Preparation and Application of a Self-Supported Carbon-Coated Cobalt-Iron-Nickel Binary Dual-Phase Alloy Multifunctional Catalyst

Abstract

This invention belongs to the field of air electrode materials for zinc-air batteries, and discloses the preparation and application of a self-supporting carbon-coated cobalt-iron / nickel-iron binary dual-phase alloy multifunctional catalyst. The CoFe-NiFe / NC catalyst synthesized by carbonization reduction under relatively low temperature conditions is composed of cross-linked N-doped carbon nanosheets. The nanosheets are uniformly decorated with dense, uniform micro-nanoparticles, which have more exposed active sites, directional electron transfer, and accelerated mass diffusion between the carbon nanosheets, thereby promoting reversible oxygen reactions. The carbon-coated cobalt-iron / nickel-iron binary dual-phase alloy oxygen electrode prepared by this invention exhibits good OER / ORR / HER electrochemical activity. When assembled into a liquid zinc-air battery, it demonstrates excellent cycle performance and capacity. Furthermore, it exhibits high mechanical flexibility, showing promising application prospects in flexible wearable devices and water splitting.

Description

Technical Field

[0001] This invention belongs to the field of air electrode materials for zinc-air batteries, and specifically relates to the preparation and application of a self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst. Background Technology

[0002] The emergence of new portable and wearable electronics, such as flexible displays, smart clothing, and implantable medical devices, promises to bring about tremendous changes to people's daily lives. Developing flexible energy storage and conversion technologies, such as water splitting, zinc-air batteries, and fuel cells, is a crucial strategy for adapting to these new devices and addressing the current energy crisis. Zinc-air batteries are considered a potential power source candidate due to their high energy density and low cost. On the other hand, electrochemically driven water splitting can produce hydrogen based on the electron energy generated from clean energy sources, a clean, efficient, and zero-carbon emission energy source. In principle, a key issue in realizing these energy technologies is the fabrication of flexible electrodes with highly active electrocatalytic activity that can facilitate three key reactions: the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and the oxygen reduction reaction (ORR), which determine energy conversion and storage efficiency. However, the high overpotential in practical operation leads to slow kinetics in HER / OER / ORR, significantly limiting operational efficiency. Pt / C is considered state-of-the-art in ORR and HER, while RuO2 and IrO2 are benchmark catalysts for OER. However, their high cost, poor stability, and scarcity hinder their widespread application. More importantly, these noble metal-based catalysts can only promote specific reactions. Ru and Ir-based electrocatalysts are only effective for OER, while Pt-based electrocatalysts with high HER and ORR activities generally exhibit poor OER performance. Therefore, there is an urgent need to develop efficient, low-cost, and stable trifunctional electrocatalysts and assemble them into electrodes with excellent mechanical strength.

[0003] Transition metal and nitrogen-doped carbon materials (MNC, M=Ni, Co, Fe, etc.) have been widely reported due to their excellent ORR and OER bifunctional oxygen electrode activities. However, the simple synthesis of highly active bifunctional MNC catalysts remains a challenge because the aggregation and phase separation of metal particles are difficult to handle during high-temperature synthesis. Therefore, constructing materials with uniform, high-density, and well-preserved metal active sites is an effective way to achieve high-performance bifunctional catalysts. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a method for preparing a self-supporting carbon-coated cobalt-iron-nickel binary dual-phase alloy multifunctional catalyst.

[0005] Another objective of this invention is to provide a self-supporting carbon-coated cobalt-iron / nickel-iron binary dual-phase alloy multifunctional catalyst prepared by the above method. The CoFe-NiFe / NC catalyst, synthesized by carbonization reduction under relatively low temperature conditions, consists of cross-linked N-doped carbon nanosheets. The nanosheets are uniformly decorated with dense and uniform micro-nanoparticles, which have more exposed active sites, directional electron transfer, and accelerated mass diffusion between the carbon nanosheets, thereby promoting reversible oxygen reactions.

[0006] Another objective of this invention is to provide the application of the above-mentioned self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst in zinc-air batteries, flexible wearable devices, and water splitting.

[0007] The objective of this invention is achieved through the following solution:

[0008] A method for preparing a self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst includes the following steps:

[0009] (1) Disperse cobalt salt, iron salt, urea and ammonium fluoride into water and stir to form a uniform solution;

[0010] (2) The solution obtained in step (1) and the nickel foam conductive substrate (2*5cm) 2 The electrodes were transferred together to a high-pressure reactor for reaction. After the reaction was completed, the electrodes were removed, rinsed, and dried.

[0011] (3) Dissolve cobalt salt and polyvinylpyrrolidone in a solvent to obtain solution A; dissolve organic ligand in a solvent to obtain solution B; soak the electrode dried in step (2) in solution A, then add solution B to solution A to react, and finally wash and dry the obtained electrode for later use.

[0012] (4) The electrode obtained in step (3) is calcined in an inert atmosphere to obtain a self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst.

[0013] The cobalt salt mentioned in step (1) is at least one of cobalt nitrate hexahydrate, cobalt acetate tetrahydrate, and cobalt sulfate heptahydrate, preferably cobalt nitrate hexahydrate;

[0014] The iron salt mentioned in step (1) is at least one of ferric nitrate nonahydrate, ferric sulfate heptahydrate, and ferric acetate, preferably ferric nitrate nonahydrate;

[0015] The molar ratio of cobalt salt, iron salt, urea and ammonium fluoride in step (1) is (1-5):1:(1-15):8, preferably 2:1:15:8.

[0016] The concentration of cobalt salt in the homogeneous solution formed in step (1) is 0.01 mol / L to 0.04 mol / L;

[0017] Before use, the nickel foam described in step (2) is preferably pretreated with acetone and dilute hydrochloric acid to remove surface oxides. The specific pretreatment steps are as follows: first, sonicate in acetone for 5-10 minutes, clean the surface of residual acetone with deionized water, then soak in 0.01mol / L-1mol / L dilute hydrochloric acid for 5-10 minutes, clean the surface of residual dilute hydrochloric acid with deionized water, then sonicate in water for 10-20 minutes, and finally sonicate in anhydrous ethanol for 5-10 minutes and dry for later use.

[0018] The amounts of solution and nickel foam conductive substrate mentioned in step (2) are such that the nickel foam conductive substrate is completely immersed in the solution, and the solution cannot exceed 2 / 3 of the volume of the reactor.

[0019] The reaction described in step (2) refers to a reaction at 100-180℃ for 4-12 hours, preferably at 120℃ for 6 hours.

[0020] The rinsing described in step (2) is preferably done with water and ethanol.

[0021] The cobalt salt mentioned in step (3) is at least one of cobalt nitrate hexahydrate, cobalt acetate tetrahydrate, and cobalt sulfate heptahydrate, preferably cobalt nitrate hexahydrate;

[0022] The organic ligand mentioned in step (3) is at least one of dimethylimidazole, N,N-dimethylformamide, and benzotricarboxylic acid, preferably dimethylimidazole.

[0023] The ratio of cobalt salt to polyvinylpyrrolidone in solution A in step (3) is 1 mmol:0.1 g to 8 mmol:2 g, preferably 4 mmol:0.8 g; the amount of solvent in solution A in step (3) satisfies that the concentration of cobalt salt in solution A is 20-60 mmol / L, preferably 40 mmol / L.

[0024] In step (3), the solvent in solution A and solution B is the same, which is one of methanol, ethanol, and isopropanol, preferably methanol.

[0025] The concentration of the organic ligand in solution B in step (3) is 100-600 mmol / L, preferably 400 mmol / L;

[0026] The molar ratio of cobalt salt and organic ligand in step (3) is 1:20-1:1, preferably 1:10.

[0027] The molar ratio of the organic ligand in step (3) to the iron salt in step (1) is 10:1-60:1, preferably 57:1.

[0028] The soaking in solution A mentioned in step (3) refers to soaking at room temperature for 10 min-60 min, preferably 30 min; the reaction mentioned in step (3) refers to reacting at 20-30℃ for 12-24 h.

[0029] The washing mentioned in step (3) refers to washing with the solvent in step (3).

[0030] The inert atmosphere described in step (4) is preferably an Ar atmosphere.

[0031] The calcination mentioned in step (4) refers to heating to 450-700℃ at a heating rate of 1-5℃ / min and reacting for 1-5 hours.

[0032] A self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst prepared by the above method.

[0033] The above-mentioned self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst has applications in zinc-air batteries, flexible wearable devices, and water splitting.

[0034] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0035] (1) In view of the defects of the oxygen electrode of the air cathode in the traditional zinc-air battery, the present invention does not require the addition of any binder, additives and conductive agents, and grows directly on the conductive substrate as a self-supporting electrode, avoiding the cumbersome process of the air cathode of the traditional zinc-air battery, which is conducive to reducing costs and large-scale application.

[0036] (2) This invention generates CoFe hydroxide on nickel foam via a hydrothermal reaction, adsorbs Co-ZIF, and then undergoes high-temperature calcination and carbonization reduction to obtain dense and uniform micro-CoFe and NiFe nanoalloy particles uniformly decorated on cross-linked N-doped carbon nanosheets. These particles have more exposed active sites, directional electron transfer, and accelerated mass diffusion between carbon nanosheets, thereby promoting reversible oxygen reactions. Furthermore, the lower carbonization temperature for synthesizing the biphase alloy helps reduce the composition and effectively overcomes the drawbacks of existing preparation methods, such as harsh multi-step synthesis conditions, complex processes, and high costs, enabling industrialization.

[0037] (3) The carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy oxygen electrode prepared by the present invention has good OER / ORR / HER electrochemical activity. When assembled into a liquid zinc-air battery, it has excellent cycle performance and capacity. In addition, it has high mechanical flexibility and can be used to prepare flexible zinc-air batteries. It has good flexibility and portability and has good application and development prospects in the field of flexible wearable devices and the field of water electrolysis.

[0038] (4) This invention is simple and easy to implement, uses inexpensive raw materials, has a simple preparation process, does not require harsh conditions, has low equipment dependence, and a simple process, making it suitable for large-scale industrial production applications. Attached Figure Description

[0039] Figure 1 SEM image of a self-supporting carbon-coated cobalt-iron / nickel-iron binary dual-phase alloy multifunctional oxygen electrode prepared for Case 1;

[0040] Figure 2 XPS plots for Example 1, Comparative Example 1, and Comparative Example 2, where (a) represents the full spectrum of Example 1, Comparative Example 1, and Comparative Example 2, (b) represents the Co 2p fitted spectrum of Example 1, Comparative Example 1, and Comparative Example 2, (c) represents the Fe 2p fitted spectrum of Example 1 and Comparative Example 2, (d) represents the Ni 2p fitted spectrum of Example 1, (e) represents the N1s fitted spectrum of Example 1 and Comparative Example 1, and (f) represents the O1s fitted spectrum of Example 1, Comparative Example 1, and Comparative Example 2.

[0041] Figure 3 The images are SEM images of the composite electrodes of Examples 1-6, where (a) and (b) represent Example 2, (c) and (d) represent Example 1, (e) and (f) represent Example 3, (g) and (h) represent Example 4, (i) and (j) represent Example 5, and (k) and (l) represent Example 6.

[0042] Figure 4 The XRD patterns of the composite electrodes of Example 1, Comparative Example 1, and Comparative Example 2 are shown.

[0043] Figure 5 TEM image of a self-supporting carbon-coated cobalt-iron / nickel-iron binary dual-phase alloy multifunctional oxygen electrode prepared for Case 1.

[0044] Figure 6 The OER / ORR / HER performance data graphs of the composite electrodes of Example 1 and Comparative Examples 1-2 are shown below; where (a) represents the OER performance data graph of Example 1, Comparative Example 1, and Comparative Example 2, (b) represents the ORR performance data graph of Example 1, Comparative Example 1, and Comparative Example 2, and (c) represents the HER performance data graph of Example 1, Comparative Example 1, and Comparative Example 2.

[0045] Figure 7 The diagrams show the OER / ORR / HER performance of the composite electrodes of Examples 1-6; where (a) represents the HER performance data of Examples 1-6, (b) represents the OER performance data of Examples 1-6, and (c) represents the ORR performance data of Examples 1-6.

[0046] Figure 8The graph shows the cycle performance of a liquid zinc-air battery assembled using the self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional oxygen electrode prepared in Example 1, and the liquid zinc-air battery assembled in Comparative Example 1, under constant current charge-discharge test.

[0047] Figure 9 The voltage-specific capacity curves of the liquid zinc-air battery assembled with the self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional oxygen electrode prepared in Example 1 and the liquid zinc-air battery assembled in Comparative Example 1 were obtained by constant current discharge testing.

[0048] Figure 10 This diagram illustrates the practical application of the air cathode in a flexible solid-state zinc-air battery assembled from the self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional oxygen electrode prepared in Example 2.

[0049] Figure 11 The graph shows the stability test results of a flexible solid-state zinc-air battery assembled from the self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional oxygen electrode prepared in Example 1, used as a power source, and the flexible solid-state zinc-air battery assembled in Comparative Example 1 used as a power source to power a water electrolysis device. Detailed Implementation

[0050] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0051] Unless otherwise specified, all reagents used in the examples are commercially available.

[0052] In the embodiments, the pre-dried nickel foam conductive substrate was pretreated by the following method: first, sonicated in acetone for 5-10 min, then cleaned with deionized water to remove residual acetone, then immersed in 0.01 mol / L-1 mol / L dilute hydrochloric acid for 5-10 min, then cleaned with deionized water to remove residual dilute hydrochloric acid, then sonicated in deionized water for 10-20 min, and finally sonicated in anhydrous ethanol for 5-10 min, and then dried for later use.

[0053] Example 1

[0054] 1) Disperse 2 mmol cobalt nitrate hexahydrate, 1 mmol ferric nitrate nonahydrate, 15 mmol urea and 8 mmol ammonium fluoride into 50 ml of deionized water and form a uniform pink transparent solution under magnetic stirring.

[0055] 2) Add 35 mL of the above transparent solution and a pre-dried nickel foam conductive substrate (2*5 cm) 2 The reaction mixture was transferred to a 50ml polytetrafluoroethylene-lined stainless steel autoclave. The autoclave was then transferred to an electrically heated constant temperature drying oven and dried at 120℃ for 6 hours. After the reaction was completed, the mixture was allowed to cool naturally to room temperature. The electrodes were then removed, rinsed repeatedly with deionized water and ethanol, and finally dried in a vacuum drying oven.

[0056] 3) Dissolve 4 mmol of cobalt nitrate hexahydrate and 0.8 g of polyvinylpyrrolidone in 100 ml of methanol to obtain solution A; dissolve 40 mmol of dimethylimidazole in 100 ml of methanol to obtain solution B. Soak the electrode dried in step (2) in solution A for 30 min, then add solution B to solution A and react for 20 h. Finally, wash the obtained electrode with methanol and dry it for later use.

[0057] 4) The electrode obtained in step (3) is heated to 500℃ and annealed for 2h in an Ar atmosphere at a heating rate of 2℃ / min to obtain the final electrode, named NF / CoFe-NiFe / NC.

[0058] Example 2:

[0059] This embodiment provides a method for preparing a self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst. The difference between this preparation method and that of Example 1 is:

[0060] 4) The electrode obtained in step (3) is heated to 450℃ and annealed for 2h in an Ar atmosphere at a heating rate of 2℃ / min to obtain the final electrode, named CoFe-NiFe / NC-450℃.

[0061] Example 3:

[0062] This embodiment provides a method for preparing a self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst. The difference between this preparation method and that of Example 1 is:

[0063] 4) The electrode obtained in step (3) is heated to 550℃ for 2h under Ar atmosphere at a heating rate of 2℃ / min to obtain the final electrode, named CoFe-NiFe / NC-550℃.

[0064] Example 4:

[0065] This embodiment provides a method for preparing a self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst. The difference between this preparation method and that of Example 1 is:

[0066] 4) The electrode obtained in step (3) is heated to 600℃ and annealed for 2h in an Ar atmosphere at a heating rate of 2℃ / min to obtain the final electrode, named CoFe-NiFe / NC-600℃.

[0067] Example 5:

[0068] This embodiment provides a method for preparing a self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst. The difference between this preparation method and that of Example 1 is:

[0069] 4) The electrode obtained in step (3) is heated to 650℃ for 2h under Ar atmosphere at a heating rate of 2℃ / min to obtain the final electrode, named CoFe-NiFe / NC-650℃.

[0070] Example 6:

[0071] This embodiment provides a method for preparing a self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst. The difference between this preparation method and that of Example 1 is:

[0072] 4) The electrode obtained in step (3) is heated to 700℃ and annealed for 2h in an Ar atmosphere at a heating rate of 2℃ / min to obtain the final electrode, named CoFe-NiFe / NC-700℃.

[0073] Comparative Example 1:

[0074] 1) Disperse 2 mmol cobalt nitrate hexahydrate, 15 mmol urea and 8 mmol ammonium fluoride into 50 ml of deionized water and form a uniform pink transparent solution under magnetic stirring.

[0075] 2) Transfer the above transparent solution and the pre-dried nickel foam conductive substrate to a 50ml polytetrafluoroethylene-lined stainless steel autoclave. Transfer the autoclave to an electric thermostatic drying oven and carry out the reaction at 120℃ for 6 hours. After the reaction is completed, allow it to cool naturally to room temperature. Remove the electrode, rinse it repeatedly with deionized water and ethanol, and finally dry it in a vacuum drying oven.

[0076] 3) Dissolve 4 mmol of cobalt nitrate hexahydrate and 0.8 g of polyvinylpyrrolidone in 100 ml of methanol to obtain solution A. Dissolve 40 mmol of dimethylimidazole in 100 ml of methanol to obtain solution B. Soak the electrode dried in step (2) in solution A for 30 min, then add solution B to solution A and react for 20 h. Finally, wash the obtained electrode with methanol and dry it for later use.

[0077] 4) The electrode obtained in step (3) is subjected to an Ar atmosphere at 2℃ min. -1The electrode was heated to 500℃ and annealed for 2 hours to obtain the final electrode, which was named Co / NC.

[0078] Comparative Example 2:

[0079] 1) Disperse 2 mmol cobalt nitrate hexahydrate, 1 mmol ferric nitrate nonahydrate, 15 mmol urea and 8 mmol ammonium fluoride into 50 ml of deionized water and form a uniform pink transparent solution under magnetic stirring.

[0080] 2) Transfer the above transparent solution and the pre-dried nickel foam conductive substrate to a 50ml polytetrafluoroethylene-lined stainless steel autoclave. Transfer the autoclave to an electric thermostatic drying oven and carry out the reaction at 120℃ for 6 hours. After the reaction is completed, allow it to cool naturally to room temperature. Remove the electrode, rinse it repeatedly with deionized water and ethanol, and finally dry it in a vacuum drying oven.

[0081] 3) Expose the electrode obtained in step (2) to air at 2°C for 2 minutes. -1 The electrode was heated to 500℃ and annealed for 2 hours to obtain the final electrode, which was named Fe-Co3O4.

[0082] Application Example 1:

[0083] The trifunctional oxygen electrode of Specific Example 1 was used as the air cathode, a polished zinc plate (300 μm thick) was used as the anode, and a mixed aqueous electrolyte of 6 M KOH and 0.2 M zinc acetate was used as the electrolyte to form a liquid zinc-air battery. All electrochemical performance tests were performed under atmospheric conditions using a CHI650E and a NEWARE battery system (CT-3008).

[0084] Application Example 2:

[0085] A flexible zinc-air battery was assembled using the trifunctional oxygen electrode from Specific Example 1 as the air cathode, polished zinc foil as the anode, and a polymer gel electrolyte sandwiched between them (preparation method: 0.25M ZnO and 11.25M KOH were added to 5mL of deionized water, and a mixed dispersion was prepared by magnetic stirring. Next, 0.5g of acrylic acid and 0.075g of N,N'-methylenebisacrylamide were dissolved in the above naturally cooled dispersion, and the mixture was stirred continuously for 5min. The precipitate was further filtered out to form a transparent dispersion. Finally, the transparent dispersion was poured into a petri dish, and 75μL of 0.3M K2S2O4 was added to initiate monomer polymerization to form a gel electrolyte). All electrochemical performance tests were performed under atmospheric conditions using a CHI650E and a NEWARE battery system (CT-3008).

[0086] Application Example 3:

[0087] The trifunctional oxygen electrode of Specific Embodiment 1 is used as the positive and negative electrodes to assemble a water electrolysis device. The water electrolysis device is directly driven by two flexible batteries of Application Implementation Case 1 connected in series, and is used for hydrogen production.

[0088] Comparative Application Example 1:

[0089] A liquid zinc-air battery was constructed by supporting a RuO2+Pt / C catalyst on nickel foam as an air cathode, using a polished zinc plate (300 μm thick) as the anode, and a mixed aqueous electrolyte of 6 M KOH and 0.2 M zinc acetate as the electrolyte. All electrochemical performance tests were performed under atmospheric conditions using a CHI650E and a NEWARE battery system (CT-3008).

[0090] The RuO2+Pt / C catalyst was prepared as follows: 1 mg of commercial Pt / C and 1 mg of RuO2 were ultrasonically dispersed in 1 mL of ethanol containing 100 μL of Nafion solution (0.5 wt.%) for 1 h to obtain a homogeneous dispersion. The homogeneous dispersion was then dropwise added to a pre-dried NF substrate with a catalyst loading of 2.0 mg / cm³. -2 .

[0091] Comparative Application Example 2:

[0092] A flexible zinc-air battery was assembled by loading a RuO2+Pt / C catalyst onto nickel foam as an air cathode, polished zinc foil as an anode, and a polymer gel electrolyte sandwiched between the air cathode (preparation method as in Application Example 2). All electrochemical performance tests were measured under atmospheric conditions using a CHI650E and a NEWARE battery system (CT-3008).

[0093] Comparative Application Example 3

[0094] A RuO2+Pt / C catalyst was loaded onto nickel foam as the positive and negative electrodes to assemble a water electrolysis device. The water electrolysis device was directly driven by two flexible batteries connected in series, as described in Application Case 1, for hydrogen production.

[0095] Figure 1 SEM images of a self-supporting carbon-coated cobalt-iron / nickel-iron binary dual-phase alloy multifunctional oxygen electrode were prepared for Case 1. CoFe hydroxide nanosheets were grown on a nickel foam substrate via a hydrothermal method. After adsorption of Co-ZIF and high-temperature carbonization in an argon atmosphere, nickel in the nickel foam was dissolved, and high-temperature carbonization reduction yielded a composite material of nitrogen-doped carbon nanosheets with distributed metallic alloys CoFe and NiFe.

[0096] Figure 2XPS images for Example 1, Comparative Example 1, and Comparative Example 2 are shown below. (a) represents the full spectrum of Example 1, Comparative Example 1, and Comparative Example 2; (b) represents the Co 2p fitted spectrum of Example 1, Comparative Example 1, and Comparative Example 2; (c) represents the Fe 2p fitted spectrum of Example 1, Comparative Example 2; (d) represents the Ni 2p fitted spectrum of Example 1; (e) represents the N 1s fitted spectrum of Example 1, Comparative Example 1; and (f) represents the O 1s fitted spectrum of Example 1, Comparative Example 1, and Comparative Example 2. As can be seen from the figures, metallic Co... 0 Fe 0 and Ni 0 The coexistence of these elements is consistent with the XRD and HR-TEM results of the aforementioned biphase alloy-based catalysts, demonstrating the successful synthesis of CoFe-NiFe / NC.

[0097] Figure 3 (a) and (b), (c) and (d), (e) and (f), (g) and (h), (i) and (j), (k) and (l) are SEM images of the composite electrodes of Examples 2, 1, 3, 4, 5 and 6, respectively. When the temperature is increased from 450°C to 700°C, the complete nanosheets gradually disintegrate, the surface nanoparticles are refined, and then they fuse.

[0098] Figure 4 The XRD patterns of the composite electrodes of Example 1, Comparative Example 1, and Comparative Example 2 are shown; the characteristic peaks at 2θ = 44.80, 65.38, and 82.78 represent the CoFe alloy phase (PDF#49-1568), and the peaks at 43.98 are also shown.

[0099] The sharp peaks at 51.28 and 75.56 represent the NiFe alloy phase (PDF#12-0736), confirming the existence of a two-phase alloy in the CoFe-NiFe / NC catalyst. The broad peak centered at 26.40 indicates that the CoFe-NiFe / NC catalyst contains a large amount of carbon components.

[0100] Figure 5 TEM images of the self-supporting carbon-coated cobalt-iron / nickel-iron binary dual-phase alloy multifunctional oxygen electrode prepared in Example 1 are shown. HR-TEM images of the CoFe-NiFe / NC catalyst show that the nanoparticles are highly dispersed, approximately 20 nm in size, distributed on nanosheets. Individual nanoparticles are uniformly isolated and surrounded by several layers of carbon. The lattice spacing of 0.202 nm corresponds to the (110) crystal plane of the CoFe alloy phase, and the lattice fringe spacing of 0.206 nm corresponds to the (111) crystal plane of the NiFe alloy phase (1#, 3# in the figure). Furthermore, a continuous carbon shell with slight lattice distortion and a spacing of 0.340 nm was observed, matching the (002) crystal plane of graphitic carbon.

[0101] Figure 6 (a), (b), and (c) are OER / ORR / HER performance data graphs of the composite electrodes of Example 1 and Comparative Examples 1-2, respectively. It can be seen from the graphs that the catalyst obtained in Example 1 exhibits excellent OER / ORR / HER activity.

[0102] Figure 7 The figures show the OER / ORR / HER performance data of the composite electrodes in Examples 1-6, respectively. As can be seen from the figures, the best OER / ORR / HER activity is exhibited at a calcination temperature of 500℃, indicating that the most suitable calcination temperature is 500℃.

[0103] Figure 8 The graph shows the cycle performance of a liquid zinc-air battery assembled using the self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional oxygen electrode prepared in Example 1, and the liquid zinc-air battery assembled in Comparative Example 1, under constant current charge-discharge testing. Compared with Pt / C+RuO2, the liquid zinc-air battery based on CoFe-NiFe / NC exhibits better cycle performance at 10 mA / cm². -2 Under these conditions, there was no significant attenuation within 400 hours, and the voltage difference was only 0.79V, demonstrating good charge and discharge stability.

[0104] Figure 9 The voltage-specific capacity curves of the liquid zinc-air battery assembled using the self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional oxygen electrode prepared in Example 1 and the liquid zinc-air battery assembled in Comparative Example 1 were obtained through constant current discharge testing. At a high discharge voltage platform of 1.15V, the specific discharge capacity of the CoFe-NiFe / NC-based liquid zinc-air battery was 786 mAh g. Zn -1 It is higher than Pt / C+RuO2.

[0105] Figure 10 This image illustrates the practical application of the air cathode of a flexible solid-state zinc-air battery assembled from a self-supporting carbon-coated cobalt-iron / nickel-iron binary dual-phase alloy multifunctional oxygen electrode prepared in Example 2. Two series-connected flexible zinc-air batteries can continuously illuminate the "SCAU" LED panel with constant brightness in various bending states or when worn on the wrist. More notably, an everyday mobile phone can be easily charged using four series-connected flexible zinc-air batteries. All these demonstrations strongly validate the attractive practical potential of high-efficiency FZABs made from CoFe-NiFe / NC, showing promising applications in portable / flexible energy devices and smart wearable power supplies.

[0106] Figure 11Stability test results are shown for a flexible solid-state zinc-air battery assembled using the self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional oxygen electrode prepared in Example 1, and for a water electrolysis device powered by the flexible solid-state zinc-air battery assembled in Comparative Example 1. The composite material from Example 1 was used as the two electrodes for complete water electrolysis, and its stability at 20 mA / cm² was measured. -2 The required potential is 1.64V at a current density of 20mA / cm. -2 After 27 hours of testing, no significant performance degradation was observed. The performance test results of the above devices indicate that the composite material of Example 1 has good application potential in zinc-air batteries and all-water electrolysis applications.

[0107] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst, characterized in that... Includes the following steps: (1) Disperse cobalt salt, iron salt, urea and ammonium fluoride into water and stir to form a uniform solution; (2) Transfer the solution obtained in step (1) and the nickel foam conductive substrate together to a high-pressure reactor for reaction. After the reaction is completed, remove the electrode, rinse and dry it. (3) Dissolve cobalt salt and polyvinylpyrrolidone in a solvent to obtain solution A; dissolve organic ligand in a solvent to obtain solution B; soak the electrode dried in step (2) in solution A, then add solution B to solution A to react, and finally wash and dry the obtained electrode for later use. (4) The electrode obtained in step (3) is calcined in an inert atmosphere to obtain a self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst.

2. The preparation method of the self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst according to claim 1, characterized in that: The cobalt salt mentioned in step (1) is at least one of cobalt nitrate hexahydrate, cobalt acetate tetrahydrate, and cobalt sulfate heptahydrate; The iron salt mentioned in step (1) is at least one of ferric nitrate nonahydrate, ferric sulfate heptahydrate, and ferric acetate; The molar ratio of cobalt salt, iron salt, urea and ammonium fluoride mentioned in step (1) is (1-5):1:(1-15):

8.

3. The preparation method of the self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst according to claim 1, characterized in that: The concentration of cobalt salt in the homogeneous solution formed in step (1) is 0.01 mol / L to 0.04 mol / L; The amounts of solution and nickel foam conductive substrate mentioned in step (2) are such that the nickel foam conductive substrate is completely immersed in the solution, and the solution does not exceed 2 / 3 of the volume of the reactor.

4. The preparation method of the self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst according to claim 1, characterized in that: The reaction described in step (2) refers to a reaction at 100-180℃ for 4-12 hours.

5. The preparation method of the self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst according to claim 1, characterized in that: The cobalt salt mentioned in step (3) is at least one of cobalt nitrate hexahydrate, cobalt acetate tetrahydrate, and cobalt sulfate heptahydrate; The organic ligand mentioned in step (3) is at least one of dimethylimidazole, N,N-dimethylformamide, and benzotricarboxylic acid; The ratio of cobalt salt to polyvinylpyrrolidone used in step (3) is 1 mmol: 0.1 g to 8 mmol: 2 g; the amount of solvent used in solution A is such that the concentration of cobalt salt in solution A is 20-60 mmol / L. In step (3), the solvent in solution A and solution B is the same, which is one of methanol, ethanol, and isopropanol; The concentration of the organic ligand in solution B mentioned in step (3) is 100–600 mmol / L; The molar ratio of cobalt salt and organic ligand in step (3) is 1:20-1:

1.

6. The preparation method of the self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst according to claim 1, characterized in that: The soaking time in solution A mentioned in step (3) is 10 min to 60 min; the reaction mentioned in step (3) refers to the reaction at 20-30℃ for 12-24 h.

7. The preparation method of the self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst according to claim 1, characterized in that: The molar ratio of the organic ligand described in step (3) to the iron salt described in step (1) is 10:1-60:

1.

8. The preparation method of the self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst according to claim 1, characterized in that: The calcination mentioned in step (4) refers to heating to 450-700℃ at a heating rate of 1-5℃ / min and reacting for 1-5 hours.

9. A self-supporting carbon-coated cobalt-iron / nickel-iron binary dual-phase alloy multifunctional catalyst prepared by the method according to any one of claims 1-8.

10. The application of the self-supporting carbon-coated cobalt-iron-nickel-iron binary dual-phase alloy multifunctional catalyst according to claim 9 in zinc-air batteries, flexible wearable devices, and water splitting.

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