Method for preparing boron etching modified gas diffusion electrode and in-situ hydrogen peroxide production application

Abstract

The present application relates to the technical fields of electrochemical energy and functional carbon material, in particular to a preparation method of boron etching modified gas diffusion electrode and in-situ hydrogen peroxide production application, comprising: sequentially placing original carbon felt in ethanol solution and deionized water, drying under vacuum condition after cleaning to obtain pretreated carbon felt substrate; twice coating the pretreated carbon felt substrate with polytetrafluoroethylene and gradient heat treatment to obtain gradient polytetrafluoroethylene modified carbon felt, coating one side with a solution containing boron substance, then performing spin coating treatment under the condition of 50-70 DEG C, draining and drying under vacuum condition to obtain carbon felt loaded with boron-containing substance; placing it in a tube furnace under inert atmosphere, calcining at 500-600 DEG C for 20-40 min, and obtaining boron etching modified gas diffusion electrode after cooling. Thus, the problems of PTFE hindering electron transmission, limited catalytic performance of carbon material, poor hydrogen peroxide preparation effect and the like in the prior art are solved.

Description

Technical Field

[0001] This invention relates to the field of electrochemical energy and functional carbon materials technology, specifically to a method for preparing a boron-etched modified gas diffusion electrode and its application in in-situ hydrogen peroxide production. Background Technology

[0002] Hydrogen peroxide, as an important green oxidant, shows broad application prospects in environmental remediation, chemical synthesis, and energy conversion. Traditional industrial production of hydrogen peroxide often employs the anthraquinone process, which suffers from inherent drawbacks such as complex processes, high energy consumption, and difficulty in achieving distributed production. In contrast, the direct synthesis of hydrogen peroxide via an electrochemical oxygen reduction reaction through a two-electron pathway offers a novel technological route for the green and efficient preparation of hydrogen peroxide.

[0003] Air electrodes occupy a central position in the electrochemical synthesis of hydrogen peroxide. Their core function is to serve as the working electrode for the oxygen reduction reaction, enabling efficient electron exchange with the reactant (oxygen) and thus achieving the selective reduction and conversion of oxygen to hydrogen peroxide. The overall performance of the air electrode directly determines the reaction efficiency, product selectivity, and system stability of the electrochemical synthesis process, and is one of the key bottlenecks for the large-scale application of this technology.

[0004] Traditional air electrodes typically utilize loaded carbon powder and polytetrafluoroethylene (PTFE) to modulate electrode structure and performance. PTFE imparts excellent hydrophobicity to the electrode, a crucial property for preventing electrolyte intrusion and maintaining the continuity of the gas mass transfer pathway. However, PTFE also has significant limitations; while constructing a hydrophobic structure, it may hinder electron transport within the electrode, reducing charge transfer efficiency. Carbon materials are currently the most widely used two-electron oxygen reduction catalysts, possessing excellent conductivity. However, their catalytic performance is often limited by surface structure—ordinary carbon materials have a limited number of surface defects, lacking sufficient and suitable active sites, and the homogeneity of their surface structure prevents them from fully realizing their catalytic potential. Furthermore, the easy formation of unstable intermediates during the reaction further restricts the efficiency and selectivity of hydrogen peroxide formation. Summary of the Invention

[0005] This application provides a method for preparing a boron-etched modified gas diffusion electrode and its application in in-situ hydrogen peroxide production, in order to solve the problems of PTFE hindering electron transport, the limited catalytic performance of carbon materials, and the poor hydrogen peroxide production effect 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 method for preparing a boron-etched modified gas diffusion electrode, characterized in that the preparation method includes the following steps: S1. Place the original carbon felt in ethanol solution and deionized water respectively for ultrasonic cleaning for 8-12 minutes. After cleaning, dry it under vacuum for 5-10 hours to obtain the pretreated carbon felt substrate. S2. The pretreated carbon felt substrate is subjected to two polytetrafluoroethylene coatings and gradient heat treatments to obtain gradient polytetrafluoroethylene modified carbon felt. S3. Coat one side of the gradient polytetrafluoroethylene modified carbon felt with a solution containing boron, and then spin-coat it at 50-70°C to form a uniform covering layer. After draining, dry it under vacuum at 60-80°C for 5-10 hours to obtain a carbon felt loaded with boron. S4. Under an inert atmosphere, the carbon felt loaded with boron-containing material is placed in a tube furnace and calcined at 450-650°C for 20-40 minutes. After cooling, the boron-etched modified gas diffusion electrode is obtained.

[0007] Further, the pretreated carbon felt substrate is subjected to two polytetrafluoroethylene (PTFE) coatings and gradient heat treatments to obtain gradient PTFE-modified carbon felt, comprising: S2-1. The pretreated carbon felt substrate is suspended in a dip coating machine and immersed in a 15-25wt% polytetrafluoroethylene dispersion for 12-18 times for 15-25s each time. It is then hung vertically for 8-12min to drain and dried under vacuum at 60-80℃ for 5-10h. Subsequently, it is calcined at 350-370℃ for 20-40min and cooled to obtain a primary polytetrafluoroethylene modified carbon felt. S2-2. The polytetrafluoroethylene modified carbon felt is suspended again in a dip coating machine and immersed in a 5-15wt% polytetrafluoroethylene dispersion for 15-25 seconds each time, 4-6 times. It is then hung vertically for 8-12 minutes to drain and dried under vacuum at 60-80℃ for 5-10 hours. Subsequently, it is calcined at 320-340℃ for 20-40 minutes and cooled to obtain graded polytetrafluoroethylene modified carbon felt.

[0008] Furthermore, the boron-containing substance is selected from at least one of boric acid, borax, or boron oxide.

[0009] Furthermore, the boron-containing solution is an ethanol solution with a concentration of 0.1-1.0M.

[0010] Furthermore, the spin coating process is performed at a speed of 200-400 rpm and the number of cycles is 2-4.

[0011] Furthermore, the inert atmosphere is a nitrogen or argon atmosphere.

[0012] The present invention also provides a boron-etched modified gas diffusion electrode, which is prepared by the aforementioned method.

[0013] It should be noted that the boron etch-modified gas diffusion electrode includes a carbon felt substrate and a boron defluorination etch surface reconstruction layer. During the formation of the surface reconstruction layer, boron oxides interact with the fluorine species to form a boron-fluorine coordination structure, thereby inducing defluorination etching and structural rearrangement on the surface of the carbon felt fiber. Boron-containing functional structures, carbon defect structures, or a combination of both are formed on the surface of the carbon felt fiber, which further promotes the recombination of surface active carbon species to form an amorphous carbon layer. After the above surface reconstruction, the electronic structure and wetting properties of the carbon felt surface are regulated, which is conducive to the construction of a stable gas-liquid-solid three-phase interface and promotes the mass transfer of oxygen to the reaction interface. The boron-etched modified gas diffusion electrode is used as an air cathode in the electrochemical oxygen reduction reaction system to prepare hydrogen peroxide.

[0014] This invention also provides an application of a boron-etched modified gas diffusion electrode in the electrochemical in-situ generation of hydrogen peroxide.

[0015] Furthermore, the boron-etched side of the gas diffusion electrode is brought into contact with the electrolyte, while the untreated side is exposed to air or an oxygen atmosphere. A constant potential electrolysis is performed in the electrochemical system by applying an external potential of -0.6V to -1.2V.

[0016] Furthermore, the electrolyte is an aqueous solution of sodium sulfate with a concentration of 10-100 mM.

[0017] It should be noted that a boron-etched modified gas diffusion electrode for electrochemical in-situ generation of hydrogen peroxide includes the following steps: A boron-etched modified gas diffusion electrode was used as the working electrode; a graphite rod was selected as the counter electrode; and a silver / silver chloride (Ag / AgCl) electrode was used as the reference electrode. A 50 mM sodium sulfate aqueous solution was prepared as the electrolyte, using deionized water. The boron-etched side of the working electrode was brought into contact with the electrolyte, while the unetched side was exposed to air. An external potential was applied to the three-electrode system in constant potential mode.

[0018] The concentration of hydroxide was analyzed using a standard iodometric method, in which 1 mL of 0.1 M potassium hydrobenzoate aqueous solution and 1 mL of 0.4 M potassium iodide aqueous solution were added to the test solution, and the reaction was allowed to proceed for 30 minutes. H₂O₂ molecules react with iodide ions (I₂O₂). - The reaction (H₂O₂ + 3I₂) occurs under acidic conditions. - +2H + →I3 - +2H₂O) to generate triiodide ions (I₃) - It has strong absorption at 350 nm.

[0019] The beneficial effects achieved by using the present invention described above are as follows: 1. This invention proposes a method for preparing a boron-etched modified gas diffusion electrode, in which a boron-containing precursor is converted into boron oxide (BO) with Lewis acidity during heat treatment. x ), preferentially coordinate or substitute with active fluorine species produced by the pyrolysis of polytetrafluoroethylene (PTFE), forming an unstable transition state structure (such as [BO)). x F y ] n This process weakens the CF bonds in PTFE, inducing selective defluorination etching of the carbon substrate, accompanied by carbon skeleton rearrangement and the formation of defects (such as vacancies and edge sites). This boron-induced etching mechanism constructs a multi-level rough structure and abundant defect sites on the carbon fiber surface, significantly improving the electrode's reactivity accessibility and active site density. 2. Simultaneously, through the synergistic treatment of gradient PTFE coating and boron etching, a functional gradient structure is formed along the thickness direction of the electrode, where hydrophobic gas sides and hydrophilic reactive sides coexist. The PTFE coating layer maintains the hydrophobicity of the gas side, ensuring continuous oxygen mass transfer; while the BO, BOC, and -OH functional groups introduced by boron etching significantly enhance the hydrophilicity of the reactive side, promoting electrolyte wetting. This gradient structure can effectively stabilize the gas-liquid-solid three-phase interface, prevent electrolyte intrusion into the gas channel, and simultaneously improve the local concentration and mass transfer efficiency of oxygen at the reaction interface. 3. The boron-containing functional groups (BO, BOC) and the carbon defect structures introduced during boron etching can regulate the electron distribution and local charge state on the surface of carbon materials, optimizing the oxygen molecule adsorption energy and the stability of intermediate products. This precise regulation of the surface chemical environment allows the oxygen reduction reaction (ORR) to preferentially proceed along the two-electron pathway, significantly improving the selectivity and Faraday efficiency of hydrogen peroxide generation. 4. The gradient PTFE structure ensures the continuity and hydrophobic stability of the gas channel, while the boron etched reconstruction layer introduces hydrophilic sites while maintaining the integrity of the overall conductive network of the carbon skeleton. This design achieves an effective balance between gas mass transfer capability and electron transport efficiency, overcoming the technical contradiction in traditional electrodes where hydrophobic components hinder electron transport and hydrophilic components affect gas mass transfer. 5. The present invention adopts a preparation process that combines step-by-step impregnation-spin coating-heat treatment. The steps are clear and the parameters are controllable. It does not require complex equipment or harsh conditions, has good process repeatability and potential for large-scale production, and is suitable for industrial application needs. It also clarifies its application in the electrochemical in-situ synthesis of hydrogen peroxide. This solves the problems in existing technologies, such as PTFE hindering electron transport, the limited catalytic performance of carbon materials, and the poor hydrogen peroxide preparation effect.

[0020] 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

[0021] 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: Figure 1 Comparison of air electrode structures with those encapsulated in gradient polytetrafluoroethylene and those with original carbon felt; Figure 2 Scanning electron microscope image of a polytetrafluoroethylene-modified carbon felt air electrode; Figure 3 Scanning electron microscope image of a boron-etched modified gas diffusion electrode; Figure 4 Fourier transform infrared (FTIR) comparison spectra of different electrodes; Figure 5 This is the standard curve for hydrogen peroxide. Figure 6 The graph shows the hydrogen peroxide yield for different electrodes. Detailed Implementation

[0022] 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.

[0023] 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.

[0024] The following description, with reference to the accompanying drawings, illustrates a method for preparing a boron-etched modified gas diffusion electrode and its application in in-situ hydrogen peroxide production according to embodiments of this application. Addressing the problem of poor hydrogen peroxide production efficiency mentioned in the background art, this application provides a method for preparing a boron-etched modified gas diffusion electrode. In this method, a boron-containing precursor undergoes dehydration and condensation reactions during heating, preferentially forming boron oxides (B₂O₃ or BO₄) with Lewis acid properties.x These boron-oxygen species can first interact with the surface of polytetrafluoroethylene (PTFE), and then undergo coordination or substitution reactions with the active fluorinated groups generated during the thermal decomposition of PTFE to form unstable [BO] compounds. x F y ] n A transition state-like structure is constructed. The formation of the transition state weakens the original CF bond binding energy, thereby inducing selective defluorination etching on the carbon matrix surface, accompanied by local carbon framework rearrangement and defect generation. Furthermore, the introduction of BO, BOC, and hydroxyl functional structures selectively weakens the original local hydrophobicity of PTFE, thus constructing a functional gradient structure with both hydrophobic gas and hydrophilic reactive sides along the electrode thickness direction. This structure is beneficial for stabilizing the gas-liquid-solid three-phase interface and promoting oxygen enrichment and mass transfer at the reaction interface, ultimately guiding the oxygen reduction reaction preferentially along a two-electron pathway, achieving highly selective in-situ generation of hydrogen peroxide.

[0025] The present invention will be further described in conjunction with the following embodiments.

[0026] Example 1

[0027] This application discloses a method for preparing a boron-etched modified gas diffusion electrode, the method comprising the following steps: S1. The original carbon felt was placed in ethanol solution and deionized water respectively for ultrasonic cleaning for 10 min. After cleaning, it was dried under vacuum for 6 h to obtain the pretreated carbon felt substrate. S2. The pretreated carbon felt substrate is coated with polytetrafluoroethylene twice and subjected to gradient heat treatment to obtain gradient polytetrafluoroethylene modified carbon felt. S3. Coat one side of the gradient polytetrafluoroethylene modified carbon felt with a solution containing boron, and then spin-coat it at 60°C to form a uniform covering layer. After draining, dry it under vacuum at 70°C for 6 hours to obtain a carbon felt loaded with boron. S4. Under an inert atmosphere, carbon felt loaded with boron-containing material is placed in a tube furnace and calcined at 550°C for 30 min. After cooling, a boron-etched modified gas diffusion electrode is obtained.

[0028] Preferably, the pretreated carbon felt substrate is subjected to two polytetrafluoroethylene (PTFE) coatings and gradient heat treatments to obtain gradient PTFE-modified carbon felt, comprising: S2-1. The pretreated carbon felt substrate is suspended in a dip coating machine and immersed in a 20wt% polytetrafluoroethylene dispersion 15 times for 20s each time. It is then hung vertically for 10min to drain and dried under vacuum at 70℃ for 6h. Subsequently, it is calcined at 360℃ for 30min and cooled to obtain a primary polytetrafluoroethylene modified carbon felt. S2-2. The polytetrafluoroethylene modified carbon felt is suspended again in a dip coating machine and immersed in a 10wt% polytetrafluoroethylene dispersion for 20 seconds each time, 5 times. It is then hung vertically for 10 minutes to drain and dried under vacuum at 70℃ for 8 hours. Subsequently, it is calcined at 330℃ for 30 minutes and cooled to obtain graded polytetrafluoroethylene modified carbon felt.

[0029] Preferably, the boron-containing substance is selected from borax.

[0030] Preferably, the boron-containing solution is an ethanol solution with a concentration of 0.5M.

[0031] Preferably, the spin coating process is performed at a speed of 300 rpm and the number of cycles is 3.

[0032] Preferably, the inert atmosphere is a nitrogen atmosphere.

[0033] Example 2

[0034] This application discloses a method for preparing a boron-etched modified gas diffusion electrode, the method comprising the following steps: S1. The original carbon felt was placed in ethanol solution and deionized water respectively for ultrasonic cleaning for 10 min. After cleaning, it was dried under vacuum for 6 h to obtain the pretreated carbon felt substrate. S2. The pretreated carbon felt substrate is coated with polytetrafluoroethylene twice and subjected to gradient heat treatment to obtain gradient polytetrafluoroethylene modified carbon felt. S3. Coat one side of the gradient polytetrafluoroethylene modified carbon felt with a solution containing boron, and then spin-coat it at 60°C to form a uniform covering layer. After draining, dry it under vacuum at 70°C for 6 hours to obtain a carbon felt loaded with boron. S4. Under an inert atmosphere, carbon felt loaded with boron-containing material is placed in a tube furnace and calcined at 650°C for 30 minutes. After cooling, a boron-etched modified gas diffusion electrode is obtained.

[0035] Preferably, the pretreated carbon felt substrate is subjected to two polytetrafluoroethylene (PTFE) coatings and gradient heat treatments to obtain gradient PTFE-modified carbon felt, comprising: S2-1. The pretreated carbon felt substrate is suspended in a dip coating machine and immersed in a 20wt% polytetrafluoroethylene dispersion 15 times for 20s each time. It is then hung vertically for 10min to drain and dried under vacuum at 70℃ for 6h. Subsequently, it is calcined at 360℃ for 30min and cooled to obtain a primary polytetrafluoroethylene modified carbon felt. S2-2. The polytetrafluoroethylene modified carbon felt is suspended again in a dip coating machine and immersed in a 10wt% polytetrafluoroethylene dispersion for 20 seconds each time, 5 times. It is then hung vertically for 10 minutes to drain and dried under vacuum at 70℃ for 8 hours. Subsequently, it is calcined at 330℃ for 30 minutes and cooled to obtain graded polytetrafluoroethylene modified carbon felt.

[0036] Preferably, the boron-containing substance is selected from borax.

[0037] Preferably, the boron-containing solution is an ethanol solution with a concentration of 0.5M.

[0038] Preferably, the spin coating process is performed at a speed of 300 rpm and the number of cycles is 3.

[0039] Preferably, the inert atmosphere is a nitrogen atmosphere.

[0040] Comparative Example 1 This comparative example presents a method for preparing a boron-etched modified gas diffusion electrode, the method comprising the following steps: S1. Place the raw carbon felt in ethanol solution and deionized water in sequence, and ultrasonically treat them for 10 minutes in an ultrasonic cleaner to remove surface impurities. After cleaning, place the carbon felt in a vacuum drying oven at 70°C and dry for 6 hours to obtain the pretreated carbon felt substrate.

[0041] S2. The pretreated carbon felt was completely immersed in a polytetrafluoroethylene dispersion with a solid content of 10% for 10 minutes. After soaking, it was removed and hung vertically for 1 minute to remove excess dispersion. Then it was placed in a vacuum drying oven at 70°C for 6 hours. The dried carbon felt was placed in a preheated muffle furnace and calcined at 330°C for 20 minutes. After being removed and allowed to cool naturally, polytetrafluoroethylene modified carbon felt was obtained.

[0042] S3. Immerse one side of the pretreated carbon felt substrate in a 0.5M boric acid ethanol solution and spin-coat it at 60°C with a spin speed of 300 rpm for 3 cycles to form a uniform boron-containing coating layer on the surface of the carbon felt. After treatment, remove the substrate, hang it vertically for 1 minute to drain, and then place it in a vacuum drying oven at 70°C for 6 hours to obtain a carbon felt loaded with boron-containing material.

[0043] S4. Under a nitrogen atmosphere, the carbon felt loaded with boron-containing material is placed in a tube furnace and calcined at 550°C for 30 minutes. After cooling, it is taken out to obtain a boron-etched modified gas diffusion electrode.

[0044] Comparative Example 2 This comparative example presents a method for preparing a boron-etched modified gas diffusion electrode, the method comprising the following steps: S1. Place the raw carbon felt in ethanol solution and deionized water in sequence, and ultrasonically treat them for 10 minutes in an ultrasonic cleaner to remove surface impurities. After cleaning, place the carbon felt in a vacuum drying oven at 70°C and dry for 6 hours to obtain the pretreated carbon felt substrate.

[0045] S2. The pretreated carbon felt is completely immersed in a polytetrafluoroethylene dispersion with a solid content of 20% for 10 minutes, then removed and hung vertically for 1 minute to remove excess dispersion; subsequently, it is dried in a vacuum drying oven at 70°C for 6 hours. The dried carbon felt is placed in a preheated muffle furnace and calcined at 330°C for 20 minutes, then removed and allowed to cool naturally to obtain polytetrafluoroethylene modified carbon felt.

[0046] application The electrodes prepared in Examples 1-3 and Comparative Examples 1-2 were used for electrochemical in-situ hydrogen peroxide production, comprising the following steps: 1. Construction of the electrode system: The prepared electrode was used as the working electrode; a graphite rod was selected as the counter electrode; and a silver / silver chloride (Ag / AgCl) electrode was used as the reference electrode. 2. Electrolyte and reaction conditions A 50 mM sodium sulfate (Na2SO4) aqueous solution was prepared as the electrolyte, using deionized water. The boron-etched side of the working electrode was placed in contact with the electrolyte, while the unetched side was exposed to air. An external potential of -1 V was applied to the three-electrode system in constant potential mode.

[0047] 3. Hydrogen peroxide detection Samples were taken periodically during the reaction, and the hydrogen peroxide produced was quantitatively detected using iodometric titration. For example... Figure 5 As shown, the absorbance was measured at a wavelength of 352 nm using a UV-Vis spectrophotometer, and the hydrogen peroxide concentration was calculated based on a pre-established standard curve.

[0048] Performance testing The performance of the electrodes prepared in Examples 1-3 and Comparative Examples 1-2 was tested, and the results are as follows: like Figure 1 , Figure 2 and Figure 3 As shown, the electrode of Example 1, after modification with polytetrafluoroethylene (PTFE), boric acid loading, and synergistic boron etching, exhibits excellent electrochemical performance, stably and efficiently generating hydrogen peroxide with the highest yield. Scanning electron microscopy (SEM) characterization reveals that the boron etching treatment creates abundant defect structures and irregular cracks on the electrode surface. This multi-level microstructure significantly expands the exposed area of ​​the reaction interface, providing more accessible active sites for the oxygen reduction reaction. Figure 4As shown, Fourier transform infrared spectroscopy (FTIR) analysis indicates that oxygen-containing functional groups such as hydroxyl (-OH) were successfully introduced into the electrode surface after boron etching, which improved the hydrophilicity and wettability of the reaction side, facilitating electrolyte wetting and reactant contact; simultaneously, at 1500 cm⁻¹... -1 Left and right and 900-1100cm -1 The newly added absorption peaks in the range confirm the formation of boron-oxygen functional structures dominated by BO and BOC on the surface of the carbon material, accompanied by a small contribution from boron-fluorine coordination structures. These boron-based functional groups effectively regulate the electronic structure and surface chemical environment of the carbon material, thereby enhancing its ability to generate and maintain hydrogen peroxide.

[0049] In Example 2, further increasing the boron etching temperature actually decreased the hydrogen peroxide yield. This phenomenon stems from the etching temperature exceeding the critical pyrolysis threshold of PTFE, leading to a large amount of PTFE pyrolysis and volatilization, which disrupts the original hydrophobic interface structure of the electrode. This makes it easier for the electrolyte to penetrate the electrode, hindering the continuous mass transfer of gaseous oxygen, weakening the stability of the gas-liquid-solid three-phase interface, and ultimately resulting in a significant reduction in hydrogen peroxide generation efficiency.

[0050] In Comparative Example 1, after reducing the concentration of the PTFE modified dispersion, even with the retention of boric acid loading and boron etching treatment, the stability of the gas-liquid-solid three-phase interface on the electrode surface decreased significantly due to insufficient hydrophobic components. The oxygen mass transfer channels were easily destroyed by the electrolyte, resulting in a significant deterioration of the overall electrochemical performance.

[0051] Comparative Example 2, which omits the boron loading and boron etching steps, retains PTFE modification and maintains a certain oxygen mass transfer capacity, but its electrochemical performance is significantly lower than that of Example 1. The core reason is that boron etching can construct multi-level defects, irregular cracks, and boron-based functional groups such as BO and BOC on the surface of carbon materials, significantly improving the electrode's hydrophilicity, reaction accessibility, and electrochemical activity; while electrodes lacking this treatment cannot form the aforementioned key microstructures and chemical environments, resulting in insufficient active sites and limited oxygen reduction reaction efficiency.

[0052] like Figure 6 As shown, the concentration changes of hydrogen peroxide generated by the four electrodes within 120 minutes are as follows: Example 1 showed the best performance, with a concentration of approximately 65 mg / L at 120 minutes, exhibiting the fastest and most stable growth rate throughout; Example 2 was second, with a concentration of approximately 47 mg / L at 120 minutes; Comparative Example 1 had a concentration of approximately 30 mg / L; while Comparative Example 2 had the lowest generation efficiency, with only approximately 5 mg / L at 120 minutes. All samples exhibited the typical electrochemical synthesis characteristics of rapid concentration growth in the first 60 minutes followed by a slowdown in the growth rate, and Example 1 maintained its leading position throughout the entire reaction cycle, clearly demonstrating the significant impact of different electrode preparation processes on hydrogen peroxide generation efficiency.

[0053] This application provides a method for preparing a boron-etched modified gas diffusion electrode. During heating, the boron-containing precursor undergoes dehydration and condensation reactions, preferentially forming boron oxides (B₂O₃ or BO₂) with Lewis acid properties. x These boron-oxygen species can first interact with the surface of polytetrafluoroethylene (PTFE), and then undergo coordination or substitution reactions with the active fluorinated groups generated during the thermal decomposition of PTFE to form unstable [BO] compounds. x F y ] n A transition state-like structure is constructed. The formation of the transition state weakens the original CF bond binding energy, thereby inducing selective defluorination etching on the carbon matrix surface, accompanied by local carbon framework rearrangement and defect generation. Furthermore, the introduction of BO, BOC, and hydroxyl functional structures selectively weakens the original local hydrophobicity of PTFE, thus constructing a functional gradient structure with both hydrophobic gas and hydrophilic reactive sides along the electrode thickness direction. This structure is beneficial for stabilizing the gas-liquid-solid three-phase interface and promoting oxygen enrichment and mass transfer at the reaction interface, ultimately guiding the oxygen reduction reaction preferentially along a two-electron pathway, achieving highly selective in-situ generation of hydrogen peroxide.

[0054] 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 method for preparing a boron-etched modified gas diffusion electrode, characterized in that, The preparation method includes the following steps: S1. The original carbon felt is placed in ethanol solution and deionized water for ultrasonic cleaning in turn. After cleaning, it is dried under vacuum to obtain the pretreated carbon felt substrate. S2. The pretreated carbon felt substrate is subjected to two polytetrafluoroethylene coatings and gradient heat treatments to obtain gradient polytetrafluoroethylene modified carbon felt. S3. Coat one side of the gradient polytetrafluoroethylene modified carbon felt with a solution containing boron, then spin-coat it to form a uniform covering layer, drain it, and dry it under vacuum to obtain a carbon felt loaded with boron. S4. Under an inert atmosphere, the carbon felt loaded with boron-containing material is placed in a tube furnace and calcined at 450-550°C for 20-40 minutes. After cooling, the boron-etched modified gas diffusion electrode is obtained.

2. The method for preparing a boron-etched modified gas diffusion electrode according to claim 1, characterized in that, The pretreated carbon felt substrate is subjected to two polytetrafluoroethylene (PTFE) coatings and gradient heat treatments to obtain gradient PTFE-modified carbon felt, comprising: S2-1. The pretreated carbon felt substrate is suspended in a dip coating machine and dipped in a 15-25wt% polytetrafluoroethylene dispersion. After being vertically suspended and drained, it is vacuum dried and then calcined at 350-370℃ and cooled to obtain a primary polytetrafluoroethylene modified carbon felt. S2-2. The polytetrafluoroethylene modified carbon felt is suspended again in a dip coating machine and dipped again in a 5-15wt% polytetrafluoroethylene dispersion. After being hung vertically to drain, it is vacuum dried and then calcined at 320-340℃. After cooling, a gradient polytetrafluoroethylene modified carbon felt is obtained.

3. The method for preparing a boron-etched modified gas diffusion electrode according to claim 1, characterized in that, The boron-containing substance is selected from at least one of boric acid, borax, or boron oxide.

4. The method for preparing a boron-etched modified gas diffusion electrode according to claim 1, characterized in that, The boron-containing solution is an ethanol solution with a concentration of 0.1-1.0M.

5. The method for preparing a boron-etched modified gas diffusion electrode according to claim 1, characterized in that, The spin coating process is performed at a speed of 200-400 rpm, and the number of cycles is 2-4.

6. The method for preparing a boron-etched modified gas diffusion electrode according to claim 1, characterized in that, The inert atmosphere is a nitrogen or argon atmosphere.

7. A boron-etched modified gas diffusion electrode, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. The application of the boron-etched modified gas diffusion electrode as described in claim 7 in the electrochemical in-situ generation of hydrogen peroxide.

9. The application according to claim 8, characterized in that, The boron-etched side of the gas diffusion electrode is brought into contact with the electrolyte, while the untreated side is exposed to air or an oxygen atmosphere. A constant potential electrolysis is performed in the electrochemical system by applying an external potential of -0.6V to -1.2V.

10. The application according to claim 9, characterized in that, The electrolyte is a sodium sulfate aqueous solution with a concentration of 10-100 mM.

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