Catalytic layer and microporous layer integration method and application thereof

Abstract

The invention provides an integration method of a catalyst layer and a microporous layer and application thereof, and relates to the technical field of energy and cleaning, the integration method of the catalyst layer and the microporous layer comprises the following steps: carrying out heat transfer printing on the microporous layer to the catalyst layer; the microporous layer is a porous structure layer formed by anisotropic arrangement of nanofibers, the nanofibers are of a core-shell structure, a core material is a polymer obtained through a cross-linking esterification reaction of polyacrylic acid and polyvinyl alcohol, and a shell material comprises a conductive material and perfluorinated sulfonic acid resin; and the catalyst layer comprises perfluorinated sulfonic acid resin accounting for 10-40 wt% of the catalyst layer. According to the integration method of the catalyst layer and the microporous layer, the interface contact between the microporous layer and the catalyst layer can be enhanced, and the effects of increasing the effective electrochemical active area of the catalyst layer and relieving water logging of the catalyst layer are achieved.

Description

Technical Field

[0001] This invention relates to the fields of energy and clean technology, and in particular to an integrated method for combining a catalytic layer and a microporous layer and its application. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) have a promising future in transportation, power generation, and other applications due to their high energy conversion efficiency, rapid low-temperature start-up, and zero carbon emissions. The microporous layer, in direct contact with the catalyst layer, plays a crucial role in efficiently transporting reactant gases to the catalyst layer, enhancing electron conduction to the catalyst layer, and optimizing water management within the catalyst layer. Therefore, the interfacial contact between the microporous layer and the catalyst layer is critical to the performance output of the PEMFC.

[0003] Traditional microporous layers are typically prepared by coating a slurry containing carbon powder and hydrophobic binders onto a carbon paper substrate. This process allows the slurry to penetrate into the substrate, affecting not only the substrate's pore structure and reducing its water vapor transport efficiency, thus impacting battery performance, but also resulting in an uneven surface with depressions that hinder interfacial contact with the catalyst layer. Furthermore, the poor dispersibility of traditional microporous layer slurries inevitably leads to cracking during drying, further deteriorating the interfacial contact between the microporous layer and the catalyst layer, worsening the microporous layer's water management capabilities, and increasing interfacial contact resistance.

[0004] To address the aforementioned issues, some technologies have disclosed modifications to the structure of the microporous layer and the battery composition to resolve problems with the interface contact between the traditional microporous layer and the catalyst layer. For example, patent CN116314905A discloses an independent microporous layer for fuel cells, composed of carbon nanotubes and a hydrophobic treatment agent, providing a supporting structure that allows it to exist independently of the substrate layer. However, relying solely on carbon nanotubes for support leads to a decrease in the mechanical strength of the microporous layer. Direct stacking and assembly of the microporous layer in the battery makes it difficult to maintain the microporous layer structure without damage while simultaneously ensuring good interface contact between the microporous layer and the catalyst layer. Patent CN117174918A discloses a flexible self-supporting microporous layer and its preparation method. Using a mixed solution of a carbon precursor polymer and a Ti precursor as the spinning solution, a nanofiber membrane is obtained through electrospinning, followed by pre-oxidation and carbonization to obtain a TiN-doped flexible self-supporting microporous layer. The microporous layer reduces brittleness and enhances mechanical properties; however, the presence of metal elements within it can lead to ion degradation during battery use due to metal oxidation. Furthermore, when the microporous layer is bonded to carbon paper to form a gas diffusion layer for battery use, ensuring good interfacial contact with the catalyst layer is difficult. Summary of the Invention

[0005] This invention provides an integrated method for a catalyst layer and a microporous layer and its application, which solves the defect of poor interfacial contact between the microporous layer and the catalyst layer in the prior art, so as to enhance the adhesion between the microporous layer and the catalyst layer.

[0006] This invention provides a method for integrating a catalyst layer and a microporous layer, wherein the microporous layer is thermally transferred onto the catalyst layer; The microporous layer is a porous structure layer formed by anisotropic arrangement of nanofibers. The nanofibers have a core-shell structure. The core material is a polymer obtained by cross-linking and esterification reaction of polyacrylic acid and polyvinyl alcohol. The shell material includes conductive materials and perfluorosulfonic acid resin (Nafion). The catalyst layer comprises 10wt% to 40wt% of perfluorosulfonic acid resin.

[0007] The method for integrating a catalyst layer and a microporous layer provided by the present invention integrates a catalyst layer with a microporous layer with a specific composition and structure together by thermal transfer. This enhances the interfacial contact between the microporous layer and the catalyst layer, avoids water accumulation in the cracked and recessed areas of the traditional microporous layer, increases the effective electrochemical active area of ​​the catalyst layer, and alleviates the flooding of the catalyst layer. It also reduces the contact resistance between the microporous layer and the catalyst layer.

[0008] The method for integrating the catalyst layer and microporous layer provided by this invention features an independent microporous layer of nanofibers with a core-shell structure. This not only provides good mechanical strength and flexibility but also facilitates thermal transfer by fusing Nafions in the outer shell of the microporous nanofibers with Nafions in the catalyst layer, thereby enhancing the bonding force between the microporous layer and the catalyst layer and preventing water accumulation in the interfacial gaps. If the outer shell cannot achieve good polymer coating, the exposed polymer nanofibers cannot fuse with the Nafions in the catalyst layer, and the integration of the catalyst layer and microporous layer cannot be achieved. Furthermore, the exposed polymer nanofibers are non-conductive, and direct contact with the catalyst layer not only increases the contact resistance but also reduces the electrochemically active area due to the inability to construct a three-phase interface.

[0009] In the integrated method of catalyst layer and microporous layer provided in this scheme, by controlling the mass ratio of perfluorosulfonic acid resin in catalyst layer to 10wt%~40wt%, on the one hand, it ensures that there is enough perfluorosulfonic acid resin to facilitate proton transport in catalyst layer, while also achieving good fusion and bonding with microporous layer; on the other hand, it avoids excessive perfluorosulfonic acid resin from hindering gas diffusion and increasing the resistance to the transport of reactant gas to the three-phase interface, thus ensuring good electrochemical reaction and good electrochemical activity.

[0010] In the integrated method of the catalyst layer and microporous layer provided by this invention, the nanofibers of the microporous layer have a core-shell structure, that is, a shell formed by conductive material and perfluorosulfonic acid resin encapsulates a nanofiber skeleton (core) formed by a polymer obtained by cross-linking and esterification reaction of polyacrylic acid and polyvinyl alcohol. This structure, by relying on the characteristic of the conductive material in the outer shell to conduct electrons, achieves the effect of reducing the amount of conductive material used in a microporous layer of the same volume while ensuring the same good conductivity. Furthermore, it overcomes the problem of requiring high-temperature carbonization treatment for electron conduction in traditional electrospinning preparation of microporous layers, resulting in significantly reduced preparation costs, shorter preparation time, and an environmentally friendly preparation process. In addition, the cross-linked core polymer in this structure provides good mechanical strength and flexibility to the independent microporous layer of nanofibers, maintaining the independent microporous layer structure and enhancing the adhesion between the microporous layer and the catalyst layer, thereby reducing the contact resistance between the microporous layer and the catalyst layer and increasing the effective electrochemical active area of ​​the catalyst layer.

[0011] In the method for integrating the catalytic layer and the microporous layer provided by the present invention, the microporous layer is composed of stacked nanofibers with a core-shell structure, which enhances the bonding force between the stacked nanofibers in the microporous layer, thereby enhancing the interlayer bonding force of the microporous layer, avoiding delamination and breakage during use, and thus improving durability.

[0012] Preferably, the catalyst layer comprises 15wt% to 25wt% of perfluorosulfonic acid resin.

[0013] This scheme controls the mass ratio of perfluorosulfonic acid resin in the catalyst layer to be 15wt%~25wt%. On the one hand, it ensures that there is enough perfluorosulfonic acid resin to further facilitate the transport of protons in the catalyst layer, while also achieving better integration and bonding with the microporous layer. On the other hand, it avoids excessive perfluorosulfonic acid resin from hindering gas diffusion and increasing the resistance to the transport of reactant gas to the three-phase interface, thus ensuring a better electrochemical reaction and better electrochemical activity.

[0014] Preferably, the catalyst layer further comprises a catalyst Pt and a carbon support, wherein the mass of the catalyst Pt accounts for 20% to 60% of the total mass of the catalyst Pt and the carbon support, preferably 30% to 50%. Preferably, the Pt loading in the catalyst layer is 0.05~1 mg cm⁻¹. -2 Preferably, the concentration is 0.1~0.6 mg cm. -2 .

[0015] Preferably, the temperature of the heat transfer is 120℃~150℃, and more preferably 130~150℃.

[0016] The method for integrating the catalyst layer and microporous layer provided in this solution utilizes thermal transfer to achieve the integrated preparation of the microporous layer and catalyst layer. Based on the specific composition of the catalyst layer and the specific composition and structure of the microporous layer used in this invention, the thermal transfer temperature is controlled at 120℃~150℃. This ensures that the temperature is high enough to achieve good melting of the perfluorosulfonic acid resin in the catalyst layer and the perfluorosulfonic acid resin in the microporous shell, thus achieving good fusion and bonding between the two. At the same time, it avoids excessively high temperatures that would increase the fluidity of the perfluorosulfonic acid resin and worsen its distribution uniformity. Furthermore, the specific composition of the catalyst layer, the specific composition and structure of the microporous layer, and the thermal transfer (thermal transfer temperature 120℃~150℃) are interdependent and closely linked, and their synergistic effect enhances the bonding force between the catalyst layer and the microporous layer.

[0017] Preferably, the heat transfer pressure is 0.05 MPa to 0.5 MPa, and / or the heat transfer time is 30 s to 300 s; More preferably, the heat transfer pressure is 0.1 MPa to 0.3 MPa, and / or the heat transfer time is 60 s to 120 s.

[0018] This scheme controls the heat transfer pressure to be 0.05 MPa to 0.5 MPa. Within this pressure range, it can ensure that there is sufficient pressure to achieve good fusion and bonding of the molten perfluorosulfonic acid resin in the catalyst layer and the microporous shell layer, while avoiding excessive pressure that could cause the three-dimensional channels of the microporous layer to collapse and the pore structure of the microporous layer to be destroyed, thereby reducing the water vapor transmission efficiency and thus reducing the performance of the integrated catalyst layer / microporous layer.

[0019] This scheme controls the heat transfer time to 30 s to 300 s. Within this time range, it can ensure that there is enough time for the perfluorosulfonic acid resin in the catalyst layer and the microporous shell layer to achieve a good melt state transition, while avoiding the problem of poor uniformity of perfluorosulfonic acid resin distribution in the catalyst layer due to excessive time.

[0020] Preferably, the perfluorosulfonic acid resin accounts for 5% to 15% of the mass of the microporous layer; more preferably 7% to 12%.

[0021] In the integrated method of catalyst layer and microporous layer provided in this scheme, by controlling the mass ratio of perfluorosulfonic acid resin in catalyst layer to 10wt%~40wt% and the mass ratio of perfluorosulfonic acid resin in microporous shell material to 11%~17%, the two work synergistically to achieve better fusion and bonding with catalyst layer, and further avoid excessive perfluorosulfonic acid resin from hindering gas diffusion and reducing electrochemical activity, thus ensuring good electrochemical activity.

[0022] Preferably, the diameter of the nanofibers is 100 nm to 1000 nm, and / or the porosity of the microporous layer is 60% to 80%, and / or the average pore size of the microporous layer is 100 nm to 1000 nm.

[0023] More preferably, the thickness of the microporous layer is 3 μm to 30 μm.

[0024] More preferably, the hydrophobic angle of the microporous layer is 120°~160°.

[0025] Preferably, the method for preparing the microporous layer includes the following steps: S1. Dissolve the spinning polymer in a first solvent to obtain a spinning polymer solution, wherein the spinning polymer is polyacrylic acid and polyvinyl alcohol; S2. Disperse the conductive material and perfluorosulfonic acid resin in a second solvent, then add the spinning polymer solution, homogenize, and obtain a microporous layer spinning slurry; S3. Electrospin the microporous layer spinning slurry to obtain a microporous layer precursor; S4. The microporous layer precursor is heat-treated to cause cross-linking and esterification of polyacrylic acid and polyvinyl alcohol, and then pressed to obtain the microporous layer.

[0026] In the integrated method of catalyst layer and microporous layer provided in this scheme, the microporous layer is prepared by electrospinning. The anisotropic and disordered macroporous fiber structure generated by the random stacking of nanofibers can increase the pore size of the microporous layer, thereby improving the water vapor transport capacity of the microporous layer, reducing the water breakthrough pressure, thereby reducing the water saturation in the catalyst layer, and increasing the oxygen concentration in the catalyst layer.

[0027] Preferably, the molecular weight of the polyacrylic acid is 85,000 to 230,000, and the molecular weight of the polyvinyl alcohol is 130,000 to 1250,000.

[0028] Preferably, in S1, the mass ratio of polyacrylic acid to polyvinyl alcohol is (1~2):(1~2).

[0029] Preferably, in step S1, the concentration of the spinning polymer in the spinning polymer solution is 2 wt% to 20 wt%, more preferably 4 wt% to 12 wt%.

[0030] This method controls the concentration of the spinning polymer in the spinning polymer solution to be 2 wt%~20 wt%. This ensures the required viscosity of the spinning polymer solution, guaranteeing successful and continuous spinning without fiber beading, while also preventing excessively high viscosity of the spinning polymer solution from causing highly uneven distribution of nanofiber diameter.

[0031] Preferably, the mass of the conductive material is a, the mass of the hydrophobic agent is b, and the mass of the spinning polymer is c. a / (a+b+c) = 50%~80%, And / or, b:c=1:(2~6), preferably b:c=1:(2.5~4).

[0032] In the microporous layer preparation method provided in this scheme, the mass of conductive material is controlled to account for 50% to 80% of the total mass of conductive material, hydrophobic agent, and spinning polymer, thereby controlling the composition, structure, and properties of nanofibers in the microporous layer. When the mass proportion of conductive material is less than 50%, a uniform carbon-coated spinning polymer nanofiber skeleton structure cannot be formed; when the mass proportion of conductive material is greater than 80%, the diameter and strength of the polymer nanofiber skeleton are significantly reduced, making it unsuitable for application.

[0033] In this scheme, the conductive material accounts for more than 50% of the mass. Combined with homogeneity, it can enhance the dispersibility of the conductive material in the viscous polymer solution, thereby enhancing the uniformity of carbon-coated spun polymer nanofibers.

[0034] Preferably, in step S2, the conductive material is selected from at least one of XC-72 carbon black, acetylene black, conductive carbon black SuperP, carbon nanofibers, graphene, carbon nanotubes, and high surface area graphite.

[0035] Preferably, the first solvent and the second solvent are each independently selected from one or more of water, isopropanol, n-propanol, propanol, and ethanol.

[0036] Preferably, in S2, the homogenization method is selected from at least one of high-shear homogenization, high-pressure homogenization, microfluidic homogenization, and ball milling homogenization.

[0037] Further preferably, the rotational speed for high shear homogenization is 5000-50000 rpm, more preferably 8000-30000 rpm.

[0038] Furthermore, preferably, the pressure of the high-pressure homogenization is 400~600 bar.

[0039] Preferably, in step S3, the environmental conditions for electrospinning are: temperature 20℃-40℃, relative humidity greater than 50%RH.

[0040] This solution uses a low-boiling-point (boiling point ≤ 100℃) solvent in the microporous layer spinning slurry. The relative humidity in the electrospinning environment is greater than 50%RH, which can suppress the evaporation rate of the solvent during the spinning process and reduce the jet solidification rate, thus achieving smooth and continuous spinning without clogging the spinning needle.

[0041] Preferably, in S3, the electrospinning conditions are as follows: the microporous layer spinning slurry feed rate is 0.2 mL / h to 1.0 mL / h, and / or the voltage is 6.0 kV to 22.0 kV, and / or the rotational speed of the drum receiver is 100 rpm / min to 1000 rpm / min, and / or the needle diameter is 10G to 26G, and / or the distance between the needle and the receiver is 8 cm to 18 cm.

[0042] Preferably, in step S4, the temperature of the heat treatment is 120°C to 150°C, more preferably 130°C to 140°C.

[0043] The microporous layer preparation method provided in this scheme uses two spinning polymers, polyacrylic acid (PAA) and polyvinyl alcohol (PVA), as raw materials, and allows them to undergo a cross-linking esterification reaction during heat treatment at a temperature of 120℃~150℃. Through the cross-linking esterification reaction between the two polymers, the stability of the polymer nanofiber skeleton is enhanced, resulting in a significant extension of the service life and durability of the microporous layer.

[0044] Preferably, in step S4, the pressing pressure is 0.2 MPa to 2 MPa, and more preferably 0.8 to 1.5 MPa.

[0045] This invention provides an integrated catalytic layer / microporous layer prepared by an integrated method for combining the catalytic layer and the microporous layer.

[0046] The integrated catalyst layer / microporous layer prepared by the integrated method of catalyst layer and microporous layer provided by the present invention integrates the two components together, so that the microporous layer is separated from the substrate layer, which facilitates the recycling of waste membrane electrodes, improves the recyclability and sustainability of the substrate layer, and improves the cycle life of battery materials.

[0047] This invention provides an electrochemical device, the electrochemical device including the integrated catalytic layer / microporous layer; More preferably, the electrochemical device includes a fuel cell, a water electrolyzer, and a carbon dioxide electrolyzer. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0049] Figure 1 This is a schematic diagram of the integrated catalyst layer / microporous layer obtained by the method of integrating the catalyst layer and microporous layer of the present invention.

[0050] Figure 2 This is a scanning electron microscope (SEM) image of the nanofiber microporous layer in Example 1 of the present invention.

[0051] Figure 3 This is a SEM image of the nanofiber microporous layer in Comparative Example 2 of the present invention.

[0052] Figure 4 This is a SEM image of the nanofiber microporous layer in Comparative Example 3 of the present invention.

[0053] Figure 5 This is a physical image of the integration of nanofiber microporous layer and CCM (catalyst coating film) in Example 1 of the present invention.

[0054] Figure 6 This is a SEM image of one side of the microporous layer in the conventional gas diffusion layer in Comparative Example 1 of the present invention.

[0055] Figure 7 This is a cross-sectional SEM image of the conventional gas diffusion layer in Comparative Example 1 of the present invention.

[0056] Figure 8 This is a comparison chart of the battery polarization curves and power density curves of Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 1 of the present invention.

[0057] Figure 9 These are battery polarization curves for Examples 4 and 5 of the present invention.

[0058] Figure 10 These are battery polarization curves from Examples 2-5 of the present invention. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0060] Example 1 The preparation method of the microporous layer in this embodiment specifically includes the following steps: S1. Polyvinyl alcohol (PVA, molecular weight 450,000 g / mol) -1 ) and polyacrylic acid (PAA, molecular weight 195000 g mol) -1 The spinning polymer was added to deionized water and stirred to prepare 5 wt% polyvinyl alcohol solution and 5 wt% polyacrylic acid solution respectively. The polyvinyl alcohol solution and polyacrylic acid solution were then mixed at a mass ratio of 1:1 to obtain the spinning polymer solution.

[0061] S2. XC-72 carbon black conductive material and Nafion solution (concentration of 5wt%) hydrophobic agent are ultrasonically dispersed in isopropanol, and then a spinning polymer solution is added. The microporous layer spinning slurry is prepared by high-shear homogenization stirring (speed of 12000rpm) using a high-shear homogenizer.

[0062] S3. Electrospinning technology is used to spin the microporous layer spinning slurry. The environmental parameters for electrospinning are: temperature 27℃, relative humidity 65%RH; the spinning parameters are: microporous layer slurry feed rate 0.3mL / h, voltage 8.0kV, drum receiver rotation speed 150 rpm / min, needle diameter 20G, and distance between needle and receiver 15cm, to obtain the microporous layer precursor.

[0063] S4. The microporous layer precursor was heat-treated at 140°C for 1 hour, and then pressed at 1.2 MPa at ambient temperature to obtain a 7 μm thick nanofiber independent microporous layer. In this embodiment, the mass ratio of the conductive material (XC-72 carbon black), hydrophobic agent (Nafion), and spinning polymer (polyvinyl alcohol and polyacrylic acid) used in the nanofiber independent microporous layer was 7:1:3. In the prepared nanofiber independent microporous layer, the mass of perfluorosulfonic acid resin (Nafion) accounted for 9.1% of the mass of the nanofiber independent microporous layer.

[0064] The integration method of the catalyst layer and the microporous layer in this embodiment specifically includes the following steps: Integration of the catalyst coating membrane and the microporous layer: The nanofiber-based independent microporous layer prepared in this embodiment is placed on an aluminum foil. Then, a catalyst coating membrane (composed of a proton exchange membrane and a catalyst layer, the catalyst layer comprising perfluorosulfonic acid resin (Nafion), catalyst Pt, and a carbon support, wherein the mass of perfluorosulfonic acid resin (Nafion) accounts for 25% of the catalyst layer mass, and the mass of catalyst Pt accounts for 40% of the total mass of catalyst Pt and carbon support, with a Pt loading of 0.4 mg / cm³) is formed in the catalyst layer. -2 The cathode side of the catalyst coating membrane (CCM) is placed directly opposite the microporous layer. Then, an aluminum foil layer is placed on the CCM, sandwiched between two steel plates, and placed in a hot press at a temperature of 140°C, a pressure of 0.1 MPa, and a time of 90 seconds. This process thermally transfers the nanofiber-independent microporous layer prepared in this embodiment onto the catalyst layer of the CCM, thus preparing an integrated catalyst coating membrane / microporous layer (integrated CCM / microporous layer). The structure of this integrated CCM / microporous layer is as follows: Figure 1 As shown.

[0065] This embodiment provides a fuel cell, and the specific preparation method is as follows: The integrated CCM / microporous layer prepared in this embodiment was assembled with hydrophobically treated Toray TGP-H-060 carbon paper (the carbon paper was immersed in a 3wt% polytetrafluoroethylene (PTFE) dispersion, dried, and heat-treated in an oven at 360°C for 1 hour) to obtain a fuel cell membrane electrode assembly. This membrane electrode assembly was then assembled with a graphite bipolar plate with a flow field to obtain a fuel cell. Electrochemical performance was evaluated using a single-cell evaluation device.

[0066] Example 2 The difference between the preparation method of the microporous layer in this embodiment and that in Example 1 is that the mass ratio of the conductive material (XC-72 carbon black), hydrophobic agent (Nafion), and spinning polymer (polyvinyl alcohol and polyacrylic acid) used in the preparation of the nanofiber independent microporous layer in this embodiment is 7:0.9:3. In the prepared nanofiber independent microporous layer, the mass of perfluorosulfonic acid resin (Nafion) accounts for 8.3% of the mass of the nanofiber independent microporous layer.

[0067] The integration method of the catalyst layer and the microporous layer in this embodiment specifically includes the following steps: Integration of the catalyst coating membrane and the microporous layer: The nanofiber-based independent microporous layer prepared in this embodiment is placed on an aluminum foil. Then, a catalyst coating membrane (composed of a proton exchange membrane and a catalyst layer, the catalyst layer comprising perfluorosulfonic acid resin (Nafion), catalyst Pt, and a carbon support, wherein the mass of perfluorosulfonic acid resin (Nafion) accounts for 25% of the catalyst layer mass, and the mass of catalyst Pt accounts for 40% of the total mass of catalyst Pt and carbon support, with a Pt loading of 0.4 mg / cm³) is formed in the catalyst layer. -2 The cathode side of the catalyst coating membrane (CCM) is placed directly opposite the microporous layer. Then, an aluminum foil layer is placed on the CCM, sandwiched between two steel plates, and placed in a hot press at 150°C, 0.1 MPa, and 45 seconds. This process thermally transfers the nanofiber-independent microporous layer prepared in this embodiment onto the catalyst layer of the CCM, thus preparing an integrated catalyst coating membrane / microporous layer (integrated CCM / microporous layer). The structure of this integrated CCM / microporous layer is as follows: Figure 1 As shown.

[0068] The difference between the fuel cell fabrication method in this embodiment and that in Embodiment 1 is that the integrated CCM / microporous layer prepared in this embodiment is used.

[0069] Example 3 The difference between the preparation method of the microporous layer in this embodiment and that in Example 1 is that the mass ratio of the conductive material (XC-72 carbon black), hydrophobic agent (Nafion), and spinning polymer (polyvinyl alcohol and polyacrylic acid) used in the preparation of the nanofiber independent microporous layer in this embodiment is 7:1.25:3. In the prepared nanofiber independent microporous layer, the mass of perfluorosulfonic acid resin (Nafion) accounts for 11.1% of the mass of the nanofiber independent microporous layer.

[0070] The integration method of the catalyst layer and the microporous layer in this embodiment specifically includes the following steps: Integration of the catalyst coating membrane and the microporous layer: The nanofiber-based independent microporous layer prepared in this embodiment is placed on an aluminum foil. Then, a catalyst coating membrane (composed of a proton exchange membrane and a catalyst layer, the catalyst layer comprising perfluorosulfonic acid resin (Nafion), catalyst Pt, and a carbon support, wherein the mass of perfluorosulfonic acid resin (Nafion) accounts for 25% of the catalyst layer mass, and the mass of catalyst Pt accounts for 40% of the total mass of catalyst Pt and carbon support, with a Pt loading of 0.4 mg / cm³) is formed in the catalyst layer. -2The cathode side of the catalyst coating membrane (CCM) is placed directly opposite the microporous layer. Then, an aluminum foil layer is placed on the CCM, sandwiched between two steel plates, and placed in a hot press at 120°C, 0.1 MPa, and 90 s. This process thermally transfers the nanofiber-independent microporous layer prepared in this embodiment onto the catalyst layer of the CCM, thus preparing an integrated catalyst coating membrane / microporous layer (integrated CCM / microporous layer). The structure of this integrated CCM / microporous layer is as follows: Figure 1 As shown.

[0071] The difference between the fuel cell fabrication method in this embodiment and that in Embodiment 1 is that the integrated CCM / microporous layer prepared in this embodiment is used.

[0072] Example 4 The difference between the preparation method of the microporous layer in this comparative example and that in Example 1, the mass ratio of the conductive material (XC-72 carbon black), hydrophobic agent (Nafion), and spinning polymer (polyvinyl alcohol and polyacrylic acid) used in the preparation of the nanofiber independent microporous layer in this comparative example is 7:0.75:3. In the prepared nanofiber independent microporous layer, the mass of perfluorosulfonic acid resin (Nafion) accounts for 7% of the mass of the nanofiber independent microporous layer.

[0073] The difference between the integration method of the catalyst layer and the microporous layer in this comparative example and that in Example 1 is that the microporous layer prepared in this comparative example is used.

[0074] The difference between the preparation method of this comparative fuel cell and Example 1 is that the integrated CCM / microporous layer prepared in this comparative example is used.

[0075] Example 5 The difference between the preparation method of the microporous layer in this comparative example and that in Example 1, the mass ratio of the conductive material (XC-72 carbon black), hydrophobic agent (Nafion), and spinning polymer (polyvinyl alcohol and polyacrylic acid) used in the preparation of the nanofiber independent microporous layer in this comparative example is 7:3:3. In the prepared nanofiber independent microporous layer, the mass of perfluorosulfonic acid resin (Nafion) accounts for 23% of the mass of the nanofiber independent microporous layer.

[0076] The difference between the integration method of the catalyst layer and the microporous layer in this comparative example and that in Example 1 is that the microporous layer prepared in this comparative example is used.

[0077] The difference between the preparation method of this comparative fuel cell and Example 1 is that the integrated CCM / microporous layer prepared in this comparative example is used.

[0078] Comparative Example 1 This comparative example provides a fuel cell. The specific preparation method of this fuel cell differs from that of the fuel cell provided in Example 1 in that the CCM and conventional commercial gas diffusion layer are used for membrane electrode preparation, battery assembly, and electrochemical performance evaluation.

[0079] Comparative Example 2 The difference between the preparation method of the microporous layer in this comparative example and the preparation method of the microporous layer in Example 1 is that the mass proportion of conductive carbon material in the microporous layer spinning slurry is reduced. The mass ratio of conductive material (XC-72), hydrophobic agent (Nafion), and spinning polymer (polyvinyl alcohol and polyacrylic acid) used in the preparation of the nanofiber independent microporous layer in this comparative example is 12:3:10.

[0080] The difference between the integration method of the catalyst layer and microporous layer in this comparative example and the integration method of the catalyst layer and microporous layer in Example 1 is that the nanofiber independent microporous layer prepared in this comparative example is used.

[0081] This comparative example provides a fuel cell. The specific preparation method of this fuel cell differs from that of the fuel cell provided in Example 1 in that it uses the integrated CCM / microporous layer prepared in this comparative example.

[0082] Because the spun polymer fiber backbone is not completely covered by the shell formed by carbon particles and Nafion, some parts of the spun polymer fiber backbone are exposed. These exposed nanofibers cannot fuse with the Nafion in the catalyst layer, resulting in a small area of ​​unexposed backbone after thermal transfer. It is difficult to fully integrate the catalytic layer and the microporous layer.

[0083] Comparative Example 3 The difference between the preparation method of the microporous layer in this comparative example and the preparation method of the microporous layer in Example 1 is that the mass proportion of conductive carbon material in the microporous layer spinning slurry is reduced. The mass ratio of conductive material (XC-72), hydrophobic agent (Nafion), and spinning polymer (polyvinyl alcohol and polyacrylic acid) used in the preparation of the nanofiber independent microporous layer in this comparative example is 6:3:10.

[0084] The difference between the integration method of the catalyst layer and microporous layer in this comparative example and the integration method of the catalyst layer and microporous layer in Example 1 is that the nanofiber independent microporous layer prepared in this comparative example is used.

[0085] Since the spun polymer nanofiber skeleton is loaded with only a small amount of carbon particles and is almost not covered by the shell formed by carbon particles and Nafion, the spun polymer nanofiber skeleton is basically in a bare state. The bare spun polymer nanofiber skeleton cannot fuse with Nafion in the catalyst layer, and the integration of the catalyst layer and the microporous layer cannot be achieved.

[0086] This comparative example provides a fuel cell, the specific preparation method of which is as follows: The membrane electrode was fabricated, the battery was assembled, and the electrochemical performance was evaluated by directly stacking a CCM, a microporous layer, and a carbon paper substrate.

[0087] Comparative Example 4 The preparation method of the microporous layer in this comparative example is the same as that in Example 1.

[0088] The difference between this comparative method for integrating the catalyst layer and the microporous layer and Example 1 is that the catalyst layer comprises 5 wt% perfluorosulfonic acid resin by mass.

[0089] The difference between the preparation method of this comparative fuel cell and Example 1 is that the integrated CCM / microporous layer prepared in this comparative example is used.

[0090] Comparative Example 5 The preparation method of the microporous layer in this comparative example is the same as that in Example 1.

[0091] The difference between this comparative method for integrating the catalyst layer and the microporous layer and Example 1 is that the catalyst layer comprises 50 wt% perfluorosulfonic acid resin by mass.

[0092] The difference between the preparation method of this comparative fuel cell and Example 1 is that the integrated CCM / microporous layer prepared in this comparative example is used.

[0093] Test Results Figure 2 , Figure 3 and Figure 4 The images show surface SEM images of the nanofiber-independent microporous layers prepared in Examples 1, 2, and 3, respectively. As can be seen from the images, with decreasing carbon content in the microporous layer slurry, the proportion of the exposed area of ​​the spun polymer nanofiber skeleton increases, and the core-shell structure formed by the conductive carbon material and Nafion (shell) coating the spun polymer nanofiber skeleton (core) becomes less distinct. In the specific comparative examples, it becomes difficult to integrate the catalytic layer and microporous layer via thermal transfer, thus making it impossible to prepare an integrated catalytic layer / microporous layer. The well-coated microporous layer prepared in Example 1 can successfully facilitate the preparation of an integrated catalytic layer / microporous layer, as shown in the physical examples. Figure 5 As shown, the microporous layer on the aluminum foil and the CCM are successfully and completely integrated through thermal transfer.

[0094] like Figure 7 The traditional microporous layer shown is prepared by coating a microporous layer slurry onto a carbon paper substrate. This process allows the microporous layer slurry to penetrate into the carbon paper substrate, affecting the pore structure of the substrate and restricting mass transfer. Furthermore, the penetration of the microporous layer slurry also increases the surface roughness of the microporous layer, forming numerous recessed areas, such as… Figure 6 As shown. On the other hand, cracks form during the drying of the microporous layer slurry, which further increases the surface roughness, affects the interfacial contact with the catalyst layer, thereby reducing the electrochemical active area. In addition, water accumulates between the catalyst layer and the microporous layer, which in turn affects gas transport to the catalyst layer, leading to severe mass transfer polarization and reducing battery performance.

[0095] The battery performance of Example 1, Comparative Example 2, Comparative Example 3 and Comparative Example 1 is as follows: Figure 8 As shown. Example 1 exhibits the best microporous layer coverage, thus fully integrating the CCM with the microporous layer without any gaps in contact. Its battery performance is the best, followed by Comparative Example 2, while Comparative Example 3 shows slightly lower performance. This test result demonstrates that integrating the catalytic layer and the microporous layer enhances the interfacial contact between the microporous and catalytic layers, preventing water accumulation in cracked and recessed areas of traditional microporous layers, thereby improving the battery's water vapor transport efficiency and overall performance output. However, the battery performance of Comparative Example 3, particularly in the mass transfer polarization region, is still superior to that of Comparative Example 1, which uses a traditional gas diffusion layer. This indicates that using the specific microporous layer of this invention can effectively improve battery performance.

[0096] Compared to Example 1, the difference between Examples 4 and 5 lies in the different mass percentages of perfluorosulfonic acid resin in the microporous layer. The battery performance of Examples 4 and 5 is as follows: Figure 9 As shown, the limiting current density of both batteries is less than 4000 mA / cm². -2 The results indicate that the perfluorosulfonic acid resin content in the microporous layer affects battery performance, but to a limited extent. In Example 4, the perfluorosulfonic acid resin content in the microporous layer was 7%, similar to Example 1, and the battery's limiting current density was also similar to Example 1. In Example 5, the perfluorosulfonic acid resin content in the microporous layer was 23%, more than double that of Example 1. The battery's limiting current density further decreased, and the ohmic region performance deteriorated. This test result demonstrates that an increased proportion of perfluorosulfonic acid resin in the microporous layer affects the conductivity of the microporous layer, thereby causing a decline in battery performance.

[0097] The battery performance of Comparative Example 4, Comparative Example 5, Example 2, and Example 3 is as follows: Figure 10 As shown. In Comparative Example 4, the catalyst layer had the lowest proportion of perfluorosulfonic acid resin due to a lack of sufficient ion transport medium. Figure 10This indicates that its battery performance is the worst. Comparative Example 5 has the highest proportion of perfluorosulfonic acid resin in its catalyst layer; however, a high proportion of perfluorosulfonic acid resin increases the resistance to the diffusion of reactant gases to the catalyst layer surface, making mass transfer polarization of the battery highly likely to occur. Figure 10 The battery performance was shown to exhibit voltage drop even in the low current density region. In Example 2, the perfluorosulfonic acid resin in the catalyst layer was increased compared to Comparative Example 4, resulting in an increased ion transport medium, reduced proton transport resistance, and a significant improvement in battery performance. Similarly, in Example 3, compared to Comparative Example 5 with a lower proportion of perfluorosulfonic acid resin, mass transfer resistance was reduced, and mass transfer polarization was alleviated.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for integrating a catalytic layer and a microporous layer, characterized in that, The microporous layer is thermally transferred onto the catalyst layer; The microporous layer is a porous structure layer formed by anisotropic arrangement of nanofibers. The nanofibers have a core-shell structure. The core material is a polymer obtained by cross-linking and esterification reaction of polyacrylic acid and polyvinyl alcohol. The shell material includes conductive materials and perfluorosulfonic acid resin. The catalyst layer comprises 10wt% to 40wt% of perfluorosulfonic acid resin.

2. The method for integrating the catalyst layer and the microporous layer according to claim 1, characterized in that, The catalyst layer comprises 15wt% to 25wt% of perfluorosulfonic acid resin.

3. The method for integrating the catalyst layer and the microporous layer according to claim 1 or 2, characterized in that, The catalyst layer also includes a catalyst Pt and a carbon support, wherein the mass of the catalyst Pt accounts for 20% to 60% of the total mass of the catalyst Pt and the carbon support, preferably 30% to 50%. Preferably, the Pt loading in the catalyst layer is 0.05~1 mg cm⁻¹. -2 Preferably, the concentration is 0.1~0.6 mg cm. -2 .

4. The method for integrating the catalyst layer and the microporous layer according to claim 1 or 3, characterized in that, The temperature for heat transfer is 120℃~150℃, preferably 130~150℃.

5. The method for integrating the catalyst layer and the microporous layer according to claim 1 or 4, characterized in that, The heat transfer pressure is 0.05 MPa to 0.5 MPa, and / or the heat transfer time is 30 s to 300 s; Preferably, the heat transfer pressure is 0.1 MPa to 0.3 MPa, and / or the heat transfer time is 60 s to 120 s.

6. The method for integrating the catalyst layer and the microporous layer according to claim 1 or 5, characterized in that, In the microporous layer, the perfluorosulfonic acid resin accounts for 5% to 15% of the mass of the microporous layer; preferably 7% to 12%.

7. The method for integrating the catalyst layer and the microporous layer according to claim 1 or 6, characterized in that, The nanofibers have a diameter of 100 nm to 1000 nm, and / or the microporous layer has a porosity of 60% to 80%, and / or the microporous layer has an average pore size of 100 nm to 1000 nm.

8. The method for integrating the catalyst layer and the microporous layer according to claim 1 or 7, characterized in that, The method for preparing the microporous layer includes the following steps: S1. Dissolve the spinning polymer in a first solvent to obtain a spinning polymer solution, wherein the spinning polymer is polyacrylic acid and polyvinyl alcohol; S2. Disperse the conductive material and perfluorosulfonic acid resin in a second solvent, then add the spinning polymer solution, homogenize, and obtain a microporous layer spinning slurry; S3. Electrospin the microporous layer spinning slurry to obtain a microporous layer precursor; S4. The microporous layer precursor is heat-treated to cause cross-linking and esterification of polyacrylic acid and polyvinyl alcohol, and then pressed to obtain the microporous layer.

9. An integrated catalyst layer / microporous layer prepared by an integrated method for integrating a catalyst layer and a microporous layer as described in any one of claims 1 to 8.

10. An electrochemical device, characterized in that, The electrochemical device includes the integrated catalytic layer / microporous layer as described in claim 9; Preferably, the electrochemical device includes a fuel cell, a water electrolyzer, and a carbon dioxide electrolyzer.

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