Gas diffusion electrode with ordered catalyst layer structure, preparation method of gas diffusion electrode, self-breathing type reaction galvanic pile and application of self-breathing type reaction galvanic pile

Abstract

The invention discloses a gas diffusion electrode with an ordered catalyst layer structure, a preparation method of the gas diffusion electrode, a self-breathing type reaction galvanic pile and application of the self-breathing type reaction galvanic pile, the gas diffusion electrode capable of self-breathing is constructed by forming the ordered catalyst layer structure with three layers of wettability gradients and two layers of pore structure gradients, and the self-breathing type reaction galvanic pile is formed through an open structure. Oxygen is supplied depending on natural diffusion of air, additional gas supply and pressurization systems are not needed, the energy consumption and the size of the system can be greatly reduced while the oxygen reduction reaction is realized, in addition, a self-breathing overflowing type reaction galvanic pile is designed based on the electrode, and the galvanic pile has the structural characteristics of modularization and stackability, and is suitable for large-scale popularization and application. High-concentration H2O2 can be continuously electrolyzed and synthesized under the condition of no external oxygen supply, series integration of four reactor units is successfully realized through experiments, and a new solution is provided for field preparation and distributed application of hydrogen peroxide.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy materials technology, specifically relating to the design and application of an ordered catalytic layer structure gas diffusion electrode for the electrosynthesis of hydrogen peroxide (H2O2) and a self-breathing reactor. Background Technology

[0002] Hydrogen peroxide (H2O2) is a green oxidant widely used in environmental remediation, pharmaceutical disinfection, food processing, and the electronics industry. Traditional H2O2 production methods mainly use the anthraquinone process, which, although having a mature industrial foundation, suffers from problems such as complex processes, strong dependence on centralized production, and high transportation risks, making it difficult to meet the needs of distributed, small-scale, low-cost in-situ preparation.

[0003] In recent years, the electrosynthesis of H2O2 based on gas diffusion electrodes (GDE) has become an important development direction to replace the anthraquinone process due to its high selectivity, high energy efficiency, and environmental friendliness. In a typical GDE system, oxygen diffuses from the back of the electrode to the catalyst surface to participate in the 2e-electrolysis. - Oxygen reduction reaction (2e) - (ORR) to generate H2O2. However, these electrodes typically rely on external oxygen supply systems, such as gas pumps or pure oxygen gas, which increases energy consumption and system complexity, and also limits the miniaturization and field deployment capabilities of the equipment. Therefore, it is necessary to simplify existing gas supply structures to meet the needs of different scenarios. Studies have shown that, through simple theoretical calculations, it is sufficient to synthesize high concentrations of hydrogen peroxide using only the partial pressure of oxygen in the atmosphere, with a limiting yield reaching 5.37 g / cm³. 2 / h. However, the removal of external gas sources places higher demands on the electrode's resistance to flooding. The pore channels in the catalyst layer are more easily invaded by liquid electrolytes or flooded by electrogenerated liquids, causing flooding at the three-phase interface. This leads to the cathode reaction proceeding to competing side reactions such as hydrogen evolution or four-electron oxygen reduction, which severely restricts the synthesis efficiency of hydrogen peroxide.

[0004] To address the aforementioned issues, this invention proposes an ordered catalytic layer structure gas diffusion electrode and its preparation method, as well as a self-breathing reactor and its application. By arranging a gradient-ordered wetting and porous structure, a droplet self-transport mechanism under gradient surface tension is triggered, effectively mitigating electrolyte intrusion into the catalytic layer and significantly improving the hydrogen peroxide discharge capacity, thus constructing a "self-breathing" gas diffusion electrode. The self-breathing electrode, with its open structure, relies on natural air diffusion for oxygen supply, eliminating the need for additional gas supply and pressurization systems. While achieving the oxygen reduction reaction, it significantly reduces system energy consumption and volume, representing an important direction for promoting the miniaturization, modularization, and stackability of H2O2 electrosynthesis equipment. Furthermore, a self-breathing overcurrent reactor was designed based on this electrode. This reactor features a modular and stackable structure, enabling continuous electrolytic synthesis of high-concentration H2O2 without external oxygen supply. The series integration of four reactor units has been successfully achieved, providing a new solution for the on-site preparation and distributed application of hydrogen peroxide. Summary of the Invention

[0005] The purpose of this invention is to provide an ordered catalytic layer structure gas diffusion electrode and its preparation method, as well as a self-breathing reactor. Under the premise of ensuring that the catalyst activity and selectivity remain unchanged, by controlling the gradient hydrophilicity and hydrophobicity and pore structure in the thickness direction of the catalytic layer, droplets are induced to be transported in a directional manner in the catalytic layer. This solves the problems of easy water flooding of the gas diffusion electrode and discharge of in-situ generated hydrogen peroxide in the self-breathing system, thereby improving the efficiency of hydrogen peroxide electrosynthesis.

[0006] The objective of this invention is achieved through the following technical solution.

[0007] An ordered catalytic layer structure gas diffusion electrode comprises a gradient-structured catalytic layer and a gas diffusion layer. The gradient-structured catalytic layer has three wettability gradients and two pore structure gradients. The gas diffusion layer is a superhydrophobic gas diffusion layer, and its substrate is one or a combination of carbon fiber conductive carbon paper, carbon cloth, carbon felt, or stainless steel mesh. Its preparation method includes the following:

[0008] The first step involves ultrasonically impregnating the substrate of the gas diffusion layer in a polytetrafluoroethylene emulsion, drying and calcining it to obtain a superhydrophobic gas diffusion layer. Further, the mass fraction of the polytetrafluoroethylene emulsion is 5-30%, more preferably 10%, the ultrasonic impregnation time is 20-60 min, more preferably 30 min, and the calcination is performed at 340°C for 1 h.

[0009] The second step involves ultrasonically premixing commercial carbon black particles and isopropanol to obtain a first mixture. Simultaneously, 0.15 ml of 60% polytetrafluoroethylene emulsion is first mixed evenly with 4 ml of deionized water, and then slowly and dropwise added to the first mixture to obtain a first cathode slurry. The first cathode slurry is placed in the slurry tank of a catalyst coating proton exchange membrane (CCM) planar spraying equipment, the spraying parameters are set, and the first cathode slurry is sprayed onto the surface of the gas diffusion layer obtained in the first step. The slurry is then placed in a muffle furnace for calcination to obtain a gas diffusion electrode with a first wettability gradient and a first porous catalytic layer. Furthermore, the ratio of commercial carbon black particles to isopropanol is 1g:30-40ml, more preferably 1g:33ml; the volume ratio of polytetrafluoroethylene emulsion to the first mixture is 1ml:10-20ml, more preferably 1ml:13ml; the spraying process is configured with a slurry pressure of 0.1-0.35bar, an atomization pressure of 2.5-4.5bar, and a spraying pressure of 0.5-1.5bar, more preferably a slurry pressure of 0.25bar, an atomization pressure of 3.5bar, and a spraying pressure of 1bar; the calcination is performed at 327-350℃ for 0.5h-1h, more preferably at 340℃ for 1h.

[0010] The third step involves ultrasonically premixing commercial carbon black particles and isopropanol to obtain a second mixture. Simultaneously, a 60% (w / w) polytetrafluoroethylene (PTFE) emulsion is first mixed evenly with 4 ml of deionized water, and then slowly and dropwise added to the second mixture to obtain a second cathode slurry. The second cathode slurry is placed in the slurry tank of a catalyst coating proton exchange membrane (CCM) planar spraying equipment. Spraying parameters are set, and the vertical distance between the spray gun and the gas diffusion layer and the horizontal spraying spacing are controlled. The slurry is sprayed layer by layer onto the surface of the gas diffusion layer at a constant speed, with a pause of 1–10 minutes (preferably 5 minutes) after each layer is sprayed, and hot air is used for assisted drying to evaporate the hydrophilic surfactant (derived from the PTFE emulsion) in the second cathode slurry until the slurry is completely sprayed. Finally, it is dried at a constant temperature (preferably at 60°C for 12 hours) to obtain a gas diffusion electrode with a second wettability gradient and a second porous catalyst layer. Furthermore, the ratio of the commercial carbon black particles to isopropanol is 1g:30-40ml, more preferably 1g:33ml; the volume ratio of the polytetrafluoroethylene emulsion to the second mixture is 1ml:20-40ml, more preferably 1ml:33ml; the spraying process is configured with a slurry pressure of 0.1-0.35bar, an atomization pressure of 2.5-4.5bar, and a spraying pressure of 0.5-1.5bar, more preferably a slurry pressure of 0.25bar, an atomization pressure of 3.5bar, and a spraying pressure of 1bar; the vertical distance between the spray gun and the gas diffusion layer is controlled to be 5-20cm, more preferably 10cm, and the horizontal spraying spacing is 3-8mm, more preferably 5mm.

[0011] In the fourth step, the gas diffusion electrode with the second-layer wettability gradient and the second-layer pore structure catalytic layer is horizontally placed into a plasma etching machine, and the surface of the catalytic layer is subjected to plasma etching using pure oxygen or air (preferably pure oxygen) as the gas source to obtain a gas diffusion electrode with the third-layer wettability gradient and the second-layer pore structure catalytic layer.

[0012] For the gas diffusion electrode with the third-layer wettability gradient and the second-layer pore structure catalytic layer, both the contact angle and the porosity show discontinuous monotonic changes in the thickness direction of the catalytic layer. From the surface of the catalytic layer to the gas diffusion layer, the contact angles are 15° - 40°, 100° - 130°, and 130° - 160° in sequence, forming a wettability gradient, and the pore structure gradually becomes denser from loose, forming a pore structure gradient.

[0013] A self-breathing electrode is obtained based on the above-mentioned gas diffusion electrode with an ordered catalytic layer structure, which does not require additional oxygen supply and can continuously resist flooding.

[0014] Based on this self-breathing electrode, a self-breathing reaction stack is obtained, which includes two end plates, and a number of modular electrolysis units and an anode conductive plate arranged between the two end plates; each modular electrolysis unit includes, in sequence: a bipolar plate, a self-breathing cathode, a cathode flow channel plate, a cation exchange membrane, an anode, and an anode flow channel plate; the self-breathing cathode uses the above-mentioned gas diffusion electrode with an ordered catalytic layer structure;

[0015] The bipolar plate is formed by fastening an anode current collector plate and a hollowed-out frame for conducting electricity and supporting the self-breathing cathode with bolts. The anode current collector plate is a titanium plate with a platinum coating; one side of the gas diffusion layer of the self-breathing cathode is adhered to the hollowed-out frame so that one side of the gas diffusion layer can be exposed to the atmospheric environment to achieve self-breathing oxygen supply, and the reaction stack does not require additional oxygen supply; a cathode terminal is provided on the bipolar plate for connecting to the negative pole of the power supply.

[0016] Furthermore, the hollowed-out frame is in a "tian" character, "jing" character or honeycomb structure, and the material is carbon, titanium, titanium with a noble metal coating, nickel or graphite.

[0017] The present invention also provides the application of the gas diffusion electrode with an ordered catalytic layer structure in the electro-synthesis of hydrogen peroxide, and a performance comparison is made with the gas diffusion electrode designed with a traditional catalytic layer structure.

[0018] The performance is calculated through the hydrogen peroxide yield and the Faraday efficiency;

[0019] The formula for calculating the hydrogen peroxide yield is:

[0020]

[0021] In the formula, γ is the hydrogen peroxide yield, mmol·cm-2 ·h -1 ; The concentration of hydrogen peroxide produced is expressed in g·L⁻¹. -1 V is the volume of the electrolyte, in L; M is the relative molecular mass of hydrogen peroxide, in g·mol⁻¹ -1 S represents the active area of ​​the gas diffusion electrode reaction, in cm². -1 t represents the reaction time, in hours (h).

[0022] The formula for calculating Faraday efficiency is as follows:

[0023]

[0024] In the formula, FE is the Faraday efficiency; n is the number of reaction electrons, 2; The concentration of hydrogen peroxide produced is expressed in g·L⁻¹. -1 V is the electrolyte volume, in L; S is the active surface area of ​​the gas diffusion electrode, in cm². -1 F is the Faraday constant, 96485 C·mol⁻¹ -1 I is the reaction current, A; t is the reaction time, h.

[0025] The advantage of this invention lies in the fact that, based on the droplet self-transport mechanism in porous media, the microflow of droplets in porous media is mainly affected by the surface tension of the droplets on the pores. The size of the pores and the wettability of the interface are key factors affecting the solid-liquid surface tension. The monotonic gradient wettability and the gradient Laplace pressure formed by the pore size promote the spontaneous migration of droplets towards the electrolyte side, thereby significantly improving the water flooding resistance and in-situ hydrogen peroxide removal capability of the gas diffusion electrode, and improving the efficiency of hydrogen peroxide electrosynthesis. This constructs a gas diffusion electrode that can "breathe." The self-breathing electrode, through its open structure, relies on natural air diffusion for oxygen supply, eliminating the need for an additional gas supply and pressurization system. While achieving the oxygen reduction reaction, it significantly reduces system energy consumption and volume, representing an important direction for promoting the miniaturization, modularization, and stackability of H2O2 electrosynthesis equipment. Furthermore, a self-breathing overcurrent reactor was designed based on this electrode. This reactor features a modular and stackable structure, enabling continuous electrolysis synthesis of high-concentration H2O2 without external oxygen supply. The series integration of four reactor units has been successfully achieved, providing a new solution for the on-site preparation and distributed application of hydrogen peroxide. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0027] Figure 1 The yield of hydrogen peroxide electrosynthesized by gradient electrode and conventional electrode in Example 1 and the comparative example.

[0028] Figure 2 Example 1: Contact angle data of the three-layer wettability gradient of the gradient electrode.

[0029] Figure 3 Example 1: Scanning electron microscope image of the pore gradient of the two layers of the gradient electrode.

[0030] Figure 4 This invention discloses an exploded structural diagram of a self-breathing reactor.

[0031] Figure 5 This is a schematic diagram of the feeding and discharging process of the cathode in a self-breathing reactor.

[0032] Figure 6 This is a schematic diagram of the anode feeding and discharging process of a self-breathing reactor stack.

[0033] Figure 7 The graph shows the changes in hydrogen peroxide production and Faraday efficiency of the self-breathing reactor of the present invention over time in Example 3.

[0034] Figure 8 This is a graph showing the change in hydrogen peroxide production over time in Example 4 of the self-breathing reactor of the present invention.

[0035] Figure 9 The hydrogen peroxide concentrations that can be obtained from the self-breathing reactor of this invention at different cathode flow rates are shown.

[0036] Figure description: 1. Cathode stainless steel end plate, 2. Gasket, 3. First bipolar plate, 4. First self-breathing cathode, 5. Gasket, 6. First cathode flow channel plate, 7. Cation membrane, 8. Anode, 9. Gasket, 10. Anode flow channel plate, 11. Gasket, 12-14. Three sets of modular electrolysis units, 15. Anode conductive plate, 16. Gasket, 17. Anode end plate, wherein 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 constitute a set of modular electrolysis units. Detailed Implementation

[0037] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Example 1

[0039] This embodiment discloses an ordered catalytic layer structure gas diffusion electrode, the method of which is as follows: A 30 wt% polytetrafluoroethylene (PTFE) emulsion is prepared, and carbon fiber conductive paper is completely impregnated into the prepared PTFE solution. The mixture is then ultrasonically mixed at 25°C using a constant-temperature ultrasonic cleaner to ensure uniform PTFE distribution within the carbon fibers of the conductive paper. After drying at 60°C for 12 hours, it is finally calcined at 340°C for 1 hour to obtain a superhydrophobic gas diffusion layer. 0.15 g of commercial carbon black is weighed and added to 5 ml of isopropanol, and premixed in an ultrasonic cleaner. Simultaneously, 0.3 ml of a 60% PTFE emulsion is added to 4 ml of deionized water, stirred evenly, and then added dropwise to the isopropanol mixture containing commercial carbon black to obtain the first cathode slurry. Weigh 0.15g of commercial carbon black and, following the same preparation method as described above, replace 0.3ml of 60% polytetrafluoroethylene emulsion with 0.15ml to obtain the second cathode slurry. Place the first cathode slurry into the slurry tank of a CCM planar spraying equipment, setting the slurry pressure to 0.25bar, the atomization pressure to 3.5bar, and the spraying pressure to 1bar. Spray 2ml of the first cathode slurry layer by layer onto the surface of the superhydrophobic gas diffusion layer, and place it in a muffle furnace for calcination at 340℃ for 1h to obtain a gas diffusion electrode with a first wettability gradient and a first porous catalytic layer. Then, place the second cathode slurry into the slurry tank of the CCM planar spraying equipment. Under the same spraying parameters, control the vertical distance between the spray gun and the gas diffusion layer to be 10cm, and the horizontal spraying spacing to be 5mm. Spray the slurry layer by layer onto the surface of the gas diffusion layer at a constant speed, pausing for 5min after each layer and using hot air to assist drying until the slurry spraying is complete. Finally, the electrode was dried at 60℃ for 12 hours to obtain a gas diffusion electrode with a second wettability gradient and a second porous catalytic layer. The gas diffusion electrode with the second wettability gradient and the second porous catalytic layer was horizontally placed in a plasma etching machine, and the plasma etching machine was vacuum filtered. Using pure oxygen as the gas source, the etching was performed at a power of 25W for 5 minutes to obtain a gas diffusion electrode with an ordered catalytic layer structure.

[0040] The gas diffusion electrode prepared in Example 1 was used as the cathode, and the iridium-tantalum (Ir-Ta) coated electrode was used as the anode. The gas diffusion electrode was then subjected to a 1 mol·L⁻¹ solution. -1 Hydrogen peroxide was synthesized by electrolysis in a sodium sulfate electrolyte solution. The hydrogen peroxide concentration was measured every hour, and the electrolyte was replaced as needed. The test lasted for a total of 5 hours. The amount of hydrogen peroxide produced was determined by the potassium titanium oxalate method.

[0041] Comparative Example 1

[0042] A 30wt% polytetrafluoroethylene (PTFE) emulsion was prepared, and carbon fiber conductive paper was completely impregnated in the prepared PTFE solution. The mixture was then ultrasonically mixed at 25°C using a constant-temperature ultrasonic cleaner to ensure uniform PTFE distribution within the carbon fibers of the conductive paper. The mixture was then dried at 60°C for 12 hours and finally calcined at 340°C for 1 hour to obtain a superhydrophobic gas diffusion layer. 0.15g of commercial carbon black was weighed and added to 5ml of isopropanol, and premixed in an ultrasonic cleaner. Simultaneously, 0.3ml of a 60% PTFE emulsion was added to 4ml of deionized water, stirred thoroughly, and then added dropwise to the isopropanol mixture containing commercial carbon black to obtain the first cathode slurry. Weigh 0.15g of commercial carbon black and, following the same preparation method as described above, replace 0.3ml of 60% polytetrafluoroethylene emulsion with 0.15ml to obtain the second cathode slurry. Place the first cathode slurry into the slurry tank of a CCM planar spraying equipment, setting the slurry pressure to 0.25bar, the atomization pressure to 3.5bar, and the spraying pressure to 1bar. Spray 2ml of the first cathode slurry layer by layer onto the surface of the superhydrophobic gas diffusion layer, and place it in a muffle furnace for calcination at 340℃ for 1h to obtain a gas diffusion electrode with a first wettability gradient and a first porous catalytic layer. Then, place the second cathode slurry into the slurry tank of the CCM planar spraying equipment. Under the same spraying parameters, control the vertical distance between the spray gun and the gas diffusion layer to be 10cm, and the horizontal spraying spacing to be 5mm. Spray the slurry layer by layer onto the surface of the gas diffusion layer at a constant speed, pausing for 5min after each layer and using hot air to assist drying until the slurry spraying is complete. Finally, the electrode was dried at 60℃ for 12 hours to obtain a gas diffusion electrode with two wettability gradients and two porous catalytic layers.

[0043] The gas diffusion electrode prepared in Comparative Example 1 was used as the cathode for electrolysis experiments. The experimental conditions and hydrogen peroxide test methods were the same as in Example 1.

[0044] Comparative Example 2

[0045] A 30wt% polytetrafluoroethylene (PTFE) emulsion was prepared, and carbon fiber conductive paper was completely impregnated in the prepared PTFE solution. The mixture was then ultrasonically mixed at 25°C using a constant-temperature ultrasonic cleaner to ensure uniform PTFE distribution within the carbon fibers of the conductive paper. The mixture was then dried at 60°C for 12 hours and finally calcined at 340°C for 1 hour to obtain a superhydrophobic gas diffusion layer. 0.15g of commercial carbon black was weighed and added to 5ml of isopropanol, and premixed in an ultrasonic cleaner. Simultaneously, 0.3ml of a 60% PTFE emulsion was added to 4ml of deionized water, stirred thoroughly, and then added dropwise to the isopropanol mixture containing commercial carbon black to obtain the first cathode slurry. Weigh 0.15g of commercial carbon black and, following the same preparation method as described above, replace 0.3ml of 60% polytetrafluoroethylene emulsion with 0.15ml to obtain the second cathode slurry. Place the first cathode slurry into the slurry tank of a CCM planar spraying equipment, setting the slurry pressure to 0.25bar, the atomization pressure to 3.5bar, and the spray pressure to 1bar. Control the vertical distance between the spray gun and the gas diffusion layer to 10cm and the horizontal spraying spacing to 5mm. Spray the slurry layer by layer onto the surface of the gas diffusion layer at a constant speed, pausing for 5min after each layer and using hot air to assist drying until the slurry is completely sprayed. Finally, dry the electrode at 60℃ for 12h to obtain a gas diffusion electrode with a disordered catalytic layer structure without gradients.

[0046] The gas diffusion electrode prepared in Comparative Example 2 was used as the cathode for electrolysis experiments. The experimental conditions and hydrogen peroxide test method were the same as in Example 1.

[0047] Comparative Example 3

[0048] The electrode prepared in Example 1 was used as the reaction cathode, and the electrolysis experiment was carried out in the conventional additional oxygen supply mode. Other test conditions and hydrogen peroxide determination methods were the same as in Example 1.

[0049] The yield and Faraday efficiency of hydrogen peroxide production of the electrodes prepared in Example 1 and Comparative Examples 1-3 are as follows: Figure 1 As shown.

[0050] Example 2

[0051] This embodiment discloses a self-breathing reactor, referring to... Figure 4 The fuel cell stack comprises, in sequence, a cathode stainless steel end plate, a first modular electrolysis unit (including a first bipolar plate, a first self-breathing cathode, a first cathode flow channel plate, a cation membrane, a first anode, and a first anode flow channel plate), and three other modular electrolysis units (all with the same structure) connected in series, an anode conductive plate, an anode stainless steel end plate, a plastic bolt sleeve, and plastic gaskets between the plates.

[0052] The anode uses nickel foam with a thickness of 4 mm. The first self-breathing cathode uses the electrode prepared in Example 1.

[0053] In other embodiments of the present invention, according to actual situations, the number of modular electrolysis units can be arbitrarily set to form a stack with different specifications.

[0054] The bipolar plate is formed by fastening an anode current collector plate and a self-breathing cathode "field" character frame with bolts. The anode current collector plate is a titanium plate with a platinum coating.

[0055] The self-breathing cathode "field" character frame functions to conduct electricity and support the cathode gas diffusion electrode. At the same time, the frame structure can expose the gas diffusion layer side of the first self-breathing cathode (i.e., the ordered catalytic layer structure gas diffusion electrode of the present invention) to the atmospheric environment, enabling it to achieve self-breathing oxygen supply. The gas supply mechanisms such as gas chambers and oxygen generators in the traditional structure are eliminated, greatly reducing the complexity of the system. The frame structure can be a "field" character, "well" character or other honeycomb structures (preferably the "field" character structure), and the material can be ordinary carbon, titanium, and titanium, nickel or graphite with noble metal coatings (platinum, palladium, iridium, tantalum) (preferably graphite).

[0056] There is a cathode terminal on the first bipolar plate, which functions to connect to the negative pole of the power supply. The material can be ordinary carbon, titanium, and titanium, nickel or graphite with noble metal coatings (platinum, palladium, iridium, tantalum) (preferably graphite).

[0057] The cathode flow channel plate and the anode flow channel plate have a rectifying structure, which functions to evenly distribute the flow field. The material can be acrylic, PEEK, etc. (preferably PEEK).

[0058] The anode conductive plate functions to conduct electricity for the anode. The material can be nickel or titanium with a noble metal coating (platinum, palladium, iridium, tantalum) (preferably a titanium plate with a platinum coating).

[0059] There is an anode terminal on the anode conductive plate, which functions to connect to the positive pole of the power supply. The material can be nickel or titanium with a noble metal coating (platinum, palladium, iridium, tantalum) (preferably a titanium plate with a platinum coating).

[0060] The self-breathing cathode "field" character frame and the flow channel plate are both provided with first and second feed and discharge diversion holes, and the diversion holes are superimposed and combined to form the inlet and outlet flow channels in the stack.

[0061] There are 2 groups of inlet and outlet external interfaces on the cathode end plate, corresponding to the first inlet and outlet and the second inlet and outlet respectively.

[0062] The first inlet and outlet external interfaces are connected to the first inlet and outlet ports of all plates, forming the first inlet and outlet main channel. Since the anode cavity of the anode flow channel plate is connected to the first inlet and outlet port, the anode cavity of each anode flow channel plate becomes a branch flow channel of the first inlet and outlet main channel.

[0063] The second inlet and outlet external interfaces are connected to the second inlet and outlet ports of all plates, forming the main second inlet and outlet channel. Since the cathode cavity of the cathode flow channel plate is connected to the second inlet and outlet ports, the electrolyte cavity of each electrolyte chamber plate becomes a branch flow channel of the main second inlet and outlet channel. For example... Figure 5 , Figure 6 As shown.

[0064] Example 3

[0065] This embodiment uses the self-breathing reactor described in Example 2 for production testing. This embodiment employs a fixed constant current of 10A. The calculated current density of the gas diffusion electrode in a single electrolysis unit is 100 mA / cm². 2 The reaction was carried out using a cathode circulation flow method, with the initial catholyte being 1 L of pure water. The catholyte entered the fuel cell stack at a flow rate of 100 ml / min, was evenly distributed to each cathode chamber, and exited the stack after passing through the cathode channels, generating hydrogen peroxide. Each cycle lasted for 2 hours. At the end of the cycle, the cell pressure was recorded, and the hydrogen peroxide concentration was tested using the potassium titanate oxalate method. Afterward, all the catholyte was replaced, and the next cycle began.

[0066] NaOH solution is used as the anolyte, which is circulated from the anode feed inlet into the fuel cell stack at a flow rate of 150 ml / min, evenly distributed to each anode cavity, and exits the stack after passing through the anode flow channel. The anolyte is replenished every 1 hour with 100 ml of 30% NaOH solution.

[0067] Example 4

[0068] This embodiment is basically the same as embodiment 3, except that:

[0069] The reaction is carried out by direct flow without cyclic electrolysis, that is, pure water is continuously flowing in, and the resulting hydrogen peroxide is not re-entered into the stack. The cathode electrolyte flow rate is 5 ml / min.

[0070] Example 5

[0071] This embodiment is basically the same as embodiment 4, except that:

[0072] The cathode electrolyte flow rate is 15 ml / min.

[0073] Example 6

[0074] This embodiment is basically the same as embodiment 4, except that:

[0075] The cathode electrolyte flow rate is 45 ml / min.

[0076] from Figure 1 It can be seen that the electrode prepared in Example 1, with three wettability gradients and two pore gradients, outperforms the electrode prepared in Comparative Example 1, which has two wettability gradients and two pore gradients, and is also superior to the conventional electrode without a gradient structure prepared in Comparative Example 2. Furthermore, a comparison with Comparative Example 3 shows that the electrode prepared in Example 1 can achieve the performance level of a conventional aerobic supply without additional oxygen supply, demonstrating that the electrode can supply oxygen through respiration.

[0077] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of the claims of the present invention.

Claims

1. A gas diffusion electrode with an ordered catalytic layer structure, characterized in that, It consists of a gradient-structured catalytic layer and a gas diffusion layer; the gradient-structured catalytic layer has three wettability gradients and two pore structure gradients, and the gas diffusion layer is a superhydrophobic gas diffusion layer; its preparation method includes the following: The first step is to ultrasonically impregnate the substrate of the gas diffusion layer in polytetrafluoroethylene emulsion, dry and calcine it to obtain the superhydrophobic gas diffusion layer. The second step involves ultrasonically premixing commercial carbon black particles and isopropanol to obtain a first mixture; simultaneously, 60% by mass of polytetrafluoroethylene emulsion is added dropwise to the first mixture to obtain a first cathode slurry; the first cathode slurry is placed in the slurry tank of a catalyst coating proton membrane (CCM) planar spraying equipment, the spraying parameters are set, the first cathode slurry is sprayed onto the surface of the gas diffusion layer obtained in the first step, and then placed in a muffle furnace for calcination to obtain a gas diffusion electrode with a first wettability gradient and a first porous catalyst layer; The third step involves ultrasonically premixing commercial carbon black particles and isopropanol to obtain a second mixture. Simultaneously, 60% by mass of polytetrafluoroethylene emulsion is added dropwise to the second mixture to obtain a second cathode slurry. The second cathode slurry is placed in the slurry tank of a CCM planar spraying equipment. Spraying parameters are set, and the vertical distance between the spray gun and the gas diffusion layer and the horizontal spraying spacing are controlled. The slurry is sprayed layer by layer onto the surface of the gas diffusion layer at a constant speed. After each layer is sprayed, the process is paused for 1 to 10 minutes and hot air is used to assist drying until the slurry is completely sprayed. Finally, the slurry is dried at a constant temperature to obtain a gas diffusion electrode with a second wettability gradient and a second porous catalytic layer. The fourth step involves horizontally placing the gas diffusion electrode with the second wettability gradient and the second porous structure catalyst layer into a plasma etching machine, using pure oxygen or air as the gas source to perform plasma etching on the surface of the catalyst layer, thereby forming a gas diffusion electrode with the third wettability gradient and the second porous structure catalyst layer. An ordered catalytic layer structure gas diffusion electrode was obtained.

2. The ordered catalytic layer structure gas diffusion electrode according to claim 1, characterized in that, The gas diffusion electrode with a third wettability gradient and a second porous catalytic layer exhibits discontinuous monotonic changes in both contact angle and porosity along the thickness direction of the catalytic layer. From the surface of the catalytic layer to the gas diffusion layer, the contact angles are successively 15°–40°, 100°–130°, and 130°–160°. The pore structure gradually becomes denser, forming a pore structure gradient.

3. The ordered catalytic layer structure gas diffusion electrode according to claim 1, characterized in that, The substrate of the gas diffusion layer is one or a combination of carbon fiber conductive carbon paper, carbon cloth, carbon felt, or stainless steel mesh.

4. The gas diffusion electrode with an ordered catalytic layer structure according to claim 1, characterized in that, The mass fraction of the polytetrafluoroethylene emulsion in the first step is 5-30%, the ultrasonic impregnation time is 20-60 min, and the calcination is calcined at 340℃ for 1 h.

5. The gas diffusion electrode with an ordered catalytic layer structure according to claim 1, characterized in that, In the second step, the ratio of commercial carbon black particles to isopropanol is 1g:30-40ml, the volume ratio of the polytetrafluoroethylene emulsion to the first mixture is 1ml:10-20ml, the spraying parameters are: slurry pressure is 0.1-0.35bar, atomization pressure is 2.5-4.5bar, and spray pressure is 0.5-1.5bar; the calcination is carried out at 327-350℃ for 0.5-1h.

6. The gas diffusion electrode with an ordered catalytic layer structure according to claim 1, characterized in that, In the third step, the dosage ratio of commercial carbon black particles to isopropanol is 1 g: 30 - 40 ml, the volume ratio of the polytetrafluoroethylene emulsion to the second mixed solution is 1 ml: 20 - 40 ml, and the spraying parameters are as follows: the slurry pressure is 0.1 - 0.35 bar, the atomization pressure is 2.5 - 4.5 bar, and the spray radiation pressure is 0.5 - 1.5 bar; the vertical distance between the spray gun and the gas diffusion layer is controlled to be 5 - 20 cm, and the horizontal spraying distance is 3 - 8 mm.

7. Use of the ordered catalytic layer structure gas diffusion electrode according to any one of claims 1 - 6 in the electrosynthesis of hydrogen peroxide.

8. A self-breathing electrode, characterized in that, Obtained based on the ordered catalytic layer structure gas diffusion electrode according to any one of claims 1 - 6, without additional oxygen supply, and capable of continuously resisting flooding.

9. A self-breathing fuel cell stack, characterized in that, It includes two end plates, and a plurality of modular electrolysis units and an anode conductive plate arranged between the two end plates; each modular electrolysis unit includes, in sequence: a bipolar plate, a self-breathing cathode, a cathode flow channel plate, a cation exchange membrane, an anode, and an anode flow channel plate; the self-breathing cathode uses the ordered catalytic layer structure gas diffusion electrode according to any one of claims 1 - 6; The bipolar plate is formed by fastening an anode current collector plate and a hollowed-out frame for conducting electricity and supporting the self-breathing cathode with bolts. The anode current collector plate is a titanium plate with a platinum coating; one side of the gas diffusion layer of the self-breathing cathode is adhered to the hollowed-out frame so that one side of the gas diffusion layer can be exposed to the atmospheric environment to achieve self-breathing oxygen supply; a cathode terminal is provided on the bipolar plate for connecting to the negative pole of the power supply.

10. The self-breathing reactor stack according to claim 9, characterized in that, The hollowed-out frame is in a "field" character, "well" character or honeycomb structure, and the material is carbon, titanium, titanium with a noble metal coating, nickel or graphite.

Images