Flexible electrode with vertical gradient hierarchical ordered topological network structure and preparation method thereof

Abstract

The invention provides a flexible electrode with a vertical gradient hierarchical ordered topological network structure and a preparation method thereof, which are characterized in that molecular structure design and template engineering are combined, and polyethylene glycol diacrylate (PEGDA) with a hydrophilic functional group is selected as a polymer substrate; a polar group in a molecular chain of the polymer forms multiple interactions with a conductive polymer PEDOT: PSS and reduced graphene oxide (rGO), and a stable three-dimensional network framework is constructed. A temperature response type template agent and photonic crystal template method combined technology is adopted, a multi-stage continuous ion channel with a bionic capillary effect is formed, the capillary pressure gradient of a system is enhanced, electrolyte wettability and substance diffusion kinetics are remarkably improved, and interface mass transfer impedance is reduced. Meanwhile, the mechanical strength is improved through stress gradient transmission, and the long-term stability of multiple cycles of the flexible electrode is enhanced.

Description

Technical Field

[0001] The present invention relates to the field of flexible electrodes, and in particular to a flexible electrode with a vertical gradient hierarchical ordered topological network structure and a preparation method thereof. Background Art

[0002] Flexible electrodes are core components of wearable devices, flexible energy storage systems and bioelectronic devices. Their performance directly determines the energy density, mechanical reliability and dynamic service life of the devices.

[0003] Current mainstream commercial flexible electrodes (such as 3M VFlex TM 、TDK FlexElast TM ) generally adopts a homogeneous porous structure design. Although it has basic flexibility, it faces three common problems: First, the inversion contradiction between mechanical and electrochemical properties is prominent. When the porosity exceeds 80%, the bending strength drops sharply to below 15MPa, while strengthening the mechanical properties will cause the ion diffusion coefficient to decay to 10 -10 m 2 / s level; secondly, the dynamic stability is insufficient, 4 After the first bending cycle, stress concentration causes crack expansion, and the interface contact resistance surges by more than 50%; thirdly, the high-rate performance is limited, and the capacity retention rate is less than 55% during 10C charging and discharging, which seriously restricts its application in fast response scenarios.

[0004] Therefore, there is an urgent need to design a flexible electrode and preparation method that can break the contradiction between the energy storage density and mechanical tolerance of flexible electrodes. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a flexible electrode with a vertical gradient hierarchical ordered topological network structure and a preparation method thereof.

[0006] The technical solutions adopted by the present invention are as follows:

[0007] The first aspect of the present invention provides a flexible electrode having a vertical gradient hierarchical ordered topological network structure, which includes an inverse opal composite film having multi-level pores, palladium-based active sites adsorbed within the multi-level pores, and an Ag-Ni bimetallic heterostructure in situ grown on the palladium-based active sites within the multi-level pores.

[0008] The multi-level pore channel includes at least two groups of interpenetrating single-level pore layers, and the single-level pore layers are composed of regularly arranged spherical air holes with the same diameter. The diameters of the spherical air holes in different single-level pore layers vary in a gradient.

[0009] Preferably, the gradient variation range of the diameter of the spherical air pores in the different single-stage pore layers is 2.5 μm to 50 nm.

[0010] A second aspect of the present invention provides a method for preparing a flexible electrode having a vertical gradient hierarchical ordered topological network structure, comprising the following steps:

[0011] S1. Using a vertical pulling coating method, SiO2 microsphere dispersions of different particle sizes are deposited layer by layer on a substrate according to a particle size gradient to form a multi-level opal template;

[0012] S2, filling the composite membrane slurry into the multi-level opal template for solidification, and removing the template to obtain an inverse opal composite membrane with multi-level pores;

[0013] S3, activating the inverse opal composite membrane using a palladium complex to obtain an inverse opal composite membrane loaded with palladium-based active sites;

[0014] S4, immersing the inverse opal composite film loaded with palladium-based active sites in a nickel-containing plating solution containing a reducing agent, and causing Ni nanoparticles to in situ grow on the inverse opal composite film loaded with palladium-based active sites through an autocatalytic reduction reaction, thereby obtaining a Ni-loaded inverse opal composite film;

[0015] S5, immersing the Ni-loaded inverse opal composite film into a silver-containing plating solution, and using capillary force to drive the Ag + It migrates directionally to the inner wall of the pores of the inverse opal composite membrane to obtain an inverse opal composite membrane loaded with Ag-Ni bimetallic heterostructure.

[0016] Preferably, in step S2, the method for preparing the composite membrane slurry comprises the following steps:

[0017] (A) Ethoxylated trimethylolpropane triacrylate monomer, polyethylene glycol diacrylate monomer, and acrylic acid monomer were weighed in a volume ratio of 1:(2.5-3.5):(0.2-0.8), and 0.8%-1.2% of 2-hydroxy-2-methyl-1-phenyl-1-propanone based on the total monomer volume was added and thoroughly mixed until a homogeneous transparent solution was formed, which was recorded as PEA;

[0018] (B) PEDOT and PSS were weighed in a mass ratio of 1:(100-140), ultrapure water and dimethyl sulfoxide were added sequentially, and the mixture was stirred to obtain a PEDOT:PSS solution.

[0019] (C) PEA, PEDOT:PSS, and rGO powders were mixed in a mass ratio of (8-12):1:(0.5-1.5) and then sheared and emulsified to obtain a PEA-PEDOT:PSS-rGO composite membrane slurry.

[0020] Preferably, in step (C), the method for preparing the rGO powder comprises the following steps:

[0021] Mixing a graphene oxide dispersion having a concentration of 1-3 g / L with a hydrogen peroxide solution having a concentration of 20-30% in a volume ratio of (8-12):1, and hydrothermally reacting at 80-120° C. for 1-3 hours to obtain a reaction product;

[0022] The reaction product is dialyzed to remove residual reagents to obtain a treatment liquid, the treatment liquid, 70-90% by mass hydrazine hydrate, and ammonia water are mixed in a volume ratio of 100:(0.1-0.3):(0.3-0.6)), and the mixture is reacted at 90-100°C for 1-3 hours. After adding 70-90% by mass hydrazine hydrate, which accounts for 0.1-0.3% of the volume of the treatment liquid, the reaction is continued for 1-3 hours. The product is dialyzed for purification and then freeze-dried to obtain rGO powder with a porous structure.

[0023] Preferably, the step S3 specifically includes the following steps:

[0024] The inverse opal composite membrane is immersed in a 0.1-0.2 g / mL (NH4)2PdCl4 aqueous solution and treated under vacuum conditions of -0.15 to -0.05 MPa for 20-40 minutes to uniformly adsorb [PdCl4]2- ions on the porous skeleton surface and remove unfixed palladium complexes to obtain an inverse opal composite membrane loaded with palladium-based active sites.

[0025] Preferably, in step S4, the reducing agent is dimethylamine borane,

[0026] In the nickel-containing plating solution containing a reducing agent, the molar ratio of nickel ions to dimethylamine borane is (2.5-4):1.

[0027] Preferably, in step S4, the nickel-containing plating solution containing a reducing agent comprises the following preparation steps: dissolving NiSO4·6H2O, trisodium citrate, and lactic acid in deionized water at a mass ratio of (3-5): (1-3): 1, adjusting the pH to 8-9 with ammonia water to obtain a mixed solution A, and mixing the mixed solution A with a dimethylamine borane solution to obtain a nickel-containing plating solution containing a reducing agent.

[0028] Preferably, in step S5, the silver-containing plating solution comprises: 4-6 g / L tetrasodium ethylenediaminetetraacetic acid, 7-8 g / L silver nitrate, and 9-11 g / L sodium citrate.

[0029] Preferably, in step S1, the pulling speed of the vertically pulled coating is 1-3 μm / s, and the immersion temperature is 20-30°C.

[0030] The beneficial effects of the present invention are as follows:

[0031] 1. This paper proposes a method for preparing PEA-PEDOT:PSS-rGO composite membranes based on multi-level ordered pore design and interface modification strategy, aiming to solve the difficult problem of synergistic optimization of mass transfer efficiency and electrochemical activity in flexible electrode materials, providing a high-performance solution for wearable devices and implantable medical sensors.

[0032] By combining molecular structure design with template engineering, polyethylene glycol diacrylate (PEGDA), a hydrophilic polymer substrate, was selected. The polar groups in its molecular chain formed multiple interactions with the conductive polymer PEDOT:PSS and reduced graphene oxide (rGO), constructing a stable three-dimensional network framework. A temperature-responsive template was combined with a photonic crystal template method to construct a vertically gradient, hierarchical, and ordered topological network structure, forming a hierarchical and continuous ion transport path. This significantly improved electrolyte wettability and material diffusion kinetics, while reducing interfacial mass transfer impedance.

[0033] 2. To address the issue of insufficient electrode reaction activity, Ni-Ag bimetallic nanoparticles were controllably loaded onto the inner pore walls through a synergistic process of electrochemical deposition and photochemical reduction. This resulted in a heterogeneous structure of Ni nanocrystals and Ag nanoparticles on the graphene surface of the PEA-PEDOT:PSS-rGO composite membrane. The catalytic activity of Ni and the high conductivity of Ag complement each other, while the spatial confinement of the nanoparticles within the pores inhibits aggregation and maintains the stability of the active sites. The synergistic effect of the multi-level pore topology and the metal-carbon interface in the composite membrane achieves a three-dimensional integration of the electron transport network and ion diffusion channels, effectively reducing the interfacial charge transfer impedance. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying any creative work, other drawings obtained based on these drawings still fall within the scope of the present invention.

[0035] Figure 1 This is a flow chart for the preparation of the PEA-PEDOT:PSS-rGO composite precursor in an embodiment of the present invention.

[0036] Figure 2 (a) (b) are scanning electron micrographs of two types of single-molecule SiO2 microspheres with different particle sizes in step S3-1 of Example 1 of the present invention.

[0037] Figure 3Schematic diagram of the structure of the PEA-PEDOT:PSS-rGO@Ni&Ag multi-level pore inverse opal metal composite membrane in Example 1 of the present invention.

[0038] Figure 4 (a) is the contact angle of pure PEA film in 3.0 mol / L KOH solution; (b) is the contact angle of PEA-PEDOT:PSS-rGO@Ni&Ag double-absorption composite film in Example 1 of the present invention in 3.0 mol / L KOH solution.

[0039] Figure 5 The electrochemical properties of the PEA-PEDOT:PSS-rGO@Ni&Ag double-absorption composite membrane in Example 1 of the present invention in 3.0 mol / L KOH: (a) is EIS, (b) is the change of volume area capacitance and volume capacitance at different voltage scan rates, (c) is GCD at different current densities, and (d) is CV at different voltage scan rates.

[0040] Figure 6 (ab) XPS test and (c) XRD test of the PEA-PEDOT:PSS-rGO@Ni&Ag double-absorption composite film in Example 1 of the present invention.

[0041] Figure 7 This is a cross-sectional SEM photograph of the PEA-PEDOT:PSS-rGO@Ni&Ag multi-level porous inverse opal metal composite film in Example 1 of the present invention. DETAILED DESCRIPTION

[0042] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be described in further detail below with reference to the accompanying drawings.

[0043] Example 1

[0044] This embodiment provides a method for preparing a PEA-PEDOT:PSS-rGO@Ni&Ag inverse opal metal composite film, and the specific steps are as follows:

[0045] Step S1: Prepare the main reagents:

[0046] S1-1. Preparation of PEA photosensitive prepolymer system: Ethoxylated trimethylolpropane triacrylate (ETPTA), polyethylene glycol diacrylate (PEGDA) and acrylic acid (AA) were measured in a volume ratio of 1:3:0.5, and 2-hydroxy-2-methyl-1-phenyl-1-propanone (photoinitiator 1173) accounting for 1% of the total monomer volume was added. The mixture was thoroughly mixed with a magnetic stirrer to form a homogeneous transparent solution. The mixed system was recorded as PEA.

[0047] S1-2. Preparation of Conductive Polymer Dispersion: PEDOT:PSS solids (base weight 0.02 g) were weighed at a mass ratio of 1:120, and 2.4 g of ultrapure water were gradually added to prepare a primary dispersion system. Subsequently, 100 μL of dimethyl sulfoxide (DMSO) was introduced as a secondary dopant to promote conformational transitions and phase separation of the conductive polymer chains. The entire system was mechanically stirred continuously at a constant temperature of 25°C for 24 hours, ultimately obtaining a uniform and stable dark blue conductive solution.

[0048] S1-3. Prepare porous reduced graphene oxide (rGO) by a step-by-step reduction method: First, 200 mL of a 2 g / L graphene oxide dispersion was mixed with 20 mL of 25% hydrogen peroxide and hydrothermally reacted at 100 ° C for 2 hours to achieve structural etching. After the reaction product was dialyzed for 48 hours to remove residual reagents, 100 mL of the treatment solution was mixed with 0.2 mL of 80% hydrated hydrazine and 0.45 mL of ammonia water, and reduced in two stages (2 hours each) in a 95 ° C oil bath, with 0.2 mL of hydrazine added in the middle to enhance the reduction effect. The final product was purified by secondary dialysis and freeze-dried to obtain a black rGO powder with a porous structure.

[0049] Step S2: constructing a PEA-PEDOT:PSS-rGO composite precursor:

[0050] S2-1. PEA and PEDOT:PSS were mixed at a mass ratio of 10:1 to obtain a PEA-PEDOT:PSS mixed solution.

[0051] S2-2. The rGO powder was dispersed with the PEA-PEDOT:PSS mixture at a mass fraction of 10% by high shear emulsification to obtain four groups of composite slurries with different compositions.

[0052] S2-3. Each slurry was evenly coated onto a pretreated glass substrate using a doctor blade coating process. The slurry was then transferred to a 35°C thermostat for 3 hours to evaporate the solvent. After initial film formation, the film was cured on both sides using a 365nm UV light source (15 seconds per side). The cured composite film was then immersed in anhydrous ethanol for post-treatment to obtain a composite electrode material with inverse opal structure characteristics.

[0053] Step S3, constructing a PEA-PEDOT:PSS-rGO inverse opal multi-level pore composite membrane:

[0054] S3-1. Preparation of multi-level structure SiO2 template:

[0055] (1) Synthesis of dual-size microspheres:

[0056] The seed growth method (particle size A = 200nm) and the improved Two types of monodisperse SiO2 microspheres (particle size difference >30%) were prepared by the HPLC method (particle size B = 800 nm), and their monodispersity (PDI < 0.05) was verified by dynamic light scattering (DLS).

[0057] (2) Gradient assembly process:

[0058] Primary template construction: SiO2 microspheres with particle size A were dispersed in anhydrous ethanol (mass fraction 8%) and deposited three times on a glass substrate using vertical pulling coating technology (pulling speed 2 μm / s, immersion temperature 25°C) to form a densely packed microsphere array.

[0059] Secondary template superposition: Replace with SiO2 microsphere dispersion of particle size B (mass fraction 8%), maintain the same pulling parameters for secondary deposition, and form a dual-scale ordered opal template through layer-by-layer self-assembly of heterogeneous microspheres.

[0060] Among them, the seed growth method is suitable for preparing SiO2 microspheres with a particle size of less than 360nm. This embodiment takes SiO2 microspheres with a particle size of 200nm as an example to introduce the preparation method. The specific preparation steps are as follows:

[0061] (a) Seed solution preparation: Use a graduated cylinder to measure 33 mL of deionized water and 3.3 mL of aqueous ammonia in a beaker. Seal the mixture with parafilm and ultrasonically disperse the mixture in an ultrasonic multi-frequency cleaner for 2 minutes. Add the mixture to a 500 mL single-necked round-bottom flask. Add 160 mL of anhydrous ethanol to the flask. Heat the flask in a 60°C oil bath with mechanical stirring. Use a pipette to remove 4.4 mL of tetraethyl orthosilicate (TEOS) and place it in the beaker. Use a 5 mL disposable sterile syringe to draw up the TEOS and place it on a constant-rate syringe pump at 0.44 mL / min. Add the solution dropwise for 10 minutes. After the solution is complete, allow the mixture to react for 10 hours to obtain a light blue, transparent seed solution.

[0062] (b) Preparation of SiO2 microsphere solution: 160 mL of ethanol, 40 mL of ammonia, and 40 mL of deionized water were added to a 500 mL three-necked flask. The mixture was stirred magnetically at room temperature at 300 rpm. 3.3-0.8 mL of the seed solution was pipetted into the flask. Pre-measured solution A (20 mL of tetraethyl orthosilicate) and solution B (10 mL of ethanol, 8 mL of ammonia, and 3 mL of deionized water) were added dropwise using a 20 mL disposable syringe at a rate of 0.2 mL / min for 100 min. The mixture was allowed to react for 5 h after completion of the addition.

[0063] (c) Cleaning: Remove the reaction solution from a centrifuge tube and centrifuge at 6000 rpm for 30 min. Remove the supernatant. Add anhydrous ethanol and ultrasonically disperse the solution. Centrifuge again and remove the supernatant. Repeat this process three times. Transfer the resulting SiO2 microspheres to a sample bottle and dry them for later use. To prepare an 8% ethanol dispersion, grind the microspheres into a powder in a mortar and pestle, transfer the powder to a conical flask, and ultrasonically disperse the microspheres in anhydrous ethanol.

[0064] Improved The method is suitable for preparing SiO2 microspheres with a particle size greater than 360nm. This embodiment takes SiO2 microspheres with a particle size of 800nm ​​as an example to introduce the preparation method. The specific preparation steps are as follows:

[0065] (a) Preparation of SiO2 microsphere solution: 100 mL of anhydrous ethanol was added to a 500 mL single-necked flask. 28-40 mL of concentrated aqueous ammonia was diluted to 50 mL with deionized water and added to the flask. The mixture was stirred magnetically at room temperature at 1500 r / min. 20 mL of tetraethyl orthosilicate and 80 mL of anhydrous ethanol were quickly added at this speed. After 2 minutes, the speed was increased to 600 r / min, and the reaction was continued for 3 h.

[0066] (b) Cleaning: Remove the reaction solution from a centrifuge tube and centrifuge at 6000 rpm for 30 min. Remove the supernatant. Add anhydrous ethanol and ultrasonically disperse the solution. Centrifuge again and remove the supernatant. Repeat this process three times. Transfer the resulting SiO2 microspheres to a sample bottle and dry them for later use. To prepare an 8% ethanol dispersion, grind the microspheres into a powder in a mortar and pestle, transfer the powder to a conical flask, and ultrasonically disperse the microspheres in anhydrous ethanol.

[0067] S3-2. Construction of multi-level pore composite membrane

[0068] (1) Precursor solution filling: The PEA-PEDOT:PSS-rGO composite solution is injected into the template pores, and vacuum-assisted infiltration is used to ensure that the multi-level channels are fully filled.

[0069] (2) Photocrosslinking and curing: A 365 nm ultraviolet light source is used to irradiate the composite system on both sides (15 s per side) to trigger a free radical polymerization reaction to form a stable three-dimensional network.

[0070] S3-3. Template Etching and Pore Release

[0071] The cured film was immersed in a 5 wt.% hydrofluoric acid (HF) solution, and the etching progress was dynamically monitored until the template was completely removed (SEM-EDS confirmed the disappearance of the Si element signal). The resulting PEA-PEDOT:PSS-rGO inverse opal structure retained dual-scale periodic pores, forming a hierarchical interpenetrating network of large pores (originating from particle size A) and small pores (originating from particle size B).

[0072] Step S4: constructing PEA-PEDOT:PSS-rGO@Ni&Ag inverse opal metal composite film

[0073] S4-1. Precursor activation and palladium-based catalytic site anchoring:

[0074] The PEA-PEDOT:PSS-rGO inverse opal hierarchical composite membrane prepared in step S3 was immersed in a 0.142 g / mL (NH4)2PdCl4 aqueous solution and treated under -0.1 MPa vacuum for 30 minutes to make [PdCl4] 2- The ions are uniformly adsorbed on the surface of the porous skeleton. After removal, ultrasonic rinsing with deionized water (3 times, 5 minutes each time) is performed to remove the unfixed palladium complex and obtain the loaded Pd 2+ Porous supports for active sites.

[0075] S4-2, Chemical Nickel Plating Process:

[0076] NiSO4·6H2O (64 g / L), trisodium citrate (32 g / L), and lactic acid (16 g / L) were dissolved in deionized water, and the pH was adjusted to 8.5 with ammonia water to obtain a mixed solution A. Dimethylamine borane (DMAB, 22.5 g / L) was used as a reducing agent solution, and the mixed solution A (200 mL) was mixed with DMAB solution (6.7 mL) at a volume ratio of 30:1 to control Ni 2+ The molar ratio of DMAB is 3.2:1.

[0077] The loaded Pd prepared in step S4-1 2+ The porous support with active sites was immersed in the plating solution and allowed to stand at room temperature for 180 minutes. The in-situ growth of Ni nanoparticles was achieved through an autocatalytic reduction reaction to obtain a Ni-loaded composite membrane.

[0078] S4-3. Gradient Deposition of Silver Nanostructures

[0079] Tetrasodium ethylenediaminetetraacetic acid (Na4EDTA, 5g / L) and silver nitrate (AgNO3, 7.5g / L) were mixed in a volume ratio of 1:1, and sodium citrate (10g / L) was added as a reducing agent to obtain a silver plating solution. The Ni-loaded composite film obtained in step S4-2 was immersed in the silver plating solution and placed in a constant temperature environment of 60°C to slowly evaporate the solvent (about 2 hours). The capillary force was used to drive the Ag to form a silver plating solution. + The Ag-Ni bimetallic heterostructure was formed after the deposition was completed. After the deposition was completed, the residual plating solution was removed by nitrogen purge and the samples were dried in vacuum at 60°C for 12 hours.

[0080] like Figure 2As shown, the particle sizes of SiO2 microspheres prepared by the two methods are very consistent, and the highly uniform particle size distribution is beneficial to the construction of the subsequent pore-forming template.

[0081] like Figure 3 As shown, the prepared PEA-PEDOT:PSS-rGO@Ni&Ag double-absorption composite membrane structure has a dual-scale pore structure.

[0082] like Figure 4 As shown in the figure, contact angle tests of wettability in 3 mol / L KOH electrolyte were conducted. Compared with the contact angle of pure PEA membrane, the contact angle of the PEA-PEDOT:PSS-rGO@Ni&Ag double-absorption composite membrane was further reduced to 15.5°, demonstrating excellent hydrophilicity and electrolyte wettability. The multi-scale, multi-porous electrode membrane structure can significantly improve the permeability and diffusion of the electrolyte, thereby enhancing electrolyte wettability and electrode material utilization.

[0083] like Figure 5 As shown in (a), the Nyquist curve fitting of the PEA-PEDOT:PSS-rGO@Ni&Ag double-absorption composite film shows that its equivalent series resistance (Rrs=0.52Ω) and charge transfer resistance (Rct=0.447Ω) are both low, indicating excellent charge transfer ability.

[0084] like Figure 5 As shown in (b), the volume capacitance of the PEA-PEDOT:PSS-rGO@Ni&Ag double-absorption composite film changes at a scan rate of 5 to 50 mV s-1. At a scan rate of 5 mV s-1, the volume capacitance can reach about 3615 Fcm-3. When the scan rate increases to 10 mV s-1, the volume capacitance retention rate is as high as 88.6%.

[0085] like Figure 5 As shown in (c), the constant current charge and discharge (GCD) curves at current densities of 1Ag-1, 2Ag-1, and 5Ag-1 show that its charge and discharge platform is basically consistent with the redox peak range of the CV curve, and the electrode material has good reversibility, conductivity, and consistent electrochemical properties.

[0086] like Figure 5 As shown in (d), the CV curve has a small deformation at different scan rates, indicating that the electrochemical polarization resistance is low and the electrode film has good electrochemical stability.

[0087] like Figure 6 As shown, the peaks in the XPS test correspond to the characteristic peaks of Ni and Ag, and the peaks in the XRD test correspond to the characteristic peaks of Ni and Ag, proving that metal Ni and Ag are successfully deposited into the electrode film.

[0088] like Figure 7As shown, SEM shows that a dual-scale pore structure is constructed in the precursor PEA-PEDOT:PSS-rGO, and EDS shows that metal nanoparticles Ni and Ag are smoothly and evenly deposited in the PEA-PEDOT:PSS-rGO dual-scale pore membrane.

[0089] The above disclosure is merely a preferred embodiment of the present invention and certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A flexible electrode with a vertical gradient hierarchical ordered topological network structure, characterized by: The invention comprises an inverse opal composite membrane with multi-level pores, palladium-based active sites adsorbed in the multi-level pores, and an Ag-Ni bimetallic heterostructure in situ grown on the palladium-based active sites in the multi-level pores. The multi-level pore channel includes at least two groups of interpenetrating single-level pore layers, and the single-level pore layers are composed of regularly arranged spherical air holes with the same diameter. The diameters of the spherical air holes in different single-level pore layers vary in a gradient.

2. The flexible electrode having a vertical gradient hierarchical ordered topological network structure according to claim 1, characterized in that: The gradient variation range of the diameters of the spherical air pores in the different single-level pore layers is from 2.5 μm to 50 nm.

3. The method for preparing a flexible electrode having a vertical gradient hierarchical ordered topological network structure according to claim 1 or 2, characterized in that: The steps include: S1. Using a vertical pulling coating method, SiO2 microsphere dispersions of different particle sizes are deposited layer by layer on a substrate according to a particle size gradient to form a multi-level opal template; S2, filling the composite membrane slurry into the multi-level opal template for solidification, and removing the template to obtain an inverse opal composite membrane with multi-level pores; S3, activating the inverse opal composite membrane using a palladium complex to obtain an inverse opal composite membrane loaded with palladium-based active sites; S4, immersing the inverse opal composite film loaded with palladium-based active sites in a nickel-containing plating solution containing a reducing agent, and causing Ni nanoparticles to in situ grow on the inverse opal composite film loaded with palladium-based active sites through an autocatalytic reduction reaction, thereby obtaining a Ni-loaded inverse opal composite film; S5, immersing the Ni-loaded inverse opal composite film into a silver-containing plating solution, and using capillary force to drive the Ag + It migrates directionally to the inner wall of the pores of the inverse opal composite membrane to obtain an inverse opal composite membrane loaded with Ag-Ni bimetallic heterostructure.

4. The method for preparing a flexible electrode having a vertical gradient hierarchical ordered topological network structure according to claim 3, characterized in that: In step S2, the method for preparing the composite membrane slurry comprises the following steps: (A) Ethoxylated trimethylolpropane triacrylate monomer, polyethylene glycol diacrylate monomer, and acrylic acid monomer were weighed in a volume ratio of 1:(2.5-3.5):(0.2-0.8), and 0.8%-1.2% of 2-hydroxy-2-methyl-1-phenyl-1-propanone based on the total monomer volume was added and thoroughly mixed until a homogeneous transparent solution was formed, which was recorded as PEA; (B) PEDOT and PSS were weighed in a mass ratio of 1:(100-140), ultrapure water and dimethyl sulfoxide were added sequentially, and the mixture was stirred to obtain a PEDOT:PSS solution. (C) PEA, PEDOT:PSS, and rGO powders were mixed in a mass ratio of (8-12):1:(0.5-1.5) and then sheared and emulsified to obtain a PEA-PEDOT:PSS-rGO composite membrane slurry.

5. The method for preparing a flexible electrode having a vertical gradient hierarchical ordered topological network structure according to claim 4, characterized in that: In step (C), the method for preparing the rGO powder comprises the following steps: Mixing a graphene oxide dispersion having a concentration of 1-3 g / L with a hydrogen peroxide solution having a concentration of 20-30% in a volume ratio of (8-12):1, and hydrothermally reacting at 80-120° C. for 1-3 hours to obtain a reaction product; The reaction product is dialyzed to remove residual reagents to obtain a treatment liquid, the treatment liquid, 70-90% by mass hydrazine hydrate, and ammonia water are mixed in a volume ratio of 100:(0.1-0.3):(0.3-0.6)), and the mixture is reacted at 90-100°C for 1-3 hours. After adding 70-90% by mass hydrazine hydrate, which accounts for 0.1-0.3% of the volume of the treatment liquid, the reaction is continued for 1-3 hours. The product is dialyzed for purification and then freeze-dried to obtain rGO powder with a porous structure.

6. The method for preparing a flexible electrode having a vertical gradient hierarchical ordered topological network structure according to claim 3, characterized in that: The step S3 specifically includes the following steps: The inverse opal composite membrane is immersed in a 0.1-0.2 g / mL (NH4)2PdCl4 aqueous solution and treated under vacuum conditions of -0.15 to -0.05 MPa for 20-40 minutes to uniformly adsorb [PdCl4]2- ions on the porous skeleton surface and remove unfixed palladium complexes to obtain an inverse opal composite membrane loaded with palladium-based active sites.

7. The method for preparing a flexible electrode having a vertical gradient hierarchical ordered topological network structure according to claim 3, characterized in that: In step S4, the reducing agent is dimethylamine borane, In the nickel-containing plating solution containing a reducing agent, the molar ratio of nickel ions to dimethylamine borane is (2.5-4):

1.

8. The method for preparing a flexible electrode having a vertical gradient hierarchical ordered topological network structure according to claim 7, characterized in that: In step S4, the nickel-containing plating solution containing a reducing agent comprises the following preparation steps: dissolving NiSO4·6H2O, trisodium citrate, and lactic acid in deionized water at a mass ratio of (3-5):(1-3):1, adjusting the pH to 8-9 with ammonia water to obtain a mixed solution A, and mixing the mixed solution A with a dimethylamine borane solution to obtain a nickel-containing plating solution containing a reducing agent.

9. The method for preparing a flexible electrode having a vertical gradient hierarchical ordered topological network structure according to claim 3, characterized in that: In step S5, the silver plating solution includes: 4-6 g / L tetrasodium ethylenediaminetetraacetic acid, 7-8 g / L silver nitrate, and 9-11 g / L sodium citrate.

10. The method for preparing a flexible electrode having a vertical gradient hierarchical ordered topological network structure according to claim 3, characterized in that: In the step S1, the pulling speed of the vertically pulled coating is 1-3 μm / s, and the immersion temperature is 20-30°C.

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