Composite microporous layer structure for oxygen evolution of electrolytic tank and preparation method of composite microporous layer structure

Abstract

The invention belongs to the technical field of electrolytic tanks, and particularly relates to a composite microporous layer structure for oxygen evolution of an electrolytic tank and a preparation method thereof.The composite microporous layer structure comprises a substrate layer, a bubble separation layer, a bubble growth layer, a bubble nucleation layer and a bubble removal layer which are sequentially stacked; the bubble separation layer is connected with an anode side cavity opening of the electrolytic tank; continuous branch-shaped pore throats are arranged in the bubble nucleation layer and the bubble growth layer; the bubble nucleation layer is of a periodic structure, the valley part forms a preferential nucleation area, and the bottom of the valley part is connected with the pore throat; the bubble removing layer is arranged at a position outside the preferential nucleation area on the bubble nucleation layer; the bubble removal layer is disposed toward the electrode interface. Compared with the prior art, the invention solves the problem that the negative influence caused by bubble accumulation cannot be fully solved in the prior art. The composite microporous layer structure in the scheme has the characteristics of enhancing the electrode interface reaction and promoting the discharge of products, and can realize the efficient oxygen evolution of the electrolytic tank and promote the rapid discharge of oxygen in the form of small bubbles.

Description

Technical Field

[0001] This invention belongs to the field of electrolytic cell technology, specifically relating to a composite microporous layer structure for oxygen evolution in electrolytic cells and its preparation method. Background Technology

[0002] Proton exchange membrane water electrolysis (PEMWE), as a highly efficient and clean hydrogen production technology, holds significant promise for applications in renewable energy storage and green hydrogen energy. However, when PEMWE operates at high current densities, the mass transport problem on the anode side becomes a key factor limiting its performance. This problem mainly stems from the complex transport behavior of oxygen bubbles generated during electrolysis within the catalyst layer (CL) and porous transport layer (PTL). Excess oxygen cannot be expelled in time, leading to bubble accumulation. On one hand, bubbles retained on the electrode surface can obscure reaction sites, increasing the cell's activation overpotential; on the other hand, bubble accumulation hinders the transport of reactant water, causing localized dehydration of the proton exchange membrane, reducing proton conductivity, and thus increasing ohmic losses and concentration overpotential, ultimately degrading cell performance.

[0003] Furthermore, traditional PTLs typically employ sintered titanium fibers or porous titanium plates, whose randomly distributed pores result in tortuous bubble transport paths, low venting efficiency, and a tendency to reach a steady-state of bubble accumulation. To optimize bubble management, existing technologies have proposed surface modification treatments or gradient pore designs, but these approaches all focus on a single physical property and are insufficient to achieve the expected high-efficiency reaction and rapid bubble venting.

[0004] For example, patent CN115652352A discloses "a gas-liquid diffuser for alkaline water electrolysis to produce hydrogen and its application", which provides a gas-liquid diffuser with a cross-section formed by multiple flow channels in a wave shape. Although it can make the fluid flow evenly on both sides of the gas-liquid diffuser and reduce the contact resistance, it has limited effect in promoting the efficient discharge of bubbles and cannot meet the requirement of rapid bubble discharge under the high current density of PEMWE.

[0005] For example, patent CN111408725A discloses "a method for preparing a gas diffusion layer with gradient pore size for an SPE electrolyzer," which designs a gas diffusion layer with gradient pore size, which can promote gas-liquid mass transfer in the electrolysis chamber to a certain extent and improve the performance of the electrolyzer. However, this design is insufficient in terms of the rapid and directional removal of the large number of bubbles generated under high current density, and cannot fully solve the negative impact of bubble accumulation.

[0006] For example, patent CN119108565A discloses "a gas diffusion layer with good water management performance and its preparation method", which realizes drainage under high humidity through a microporous layer with bimodal pore size distribution. However, this solution does not take into account the problem of bubbles and their emission, and cannot fully solve the negative impact of bubble accumulation.

[0007] It is evident that there is currently a lack of porous structure designs that comprehensively improve the multi-physical processes of bubble nucleation, growth, and expulsion. Summary of the Invention

[0008] The purpose of this invention is to provide a composite microporous layer structure for oxygen evolution in electrolytic cells and its preparation method, thereby addressing at least one of the aforementioned problems and resolving the negative impacts of bubble accumulation that cannot be adequately addressed in existing technologies. The composite microporous layer structure of this invention enhances the electrode interface reaction and promotes the discharge of products, enabling efficient oxygen evolution in electrolytic cells and facilitating the rapid discharge of oxygen in the form of small bubbles.

[0009] The objective of this invention is achieved through the following technical solution: The first aspect of the present invention discloses a composite microporous layer structure for oxygen evolution in an electrolytic cell, comprising a base layer, a bubble detachment layer, a bubble growth layer, a bubble nucleation layer and a bubble removal layer stacked sequentially. The bubble detachment layer is connected to the anode side cavity of the electrolytic cell, and the bubble detachment layer is hydrophilic. The bubble nucleation layer and the bubble growth layer are provided with continuous branched pore throats inside, and the inner wall surface of the pore throats is hydrophobic. The bubble nucleation layer has a periodic structure, wherein: the valley forms a preferential nucleation region with superhydrophilicity, and the bottom of the preferential nucleation region is connected to the pore throat; The bubble removal layer is disposed on the bubble nucleation layer outside the preferred nucleation region, and the surface of the bubble nucleation layer has a corrugated structure; the bubble removal layer deposits noble metal particles on the protrusions of the bubble nucleation layer surface and forms a superhydrophobic surface in the depressions of the bubble nucleation layer surface; the bubble removal layer is disposed facing the electrode interface.

[0010] Preferably, the pore size of the pore throat increases along the gas phase flow direction, and the pore throat is connected to the bubble release layer from the preferential nucleation region.

[0011] Preferably, the noble metal particles are stacked to form a nanoporous structure, and the noble metal particles are stacked in a peak-shaped structure at the protrusions on the surface of the bubble-shaped nucleation layer. The superhydrophobic surface is formed by depositing a superhydrophobic agent, and the contact angle of the superhydrophobic surface is greater than 150°.

[0012] Preferably, the bubble nucleation layer is composed of micron-sized porous titanium; The preferred nucleation region consists of micro / nano structures formed in the valley of the bubble nucleation layer and a superhydrophilic agent coated on the surface of the micro / nano structures. The contact angle of the preferred nucleation region is less than 30°.

[0013] Preferably, the bubble growth layer is made of porous titanium, wherein the porosity of the bubble growth layer is greater than the porosity of the bubble nucleation layer.

[0014] Preferably, the base layer is a titanium mesh, and the bubble release layer is a millimeter-scale titanium felt.

[0015] A second aspect of this invention discloses a method for preparing a composite microporous layer structure for oxygen evolution in an electrolytic cell as described above, comprising the following steps: S1: De-bubbling layers are stacked onto the substrate layer; S2: Prepare slurries with different porosities, wherein the porosity of the bottom layer slurry is higher than that of the top layer slurry; S3: A bubble growth layer is formed on the bubble release layer by a casting process, and then a bubble nucleation layer is formed on the bubble growth layer by a casting process. S4: Periodic structures are imprinted on the surface of the bubble nucleation layer, followed by sintering; S5: Hole throats are formed separately using laser processing technology; S6: Hydrophobic modification of the pore throat; S7: A mask is used to cover the peaks of the bubble nucleation layer, and then a superhydrophilic agent is coated on the valleys of the bubble nucleation layer to form a preferential nucleation region; S8: The mask covers the recessed areas of the corrugated structure, where noble metal particles are deposited by magnetron sputtering; the mask covers the protruding areas of the corrugated structure, where a superhydrophobic agent is deposited to form a superhydrophobic surface.

[0016] Preferably, the slurry is composed of precious metal particles, a pore-forming agent, isopropanol, and a hydrophilic binder, and the slurry is ball-milled to remove air bubbles.

[0017] Preferably, the sintering is carried out in an Ar atmosphere.

[0018] Preferably, the pore throat is formed by first using infrared laser processing to create a large-diameter main pore throat with gradually increasing pore size, and then using ultraviolet laser processing to create branch pore throats with gradually increasing pore size.

[0019] The working principle of this invention is as follows: The bubble nucleation layer has a preferential nucleation region. The bubble removal layer is orderly attached to the porous surface of the bubble nucleation layer, which makes it easier for bubbles to nucleate in the preferential nucleation region of the bubble nucleation layer, while making it difficult for them to nucleate in the bubble removal layer. This has the property of inhibiting bubble nucleation.

[0020] The bubble growth layer is adjacent to the bubble nucleation layer and has a pore throat structure, which promotes the directional growth of bubbles along a shorter path to the bubble detachment layer, and then they detach rapidly under the impetus of the two-phase flow.

[0021] Compared with the prior art, the present invention has the following beneficial effects: (1) The surface morphology of the composite microporous layer increases the number of active sites for oxygen evolution reaction, enhances the electrochemical reaction efficiency at the same current density, and reduces the activation overpotential of the battery.

[0022] (2) The composite microporous layer structure physically separates the electrode interface where the oxygen evolution reaction occurs from the bubble preferential nucleation region, which can prevent bubbles from nucleating and remaining at the electrode interface and causing deactivation of the reaction site. It promotes the nucleation and growth of bubbles in the region far away from the electrode interface, thereby mitigating the adverse effects of bubbles shielding the electrode and reducing the bubble shielding overpotential.

[0023] (3) The layered design of the composite microporous layer can control the orderly nucleation, growth and expulsion of oxygen generated in the reaction, and prevent oxygen from accumulating in the porous structure and causing blockage. An oxygen concentration gradient can be formed between the electrode interface and the preferential nucleation region, which promotes the diffusion of dissolved oxygen along the concentration gradient and prevents the oxygen concentration in the electrode interface region from being too high, thereby reducing the oxygen concentration overpotential. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the composite microporous layer of the present invention.

[0025] Figure 2 This is a partially enlarged schematic diagram of the preferential nucleation region in the bubble nucleation layer of the present invention.

[0026] Figure 3 This is a graph showing the relationship between the contact angle and the gas phase transfer rate of the composite microporous layer of the present invention, simulated based on the heterogeneous nucleation theory.

[0027] Figure 4 This is a schematic diagram of the oxygen concentration gradient formed by the bubble nucleation layer and the bubble removal layer of the present invention.

[0028] Figure 5 This is a partially enlarged schematic diagram of the structure of the bubble-removing layer of the present invention.

[0029] Figure 6 This is a schematic diagram of the pore throat structure in the bubble growth layer of the present invention.

[0030] In the figure: 1-bubble removal layer; 2-bubble nucleation layer; 3-bubble growth layer; 4-bubble detachment layer; 5-substrate layer; 6-electrode interface; 7-anode side cavity; 8-preferred nucleation region; 9-far nucleation region; 10-near nucleation region; 11-bubble; 101-noble metal particle; 201-corrugated structure; 202-superhydrophobic surface; 301-pore throat; 801-superhydrophilic agent; 802-micro / nano structure. Detailed Implementation

[0031] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0032] Unless otherwise specified, the reagents used in the following description are conventional commercial products, the methods used are well-known in the art, and any other matters not covered herein can be handled using existing technology.

[0033] Example 1 A highly efficient oxygen evolution composite microporous layer structure, such as Figure 1 As shown, the structure includes a bubble removal layer 1, a bubble nucleation layer 2, a bubble growth layer 3, a bubble detachment layer 4, and a base layer 5, which are stacked sequentially. The bubble nucleation layer 2 has a preferential nucleation region 8. The bubble removal layer 1 is orderly attached to the porous surface of the bubble nucleation layer 2, making it easier for bubbles 11 to nucleate in the preferential nucleation region 8 of the bubble nucleation layer 2, while making it difficult for them to nucleate in the bubble removal layer 1, thus inhibiting bubble nucleation. The bubble growth layer 3 is adjacent to the bubble nucleation layer 2 and has a pore throat 301 structure inside. This promotes the directional growth of bubbles 11 entering the pore throat 301 from the preferential nucleation region 8 along a shorter path to the bubble detachment layer 4, where they then rapidly detach under the impetus of the two-phase flow. The orderly combination of the bubble removal layer 1, the bubble nucleation layer 2, the bubble growth layer 3, and the bubble detachment layer 4 increases the reaction sites at the electrode interface 6, improves conductivity, and promotes efficient bubble detachment.

[0034] More specifically: The bubble nucleation layer 2 is composed of micron-sized porous titanium, exhibiting a periodic undulating structure and differentiated hydrophilic properties. Micro / nano structures 802 are formed in the valleys (surface depressions) of the periodic structure of the bubble nucleation layer 2, and a superhydrophilic agent 801 is coated into the micro / nano structures 802 to impart superhydrophilic properties, thereby forming a structure like... Figure 2 The preferred nucleation region 8 is shown. This preferred nucleation region 8 possesses superhydrophilic properties, with a contact angle of less than 30°; further... Figure 3 As shown by the heterogeneous nucleation principle, the rate at which dissolved oxygen transfers from the liquid phase to the gas phase (gas phase transfer rate) is higher in the superhydrophilic region (i.e., the preferential nucleation region 8), making it easier to form bubbles 11, thus resulting in a high bubble growth rate. At the same time, the surface of the micro-nano structure 802 in the preferential nucleation region 8 can further promote the nucleation of bubbles 11 within the preferential nucleation region 8.

[0035] The nucleation process of bubble 11 requires a certain dissolved oxygen concentration, and once bubble 11 is nucleated, it continuously absorbs dissolved oxygen into itself. The superhydrophilic properties and the micro / nano structure surface 802 can enhance the nucleation rate of bubble 11. Therefore, bubble 11 is more likely to nucleate and grow in the preferential nucleation region 8, forming a dissolved oxygen concentration gradient with the bubble removal layer 1, such as... Figure 4 As shown, the nucleation of bubble 11 causes a decrease in dissolved oxygen concentration in the preferential nucleation region 8. Meanwhile, the distant nucleation region 9 has high conductivity and numerous reaction sites, resulting in a higher dissolved oxygen concentration than the near-nucleation region 10. This allows dissolved oxygen to diffuse along the concentration gradient from the distant nucleation region 9 to the near-nucleation region 10. Driven by this dissolved oxygen concentration gradient, dissolved oxygen is continuously transported from the distant nucleation region 9 to the near-nucleation region 10. This ensures sufficient dissolved oxygen in the preferential nucleation region 8 for nucleation while maintaining a lower dissolved oxygen concentration in other regions. This ensures successful nucleation of bubble 11 in the preferential nucleation region 8 while preventing premature nucleation in non-nucleation regions. Furthermore, the capillary force generated by the superhydrophilic properties allows water to penetrate into the rough areas of the preferential nucleation region 8, forming a continuous wetting film. Consequently, the nucleated bubble 11 detaches quickly from the preferential nucleation region 8, achieving efficient nucleation and rapid detachment within the preferential nucleation region 8.

[0036] The bubble-removing layer 1 is a nanoporous structure composed of noble metal particles 101. It avoids the preferential nucleation region 8 of the bubble nucleation layer 2 and is orderly attached to the surface of the bubble nucleation layer 2, facing the electrode interface 6. The density of the noble metal particles 101 in the bubble nucleation layer 1 increases or decreases accordingly with the periodic undulations (corrugated structure 201) of the surface of the bubble nucleation layer 2: with convex surfaces of the corrugated structure 201, the noble metal particles 101 are more dense, and the nanoporous structure is denser; with concave surfaces of the corrugated structure 201, the nanoporous structure is sparser, thus forming a peak-like structure with alternating convex and concave distributions. This configuration of the bubble-removing layer 1 increases the contact area with the catalyst-coated membrane (CCM), thereby increasing the reaction sites for the surface oxidation-reduction reaction (OER). In the raised areas on the surface of the bubble-shaped nucleus layer 2, the noble metal particles 101 are more dense and have high conductivity, which can increase the surface reaction sites; in the recessed areas on the surface of the bubble-shaped nucleus layer 2, the noble metal particles 101 are more sparse and have relatively low conductivity, which macroscopically manifests as the OER reaction sites being more concentrated in the raised areas on the surface.

[0037] The nanoporous structure formed by the noble metal material particles in the bubble-removing layer 1 further develops microwave-like ripples on the surface, such as... Figure 5As shown. The raised areas (peak-shaped structure) of the microwave ripples are used to increase the reaction surface and improve conductivity, thereby increasing the OER reaction sites at the electrode interface 6; the recessed areas of the microwave ripples form a superhydrophobic surface 202, which has superhydrophobic properties and a contact angle greater than 150°. Therefore, by Figure 3 As shown by the heterogeneous nucleation principle, the gas phase transfer rate is lower in the superhydrophobic surface 202 region, resulting in a low bubble growth rate. This can suppress bubble nucleation and effectively inhibit the generation of dissolved oxygen at the near electrode interface 6 during electrolysis, thus preventing the original reaction sites from being blocked and promoting the transport of dissolved oxygen in the form of diffusion as much as possible.

[0038] like Figure 6 As shown, the bubble growth layer 3 has an ordered pore throat 301 structure inside. The inner surface of the pore throat 301 has hydrophobic properties, which reduces the resistance to gas phase transport, guides the bubbles 11 to transport directionally along the pore throat 301 and prevents liquid phase inflow, thereby separating the liquid phase and gas phase transport channels, ensuring that the reactants can smoothly reach the OER reaction sites at the electrode interface 6, and promoting the transport of bubbles 11 along the direction of the pore throat 301. The branched pore throat 301 of the bubble growth layer 3 has a pore size that gradually increases along the gas phase flow direction, which can reduce the ineffective lateral transport of bubbles 11 and prevent bubbles 11 from merging into large bubbles 11 that hinder reactant transport. Furthermore, one end of the pore throat 301 is connected to the bottom of the preferential nucleation region 8 (i.e., a portion of the pore throat 301 is also formed in the bubble nucleation layer 2), allowing the nucleated bubbles 11 to quickly enter the pore throat 301 for transport.

[0039] The bubble detachment layer 4 has high porosity and millimeter-scale pore size, and is hydrophilic, allowing bubbles 11 to quickly merge into larger bubbles 11. These larger bubbles 11 are then easily discharged from the bubble detachment layer 4 under the influence of the reactants. The side of the bubble detachment layer 4 is also connected to the anode-side cavity 7 of the electrolytic cell. Liquid water from the anode side of the electrolytic cell is directly supplied to the bubble detachment layer 4 and transported to the bubble growth layer 3, while the bubbles 11 are promptly discharged from the porous structure by the two-phase flow.

[0040] The substrate layer 5 serves as the mechanical support for this microporous layer structure. It does not require the design of flow field distribution and has hydrophobic properties, high conductivity, and high surface uniformity.

[0041] The composite microporous layer structure of this scheme comprises: a bubble nucleation layer 2 with a preferential nucleation region 8, promoting the nucleation of bubbles 11 within the bubble nucleation layer 2; a bubble removal layer 1 attached to the bubble nucleation layer 2, inhibiting the nucleation of bubbles 11 in the region adjacent to the electrode interface 6, thus preventing the reaction sites at the electrode interface 6 from being blocked by bubbles 11; a directional growth layer used to promote the directional transport of bubbles 11 and prevent bubbles 11 from rapidly merging into large bubbles 11; and a bubble separation layer with superhydrophilic properties and low surface tension used to promote the rapid detachment of bubbles 11 from the porous structure through two-phase flow. This configuration enables the composite microporous layer structure designed in this scheme to promote efficient electrode reaction and rapid removal of bubbles 11.

[0042] Example 2 This embodiment provides a method for preparing a composite microporous layer structure based on a micron-scale porous substrate as described in Example 1. The specific steps are as follows: Commercial titanium mesh structure was directly selected as the base layer 5, and millimeter-level titanium felt was used as the bubble release layer 4.

[0043] A bubble growth layer 3 and a bubble nucleation layer 2 are prepared on the bubble detachment layer 4. The specific steps are as follows: S1. Combining the casting process and gradient slurry system, a bubble growth layer 3 and a bubble nucleation layer 2 are constructed on the bubble release layer 4: a bottom slurry with high porosity and an upper slurry with low porosity are prepared using precious metal titanium particles, PMMA pore-forming agent, isopropanol, and Nafion solution hydrophilic binder, respectively. Then, the bubbles 11 in the slurry are removed by ball milling to obtain a uniform slurry. The volume fraction of PMMA in the slurry determines the macroscopic pore size and overall porosity; the Nafion solution hydrophilic binder reduces porosity by filling pores and providing hydrophilic channels; the packing ratio of Ti particles determines the density of the solid skeleton. Therefore, for the desired high-porosity bottom slurry, the following formulation (volume fraction) can be used: 30-40% titanium particles, 40-60% PMMA pore-forming agent, 1-2% Nafion solution hydrophilic binder, and isopropanol as solvent; for the desired low-porosity top slurry, the following formulation (volume fraction) can be used: 10-20% titanium particles, 0-10% PMMA pore-forming agent, 3-5% Nafion solution hydrophilic binder, and isopropanol as solvent.

[0044] S2. First, the bottom layer slurry is cast onto the substrate, then the top layer slurry is cast onto the bottom layer slurry. After settling, a high-porosity bubble growth layer 3 and a low-porosity bubble nucleation layer 2 are formed. The high-porosity bottom layer reduces diffusion resistance and promotes gas-liquid transport; the low-porosity top layer increases electronic conductivity and active site density. Thus, the difference in porosity enables rapid outward migration and elimination of bubbles at the structural level.

[0045] S3. Use a mold to imprint a periodic undulating structure on the surface of the bubble nucleation layer 2.

[0046] S4. Sintering is carried out in an Ar atmosphere.

[0047] S5. Using laser composite processing technology (multi-wavelength laser processing), microwave texture structure 201 is first processed on the surface of bubble nucleation layer 2; then, a tree-like throat structure with increasing pore size is constructed on bubble growth layer 3: first, infrared laser processing is used to form a large-diameter main throat 301 with gradually increasing pore size, and then ultraviolet laser is switched to process branch throats 301 with gradually increasing pore size at a certain branching angle.

[0048] S6. Hydrophobic modification of the inside of the pore throat 301: Inject PTFE dispersion (hydrophobic agent) into the pore throat 301, and then dry it to make the hydrophobic agent firmly bonded to the pore wall.

[0049] S7. Constructing the preferential nucleation region 8: A mask is used to cover the surface peaks of the bubble nucleation layer 2, and a superhydrophilic agent 801 is sprayed onto its surface valleys. Then, a hydrothermal reaction method is used to form micro / nano structures 802 on the surface of the preferential nucleation region 8. The overall hydrothermal reaction process is as follows: an acidic aqueous solution of titanium tetrachloride is prepared as a precursor solution and transferred to a hydrothermal reactor. Subsequently, the substrate (the bubble nucleation layer 2 after spraying with superhydrophilic agent 801) is placed in the hydrothermal reactor to undergo a hydrothermal reaction, thereby achieving the growth of TiO2 nanostructures on the substrate surface.

[0050] S8. Based on the prepared bubble nucleation layer 2, the bubble removal layer 1 is further prepared. The specific steps are as follows: S81. Construct a bubble 11 removal layer at the protrusion of the microwave texture structure 201 of the bubble nucleation layer 2: Cover the recessed area of ​​the bubble nucleation layer 2 with a mask, and use an Ir target to perform magnetron sputtering deposition on the uncovered protrusion area.

[0051] S82, such as Figure 5 As shown, a superhydrophobic surface 202 is constructed in the depression of the microwave texture structure 201 of the bubble nucleation layer 2: the microwave texture protrusions are covered by a mask, and a superhydrophobic agent is deposited in the microwave texture depression to form a superhydrophobic surface 202 with a large contact angle.

[0052] Example 3 This embodiment provides a method for directly imprinting a microwave textured structure 201 onto the bubble nucleation layer 2, which further avoids the complexity of the processing method caused by laser processing and eliminates the need to construct the micro / nano structure 802 surface in the preferred nucleation region 8, thus simplifying the fabrication method. This composite microporous layer structure is essentially the same as in Embodiment 1, except that the micro / nano structure 802 in the preferred nucleation region 8 is removed.

[0053] The specific steps are as follows: Commercial titanium mesh structure was directly selected as the base layer 5, and millimeter-level titanium felt was used as the bubble release layer 4.

[0054] The specific steps for preparing bubble growth layer 3 and bubble nucleation layer 2 are as follows: S1. Construct bubble growth layer 3 and bubble nucleation layer 2 by combining tape casting process and gradient slurry system: Use precious metal titanium particles, PMMA pore-forming agent, isopropanol and Nafion solution hydrophilic binder to prepare bottom slurry with high porosity and top slurry with low porosity respectively. Remove bubbles 11 in the slurry by ball milling to obtain uniform slurry. The volume fraction of PMMA in the slurry determines the macroscopic pore size and overall porosity; the Nafion solution hydrophilic binder reduces porosity by filling pores and providing hydrophilic channels; the packing ratio of Ti particles determines the density of the solid skeleton. Therefore, for the desired high-porosity bottom slurry, the following formulation (volume fraction) can be used: 30-40% titanium particles, 40-60% PMMA pore-forming agent, 1-2% Nafion solution hydrophilic binder, and isopropanol as solvent; for the desired low-porosity top slurry, the following formulation (volume fraction) can be used: 10-20% titanium particles, 0-10% PMMA pore-forming agent, 3-5% Nafion solution hydrophilic binder, and isopropanol as solvent.

[0055] S2. First, the bottom layer slurry is cast onto the substrate, then the top layer slurry is cast onto the bottom layer slurry. After settling, a high-porosity bubble growth layer 3 and a low-porosity bubble nucleation layer 2 are formed. The high-porosity bottom layer reduces diffusion resistance and promotes gas-liquid transport; the low-porosity top layer increases electronic conductivity and active site density. Thus, the difference in porosity enables rapid outward migration and elimination of bubbles at the structural level.

[0056] S3. First, use a mold to imprint a periodic undulating structure, and then imprint a microwave texture structure 201 on the surface of the bubble nucleation layer 2.

[0057] S4. Sintering is carried out in an Ar atmosphere.

[0058] S5. Using laser composite processing technology (multi-wavelength laser processing), a tree-like throat 301 structure with increasing pore size is constructed in the bubble growth layer 3: first, infrared laser processing is used to form a large-diameter main throat 301 with gradually increasing pore size, and then ultraviolet laser is switched to process branch throats 301 with gradually increasing pore size at a certain branching angle.

[0059] S6. Hydrophobic modification of the inside of the pore throat 301: Inject PTFE dispersion (hydrophobic agent) into the pore throat 301, and then dry it to make the hydrophobic agent firmly bonded to the pore wall.

[0060] S7. Constructing the preferred nucleation region 8: Cover the peak of the bubble nucleation layer 2 with a mask and spray superhydrophilic agent 801 in its valley region.

[0061] S8. Based on the prepared bubble nucleation layer 2, the bubble removal layer 1 is further prepared. The specific steps are as follows: S81. Construct a bubble 11 removal layer at the protrusion of the micro-wave texture structure 201 in the bubble nucleation layer 2: Cover the recessed area of ​​the bubble nucleation layer 2 with a mask, and use an Ir target to carry out magnetron sputtering deposition on the uncovered protrusion area.

[0062] S82, such as Figure 5 As shown, a superhydrophobic surface 202 is constructed in the depression of the micro-wave textured structure 201 of the bubble nucleation layer 2: the wavy protrusions are covered by a mask, and a superhydrophobic agent is deposited in the wavy depression to form a superhydrophobic surface 202 with a large contact angle.

[0063] The superhydrophilic agent 801, superhydrophobic agent, and other reagents used in the above process, as well as other methods such as sintering and laser processing, can be selected and carried out in accordance with common knowledge or the general understanding of those skilled in the art, without any particular restrictions.

[0064] Comparative Example 1 It uses a commercially available AL-ES-10 type PEM electrolyzer single cell (Dark Current Technology, effective area 36cm²). 2 ).

[0065] Comparative Example 2 The industrial-grade proton exchange membrane (PEM) electrolysis hydrogen production system developed by the aerospace engineering company (based on publicly available data) operates at a pressure of 3.2 MPaG.

[0066] Performance testing: To further verify the operational capability of the electrolytic cell with the structure of this application under high current density, the following method can be used for the experiment: tests can be conducted according to the ISO 22734:2019 standard.

[0067] The visualization microelectrolyte cell scheme validated in the literature "Adv. Sci. 2024, 11, 2405658" was adopted: the two end plates are titanium alloy parallel flow fields (flow channel width 0.5 mm), and the visualization window is 12 mm × 0.9 mm × 0.6 mm (effective area 0.09 cm²). 2 Deionized water was pumped at 18 mL / min using a micro-pump. -1 Continuous supply; membrane electrode uses Nafion 115, cathode Pt / C (loading 0.8 mg·cm³). -2 ), anode IrO2 (2 mg·cm -2 ).

[0068] First, apply a constant current step (1.0~10.0 A·cm). -2 Record the steady-state IV curve at 6 minutes per point, and then from 10 A·cm -2 →0A·cm -2 According to 0.01A·cm -2 Polarization curves are obtained by intermittent load reduction (3s per point); the ohmic impedance is subtracted online from the high-frequency resistance value to give the iR-free potential and Tafel slope.

[0069] Synchrotron radiation in-situ characterization was performed using Operando X-ray imaging with a pixel size of 0.325 μm and a sampling frequency of 10 Hz. The number of interface separation regions and bubble radii were statistically analyzed.

[0070] Because of the significant thermal effect under high current density during the experiment, a thermocouple and an external closed-loop temperature control system are further installed in the electrolytic cell to control the test temperature, which is maintained at 60±1℃~80±1℃ to ensure stable experimental conditions.

[0071] Test results show that the voltage, under constant current density operation, exhibits a fluctuating trend, decreasing to a stable level (low current density) or fluctuating before remaining relatively stable (high current density). At low current density, intermittent depletion of oxygen bubbles can be observed, accompanied by a complete nucleation, growth, and detachment process; at high current density, the bubble separation frequency increases, and more oxygen bubble detachment processes can be continuously observed. No significant upward trend in oxygen overpotential is observed on the exponential coordinate system, and no obvious inflection point is observed. Furthermore, tests show that the electrolytic cell employing the composite microporous layer structure of this application (all examples 1-3 meet the requirements) has a voltage of at least 10 A / cm². 2 The current density operating capability; while existing products (Comparative Examples 1 and 2) can only reach 2A / cm. 2 As can be seen, this solution brings a significant performance improvement.

[0072] This application proposes a composite microporous layer structure for efficient oxygen evolution. Through a layered improvement design of the traditional porous transport layer surface structure, it can promote the efficient nucleation, growth and detachment of dissolved oxygen generated during the oxygen evolution reaction in the preferential nucleation region 8. This avoids the problem of bubbles 11 obscuring the electrode interface 6, causing deactivation of reaction sites and slowing down the efficiency of electrochemical reaction.

[0073] This solution can effectively improve the polarization performance of proton exchange membrane electrolyzers under high electrical density conditions. Specific technical advantages are as follows: (1) The surface morphology of the composite microporous layer increases the number of active sites for the oxygen evolution reaction, enhances the electrochemical reaction efficiency at the same current density, and reduces the activation overpotential of the battery. (2) The composite microporous layer structure physically separates the electrode interface 6 where the oxygen evolution reaction occurs from the preferential nucleation region 8 of bubble 11, preventing bubble 11 from nucleating and lingering at the electrode interface 6, thus preventing deactivation of the reaction sites. It promotes the nucleation and growth of bubble 11 in the region away from the electrode interface 6, thereby mitigating the adverse effects of bubble 11 shielding the electrode and reducing the overpotential of bubble 11 shielding. (3) The layered design of the composite microporous layer can control the orderly nucleation, growth, and discharge of oxygen generated in the reaction, preventing oxygen from accumulating in the porous structure and causing blockage of the porous structure. An oxygen concentration gradient can be formed between the electrode interface 6 and the preferential nucleation region 8, promoting the diffusion of dissolved oxygen along the concentration gradient and preventing the oxygen concentration in the electrode interface 6 region from being too high, thereby reducing the oxygen concentration overpotential.

[0074] Based on the oxygen evolution reaction principle and anode-side oxygen evolution characteristics of proton exchange membrane electrolyzers, this application proposes a composite microporous layer structure with enhanced surface and high-efficiency oxygen evolution. On one hand, the enhanced surface improves catalyst utilization and reduces precious metal loading, thereby lowering the cost of industrial application of the electrolyzer. On the other hand, the high-efficiency oxygen evolution characteristics reduce overpotential during polarization, achieving higher electrolysis efficiency and improving industrial hydrogen production efficiency. Finally, in-situ experiments verify that the electrolyzer constructed in this application has the capability to operate at higher current densities (greater than 10 A / cm²). 2 Compared to the conventional PEM electrolyzer, which can only achieve 2A / cm, 2 The application level has been greatly improved, and it can better adapt to the volatility of hydrogen production from renewable energy.

[0075] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A composite microporous layer structure for oxygen evolution in an electrolytic cell, characterized in that, It includes a base layer (5), a bubble detachment layer (4), a bubble growth layer (3), a bubble nucleation layer (2), and a bubble removal layer (1) stacked in sequence. The bubble detachment layer (4) is connected to the anode side cavity (7) of the electrolytic cell, and the bubble detachment layer (4) is hydrophilic; The bubble nucleation layer (2) and the bubble growth layer (3) are provided with continuous branched pore throats (301), and the inner wall surface of the pore throats (301) is hydrophobic. The bubble nucleation layer (2) is a periodic structure, wherein: a preferential nucleation region (8) with superhydrophilicity is formed in the valley, and the bottom of the preferential nucleation region (8) is connected to the pore throat (301); The bubble removal layer (1) is disposed on the bubble nucleation layer (2) outside the preferred nucleation region (8), and the surface of the bubble nucleation layer (2) is a corrugated structure (201); the bubble removal layer (1) deposits noble metal particles (101) on the protrusions of the bubble nucleation layer (2) and forms a superhydrophobic surface (202) on the depressions of the bubble nucleation layer (2); the bubble removal layer (1) is disposed facing the electrode interface (6).

2. The composite microporous layer structure for oxygen evolution in an electrolytic cell according to claim 1, characterized in that, The pore size of the pore throat (301) increases along the gas phase flow direction, and the pore throat (301) is connected to the bubble release layer (4) by the preferential nucleation region (8).

3. The composite microporous layer structure for oxygen evolution in an electrolytic cell according to claim 1, characterized in that, The noble metal particles (101) are stacked to form a nanoporous structure, and the noble metal particles (101) are stacked in a peak-shaped structure at the protrusions on the surface of the bubble nucleation layer (2). The superhydrophobic surface (202) is formed by depositing a superhydrophobic agent, and the contact angle of the superhydrophobic surface (202) is greater than 150°.

4. The composite microporous layer structure for oxygen evolution in an electrolytic cell according to claim 1, characterized in that, The bubble nucleation layer (2) is composed of micron-sized porous titanium; The preferred nucleation region (8) consists of a micro / nano structure (802) formed in the valley of the bubble nucleation layer (2) and a superhydrophilic agent (801) coated on the surface of the micro / nano structure (802). The contact angle of the preferred nucleation region (8) is less than 30°.

5. A composite microporous layer structure for oxygen evolution in an electrolytic cell according to claim 1, characterized in that, The bubble growth layer (3) is made of porous titanium, wherein the porosity of the bubble growth layer (3) is greater than that of the bubble nucleation layer (2).

6. The composite microporous layer structure for oxygen evolution in an electrolytic cell according to claim 1, characterized in that, The base layer (5) is a titanium mesh, and the bubble release layer (4) is a millimeter-sized titanium felt.

7. A method for preparing a composite microporous layer structure for oxygen evolution in an electrolytic cell as described in any one of claims 1 to 6, characterized in that, Includes the following steps: S1: The bubble release layer (4) is stacked on the base layer (5); S2: Prepare slurries with different porosities, wherein the porosity of the bottom layer slurry is higher than that of the top layer slurry; S3: A bubble growth layer (3) is formed on the bubble release layer (4) by a casting process, and a bubble nucleation layer (2) is formed on the bubble growth layer (3) by a casting process. S4: A periodic structure is imprinted on the surface of the bubble nucleation layer (2), and then sintered; S5: The throat (301) is formed by laser processing technology. S6: Hydrophobic modification of the pore throat (301); S7: A mask is used to cover the peak of the bubble nucleation layer (2), and then a superhydrophilic agent is coated on the valley of the bubble nucleation layer (2) to form a preferential nucleation region (8). S8: The recesses of the corrugated structure (201) are covered by a mask, and noble metal particles (101) are deposited by magnetron sputtering; the protrusions of the corrugated structure (201) are covered by a mask, and a superhydrophobic surface (202) is formed by depositing a superhydrophobic agent.

8. The method for preparing a composite microporous layer structure for oxygen evolution in an electrolytic cell according to claim 7, characterized in that, The slurry is composed of precious metal particles, pore-forming agent, isopropanol and hydrophilic binder, and the slurry is ball-milled to remove air bubbles.

9. The method for preparing a composite microporous layer structure for oxygen evolution in an electrolytic cell according to claim 7, characterized in that, The sintering was carried out in an Ar atmosphere.

10. The method for preparing a composite microporous layer structure for oxygen evolution in an electrolytic cell according to claim 7, characterized in that, The aforementioned throat (301): First, infrared laser processing is used to form a large-diameter main throat with gradually increasing aperture, and then ultraviolet laser processing is used to form branch throats with gradually increasing aperture.

Images