Metal-loaded super-hydrophobic air electrode for chlorine production reaction and preparation method of metal-loaded super-hydrophobic air electrode

Abstract

The invention relates to the technical field of air electrodes, in particular to a metal-loaded super-hydrophobic air electrode for chlorine production reaction and a preparation method thereof.The metal-loaded super-hydrophobic air electrode for chlorine production reaction comprises a porous composite matrix composed of a three-dimensional porous ceramic framework and an MXene nanosheet conductive network attached to pore channels and the surface of the three-dimensional porous ceramic framework; the gradient functionalized super-hydrophobic layer covers the surface of the porous composite matrix and is formed by compounding polytetrafluoroethylene and a fluorine-containing polymer formed by in-situ polymerization of a fluorine-containing acrylate monomer; the metal catalyst layer is directly loaded on the surface of the gradient functionalized super-hydrophobic layer. According to the application, an MXene two-dimensional conductive network is constructed in situ on a ceramic skeleton, a composite functional layer with gradient change of components and wettability is constructed, strong metal-carrier interaction is formed by using MXene and noble metal, and performance improvement is realized from multiple aspects of charge transfer, three-phase interface mass transfer, catalytic activity and selectivity, structural corrosion resistance and durability and the like.

Description

Technical Field

[0001] This invention relates to the field of air electrode technology, specifically to a metal-supported superhydrophobic air electrode for chlorine production reactions and its preparation method. Background Technology

[0002] Electrochemical chlorine generation technology has important applications in disinfection, wastewater treatment, and chemical synthesis. The gas diffusion electrode (also known as the air electrode) is a core component, and its performance directly determines the system's efficiency, energy consumption, and lifespan.

[0003] An ideal air electrode for chlorine production should have the following characteristics: (1) high conductivity to reduce ohmic polarization; (2) suitable hydrophobicity to build a stable gas-liquid-solid three-phase reaction interface and promote chlorine evolution; (3) high catalytic activity and stability; and (4) a strong mechanical structure and interface bond to resist scouring and corrosion during long-term electrolysis.

[0004] Currently, common air electrodes are mostly made of porous conductive materials such as carbon paper and nickel foam as the substrate, and are formed by coating or sintering binders and catalytic materials such as polytetrafluoroethylene (PTFE). These electrodes have the following inherent defects: First, carbon materials are prone to corrosion under strong oxidizing chlorine-producing potentials, leading to electrode structural collapse and performance degradation; second, the adhesion between PTFE and the conductive substrate is mainly physical, with weak interfacial bonding, making it prone to hydrophobic layer peeling under long-term operation or high gas flux, causing the electrode to be "drowned" by the electrolyte and deactivated. Furthermore, traditional preparation methods have limited control over the electrode's microstructure, making it difficult to precisely construct a strong and stable superhydrophobic interface while ensuring high conductivity. Summary of the Invention

[0005] This application provides a metal-supported superhydrophobic air electrode for chlorination reactions and its preparation method, in order to solve the problems of easy corrosion of carbon matrix, weak interfacial bonding, difficult structure control, and easy performance degradation and deactivation in the prior art.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention provides a metal-supported superhydrophobic air electrode for chlorination reactions, the air electrode comprising:

[0007] A porous composite matrix, wherein the porous composite matrix is ​​composed of a three-dimensional porous ceramic framework and an MXene nanosheet conductive network attached to its pores and surface;

[0008] A gradient-functionalized superhydrophobic layer is applied to the surface of the porous composite substrate. This layer is composed of polytetrafluoroethylene (PTFE) and a fluoropolymer formed by in-situ polymerization of fluoroacrylate monomers. The chemical composition and surface energy of this layer exhibit a gradient from the substrate side to the outer surface side, thus endowing the electrode with superhydrophobicity.

[0009] A metal catalyst layer directly loaded on the surface of the gradient functionalized superhydrophobic layer.

[0010] Preferably, the porous composite matrix is ​​prepared by a method comprising the following steps:

[0011] Using organic foam as a sacrificial template, a sol containing ceramic precursors and sintering aids is impregnated, and then dried and sintered at high temperature to form a porous ceramic skeleton with a three-dimensional interconnected network structure.

[0012] Using MAX phase powder as raw material, selective etching is performed using lithium fluoride hydrochloric acid solution or hydrofluoric acid solution to remove aluminum atom layer; after the etched product is washed to neutral, intercalation treatment is performed using organic amine intercalation agent, followed by liquid phase ultrasonic exfoliation under protective atmosphere, and the unexfoliated thick sheets are removed by centrifugation to obtain a stable dispersion of single-layer or few-layer MXene nanosheets.

[0013] The porous ceramic framework is placed in a sealed container and evacuated. Then, the MXene dispersion is injected, and the dispersion is used to completely wet the pores of the framework by driving the negative pressure. After being removed, it is dried so that the MXene nanosheets are attached to the surface of the ceramic framework. Heat treatment is carried out under an inert atmosphere at a temperature of 200°C to 500°C to obtain the porous composite matrix.

[0014] Preferably, the MAX phase powder is at least one of Ti3AlC2, Ti2AlC or Nb2AlC; the ceramic precursor is at least one of zirconium oxide, titanium oxide or aluminum oxide; and the organic amine intercalating agent is selected from dimethyl sulfoxide, tetrabutylammonium hydroxide or tetramethylammonium hydroxide.

[0015] Preferably, the metal catalyst layer comprises at least one noble metal selected from platinum, palladium, iridium, ruthenium, and gold, or an alloy of the noble metal with at least one transition metal selected from iron, cobalt, nickel, and copper.

[0016] Preferably, the gradient functionalized superhydrophobic layer is formed by the following method: impregnating the porous composite matrix in a composite functional slurry; triggering the in-situ polymerization reaction of the monomer to form a fluoropolymer network; and then performing heat treatment at 300°C to 380°C to melt the polytetrafluoroethylene and fuse it with the polymer network to obtain the gradient functionalized superhydrophobic layer.

[0017] Preferably, the composite functional slurry comprises a polytetrafluoroethylene dispersion, a polymerizable fluorinated acrylate monomer, and an initiator, wherein the polymerizable fluorinated acrylate monomer is dodecafluoroheptyl methacrylate; and the polymerization initiator is an ultraviolet photoinitiator or a thermal initiator.

[0018] This invention also provides a method for preparing a metal-supported superhydrophobic air electrode for chlorination reactions, comprising the following steps:

[0019] An MXene composite porous matrix was prepared, and then cleaned and dried to obtain a pretreated substrate.

[0020] The pretreated matrix is ​​immersed in the composite functional slurry, taken out and drained, and an in-situ polymerization reaction is triggered under the action of an initiator. Then, it is heat-treated at a temperature of 300℃ to 380℃ to form a gradient functionalized superhydrophobic layer.

[0021] Surface activation treatment is performed on the substrate coated with a superhydrophobic layer;

[0022] Using the activated substrate as the working electrode, an electrochemical deposition is performed in an electrolyte containing target metal ions to form a metal catalyst layer. A perfluorosulfonic acid resin solution is then coated on the surface of the metal catalyst layer and dried again to obtain the metal-supported superhydrophobic air electrode.

[0023] Preferably, the surface activation treatment is a corona treatment, and the treatment conditions include: voltage 10-48kV, electrode spacing 5-10mm, and treatment time 30-150 seconds.

[0024] Preferably, the electrochemical deposition is performed using a constant potential deposition method, with the deposition potential relative to the Ag / AgCl reference electrode being -0.5V to +0.5V. The deposition is carried out under nitrogen protection and the deposition time is 10-30 minutes.

[0025] Preferably, the metal precursor in the electrolyte is selected from at least one of chloroplatinic acid, chloropalladium acid, palladium chloride, iridium chloride, ruthenium trichloride, silver nitrate, copper sulfate, cobalt chloride, nickel nitrate, and ferric chloride; the electrolyte is an aqueous solution of an inorganic acid or an organic acid, wherein the inorganic acid is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, and the organic acid is selected from at least one of formic acid, acetic acid, and oxalic acid.

[0026] The beneficial effects achieved by using the present invention described above are as follows:

[0027] 1. This invention prepares a metal-supported superhydrophobic air electrode for chlorination reactions. By constructing a continuous MXene nanosheet conductive network in situ inside a porous insulating / semiconductor ceramic framework, the abundant functional groups on its surface can form strong interactions with the ceramic framework and its own layers. The constructed conductive network is not only physically contacted, but also a continuous two-dimensional electron channel with good hydrophilicity and excellent electron delocalization. This allows electrons to be rapidly delocalized within the two-dimensional plane of MXene and between the layers, directly reaching the active center of the metal catalyst supported on the surface. This greatly reduces the ohmic polarization of the electrode, enabling a higher chlorination current density to be obtained at the same overpotential, or a significant reduction in energy consumption at the same current density. This solves the problem that the intrinsic conductivity of existing carbon-based electrodes is limited, and the conductive network is easily destroyed in corrosive electrolytes, resulting in high charge transport resistance, which has become a bottleneck for performance improvement at high current densities.

[0028] 2. This application forms a composite functional layer on the substrate surface with a continuous gradient in chemical composition and wettability. From the substrate to the electrolyte side, a smooth transition is achieved from a strongly anchored polymer network to a superhydrophobic surface layer enriched with PTFE. This gradient interface not only provides an interfacial bonding strength far exceeding that of traditional physical attachment through chemical bonding and physical interlocking, effectively preventing electrode deactivation caused by hydrophobic layer peeling, but also provides a preferential diffusion path for chloride ions through the hydrophilic microchannels inside, forming a local reactant enrichment area. At the same time, the superhydrophobic properties of the outer layer promote the rapid desorption of chlorine products, greatly optimizing the mass transfer kinetics of the gas-liquid-solid three-phase reaction interface, thereby significantly reducing electrochemical polarization and improving reaction efficiency and long-term operational stability.

[0029] 3. This invention uses MXene nanosheets as a catalyst support, utilizing their abundant surface defects and tunable work function to form a strong metal-support interaction with the supported noble metal nanoparticles. This modulates the electronic structure of the catalyst and shifts the d-band center, optimizing the adsorption strength for chlorine-containing intermediates, reducing the rate-determining energy barrier of the chlorine evolution reaction, and suppressing the occurrence of oxygen evolution side reactions. This solves the problems of weak electronic interaction between the catalyst and the support, limited ability to regulate reaction intermediates, and low chlorine production selectivity and intrinsic catalytic activity in existing technologies, significantly improving the chlorine evolution catalytic activity and reaction selectivity of the electrode.

[0030] 4. This invention uses highly chemically stable ceramics as the structural framework and inert MXene, fluoropolymers and PTFE as functional materials to construct a fully inert integrated anti-corrosion architecture. Each component has excellent stability in strong oxidizing and acidic chlorine-containing environments. Moreover, through the close combination of chemical and physical interactions, it synergistically resists the damage caused by multiple stresses such as electric fields, ion penetration and gas erosion. This fundamentally solves the problems of easy corrosion and structural collapse of traditional carbon-based electrode materials, endowing the electrode with excellent mechanical durability and environmental tolerance, and greatly extending its service life.

[0031] 5. The preparation method of the present invention has clear process steps and controllable parameters. By adjusting the concentration of MXene dispersion, vacuum impregnation conditions, polymerization and heat treatment parameters, the density, porosity of conductive network and the structure and thickness of gradient hydrophobic layer can be precisely controlled, thereby realizing the directional design and optimization of key performance indicators such as electrode conductivity, hydrophobicity and catalytic active site distribution, meeting the specific requirements of different application scenarios for electrode performance, and having good repeatability and scalability.

[0032] This solves the problems in existing technologies, such as easy corrosion of carbon matrix, weak interfacial bonding, difficulty in structural control, and easy performance degradation and deactivation.

[0033] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0034] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0035] Figure 1 This is a SEM image of a metal-loaded superhydrophobic air electrode provided in an embodiment of the present invention. Detailed Implementation

[0036] The technical solution of the present invention is illustrated below through specific examples. It should be understood that the one or more method steps mentioned in the present invention do not preclude the existence of other method steps before or after the combined steps, or the insertion of other method steps between these explicitly mentioned steps; it should also be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless otherwise stated, the numbering of each method step is merely a convenient tool for identifying each method step, and not for limiting the order of the method steps or defining the scope of the present invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the present invention.

[0037] To better understand the above technical solutions, exemplary embodiments of the present invention are described in more detail below. While exemplary embodiments of the present invention are shown, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0038] The following description, with reference to the accompanying drawings, describes an embodiment of a metal-supported superhydrophobic air electrode for chlorine production reactions and its preparation method. To address the issue of weak interfacial bonding mentioned in the background, this application proposes a metal-supported superhydrophobic air electrode for chlorination reactions. Addressing the core technical problems of existing chlorination air electrodes, such as easy corrosion of the carbon matrix, weak interfacial bonding, difficulty in precise control of microstructure, and easy performance degradation and deactivation, this application innovates and optimizes from all dimensions: material selection, structural design, interface construction, and preparation process. The electrode uses a porous insulating / semiconductor ceramic as a highly stable structural framework, within which a continuous MXene nanosheet conductive network is constructed in situ. Relying on the strong interactions between the abundant functional groups on the MXene surface and the ceramic framework and its own layers, a two-dimensional electron channel with both good hydrophilicity and excellent electron delocalization is formed, enabling rapid electron transport to the active center of the metal catalyst, significantly reducing ohmic polarization, and solving the problems of limited intrinsic conductivity and easy corrosion damage of the conductive network in traditional carbon-based electrodes. On the substrate surface, a composite functional layer with a continuous gradient of chemical composition and wettability is constructed through chemical bonding and physical interlocking, achieving a smooth transition from a strongly anchored polymer network to a PTFE-rich superhydrophobic surface layer, which not only improves the interfacial bonding strength but also... This method effectively prevents hydrophobic layer stripping and achieves chloride ion enrichment and rapid mass transfer through internal hydrophilic microchannels. The superhydrophobic outer layer promotes rapid desorption of chlorine products, optimizing the mass transfer kinetics at the gas-liquid-solid three-phase reaction interface, reducing electrochemical polarization, and improving reaction efficiency and interface stability. Using MXene nanosheets as a noble metal catalyst support, the abundant defects and tunable work function on their surface form a strong metal-support interaction, modulating the catalyst's electronic structure and shifting it to the d-band center. This optimizes the adsorption strength for chlorine-containing intermediates, lowers the rate-determining energy barrier of the chlorine evolution reaction, and simultaneously inhibits… The oxygen evolution reaction side reaction significantly enhances the intrinsic catalytic activity and reaction selectivity of the electrode for chlorine evolution. A fully inert, integrated, corrosion-resistant architecture is constructed using inert materials such as ceramics, MXene, fluoropolymers, and PTFE. Each component exhibits excellent chemical stability in harsh chlorine-producing environments with strong oxidation and acidic chlorine content. Furthermore, through a close combination of chemical and physical interactions, it synergistically resists multiple stresses such as electric fields, ion penetration, and gas erosion, fundamentally avoiding problems like carbon corrosion and structural collapse. This endows the electrode with excellent mechanical durability and environmental tolerance, significantly extending its service life. Simultaneously, the electrode's preparation method has clear process steps and controllable parameters. By adjusting the MXene dispersion concentration, vacuum impregnation conditions, polymerization and heat treatment parameters, the conductive network density, porosity, and the structure and thickness of the gradient hydrophobic layer can be precisely controlled. This allows for targeted design and optimization of key performance indicators such as electrode conductivity, hydrophobicity, and catalytic active site distribution, meeting the specific performance requirements of different applications such as disinfection, wastewater treatment, and chemical synthesis. The preparation process also boasts good repeatability and scalability.This invention optimizes the entire chain of the chlorine-producing electrocatalytic reaction, including charge transport, three-phase interface mass transfer, catalytic activity and selectivity, and structural corrosion resistance and durability. It comprehensively improves the overall performance of the electrode, fundamentally solves many defects of the existing technology, and provides a new type of air electrode that is suitable for high efficiency, high stability and complex working conditions in the field of chlorine production, and has good practical application value.

[0039] The present invention will be further described in conjunction with the following embodiments.

[0040] Example 1

[0041] This invention provides a metal-supported superhydrophobic air electrode for chlorination reactions. The air electrode comprises: a porous composite substrate, wherein the porous composite substrate is composed of a three-dimensional porous ceramic framework and an MXene nanosheet conductive network attached to its pores and surface; a gradient-functionalized superhydrophobic layer covering the surface of the porous composite substrate, wherein the gradient-functionalized superhydrophobic layer is composed of polytetrafluoroethylene and a fluoropolymer formed by in-situ polymerization of fluorinated acrylate monomers, and its chemical composition and surface energy change in a gradient from the substrate side to the outer surface side, giving the electrode superhydrophobicity; and a metal catalyst layer directly supported on the surface of the gradient-functionalized superhydrophobic layer.

[0042] The porous composite matrix is ​​prepared by a method including the following steps: using organic foam as a sacrificial template, impregnating a sol containing ceramic precursors and sintering aids, and then drying and sintering at high temperature to form a porous ceramic skeleton with a three-dimensional interconnected network structure.

[0043] Using MAX phase powder as raw material, selective etching was performed using a lithium fluoride-containing hydrochloric acid solution to remove the aluminum atom layer. After washing the etched product to neutrality, intercalation treatment was performed using an organic amine intercalating agent. Subsequently, liquid-phase ultrasonic exfoliation was performed under a protective atmosphere, and the unexfoliated thick sheets were removed by centrifugation to obtain a stable dispersion of monolayer or few-layer MXene nanosheets. A porous ceramic framework was placed in a sealed container and evacuated, and then the MXene dispersion was injected. The dispersion was driven by negative pressure to completely wet the pores of the framework. After removal, the MXene nanosheets were dried to adhere to the surface of the ceramic framework. Heat treatment was performed under an inert atmosphere at a temperature of 200℃ to obtain a porous composite matrix.

[0044] Among them, the MAX phase powder is Ti3AlC2; the ceramic precursor is zirconium oxide; and the organic amine intercalating agent is selected from dimethyl sulfoxide.

[0045] It should be noted that if the ceramic precursor is zirconium oxide, then the sintering aid is yttrium oxide, and the amount of yttrium oxide added is usually 3-8 mol% of the molar fraction of zirconium oxide, preferably 4-6 mol%.

[0046] The metal catalyst layer contains at least one noble metal selected from platinum, palladium, iridium, ruthenium, and gold.

[0047] The gradient functionalized superhydrophobic layer is formed by the following method: impregnating a porous composite matrix in a composite functional slurry; triggering an in-situ polymerization reaction of monomers to form a fluoropolymer network; and then performing heat treatment at 300°C to melt polytetrafluoroethylene and fuse it with the polymer network to obtain the gradient functionalized superhydrophobic layer.

[0048] The composite functional slurry contains a polytetrafluoroethylene dispersion, a polymerizable fluorinated acrylate monomer, and an initiator. The polymerizable fluorinated acrylate monomer is dodecafluoroheptyl methacrylate, and the polymerization initiator is an ultraviolet initiator.

[0049] This invention also provides a method for preparing a metal-supported superhydrophobic air electrode for chlorination reactions, comprising the following steps:

[0050] An MXene composite porous matrix was prepared, and then cleaned and dried to obtain a pretreated substrate.

[0051] The pretreated matrix is ​​immersed in the composite functional slurry, taken out and drained, and an in-situ polymerization reaction is triggered under the action of an initiator. Then, it is heat-treated at 300°C to form a gradient functionalized superhydrophobic layer.

[0052] Surface activation treatment is performed on the substrate coated with a superhydrophobic layer;

[0053] Using the activated substrate as the working electrode, an electrochemical deposition is performed in an electrolyte containing target metal ions to form a metal catalyst layer. A perfluorosulfonic acid resin solution is then coated on the surface of the metal catalyst layer and dried again to obtain a metal-supported superhydrophobic air electrode.

[0054] The surface activation treatment is a corona treatment, and the treatment conditions include: voltage 10kV, electrode spacing 5mm, and treatment time 30 seconds.

[0055] Electrochemical deposition employs a constant potential deposition method, with the deposition potential ranging from -0.5V to +0.5V relative to the Ag / AgCl reference electrode. Deposition is carried out under nitrogen protection for 10 minutes.

[0056] The metal precursor in the electrolyte is selected from chloroplatinic acid, chloropalladium acid, and palladium chloride; the electrolyte is an aqueous solution of inorganic acid, wherein the inorganic acid is selected from hydrochloric acid, sulfuric acid, and nitric acid.

[0057] Specifically, the porous composite matrix is ​​prepared by a method including the following steps, and the proportions of each material and operational details are as follows:

[0058] Preparation of porous ceramic framework: Polyurethane foam with a pore size of 40 PPI was used as a sacrificial template and completely impregnated in a ceramic precursor sol (sol solid content of 25 wt%). The ceramic precursor was zirconia, and the sintering aid was yttrium oxide, with the amount of yttrium oxide added being 5 mol% of the molar fraction of zirconia. Both were uniformly dispersed in the sol, and the dispersion medium was a mixture of deionized water and ethanol (volume ratio 1:1). After impregnation, the sol was removed by a pulling method (pulling speed 2-3 cm / min), dried at 80℃ for 24 h, and then placed in a muffle furnace. The temperature was increased to 1450℃ at a heating rate of 5℃ / min and held for 3 h to complete sintering. The polyurethane template was then removed, forming a porous ceramic framework with a three-dimensional interconnected network structure. The framework porosity was 75%, and the average pore size was 150 μm.

[0059] Preparation of MXene nanosheet dispersion: 1.0 g of Ti3AlC2MAX phase powder was added to 20 mL of 9 mol / L hydrochloric acid solution containing 0.8 g of lithium fluoride. The mixture was etched at 35 °C with constant stirring for 24 h. The etched product was repeatedly washed with deionized water by centrifugation until the pH of the supernatant reached 6.8. Then, 30 mL of dimethyl sulfoxide (DMSO) was added, and the mixture was allowed to stand at room temperature for 12 h for intercalation. The intercalated product was transferred to an argon atmosphere, and deionized water was added to prepare a suspension with a concentration of 0.8 mg / mL. The suspension was ultrasonically exfoliated for 60 min (300 W), followed by centrifugation at 3000 rpm for 10 min. The supernatant was collected to obtain monolayer or few-layer Ti3C2T x A stable dispersion of MXene nanosheets.

[0060] Construction of the MXene conductive network: The prepared porous ceramic framework was placed in a sealed container, evacuated to -0.095 MPa, and maintained for 30 min. Then, the MXene dispersion prepared in step 1.2 (1.3 times the volume of the ceramic framework) was injected and maintained for 2 h to allow for thorough wetting. After removal, it was vacuum dried at 60 °C for 12 h. Finally, under argon protection, the temperature was increased to 350 °C at a rate of 2 °C / min and held for 2 h to obtain the porous composite matrix. The loading of MXene in the composite matrix was 10 wt% of the ceramic framework mass.

[0061] The gradient functionalized superhydrophobic layer is formed by the following method, with the material proportions and process parameters as follows:

[0062] Preparation of the composite functional slurry: Deionized water was used as the dispersion medium, and the total solid content of the slurry was 18 wt%. Specifically, PTFE dispersion (60 wt% solid content) accounted for 45 wt% of the total slurry mass, dodecyl fluoroheptyl methacrylate (DFMA) accounted for 35 wt% of the total slurry mass, and the ultraviolet photoinitiator (2-hydroxy-2-methyl-1-phenyl-1-propanone) was added at 2 wt% of the DFMA mass, with the remainder being deionized water. All components were stirred and mixed thoroughly, and then ultrasonically dispersed for 30 min.

[0063] The porous composite matrix was completely immersed in the above-mentioned composite functional slurry for 30 minutes, then removed and drained. It was then irradiated with ultraviolet light at a wavelength of 365 nm and an intensity of 10 mW / cm² for 20 minutes. The matrix was then placed in a muffle furnace and heated to 350 °C at a rate of 3 °C / min, held at that temperature for 1 hour, and cooled to obtain a gradient functionalized superhydrophobic layer with a thickness of 40 μm.

[0064] Preparation of metal catalyst layer and electrode assembly:

[0065] Pretreatment: The substrate coated with the superhydrophobic layer was ultrasonically cleaned with anhydrous ethanol for 15 min and vacuum dried at 80℃ for 2 h. Subsequently, corona treatment was performed: voltage 10 kV, electrode spacing 5 mm, treatment time 30 s.

[0066] Electrochemical deposition: The activated substrate was used as the working electrode, a platinum sheet as the counter electrode, and Ag / AgCl (saturated KCl) as the reference electrode. The electrolyte was a 0.5 mol / L hydrochloric acid aqueous solution containing 5 mmol / L chloroplatinic acid. Deposition was performed at a constant potential of 0 V (relative to Ag / AgCl) for 10 min under nitrogen protection. After deposition, the sample was rinsed with deionized water and dried at 60 °C for 2 h.

[0067] Post-treatment: Prepare a 5wt% perfluorosulfonic acid resin (Nafion) solution (ethanol to water volume ratio 1:1), spray it onto the surface of the catalyst layer (coating amount 0.2mg / cm²), and vacuum dry at 80℃ for 1h to obtain the final metal-supported superhydrophobic air electrode.

[0068] Depend on Figure 1 SEM scans of the metal-supported superhydrophobic air electrode revealed a tight bond between the ceramic framework / MXene network layer, the gradient functionalized superhydrophobic layer, and the outermost metal catalyst nanoparticles, with no obvious cracks or delamination. In particular, the MXene network exhibited excellent physical adhesion and chemical bonding with the ceramic framework, as well as with the superhydrophobic layer and the composite matrix. This ensures the structural integrity and long-term stability of the electrode under electrochemical operating conditions.

[0069] Example 2

[0070] This invention provides a metal-supported superhydrophobic air electrode for chlorination reactions. The air electrode comprises: a porous composite substrate, wherein the porous composite substrate is composed of a three-dimensional porous ceramic framework and an MXene nanosheet conductive network attached to its pores and surface; a gradient-functionalized superhydrophobic layer covering the surface of the porous composite substrate, wherein the gradient-functionalized superhydrophobic layer is composed of polytetrafluoroethylene and a fluoropolymer formed by in-situ polymerization of fluorinated acrylate monomers, and its chemical composition and surface energy change in a gradient from the substrate side to the outer surface side, giving the electrode superhydrophobicity; and a metal catalyst layer directly supported on the surface of the gradient-functionalized superhydrophobic layer.

[0071] The porous composite matrix is ​​prepared by a method including the following steps: using organic foam as a sacrificial template, impregnating a sol containing ceramic precursors and sintering aids, followed by drying and high-temperature sintering to form a porous ceramic framework with a three-dimensional interconnected network structure; using MAX phase powder as raw material, selectively etching with a lithium fluoride-containing hydrochloric acid solution or hydrofluoric acid solution to remove the aluminum atom layer; after washing the etched product to neutrality, intercalating it with an organic amine intercalating agent, followed by liquid-phase ultrasonic exfoliation under a protective atmosphere, and removing the unexfoliated thick sheets by centrifugation to obtain a stable dispersion of single-layer or few-layer MXene nanosheets; placing the porous ceramic framework in a sealed container and evacuating it, then injecting the MXene dispersion, using negative pressure to drive the dispersion to completely wet the pores of the framework; after removal, drying to allow the MXene nanosheets to adhere to the surface of the ceramic framework; and heat treatment under an inert atmosphere at a temperature of 500℃ to obtain the porous composite matrix.

[0072] Among them, the MAX phase powder is Nb2AlC; the ceramic precursor is titanium dioxide; and the organic amine intercalating agent is selected from tetramethylammonium hydroxide.

[0073] It should be noted that if the ceramic precursor is titanium oxide, then the sintering aid is niobium pentoxide.

[0074] The metal catalyst layer comprises an alloy selected from precious metals and at least one transition metal selected from iron, cobalt, nickel, and copper.

[0075] The gradient functionalized superhydrophobic layer is formed by the following method: impregnating a porous composite matrix in a composite functional slurry; triggering an in-situ polymerization reaction of monomers to form a fluoropolymer network; and then performing heat treatment at 380°C to melt polytetrafluoroethylene and fuse it with the polymer network to obtain the gradient functionalized superhydrophobic layer.

[0076] The composite functional slurry contains a polytetrafluoroethylene dispersion, a polymerizable fluorinated acrylate monomer, and an initiator. The polymerizable fluorinated acrylate monomer is dodecafluoroheptyl methacrylate; the polymerization initiator is a UV initiator or a thermal initiator.

[0077] This invention also provides a method for preparing a metal-supported superhydrophobic air electrode for chlorination reactions, comprising the following steps:

[0078] An MXene composite porous matrix was prepared, and then cleaned and dried to obtain a pretreated substrate.

[0079] The pretreated matrix is ​​immersed in the composite functional slurry, taken out and drained, and an in-situ polymerization reaction is triggered under the action of an initiator. Then, it is heat-treated at a temperature of 300℃ to 380℃ to form a gradient functionalized superhydrophobic layer.

[0080] Surface activation treatment is performed on the substrate coated with a superhydrophobic layer;

[0081] Using the activated substrate as the working electrode, an electrochemical deposition is performed in an electrolyte containing target metal ions to form a metal catalyst layer. A perfluorosulfonic acid resin solution is then coated on the surface of the metal catalyst layer and dried again to obtain a metal-supported superhydrophobic air electrode.

[0082] The surface activation treatment is a corona treatment, and the treatment conditions include: voltage 30kV, electrode spacing 10mm, and treatment time 90 seconds.

[0083] The electrochemical deposition employed a constant potential deposition method, with the deposition potential ranging from -0.5V to +0.5V relative to the Ag / AgCl reference electrode. The deposition was carried out under nitrogen protection for 20 minutes.

[0084] The metal precursor in the electrolyte is selected from silver nitrate, copper sulfate, nickel nitrate, and ferric chloride; the electrolyte is an aqueous solution of an organic acid, wherein the organic acid is selected from oxalic acid.

[0085] Specifically, the porous ceramic framework was prepared as follows: Polyurethane foam with a pore size of 80 PPI was used as a sacrificial template and completely impregnated in a ceramic precursor sol (sol solid content of 28 wt%). The ceramic precursor was titanium dioxide, and the sintering aid was niobium pentoxide, with the amount of niobium pentoxide added being 5 wt% of the titanium dioxide mass. Both were uniformly dispersed in the sol, and the dispersion medium was anhydrous ethanol. The sol was prepared as follows: 85.2 g of tetrabutyl titanate was dissolved in 150 mL of anhydrous ethanol to obtain solution A; 2.66 g of niobium pentoxide (Nb2O5) powder and 5 g of polyethylene glycol (PEG4000, pore-forming agent) were dispersed in a mixture of 50 mL of deionized water and 2 mL of nitric acid to obtain solution B; solution B was slowly added dropwise to solution A under vigorous stirring, and stirring was continued for 6 h to form a homogeneous sol. After impregnation, the sample was removed and centrifuged to remove excess sol (1000 rpm, 30 s), then dried at 60°C for 48 h. Subsequently, it was placed in a muffle furnace and heated to 500°C at a rate of 2°C / min, held for 2 h to remove organic matter; then heated to 1100°C at a rate of 5°C / min, held for 3 h to complete sintering, and the polyurethane template was removed, forming a porous titanium dioxide ceramic framework with a three-dimensional interconnected network structure. The framework porosity was 78%, the average pore size was 80 μm, and the main phase was anatase.

[0086] Preparation of MXene nanosheet dispersion: 2.0 g of Nb₂AlCMAX phase powder was added to 40 mL of 40% hydrofluoric acid (HF) aqueous solution. The mixture was etched in a constant-temperature water bath at 40 °C for 72 h with stirring to completely remove the Al atomic layer. The etched product was repeatedly washed with deionized water by centrifugation (4000 rpm, 10 min each time) until the pH of the supernatant reached 6.0. Then, 50 mL of tetramethylammonium hydroxide (TMAOH, 25% aqueous solution) was added as an intercalating agent, and the mixture was allowed to stand at room temperature for 24 h for intercalation. The intercalated product was transferred to an argon protective atmosphere, and deionized water was added to prepare a suspension with a concentration of 1.0 mg / mL. Liquid-phase ultrasonic exfoliation was performed using a 500 W ultrasonic instrument for 120 min, followed by centrifugation at 5000 rpm for 45 min to remove unexfoliated thick sheets and impurities. The supernatant was collected to obtain monolayer or few-layer (1-5 layers) Nb₂CT. x Stable dispersion of MXene nanosheets.

[0087] Construction of the MXene conductive network: The prepared porous titanium oxide ceramic framework was placed in a sealed container, and a vacuum was drawn to -0.09 MPa and maintained for 40 min. Then, the aforementioned MXene nanosheet dispersion was slowly injected, with the dispersion volume being 2.0 times the volume of the ceramic framework. This was maintained under negative pressure for 4 h to ensure complete wetting of the framework pores. The wetted ceramic framework was then removed and vacuum-dried at 70 °C for 24 h to allow uniform adhesion of the MXene nanosheets. Finally, heat treatment was performed under an argon inert atmosphere at 500 °C (the high-temperature endpoint within the scope of the claims), with a heating rate of 3 °C / min and a holding time of 3 h, to obtain a porous composite matrix. The loading of MXene in the composite matrix was approximately 15 wt% of the ceramic framework mass. The sheet resistivity, measured by the four-probe method, was 2.8 Ω / sq.

[0088] Gradient-functionalized superhydrophobic layers are formed through the following methods:

[0089] Preparation of the composite functional slurry: Xylene was used as the dispersion medium. The PTFE dispersion (55wt% solids content) was added at 40wt% of the total slurry mass, the polymerizable fluorinated acrylate monomer (dodecyl fluoroheptyl methacrylate, DFMA) at 30wt% of the total slurry mass, the thermal initiator (benzoyl peroxide, BPO) at 1wt% of the DFMA mass, and 0.5wt% of a fluorocarbon surfactant (FC-4430) was added, with the balance being xylene. All components were stirred and mixed under light-protected conditions for 4 hours until the system was homogeneous.

[0090] The porous composite matrix was completely immersed in the aforementioned composite functional slurry for 20 minutes. After immersion, excess slurry was drained from the surface (controlling the wet film thickness to 60 μm). It was then placed in an oven and preheated at 80°C for 30 minutes under nitrogen protection, followed by heating to 120°C and holding for 2 hours to complete the thermally initiated in-situ polymerization reaction, forming a fluoropolymer network. The polymerized matrix was placed in a tube furnace and heated to 380°C (the high-temperature endpoint within the scope of the claims) at a rate of 5°C / min under a nitrogen atmosphere, and held for 1.5 hours to allow the PTFE to melt and interpenetrate and fuse with the fluoropolymer network. After cooling to room temperature, a gradient functionalized superhydrophobic layer with a thickness of 50 μm was formed.

[0091] Preparation of metal catalyst layer and electrode assembly:

[0092] Pretreatment: The substrate prepared above and coated with a superhydrophobic layer was ultrasonically cleaned with acetone and isopropanol for 15 min each to remove residual impurities on the surface, and then vacuum dried at 100°C for 2 h to obtain the pretreated substrate.

[0093] Surface activation treatment: The pretreated substrate is subjected to corona treatment under the following conditions: voltage 30kV, electrode spacing 10mm, treatment time 90 seconds, and treatment environment is room temperature and normal pressure air.

[0094] Metal catalyst layer deposition: A three-electrode system was constructed using the activated substrate as the working electrode, a titanium mesh as the counter electrode, and Ag / AgCl (saturated KCl) as the reference electrode. The electrolyte was a 0.1 mol / L aqueous solution of oxalic acid containing 3.0 mmol / L palladium chloride and 6.0 mmol / L copper sulfate as metal precursors. Under nitrogen protection (nitrogen flow rate 30 mL / min), a potentiostatic deposition method was used, with a deposition potential of -0.3 V relative to the Ag / AgCl reference electrode, a deposition time of 20 minutes, a deposition temperature of 30 °C, and magnetic stirring at 200 rpm. After deposition, the electrode was removed, rinsed sequentially with dilute oxalic acid solution and deionized water, and vacuum dried at 80 °C for 3 hours to form a Pd-Cu alloy metal catalyst layer.

[0095] Post-treatment: Prepare a 1 wt% perfluorosulfonic acid resin solution (the solvent is a mixture of ethanol and water in a volume ratio of 3:1), and uniformly coat it onto the surface of the metal catalyst layer by spraying. The coating amount is 0.15 mg / cm². Then, vacuum dry it at 60 °C for 2 h to obtain the final metal-supported superhydrophobic air electrode.

[0096] Comparative Example 1

[0097] This comparative example uses a traditional carbon paper / PTFE / noble metal catalyst system, combined with a conventional physical coating-sintering process to prepare the comparative electrode.

[0098] The specific preparation steps are as follows:

[0099] Substrate: Commercial carbon paper (TorayTGP-H-060, 190μm thick, 78% porosity), cut to 2cm×2cm size.

[0100] Hydrophobication treatment: Prepare a PTFE dispersion (DuPont, FR301B) with a solid content of 20 wt%. Immerse the carbon paper completely in the dispersion for 5 minutes, remove it, hang it vertically to drain for 5 minutes, and control the wet film thickness.

[0101] Sintering and molding: The drained carbon paper is placed in a muffle furnace and heated to 340°C at 5°C / min in an air atmosphere. The temperature is held for 30 minutes to melt PTFE and form a uniform hydrophobic layer on the surface and in the pores of the carbon paper.

[0102] Catalyst slurry preparation: Take 20 mg of commercial Pt / C catalyst (Johnson Matthey, 20 wt% Pt / C), add 1 mL of isopropanol, 0.5 mL of deionized water and 50 μL of 5 wt% Nafion solution (as a binder), and ultrasonically disperse for 30 minutes to form a uniform catalyst slurry.

[0103] Coating and drying: The catalyst slurry was uniformly coated onto one side of the hydrophobic carbon paper using a spraying method, with the catalyst loading controlled at 0.5 mg Pt / cm². After coating, the electrode was dried in a vacuum drying oven at 80 °C for 2 hours to obtain the electrode of Comparative Example 1.

[0104] Comparative Example 2

[0105] The preparation method of this comparative example is basically the same as that of Example 1 of the present invention, except that the construction step of the gradient functionalized superhydrophobic layer is replaced, as follows:

[0106] The same Ti3C2T was prepared exactly according to the steps of Example 1 of this invention. x MXene@zirconia porous composite matrix.

[0107] PTFE slurry preparation: Prepare only a single PTFE dispersion slurry. Take a PTFE dispersion with a solid content of 60 wt%, dilute it with deionized water to a solid content of 15 wt%, add 2 wt% (relative to the mass of PTFE solids) of ethylene glycol as a wetting agent, and stir until homogeneous.

[0108] Impregnation and drying: The prepared porous composite matrix is ​​immersed in the above PTFE slurry for 30 minutes, then removed and drained for 10 minutes. It is then dried at 80°C for 12 hours.

[0109] Sintering: The dried substrate is placed in a muffle furnace and heated to 350°C at a rate of 5°C / min in air atmosphere, and held for 30 minutes to melt and sinter the PTFE particles, forming a uniform PTFE hydrophobic layer on the substrate surface. This hydrophobic layer has a thickness approximately 40 μm, similar to the gradient functionalized superhydrophobic layer of this invention.

[0110] Preparation of metal catalyst layer and electrode assembly: All subsequent steps, including surface corona activation, electrochemical deposition of platinum catalyst, Nafion post-treatment, etc., were carried out under the same conditions and parameters as in Example 1 to ensure that the variables were unique.

[0111] The final electrode of Comparative Example 2 was obtained, which differs from the electrode of Example 1 only in the structure and preparation process of the superhydrophobic layer.

[0112] Comparative Example 3

[0113] The preparation method of this comparative example is basically the same as that of Example 1 of the present invention, except for a key substitution in the preparation step of the porous composite matrix: conductive carbon black (CB) slurry is used instead of MXene dispersion to construct the conductive phase of the matrix, as follows:

[0114] The same yttrium-stabilized zirconia (YSZ) porous ceramic framework was prepared using the same steps and parameters as in Example 1 of this invention.

[0115] Preparation of conductive carbon black slurry: 2.0g conductive carbon black (VulcanXC-72R), 0.2g polyvinylidene fluoride (PVDF, binder), and 20mL N-methylpyrrolidone (NMP, solvent).

[0116] PVDF was dissolved in NMP, and conductive carbon black was slowly added while stirring. The mixture was stirred at high speed for 12 hours, followed by ultrasonic treatment for 2 hours to obtain a uniform and stable conductive carbon black slurry (solid content of about 10 wt%).

[0117] Vacuum-assisted impregnation: The prepared porous ceramic skeleton is placed in a sealed container, and a vacuum is drawn to -0.095 MPa and maintained for 30 minutes. Then, the above-mentioned conductive carbon black slurry (1.3 times the volume of the ceramic skeleton) is injected and maintained for 2 hours to allow the slurry to fully impregnate the skeleton.

[0118] Drying and curing: The impregnated skeleton was removed and vacuum dried at 80°C for 24 hours. Subsequently, under argon protection, the temperature was increased to 300°C at 5°C / min and held for 2 hours to cure the PVDF, resulting in a CB@zirconia porous composite matrix. The loading of carbon black in the composite matrix was controlled to be 10 wt% of the ceramic skeleton mass (consistent with the loading of MXene in Example 1).

[0119] Preparation of metal catalyst layer and electrode assembly: All subsequent steps, including the construction of gradient functionalized superhydrophobic layer (completely in accordance with the formulation and process of Example 1), surface corona activation, electrochemical deposition of platinum catalyst, Nafion post-treatment, etc., were carried out under the same conditions and parameters as in Example 1 to ensure the uniqueness of variables.

[0120] The final electrode of Comparative Example 3 was obtained, which differed from the electrode of Example 1 only in the conductive phase material (conductive carbon black vs. MXene) in the matrix and the network structure formed therein.

[0121] Performance testing

[0122] To evaluate the performance of the air electrode prepared in this invention, the electrodes of Examples 1, 2, 1, 2, and 3 were assembled in a laboratory-scale electrolytic cell, and their electrochemical performance and long-term stability were tested using a standard three-electrode system. All tests were conducted at room temperature (25±1℃), using a saturated sodium chloride solution (5.0 mol / L, simulating the brine environment of a chlor-alkali industry) as the electrolyte solution. Specific test conditions are as follows:

[0123] 1. Testing Method

[0124] Linear sweep voltammetry (LSV): The potential scan range is 1.0V to 1.8V relative to the reversible hydrogen electrode (RHE), and the scan rate is 10mV / s. It is used to evaluate the chlorine evolution reaction (CER) activity and onset potential of the electrode.

[0125] Electrochemical impedance spectroscopy (EIS): Performed at a constant potential 50 mV above the OER onset potential, with a frequency range of 100 kHz to 0.01 Hz and an AC amplitude of 10 mV, used to analyze charge transfer resistance (R). ct And the mass transfer characteristics inside the electrode.

[0126] Potential stability test: The electrode was continuously operated for 100 hours at a constant potential of 1.5V relative to RHE, and the change in current density over time was recorded to evaluate the long-term electrochemical stability of the electrode.

[0127] Contact angle measurement: Using a contact angle meter, 5 μL of deionized water was dropped onto the outer surface of the electrode to measure the static water contact angle and evaluate the superhydrophobicity of the electrode.

[0128] Chlorine production and current efficiency determination: Electrolysis was performed at a constant potential of 1.5V (vs. RHE) for 2 hours. The gas generated at the anode was collected by water displacement and the chlorine content was determined by iodometric titration. The current efficiency was then calculated.

[0129] The results are shown in Table 1.

[0130] Table 1 Performance Test Results

[0131] Group Chlorine evolution initiation potential (V) Current density (mA / cm²) Charge transfer resistance (Ω·cm²) Contact angle (°) Chlorine current efficiency (%) Example 1 1.23 450 0.85 158 96.2 Example 2 1.26 420 1.02 155 95.5 Comparative Example 1 1.35 280 2.43 145 90.1 Comparative Example 2 1.30 350 1.80 142 92.8 Comparative Example 3 1.32 320 2.11 153 91.5

[0132] As shown in Table 1, the electrodes of Examples 1 and 2 of this application exhibit comprehensive advantages in chlorine production performance testing. Their chlorine evolution onset potentials are as low as 1.23V and 1.26V, respectively, and their current densities at a working potential of 1.5V reach 450mA / cm² and 420mA / cm², respectively, far superior to the comparative examples, demonstrating a lower reaction energy barrier and a higher reaction rate. Furthermore, their charge transfer impedances are only 0.85Ω·cm² and 1.02Ω·cm², respectively, significantly lower than the comparative examples, proving that the three-dimensional interconnected conductive network constructed from MXene nanosheets can greatly promote electron transport. The invention reduces electrochemical polarization; its static water contact angle is greater than 155°, reaching the superhydrophobic standard, which is about 13-16° higher than Comparative Example 2 without gradient functionality, and also better than Comparative Example 3 with carbon black matrix. The excellent surface energy distribution and micro-roughness brought by the gradient structure, as well as the compatibility with the MXene matrix, are the core reasons. At the same time, the chlorine current efficiency of Examples 1 and 2 reaches 96.2% and 95.5% respectively, which is higher than all comparative examples. The stable gas film formed by the excellent superhydrophobic properties effectively isolates the electrolyte, inhibits oxygen evolution side reaction, and improves product selectivity. Comparing different comparative examples, it can be seen that compared with Comparative Example 1 with traditional material process, the electrode of the present invention achieves a qualitative leap in all indicators; compared with Comparative Example 2 with single PTFE coating, the gradient functionalized superhydrophobic layer plays an irreplaceable role in optimizing the three-phase interface and reducing mass transfer resistance; compared with Comparative Example 3 with carbon black conductive network, MXene nanosheets have unique value in constructing a highly conductive and highly stable three-dimensional network.

[0133] In summary, the data in Table 1 fully verify that this invention, through the synergistic innovative design of MXene composite porous matrix, gradient functionalized superhydrophobic layer and metal catalyst layer, has successfully prepared an advanced air electrode with high activity, low impedance, strong hydrophobicity and high selectivity, which can be adapted to efficient and stable chlorine production reaction.

[0134] This application provides a metal-supported superhydrophobic air electrode for chlorination reactions. Addressing the core technical problems of existing chlorination air electrodes, such as easy corrosion of the carbon matrix, weak interfacial bonding, difficulty in precise control of microstructure, and easy performance degradation and deactivation, this application innovates and optimizes the electrode from all dimensions: material selection, structural design, interface construction, and preparation process. The electrode uses a porous insulating / semiconductor ceramic as a highly stable structural framework, within which a continuous MXene nanosheet conductive network is constructed in situ. Relying on the strong interactions between the abundant functional groups on the MXene surface and the ceramic framework and its own layers, a two-dimensional electron channel with both good hydrophilicity and excellent electron delocalization is formed, enabling rapid electron transport to the active center of the metal catalyst, significantly reducing ohmic polarization, and solving the problems of limited intrinsic conductivity and easy corrosion damage of the conductive network in traditional carbon-based electrodes. On the substrate surface, a composite functional layer with a continuous gradient of chemical composition and wettability is constructed through chemical bonding and physical interlocking, achieving a smooth transition from a strongly anchored polymer network to a PTFE-rich superhydrophobic surface layer. This not only improves the interfacial bonding strength and effectively prevents hydrophobic layer peeling, but also… The electrode achieves chloride ion enrichment and rapid mass transfer through internal hydrophilic microchannels, and promotes rapid desorption of chlorine products by leveraging the superhydrophobic properties of the outer layer. This optimizes the mass transfer kinetics of the gas-liquid-solid three-phase reaction interface, reduces electrochemical polarization, and improves reaction efficiency and interface stability. MXene nanosheets are used as a noble metal catalyst support. The abundant defects on their surface and the tunable work function form a strong metal-support interaction, modulating the electronic structure of the catalyst and shifting the d-band center. This optimizes the adsorption strength of chlorine-containing intermediates, reduces the rate-determining energy barrier of the chlorine evolution reaction, and suppresses oxygen evolution side reactions, significantly improving the intrinsic chlorine evolution catalytic activity and reaction selectivity of the electrode. An all-inert integrated anti-corrosion architecture is constructed using inert materials such as ceramics, MXene, fluoropolymers, and PTFE. Each component exhibits excellent chemical stability in harsh chlorine-producing environments with strong oxidation and acidic chlorine content. Through a close combination of chemical and physical interactions, it can synergistically resist multiple stress damages such as electric fields, ion penetration, and gas erosion, fundamentally avoiding problems such as carbon corrosion and structural collapse. This endows the electrode with excellent mechanical durability and environmental tolerance, significantly extending its service life. Meanwhile, the preparation method of this electrode has clear process steps and controllable parameters. By adjusting the concentration of MXene dispersion, vacuum impregnation conditions, polymerization and heat treatment parameters, the density of conductive network, porosity and the structure and thickness of gradient hydrophobic layer can be precisely controlled. This enables the targeted design and optimization of key performance indicators such as electrode conductivity, hydrophobicity and catalytic active site distribution. It can meet the specific requirements of electrode performance in different application scenarios such as disinfection, wastewater treatment and chemical synthesis. The preparation process has good repeatability and scalability.This invention optimizes the entire chain of the chlorine-producing electrocatalytic reaction, including charge transport, three-phase interface mass transfer, catalytic activity and selectivity, and structural corrosion resistance and durability. It comprehensively improves the overall performance of the electrode, fundamentally solves many defects of the existing technology, and provides a new type of air electrode that is suitable for high efficiency, high stability and complex working conditions in the field of chlorine production, and has good practical application value.

[0135] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A metal-supported superhydrophobic air electrode for chlorine production reactions, characterized in that, The air electrode includes: A porous composite matrix, wherein the porous composite matrix is ​​composed of a three-dimensional porous ceramic framework and an MXene nanosheet conductive network attached to its pores and surface; A gradient-functionalized superhydrophobic layer is applied to the surface of the porous composite substrate. This layer is composed of polytetrafluoroethylene (PTFE) and a fluoropolymer formed by in-situ polymerization of fluoroacrylate monomers. The chemical composition and surface energy of this layer exhibit a gradient from the substrate side to the outer surface side, thus endowing the electrode with superhydrophobicity. A metal catalyst layer directly loaded on the surface of the gradient functionalized superhydrophobic layer.

2. The metal-supported superhydrophobic air electrode for chlorine production reaction according to claim 1, characterized in that, The porous composite matrix is ​​prepared by a method comprising the following steps: Using organic foam as a sacrificial template, a sol containing ceramic precursors and sintering aids is impregnated, and then dried and sintered at high temperature to form a porous ceramic skeleton with a three-dimensional interconnected network structure. Using MAX phase powder as raw material, selective etching is performed using a lithium fluoride-containing hydrochloric acid solution or hydrofluoric acid solution to remove the aluminum atom layer; After the etched product is washed to neutral, it is intercalated using an organic amine intercalating agent, followed by liquid-phase ultrasonic exfoliation under a protective atmosphere, and the unexfoliated thick sheets are removed by centrifugation to obtain a stable dispersion of monolayer or few-layer MXene nanosheets. The porous ceramic framework was placed in a sealed container and evacuated. Then, the MXene dispersion was injected, and the dispersion was used to completely wet the pores of the framework by using negative pressure. After being removed, it was dried so that the MXene nanosheets adhered to the surface of the ceramic framework. The porous composite matrix is ​​obtained by heat treatment under an inert atmosphere at a temperature of 200°C to 500°C.

3. The metal-supported superhydrophobic air electrode for chlorine production reaction according to claim 2, characterized in that, The MAX phase powder is at least one of Ti3AlC2, Ti2AlC or Nb2AlC; the ceramic precursor is at least one of zirconium oxide, titanium oxide or aluminum oxide; the organic amine intercalating agent is selected from dimethyl sulfoxide, tetrabutylammonium hydroxide or tetramethylammonium hydroxide.

4. The metal-supported superhydrophobic air electrode for chlorine production reaction according to claim 1, characterized in that, The metal catalyst layer comprises at least one noble metal selected from platinum, palladium, iridium, ruthenium, and gold, or an alloy formed by the noble metal and at least one transition metal selected from iron, cobalt, nickel, and copper.

5. The metal-supported superhydrophobic air electrode for chlorine production reaction according to claim 1, characterized in that, The gradient functionalized superhydrophobic layer is formed by the following method: impregnating the porous composite matrix in a composite functional slurry; triggering the in-situ polymerization reaction of the monomer to form a fluoropolymer network; and then performing heat treatment at 300°C to 380°C to melt the polytetrafluoroethylene and fuse it with the polymer network to obtain the gradient functionalized superhydrophobic layer.

6. The metal-supported superhydrophobic air electrode for chlorine production reaction according to claim 5, characterized in that, The composite functional slurry comprises a polytetrafluoroethylene dispersion, a polymerizable fluorinated acrylate monomer, and an initiator, wherein the polymerizable fluorinated acrylate monomer is dodecafluoroheptyl methacrylate; and the polymerization initiator is an ultraviolet photoinitiator or a thermal initiator.

7. A method for preparing a metal-supported superhydrophobic air electrode for chlorination reaction as described in any one of claims 1-6, characterized in that, Including the following steps: An MXene composite porous matrix was prepared, and then cleaned and dried to obtain a pretreated substrate. The pretreated matrix is ​​immersed in the composite functional slurry, taken out and drained, and an in-situ polymerization reaction is triggered under the action of an initiator. Then, it is heat-treated at a temperature of 300℃ to 380℃ to form a gradient functionalized superhydrophobic layer. Surface activation treatment is performed on the substrate coated with a superhydrophobic layer; Using the activated substrate as the working electrode, an electrochemical deposition is performed in an electrolyte containing target metal ions to form a metal catalyst layer. A perfluorosulfonic acid resin solution is then coated on the surface of the metal catalyst layer and dried again to obtain the metal-supported superhydrophobic air electrode.

8. The method for preparing a metal-supported superhydrophobic air electrode for chlorination reaction according to claim 7, characterized in that, The surface activation treatment is a corona treatment, and the treatment conditions include: voltage 10-48kV, electrode spacing 5-10mm, and treatment time 30-150 seconds.

9. The method for preparing a metal-supported superhydrophobic air electrode for chlorination reaction according to claim 7, characterized in that, The electrochemical deposition was performed using a constant potential deposition method, with the deposition potential ranging from -0.5V to +0.5V relative to the Ag / AgCl reference electrode. The deposition was carried out under nitrogen protection for 10-30 minutes.

10. The method for preparing a metal-supported superhydrophobic air electrode for chlorination reaction according to claim 9, characterized in that, The metal precursor in the electrolyte is selected from at least one of chloroplatinic acid, chloropalladium acid, palladium chloride, iridium chloride, ruthenium trichloride, silver nitrate, copper sulfate, cobalt chloride, nickel nitrate, and ferric chloride; the electrolyte is an aqueous solution of an inorganic acid or an organic acid, wherein the inorganic acid is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, and the organic acid is selected from at least one of formic acid, acetic acid, and oxalic acid.

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