A cobalt-iron-based electrocatalyst with a wheat ear-shaped superhydrophilic-superair-repellent structure and application thereof

Abstract

This invention discloses a wheat-ear-shaped superhydrophilic-superhydrophobic cobalt-iron-based electrocatalyst and its application. The cobalt-iron-based electrocatalyst is prepared using the following method, which includes the following steps: First, a nanoneedle-shaped cobalt-iron-based bimetallic hydroxide precursor is grown on a porous metal substrate using a hydrothermal method; Second, the precursor is sequentially immersed in a pyrrole solution and an oxidant solution, and conductive polypyrrole nanospheres are formed on the surface of the precursor through oxidative polymerization of pyrrole; Third, the porous metal substrate is immersed in a sodium sulfide solution or sodium thiosulfate solution at 50℃~70℃ for 1h~2h to perform surface sulfidation of the precursor. The cobalt-iron-based electrocatalyst of this application possesses excellent superhydrophilic and superhydrophobic properties, as well as excellent catalytic activity. When applied to water electrolysis for hydrogen production, it can improve the overall performance of the water electrolysis system; furthermore, the method of this application is simple, the conditions are controllable, and it is easy to implement on a large scale.

Description

Technical Field

[0001] This application belongs to the field of catalyst technology, specifically relating to a wheat-ear-shaped superhydrophilic-superhydrophobic cobalt-iron-based electrocatalyst and its application. Background Technology

[0002] Electrolysis of water is one of the most promising methods for producing green hydrogen. During electrolysis, if the continuously generated gas on the electrode surface cannot be quickly removed, it will adhere to and gradually accumulate, forming a bubble layer on the electrode surface. These bubbles cover active sites, increasing ion transport resistance, leading to uneven local current density distribution, increased reaction overpotential, and potentially causing stress corrosion and structural spalling of the electrode material, thus severely limiting the energy efficiency and long-term operational stability of the electrolyzer. Therefore, effectively controlling the wetting characteristics of the electrode surface to achieve rapid gas generation and immediate desorption is one of the key technical issues for improving the overall performance of water electrolysis systems. Summary of the Invention

[0003] The purpose of this application is to provide a wheat-ear-shaped superhydrophilic-superhydrophobic cobalt-iron-based electrocatalyst and its application. The cobalt-iron-based electrocatalyst of this application has both excellent wetting properties and catalytic activity, and can achieve rapid desorption of gases.

[0004] On the one hand, this application provides a wheat-ear-shaped superhydrophilic-superhydrophobic cobalt-iron-based electrocatalyst, which is prepared by the following method, the preparation method comprising the following steps in sequence: The first step involves growing a cobalt-iron base layer precursor in the form of nanoneedle arrays on a porous metal substrate using a hydrothermal method. The second step involves sequentially immersing the precursor in a pyrrole solution and an oxidant solution, and then polymerizing the pyrrole on the surface of the precursor through an oxidative polymerization reaction to form conductive polypyrrole nanospheres. The third step involves immersing the porous metal substrate in a sodium sulfide solution or sodium thiosulfate solution at 50°C to 70°C for 1 to 2 hours to perform surface sulfidation on the precursor.

[0005] In the first step, a cobalt-iron-based bimetallic hydroxide precursor in the form of an array of nanoneedles is grown on a porous metal substrate via a hydrothermal reaction. In the second step, conductive polypyrrole nanospheres (PPy nanospheres) are polymerized on the surface of the nanoneedles via an oxidative polymerization reaction. The PPy nanospheres are distributed on the surface of the nanoneedles, constructing a biomimetic "wheat ear" morphological structure. In the third step, due to the pores between the PPy nanospheres, sulfur elements contact the surface of the nanoneedles through the pores, thereby partially and mildly sulfurizing the surface of the nanoneedles, thus obtaining a cobalt-iron-based electrocatalyst with a sandwich structure of "layered substrate - metal sulfide active layer - polymer encapsulation".

[0006] Specifically, the first step above includes: Soluble cobalt salt, soluble iron salt, ammonium fluoride, and urea are dissolved in water to obtain a mixed solution; The porous metal substrate is immersed in the mixed solution and heated to 100℃~150℃ and kept at the temperature for 6h~8h to carry out a hydrothermal reaction.

[0007] Optionally, the molar ratio of cobalt in soluble cobalt salt, iron in soluble iron salt, ammonium fluoride, and urea is 1~2:1~2:5~10:5~20.

[0008] Optionally, the concentrations of cobalt, iron, ammonium fluoride, and urea in the mixed solution are 0.05~0.1 mmol / mL, 0.05~0.1 mmol / mL, 0.25~0.5 mmol / mL, and 0.25~1 mmol / mL, respectively.

[0009] Alternatively, the porous metal substrate may be nickel foam or copper foam.

[0010] Specifically, in the second step above, the concentration of the pyrrole solution is 1~8 μL / mL, and the concentration of the oxidant solution is potassium persulfate solution, which is 1~4 mol / mL.

[0011] Optionally, in the second step above, the cyclic impregnation operation is repeated 8 to 12 times. The impregnation operation refers to the operation of sequentially impregnating the precursor with pyrrole solution and oxidant solution, with each impregnation time being 10 to 20 seconds.

[0012] Specifically, in the third step above, the concentration of sodium sulfide solution or sodium thiosulfate solution is 0.05~0.2 mol / L.

[0013] On the other hand, this application also provides the application of the above-mentioned wheat-ear-shaped superhydrophilic-superhydrophobic cobalt-iron-based electrocatalyst as a catalytic electrode in water electrolysis for hydrogen production.

[0014] The cobalt-iron-based electrocatalyst of this application has the following characteristics: On the one hand, LDH nanoneedle arrays can provide an ideal channel for the rapid nucleation and escape of bubbles; On the other hand, the introduction of PPy nanospheres not only endows the catalyst with excellent conductivity, but also allows for the control of interfacial energy through close integration with the LDH nanoneedle array. Specifically, the PPy conductive polymer has a conjugated π-electron system. When it is closely integrated with the LDH nanoneedles, a heterojunction is formed. Electrons are transferred at the interface of the heterojunction until the Fermi level reaches equilibrium, thus achieving the purpose of controlling the interfacial energy in the process. On the other hand, the mild introduction of sulfur atoms to partially modify the surface of LDH nanoneedles does not damage the PPy conductive layer, but enhances the capillary effect on the catalyst surface. Through synergy with the LDH nanoneedle array and PPy nanospheres, ultra-low bubble adhesion and further performance improvement are achieved.

[0015] Therefore, the technical solution provided in this application may include the following beneficial effects: The cobalt-iron-based electrocatalyst of this application possesses excellent superhydrophilicity and superhydrophobicity, as well as excellent catalytic activity. When applied to hydrogen production through water electrolysis, it can improve the overall performance of the water electrolysis system. Furthermore, the method of this application is simple, the conditions are controllable, and it is easy to implement on a large scale.

[0016] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0017] The above and other objects, features and advantages of this application will become more apparent from the following description of exemplary embodiments of this application in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments of this application.

[0018] Figure 1 This is a schematic diagram of the preparation process of the S-CoFe-LDHs@PPy electrocatalyst in the examples; Figure 2 This is a scanning electron microscope image of the CoFe-LDHs precursor in Example 2; Figure 3 This is a scanning electron microscope image of the S-CoFe-LDHs@PPy electrocatalyst in Example 2; Figure 4 The image shows a scanning electron microscope (SEM) image of the NiFe-LDHs@PPy electrocatalyst prepared in Comparative Example 2. Figure 5 The XRD patterns of the CoFe-LDHs precursor, CoFe-LDHs@PPy electrocatalyst, and S-CoFe-LDHs@PPy electrocatalyst in Example 2 are shown below. Figure 6 Raman spectra of the CoFe-LDHs precursor, CoFe-LDHs@PPy electrocatalyst, and S-CoFe-LDHs@PPy electrocatalyst in Example 2; Figure 7 The graph shows the hydrophilic and gas-repellent properties of the CoFe-LDHs precursor in Example 2. Figure 8 The graph shows the hydrophilic and gas-repellent properties of the CoFe-LDHs@PPy electrocatalyst in Example 2. Figure 9 The graph shows the hydrophilic and gas-repellent properties of the S-CoFe-LDHs@PPy electrocatalyst in Example 2. Figure 10The graph shows the hydrophilic and gas-repellent properties of the NiFe-LDHs@PPy electrocatalyst prepared in Comparative Example 2. Figure 11 HER linear sweep polarization curves of S-CoFe-LDHs@PPy electrocatalyst, CoFe-LDHs@PPy electrocatalyst, and NiFe-LDHs@PPy electrocatalyst; Figure 12 The OER linear sweep polarization curves of S-CoFe-LDHs@PPy electrocatalyst, CoFe-LDHs@PPy electrocatalyst, and NiFe-LDHs@PPy electrocatalyst are shown. Detailed Implementation

[0019] The following will describe this application and its technical effects in detail with reference to specific embodiments and examples. Those skilled in the art should understand that these specific embodiments and examples are for illustrative purposes only and are not intended to limit the scope of this application.

[0020] Please see Figure 1 The diagram illustrates the preparation process of the S-CoFe-LDHs@PPy electrocatalyst in this embodiment. The process mainly includes: First, using pretreated nickel foam NF as a three-dimensional conductive substrate, vertically aligned cobalt-iron layered bimetallic hydroxide nanoneedles are grown in situ on its surface via a hydrothermal method. Then, a layer of polypyrrole conductive polymer is uniformly coated onto the nanoneedles through in-situ polymerization, forming a core-shell structured CoFe-LDHs@PPy composite array. Finally, the nanoneedles are surface-modified through a mild liquid-phase sulfidation treatment, introducing a cobalt-iron sulfide phase without damaging the overall morphology, thereby constructing an integrated catalytic electrode with a unique "wheat ear" hierarchical rough structure and superhydrophilic-superhydrophobic interface properties. This method is simple, with controllable conditions, and allows for the synergistic design and precise control of catalyst structure, composition, and interface function.

[0021] All raw materials used in this application are not subject to any particular restrictions on their source; they can be purchased commercially or prepared using conventional methods known to those skilled in the art.

[0022] Detailed embodiments and comparative examples will be provided below. Example 1

[0023] The specific preparation steps of the catalytic electrode in this embodiment are as follows: (1) Pretreatment of nickel foam NF: First, take 2×3cm 2The NF was ultrasonically treated with acetone and dilute HCl solution for 20 min in sequence to remove oil and oxide layer from the surface of NF; then, it was ultrasonically washed with deionized water and anhydrous ethanol for 20 min in sequence, and repeated three times; finally, it was dried in a vacuum drying oven at 60°C to obtain clean NF.

[0024] (2) Preparation of CoFe-LDHs precursors: First, 1 mmol of cobalt nitrate, 1 mmol of ferric nitrate, 5 mmol of ammonium fluoride, and 5 mmol of urea were dissolved in 20 mL of deionized water and stirred magnetically for 1 h to obtain a mixed solution. Then, the mixed solution was transferred to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene (PTFE), and NF was placed in the solution. The reactor was heated at 120 °C for 6 h for a constant-temperature hydrothermal reaction. During the reaction, a layered bimetallic hydroxide nanoneedle array grew on the surface of NF. Finally, after the hydrothermal reactor cooled to room temperature, the sample was washed multiple times with ultrapure water and anhydrous ethanol, and then dried in a vacuum drying oven at 60 °C for 12 h.

[0025] (3) Preparation of CoFe-LDHs@PPy electrocatalyst: First, 100 μL of pyrrole was dispersed in a beaker containing 50 mL of ultrapure water to obtain a pyrrole solution. 0.1 mol of potassium persulfate was dissolved in another beaker containing 50 mL of ultrapure water to obtain a potassium persulfate solution. Then, the CoFe-LDHs precursor was sequentially immersed in the pyrrole solution and the potassium persulfate solution, with each immersion lasting 20 seconds, for a total of 20 immersions (10 immersions in each solution). During the immersion process, conductive polypyrrole nanospheres were polymerized on the surface of the nanoneedles using a nanoneedle array as a template. Finally, the sample was washed multiple times with ultrapure water and anhydrous ethanol, and dried in a vacuum drying oven at 60 °C for 12 h.

[0026] (4) Preparation of S-CoFe-LDHs@PPy electrocatalyst: First, the CoFe-LDHs@PPy electrocatalyst was impregnated in a sodium sulfide solution at 60°C for 1 hour. The concentration of the sodium sulfide solution was 0.1 mol / L. During this impregnation process, sulfur ions were introduced to modify the surface of the electrocatalyst. Then, the sample was washed multiple times with ultrapure water and anhydrous ethanol, and dried in a vacuum drying oven at 60°C for 12 hours. Example 2

[0027] The only difference between this embodiment and embodiment 1 is the amount of pyrrole used in step (3). In this embodiment, the amount of pyrrole used is 200 μL, that is, 200 μL of pyrrole is dispersed in a beaker containing 50 mL of ultrapure water to obtain a pyrrole solution. Example 3

[0028] The only difference between this embodiment and embodiment 1 is the amount of pyrrole used in step (3). In this embodiment, the amount of pyrrole used is 300 μL, that is, 300 μL of pyrrole is dispersed in a beaker containing 50 mL of ultrapure water to obtain a pyrrole solution.

[0029] Comparative Example 1 The specific preparation steps of the catalytic electrode in this comparative example are as follows: (1) Pretreatment of nickel foam NF: First, take 2×3cm 2 The NF was ultrasonically treated with acetone and dilute HCl solution for 20 min in sequence to remove oil and oxide layer from the surface of NF; then, it was ultrasonically washed with deionized water and anhydrous ethanol for 20 min in sequence, and repeated three times; finally, it was dried in a vacuum drying oven at 60°C to obtain clean NF.

[0030] (2) Preparation of NiFe-LDHs precursor: First, 0.5 mmol nickel nitrate, 0.5 mmol ferric nitrate, 5 mmol ammonium fluoride, and 5 mmol urea were dissolved in 20 mL of deionized water and stirred magnetically for 1 h to obtain a blue-green mixed solution. Then, the mixed solution was transferred to a stainless steel hydrothermal reactor lined with polytetrafluoroethylene (PTFE), and NF was placed in the solution. The reactor was heated at 120 °C for 6 h for a constant-temperature hydrothermal reaction. During the reaction, layered bimetallic hydroxide nanosheets grew on the surface of NF. Finally, after the hydrothermal reactor cooled to room temperature, the sample was washed multiple times with ultrapure water and anhydrous ethanol, and then dried in a vacuum drying oven at 60 °C for 12 h.

[0031] (3) Preparation of NiFe-LDHs@PPy electrocatalyst: First, 100 μL of pyrrole was dispersed in a beaker containing 50 mL of ultrapure water to obtain a pyrrole solution. 0.1 mol of potassium persulfate was dissolved in another beaker containing 50 mL of ultrapure water to obtain a potassium persulfate solution. Then, the NiFe-LDHs precursor was sequentially immersed in the pyrrole solution and the potassium persulfate solution, with each immersion lasting 20 seconds, for a total of 20 immersions (10 immersions in each solution). During the immersion process, conductive polypyrrole nanospheres were formed on the surface of the nanosheets using a nanosheet array as a template. Finally, the sample was washed multiple times with ultrapure water and anhydrous ethanol, and dried in a vacuum drying oven at 60 °C for 12 h.

[0032] Comparative Example 2 The only difference between this comparative example and Comparative Example 1 is the amount of pyrrole used in step (3). In this comparative example, the amount of pyrrole used is 200 μL, that is, 200 μL of pyrrole is dispersed in a beaker containing 50 mL of ultrapure water to obtain a pyrrole solution.

[0033] Comparative Example 3 The only difference between this comparative example and Comparative Example 1 is the amount of pyrrole used in step (3). In this comparative example, the amount of pyrrole used is 300 μL, that is, 300 μL of pyrrole is dispersed in a beaker containing 50 mL of ultrapure water to obtain a pyrrole solution.

[0034] Please see Figures 2-3 The image shows a scanning electron microscope (SEM) image of the CoFe-LDHs precursor and the S-CoFe-LDHs@PPy electrocatalyst from Example 2. Figures 2-3 It is evident that the CoFe-LDHs precursor exhibits an ordered, tightly packed nanoneedle morphology, while the S-CoFe-LDHs@PPy electrocatalyst has a uniform layer of nanospheres coated on the nanoneedles, forming a biomimetic "wheat ear" structure. This biomimetic "wheat ear" structure is a multi-level structure composed of a main nanoneedle and densely packed secondary nanospheres on its surface, resulting in a significantly increased specific surface area and a multiplied number of active sites. Simultaneously, the constructed crisscrossing open pore network significantly promotes electrolyte wetting and ion transport, and also provides low-resistance escape channels for reaction bubbles, enabling efficient gas-liquid mass transfer and thus optimizing superhydrophilic and superhydrophobic properties. Furthermore, this microstructure provides a mutually supporting and stable framework, effectively inhibiting the aggregation and collapse of active materials during cycling, thereby enhancing the stability of mechanical and electrochemical properties. The tight interface formed between the main and secondary structures can regulate local electron distribution, inducing a synergistic catalytic effect and further enhancing intrinsic activity.

[0035] Please see Figure 5 The figure shows the XRD patterns of the CoFe-LDHs precursor, CoFe-LDHs@PPy electrocatalyst, and S-CoFe-LDHs@PPy electrocatalyst in Example 2; wherein, spectra (a) to (c) are the XRD patterns of the S-CoFe-LDHs@PPy electrocatalyst, CoFe-LDHs@PPy electrocatalyst, and CoFe-LDHs precursor, respectively.

[0036] from Figure 5 It can be seen that the XRD patterns of spectra (a) to (c) all show obvious characteristic diffraction peaks of LDHs at 11.7°, 23.5°, 34.5°, and 60.2°, corresponding to the (003), (006), (012), and (110) crystal planes, respectively, indicating that the material retains its main layered crystal structure after polymer coating and sulfidation treatment. Compared with the CoFe-LDHs precursor and CoFe-LDHs@PPy electrocatalyst, the characteristic diffraction peak intensity of S-CoFe-LDHs@PPy electrocatalyst is significantly reduced, indicating that under mild sulfidation, S... 2- Partially replaced the OH between the layers - and the O on the shelf 2-This leads to a decrease in the crystallinity of the layered structure, possibly accompanied by subtle changes in lattice microstrain and grain size, indicating that surface sulfidation modification has been successfully achieved. These subtle changes in lattice microstrain and grain size are beneficial for controlling the electronic structure and surface properties of the material, thereby optimizing its electrocatalytic performance.

[0037] Please see Figure 6 The image shows the Raman spectra of the CoFe-LDHs precursor, CoFe-LDHs@PPy electrocatalyst, and S-CoFe-LDHs@PPy electrocatalyst in Example 2; wherein, spectra (a) to (c) are the Raman spectra of the S-CoFe-LDHs@PPy electrocatalyst, CoFe-LDHs@PPy electrocatalyst, and CoFe-LDHs precursor, respectively.

[0038] from Figure 6 It can be seen that the CoFe-LDHs precursor has a Raman shift of approximately 458 cm⁻¹. -1 and 528 cm -1 At a certain point, characteristic Raman peaks of layered bimetallic hydroxides appeared, corresponding to the stretching vibrations of the metal-oxygen (MO) bond and the bending vibrations of the interlayer hydroxyl groups, confirming the existence of the layered structure. Compared with the CoFe-LDHs precursor and the CoFe-LDHs@PPy electrocatalyst, the intensity of the MO bond characteristic peak of the S-CoFe-LDHs@PPy electrocatalyst was significantly weakened and red-shifted, with a Raman shift of approximately 300 cm⁻¹. -1 The appearance of new Co-S bond characteristic Raman peaks confirms that S during the sulfidation process... 2- The O species on the CoFe-LDHs laminations were effectively substituted, forming active sites for metal sulfides, and the polymer coating did not hinder the sulfidation reaction.

[0039] The changes in the Raman spectra shown above indicate that, after polymer coating and sulfidation modification, a composite structure of "layered substrate-metal sulfide active layer-polymer coating" was successfully constructed in this application. This composite structure optimizes the electronic conduction efficiency of the electrocatalyst on the one hand, and introduces highly active metal sulfur species on the other hand, providing a structural and chemical basis for improving the electrocatalytic performance.

[0040] Please see Figures 7-9 The graphs show the hydrophilicity and gas-phobicity test spectra of the CoFe-LDHs precursor, CoFe-LDHs@PPy electrocatalyst, and S-CoFe-LDHs@PPy electrocatalyst in Example 2. Figures 7-9It can be seen that the CoFe-LDHs precursor, CoFe-LDHs@PPy electrocatalyst, and S-CoFe-LDHs@PPy electrocatalyst all have excellent hydrophilicity. The bubble contact angle of the CoFe-LDHs precursor is 151.3°, that of the CoFe-LDHs@PPy electrocatalyst is 152.8°, and that of the S-CoFe-LDHs@PPy electrocatalyst is 154.3°. This shows that sulfidation can further improve the hydrophilicity and gas-repellent properties of the electrocatalyst.

[0041] In the CoFe-LDHs precursor, the abundant hydroxyl groups in its layered structure form strong hydrogen bonds with water molecules, exhibiting excellent hydrophilicity. In the CoFe-LDHs@PPy electrocatalyst, PPy nanospheres are distributed on the surface of nanoneedles to form a PPy coating layer, exhibiting a biomimetic "wheat ear" composite structure in its microstructure, which enhances the gas-repellency of the material. The reduced surface area for bubble adhesion weakens the adhesion force, making it easier for bubbles to detach from the material surface. After the introduction of sulfur ions, the bubble contact angle of the S-CoFe-LDHs@PPy electrocatalyst is 154.3°. The synergistic effect of the PPy nanosphere-modified surface structure and the Co-S bonds formed after sulfidation further enhances the gas-repellency. The optimization of gas-repellency by the PPy coating layer structure can effectively inhibit the adsorption and aggregation of gases generated in the electrocatalytic reaction on the material surface, preventing the active sites from being covered. Combined with the stable maintenance of hydrophilicity and the enhancement after sulfidation, the electrocatalytic reaction kinetics and long-term stability of the material are synergistically improved.

[0042] Please see Figure 4 The image shown is a scanning electron microscope (SEM) image of the NiFe-LDHs@PPy electrocatalyst prepared in Comparative Example 2. From... Figure 4 As can be seen, the NiFe-LDHs precursor exhibits a two-dimensional nanosheet morphology, uniformly grown on the NF framework, while PPy nanospheres are tightly and uniformly coated on the nanosheet surface, forming a composite structure. Compared to the two-dimensional nanosheet structure, the nanoneedle structure of this application can provide more channels and better gas-repellency; at the same time, it can also provide more electrochemical active sites and has superior electrocatalytic activity.

[0043] Please see Figure 10 The image shows the hydrophilicity and gas-phobicity test spectrum of the NiFe-LDHs@PPy electrocatalyst prepared in Comparative Example 2; combined with... Figures 7-10 It is evident that the CoFe-LDHs@PPy electrocatalyst and the S-CoFe-LDHs@PPy electrocatalyst prepared in this application exhibit significantly superior hydrophilicity and gas-repellency.

[0044] The inventor's analytical mechanism may be: First, Co 2+ Its electronegativity is lower than that of Ni 2+The stronger local positive electric field formed on the surface of the laminate facilitates enhanced adsorption of water molecules through electrostatic interactions; simultaneously, CoFe-LDH intrinsically possesses a higher surface hydroxyl density, which is beneficial for forming hydrogen bonds with water molecules. Secondly, Co... 2+ The d-electron configuration of Co makes it easier for it to coordinate with the N atom in PPy, inducing more polaron states on the PPy chain, thereby exposing more polar sites and further enhancing hydrophilicity. In addition, Co... 2+ The faster nucleation rate results in smaller LDH crystal size and higher surface roughness, which is beneficial for stabilizing the Cassie-Baxter gas-solid contact state; combined with Co 2+ / Co 3+ The redox activity promotes the uniform polymerization of PPy to form a low surface energy gas-repellent layer, and the intrinsic weak adsorption characteristics of CoFe-LDH on gas molecules together reduce the adhesion of bubbles on the electrode surface, thereby significantly enhancing the gas-repellency.

[0045] Please see Figures 11-12 The figures show linear sweep polarization curves for electrocatalytic hydrogen evolution (HER) and oxygen evolution (OER), respectively. The test samples included the CoFe-LDHs@PPy electrocatalyst and S-CoFe-LDHs@PPy electrocatalyst prepared in Example 2, and the NiFe-LDHs@PPy electrocatalyst prepared in Comparative Example 2. The test conditions were as follows: in a standard three-electrode system, 1 MkOH was used as the electrolyte, a graphite rod as the counter electrode, and mercury / mercuric oxide as the reference electrode. Cyclic voltammetry (CV) activation was performed before linear sweep voltammetry (LSV) testing until a consistent voltammogram was obtained. LSV was performed at 3 mV / s without iR correction, and all potentials were referenced to the reversible hydrogen electrode. Figures 11-12 As can be seen, the S-CoFe-LDHs@PPy electrocatalyst exhibited the lowest overpotential in both the HER and OER processes, indicating that it has significantly optimal electrocatalytic activity.

[0046] This application employs an in-situ hydrothermal method and a mild impregnation method to prepare an electrocatalyst. A vertically aligned array of nanoneedles encapsulated by polymer microspheres is grown on a nickel foam substrate. Compared to the two-dimensional nanosheet structure in the comparative example, the unique core-shell hierarchical array constructed in this application offers multiple advantages. The one-dimensional nanoneedle structure provides a superior electron transport path and higher mechanical stability. The uniformly encapsulated microspheres and sulfurization modification not only significantly enhance the overall hydrophilicity and electrolyte wettability but also effectively suppress the structural collapse of the nanoneedles during cycling through their elastic buffering effect, thereby protecting the loss of active sites. Furthermore, the synergistic effect of this special morphology and sulfurization modification endows the electrode surface with excellent superhydrophobic properties, ensuring rapid desorption of generated bubbles and significantly reducing mass transfer resistance. This method offers controllable processes and mild conditions, and the prepared integrated catalytic electrode exhibits significantly enhanced reactivity and long-term operational stability in alkaline electrolytes.

[0047] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A wheat-ear-shaped superhydrophilic-superhydrophobic cobalt-iron-based electrocatalyst, characterized in that: The cobalt-iron-based electrocatalyst is prepared by the following method, which includes the following steps: The first step involves growing a nanoneedle-shaped cobalt-iron layered bimetallic hydroxide precursor on a porous metal substrate using a hydrothermal method; the process further includes: dissolving soluble cobalt salt, soluble iron salt, ammonium fluoride, and urea in water to obtain a mixed solution; immersing the porous metal substrate in the mixed solution, heating it to 100℃~150℃, and holding it at that temperature for 6h~8h to carry out a hydrothermal reaction. The second step involves sequentially immersing the precursor in a pyrrole solution and an oxidant solution, and then polymerizing the pyrrole on the surface of the precursor through an oxidative polymerization reaction to form conductive polypyrrole nanospheres. The third step involves immersing the porous metal substrate in a sodium sulfide solution or sodium thiosulfate solution at 50°C to 70°C for 1 to 2 hours to perform surface sulfidation on the precursor. The molar ratio of cobalt in the soluble cobalt salt, iron in the soluble iron salt, ammonium fluoride, and urea is 1~2:1~2:5~10:5~20.

2. The wheat-ear-shaped superhydrophilic-superhydrophobic cobalt-iron-based electrocatalyst as described in claim 1, characterized in that: The concentrations of cobalt, iron, ammonium fluoride, and urea in the mixed solution are 0.05~0.1 mmol / mL, 0.05~0.1 mmol / mL, 0.25~0.5 mmol / mL, and 0.25~1 mmol / mL, respectively.

3. The wheat-ear-shaped superhydrophilic-superhydrophobic cobalt-iron-based electrocatalyst as described in claim 1, characterized in that: The porous metal substrate is nickel foam or copper foam.

4. The wheat-ear-shaped superhydrophilic-superhydrophobic cobalt-iron-based electrocatalyst as described in claim 1, characterized in that: In the second step, the concentration of the pyrrole solution is 1~8 μL / mL, and the oxidant solution is potassium persulfate solution.

5. The wheat-ear-shaped superhydrophilic-superhydrophobic cobalt-iron-based electrocatalyst as described in claim 1, characterized in that: in In the second step, the cyclic immersion operation is repeated 8 to 12 times. The immersion operation refers to the operation of sequentially immersing the porous metal substrate in pyrrole solution and oxidant solution, with each immersion time being 10 to 20 seconds.

6. The wheat-ear-shaped superhydrophilic-superhydrophobic cobalt-iron-based electrocatalyst as described in claim 1, characterized in that: In the third step, the concentration of the sodium sulfide solution or the sodium thiosulfate solution is 0.05~0.2 mol / L.

7. The application of the wheat-ear-shaped superhydrophilic-superhydrophobic cobalt-iron-based electrocatalyst as described in any one of claims 1 to 6 as a catalytic electrode in water electrolysis for hydrogen production.

Images