center of a tube furnace at 5 °C min -1 At a heating rate of , the temperature was raised to 750 °C in a nitrogen atmosphere for high-temperature carbonization and insulation for 1 h. After the reaction was completed, it was naturally cooled to room temperature, and the sample was taken out to obtain a FeNi3@NCNTs-1 electrode.

[0154] (2) Preparation of FeNiPBA / FeNi3@NCNTs-1: 0.7 mmol of nickel nitrate hexahydrate and 1.5 mmol of sodium citrate were dissolved in 30 mL of deionized water to obtain a blue-green solution, which was labeled as solution A; 0.6 mmol of potassium ferrocyanide was dissolved in 30 mL of deionized water to obtain a yellow-red solution, which was labeled as solution B. While solution A was being stirred, solution B was slowly poured into the solution and stirred rapidly for 5 min to obtain a yellow-green solution. The FeNi3@NCNTs-1 electrode was then placed in the yellow-green mixed solution. After standing for 24 h, the electrode was taken out and cleaned with deionized water, and dried in an oven at 60°C to obtain a FeNiPBA / FeNi3@NCNTs-1 electrode.

[0155] Comparative Example 5

[0156] Comparative Example 5 provides a method for preparing a self-supporting electrode, which is different from Example 1 in that, in the preparation of step (1) FeNi-OH, the molar ratio of nickel nitrate hexahydrate, ferric nitrate nonahydrate, urea and ammonium fluoride is 1:2:6:2, and the amount of nickel nitrate hexahydrate is 1 mmol; the other steps are the same as Example 1.

[0157] Comparative Example 6

[0158] Comparative Example 6 provides a method for preparing a self-supporting electrode, which is different from Example 1 in that, in the preparation of step (1) FeNi-OH, the molar ratio of nickel nitrate hexahydrate, ferric nitrate nonahydrate, urea and ammonium fluoride is 1:0.4:6:2, and the amount of nickel nitrate hexahydrate is 1 mmol; the other steps are the same as Example 1.

[0159] Comparative Example 7

[0160] Comparative Example 7 provides a method for preparing a self-supporting electrode, which differs from Example 1 in that, in step (1) the preparation of FeNi-OH, the temperature of the solvent thermal reaction is 165°C; the other steps are the same as Example 1.

[0161] Comparative Example 8

[0162] Comparative Example 8 provides a method for preparing a self-supporting electrode, which differs from Example 1 in that, in step (1) the preparation of FeNi-OH, the temperature of the solvent thermal reaction is 95°C; the other steps are the same as Example 1.

[0163] Comparative Example 9

[0164] Comparative Example 9 provides a method for preparing a self-supporting electrode, which differs from Example 1 in that, in step (1) of preparing FeNi-OH, the solvent thermal reaction time is 12 h; the other steps are the same as Example 1.

[0165] Comparative Example 10

[0166] Comparative Example 10 provides a method for preparing a self-supporting electrode, which is different from Example 1 in that, in the preparation of FeNi-OH in step (1), the solvent thermal reaction time is 5 hours; the other steps are the same as Example 1.

[0167] Comparative Example 11

[0168] Comparative Example 11 provides a method for preparing a self-supporting electrode, which differs from Example 1 in that, in step (2) of preparing FeNiPBA / FeNi-OH, the standing time is 10 h; the other steps are the same as Example 1.

[0169] Comparative Example 12

[0170] Comparative Example 12 provides a method for preparing a self-supporting electrode, which differs from Example 1 in that, in step (2) of preparing FeNiPBA / FeNi-OH, the standing time is 40 h; the other steps are the same as Example 1.

[0171] Comparative Example 13

[0172] Comparative Example 13 provides a method for preparing a self-supporting electrode, which is different from Example 1 in that, in step (2) of preparing FeNiPBA / FeNi-OH, the amount of sodium citrate used is 0.7 mmol; the other steps are the same as Example 1.

[0173] Comparative Example 14

[0174] Comparative Example 14 provides a method for preparing a self-supporting electrode, which differs from Example 1 in that, in step (2) of preparing FeNiPBA / FeNi-OH, solution A is slowly poured into solution B while it is being stirred; the other steps are the same as Example 1.

[0175] Comparative Example 15

[0176] Comparative Example 15 provides a method for preparing a self-supporting electrode. The difference from Example 1 is that in step (3) of preparing FeNi3@NCNTs, the amount of dicyandiamide used is 2 Carbon cloth 0.04g; other steps are the same as Example 1.

[0177] Comparative Example 16

[0178] Comparative Example 16 provides a method for preparing a self-supporting electrode, which differs from Example 1 in that, in step (3), in the preparation of FeNi3@NCNTs, the temperature is raised to 550°C for high-temperature carbonization; the other steps are the same as Example 1.

[0179] Comparative Example 17

[0180] Comparative Example 17 provides a method for preparing a self-supporting electrode, which differs from Example 1 in that, in step (3) of preparing FeNi3@NCNTs, the insulation time is 3.5 h; the other steps are the same as Example 1.

[0181] Application Examples

[0182] Application Example 1

[0183] Liquid zinc-air battery

[0184] The FeNi3@NCNTs provided in Example 1, the FeNi3@NCNTs-1 provided in Comparative Example 1, and the FeNi3@NC electrodes provided in Comparative Example 2 were respectively used to assemble zinc-air liquid batteries. The FeNi3@NCNTs, FeNi3@NCNTs-1, and FeNi3@NC electrodes were used as self-supporting (without binder and conductive additive) air cathodes, and the zinc sheet was used as the anode. -1 Potassium hydroxide (concentration 6 mol·L) with zinc acetate additive -1 ) as the electrolyte to assemble into a liquid zinc-air battery.

[0185] For comparison, the obtained Pt / C+RuO2 electrode was used to assemble a zinc-air liquid battery. The Pt / C+RuO2 electrode was used as a self-supporting (without binder and conductive additive) air cathode, and the zinc sheet was used as the anode. -1 Potassium hydroxide (concentration 6 mol·L) with zinc acetate additive -1 ) as the electrolyte to assemble into a liquid zinc-air battery.

[0186] Application Example 2

[0187] Zinc-air solid-state battery

[0188] The zinc-air solid-state battery was assembled using the FeNi3@NCNTs electrode provided in Example 1. The FeNi3@NCNTs electrode was used as a self-supporting (without a binder and a conductive additive) air cathode, and the zinc sheet was used as an anode. -1 Potassium hydroxide (concentration of 11.25 mol·L) as zinc oxide additive -1 ) electrolyte 5 mL was mixed with 0.5 g acrylic acid and 0.075 g NN methylenebisacrylamide and stirred for 5 min, filtered, and 75 μL 0.3 M potassium persulfate was added as a traction agent to form a gel electrolyte.

[0189] Performance Testing

[0190] (1) OER and ORR performance

[0191] A three-electrode system with silver chloride electrode as indicator electrode, platinum sheet as counter electrode and self-supporting electrode as working electrode was used. 1M KOH and oxygen-saturated 0.1M KOH were used in a CHI660 electrochemical workstation to test the OER and ORR performances of pure carbon cloth CC electrode, FeNi3@NCNTs electrode, FeNi3@NCNTs-1 electrode, FeNi3@NC electrode, the OER performance of RuO2 electrode and the ORR performance of Pt / C electrode.

[0192] The electrocatalytic OER activity test results of the FeNi3@NCNTs electrode provided in Example 1, the FeNi3@NCNTs-1 electrode provided in Comparative Example 1, the FeNi3@NC electrode provided in Comparative Example 2, and the RuO2 electrode provided in Comparative Example 3 in 1.0 M KOH are as follows: Figure 1 shown.

[0193] FeNi3@NCNTs provide a higher current density and lower onset potential compared to other electrodes. OER overpotential = E 实际 -E 理论(1.23V), the overpotential is equal to the difference between the reaction potential determined by thermodynamic theory in the redox reaction and the reaction potential observed in the actual experiment. Generally speaking, due to concentration polarization, electrode surface characteristics and other reasons, the difference cannot be zero. In the study of electrocatalysts, we often hope to reduce this difference to improve the efficiency of electrical energy utilization. Factors affecting the overpotential of the oxygen evolution reaction of zinc-air batteries include the pH value of the electrolyte, the concentration of oxygen, the quality and surface state of the electrode material, etc. These factors will affect the adsorption and reaction rate of oxygen molecules on the electrode surface, thereby affecting the overpotential of the oxygen evolution reaction. The larger the overpotential, the more difficult it is for the oxygen evolution reaction to occur, and the efficiency of the battery will decrease. In order to achieve 10mA·cm -2 The overpotential of FeNi3@NCNTs is only 263 mV, which is significantly lower than that of FeNi3@NCNTs-1 (287 mV) and FeNi3@NC (323 mV), and slightly higher than that of RuO2 (257 mV). The significantly reduced overpotential and increased current density of FeNi3@NCNTs reveal its extraordinary OER catalytic activity.

[0194] The LSV results of the ORR of the FeNi3@NCNTs electrode provided in Example 1, the FeNi3@NCNTs-1 electrode provided in Comparative Example 1, the FeNi3@NC electrode provided in Comparative Example 2, and the Pt / C electrode provided in Comparative Example 3 in an O2-saturated 0.1M KOH solution are as follows: Figure 2 shown.

[0195] Half-wave potential is the most important performance indicator for measuring ORR catalysts. Half-wave potential can be defined as the potential at half of the limiting diffusion current. The more positive the half-wave potential value is, the more active the catalyst is. The faster the rate of oxygen reduction reaction is, the better the battery performance will be. Factors affecting the oxygen reduction reaction of electrode materials include the catalytic activity, surface area and structure of the electrode material. The catalytic activity of the electrode material affects the rate of oxygen reduction reaction, while the surface area and structure will affect the contact area and reaction activity between the electrode and the electrolyte, and will affect the adsorption and reaction rate of oxygen molecules on the electrode surface, thereby affecting the efficiency of the oxygen reduction reaction and thus affecting its half-wave potential. Obviously, FeNi3@NCNTs exhibits the best ORR activity among the electrodes studied. The half-wave potential (E 1 / 2 ) is 0.82 V vs. RHE, which is greater than FeNi3@NCNTs-1 (0.81 V vs. RHE) and FeNi3@NC (0.52 V vs. RHE). Although this performance is not as good as commercial Pt / C (0.84 V vs. RHE), it also shows that FeNi3@NCNTs has good ORR performance.

[0196] (2) X-ray diffraction (XRD) spectrum

[0197] The FeNi3@NCNTs electrode provided in Example 1, the FeNi3@NCNTs-1 electrode provided in Comparative Example 1, and the FeNi3@NC electrode provided in Comparative Example 2 were subjected to X-ray diffraction, and the XRD spectra were as follows: Figure 3 As shown. Figure 3 It can be seen that the diffraction peaks appear at 2θ=25.1°, corresponding to the (002) lattice of graphite carbon of carbon cloth and carbon nanotubes (JCPDs No.41-1487). At the same time, the alloy diffraction peaks of FeNi3 (JCPDs No.38-0419) at (111), (200), and (220) lattices can also be identified. The difference is that FeNi3@NCNTs-1 also has diffraction peaks of metal Ni at (111), (200), and (220) lattices, corresponding to JCPDs No.04-0850, indicating that the addition of FeNiPBA is conducive to the formation of FeNi3 alloy rather than the formation of elemental Ni during the high-temperature reaction. On the other hand, the relative intensity of graphite carbon and FeNi3 alloy peaks of FeNi3@NC is stronger, indicating that when dicyandiamide is not used as an external carbon source, the structure of the carbon-coated alloy is fixed on the surface of the carbon cloth, resulting in the corresponding peak intensity enhancement.

[0198] (3) Scanning electron microscope (SEM)

[0199] The scanning electron microscope (SEM) images of the FeNi3@NCNTs electrode provided in Example 1, the FeNi3@NCNTs-1 electrode provided in Comparative Example 1, and the FeNi3@NC electrode provided in Comparative Example 2 at different magnifications are as follows: Figure 4 As shown. Figure 4 (ab) It can be seen that the carbon nanotubes of the FeNi3@NCNTs electrode grow uniformly on the carbon cloth conductive substrate and grow upright outward, which is different from FeNi3@NCNTs-1( Figure 4 (cd)) In comparison, the carbon nanotubes grown by FeNi3@NCNTs are more slender, while the diameter of FeNi3@NCNTs-1 is larger and there is agglomeration at the top of the carbon nanotubes. Figure 4 As can be seen from (ef), FeNi3@NC presents a carbon-coated alloy structure fixed on the surface of carbon cloth, indicating that FeNiPBA cannot catalyze the formation of carbon nanotubes when dicyandiamide is not used as an external carbon source.

[0200] (4) Transmission electron microscope TEM

[0201] The transmission electron microscopy (TEM) images of the FeNi3@NCNTs electrode provided in Example 1 and the FeNi3@NCNTs-1 electrode provided in Comparative Example 1 are as follows: Figure 5 As shown. Figure 5 It can be seen that the NCNTs of FeNi3@NCNTs have a typical bamboo-like structure, with a tube diameter of about 20 to 80 nm; FeNi3 alloy particles with a particle size of 10 to 20 nm are densely and evenly distributed in carbon nanotubes with a wall thickness of 2 to 3 nm. It can be seen from the TEM image of FeNi3@NCNTs-1 that in addition to FeNi3 alloy particles with a size of 10 to 20 nm, there are also relatively large Ni particles with a size of 100-300 nm distributed in the coarser carbon nanotubes, indicating that the addition of FeNiPBA is conducive to the formation of FeNi3 alloy rather than the formation of single Ni during the high-temperature reaction.

[0202] (5) Cyclic Sweep Voltammetry Test

[0203] The FeNi3@NCNTs electrode provided in Example 1, the FeNi3@NCNTs-1 electrode provided in Comparative Example 1, and the FeNi3@NC electrode provided in Comparative Example 2 were tested by cyclic scanning voltammetry using different scanning rates to obtain electrochemical double layer capacitance (Cdl) versus electrochemically active surface area (ESCA) of different catalysts. Figure 6 shown.

[0204] The significance of comparing the electrochemical double layer capacitance (Cdl) to the electrochemically active surface area (ESCA) of different catalysts is to evaluate the activity and efficiency of the catalyst in the electrochemical reaction. This comparison can help researchers understand the extent to which the surfaces of different catalysts can participate in the reaction, thereby revealing the electrocatalytic activity of the catalyst and the electrocatalytic reaction mechanism. A large electrochemically active surface area (ESCA) can provide more active sites for electrochemical reactions, thereby increasing the reaction rate and efficiency. There are many factors that affect the electrochemical active surface area, including the chemical composition, surface morphology, pore structure, and electron transport properties of the catalyst. These factors can directly affect the electrochemical reaction performance of the catalyst, and thus affect the results of the electrochemically active surface area (ESCA). Figure 6 It can be seen that compared with FeNi3@NCNTs-1 (57.69mF·cm -2 )、FeNi3@NC(2.97mF·cm -2 ) and RuO2 (45.27mF·cm -2 ), FeNi3@NCNTs has the highest value of 106.14 mF·cm -2 This is related to the slender NCNTs grown by FeNi3@NCNTs, which provide a large specific surface area. In addition, the FeNi alloy is distributed inside the carbon tubes in small particles and high density, and the active sites are effectively exposed, thus having better catalytic performance.

[0205] (6) Liquid zinc-air battery charge and discharge cycle performance test

[0206] The liquid zinc-air battery provided in Application Example 1 was subjected to constant current (current density of 10 mA cm -2 ) Charge and discharge cycle performance test results are as follows Figure 7 As shown. At a current density of 10 mA cm -2 The cyclic stability of ZAB with FeNi3@NCNTs air cathode was evaluated in the continuous discharge / charge cycle. The initial charge and discharge potentials were 1.94V and 1.20V, respectively, and the gap was 0.74V, which was much smaller than FeNi3@NCNTs-1 (1.10V), FeNi3@NC (0.92V), and Pt / C+RuO2 (1.00V). Generally speaking, the smaller the battery voltage difference, the better. A small voltage difference means less energy loss during the charge and discharge process of the battery, high efficiency, and more efficient use of energy. The larger the voltage difference, the more battery capacity loss. Factors affecting the voltage difference of zinc-air batteries include the degree of zinc activation, the oxygen concentration in the air, and the temperature. The degree of zinc activation affects the reaction rate between zinc and oxygen, and the oxygen concentration and temperature in the air affect the rate of the redox reaction occurring at the electrode, thereby affecting the voltage difference. It is worth noting that the duration of the charge and discharge test exceeded 900h (>2000 cycles), which is much longer than the liquid zinc-air battery assembled with FeNi3@NCNTs-1 (≈250h) and FeNi3@NC (≈240h) cathodes. The FeNi3@NCNTs air cathode exhibited excellent long-term durability and stability, and the voltage difference (ΔE) remained at 0.89V. This shows that FeNi3@NCNTs can be used as the air cathode of zinc-air batteries to achieve excellent battery performance.

[0207] (7) Voltage-specific capacity test of liquid zinc-air battery discharge

[0208] The liquid zinc-air battery provided in Application Example 1 was subjected to constant current (current density of 10 mA cm -2 ) The voltage-specific capacity curve of the discharge test is as follows Figure 8 shown.

[0209] The specific capacity of a zinc-air battery is the ratio of the battery's energy density to its volume, which reflects the amount of energy that can be stored in a certain volume. The larger the specific capacity, the more energy a battery can store per unit volume. Factors that affect the specific capacity of a zinc-air battery include the activation efficiency of the zinc negative electrode, the structure and material of the air electrode, and the performance of the electrolyte. The activation efficiency of the zinc negative electrode will affect the battery's capacity, while the structure and material of the air electrode and the performance of the electrolyte will affect the battery's energy density and cycle life. The zinc-air battery assembled with this electrode can achieve 788.76mAh·g Zn–1 The specific capacity is significantly higher than that of FeNi3@NCNTs-1 (764.80 mAh g Zn -1 ), FeNi3@NC(742.80mAh·g Zn -1 ), Pt / C+RuO2(755.50mAh·g Zn -1 ) electrode assembled zinc-air battery, and close to its theoretical specific capacity of 820mAh g Zn -1 , showing its excellent specific capacity.

[0210] (8) Solid-state zinc-air battery lighting LED light board test

[0211] Application Example 2 provides a solid-state zinc-air battery to light up the LED light board for actual operation. Fig. 9 As shown, the solid-state zinc-air battery (FZAB) assembled with FeNi3@NCNTs as air electrodes lights up the blue LED light board under different bending conditions (a) flat; (b) a single piece bent 90°; (c) two pieces bent 90°. By connecting two FZABs in series ( Fig. 9 (a)) successfully lights up a light board assembled from 41 commercial blue LED beads, proving its potential as a portable power source. In addition, the light board can still be lit up when bent, and the brightness of the light board does not decrease, indicating that the assembled FZAB has excellent mechanical properties.

[0212] According to the above performance test method, the self-supporting electrodes provided in Examples 1-6 and Comparative Examples 1-17 were tested and characterized for OER, ORR, tube diameter and wall thickness of nanotubes, particle size of metal particles, electrochemically active surface area, and voltage-specific capacity of liquid zinc-air battery discharge. The results are shown in Table 1 below.

[0213] Table 1 Performance test results of self-supporting electrodes provided by Examples 1-6 and Comparative Examples 1-17

[0214]

[0215]

[0216] As can be seen from Table 1, the data in Table 1 show significant differences in electrochemical performances of the self-supporting electrodes provided by Examples 1-6 and Comparative Examples 1-17 in terms of oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). By comparing the performance of these electrodes in key indicators such as overpotential, half-wave potential, electrochemically active surface area and specific capacity, it can be clearly seen that the electrode in Example 1 has superior comprehensive performance, especially in terms of oxygen evolution and oxygen reduction reaction catalytic activity.

[0217] First, the data in Table 1 show that the overpotential of the FeNi3@NCNTs self-supporting electrode of Example 1 in OER is only 263mV, which is much lower than the overpotential of the comparative electrode. The electrode overpotential of Comparative Example 16 is as high as 325mV, which shows that Example 1 has a significant advantage in reducing the energy consumption of the oxygen evolution reaction. This low overpotential means that the electrode can complete the oxygen evolution reaction with lower energy consumption in practical applications, thereby improving the overall energy efficiency of the battery. At the same time, the half-wave potential of Example 1 in ORR is 0.82V, which is close to the level of commercial Pt / C catalysts compared to the comparative electrode, indicating that its catalytic activity in oxygen reduction reaction is also very good.

[0218] Secondly, Table 1 shows the influence of structural parameters of different electrodes on their performance. The diameter of nitrogen-doped carbon nanotubes (NCNTs) in Example 1 is 20-90nm, the wall thickness is 2-4nm, and the particle size of FeNi3 particles is 10-30nm. This moderate nanostructure not only increases the specific surface area of ​​the electrode, but also ensures the uniform distribution of particles inside the carbon nanotubes, avoiding the agglomeration of particles. This feature enables the electrode to maintain stable performance in long-term electrochemical cycles, avoiding the reduction of catalytic activity caused by particle aggregation.

[0219] Electrochemically active surface area (ESCA) is an important indicator for measuring electrode catalytic activity. Table 1 shows that the electrochemically active surface area of ​​Example 1 reached 106.14 mF·cm -2 , far exceeding the 2.97mF·cm of comparative example 2 -2 A larger active surface area means that the electrode can provide more active sites, thereby improving the electrochemical reaction rate and efficiency. This significant active surface area improves the efficiency of the electrode of Example 1 in practical applications, especially in applications under high current conditions.

[0220] Finally, Table 1 also shows the difference in specific capacity. The specific capacity of Example 1 is 788.76 mAh gZn -1 , close to the theoretical value of zinc-air battery 820mAh gZn -1This data shows that the electrode of Example 1 has great potential in energy storage. Compared with the comparative electrode, which generally has a low specific capacity, the specific capacity of the electrode of Example 1 is outstanding, further confirming its superior performance in battery applications.

[0221] In general, the self-supporting electrode of Example 1 is superior to the comparative electrode in key performance indicators such as overpotential, half-wave potential, electrochemical active surface area and specific capacity, reflecting its excellent performance in electrocatalytic reactions. This performance superiority is due to the fine control of the electrode structure, such as the uniform growth of nitrogen-doped carbon nanotubes and the reasonable distribution of FeNi3 particles, which ensures its bifunctional catalytic activity in oxygen evolution and oxygen reduction reactions.

[0222] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A self-supporting electrode, characterized in that: The self-supporting electrode comprises a conductive substrate and nitrogen-doped carbon nanotubes and FeNi3 particles distributed inside the nanotubes; the nitrogen-doped carbon nanotubes grow on the surface of the conductive substrate.

2. A self-supporting electrode according to claim 1, characterized in that: The conductive substrate is any one of carbon paper, carbon cloth, foamed nickel and foamed copper.

3. A self-supporting electrode according to claim 1, characterized in that: The diameter of the nitrogen-doped carbon nanotubes is 20 nm to 90 nm, and the wall thickness is 2 nm to 4 nm.

4. A self-supporting electrode according to claim 1, characterized in that: The particle size of the FeNi3 particles is 10nm to 30nm.

5. A method for preparing a self-supporting electrode, characterized in that: Includes steps: Dissolving iron salt, nickel salt, ammonium fluoride and urea in water to form an iron-nickel precursor solution; subjecting a conductive substrate to a solvothermal reaction in the iron-nickel precursor solution to obtain a FeNi-OH electrode; Mixing a nickel salt solution with a ferrocyanate solution to form a Prussian blue analog precursor solution; subjecting the FeNi-OH electrode to chemical deposition self-assembly in the Prussian blue analog precursor solution to obtain a FeNiPBA / FeNi-OH electrode; The FeNiPBA / FeNi-OH electrode is carbonized at high temperature in an inert atmosphere using a nitrogen source as an evaporation source to obtain the self-supporting electrode.

6. The method for preparing a self-supporting electrode according to claim 5, characterized in that: In the iron-nickel precursor solution, the molar ratio of nickel salt, iron salt, urea and ammonium fluoride is 1:0.5-1.5:3-8:1-3.

7. The method for preparing a self-supporting electrode according to claim 5, characterized in that: In the Prussian blue precursor solution, the mixing volume ratio of the nickel salt solution to the ferricyanide solution is 1:0.8-1.2; The nickel salt solution also includes citrate, and the molar ratio of the nickel salt to the citrate is 1:1.5-3.

0.

8. The method for preparing a self-supporting electrode according to claim 5, characterized in that: The iron salt and nickel salt include one or more of nitrate, sulfate and acetate; The citrate includes one of potassium citrate and sodium citrate; The ferrocyanide includes one of potassium ferrocyanate and sodium ferrocyanate; The nitrogen source includes one or more of dicyandiamide, urea, melamine, and cyano derivatives.

9. The method for preparing a self-supporting electrode according to claim 5, characterized in that: The temperature of the solvent thermal reaction is 100°C to 150°C, and the reaction time is 6h to 10h; The chemical deposition self-assembly time is 12h to 36h; The high temperature carbonization is carried out at 600° C. to 900° C. for 0.5 h to 3 h.

10. An application of a self-supporting electrode, characterized in that: The self-supporting electrode is applied to electrode materials of liquid zinc-air batteries, all-solid-state zinc-air batteries, and flexible wearable batteries.

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