Fuel cell membrane electrode catalyst layer, membrane electrode and preparation method and application thereof

Abstract

The invention relates to the technical field of batteries, and provides a fuel cell membrane electrode catalyst layer, a membrane electrode and a preparation method and application thereof, the fuel cell membrane electrode catalyst layer is formed by slurry, the slurry is mainly composed of a carbon-ionomer aggregate, a catalyst and a first ionomer; the carbon-ionomer aggregate is obtained by mixing a second ionomer, a carbon material and a first solvent and then removing the first solvent. The carbon-ionomer aggregate is further mixed with a catalyst and an ionomer to prepare a catalyst layer, so that a continuous proton conduction network can be constructed in the catalyst layer, and the surfaces of active nanoparticles can be prevented from being covered by the ionomer, so that the utilization rate of the catalyst and the electrochemical active area of a membrane electrode are improved; therefore, the power density of the fuel cell is improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a fuel cell membrane electrode catalytic layer, membrane electrode, its preparation method and application. Background Technology

[0002] Proton exchange membrane fuel cells (PEMFCs) are considered a promising clean energy technology for applications in new energy vehicles and distributed power generation due to their high energy conversion efficiency, low operating temperature, zero emissions, and rapid start-up. The membrane electrode assembly (MEA), as the core component of a PEMFC, directly determines the battery's power density, cost, and durability. The MEA typically consists of an anode, a cathode, and a proton exchange membrane sandwiched between them. The catalyst layers on the anode and cathode are the core sites where electrochemical reactions occur.

[0003] The working principle of PEMFC is as follows: fuel (such as hydrogen) undergoes an oxidation reaction in the anode catalyst layer, decomposing into protons and electrons; protons reach the cathode reaction site through the proton exchange membrane and the proton conduction network in the cathode catalyst layer, while electrons reach the cathode through the external circuit; in the cathode catalyst layer, protons and electrons undergo a reduction reaction with the oxidant (such as oxygen) to produce water. Therefore, the mass transfer efficiency, proton conduction capacity, catalyst utilization rate, and intrinsic activity within the catalyst layer are the three key factors affecting and limiting the performance of PEMFC.

[0004] In existing technologies, conventional methods for preparing catalyst layers typically employ a "one-step mixing method." This method mixes noble metal catalyst powders such as platinum-carbon (Pt / C) with a Nafion® ionomer solution in a solvent system, disperses the mixture using methods such as ultrasound to form a uniform catalyst slurry, and then coats the slurry onto a proton exchange membrane or gas diffusion layer. After drying, the catalyst layer is formed. This method is simple, mature, and widely used.

[0005] However, the catalyst layer prepared by the above method exhibits a "covered" structure at the microscopic level, meaning that the surface of the catalyst particles is generally coated with a layer of ionomer. This structure has the following inherent defects, leading to technical problems: (1) The proton conduction network is not ideal and the proton conduction resistance is high: Since the ionomers rely on their intrinsic dispersion and self-assembly during the slurry drying and film formation process, their distribution inside the catalyst layer is random and non-uniform. This makes the constructed proton conduction network discontinuous and inefficient, thereby increasing the resistance of protons to transport from the proton exchange membrane to the catalytic active site.

[0006] (2) High mass transfer resistance limits reaction rate: The thin layer of ionomers covering the surface of the catalyst active sites constitutes an additional diffusion barrier for the transport of reactant gases such as oxygen. The reactant gases need to dissolve and permeate through this ionomer layer before they can reach the catalyst surface to participate in the reaction, which significantly increases the mass transfer resistance. Especially at high current densities, insufficient oxygen supply will become the main bottleneck of performance.

[0007] (3) Low catalyst utilization and limited intrinsic activity: The direct coverage and physical shielding of the catalyst active sites by the ionomer prevents a large number of precious metal particles such as platinum that should participate in the reaction from contacting the reactants, resulting in a significant reduction in catalyst utilization. At the same time, the sulfonate groups in the ionomer also interact with the platinum active sites, producing a "poisoning" effect and limiting the full expression of the catalyst's intrinsic activity.

[0008] In summary, while the conventional methods for preparing catalyst layers and the resulting "covered" structures in existing technologies are simple, their inherent structural defects lead to problems such as high proton conduction resistance, high mass transfer resistance, and low catalyst utilization in the membrane electrode assembly (MEA). These problems collectively result in a high charge transfer resistance and a low electrochemical active surface area (ECSA) of the final MEA, ultimately limiting the improvement of the overall power density of the fuel cell.

[0009] Therefore, optimizing the microstructure of the catalyst layer to construct an efficient and continuous proton conduction network while maximizing the exposure of catalytic active sites and reducing mass transfer obstacles caused by ionomer coverage, thereby reducing charge transfer resistance, improving catalyst utilization and the electrochemical active area of ​​the membrane electrode, and thus increasing the power density of the fuel cell, is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0010] This invention provides a fuel cell membrane electrode catalytic layer, membrane electrode, its preparation method, and its application. By mixing an ionomer, carbon material, and a first solvent, and then removing the first solvent, a carbon-ionomer aggregate is obtained. This carbon-ionomer aggregate is further mixed with a catalyst and an ionomer to prepare a catalyst layer. A continuous proton conduction network can be constructed inside the catalyst layer. It can also prevent the surface of active nanoparticles from being covered by the ionomer, thereby improving the catalyst utilization rate and the electrochemical active area of ​​the membrane electrode, thus increasing the power density of the fuel cell.

[0011] In a first aspect, the present invention provides a fuel cell membrane electrode catalytic layer formed of a slurry, the slurry mainly consisting of carbon-ionomer aggregates, a catalyst and a first ionomer, wherein the first ionomer is tightly bonded to the catalyst particles to achieve mixing at the ten-nanometer to hundred-nanometer scale, for constructing local proton transport channels in the catalytic layer.

[0012] The carbon-ionomer aggregate is obtained by mixing a second ionomer, carbon material, and a first solvent, and then removing the first solvent. After the carbon-ionomer aggregate is mixed with the catalyst, it surrounds the catalyst aggregate. Compared with the first ionomer, its function is to construct an integral three-dimensional proton and ion transport channel in the catalyst layer.

[0013] The first ionomer and the second ionomer in this invention can be the same or different.

[0014] The role of ionomers is to construct ion transport channels around the catalyst. However, their direct contact with catalyst particles can also coat them, hindering the contact between gaseous reactants and the catalyst, leading to poisoning. Traditional electrode processes directly disperse and mix all the ionomers with the catalyst, which can exacerbate poisoning to some extent. This invention employs a carbon-ionomer aggregate route, where a portion of the ionomers is pre-mixed with carbon materials and then dried to obtain the carbon-ionomer aggregates. These aggregates are then mixed with the catalyst and another portion of the ionomers to construct a rapid proton conduction channel around the catalyst aggregates. This also reduces the probability of direct contact between the ionomers and the Pt catalyst particles, mitigating poisoning. Compared to traditional electrode structures, where the ionomers have a simple distribution within the catalyst layer and are mainly found between catalyst particles ranging from tens to hundreds of nanometers through dispersion, this invention also incorporates ionomers between catalyst aggregates ranging from hundreds of nanometers to micrometers. This creates a three-dimensional, highly efficient, and low-poisoning proton conduction network that combines local and overall distribution, significantly improving battery performance.

[0015] According to the fuel cell membrane electrode catalytic layer provided by the present invention, the first solvent is an organic solvent with a boiling point below 100°C; organic solvents with a boiling point below 100°C are more conducive to the dispersion of carbon materials and ionomers, thereby giving the obtained carbon-ionomer aggregates better uniformity; in conjunction with heating and stirring parameters, the evaporation and reflux of low-boiling-point solvents is beneficial to improving aggregation efficiency.

[0016] Preferably, the first solvent is selected from ethanol and / or isopropanol.

[0017] More preferably, the second ionomer is premixed with the first solvent, followed by the addition of carbon material to achieve uniform mixing. The mixture is then heated, stirred, and dried to remove the first solvent, yielding a carbon-ionomer aggregate. This drying step is crucial, as it enables efficient spatial mixing and fixation of the ionomer and carbon material. The carbon material binds the ionomer, preventing direct contact between the ionomer and the Pt catalyst particles during mixing, thus avoiding poisoning of this portion of the ionomer.

[0018] More preferably, the heating temperature is 85~95℃, the stirring speed is 200~500rpm, and the drying temperature is 60~80℃.

[0019] In this invention, the heating temperature is 85~95℃, for example, it can be any value or a range of values ​​among 85℃, 86℃, 87℃, 88℃, 89℃, 90℃, 91℃, 92℃, 93℃, 94℃, and 95℃.

[0020] In this invention, the stirring speed is 200~500 rpm, for example, it can be any value or a range of values ​​among 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, and 500 rpm.

[0021] In this invention, the drying temperature is 60~80℃, for example, it can be any value or a range of values ​​among 60℃, 65℃, 70℃, 75℃, and 80℃.

[0022] According to the fuel cell membrane electrode catalytic layer provided by the present invention, the carbon material is selected from one or more combinations of conductive carbon black, carbon fiber, carbon nanotubes and carbon nanowires; since fuel cell catalysts are generally platinum-carbon catalysts, and carbon materials themselves have excellent conductivity, experiments have found that using zero-dimensional / one-dimensional materials combined with a second ionomer is more conducive to constructing long-range fast proton conduction channels.

[0023] According to the fuel cell membrane electrode catalyst layer provided by the present invention, the second ionomer is selected from one or more combinations of perfluorosulfonic acid resin (PFSA), highly oxygen-permeable fluorinated ionomer and porous ionomer.

[0024] The aforementioned PFSA is the most widely used ionomer in the catalyst layer, characterized by a "perfluorocarbon backbone + sulfonic acid side chain", which combines high proton conductivity, excellent chemical stability and thermal stability.

[0025] High oxygen permeability fluorinated ionomers are based on a "fluorinated backbone" (retaining chemical stability). By adjusting the side chain structure (reducing the density of strongly polar groups and optimizing chain segment stacking), the oxygen permeability is improved, solving the problem of "high oxygen transport resistance" caused by the dense sulfonic acid groups in traditional PFSA ionomers. They are mainly used in the cathode catalyst layer of fuel cells (where oxygen needs to be transported from the gas diffusion layer to the catalytic active site).

[0026] Porous ionomers are characterized by having a micron / nano-scale porous structure (pore size typically 5~100nm) or forming a porous network by combining with a support. They can provide proton conduction channels and promote the transport of reactants / products through pores (such as the discharge of H2O in fuel cells and the release of O2 / Cl2 in electrolytic cells).

[0027] Preferably, the second ionomer is added to the reaction system as a dispersion with a solid content of 10-30%; for example, the dispersion is a proton-conducting polymer emulsion composed of a copolymer of perfluorosulfonic acid resin (PFSA) and polytetrafluoroethylene (PTFE).

[0028] According to the fuel cell membrane electrode catalytic layer provided by the present invention, the mass ratio of the second ionomer to the carbon material is 0.2 to 0.8:1; for example, it can be any value or a numerical range composed of any values ​​among 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, and 0.8:1.

[0029] Preferably, the mass ratio of the second ionomer to the first solvent is 1:300~400; for example, it can be any value or a range of values ​​from 1:300, 1:310, 1:320, 1:330, 1:340, 1:350, 1:360, 1:370, 1:380, 1:390, and 1:400. A mass ratio that is too low may result in insufficient dispersion of the second ionomer in the first solvent, leading to incomplete homogeneity of the carbon-ionomer aggregates.

[0030] According to the fuel cell membrane electrode catalytic layer provided by the present invention, the catalyst is a platinum-carbon catalyst, and the mass fraction of the carbon support in the catalyst is 30-70%; for example, it can be any value or a numerical range composed of any values ​​among 30%, 40%, 50%, 60%, and 70%.

[0031] Preferably, the mass ratio of carbon material in the carbon-ionomer aggregate to carbon support in the catalyst is 0.5 to 2:1; for example, it can be any value or a range of values ​​from 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2.0:1.

[0032] According to the fuel cell membrane electrode catalytic layer provided by the present invention, the first ionomer is selected from one or more combinations of perfluorosulfonic acid resin (PFSA), highly oxygen-permeable fluorinated ionomer and porous ionomer; Preferably, the mass ratio of the first ionomer to the carbon support in the catalyst is 0.2 to 0.6:1; for example, it can be any value or a range of values ​​from 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1.

[0033] According to the fuel cell membrane electrode catalytic layer provided by the present invention, the slurry is prepared by a second solvent and has a solid content of 1~2%; if the solid content of the ultrasonic spraying slurry is too high, the slurry cannot be uniformly atomized during the spraying process, resulting in insufficient uniformity of the subsequent catalytic layer.

[0034] Preferably, the second solvent is selected from water and / or isopropanol; more preferably, the second solvent is a mixture of isopropanol and deionized water in a mass ratio of 8 to 10:1.

[0035] Secondly, the present invention also provides a method for preparing the catalyst layer of a fuel cell membrane electrode as described above, comprising: The second ionomer, carbon material, and solvent are mixed, and then the solvent is removed to obtain carbon-ionomer aggregates; A slurry was prepared using carbon-ionomer aggregates, a catalyst, and a first ionomer as the main raw materials. The slurry forms the catalytic layer of the fuel cell membrane electrode.

[0036] More preferably, the method for preparing the catalyst layer of the fuel cell membrane electrode includes: (1) The second ionomer and the first solvent are premixed and added to a flask, then carbon material is added, heated and stirred and dried to obtain carbon-ionomer aggregates; (2) The carbon-ionomer aggregate, catalyst, first ionomer and second solvent are mixed evenly to obtain a slurry; (3) The slurry is sent to an ultrasonic nozzle and the slurry is uniformly coated on the substrate using an ultrasonic spraying process to obtain a catalyst layer.

[0037] Preferably, in the ultrasonic spraying process, the slurry flow rate is 0.2~1ml / min and the ultrasonic power is 1.5~3W.

[0038] Thirdly, the present invention also provides a fuel cell membrane electrode, comprising: a proton exchange membrane; And a catalyst layer located on one or both sides of the proton exchange membrane; The catalyst layer is selected from the fuel cell membrane electrode catalyst layer as described above or the fuel cell membrane electrode catalyst layer prepared by the preparation method described above.

[0039] Preferably, the catalyst layer is formed by coating on one or both sides of the proton exchange membrane.

[0040] Fourthly, the present invention also provides a method for preparing the fuel cell membrane electrode, comprising: (1) The second ionomer and the first solvent are premixed and added to a flask, then carbon material is added, heated and stirred and dried to obtain carbon-ionomer aggregates.

[0041] (2) The carbon-ionomer aggregate, catalyst, first ionomer and second solvent are mixed evenly to obtain a slurry; (3) The slurry is sent to an ultrasonic nozzle and the slurry is uniformly coated on the proton exchange membrane using an ultrasonic spraying method to obtain a membrane electrode.

[0042] Preferably, in the ultrasonic spraying process, the slurry flow rate is 0.2~1ml / min and the ultrasonic power is 1.5~3W.

[0043] When the slurry is uniformly coated on only one side of the proton exchange membrane, a half-side membrane electrode containing a catalytic layer is obtained.

[0044] Fifthly, the present invention also provides a fuel cell, comprising: a fuel cell membrane electrode assembly as described above.

[0045] This invention provides a fuel cell membrane electrode catalytic layer, membrane electrode, its preparation method, and its application. By mixing an ionomer, carbon material, and a first solvent, and then removing the first solvent, a carbon-ionomer aggregate is obtained. This carbon-ionomer aggregate is further mixed with a catalyst and an ionomer to prepare a catalyst layer. A continuous proton conduction network can be constructed inside the catalyst layer. It can also prevent the surface of active nanoparticles from being covered by the ionomer, thereby improving the catalyst utilization rate and the electrochemical active area of ​​the membrane electrode, thus increasing the power density of the fuel cell. Attached Figure Description

[0046] 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.

[0047] Figure 1 The results show the performance comparison test results of the membrane electrodes provided in Embodiment 1 and Comparative Example 1 of the present invention.

[0048] Figure 2 The cyclic voltammetry curves of the membrane electrodes provided in Embodiment 1 and Comparative Example 1 of the present invention are shown.

[0049] Figure 3 The impedance spectra of the membrane electrodes provided in Embodiment 1 and Comparative Example 1 of the present invention are shown. Detailed Implementation

[0050] 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.

[0051] The following is combined Figures 1-3 This invention describes a fuel cell membrane electrode catalytic layer, membrane electrode, its preparation method, and its application.

[0052] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0053] The platinum-carbon catalyst with a platinum (Pt) mass fraction of 40% was produced by Johnson Matthey HISPEC4000.

[0054] A perfluorosulfonic acid polymer dispersion with a mass content of 20 wt%: DuPont D2020Nafion solution.

[0055] The conductive carbon black is XC-72.

[0056] The carbon nanotubes are 20 nm in diameter and 5 μm in length.

[0057] The carbon nanowires are 150 nm in diameter and 1.5 μm in length.

[0058] Example 1 A method for fabricating a half-side membrane electrode for a fuel cell, comprising the following steps: (1) The second ionomer and the first solvent were premixed and added to a flask, followed by the addition of carbon material. The mixture was heated, stirred and dried to obtain carbon-ionomer aggregates. The first solvent was isopropanol, the heating temperature was 90°C, the stirring speed was 400 rpm, the stirring time was 2 h, and the drying temperature was 70°C.

[0059] The carbon material is selected from carbon nanotubes; The second ionomer is selected from perfluorosulfonic acid resin and added in the form of DuPont D2020 Nafion solution.

[0060] The mass ratio of the second ionomer to the carbon material is 0.5:1; The mass ratio of the second ionomer to the first solvent is 1:400.

[0061] (2) Mix the carbon-ionomer aggregate, catalyst, first ionomer and second solvent obtained in step (1) evenly to obtain a slurry with a solid content of 1%; The second solvent is a mixture of isopropanol and deionized water in a mass ratio of 10:1.

[0062] The catalyst is a platinum-carbon catalyst, Johnson Matthey HISPEC4000, in which the mass fraction of platinum is 40%.

[0063] The first ionomer was added with DuPont D2020 Nafion solution.

[0064] The mass ratio of the carbon support in the first ionomer to the catalyst is 0.5:1.

[0065] The mass ratio of carbon material in the carbon-ionomer aggregate to carbon support in the catalyst is 1:1.

[0066] (3) The slurry is sent to the ultrasonic nozzle and the slurry is uniformly coated on the proton exchange membrane (10cm×10cm) using the ultrasonic spraying method to obtain a half-side membrane electrode.

[0067] In the ultrasonic spraying process, the slurry flow rate is 0.2 ml / min, the ultrasonic power is 2.5 W, and the coating amount is 0.3 mg Pt / cm³. 2 .

[0068] The resulting half-side membrane electrode consists of a proton exchange membrane and a catalytic layer located on one side of the proton exchange membrane.

[0069] Example 2 It is basically the same as Example 1, except that carbon nanotubes are replaced with conductive carbon black, and the mass ratio of the second ionomer to conductive carbon black is 0.8:1.

[0070] Example 3 It is basically the same as Example 1, except that carbon nanotubes are replaced with carbon nanowires.

[0071] Example 4 It is basically the same as Example 1, except that isopropanol is replaced by ethanol.

[0072] Comparative Example 1 Following the preparation method of Example 1, no carbon nanotubes were added, and no carbon-ionomer aggregates were formed. The preparation method was basically the same as that of Example 1, except that step (1) was omitted without adding carbon nanotubes. In step (2), DuPont D2020 Nafion solution, Johnson Matthey HISPEC4000, deionized water, and isopropanol were mixed evenly to obtain a slurry; the proportions of each raw material were the same as in Example 1.

[0073] Comparative Example 2 It is basically the same as Example 1, except that: no first ionomer is added in step (2), and the total proportion of each raw material is the same as in Example 1 (i.e. all ionomers are added in step (1)).

[0074] Comparative Example 3 It is basically the same as Example 1, except that: after stirring in step (1), the mixture is not dried, and the resulting mixture is mixed evenly with the catalyst, the first ionomer and the second solvent in step (2).

[0075] Test case Commercial catalyst layers were stacked onto the half-side membrane electrodes obtained in the examples and comparative examples to obtain membrane electrodes. The electrochemical performance of the membrane electrodes was tested using a fuel cell testing system.

[0076] Polarization test: Battery temperature 75℃, anode H2, purity 99.999%, relative humidity 100%, cathode compressed air, relative humidity 100%.

[0077] Electrochemical active area test: battery temperature 75℃, anode H2, purity 99.999%, relative humidity 100%, cathode N2, purity 99.999%, relative humidity 100%.

[0078] The test results are as follows Figures 1-3 As shown in the table below: Table 1

[0079] like Figure 1 The figure shows a performance comparison curve of the membrane electrodes corresponding to the half-side membrane electrodes of Example 1 and Comparative Example 1 under hydrogen air conditions. Figure 1 As can be seen, in the hydrogen-air fuel cell test, the open-circuit voltage of Example 1 was 0.962V, while that of Example 1 was 0.931V. The higher open-circuit voltage indicates that the intrinsic electrochemical activity of the catalyst was more fully expressed. The membrane electrode of Example 1 showed a higher power density than that of Example 1, which further confirmed the improvement in catalyst utilization.

[0080] like Figure 2 The figures shown are cyclic voltammetry curves of the membrane electrodes corresponding to the half-side membrane electrodes of Example 1 and Comparative Example 1 under hydrogen and nitrogen conditions. Figure 2 The electrochemical active area can be calculated, corresponding to 64m² in Example 1. 2 / g Pt (the catalyst's electrochemical active area measured in the half-cell was 66 m²) 2 / g Pt), corresponding to an electrochemically active area of ​​56 m² in ratio 1. 2 The higher electrochemical active area value ( / g Pt) indicates that the membrane electrode based on carbon-ionomer aggregates has higher catalyst utilization. The catalyst electrochemical active area value measured close to that of a half-cell also reflects that the membrane electrode based on carbon-ionomer aggregates almost fully expresses the intrinsic activity of the catalyst.

[0081] like Figure 3 The image shows the impedance spectra of the membrane electrodes corresponding to the half-side membrane electrodes of Example 1 and Comparative Example 1. From... Figure 3 It can be observed that the charge transfer resistance of Example 1 is 4.282 mΩ, while that of Example 1 is 5.188 mΩ. The only difference between the two membrane electrodes lies in the structure of the catalyst layer on one side. This indicates that the carbon-ionomer aggregates construct a continuous framework network for proton conduction, which significantly reduces the charge transfer resistance of the catalyst layer due to the improved continuity of the proton conduction channels, thereby improving the overall performance of the membrane electrode. This is consistent with... Figure 1 The test results corroborate each other.

[0082] Similarly, in Comparative Examples 2 and 3, although carbon nanotubes were also added as conductive additives, their overall performance was lower than that of the embodiments of the present invention because they were not mixed and fixed with some ionomers in advance by pre-mixing and drying (Comparative Example 3), or the carbon nanotubes were not mixed with other ionomers after being fixed with some ionomers to form a local and overall conductive network (Comparative Example 2).

[0083] In summary, this invention solves the low performance problem caused by high proton conduction resistance due to the discontinuous ionomer network inside the catalyst layer of conventional fuel cell membrane electrode assemblies, which is highly dependent on the intrinsic dispersion of the catalyst slurry. The membrane electrode constructed by this invention features a complete and continuous proton conduction network formed by carbon-ionomer aggregates inside the catalyst layer. This significantly reduces the proton conduction resistance of the catalyst layer due to the improved continuity of the proton conduction channels, thereby enhancing the overall performance of the membrane electrode.

[0084] This invention solves the problems of low catalyst utilization and incomplete intrinsic activity expression caused by the covered structure of conventional fuel cell membrane electrode catalytic layers. In the non-covered membrane electrode catalytic layer constructed in this invention, the oxygen transport channels and proton conduction networks are independent of each other, avoiding the phenomena of low electrochemical active area, high local oxygen transport resistance, and poisoning of active sites by sulfonic acid groups caused by the covering of active nanoparticles with ionomers. The electrochemical active area test results completely reproduce the half-cell test results, and the catalyst utilization rate reaches more than 1.2 times that of conventional membrane electrode catalytic layers.

[0085] 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 catalyst layer for a fuel cell membrane electrode assembly, formed from a slurry, characterized in that, The slurry is mainly composed of carbon-ionomer aggregates, a catalyst, and a first ionomer; The carbon-ionomer aggregate is obtained by mixing a second ionomer, a carbon material, and a first solvent, and then removing the first solvent.

2. The fuel cell membrane electrode catalytic layer according to claim 1, characterized in that, The first solvent is an organic solvent with a boiling point below 100°C; preferably, the first solvent is selected from ethanol and / or isopropanol.

3. The fuel cell membrane electrode catalytic layer according to claim 1 or 2, characterized in that, The carbon material is selected from one or more of conductive carbon black, carbon fiber, carbon nanotubes, and carbon nanowires.

4. The fuel cell membrane electrode catalytic layer according to any one of claims 1 to 3, characterized in that, The second ionomer is selected from one or more combinations of perfluorosulfonic acid resin, highly oxygen-permeable fluorinated ionomer, and porous ionomer.

5. The fuel cell membrane electrode catalytic layer according to any one of claims 1 to 4, characterized in that, The mass ratio of the second ionomer to the carbon material is 0.2~0.8:1; And / or, the mass ratio of the second ionomer to the first solvent is 1:300~400.

6. The fuel cell membrane electrode catalytic layer according to any one of claims 1 to 5, characterized in that, The catalyst is a platinum-carbon catalyst, and the mass fraction of the carbon support in the catalyst is 30-70%. Preferably, the mass ratio of carbon material in the carbon-ionomer aggregate to carbon support in the catalyst is 0.5 to 2:

1.

7. The fuel cell membrane electrode catalytic layer according to any one of claims 1 to 6, characterized in that, The first ionomer is selected from one or more combinations of perfluorosulfonic acid resin, highly oxygen-permeable fluorinated ionomer, and porous ionomer; Preferably, the mass ratio of the first ionomer to the carbon support in the catalyst is 0.2~0.6:

1.

8. A method for preparing the catalyst layer of a fuel cell membrane electrode according to any one of claims 1 to 7, characterized in that, include: The second ionomer, carbon material, and solvent are mixed, and then the solvent is removed to obtain carbon-ionomer aggregates; A slurry was prepared using carbon-ionomer aggregates, a catalyst, and a first ionomer as the main raw materials. The slurry forms the catalytic layer of the fuel cell membrane electrode.

9. A membrane electrode assembly for a fuel cell, characterized in that, include: Proton exchange membrane; And a catalyst layer located on one or both sides of the proton exchange membrane; The catalyst layer is selected from the fuel cell membrane electrode catalyst layer according to any one of claims 1 to 7 or the fuel cell membrane electrode catalyst layer prepared by the preparation method according to claim 8.

10. A fuel cell, characterized in that, include: The fuel cell membrane electrode according to claim 9.

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