ELECTRODE AND PREPARATION METHOD AND USE THEREOF

Description

CROSS REFERENCE TO RELATED APPLICATION

This patent application claims the benefit and priority of Chinese Patent Application No. 2024108055716 filed with the China National Intellectual Property Administration on Jun. 21, 2024, the disclosure of which is incorporated by reference herein in its entirety as part of the present application.

TECHNICAL FIELD

The present disclosure belongs to the technical field of electrocatalysis, and specifically relates to an electrode and a preparation method and use thereof.

BACKGROUND

Hydrogen peroxide (H₂O₂), as an important chemical raw material, is widely used in industries such as chemical industry (organic synthesis, pulp or textile bleaching, or the like), wastewater treatment, energy conversion, and medical disinfection. The traditional anthraquinone process for preparing H₂O₂ has disadvantages such as high energy consumption, large organic solvent loss, and potential safety hazards in transportation and storage. Electrocatalytic oxygen reduction reaction process for preparing H₂O₂ is based on a two-electron (2e⁻ ORR) oxygen reduction reaction at a cathode. Compared with the traditional anthraquinone process, the electrocatalytic oxygen reduction reaction process has many advantages, such as an eco-friendly and safe synthesis route, no generation of organic by-products, possible in-situ production, and easy operations. Therefore, the electrocatalytic oxygen reduction reaction process is a desirable process for industrial preparation of H₂O₂.

In the Chinese patent CN116081579A, Se defect-rich cubic-phase cobalt selenide (c-CoSe₂) is adopted as a cathode material. In the Chinese patent CN115786962A, a metal/non-metal-co-doped amorphous carbon material is prepared with molybdenum and fluorine and then used to synthesize a cathode material, and the synthesized cathode material could promote the electrocatalytic oxygen reduction for preparing H₂O₂ to some extent. However, the industrial electrochemical preparation of H₂O₂ is usually conducted in a membrane electrolyzer, where a cathode chamber is separated from an anode chamber through an ion exchange membrane and O₂ is reduced into H₂O₂ by electrochemical means (O₂+2H⁺+2e⁻→H₂O₂) in the cathode chamber. In such a system, it is necessary to use an ion exchange membrane because H₂O₂ is very easily oxidized into O₂ (H₂O₂→O₂+2H⁺+2e⁻) at an anode. However, the ion exchange membranes are inherently expensive, and are susceptible to microbial contamination or chemical attack in a complicated water environment, resulting in a high cost for regular replacement of the ion exchange membranes in practical applications.

Although a membrane-free electrolyzer (such as the electro-Fenton system) can be adopted for the electrocatalytic production of H₂O₂ in some applications, due to the fact that a cathode and an anode are arranged in the same chamber, many side reactions occur to cause a very low H₂O₂ yield, such as H₂O₂ oxidation (H₂O₂→O₂+H⁺+2e⁻) at an anode, H₂O₂ reduction (H₂O₂+2H⁺+2e⁻→H₂O) at a cathode, and H₂O₂ decomposition (2H₂O₂→2H₂O+O₂). Therefore, how to maintain a high H₂O₂ concentration generated in a system while avoiding the use of an ion exchange membrane in a membrane-free electrolyzer is very important for the large-scale application of the technology to prepare H₂O₂ through electrocatalytic oxygen reduction.

SUMMARY

In order to solve the problems in the prior art, the present disclosure provides an electrode and a preparation method and use thereof. The electrode provided by the present disclosure could achieve the preparation of high-concentration H₂O₂ in a membrane-free electrolyzer.

To achieve the above objects, the present disclosure provides the following technical solutions.

The present disclosure provides an electrode, including a modified anode and a modified cathode, where the modified anode includes an anode and a first hydrophobic porous layer coated on a surface of the anode, and the modified cathode includes a current collector, a carbon catalysis layer attached to a surface of the current collector, and a second hydrophobic porous layer attached to a surface of the carbon catalysis layer.

A material of the first hydrophobic porous layer and a material of the second hydrophobic porous layer are independently one or more selected from the group consisting of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polypropylene (PP), polyethylene (PE), and polysulfone (PSF).

In some embodiments, raw materials for preparing the carbon catalysis layer include a binder and a carbon material, the carbon material including one or more selected from the group consisting of carbon black, activated carbon, and graphene and the binder including one or more selected from the group consisting of a PTFE binder, a PVDF binder, a PAN binder, a PMMA binder, a PP binder, a PE binder, and a PSF binder.

In some embodiments, a mass ratio of the carbon material to the binder is in a range of 1-5:1.

In some embodiments, the first hydrophobic porous layer has a thickness independently of 8 μm to 20 μm and a pore size of 0.1 μm to 10 μm, and the second hydrophobic porous layer has a thickness independently of 12 μm.

In some embodiments, the carbon catalysis layer has a thickness of 0.01 mm to 1 mm.

The present disclosure also provides a method for preparing the electrode described above, including preparing the modified anode by a process including subjecting a solution of a first hydrophobic polymer material to first dispersion and stabilization in a first organic solvent to obtain a first diluted hydrophobic polymer solution, loading the first diluted hydrophobic polymer solution to the surface of the anode to obtain a first hydrophobic porous layer-loaded anode, where the loading is conducted under first heating to remove the first organic solvent; and subjecting the first hydrophobic porous layer-loaded anode to first heat treatment to obtain the modified anode.

The method further includes preparing the modified cathode by a process including subjecting the binder and the carbon material to second dispersion and stabilization in a second organic solvent to obtain a carbon catalysis mixture, loading the carbon catalysis mixture to the surface of the current collector to obtain a carbon catalysis layer-loaded cathode, where the loading is conducted under second heating to remove the second organic solvent, subjecting the carbon catalysis layer-loaded cathode to second heat treatment to obtain a carbon material air cathode; and subjecting a solution of a second hydrophobic polymer material to third dispersion and stabilization in a third organic solvent to obtain a second diluted hydrophobic polymer solution; and loading the second diluted hydrophobic polymer solution to a surface of the carbon material air cathode to obtain the modified cathode, where the loading is conducted under third heating to remove the third organic solvent.

In some embodiments, the first organic solvent, the second organic solvent, and the third organic solvent are independently one or more selected from the group consisting of absolute ethanol, dimethylacetamide (DMAc), dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and sulfolane (MSDS).

In some embodiments, the first heat treatment is conducted at a temperature of 100° C. to 400° C. for 10 min to 60 min.

In some embodiments, the second heat treatment is conducted at a temperature of 60° C. to 400° C. for 10 min to 60 min.

The present disclosure also provides use of the electrode described above or the electrode prepared by the method described above in synthesis of H₂O₂ by an in-situ electrocatalytic oxygen reduction reaction in a membrane-free electrolyzer.

The present disclosure provides an electrode, including a modified anode or a modified cathode, where the modified anode includes an anode and a first hydrophobic porous layer coated on a surface of the anode; the modified cathode includes a current collector, a carbon catalysis layer attached to a surface of the current collector, and a second hydrophobic porous layer attached to a surface of the carbon catalysis layer; and a material of the first hydrophobic porous layer and a material of the second hydrophobic porous layer are independently one or more selected from the group consisting of PTFE, PVDF, PAN, PMMA, PP, PE, and PSF. In the present disclosure, a uniform hydrophobic porous layer is formed with a hydrophobic polymer material on a surface of the electrode, which reduces the anodic oxidation of H₂O₂ into oxygen and the further reduction of H₂O₂ into water at a cathode without affecting the cathodic oxygen reduction to produce H₂O₂. Therefore, compared with an ion exchange membrane-containing electrolyzer adopted in the traditional electrochemical preparation of the H₂O₂, the present disclosure could reduce use of an ion exchange membrane in the electrochemical preparation of the H₂O₂, does not require additional reagents, and could reduce the reaction cost and the system energy consumption while allowing the preparation of high-concentration H₂O₂. In addition, in the present disclosure, because the uniform hydrophobic porous layer is formed on the surface of the electrode, a stable solid/liquid/gas three-phase interface could be formed through hydrophobicity and a uniform hydrophobic porous structure on the surface of the electrode, and bubbles generated at an electrode interface after application of a voltage, which could reduce the occurrence of side reactions at the electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic structural diagram of the modified anode provided by the present disclosure;

FIG. 2 shows a schematic structural diagram of the modified cathode provided by the present disclosure;

FIG. 3A shows a scanning electron microscopy (SEM) characterization result of the ordinary commercial anode provided in Comparative Example 1 of the present disclosure;

FIG. 3B shows an SEM characterization result of the hydrophobic porous anode in Example 1 of the present disclosure;

FIG. 4A shows an SEM characterization result of the ordinary carbon material air cathode provided in Comparative Example 2 of the present disclosure;

FIG. 4B shows an SEM characterization result of the hydrophobic porous carbon material air cathode in Example 2 of the present disclosure;

FIG. 5 shows a schematic comparison diagram illustrating a concentration change as a function of a current density when the hydrophobic porous electrode composed of the anode and cathode provided in Examples 1 and 2 of the present disclosure and the untreated electrode composed of the anode and cathode provided in Comparative Examples 1 and 2 are used for the preparation of H₂O₂ by electrocatalytic oxygen reduction in a membrane-free electrolyzer;

FIG. 6A shows a schematic comparison diagram illustrating a voltage change when the hydrophobic porous electrode composed of the anode and cathode provided in Examples 1 and 2 of the present disclosure and the untreated electrode composed of the anode and cathode provided in Comparative Examples 1 and 2 work for a long time in a membrane-free electrolyzer; and

FIG. 6B shows a schematic comparison diagram illustrating a concentration change of H₂O₂ prepared when the hydrophobic porous electrode composed of the anode and cathode provided in Examples 1 and 2 and the untreated electrode composed of the anode and cathode provided in Comparative Examples 1 and 2 work for a long time in the membrane-free electrolyzer.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present disclosure provides an electrode, including a modified anode and a modified cathode, where the modified anode includes an anode and a first hydrophobic porous layer coated on a surface of the anode; the modified cathode includes a current collector, a carbon catalysis layer attached to a surface of the current collector, and a second hydrophobic porous layer attached to a surface of the carbon catalysis layer; and

• • a material of the first hydrophobic porous layer and a material of the second hydrophobic porous layer are independently one or more selected from the group consisting of PTFE, PVDF, PAN, PMMA, PP, PE, and PSF.

In the present disclosure, an electrode includes a modified anode or a modified cathode.

In the present disclosure, the modified anode includes an anode and a first hydrophobic porous layer coated on a surface of the anode.

In some embodiments of the present disclosure, the anode is a commercially-available product, and specifically, the anode is one selected from the group consisting of a coated titanium anode (DSA), a fluorine-doped tin oxide conductive glass (FTO), and a graphite plate.

In some embodiments of the present disclosure, a material of the first hydrophobic porous layer is one or more selected from the group consisting of PTFE, PVDF, PAN, PMMA, PP, PE, and PSF, and preferably the PTFE. In some embodiments of the present disclosure, the first hydrophobic porous layer has a thickness of 8 μm to 20 μm, and preferably 12 μm to 16 μm. In some embodiments of the present disclosure, the first hydrophobic porous layer has a pore size of 0.1 μm to 10 μm, and preferably 0.5 μm to 6 μm.

FIG. 1 shows a schematic structural diagram of the modified anode provided by the present disclosure. It can be seen from FIG. 1 that the modified anode includes the anode and the first hydrophobic porous layer coated on the surface of the anode.

In the present disclosure, the modified cathode includes a current collector, a carbon catalysis layer attached to a surface of the current collector, and a second hydrophobic porous layer attached to a surface of the carbon catalysis layer.

In some embodiments of the present disclosure, the current collector includes one selected from the group consisting of a carbon paper, a carbon felt, and a carbon cloth, and is preferably the carbon paper.

In some embodiments of the present disclosure, raw materials for preparing the carbon catalysis layer include a binder and a carbon material. In some embodiments of the present disclosure, the carbon material includes one or more selected from the group consisting of carbon black, activated carbon, and graphene, and is preferably the carbon black. In some embodiments of the present disclosure, the binder includes one or more selected from the group consisting of a PTFE binder, a PVDF binder, a PAN binder, a PMMA binder, a PP binder, a PE binder, and a PSF binder, and is preferably a PTFE binder.

In some embodiments of the present disclosure, the carbon catalysis layer has a thickness of 0.01 mm to 1 mm, and preferably 0.08 mm to 0.1 mm.

In some embodiments of the present disclosure, a material of the second hydrophobic porous layer is one or more selected from the group consisting of PTFE, PVDF, PAN, PMMA, PP, PE, and PSF, and preferably the PTFE.

In some embodiments of the present disclosure, the second hydrophobic porous layer has a thickness of 12 μm.

FIG. 2 shows a schematic structural diagram of the modified cathode provided by the present disclosure. It can be seen from FIG. 2 that the modified cathode includes the current collector, the carbon catalysis layer attached to the surface of the current collector, and the second hydrophobic porous layer attached to the surface of the carbon catalysis layer.

The present disclosure also provides a method for preparing the electrode described above, including: preparing the modified anode and preparing the modified cathode.

In the present disclosure, preparing the modified anode includes the steps of:

• • subjecting a solution of a first hydrophobic polymer material to first dispersion and stabilization in a first organic solvent to obtain a first diluted hydrophobic polymer solution.
  • loading the first diluted hydrophobic polymer solution to the surface of the anode to obtain a first hydrophobic porous layer-loaded anode, where the loading is conducted under first heating to remove the first organic solvent; and
  • subjecting the first hydrophobic porous layer-loaded anode to first heat treatment to obtain the modified anode.

In the present disclosure, a solution of a first hydrophobic polymer material is subjected to first dispersion and stabilization in a first organic solvent to obtain a first diluted hydrophobic polymer solution.

In some embodiments of the present disclosure, the first organic solvent includes one or more selected from the group consisting of absolute ethanol, DMAc, DME, DMSO, and MSDS, and is preferably the absolute ethanol. In some embodiments of the present disclosure, the solution of the first hydrophobic polymer material has a mass concentration of 0.05% to 0.2%, and preferably 0.1% to 0.15%.

In some embodiments of the present disclosure, the first dispersion and stabilization is conducted for 5 min to 60 min, and preferably 10 min to 40 min.

In the present disclosure, after the first diluted hydrophobic polymer solution is obtained, the first diluted hydrophobic polymer solution is loaded to the surface of the anode to obtain a first hydrophobic porous layer-loaded anode, where loading is conducted under first heating to remove the first organic solvent.

In some embodiments of the present disclosure, a way for the loading includes coating or impregnation, and a way for the coating is spray-coating, spin-coating, or roll-coating

In some embodiments of the present disclosure, the first heating is conducted as follows: during the loading, a heating plate is placed below the anode to evaporate the first organic solvent, where a temperature of the heating plate is in a range of 50° C. to 100° C., and preferably in a range of 60° C. to 80° C.

In the present disclosure, after the first hydrophobic porous layer-loaded anode is obtained, the first hydrophobic porous layer-loaded anode is subjected to first heat treatment to obtain the modified anode.

In some embodiments of the present disclosure, the first heat treatment is conducted at a temperature of 100° C. to 400° C., and preferably 200° C. to 350° C. In some embodiments of the present disclosure, the first heat treatment is conducted for 10 min to 60 min, and preferably 20 min to 50 min.

In the present disclosure, preparing the modified cathode includes the steps of:

• • subjecting the binder and the carbon material to second dispersion and stabilization in a second organic solvent to obtain a carbon catalysis mixture;
  • loading the carbon catalysis mixture to the surface of the current collector to obtain a carbon catalysis layer-loaded cathode, where the loading is conducted under second heating to remove the second organic solvent;
  • subjecting the carbon catalysis layer-loaded cathode to second heat treatment to obtain a carbon material air cathode; and
  • subjecting a solution of a second hydrophobic polymer material to third dispersion and stabilization in a third organic solvent to obtain a second diluted hydrophobic polymer solution; and loading the second diluted hydrophobic polymer solution to a surface of the carbon material air cathode to obtain the modified cathode, where the loading is conducted under third heating to remove the third organic solvent.

In the present disclosure, the binder and the carbon material are subjected to second dispersion and stabilization in a second organic solvent to obtain a carbon catalysis mixture.

In some embodiments of the present disclosure, the second organic solvent and a time of the second dispersion and stabilization are the same as the first organic solvent and the time of the first dispersion and stabilization, which are not repeated here.

In the present disclosure, after the carbon catalysis mixture is obtained, the carbon catalysis mixture is loaded to the surface of the current collector to obtain a carbon catalysis layer-loaded cathode, where loading is conducted under second heating to remove the second organic solvent.

In the present disclosure, a way for the loading is the same as the way for the loading to prepare the modified anode, which is not be repeated here. In some embodiments of the present disclosure, the second heating is conducted as follows: during the loading, a heating plate is placed below the current collector for heating, where a temperature of the heating plate is 60° C. to 100° C., and preferably 60° C. to 80° C.

In the present disclosure, after the carbon catalysis layer-loaded cathode is obtained, the carbon catalysis layer-loaded cathode is subjected to second heat treatment to obtain a carbon material air cathode.

In some embodiments of the present disclosure, the second heat treatment is conducted at a temperature of 60° C. to 400° C., and preferably 200° C. to 350° C. In some embodiments of the present disclosure, the second heat treatment is conducted for 10 min to 60 min, and preferably 20 min to 50 min.

In the present disclosure, a solution of a second hydrophobic polymer material is subjected to third dispersion and stabilization in a third organic solvent to obtain a second diluted hydrophobic polymer solution, and the second diluted hydrophobic polymer solution is loaded to a surface of the carbon material air cathode to obtain the modified cathode, where loading is conducted under third heating to remove the third organic solvent.

In some embodiments of the present disclosure, the solution of the second hydrophobic polymer material, a time of the third dispersion and stabilization, and the third organic solvent are the same as the solution of the first hydrophobic polymer material, the time of the first dispersion and stabilization, and the first organic solvent, respectively, which are not repeated here. In some embodiments of the present disclosure, a way for the loading of the second diluted hydrophobic polymer solution is the same as the way for the loading of the first diluted hydrophobic polymer solution, which is not repeated here.

In the method of the present disclosure, cheap hydrophobic porous materials and easily-available carbon materials are adopted as raw materials to prepare the modified cathode and the modified anode, which involves a simple preparation process, is easy to implement and control, and is conducive to large-scale production.

In summary, the present disclosure improves a configuration of the electrode on the one hand and optimizes a composition of the electrode on the other hand to develop a hydrophobic porous electrode pair (including a cathode and an anode) with a low cost, a simple process, and excellent performance, such that the electrode could achieve an ability to prepare H₂O₂ efficiently and stably in a membrane-free electrolyzer.

The present disclosure also provides use of the electrode described above or the electrode prepared by the method described above in synthesis of H₂O₂ by an in-situ electrocatalytic oxygen reduction reaction in a membrane-free electrolyzer.

In some embodiments of the present disclosure, the present disclosure also provides a method for synthesizing H₂O₂ through an in-situ electrocatalytic oxygen reduction reaction in a membrane-free electrolyzer, including the following step:

• • using the modified anode as an anode of the membrane-free electrolyzer and the modified cathode as a cathode of the membrane-free electrolyzer, subjecting an electrolyte solution to electrolysis in a resulting system under an external power supply.

In the present disclosure, the electrolyte solution is one or more selected from the group consisting of a sodium sulfate solution, a sodium chloride solution, a sodium perchlorate solution, phosphate buffered saline (PBS), a sulfuric acid solution, and a sodium hydroxide solution. In some embodiments of the present disclosure, the electrolyte solution has a concentration of 10 mM to 2,000 mM, and preferably 50 mM to 1,000 mM.

In some embodiments of the present disclosure, the electrolysis is conducted at a current density of 10 mA/cm² to 100 mA/cm², and preferably 20 mA/cm² to 40 mA/cm². In some embodiments of the present disclosure, the electrolysis is conducted for 5 min to 6,000 min, and preferably 30 min to 2,000 min.

In some embodiments of the present disclosure, a H₂O₂ solution produced after the electrolysis has a concentration of 4 g/L to 10 g/L, and preferably 7 g/L to 10 g/L.

The traditional electrochemical methods for preparing H₂O₂ mostly adopt an ion exchange membrane-containing electrolyzer to avoid anodic oxidation of the H₂O₂. In the present disclosure, a uniform hydrophobic porous layer is formed with a hydrophobic polymer material on a surface of an electrode, which reduces the anodic oxidation of the H₂O₂ into oxygen and the further reduction of the H₂O₂ into water at a cathode without affecting the cathodic oxygen reduction to produce the H₂O₂. Therefore, compared with the ion exchange membrane-containing electrolyzer adopted in the traditional electrochemical preparation of the H₂O₂, the present disclosure could reduce use of an ion exchange membrane in the electrochemical preparation of H₂O₂, and could reduce the reaction cost and the system energy consumption while allowing the preparation of high-concentration H₂O₂. The use of the modified anode and the modified cathode prepared by the present disclosure for in-situ electrocatalytic synthesis of the H₂O₂ in a membrane-free electrolyzer provides a research idea and a theoretical support for the development of a promising electrocatalytic system.

The technical solutions provided by the present disclosure are described in detail below with reference to examples, but these examples should not be understood as limiting the scope of the present disclosure.

Example 1

Through an Ultrasonic cell disruptor, 11.34 mg of a PTFE solution with a mass concentration of 60% was stably dispersed in 10 mL of absolute ethanol for 10 min to obtain a diluted PTFE solution.

A commercial DSA with a diameter of 3.8 cm was cleaned with pure water and dried to obtain a cleaned commercial DSA anode. The diluted PTFE solution was spray-coated on the cleaned commercial DSA anode to obtain a coated anode. During spray-coating, a heating plate was placed below the cleaned commercial DSA anode and kept at 80° C. to evaporate the ethanol solvent. Finally, the coated anode was heated in a muffle furnace at 330° C. for 30 min to obtain a modified anode, which was denoted as a hydrophobic porous anode. A hydrophobic porous layer in the modified anode of Example 1 had a thickness of 16 μm.

Comparative Example 1

A commercial DSA anode with a diameter of 3.8 cm was cleaned with pure water, dried, and heated in a muffle furnace at 330° C. for 30 min to obtain the commercial DSA anode in Comparative Example 1.

Example 2

Through an Ultrasonic cell disruptor, 11.34 mg of a PTFE solution with a mass concentration of 60% was stably dispersed in 10 mL of absolute ethanol for 10 min to obtain a diluted PTFE solution.

A carbon paper with a diameter of 3.8 cm was cleaned with pure water and dried to obtain a cleaned carbon paper. 45.36 mg of a graphene powder and 15.12 mg of a PTFE binder (a 60 wt % PTFE solution) were stably dispersed in 10 mL of absolute ethanol for 20 min to obtain a carbon catalysis mixture.

The carbon catalysis mixture was evenly spray-coated on the cleaned carbon paper by a spray gun to obtain a graphene-loaded carbon paper. During spray-coating, a heating plate was placed below the cleaned carbon paper and kept at 80° C. to evaporate the ethanol solvent. Then, the graphene-loaded carbon paper was heated in a muffle furnace at 330° C. for 30 min to obtain a carbon black air cathode. Finally, the diluted PTFE solution was spray-coated on the carbon black air cathode to obtain a modified cathode, which was denoted as a hydrophobic porous carbon material air cathode. During spray-coating, the heating plate was placed below the carbon black air cathode and kept at 80° C. to evaporate the ethanol solvent.

In the modified cathode of Example 2, a hydrophobic porous layer had a thickness of 12 μm and a carbon catalysis layer had a thickness of 0.1 mm.

Comparative Example 2

A carbon paper with a diameter of 3.8 cm was cleaned with pure water and dried to obtain a cleaned carbon paper. 45.36 mg of a graphene powder and 15.12 mg of a PTFE binder were stably dispersed in 10 mL of absolute ethanol for 20 min to obtain a carbon catalysis mixture. The carbon catalysis mixture was evenly spray-coated on the cleaned carbon paper by a spray gun to obtain a graphene-loaded carbon paper. During the spray-coating, a heating plate was placed below the cleaned carbon paper and kept at 80° C. to evaporate the ethanol solvent.

Then, the graphene-loaded carbon paper was heated in a muffle furnace at 330° C. for 30 min to obtain an ordinary carbon material air cathode in Comparative Example 2.

Use Example 1

In a 100 mM Na₂SO₄ solution, the hydrophobic porous anode prepared in Example 1 was adopted as an anode and the hydrophobic porous carbon material air cathode prepared in Example 2 was adopted as a cathode to establish a gas diffusion electrode system. The gas diffusion electrode system was powered by an external power supply, and in a constant current mode. Electrolysis was conducted for 5 h at each of the constant currents of 70 mA, 140 mA, 210 mA, 280 mA, and 350 mA. An H₂O₂ concentration was determined by potassium titanium oxalate spectrophotometry.

Use Example 2

In a 100 mM Na₂SO₄ solution, the hydrophobic porous anode prepared in Example 1 was adopted as an anode and the hydrophobic porous carbon material air cathode prepared in Example 2 was adopted as a cathode to establish a gas diffusion electrode system. The gas diffusion electrode system was powered by an external power supply, and in a constant current mode. Electrolysis was conducted at a constant current of 140 mA for 50 h, during which electrolyte was changed every 5 h. An H₂O₂ concentration was determined by potassium titanium oxalate spectrophotometry, and a run-time reaction voltage was recorded in real time throughout the entire running process.

Experimental results and analysis were as follows:

FIG. 3A shows an SEM characterization result of the ordinary commercial anode provided in Comparative Example 1 of the present disclosure, and FIG. 3B shows an SEM characterization result of the hydrophobic porous anode in Example 1 of the present disclosure. It can be seen from FIG. 3A-3B that cracks appear on a surface of the ordinary commercial anode, and after a hydrophobic porous coating is applied, the cracks are evenly covered by the interconnected porous structure.

FIG. 4A shows an SEM characterization result of the ordinary carbon material air cathode provided in Comparative Example 2 of the present disclosure, and FIG. 4B shows an SEM characterization result of the hydrophobic porous carbon material air cathode provided in Example 2 of the present disclosure. It can be seen from FIG. 4A-4B that a surface of the ordinary carbon material air cathode has a large pore structure, and after the hydrophobic porous coating is applied, pores in the carbon material are reduced, resulting in a relatively-uniform pore size.

In FIG. 5, the gray columnar part is a current density-concentration change diagram when the hydrophobic porous electrode composed of the anode and cathode provided in Examples 1 and 2 are used in a membrane-free electrolyzer to produce H₂O₂. It can be seen from FIG. 5 that, at a current density of 40 mA/cm², a H₂O₂ yield is 10 g/L that is 10 times a H₂O₂ yield when an electrode without a hydrophobic porous layer is adopted, indicating that the hydrophobic porous electrode can be used in the field of electrochemical synthesis of H₂O₂.

FIG. 6A shows a voltage diagram when the hydrophobic porous electrode composed of the anode and cathode provided in Examples 1 and 2 work for a long time in a membrane-free electrolyzer, and FIG. 6B shows a time-concentration change diagram when the hydrophobic porous electrode composed of the anode and cathode provided in Examples 1 and 2 are used to produce H₂O₂. It can be seen from FIGS. 6A-6B that, after 50 h of electrolysis at a constant current density of 20 mA/cm², a H₂O₂ yield is constantly 7 g/L, indicating that the hydrophobic porous electrode can be used in the field of electrocatalytic oxygen reduction to synthesize H₂O₂.

Although the present disclosure is described in detail in conjunction with the foregoing embodiments, they are only a part of, not all of, the embodiments of the present disclosure. Other embodiments can be obtained based on these embodiments without creative efforts, and all of these embodiments shall fall within the scope of the present disclosure.